WO2025206759A1 - Access method and apparatus of iot device in communication system - Google Patents

Abstract

The present invention relates to access technology of an IoT device in a communication system. The present disclosure may provide a method of a first communication node, the method comprising the steps of: receiving configuration information of a resource for random access from a second communication node; and transmitting a first identifier of the first communication node to the second communication node by utilizing the resource for the random access.

Description

Method and device for connecting IoT devices in a communication system

The present disclosure relates to a connection technology for an IoT device in a communication system, and more specifically, to a connection technology for an IoT device in a communication system that enables an IoT device to connect to a reader.

Advances in information and communication technology (ICT) can lead to the development of various wireless communication technologies. Representative wireless communication technologies include LTE (long term evolution), NR (new radio), and 6G (6th Generation), all of which are defined by the 3rd Generation Partnership Project (3GPP) standards. LTE can be one of the 4th Generation (4G) wireless communication technologies, and NR can be one of the 5th Generation (5G) wireless communication technologies.

In order to process the rapidly increasing amount of wireless data following the commercialization of 4G communication systems (e.g., communication systems supporting LTE), 5G communication systems (e.g., communication systems supporting NR) that use a higher frequency band (e.g., a frequency band higher than 6 GHz) than the frequency band of the 4G communication system (e.g., a frequency band below 6 GHz) may be considered. 5G communication systems may support enhanced Mobile Broadband (eMBB), Ultra-Reliable and Low Latency Communication (URLLC), and massive Machine Type Communication (mMTC).

Meanwhile, the Internet of Things (IoT), where numerous "things" are interconnected and operate, has recently attracted significant attention for its potential to improve industrial production efficiency and enhance the comfort of life. IoT devices can be deployed in large quantities—hundreds of billions—to accommodate diverse applications while further reducing size, complexity, and power consumption. However, IoT device management companies may find it difficult to manually replace or recharge the batteries of these IoT devices due to maintenance and management issues. Therefore, IoT technology may require new ambient IoT (AIoT) technologies to support devices without energy storage capabilities, batteries, or devices that do not require manual battery replacement or recharging.

The purpose of the present disclosure to solve the above problems is to provide a connection method and device for an IoT device to connect to a leader in a communication system.

In order to achieve the above object, a method for connecting an IoT device in a communication system according to a first embodiment of the present disclosure may include, as a method of a first communication node, a step of receiving setting information of resources for random connection from a second communication node; and a step of transmitting a first identifier of the first communication node to the second communication node by utilizing the resources for random connection.

Here, the first communication node can receive resource setting information for the random access from the second communication node through a paging message.

Here, the first communication node can transmit the first identifier or random access signal to the second communication node by utilizing the resource for random access.

Here, the configuration information of the random access resource may include at least one of configuration information of wireless resources for contention-based random access (CBRA) and contention-free based random access (CFRA), configuration information of wireless resources for access occasions, configuration information of wireless resources for responding to a random access signal, configuration information for the operation of the first communication node, information on a waiting time for receiving the response, information on a selection window for selecting the access occasions, information on a maximum number of retransmission attempts, or transmission power ramping configuration information.

Here, the first identifier may be the entire device identifier of the upper layer of the first communication node or a part of the device identifier.

Here, the first identifier may be a random value selected within the selection range of the first identifier set in the second communication node.

Here, the method may further include: receiving a first response signal for transmission of the first identifier from the second communication node; confirming the first identifier in the first response signal; and transmitting a second response signal including a second identifier to the second communication node when the first identifier is confirmed in the first response signal.

Here, the second identifier may be a device identifier of a higher layer of the first communication node.

Here, the method may further include a step of determining that reception of the first identifier has failed at the second communication node if the first response signal is not received during the waiting time for the first response signal for transmission of the first identifier from the second communication node.

Meanwhile, in a communication system according to a second embodiment of the present disclosure for achieving the above purpose, a method for connecting an IoT device may include, as a method of a second communication node, a step of transmitting setting information for random connection to a first communication node; and a step of receiving a first identifier from the first communication node based on the setting information.

Here, the method may further include a step of transmitting a first response signal including the first identifier to the first communication node; and a step of receiving a second identifier from the first communication node.

Here, the method may further include a step of receiving a service request signal from an AIoT (ambient internet of things) controller; and a step of transmitting a service response signal including the second identifier to the AIoT controller in response to the service request signal.

Here, the method may further include: transmitting a first response signal including the first identifier to the first communication node; waiting for a second response signal to the first response signal from the first communication node during a waiting time; and transmitting a signal requesting the second response signal to the first communication node if the second response signal is not received during the waiting time.

Meanwhile, in a communication system according to a third embodiment of the present disclosure for achieving the above purpose, a connection device of an IoT device includes, as a first communication node, at least one processor, wherein the at least one processor can cause the first communication node to receive setting information of resources for random access from a second communication node; and to transmit a first identifier of the first communication node to the second communication node by utilizing the resources for random access.

Here, the at least one processor can cause the first communication node to transmit the first identifier or the random access signal to the second communication node by utilizing the resources for the random access.

Here, the first identifier may be the entire device identifier of the upper layer of the first communication node or a part of the device identifier.

Here, the first identifier may be a random value selected within the selection range of the first identifier set in the second communication node.

Here, the at least one processor may further cause the first communication node to receive a first response signal from the second communication node for transmission of the first identifier; identify the first identifier in the first response signal; and, if the first identifier is identified in the first response signal, transmit a second response signal including a second identifier to the second communication node.

Here, the second identifier may be a device identifier of a higher layer of the first communication node.

Here, the at least one processor may further cause the first communication node to determine that reception of the first identifier has failed at the second communication node if the first response signal is not received during the waiting time of the first response signal for transmission of the first identifier from the second communication node.

According to the present disclosure, an IoT device can select a random access resource and transmit a random access signal to a reader. At this time, the IoT device can transmit a random access signal including a device identifier to the reader. The reader can receive the random access signal and recognize the device identifier. The reader can transmit a response signal including the recognized device identifier to the IoT device. When the IoT device receives the response signal including the transmitted device identifier, it can determine that the random access signal has been successfully received.

Figure 1 is a conceptual diagram illustrating a first embodiment of a communication system.

Figure 2 is a block diagram illustrating a first embodiment of a communication node constituting a communication system.

Figure 3 is a conceptual diagram illustrating embodiments of a base station/IoT (internet of things) device topology.

Figure 4 is a conceptual diagram illustrating embodiments of an intermediate node/IoT device topology.

Figure 5 is a conceptual diagram illustrating embodiments of user terminal/IoT device topologies.

Figure 6 is a conceptual diagram showing examples of frame structures of an AIoT (ambient internet of things) network.

Figure 7 is a conceptual diagram illustrating embodiments of a method for transmitting and receiving data between a leader and an IoT device.

Figure 8 is a conceptual diagram showing embodiments of a control frame of type 1.

Figure 9 is a conceptual diagram illustrating examples of data frames of type 1.

Figure 10 is a conceptual diagram illustrating embodiments of a type 2 R2D (reader to device) frame.

Figure 11 is a conceptual diagram showing embodiments of a D2R (device to reader) frame.

Figure 12 is a flowchart illustrating embodiments of a connection method using a four-step message exchange.

Figure 13 is a flowchart illustrating embodiments of a connection method using a four-step message exchange.

Figure 14 is a flowchart illustrating embodiments of a connection method using a two-step message exchange.

Figure 15 is a flowchart illustrating embodiments of a connection method using a two-step message exchange.

Figure 16 is a flowchart illustrating embodiments of a connection method using a three-step message exchange.

Figure 17 is a conceptual diagram illustrating embodiments of random access resource configuration based on a transmission set.

Figure 18 is a flowchart illustrating embodiments of a connection method using a one-step message exchange.

Figure 19 is a flowchart showing embodiments of an integrated random access method.

This disclosure may be subject to various modifications and various embodiments. Specific embodiments are illustrated and described in detail in the drawings. However, this is not intended to limit the disclosure to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the disclosure.

While terms such as "first" and "second" may be used to describe various components, these components should not be limited by these terms. These terms are used solely to distinguish one component from another. For example, without departing from the scope of the present disclosure, a first component could be referred to as a "second component," and similarly, a second component could also be referred to as a "first component." The term "and/or" includes a combination of multiple related items described herein or any of multiple related items described herein.

In embodiments of the present disclosure, “at least one of A and B” may mean “at least one of A or B” or “at least one of combinations of one or more of A and B.” Furthermore, in embodiments of the present disclosure, “at least one of A and B” may mean “at least one of A or B” or “at least one of combinations of one or more of A and B.”

When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components intervening. Conversely, when a component is referred to as being "directly connected" or "connected" to another component, it should be understood that there are no other components intervening.

The terminology used in this disclosure is only used to describe specific embodiments and is not intended to limit the present disclosure. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this disclosure, it should be understood that the terms "comprise" or "have" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which this disclosure pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and shall not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

Hereinafter, preferred embodiments of the present disclosure will be described in more detail with reference to the attached drawings. In order to facilitate an overall understanding in describing the present disclosure, identical reference numerals will be used for identical components in the drawings, and redundant descriptions of identical components will be omitted.

Figure 1 is a conceptual diagram illustrating a first embodiment of a communication system.

Referring to FIG. 1, a communication system (100) may include a plurality of communication nodes (110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, 130-6). Here, the communication system may be referred to as a "communication network." Each of the plurality of communication nodes may support at least one communication protocol. For example, each of the plurality of communication nodes may support a communication protocol based on CDMA (code division multiple access), a communication protocol based on WCDMA (wideband CDMA), a communication protocol based on TDMA (time division multiple access), a communication protocol based on FDMA (frequency division multiple access), a communication protocol based on OFDM (orthogonal frequency division multiplexing), a communication protocol based on OFDMA (orthogonal frequency division multiple access), a communication protocol based on SC (single carrier)-FDMA, a communication protocol based on NOMA (non-orthogonal multiple access), a communication protocol based on SDMA (space division multiple access), etc. Each of the plurality of communication nodes may have the following structure.

Figure 2 is a block diagram illustrating a first embodiment of a communication node constituting a communication system.

Referring to FIG. 2, a communication node (200) may include at least one processor (210), a memory (220), and a transceiver (230) that is connected to a network and performs communication. In addition, the communication node (200) may further include an input interface device (240), an output interface device (250), a storage device (260), etc. Each component included in the communication node (200) may be connected by a bus (270) to perform communication with each other. However, each component included in the communication node (200) may be connected through an individual interface or an individual bus centered around the processor (210), rather than a common bus (270). For example, the processor (210) may be connected to at least one of the memory (220), the transceiver (230), the input interface device (240), the output interface device (250), and the storage device (260) through a dedicated interface.

The processor (210) can execute program commands stored in at least one of the memory (220) and the storage device (260). The processor (210) may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor in which the methods according to embodiments of the present disclosure are performed. Each of the memory (220) and the storage device (260) may be configured with at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory (220) may be configured with at least one of a read-only memory (ROM) and a random access memory (RAM).

Referring again to FIG. 1, the communication system (100) may include a plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) and a plurality of user equipment (UEs) (130-1, 130-2, 130-3, 130-4, 130-5, 130-6). Each of the first base station (110-1), the second base station (110-2), and the third base station (110-3) may form a macro cell. Each of the fourth base station (120-1) and the fifth base station (120-2) may form a small cell. The fourth base station (120-1), the third UE (130-3), and the fourth UE (130-4) may be within the coverage of the first base station (110-1). The second UE (130-2), the fourth UE (130-4), and the fifth UE (130-5) may be within the coverage of the second base station (110-2). The fifth base station (120-2), the fourth UE (130-4), the fifth UE (130-5), and the sixth UE (130-6) may be within the coverage of the third base station (110-3). The first UE (130-1) may be within the coverage of the fourth base station (120-1). The sixth UE (130-6) may be within the coverage of the fifth base station (120-2).

Here, each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) may be referred to as a NodeB, an evolved NodeB, a BTS (base transceiver station), a radio base station, a radio transceiver, an access point, an access node, a road side unit (RSU), a DU (digital unit), a CDU (cloud digital unit), a RRH (radio remote head), a RU (radio unit), a TP (transmission point), a TRP (transmission and reception point), a relay node, etc. Each of the plurality of UEs (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) may be referred to as a terminal, an access terminal, a mobile terminal, a station, a subscriber station, a mobile station, a portable subscriber station, a node, a device, etc.

Each of the plurality of communication nodes (110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, 130-6) can support cellular communication (e.g., long term evolution (LTE), advanced LTE-A, 5G NR (New Radio) as defined in the 3rd generation partnership project (3GPP) standard). Each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) can operate in a different frequency band or can operate in the same frequency band. Each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) can be connected to each other via an ideal backhaul or a non-ideal backhaul, and can exchange information with each other via the ideal backhaul or the non-ideal backhaul. Each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) can be connected to a core network (not shown) via an ideal backhaul or a non-ideal backhaul. Each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) can transmit a signal received from the core network to the corresponding UE (130-1, 130-2, 130-3, 130-4, 130-5, 130-6), and can transmit a signal received from the corresponding UE (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) to the core network.

Each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) can support OFDMA-based downlink transmission and SC-FDMA-based uplink transmission. In addition, each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) can support MIMO (multiple input multiple output) transmission (e.g., single user (SU)-MIMO, multi user (MU)-MIMO, massive MIMO, etc.), CoMP (coordinated multipoint) transmission, carrier aggregation transmission, transmission in an unlicensed band, device to device (D2D) communication (or, ProSe (proximity services), etc.). Here, each of the plurality of UEs (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) can support the base station (110-1, 110-2, 110-3, 120-1, 120-2) and can perform operations supported by base stations (110-1, 110-2, 110-3, 120-1, 120-2).

The Internet of Things (IoT), where numerous "things" are interconnected and operated, has recently attracted significant attention for its potential to improve industrial production efficiency and enhance the comfort of daily life. IoT devices can be deployed in large quantities—hundreds of billions—for diverse applications while further reducing size, complexity, and power consumption. However, IoT devices can be difficult to manually replace or recharge due to maintenance and management issues. Therefore, IoT technology may require new ambient IoT (AIoT) technologies to support devices without energy storage capabilities, batteries, manual battery replacement, or recharging.

In these AIoT networks, IoT devices may have lower complexity than narrowband (NB)-IoT devices or long-term evolution machine type communication (LTE-MTC) devices. Furthermore, IoT devices in AIoT networks may not have batteries. Alternatively, IoT devices in AIoT networks may have batteries with limited capacity.

The present disclosure may propose a method for wireless connection and communication between IoT devices in an AIoT network comprised of multiple IoT devices. In particular, the present disclosure may propose a frame structure and inter-node operation procedures for wireless connection between a leader and devices in an AIoT network.

1. Network topology

AIoT networks can consider three network topologies:

1-1. Base station (BS)/Internet of Things (IoT) device topology

Figure 3 is a conceptual diagram illustrating embodiments of a base station/IoT (internet of things) device topology.

Referring to FIG. 3, in the base station/IoT device topology, an IoT device (310) can be directly connected to and communicate with a base station (320). In the base station/IoT device topology, the base station can transmit data, signals, and energy required by the IoT device to the IoT device. At this time, the base station can transmit energy to the IoT device using an RF (radio frequency) signal so that the IoT device can harvest energy. The RF signal can include data or a signal. In this topology, the base station performs the function of a reader and can include a gNB, eNB of a cellular network, or an AP (access point) of a wireless LAN network.

1-2. Immediate Node/IoT Device Topology

Figure 4 is a conceptual diagram illustrating embodiments of an intermediate node/IoT device topology.

Referring to FIG. 4, in the intermediate node/IoT device topology, an IoT device (410) can be connected to and communicate with a base station (430) through an intermediate node (420). In this topology, the base station can perform data and signal procedures of the intermediate node and the cellular network. The intermediate node can transmit data, signals, and energy required for the IoT device to the IoT device. At this time, the intermediate node can transmit energy to the IoT device using an RF signal so that the IoT device can harvest energy. The RF signal can include data or a signal. In this topology, the intermediate node performs the function of a reader and can include a relay, an integrated access and backhaul (IAB) node, a user equipment (UE) repeater, etc.

1-3. User Equipment/IoT Device Topology

Figure 5 is a conceptual diagram illustrating embodiments of user terminal/IoT device topologies.

Referring to FIG. 5, in a user equipment/IoT device topology, an IoT device (510) can be directly connected to and communicate with a user equipment (520). In this topology, the user equipment can transmit data and signals, as well as energy required by the IoT device, to the IoT device. In this case, the user equipment can transmit energy to the IoT device using an RF signal so that the IoT device can harvest energy. The RF signal can include data or a signal.

2. Device type

Devices in AIoT networks can be classified into the following types:

-Type A IoT device: Type A IoT devices may not use amplifiers when transmitting/receiving links between the IoT device and the reader. The maximum power consumption of Type A IoT devices may be greater than 0 and less than or equal to 1 μW. Link transmission from Type A IoT devices to the reader may be achieved through backscattering on an externally provided carrier wave. Type A IoT devices may not have their own energy storage.

-Type B IoT devices: Type B IoT devices may not use amplifiers during link transmission/reception between the IoT device and the reader. The maximum power consumption of Type B IoT devices may be greater than 0 and less than 1 μW. Link transmission from Type B IoT devices to the reader may be achieved through backscattering on an externally provided carrier wave. Type B IoT devices may have their own energy storage.

- Type C IoT Device: Type C IoT devices can use amplifiers during link transmission/reception between the IoT device and the reader. The maximum power consumption of Type C IoT devices can be greater than 0 and less than several hundred μW. Link transmission from Type C IoT devices to the reader can be achieved through backscattering on an externally provided carrier wave. Alternatively, link transmission from Type C IoT devices to the reader can be achieved by transmitting a signal generated by the device itself. Type C IoT devices can have their own energy storage.

3. Frame structure

Figure 6 is a conceptual diagram showing examples of frame structures of an AIoT (ambient internet of things) network.

Referring to FIG. 6, the frame structure in an AIoT network can be expressed as a frame, subframe, slot, and symbol in a resource pool composed of time and frequency resources. A frame can be composed of multiple subframes. For example, a frame can be composed of I subframes. Each subframe can be composed of multiple slots. For example, a subframe can be composed of J slots. Each slot can be composed of multiple symbols. For example, a slot can be composed of K symbols. Here, I, J, and K can be positive integers.

In an AIoT network, a reader and an IoT device can communicate with each other through a reader-to-device (R2D) frame and a device-to-reader (D2R) frame. The reader-to-device frame and the device-to-reader frame can be transmitted in units of subframes, slots, or symbols. Here, the R2D link may refer to a transmission link that transmits information from a reader to a device. The D2R link may refer to a transmission link that transmits information from a device to a reader. An R2D frame may refer to a frame transmitted over an R2D link. A D2R frame may refer to a frame transmitted over a D2R link.

Figure 7 is a conceptual diagram illustrating embodiments of a method for transmitting and receiving data between a leader and an IoT device.

Referring to FIG. 7, a leader and an IoT device can transmit and receive data using an R2D link and a D2R link. The R2D link and the D2R link can operate in time units such as subframes, slots, or symbols. In the R2D link and the D2R link, time units such as subframes, slots, or symbols can be used as transmission units of the AIoT network and can be collectively referred to as frames. Therefore, the AIoT device can perform data transmission and reception procedures by transmitting D2R frames and receiving R2D frames. In addition, the AIoT device can charge the energy required for operation through various forms of energy harvesting functions as well as the radio frequency (RF) provided by the AIoT network. A CW (carrier wave) frame can be defined to charge the energy of the AIoT device.

In an AIoT network, leaders and IoT devices can communicate in units of transmission sets, each consisting of R2D frames and D2R frames. A transmission set can consist of a variable number of R2D frames and D2R frames and can include one or more R2D frames or D2R frames. A transmission set can be used as a basic unit for wireless resource configuration and can be operated (semi-)statically or variably through wireless resource configuration of R2D frames under the control of the AIoT network.

A leader can transmit configuration information of a transmission set to IoT devices via an R2D frame. The IoT devices can receive the configuration information of the transmission set from the leader. In addition, each IoT device can perform a procedure of receiving an R2D frame and transmitting a D2R frame based on the configuration information of the received transmission set. In addition, the transmission set can be composed of a plurality of access occasions. Each access occasion can include wireless resources that an IoT device can use for random access. The access occasions can be random access occasions.

Transmission set #1 may include two R2D frames, one D2R frame, and one CW frame. An IoT device may receive R2D frames and transmit D2R frames within transmission set #1 based on the configuration and allocation control information of radio resources of the R2D frames included within transmission set #1.

Transmission set #2 may include one R2D frame and two D2R frames. The IoT device may perform R2D frame reception and D2R frame transmission within transmission set #2 based on the configuration and allocation control information of the radio resources of the R2D frame included within transmission set #2.

3-1. R2D frame structure

The leader of an AIoT network can transmit R2D frames to IoT devices periodically or aperiodically. Depending on how information for wireless resource allocation is conveyed in an AIoT network, R2D frames can be categorized into Type 1 and Type 2 R2D frames.

A Type 1 R2D frame may include a control frame that conveys configuration and allocation control information for wireless resources of a transmission set, and a data frame that transmits data from a leader to an IoT device. Thus, the control frame and data frame in a Type 1 R2D frame can operate independently. The control frame in a Type 1 R2D frame may be referred to as a Type 1 control frame. Furthermore, the data frame in a Type 1 R2D frame may be referred to as a Type 1 data frame.

Figure 8 is a conceptual diagram showing embodiments of a control frame of type 1.

Referring to FIG. 8, a control frame of type 1 may include a preamble, frame type information, frame setup information within a transmission set, random access resource setup information, scheduling information of R2D frames and D2R frames included in the transmission set, and a CRC (cyclic redundancy check) field.

Here, the preamble may be information indicating the start of an R2D frame and may be information used for frame and slot synchronization. The preamble may include a training sequence and a channel estimation sequence.

The frame type may refer to the type of R2D frame transmitted, such as a control frame or a data frame. Information about the frame configuration may include information about the number of frames included in the transmission set and the format of the frames included in the transmission set. Here, the format of the frame may refer to the format of an R2D frame, a D2R frame, or a CW frame. For example, in the frame configuration information of transmission set #1, the number of frames may be 3. In addition, information about the frame format in the frame configuration information of transmission set #1 may be expressed as a bit stream such as '00000110', assuming that the R2D frame, the D2R frame, and the CW frame are expressed as 2-bit information '00', '01', and '10', respectively.

The random access resource configuration information may be configuration information for a random access occasion resource of a D2R frame and a random access response resource of an R2D frame mapped thereto. The configuration information for the random access occasion resource and the random access response resource may include radio resource allocation information on time-frequency resources. The random access resource configuration information may be information representing the locations of the random access occasion resource and the random access response resource as a two-dimensional bitmap. The random access occasion resource may be a resource for a random access occasion. The random access response resource may be a resource for a random access response.

For example, the first D2R frame included in transmission set #1 may be composed of 14 symbols. In other words, the first D2R frame included in transmission set #1 may be composed of 14 symbols numbered 0 to 13. At this time, symbols 4 to 6 of the first D2R frame may be allocated for preamble transmission for random access. In this case, the configuration information for the time resource of the random access resource configuration information may be expressed as a bitmap of '00001110000000'. The symbol allocated for preamble transmission for random access may be a random access occasion resource.

The frequency resource configuration for the symbols allocated for preamble transmission for random access can be configured by allocating the entire frequency band in units defined in advance. Alternatively, the frequency resource configuration for the symbols allocated for preamble transmission for random access can be expressed as a bitmap corresponding to the frequency resource unit for the set symbols in the same way as the time resource configuration. For example, if six frequency resources can be allocated to symbol 4 of the D2R frame of transmission set #1, the lower three frequency resources among them can be allocated for random access. In this case, the frequency resource configuration for the symbols allocated for preamble transmission for random access can be expressed as a bit stream of '111000'.

The random access resource configuration information can be applied equally to the random access opportunity (RA opportunity) of the D2R frame and the random access response of the R2D frame. The IoT device can attempt to randomly access the leader using any one of the wireless resources selected from the resources for the random access occasions of the D2R frame. At this time, whether the random access of the IoT device to the leader is successful can be determined by the IoT device through decoding the wireless resources of the same location of the random access response of the configured R2D frame. In addition, the random access resource configuration information can include a mapping value indicating the relationship between the D2R frame to which the random access resource configuration has been applied and the R2D frame including the wireless resources of the random access response that presents the random access result. For example, the random access resource of the first D2R frame included in a specific transmission set #n can be mapped to the wireless resources of the random access response of the second R2D frame included in the transmission set. Here, n can be a positive integer.

In addition, the random access resource configuration information can provide a selection window for selecting a random access resource for an IoT device to participate in random access. Based on the information about the selection window for selecting a random access resource, the IoT device can select a random value and then transmit a random access signal to the leader from the random access occasion resource configured using the selected value. The selection window for selecting a random access resource can be arbitrarily changed by the leader considering the status of the AIoT network, collision rate, etc. The leader can transmit information about the selection window for selecting a random access resource to the IoT device as the random access resource configuration information of the D2R frame.

Additionally, the random access resource configuration information may include a waiting time for a random access response and selection window reset information for selecting a random access resource. The waiting time for a random access response may refer to the time for which an IoT device waits for a response after transmitting a random access signal, and may be a timer operation value of the IoT device or a value in units of frames.

The selection window reset information for selecting a random access resource may be information on how to expand the size of the selection window for selecting a random access resource when re-executing the random access procedure. For example, when expanding the random access interval by an exponent of 2, the IoT device can double the size of the selection window for selecting an existing random access resource. After selecting a random number from the selection window for selecting a random access resource that has been expanded twice, the IoT device can transmit a random access signal to the reader from the random access occasion resource set using the selected number.

Scheduling information may include allocation information of radio resources for transmission in each R2D frame and D2R frame included in a transmission set. The scheduling information may include allocation information of radio resources for R2D assignment and D2R grant. The allocation information of radio resources for R2D assignment and the allocation information of radio resources for D2R grant may include an IoT device identifier, radio resource allocation information indicating a position in time and frequency resources for data transmission/reception, a static scheduling flag indicating whether to allocate the same radio resources of a frame within a transmission set to a specific IoT device, and physical layer operation information including modulation and demodulation-related parameters, coding schemes, etc. for transmission.

For example, scheduling information can be expressed by mapping transmission symbols included in an R2D frame or a D2R frame to bits. For example, the second R2D frame included in transmission set #1 can be composed of 14 (0 to 13) symbols. The leader can allocate symbols 4 and 5 from the 14 symbols to IoT device A for transmission. At this time, the device identifier (device ID) of the scheduling information can be A. In the radio resource allocation information indicating a location on time resources and frequency resources for data transmission/reception of the scheduling information, the time resource allocation information can be expressed as '00001100000000' in a bitmap (bitmap for resource allocation).

In addition, frequency resource allocation information for allocation of frequency resources corresponding to allocated time resources can be expressed as a bitmap in the same form. For example, 12 frequency resources can be allocated to symbol 4 of the second R2D frame included in transmission set #1. In the radio resource allocation information indicating the location on the time resource and frequency resource for data transmission/reception of scheduling information, the frequency resource allocation information can be expressed as a bitmap of a bit stream in the form of '111111111111' when all frequency resources are allocated to IoT device A.

The leader can use established scheduling, which allocates the same radio resources to IoT devices in all frames within a transmission set, rather than dynamic scheduling, as a scheduling method. In this case, the leader can set a static scheduling flag included in the scheduling information and transmit it to the IoT device. For example, the leader can allocate 12 frequency resources to IoT device A in symbol 4 of the first R2D frame included in transmission set #1. Additionally, the leader can allocate 12 frequency resources to IoT device A in symbol 4 of the second R2D frame included in transmission set #1. At this time, the leader can transmit scheduling information including such allocation information to the IoT device by setting a static scheduling flag. In this way, the leader can allocate 12 frequency resources to the IoT device in symbol 4 of the second R2D frame as well as the first R2D frame of transmission set #1 without explicitly transmitting scheduling information.

The CRC field contains information for detecting errors in the transmitted R2D link frame and can be derived using a system-defined polynomial. The reader can add the derived CRC field to the frame and transmit it. IoT devices can receive frames containing the CRC field and detect frame errors by comparing the CRC field of the received frame calculated using the polynomial with the CRC field included in the frame.

Figure 9 is a conceptual diagram illustrating examples of data frames of type 1.

Referring to FIG. 9, a data frame of type 1 may include a preamble, frame type information, random access response information, data, and a CRC field. The data may correspond to the setup of the R2D frame of type 1 and scheduling information of the control information transmission frame. The preamble may include information indicating the start of the R2D frame. The information about the frame type may be information indicating the type of R2D frame transmitted, such as a control frame or a data frame.

Information about a random access response may be information indicating a response to a signal transmission for random access transmitted from an IoT device in a previous D2R frame. For example, an IoT device may transmit a random access signal to a leader in the first symbol and the third frequency resource of a random access occasion of a D2R frame. The IoT device may receive a response signal in the same location (the first symbol and the third frequency resource) of the radio resources of a random access response of an R2D frame. In this case, the IoT device may determine that the leader has received the random access signal. In addition, the IoT device may determine that the leader has transmitted a response to the random access signal. In addition, the IoT device may determine that the leader has received a response to the random access signal. In another embodiment, the IoT device may confirm the random access result on a D2R frame through a mapping relationship included in the random access resource configuration information of the R2D frame. The data may indicate information transmitted from the operation of the AIoT network and upper application layers. The CRC field may contain information for detecting errors in the R2D frame being transmitted.

Figure 10 is a conceptual diagram illustrating embodiments of a type 2 R2D (reader to device) frame.

Referring to FIG. 10, a Type 2 R2D frame may include control information for setting and allocating wireless resources of a transmission set and data transmitted from a leader to a device. A Type 2 R2D frame may include a preamble including a synchronization signal, frame setting information within a transmission set, random access resource setting information, random access response information, scheduling information of R2D frames and D2R frames included in the transmission set, data, and a CRC field.

The preamble of the R2D frame of type 2, the frame setup information within the transmission set, the random access resource setup information, the random access response information, and the scheduling information of the R2D frame and D2R frame included in the transmission set may be identical to the contents of the control frame of the R2D frame of type 1 described above. The CRC field may be used to detect errors in the R2D frame.

3-2. D2R frame structure

IoT devices in an AIoT network can receive wireless resource configuration and allocation control information in R2D frames from the leader. Furthermore, the IoT devices can transmit D2R frames to the leader based on the received wireless resource configuration and allocation control information.

Figure 11 is a conceptual diagram showing embodiments of a D2R (device to reader) frame.

Referring to FIG. 11, a D2R frame may include a preamble, a time measurement signal or a timestamp, random access opportunities (RA opportunities), data, and a CRC field. The preamble may be information indicating the start of the D2R frame. The measurement signal or timestamp may be information used by the reader to measure the proximity of an IoT device. For proximity measurement based on the measurement signal, the IoT device may transmit a signal based on a preset sequence on a wireless resource at a preset time and frequency. Then, the reader may receive the signal and determine the proximity of the IoT device. In this method, the IoT device may transmit a signal with a preset strength.

The reader can estimate the distance between the reader and the IoT device based on the reception strength of the received signal, such as the reference signal received power (RSRP). Another method is to utilize a timestamp. Based on the global time set by the reader, the IoT device can transmit a timestamp, which is a time value based on the operating clock, to the reader when transmitting the D2R frame. The reader can receive the timestamp from the IoT device and estimate the distance between the reader and the device by comparing the reception time of the D2R frame with the timestamp included in the D2R frame.

A random access opportunity can refer to wireless resources in the frequency and time dimensions. The wireless resources of a random access opportunity can consist of signal resources and identifier resources. IoT devices can use the signal resources of a random access opportunity to transmit signals for random access to the leader. IoT devices can use the identifier resources of a random access opportunity to transmit an identifier that identifies the IoT device to the leader.

At this time, the IoT device can transmit capability information of the IoT device along with its identifier to the leader using the identifier resource of the random access opportunity. The data can indicate information transmitted from the operation of the AIoT network and upper application layer, etc. transmitted from the IoT device to the leader. The data can be transmitted by utilizing the radio resources and physical layer operation parameters set according to the D2R grant scheduling information transmitted in the R2D frame. The CRC field can be used to detect errors in the transmitted D2R frame.

4. Connection Method

In an AIoT network, IoT devices can utilize energy harvesting to charge their built-in energy storage. IoT devices can perform random access and registration procedures while being able to transmit D2R frames. During the random access and registration procedures, IoT devices can use the D2R link to transmit their identifiers and capabilities to the leader based on wireless resource configuration information configured by the leader. During the random access and registration procedures, the leader can receive the identifiers and capabilities from IoT devices and identify IoT devices within its service area.

4-1. Connection method using 4-step message exchange

IoT devices can connect to a reader using a four-step message exchange.

Figure 12 is a flowchart illustrating embodiments of a connection method using a four-step message exchange.

Referring to FIG. 12, a connection method using a four-step message exchange may include a random connection resource setting information receiving step (S1201), a random connection signal transmitting step (S1202), a random connection response receiving step (S1203), an IoT device identifier and capability information transmitting step (S1204), a response receiving step (S1205), a data transmission/reception step (S1206), etc.

4-1-1-0. Step 1: Receiving random access resource configuration information

The leader can transmit an R2D frame including random access resource configuration information, which is composed of allocation information of wireless resources and scheduling information, to the IoT device. The random access resource configuration information can include information about the location of a D2R frame for random access and the locations of wireless resources of random access occasions in the D2R frame. The IoT device can receive an R2D frame including random access resource configuration information, which is composed of allocation information of wireless resources and scheduling information, from the leader. The IoT device can determine the location of the D2R frame for random access and the locations of wireless resources of random access occasions in the D2R frame from the allocation information of wireless resources and scheduling information of the received R2D frame. The leader can transmit the random access resource configuration information to the IoT device using a paging message. The IoT device can receive the random access resource configuration information through the paging message.

4-1-1-1. Transmitting a random access signal

IoT devices can select wireless resources for random access based on the allocation and scheduling information in the R2D frame received from the leader. When selecting wireless resources for random access, IoT devices can utilize the random access resource configuration information provided by the leader.

For example, in the random access resource configuration, there may be three symbols capable of transmitting random access signals, and three frequency resources per symbol. In this case, an IoT device can select one random access occasion from a total of nine random access occasions and transmit a random access signal to the leader using the radio resources of the selected random access occasion. The random access signal may be Msg1.

To this end, the IoT device can select a random number from 0 to 8 based on the value 9 provided in the selection window for selecting a random access resource included in the random access resource configuration information. The IoT device can decrease the selected random number by 1 whenever a random access occasion occurs. The IoT device can transmit a random access signal to the leader on the wireless resource corresponding to the point in time when the random number becomes 0.

The random access signal can be a signal similar to the NR (new radio) random access channel (RACH) preamble or an on-off signal. An IoT device can initiate random access by transmitting a predefined on signal on a selected radio resource. Alternatively, the random access signal can be multiplexed and transmitted on time resources or frequency resources depending on a multiplexing method. Alternatively, if code-based multiplexing is considered for transmission depending on the type of signal being transmitted, multiple random access signals can be transmitted and decoded on the same time-frequency resource.

An IoT device may not receive a response within a set time period after transmitting a random access signal. In this case, the IoT device may determine that a random access signal collision has occurred. Alternatively, the IoT device may determine that the random access signal was not received by the leader.

To achieve this, IoT devices can identify wireless resources for random access responses based on a timer. The timer value can be a preset value for the IoT device. Alternatively, the timer value can be a waiting time for a random access response transmitted from the reader to the IoT device using an R2D frame.

By transmitting a different type of random access signal and then waiting for a response, IoT devices can identify wireless resources for random access responses based on the frame. The frame value for waiting for a response can be a value preset for the IoT device. Alternatively, the frame value for waiting for a response can be the waiting time for a random access response transmitted from the leader to the IoT device using an R2D frame.

An IoT device may not be able to confirm a response signal on a wireless resource for a random access response even after a set time interval has elapsed. In such a case, the IoT device can reset the length of the random access interval based on the selection window reset information for selecting a random access resource received from the leader. The IoT device can select an arbitrary number and re-perform the random access procedure. For example, when extending the random access interval by an exponent of 2, the IoT device can double the size of the selection window for selecting an existing random access resource. Then, the IoT device can select an arbitrary number from the selection window for selecting a random access resource that has been doubled in size and then perform the random access signal transmission described above.

4-1-1-2. Receiving a random access response

The reader can determine whether a random access signal is received from an IoT device by decoding wireless resources for random access opportunities (RA opportunities). For example, the reader may not detect a random access signal in the resources for the configured random access opportunity. In this case, the reader can recognize the absence of the IoT device attempting to connect. Conversely, the IoT device may detect a random access signal in the wireless resources for the configured random access opportunity. In this case, the reader can recognize the presence of the IoT device attempting to connect. The reader can generate a response signal to enable the IoT device to confirm whether the IoT device has received the random access signal and transmit the generated response signal to the IoT device. The response signal may be Msg2.

The reader can detect a random access signal from resources for a configured random access opportunity. In this case, the reader can transmit a response signal to the IoT device using radio resources for a random access response (RA response) of the R2D frame. The response signal can be an on/off-based signal in the same format as the random access signal transmitted by the IoT device during the random access opportunity. In addition, the reader can allocate radio resources capable of transmitting the identifier of the IoT device. The reader can allocate radio resources capable of transmitting the identifier of the IoT device in a predefined format.

4-1-1-3. Transmitting IoT device identifiers and capability information

An IoT device can receive a response signal from a radio resource for a random access response (RA response) of an R2D frame received from a leader. The IoT device can transmit a signal (in other words, Msg3) including an identifier that can identify the IoT device and information on the capabilities that the IoT device can support to the leader. The identifier of the IoT device can mean a unique value of fixed length or an arbitrary selection value. The capabilities of the IoT device can mean functions and capabilities that the IoT device can provide. The capabilities of the IoT device can be, for example, information on the type of the IoT device. The capability information of the IoT device can be expressed as a fixed-length value. The radio resource for transmitting the identifier of the IoT device and the information on the capabilities that the IoT device can support can utilize radio resources for a random access occasion of the random access resource configuration of the D2R frame.

The identifier of an IoT device can be either a temporary identifier or a unique identifier. A temporary identifier can be a random number, a randomly selected value, etc. A unique identifier is a unique permanent identifier. It can be the entire upper-layer device identifier, a portion of the upper-layer device identifier, etc. A unique permanent identifier can be an electronic product code (EPC). A unique identifier can also be used as a temporary identifier.

The IoT device can use a random number as a temporary identifier for Msg1. Alternatively, the IoT device can use the device identifier as a temporary device identifier for Msg1. In the method using a random number, the IoT device can select a random number within a selection range provided by the reader and use it as a temporary identifier. In the method using a random number, the IoT device may require a maximum value of a selection window for selecting a random number. The reader can transmit the maximum value of the selection window to the IoT device. The IoT device can receive the maximum value of the selection window from the reader. Alternatively, the IoT device can use a preset maximum value of the selection window.

In contrast, in a method using device identifiers, IoT devices can utilize the device ID set in the upper layer as the device identifier for Msg1. In this method of using device identifiers, IoT devices can use either the entire device identifier or a portion of the device identifier.

The 3GPP service and system aspects working group 2 (SA2), a technical standardization group within 3GPP responsible for service and system architecture, discussed device identifiers by dividing them into permanent identifiers and temporary identifiers. SA2 discussed the use of long temporary identifiers as suitable identifiers between AIoT controllers and readers, and the use of short temporary identifiers as suitable identifiers between IoT devices and readers. Therefore, IoT devices can generate identifiers included in Msg1 using upper-layer device identifiers. In this case, it may be more appropriate in terms of radio resource consumption and security to generate and transmit a short temporary identifier rather than using a long full device identifier in the IoT device. In addition, when the IoT device generates a temporary identifier, it may also be necessary to configure which form it should be selected from the full device identifier.

The methods using random numbers and those using a portion of the device identifier may be similar. However, as considered in SA2, temporary identifiers can be assigned from the core network (CN) through a registration procedure. Therefore, IoT devices can generate device identifiers used in Msg1 of the random access procedure from permanent identifiers. The permanent identifiers can be composed of a mobile network operator ID (MNO ID), an owner ID, and an instance ID. The probability of generating identical identifiers may be higher than that of using random numbers. Therefore, using a random number as the device identifier used in Msg1 may have many advantages over using a portion of the device identifier.

Based on the requirements of the use cases of SA1 (3GPP service and system aspects working group 1), the inventory service can accommodate a device density of up to 1.5 million. However, this represents the maximum number of IoT devices per square kilometer (km2) that can be accommodated in indoor environments, and may not necessarily be the number of devices that a single reader should accommodate.

However, for example, if a single reader performs inventory services in a space measuring 100 or 200 meters in length and width, simultaneous connections from up to 1,000 or 60,000 IoT devices can be considered. Therefore, considering the reader's service area and the transmission power of IoT devices, the device identifier transmitted in Msg1 should be at least 16 bits.

The success or failure of Msg3 can be evaluated differently depending on the use case. In the case of inventory-only use, there is no additional data transmission after Msg3, so the IoT device cannot determine whether the device identifier was successfully transmitted. In the case of inventory and command use, an additional command is transmitted after Msg3, so the IoT device can determine that Msg3 was successfully transmitted upon receiving the command message. In the case of command-only use, since random access is not used, the IoT device may not need to determine whether Msg3 was successfully transmitted.

- Explicit mechanism with response (response message for Msg3 reception): This approach may include defining an Access Stratum (AS)-level message to respond to Msg3 reception. The reader may send an acknowledgment when Msg3 is successfully received. The reader may send a negative acknowledgment when Msg3 is not received. In this approach, the reader may send an ACK when Msg3 is successfully received. If the reader does not receive Msg3, it may send a NACK.

- Explicit retransmission mechanism (retransmission of Msg2): If the leader does not receive Msg3 within a certain amount of time after transmitting Msg2, it can retransmit Msg2. Upon receiving the retransmitted Msg2, the IoT device can retransmit Msg3.

- Implicit Mechanism (Inventory Service Reinitialization): If Msg3 is not received within a specified period after Msg2 is transmitted, the leader can request the IoT device to reinitialize the inventory service via a paging message. In this case, the IoT device can retransmit Msg1 at the leader's request. If the IoT device does not receive the inventory service reinitialization request, the leader can assume that Msg3 was successfully received.

As mentioned earlier, indicating the success or failure of a msg3 transmission to a device can be achieved using different approaches depending on the use case, or a new AS-layer message can be defined that uses a consistent method across use cases. However, because AIoT services typically have limited time constraints and are mostly best-effort, it may be more practical to re-execute the leader's procedure to verify the success of the msg3 transmission rather than defining a specific response message. Therefore, an implicit mechanism, rather than an explicitly defined message, can be used to determine the success of the msg3 transmission.

4-1-1-4. Receiving a response to the transmission of IoT device identifier and capability information.

The leader can receive a D2R frame from an IoT device, including the IoT device's identifier and capability information. The leader can decode the wireless resources for the IoT device's identifier presented in the random access configuration of the received D2R frame. Furthermore, the leader can verify the identifier of the IoT device that performed the random access and the capability information of the IoT device.

In this procedure, multiple IoT devices may transmit identifiers of the IoT devices using wireless resources for the identifiers of the same IoT device. In this case, a decoding error may occur. Alternatively, a decoding error may not occur. The reader may perform a registration procedure for the IoT device based on the identifier of the IoT device received from the IoT device. The reader may notify the device that identifier reception is complete through a response signal of the R2D frame (i.e., Msg4). The IoT device may receive a response signal from the reader.

An IoT device can transmit an arbitrary selection value to the reader as its identifier. In this case, the selection value of the randomly selected IoT device may conflict with the identifier of a previously registered IoT device. In this case, the reader can generate a response signal including a new selection value (e.g., an Access Stratum (AS) layer identifier) that does not conflict and transmit the generated response signal to the IoT device. The IoT device can receive the response signal including the new selection value. The IoT device can use the new selection value as a temporary identifier of the IoT device. To this end, the reader can transmit information to the IoT device in the control information of the response signal of the R2D frame that assigns a new identifier to the IoT device. The identifier or temporary identifier of the registered IoT device can be used as an identifier for data transmission on the R2D link or the D2R link. The capabilities of the IoT device can be utilized for scheduling wireless resources, etc.

During the 4-step random access procedure, if the leader fails to receive Msg3, it can use Msg4. For example, during the random access procedure, the IoT device may not transmit Msg3 due to insufficient available energy for communication. Alternatively, during the random access procedure, the IoT device may not transmit Msg3 if its transmission power is low. In such a situation, the leader may not receive Msg3 even after a certain period of time has passed since transmitting Msg2. The leader may infer that a transmission error has occurred. To resolve this, the leader can use Msg2 as a message instructing retransmission of Msg3. The leader can transmit Msg2, instructing retransmission of Msg3, to the IoT device. The IoT device can receive Msg2, instructing the leader to retransmit Msg3. The IoT device can retransmit Msg3 according to the instruction of Msg2. The leader can receive Msg3 from the IoT device.

4-1-1-5. Data transmission

An IoT device can receive a response from the leader to the transmission of its identifier. An IoT device that has completed registration in this manner can transmit and receive data in the following ways. The response to the transmission of its identifier may be an identifier response.

After transmitting a response signal to the transmission of the IoT device's identifier, the leader can transmit device terminated (DT) traffic to the IoT device. To this end, the leader can configure the IoT device's identifier for data reception and time/frequency-based radio resource allocation information in the R2D allocation of scheduling information. The leader can encapsulate application data received from the upper layer to create an R2D frame and transmit the created R2D frame to the IoT device. The IoT device can receive the R2D frame from the leader and check the application data.

A leader can perform D2R scheduling for registered IoT devices periodically or based on events. Through this, IoT devices can receive identifier responses and transmit DO (device originated) and DO-DTT (device originated-device terminated triggered) traffic to the leader based on D2R scheduling. To this end, the IoT device decodes D2R grant information, which includes the IoT device identifier and time/frequency-based radio resource allocation information provided by the leader, and then encapsulates application data received from a higher layer to generate a D2R frame. The IoT device can transmit the generated D2R frame to the leader. The leader can receive D2R frames from IoT devices. The leader can check the application data in the received D2R frame.

Figure 13 is a flowchart illustrating embodiments of a connection method using a four-step message exchange.

Referring to Fig. 13, a connection method using a four-step message exchange may include a connection setup information receiving step (S1301), a connection signal transmitting step (S1302), a resource allocation information receiving step (S1303), an IoT device identifier transmitting step (S1304), a response receiving step (S1304), etc.

4-1-2-0. Receiving connection setup information

The leader can generate connection configuration information that includes information about a transmission set, information about resource configuration of a connection occasion, and information about operational parameters of a random connection. The leader can transmit the generated connection configuration information to an IoT device. The IoT device can receive the connection configuration information from the leader. The leader can transmit the connection configuration information to the IoT device using a paging message. The IoT device can receive the connection configuration information via the paging message.

A transmission set can define multiple transmission opportunities. A transmission set can consist of access occasions and R2D/D2R frames. The resource configuration of an access occasion can be radio resource information of the access occasion. The resource configuration of an access occasion can include multiple access occasions in the time, frequency, or code domain. The resource configuration of an access occasion can specify the number of access occasions and resource allocation for each access occasion. The number of access occasions can define the number of opportunities for connection from an IoT device during a specific period. The resource allocation for each access occasion can refer to time, frequency, or code domain resources allocated to each access occasion.

Recently, at the RAN2 (radio access network 2) meeting, a working group that standardizes layer 2 and layer 3 protocols of radio access networks (RAN) within the 3rd generation partnership project (3GPP), it was decided to use slotted-ALOHA (additive links on-line Hawaii area) as the basic mechanism for AIoT random access. Therefore, the selection window size and backoff-related information may be key parameters for slotted-ALOHA and random access. The selection window size may refer to the maximum value for generating a random number when selecting an access occasion in an IoT device. The selection window size may be similar to the Q parameter in RFID (radio frequency identification). Backoff-related parameters may consider waiting time and backoff window. The waiting time may refer to the maximum time that an IoT device must wait for a response message after transmitting an access signal. A backoff window describes a mechanism for expanding the selection window size used for random number generation when a collision occurs. This prevents IoT devices from retransmitting at the same time on subsequent connection attempts.

4-1-2-1. Transmitting a connection signal

An IoT device can receive connection configuration information from a leader. The IoT device can extract radio resources of access occasions designated for random access from the connection configuration information. The IoT device can randomly select one access occasion to transmit an access signal from the radio resources of the access occasions designated for random access. The IoT device can randomly select a number within a selection window designated for selecting an access occasion. The IoT device can decrease the random number by 1 whenever a new access occasion occurs. When the random number becomes 0, the IoT device can transmit an access signal to the leader from the designated resource. The access signal can be Msg1.

IoT devices can use a signal similar to the NR RACH preamble or a code-multiplexed signal as the access signal. These access signal transmission steps can be applied in a 4-step procedure.

4-1-2-2. Receiving resource allocation information

An IoT device can transmit a connection signal to a reader. The reader can receive the connection signal from the IoT device. In response to the connection signal, the reader can transmit an acknowledgment to the IoT device. The acknowledgment may be Msg2. The reader can allocate wireless resources that enable the IoT device to transmit an identifier. The reader can transmit an acknowledgment response to the IoT device that includes information about the allocated wireless resources for transmitting the identifier.

While various scheduling mechanisms can be considered, the complexity and energy limitations of AIoT devices may necessitate a simple approach. IoT devices may not receive a positive response or information about allocated wireless resources within a certain timeframe. In this case, the IoT device can apply a backoff mechanism to re-perform Step 1 (i.e., the connection signal transmission step). The resource allocation information reception step can be applied to specific procedures.

4-1-2-3. Transmitting the IoT device identifier

In the 4-step procedure, the IoT device can receive an acknowledgment response from the leader, which includes information about the radio resources allocated for transmitting the identifier. The IoT device can transmit a signal including its identifier to the leader using the radio resources allocated for transmitting the identifier. Here, the signal can be Msg3. Alternatively, in the 2-step procedure, a connection occasion can be randomly selected using random number generation. This can be similar to the "connection signal transmission" in step 1. After the IoT device randomly selects a connection occasion, it can transmit its identifier to the leader.

The identifier of an IoT device can be either a temporary identifier or a unique identifier. A temporary identifier can be a random number, a randomly selected value, etc. A unique identifier is a unique permanent identifier. It can be the entire upper-layer device identifier, a portion of the upper-layer device identifier, etc. A unique permanent identifier can be an electronic product code. A unique identifier can also be used as a temporary identifier.

The IoT device can use a random number as a temporary identifier for Msg1. Alternatively, the IoT device can use the device identifier as a temporary device identifier for Msg1. In the method using a random number, the IoT device can select a random number within a selection range provided by the reader and use it as a temporary identifier. In the method using a random number, the IoT device may require a maximum value of a selection window for selecting a random number. The reader can transmit the maximum value of the selection window to the IoT device. The IoT device can receive the maximum value of the selection window from the reader. Alternatively, the IoT device can use a preset maximum value of the selection window.

In the method using device identifiers, IoT devices can utilize the device ID set in the upper layer as the device identifier for Msg1. In the method using device identifiers, IoT devices can use the entire device identifier or a portion of the device identifier.

SA2, a technical standardization group of 3GPP responsible for service and system architecture, discussed device identifiers by dividing them into permanent identifiers and temporary identifiers. SA2 discussed the use of long temporary identifiers as suitable identifiers between AIoT controllers and readers, and the use of short temporary identifiers as suitable identifiers between IoT devices and readers. Therefore, IoT devices can generate identifiers included in Msg1 using upper-layer device identifiers. In this case, it may be more appropriate in terms of radio resource consumption and security to generate and transmit a short temporary identifier rather than using a long full device identifier in the IoT device. In addition, when an IoT device generates a temporary identifier, it may also be necessary to configure which form it should be selected from the full device identifier.

The use of random numbers and the use of a portion of the device identifier may be similar. However, as considered in SA2, temporary identifiers can be assigned from the core network through a registration procedure. Therefore, IoT devices can generate device identifiers used in Msg1 of the random access procedure from permanent identifiers. Permanent identifiers can be composed of a mobile carrier identifier, an owner identifier, and an instance identifier. The probability of generating identical identifiers may be higher than that of using random numbers. Therefore, using a random number as the device identifier used in Msg1 may have many advantages over using a portion of the device identifier.

Based on the requirements of the SA1 use case, the inventory service can accommodate a device density of up to 1.5 million devices. However, this represents the maximum number of IoT devices per square kilometer (km2) that can be accommodated in an indoor environment, and may not necessarily be the number of devices that a single reader should accommodate.

However, for example, if a single reader performs inventory services in a space measuring 100 or 200 meters in length and width, simultaneous connections from up to 1,000 or 60,000 IoT devices can be considered. Therefore, considering the reader's service area and the transmission power of IoT devices, the device identifier transmitted in Msg1 should be at least 16 bits.

The success or failure of Msg3 can be evaluated differently depending on the use case. In the case of inventory-only use, there is no additional data transmission after Msg3, so the IoT device cannot determine whether the device identifier was successfully transmitted. In the case of inventory and command use, additional commands are transmitted after Msg3, so the IoT device can determine that Msg3 was successfully transmitted upon receiving the command message. In the case of command-only use, since random access is not used, the IoT device may not need to determine whether Msg3 was successfully transmitted.

- Explicit mechanism with response (response message for Msg3 reception): This approach may include defining an AS-level message to respond to Msg3 reception. The reader may send an acknowledgment when Msg3 is successfully received. The reader may send a negative acknowledgment when Msg3 is not received. In this approach, the reader may send an ACK when Msg3 is successfully received. If the reader fails to receive Msg3, it may send a NACK.

- Explicit retransmission mechanism (retransmission of Msg2): If the leader does not receive Msg3 within a certain amount of time after transmitting Msg2, it can retransmit Msg2. Upon receiving the retransmitted Msg2, the IoT device can retransmit Msg3.

- Implicit Mechanism (Inventory Service Reinitialization): If Msg3 is not received within a specified period after Msg2 is transmitted, the leader can request the IoT device to reinitialize the inventory service via a paging message. In this case, the IoT device can retransmit Msg1 at the leader's request. If the IoT device does not receive the inventory service reinitialization request, the leader can assume that Msg3 was successfully received.

As mentioned earlier, indicating the success or failure of a msg3 transmission to a device can be achieved using different approaches depending on the use case, or a new AS-layer message can be defined that uses a consistent method across use cases. However, because AIoT services typically have limited time constraints and are mostly best-effort, it may be more practical to re-execute the leader's procedure to verify the success of the msg3 transmission rather than defining a specific response message. Therefore, an implicit mechanism, rather than an explicitly defined message, can be used to determine the success of the msg3 transmission.

4-1-2-4. Receiving a response

The reader can receive a signal including an identifier from the IoT device. Accordingly, the reader can successfully decode the identifier in the received signal and confirm the absence of a collision. The reader can transmit an acknowledgment including the identifier of the IoT device received in the previous step to the IoT device. The acknowledgment may be Msg4. The IoT device can receive the acknowledgment from the reader. Alternatively, the IoT device cannot receive the acknowledgment. Then, the IoT device can determine that the collision resolution is not complete. The IoT device can apply a backoff mechanism to perform step 1 (i.e., the connection signal transmission step) or step 3 (i.e., the identifier transmission step of the IoT device) again.

Contention may occur between different devices. In such cases, a re-access mechanism can be used to resolve contention. A transmission set may have only one connection occasion. In this case, the next connection occasion can be specified in a subsequent connection establishment message. However, for transmission sets with multiple connection occasions, a backoff mechanism may be an appropriate re-access mechanism to reduce the probability of contention. For example, a backoff mechanism could expand the selection window size used to generate random numbers for reconnection attempts. Therefore, the leader can provide the device(s) with a connection retry mechanism that can handle contention.

4-2. Random access method using three-step message exchange

IoT devices can connect to a reader using a three-step message exchange.

Figure 14 is a flowchart illustrating embodiments of a connection method using a three-step message exchange.

Referring to Fig. 14, a connection method using a three-step message exchange may include a connection setting information receiving step (S1401), a temporary device identifier transmitting step (S1402), a temporary device identifier receiving step (S1403), and a device identifier transmitting step (S1404).

4-2-1-0. Receiving connection setup information via Msg0

Inventory and command services considered in AIoT networks can be procedures initiated by network demands. These services may require wireless resource configurations tailored to network requirements. Wireless resources in AIoT networks can be divided into wireless resources for R2D links, which transmit control information and data from the leader to IoT devices, and wireless resources for D2R links, which transmit data from IoT devices to the leader.

An AIoT controller or an application function (AF) entity of a core network can transmit a service request signal to a leader to request a service (S1400). Then, the leader can receive the service request signal from the AIoT controller or AF entity. The leader can initiate a service according to the service request received from the AIoT controller or AF entity. The unit that performs such a service can be defined as a transmission set. For example, an inventory and command service can be a service that detects the identifiers of IoT devices in the vicinity and reads the status information of a specific IoT device. Such an inventory and command service can be configured as a single transmission set.

Figure 15 is a conceptual diagram illustrating embodiments of random access resource configuration based on a transmission set.

Referring to FIG. 15, one transmission set #n or transmission set #n+1 can be configured as a wireless resource for transmitting an R2D frame or a D2R frame. N can be a positive integer. The wireless resource for transmitting an R2D frame can be configured as a resource for transmitting configuration information within the transmission set and a resource for transmitting data from the leader to the IoT device. In an AIoT network, IoT devices cannot receive periodic system information such as NR's SIB (system information block) due to battery status and low capability. Therefore, the leader can transmit configuration information of wireless resources for transmitting an R2D frame or a D2R frame and information to be transmitted to IoT devices through configuration information in units of transmission sets.

In contrast, resources for transmitting D2R frames can be comprised of random access resources for random access and data transmission resources for transmitting data from IoT devices to the leader. The random access procedure may involve multiple IoT devices transmitting their identifiers to the leader. To this end, IoT devices can utilize the configuration information in the R2D frame to obtain configuration information, such as wireless resource settings and operating methods, for random access.

Multiple IoT devices can perform random access in a single transmission set. To this end, a leader can allocate resources for multiple random accesses. Here, the resources for multiple random accesses can be defined as access occasions. Access occasions can be divided into shared access occasions (sharded access occasions) and dedicated access occasions (dedicated access occasions). In the case of contention-based random access (CBRA), IoT devices can select one of the shared access occasions and transmit data to the leader using the selected shared access occasion. In the case of contention-free random access (CFRA), IoT devices can transmit information to the leader through a dedicated access occasion set in the IoT device's identifier.

Referring again to FIG. 14, the leader can transmit resource configuration information for random access to the IoT device for transmitting an R2D frame or a D2R frame through a transmission set (S1401). The IoT device can receive resource configuration information for random access from the leader. The leader can transmit resource configuration information for random access to the IoT device using a paging message. The IoT device can receive resource configuration information for random access through the paging message.

Through the resource configuration and operation procedures described above, IoT devices may require the following resource configuration information for random access.

- Resource configuration information for random access

o Setting up wireless resources for CBRA and CFRA

o Setting up wireless resources for connection occasions

o Setting up wireless resources(s) for Msg2 (i.e., response to Msg1 in random access)

- Configuration information for IoT device operation

o Wait time for receiving Msg2 after sending Msg1

o Selection window for selecting connection occasions

o Maximum number of retransmission attempts

o Transmission power ramping configuration, if required

The leader can variably configure configuration information for random access, taking into account factors such as the density of IoT devices and network load. Therefore, the leader may require a procedure to transmit message-based configuration information to IoT devices.

4-2-1-1. Sending a temporary device identifier via Msg1

IoT devices can utilize wireless resources for established random access to transmit an identifier to the leader via Msg1 (S1402). The identifier may be a temporary identifier or a temporary device identifier. The purpose of Msg1 may be to notify the network of the presence of the IoT device. To this end, each IoT device can generate a different temporary device identifier and transmit the generated device identifier to the leader.

The identifier of an IoT device can be either a temporary identifier or a unique identifier. A temporary identifier can be a random number, a randomly selected value, etc. A unique identifier is a unique permanent identifier. It can be the entire upper-layer device identifier, a portion of the upper-layer device identifier, etc. A unique permanent identifier can be an electronic product code. A unique identifier can also be used as a temporary identifier.

The IoT device can use a random number as a temporary identifier for Msg1. Alternatively, the IoT device can use the device identifier as a temporary device identifier for Msg1. In the method using a random number, the IoT device can select a random number within a selection range provided by the reader and use it as a temporary identifier. In the method using a random number, the IoT device may require a maximum value of a selection window for selecting a random number. The reader can transmit the maximum value of the selection window to the IoT device. The IoT device can receive the maximum value of the selection window from the reader. Alternatively, the IoT device can use a preset maximum value of the selection window.

In contrast, in a method using device identifiers, IoT devices can utilize the device ID set in the upper layer as the device identifier for Msg1. In this method of using device identifiers, IoT devices can use either the entire device identifier or a portion of the device identifier.

SA2, a technical standardization group of 3GPP responsible for service and system architecture, discussed device identifiers by dividing them into permanent identifiers and temporary identifiers. SA2 discussed the use of long temporary identifiers as suitable identifiers between AIoT controllers and readers, and the use of short temporary identifiers as suitable identifiers between IoT devices and readers. Therefore, IoT devices can generate identifiers included in Msg1 using upper-layer device identifiers. In this case, it may be more appropriate in terms of radio resource consumption and security to generate and transmit a short temporary identifier rather than using a long full device identifier in the IoT device. In addition, when an IoT device generates a temporary identifier, it may also be necessary to configure which form it should be selected from the full device identifier.

The use of random numbers and the use of a portion of the device identifier may be similar. However, as considered in SA2, temporary identifiers can be assigned from the core network through a registration procedure. Therefore, IoT devices can generate device identifiers used in Msg1 of the random access procedure from permanent identifiers. Permanent identifiers can be composed of a mobile carrier identifier, an owner identifier, and an instance identifier. The probability of generating identical identifiers may be higher than that of using random numbers. Therefore, using a random number as the device identifier used in Msg1 may have many advantages over using a portion of the device identifier.

Based on the requirements of the SA1 use case, the inventory service can accommodate a device density of up to 1.5 million devices. However, this represents the maximum number of IoT devices per square kilometer (km2) that can be accommodated in an indoor environment, and may not necessarily be the number of devices that a single reader should accommodate.

However, for example, if a single reader performs inventory services in a space measuring 100 or 200 meters in length and width, simultaneous connections from up to 1,000 or 60,000 IoT devices can be considered. Therefore, considering the reader's service area and the transmission power of IoT devices, the device identifier transmitted in Msg1 should be at least 16 bits.

The IoT device can determine whether the transmission of Msg1 was successful or not based on whether Msg2 was received. After transmitting Msg1, the IoT device can receive Msg2. The IoT device can determine that the transmission of Msg1 was successful if the received Msg2 includes the random number transmitted through its own Msg1. The IoT device can consider Msg1 transmission failure if Msg2 is not received or if Msg2 does not contain the random number. The cause of the Msg1 transmission failure may be a collision of multiple devices or a transmission error in the D2R link.

After transmitting Message 1, an IoT device can wait for Message 2 for a certain amount of time. If the IoT device fails to receive Message 2 within this time limit, or if the received Message 2 does not contain its own random number, it may determine that Message 1 transmission has failed. Therefore, a method utilizing a timer mechanism to determine the success or failure of Message 1 may be necessary.

4-2-1-2. Receiving a temporary device identifier via Msg2

The reader can receive Msg1 including temporary device identifier information from the IoT device. The reader can transmit Msg2, which is a response to Msg1, to the IoT device (S1403). The reader can transmit Msg2 including the temporary device identifier information received from the IoT device and additional configuration information to the IoT device. The IoT device can receive Msg2 including the temporary device identifier information and additional configuration information transmitted from the reader. The temporary device identifier information included in Msg2 may be identical to the temporary device identifier transmitted by the IoT device through Msg1.

In this case, the leader can recognize the IoT device and determine that the random access procedure has been successfully completed. Additional configuration information may include radio resource scheduling information for transmitting Msg3, encryption method, etc. The radio resource configuration information of AIoT can consider a new, simple method that considers the capabilities of the IoT device, rather than the scheduling based on DCI (downlink control information) considered in the existing NR. For example, resources composed of frequency domain and time domain allocated with a fixed size can be configured as x, y coordinate values in a table format or a linear list. In addition, the x, y coordinate values in a table format or the linear list can be mapped to a device identifier.

For security reasons, Msg3 may include a device identifier. Msg2 may include encryption settings required for secure transmission over the wireless interface between the IoT device and the reader. RAN2 may also consider the security issues discussed in SA2 and SA3.

4-2-1-3. Sending device identifier via Msg3

The step of transmitting the device identifier via Msg3 may be identical to the procedure of step 3 of the connection method using a 4-step message exchange. In other words, using the encryption method received in Msg2, the IoT device can transmit Msg3 containing its own unique device identifier to the reader (S1404). The reader can receive Msg3 containing the unique device identifier of the IoT device from the IoT device. The reader that receives the message can determine that the random connection procedure has been completed and can transmit a service response message to the AIoT controller or AF entity (S1405). The service response message may include the unique device identifier of the IoT device.

Contention may occur between different devices. In such cases, a reconnection mechanism can be used to resolve contention. A transmission set may have only one connection occasion. In this case, the next connection occasion can be specified in a subsequent connection establishment message. However, for transmission sets with multiple connection occasions, a backoff mechanism may be an appropriate reconnection method to reduce the probability of contention. For example, a backoff mechanism could expand the selection window size used to generate random numbers for reconnection attempts. Therefore, the leader can provide a connection retry mechanism to the devices through paging to handle contention.

After transmitting the initial Msg1, if the IoT device does not receive Msg2 within a certain period of time or if the received Msg2 does not include its device ID, the IoT device may recognize that contention has occurred and initiate a re-access procedure. To re-connect, the IoT device may select a new connection occasion and retransmit Msg1 using a backoff mechanism. The backoff mechanism may operate by increasing the selection window size for connection occasion selection to reduce the probability of collision. Accordingly, the connection occasion for retransmitting Msg1 may be selected from the current transmission set or a new transmission set. To support this, the IoT device may require the following configuration information.

o Waiting time for receiving Msg2 after sending Msg1

o Selection window size for connection occasion reselection

o Maximum number of retransmission attempts

o Set transmission power ramping when needed

If the leader does not receive Msg3 after transmitting Msg2, it can retransmit Msg2 to request a retransmission of Msg3. Therefore, if an IoT device receives Msg2 from the leader again after transmitting Msg3, it can interpret this as a request to retransmit Msg3 and retransmit Msg3 to the leader.

Msg4 may not be included in the 3-step RA procedure. However, if necessary, the leader can use Msg4 as an optional procedure in AIoT service scenarios. For example, command services such as read, write, or disable may be required after inventory. In such cases, the leader can optionally use Msg4 to facilitate these procedures.

The success or failure of Msg3 can be evaluated differently depending on the use case. In the case of inventory-only use, there is no additional data transmission after Msg3, so the IoT device cannot determine whether the device identifier was successfully transmitted. In the case of inventory and command use, additional commands are transmitted after Msg3, so the IoT device can determine that Msg3 was successfully transmitted upon receiving the command message. In the case of command-only use, since random access is not used, the IoT device may not need to determine whether Msg3 was successfully transmitted.

- Explicit mechanism with response (response message for Msg3 reception): This approach may include defining an Access Stratum (AS)-level message to respond to Msg3 reception. The reader may send an acknowledgment when Msg3 is successfully received. The reader may send a negative acknowledgment when Msg3 is not received. In this approach, the reader may send an ACK when Msg3 is successfully received. If the reader does not receive Msg3, it may send a NACK.

- Explicit retransmission mechanism (retransmission of Msg2): If the leader does not receive Msg3 within a certain amount of time after transmitting Msg2, it can retransmit Msg2. Upon receiving the retransmitted Msg2, the IoT device can retransmit Msg3.

- Implicit Mechanism (Inventory Service Reinitialization): If Msg3 is not received within a specified period after Msg2 is transmitted, the leader can request the IoT device to reinitialize the inventory service via a paging message. In this case, the IoT device can retransmit Msg1 at the leader's request. If the IoT device does not receive the inventory service reinitialization request, the leader can assume that Msg3 was successfully received.

As mentioned earlier, indicating the success or failure of a msg3 transmission to a device can be achieved using different approaches depending on the use case, or a new AS-layer message can be defined that uses a consistent method across use cases. However, because AIoT services typically have limited time constraints and are mostly best-effort, it may be more practical to re-execute the leader's procedure to verify the success of the msg3 transmission rather than defining a specific response message. Therefore, an implicit mechanism, rather than an explicitly defined message, can be used to determine the success of the msg3 transmission.

4-3. Connection method using two-step message exchange

IoT devices can connect to a reader using a two-step message exchange.

Figure 16 is a flowchart illustrating embodiments of a connection method using a two-step message exchange.

Referring to Fig. 16, a connection method using a two-step message exchange may include a resource setting information receiving step (S1601), an IoT device identifier transmitting step (S1602), a response receiving step (S1603), a data transmission/reception step (S1604), etc.

4-3-1-0. Receiving resource configuration information

The step of receiving wireless resource configuration information may be the same as the step of receiving wireless resource configuration information of a connection method using a four-step message exchange.

4-3-1-1. Transmitting the IoT device identifier

The step of transmitting the identifier of an IoT device may be similar to a hybrid form of the procedure of the transmission step of Msg3 (transmitting the identifier and capability information of the IoT device) of the connection method using a three-step message exchange. However, compared to the method of transmitting a random connection signal in the connection method using a three-step message exchange, the IoT device can transmit the identifier of the IoT device in the following manner in the connection method using a two-step message exchange.

1) Method for simultaneously transmitting a random access signal and an IoT device identifier

An IoT device can transmit an on/off-based random access signal from a signal resource of random access resource configuration information, and can transmit an identifier of the IoT device to a leader from an identifier resource of the random access resource configuration information.

2) How to transmit the identifier of an IoT device

IoT devices may not use the signal resource of the random access resource configuration information. IoT devices may transmit their identifiers in the identifier resource of the random access resource configuration information. In this case, the random access resource configuration information may only contain identifier resources.

The identifier of an IoT device can be either a temporary identifier or a unique identifier. A temporary identifier can be a random number, a randomly selected value, etc. A unique identifier is a unique permanent identifier. It can be the entire upper-layer device identifier, a portion of the upper-layer device identifier, etc. A unique permanent identifier can be an electronic product code. A unique identifier can also be used as a temporary identifier.

The IoT device can use a random number as a temporary identifier for Msg1. Alternatively, the IoT device can use the device identifier as a temporary device identifier for Msg1. In the method using a random number, the IoT device can select a random number within a selection range provided by the reader and use it as a temporary identifier. In the method using a random number, the IoT device may require a maximum value of a selection window for selecting a random number. The reader can transmit the maximum value of the selection window to the IoT device. The IoT device can receive the maximum value of the selection window from the reader. Alternatively, the IoT device can use a preset maximum value of the selection window.

In contrast, in a method using device identifiers, IoT devices can utilize the device ID set in the upper layer as the device identifier for Msg1. In this method of using device identifiers, IoT devices can use either the entire device identifier or a portion of the device identifier.

SA2, a technical standardization group of 3GPP responsible for service and system architecture, discussed device identifiers by dividing them into permanent identifiers and temporary identifiers. SA2 discussed the use of long temporary identifiers as suitable identifiers between AIoT controllers and readers, and the use of short temporary identifiers as suitable identifiers between IoT devices and readers. Therefore, IoT devices can generate identifiers included in Msg1 using upper-layer device identifiers. In this case, it may be more appropriate in terms of radio resource consumption and security to generate and transmit a short temporary identifier rather than using a long full device identifier in the IoT device. In addition, when an IoT device generates a temporary identifier, it may also be necessary to configure which form it should be selected from the full device identifier.

The use of random numbers and the use of a portion of the device identifier may be similar. However, as considered in SA2, temporary identifiers can be assigned from the core network through a registration procedure. Therefore, IoT devices can generate device identifiers used in Msg1 of the random access procedure from permanent identifiers. Permanent identifiers can be composed of a mobile carrier identifier, an owner identifier, and an instance identifier. The probability of generating identical identifiers may be higher than that of using random numbers. Therefore, using a random number as the device identifier used in Msg1 may have many advantages over using a portion of the device identifier.

Based on the requirements of the SA1 use case, the inventory service can accommodate a device density of up to 1.5 million devices. However, this represents the maximum number of IoT devices per square kilometer ( ^km2 ) that can be accommodated in an indoor environment, and may not necessarily represent the number of devices that a single reader should accommodate.

However, for example, if a single reader performs inventory services in a space measuring 100 or 200 meters in length and width, simultaneous connections from up to 1,000 or 60,000 IoT devices can be considered. Therefore, considering the reader's service area and the transmission power of IoT devices, the device identifier transmitted in Msg1 should be at least 16 bits.

An IoT device may not receive a response within a set time period after transmitting a random access signal and its identifier. In this case, the IoT device may determine that a random access signal collision has occurred. Alternatively, the IoT device may determine that the reader has not received a random access signal. Alternatively, the IoT device may determine that the reader has not received the IoT device identifier.

IoT devices can check for wireless resources for responses based on a timer. The timer value can be a preset value for the IoT device. Alternatively, the timer value can be a waiting time for a response transmitted from the reader to the IoT device using an R2D frame.

By transmitting a different form of random access signal and waiting for a response after transmitting, the IoT device can identify wireless resources for a response based on the frame. The frame value for waiting for a response can be a value preset for the IoT device. Alternatively, the frame value for waiting for a response can be the waiting time for a response transmitted from the leader to the IoT device using an R2D frame.

An IoT device may not detect a response signal on a wireless resource even after a set time interval has elapsed. In such cases, the IoT device can reset the length of the random access window based on the selection window reset information received from the leader for selecting a random access resource. The IoT device can then select a random number and re-perform the IoT device identifier transmission procedure.

4-3-1-2. Receiving a response from an IoT device

The response reception step of the IoT device may be identical to the procedure of step 4 of the connection method using a 4-step message exchange (i.e., the response reception step for transmission of the identifier and capability information of the IoT device).

4-3-1-3. Data transmission and reception

The data transmission and reception step may be identical to the procedure of step 5 (i.e., the data transmission and reception step) of the connection method using a 4-step message exchange.

Contention may occur between different devices. In such cases, a reconnection mechanism can be used to resolve contention. A transmission set may have only one connection occasion. In this case, the next connection occasion can be specified in a subsequent connection establishment message. However, for transmission sets with multiple connection occasions, a backoff mechanism may be an appropriate reconnection method to reduce the likelihood of contention. For example, a backoff mechanism could expand the selection window size used to generate random numbers for reconnection attempts. Therefore, the leader can provide the device(s) with a connection retry mechanism that can handle contention.

Figure 17 is a flowchart illustrating embodiments of a connection method using a two-step message exchange.

Referring to Fig. 17, a connection method using a two-step message exchange may include a connection setup information transmission step (S1701), an IoT device identifier transmission step (S1702), a response transmission step (S1703), etc.

4-3-2-0. Transmit connection setup information

The leader can generate connection configuration information, including information about the transmission set, information about the resource configuration of the connection occasion, and information about the operational parameters of the random connection. The leader can transmit the generated connection configuration information to the IoT device.

A transmission set can define multiple transmission opportunities. A transmission set can consist of access occasions and R2D/D2R frames. The resource configuration of an access occasion can be radio resource information of the access occasion. The resource configuration of an access occasion can include multiple access occasions in the time, frequency, or code domain. The resource configuration of an access occasion can specify the number of access occasions and resource allocation for each access occasion. The number of access occasions can define the number of opportunities for connection from an IoT device during a specific period. The resource allocation for each access occasion can refer to time, frequency, or code domain resources allocated to each access occasion.

At a recent RAN2 meeting, it was decided to use slotted ALOHA as the basic mechanism for AIoT random access. Therefore, selection window size and backoff-related information may be key parameters for slotted ALOHA and random access. The selection window size can refer to the maximum value at which a random number is generated when an IoT device selects a connection occasion. The selection window size can be similar to the Q parameter in RFID. Backoff-related parameters may consider latency and the backoff window. The latency can refer to the maximum time an IoT device must wait for a response message after transmitting an access signal. The backoff window can describe a mechanism for expanding the selection window size used for random number generation when a collision occurs. This can prevent IoT devices from retransmitting at the same time in subsequent connection attempts.

4-3-2-1. Transmitting the IoT device identifier

In step 4, if the IoT device successfully receives wireless resources from the leader, it can transmit its identifier. In contrast, in step 2, the IoT device can select a connection occasion using random number generation. This can be similar to the "connection signal transmission" in step 1. After selecting a connection occasion, the IoT device can transmit its identifier to the leader using Msg1.

The identifier of an IoT device can be either a temporary identifier or a unique identifier. A temporary identifier can be a random number, a randomly selected value, etc. A unique identifier is a unique permanent identifier. It can be the entire upper-layer device identifier, a portion of the upper-layer device identifier, etc. A unique permanent identifier can be an electronic product code. A unique identifier can also be used as a temporary identifier.

The IoT device can use a random number as a temporary identifier for Msg1. Alternatively, the IoT device can use the device identifier as a temporary device identifier for Msg1. In the method using a random number, the IoT device can select a random number within a selection range provided by the reader and use it as a temporary identifier. In the method using a random number, the IoT device may require a maximum value of a selection window for selecting a random number. The reader can transmit the maximum value of the selection window to the IoT device. The IoT device can receive the maximum value of the selection window from the reader. Alternatively, the IoT device can use a preset maximum value of the selection window.

In contrast, in a method using device identifiers, IoT devices can utilize the device ID set in the upper layer as the device identifier for Msg1. In this method of using device identifiers, IoT devices can use either the entire device identifier or a portion of the device identifier.

SA2, a technical standardization group of 3GPP responsible for service and system architecture, discussed device identifiers by dividing them into permanent identifiers and temporary identifiers. SA2 discussed the use of long temporary identifiers as suitable identifiers between AIoT controllers and readers, and the use of short temporary identifiers as suitable identifiers between IoT devices and readers. Therefore, IoT devices can generate identifiers included in Msg1 using upper-layer device identifiers. In this case, it may be more appropriate in terms of radio resource consumption and security to generate and transmit a short temporary identifier rather than using a long full device identifier in the IoT device. In addition, when an IoT device generates a temporary identifier, it may also be necessary to configure which form it should be selected from the full device identifier.

The use of random numbers and the use of a portion of the device identifier may be similar. However, as considered in SA2, temporary identifiers can be assigned from the core network through a registration procedure. Therefore, IoT devices can generate device identifiers used in Msg1 of the random access procedure from permanent identifiers. Permanent identifiers can be composed of a mobile carrier identifier, an owner identifier, and an instance identifier. The probability of generating identical identifiers may be higher than that of using random numbers. Therefore, using a random number as the device identifier used in Msg1 may have many advantages over using a portion of the device identifier.

Based on the requirements of the SA1 use case, the inventory service can accommodate a device density of up to 1.5 million devices. However, this represents the maximum number of IoT devices per square kilometer (km2) that can be accommodated in an indoor environment, and may not necessarily be the number of devices that a single reader should accommodate.

However, for example, if a single reader performs inventory services in a space measuring 100 or 200 meters in length and width, simultaneous connections from up to 1,000 or 60,000 IoT devices can be considered. Therefore, considering the reader's service area and the transmission power of IoT devices, the device identifier transmitted in Msg1 should be at least 16 bits.

4-3-2-2. Send response

The reader can receive an identifier from the IoT device. Accordingly, the reader can successfully decode the received identifier and confirm the absence of a collision. The reader can transmit an acknowledgment response (i.e., Msg2) containing the identifier of the IoT device received in the previous step to the IoT device. The IoT device can receive the acknowledgment response from the reader. Alternatively, the IoT device cannot receive the acknowledgment response. Then, the IoT device can determine that the collision resolution is not complete. The IoT device can apply a backoff mechanism to perform step 1 (i.e., the identifier transmission step of the IoT device) again.

Contention may occur between different devices. In such cases, a reconnection mechanism can be used to resolve contention. A transmission set may have only one connection occasion. In this case, the next connection occasion can be specified in a subsequent connection establishment message. However, for transmission sets with multiple connection occasions, a backoff mechanism may be an appropriate reconnection method to reduce the likelihood of contention. For example, a backoff mechanism could expand the selection window size used to generate random numbers for reconnection attempts. Therefore, the leader can provide the device(s) with a connection retry mechanism that can handle contention.

The need for Msg2 in a two-step CBRA can consider various approaches depending on the use case.

o Case for inventory only: Since IoT devices do not transmit any additional data after Msg1, Msg2 can be used to check whether the device ID was successfully transmitted in Msg1.

o Cases used in inventory and commands: In such cases, the IoT device can use the additional data received in response to the command to verify the success of the Msg1 transmission. In other words, if the IoT device receives a command after transmitting Msg1, it can assume that Msg1 was successfully transmitted.

o Command-only use case: Random access may not be required because the leader already knows about the existence of the IoT device.

In Phase 2 CBRA, the need for Msg2 may vary depending on the use case. Therefore, IoT devices may apply different mechanisms depending on the use case or define new messages to accommodate these variations. Furthermore, since the device ID and random number are transmitted together, it may be necessary to discuss whether various mechanisms are applied to resolve contention and the mechanism for indicating the success or failure of Msg1 transmission.

A two-step CBRA may involve simultaneously transmitting a random number and a device ID in Msg1. Unlike a three-step CBRA, a two-step CBRA may require specific connection event configuration because the device ID is transmitted in Msg1. Therefore, IoT devices can signal this configuration via a paging message.

In CFRA, since Msg1 must be transmitted without collisions between devices, the reader can specify which device performs the connection for a specific connection occasion. This may mean that the reader must already know the device identifier. The identifier that specifies the device can be either an ID provided by the upper layer or an ID configured at the AS layer. Such an ID configured at the AS layer can be considered equally in all four-step, three-step, two-step, and one-step procedures. Using a higher-layer device ID may be longer and may raise security issues, but it has the advantage of only managing a single ID for the device. On the other hand, using an AS layer device ID requires multiple IDs for the device, but its temporary assignment and shorter ID length may enhance security. The AS layer ID can also be used as a scheduling identifier for control information and data transmission during a specific period. Therefore, the reader can assign a unique AS layer device ID, which can serve as a device identifier for AIoT scheduling.

There are two potential mechanisms for assigning AS layer IDs:

o Leader Assignment (Option 1): During initial connection (receiving MSg1 from inventory), the leader can assign the AS layer ID of the device and transmit it to the device via Msg2.

o Device Random Number Generation (Option 2): The device can generate a random number during initial connection. When the IoT device receives Msg2 containing the same random number sent in Msg1, it can use that random number as its AS layer ID.

In Option 1, the leader can transmit additional information about the AS layer ID to the device. In contrast, in Option 2, the device uses a random number transmitted in Msg1, so Msg2 may not require the additional AS layer ID. Considering the size of the transmitted content, Option 2 may be more advantageous.

4-4. Random access method using one-step message exchange

IoT devices can connect to a leader using a one-step message exchange.

Figure 18 is a flowchart illustrating embodiments of a connection method using a one-step message exchange.

Referring to Fig. 18, a connection method using a one-step message exchange may include a connection setup information receiving step (S1801) and a temporary device identifier transmission step (S1802).

4-4-1-0. Receiving connection setup information via Msg0

Inventory and command services considered in AIoT networks can be procedures initiated by network demands. These services may require wireless resource configurations tailored to network needs. Wireless resources in AIoT networks can be divided into wireless resources for R2D links, which transmit control information and data from the leader to IoT devices, and wireless resources for D2R links, which transmit data from IoT devices to the leader.

An AIoT controller or AF entity can transmit a service request signal to a leader to request a service (S1800). Then, the leader can receive the service request signal from the AIoT controller or AF entity and initiate a service based on the received service request. A unit that performs such a service can be defined as a transmission set. For example, an inventory and command service can be a service that detects the identifiers of surrounding IoT devices and retrieves status information about a specific IoT device. Such an inventory and command service can be configured as a single transmission set.

The leader can transmit resource configuration information for random access to the IoT device for transmitting an R2D frame or a D2R frame through a transmission set (S1801). The resource configuration information for random access may be connection configuration information for random access. Then, the IoT device can receive the resource configuration information for random access from the leader. Through the resource configuration and operation procedures described above, the IoT device may require the following connection configuration information for random access.

- Connection setting information for random access

o Setting up wireless resources for CBRA and CFRA

o Setting up wireless resources for connection occasions

The reader can variably configure the configuration information for random access by considering the density of IoT devices, network load, etc. Therefore, the reader may require a procedure for transmitting message-based configuration information to IoT devices. The reader may include radio resource scheduling information, encryption method, etc. for transmitting Msg1 in the configuration information for random access. The radio resource configuration information of AIoT may consider a new, simple method that considers the capabilities of IoT devices, rather than the DCI-based scheduling considered in the existing NR. For example, resources composed of frequency domain and time domain allocated with a fixed size can be configured as x, y coordinate values in a table format or a linear list. In addition, the x, y coordinate values in a table format or the linear list can be mapped to a device identifier.

4-4-1-1. Sending device identifier via Msg1

The step of transmitting the device identifier via Msg1 may be identical to the three-step procedure of the connection method using a three-step message exchange. In other words, the IoT device can transmit its unique identifier to the reader using the encryption method received from the random access configuration information. The reader receiving this message can determine that the random access procedure is complete and send a service response message to the AIoT controller.

4.5. Integrated random access method

Unified random access can support both contention-based and contention-free random access.

Figure 19 is a flowchart showing embodiments of an integrated random access method.

Referring to FIG. 19, the integrated random access method may include a random access wireless resource allocation information receiving step (i.e., MsgO receiving step) (S1901), a device identifier transmitting step (i.e., Msg1 transmitting step) (S1901), and a device identifier receiving step (i.e., Msg2 receiving step) (S1902).

An AIoT controller or an AF (application function) entity can transmit a service request signal to a leader to request a service (S1900). Then, the leader can receive the service request signal from the AIoT controller or AF entity and initiate a service according to the received service request. The leader can transmit random access wireless resource allocation information including the following information to an IoT device (S1901). The signal transmitting the random access resource allocation information may be Msg0. Msg0 may be included in a paging procedure or a paging message.

- Random access type

- Random access resource configuration information

o Composed of connection rounds and connection opportunities

- Upper layer data

- Device identifier

o No device identifier for inventory

o command has device identifier

An IoT device can receive a signal containing random access wireless resource allocation information from a leader. Based on the received random access wireless resource allocation information, the IoT device can select a connection occasion and then transmit a signal containing a device identifier to the leader (S1902). Through this, the IoT device can notify the network of its presence. The signal containing the device identifier may be Msg1.

Msg1 may contain the following information:

- Device identifier

- Upper layer data

The reader can receive a signal including a device identifier. The reader can recognize the device identifier from the received signal. The reader can successfully decode the device identifier in the corresponding wireless resource. In this case, the signal including the received device identifier can be transmitted to the IoT device (S1903). The signal including the received device identifier may be Msg2. The IoT device can receive Msg2. If the IoT device receives Msg2 including the same identifier as the device identifier transmitted through Msg1, the IoT device can recognize that the collision has been resolved. After transmitting Msg1, the IoT device may not receive an identifier identical to the device identifier transmitted through Msg1. In this case, the IoT device may determine that Msg1 was not transmitted due to a collision or transmission error.

The operations of the method according to the embodiments of the present disclosure can be implemented as a computer-readable program or code on a computer-readable recording medium. A computer-readable recording medium includes any type of recording device that stores information readable by a computer system. Furthermore, a computer-readable recording medium can be distributed across network-connected computer systems, allowing the computer-readable program or code to be stored and executed in a distributed manner.

Additionally, the computer-readable recording medium may include hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, etc. The program instructions may include not only machine language codes produced by a compiler, but also high-level language codes that can be executed by a computer using an interpreter, etc.

While some aspects of the present disclosure have been described in the context of a device, they may also represent a description of a corresponding method, wherein a block or device corresponds to a method step or a feature of a method step. Similarly, aspects described in the context of a method may also be described as a corresponding block or item or a feature of a corresponding device. Some or all of the method steps may be performed by (or using) a hardware device, such as, for example, a microprocessor, a programmable computer, or an electronic circuit. In some embodiments, at least one or more of the most important method steps may be performed by such a device.

In embodiments, a programmable logic device (e.g., a field-programmable gate array) may be used to perform some or all of the functions of the methods described herein. In embodiments, the field-programmable gate array may operate in conjunction with a microprocessor to perform one of the methods described herein. In general, the methods are preferably performed by some hardware device.

Although the present disclosure has been described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various modifications and changes may be made to the present disclosure without departing from the spirit and scope of the present disclosure as set forth in the claims below.

Claims (20)

As a method of the first communication node, A step of receiving resource configuration information for random access from a second communication node; and A step of transmitting the first identifier of the first communication node to the second communication node by utilizing the resource for the random access, Method of the first communication node. In claim 1, The first communication node receives the resource setting information for the random access from the second communication node through a paging message. Method of the first communication node. In claim 1, The first communication node transmits the first identifier or random access signal to the second communication node by utilizing the resources for the random access. Method of the first communication node. In claim 1, The configuration information of the random access resource includes at least one of configuration information of wireless resources for CBRA (contention based random access) and CFRA (contention-free based random access), configuration information of wireless resources for access occasions, configuration information of wireless resources for responding to a random access signal, configuration information for the operation of the first communication node, information on a waiting time for receiving the response, information on a selection window for selecting the access occasions, information on a maximum number of retransmission attempts, or transmission power ramping configuration information. Method of the first communication node. In claim 1, the first identifier is the entirety of the device identifier of the upper layer of the first communication node or a part of the device identifier. Method of the first communication node. In claim 1, The first identifier is a random value selected within the selection range of the first identifier set in the second communication node. Method of the first communication node. In claim 1, A step of receiving a first response signal for transmission of the first identifier from the second communication node; a step of confirming the first identifier in the first response signal; and Further comprising the step of transmitting a second response signal including a second identifier to the second communication node when the first identifier is confirmed in the first response signal. Method of the first communication node. In claim 7 The second identifier is a device identifier of the upper layer of the first communication node. Method of the first communication node. In claim 1, Further comprising a step of determining that reception of the first identifier has failed at the second communication node if the first response signal is not received during the waiting time of the first response signal for transmission of the first identifier from the second communication node. Method of the first communication node. As a method of the second communication node, A step of transmitting configuration information for random access to a first communication node; and A step of receiving a first identifier based on the setting information from the first communication node, Method of the second communication node. In claim 10, a step of transmitting a first response signal including the first identifier to the first communication node; and Further comprising the step of receiving a second identifier from the first communication node, Method of the second communication node. In claim 12, A step of receiving a service request signal from an AIoT (ambient internet of things) controller; and Further comprising a step of transmitting a service response signal including the second identifier to the AIoT controller in response to the service request signal. Method of the second communication node. In claim 10, A step of transmitting a first response signal including the first identifier to the first communication node; A step of waiting for a second response signal to the first response signal from the first communication node for a waiting time; and Further comprising the step of transmitting a signal requesting the second response signal to the first communication node if the second response signal is not received during the waiting time. Method of the second communication node. As the first communication node, Contains at least one processor, The at least one processor is the first communication node, Receive resource configuration information for random access from a second communication node; and Causing the first identifier of the first communication node to be transmitted to the second communication node by utilizing the resources for the above random access, First communication node. In claim 14, The at least one processor causes the first communication node to transmit the first identifier or random access signal to the second communication node by utilizing the resources for the random access. First communication node. In claim 14, The first identifier is the entirety of the device identifier of the upper layer of the first communication node or a part of the device identifier. First communication node. In claim 14, The first identifier is a random value selected within the selection range of the first identifier set in the second communication node. First communication node. In claim 14, The at least one processor is the first communication node, Receive a first response signal to the transmission of the first identifier from the second communication node; Identifying the first identifier in the first response signal; and If the first identifier is confirmed in the first response signal, a second response signal including a second identifier is further caused to be transmitted to the second communication node. First communication node. In claim 17 The second identifier is a device identifier of the upper layer of the first communication node. First communication node. In claim 14, The at least one processor is the first communication node, Further causing the second communication node to determine that reception of the first identifier has failed if the first response signal is not received during the waiting time of the first response signal for transmission of the first identifier from the second communication node. First communication node.