WO2018234851A1

WO2018234851A1 - RANDOM ACCESS PROCEDURE FOR MASSIVE MTC DEVICES

Info

Publication number: WO2018234851A1
Application number: PCT/IB2017/053709
Authority: WO
Inventors: Jagadeesh Arunachalam; Jens JANSSON
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2017-06-21
Filing date: 2017-06-21
Publication date: 2018-12-27
Anticipated expiration: 2019-12-21

Abstract

Systems and methods are disclosed herein that provide efficient transmission of data embedded in the random access procedure even in scenarios where up to many thousands of devices are served by one cell. In some embodiments, a method of operation of a wireless communication device comprises determining a random access preamble pattern, at least a portion of which uniquely identifies the wireless communication device within a given cell as a function of an identity of the wireless communication device. The random access preamble pattern defines a plurality of random access preamble sequences and a plurality of time-frequency resource sets for the plurality of random access preamble sequences, respectively. The method further comprises transmitting the plurality of random access preamble sequences on the plurality of time-frequency resource sets in accordance with the random access preamble pattern. In this manner, efficient transmission of data embedded in the random access procedure is provided.

Description

RANDOM ACCESS PROCEDURE FOR MASSIVE MTC DEVICES

Technical Field

[0001 ] The present disclosure relates to random access.

Background

[0002] Narrowband Internet of Things (NB-loT) is a Third Generation

Partnership Project (3GPP) feature for Machine Type Communication (MTC) devices. NB-loT specifications standardize low data rate devices designed for the Internet of Things (loT). While NB-loT is largely based on legacy Long Term Evolution (LTE) technology, a number of optimizations are needed to support use cases from different verticals for Fifth Generation (5G) networks. The

applications from these verticals are vast and varied. In the loT, the MTC devices, which are also referred to herein as loT or NB-loT devices, are to be used in a variety of applications such as, e.g., smart metering, connected homes, etc.

[0003] Typically, in legacy LTE and NB-loT devices, a random access procedure is used for establishing a Radio Resource Control (RRC) connection and for intra/system handover. In general, the random access procedure includes the following steps. First, the wireless communication device (e.g., the LTE User Equipment device (UE) or the NB-loT device) randomly selects a random access preamble sequence to transmit from a set of available random access preamble sequences for a given cell. The wireless communication device generates the randomly selected random access preamble sequence by applying a respective cyclic shift to a respective Zadoff-Chu root sequence(s). The wireless communication device transmits a random access request including the generated random access preamble sequence on a Physical Random

Access Channel (PRACH) channel. The available random access preambles (i.e., the available Zadoff-Chu root sequence(s) and cyclic shifts) and other information regarding the frequency/time resources for the PRACH are broadcast as part of the system information. The radio access node (i.e., the enhanced or evolved Node B (eNB)) detects the random access preamble sequence transmitted by the wireless communication device and sends a Random Access Response (RAR) to the wireless communication device. The RAR also contains an uplink scheduling grant.

[0004] The random access procedure allows for several wireless

communication devices to access the radio access node simultaneously using the same time and frequency resources (i.e., in the same PRACH occasion). This is achieved by using cyclically shifted Zadoff-Chu sequences as the random access preamble sequences. Random access preamble sequences derived using different cyclic shifts of the same Zadoff-Chu exhibit very good cross- correlation properties and, therefore, allow the radio access node to detect multiple random access preambles in the same PRACH occasion.

[0005] The random access preamble sequence is a Zadoff-Chu sequence generated as a cyclic shift of a Zadoff-Chu root sequence. The Zadoff-Chu root sequence takes the value in the range between 0 and 837. Random access preamble sequences are generated by cyclically shifting a Zadoff-Chu root sequence. Preamble sequences generated from the same Zadoff-Chu root sequence have zero correlation, i.e., they are orthogonal with one another. This means that two or more random access preamble sequences generated using different cyclic shifts of the same Zadoff-Chu root sequence can be transmitted in the same frequency/time resource and the receiver (i.e., the radio access node) will be able to receive and decode all of these random access preamble sequences. Random access preamble sequences generated from different Zadoff-Chu root sequences are not orthogonal.

[0006] Orthogonality is achieved by cyclically shifting the Zadoff-Chu root sequence. The length of the cyclic shift is configured by the network and is a function of cell size. A smaller cyclic shift is suitable for smaller cells (in terms of geographic area covered by the cells). In the 3GPP specifications, the cyclic shifts are referred to as a zero correlation zone and denoted as N_cs.

[0007] In legacy LTE, each cell is allocated a set of 64 random access preamble sequences. Ideally, the random access preamble sequences should be derived from one Zadoff-Chu root sequence. However, due to cell size and in order to avoid false detections, more than one Zadoff-Chu root sequence is needed for generating 64 preamble sequences since the cyclic shift length is more than 1 .

LIE Random Access

[0008] As illustrated in Figure 1 , in 3GPP LTE, the random access procedure is performed after first performing a cell search procedure. More specifically, an eNB broadcasts synchronization signals (i.e., Primary and Secondary

Synchronization Signals (PSS/SSS)) and system information including a number of available Zadoff-Chu root sequences (step 100). A UE performs a cell search procedure whereby the UE synchronizes to the downlink timing of the cell served by the eNB by detecting the PSS/SSS (step 102). The UE then obtains, or reads, the system information (step 104). The system information includes various types of information including information that identifies physical time and frequency resources to be used by the UE for random access as well as available Zadoff-Chu sequences from which random access preamble sequences can be derived.

[0009] With respect to the random access procedure, the UE randomly selects a random access preamble Identifier (ID) and generates a corresponding random access preamble sequence (step 106). The random access preamble sequence is generated from a given Zadoff-Chu root sequence and cyclic shift for the randomly selected random access preamble ID. The UE transmits a random access preamble that comprises a cyclic prefix and the generated random access preamble sequence (step 108). The random access preamble is transmitted on a Random Access Channel (RACH), which is a logical transport channel. The RACH is mapped into a PRACH, which is provided on time and frequency radio resources indicated by the system information broadcast by the eNB. The eNB detects the random access preamble transmitted by the UE and, based on a random access preamble sequence transmitted therein, determines the uplink timing for the UE (step 1 10). The eNB then transmits a Random Access Response (RAR) to the UE including a timing adjustment for the uplink from the UE along with, among other things, an uplink resource grant (step 1 12). The UE adjusts its uplink timing according to the timing adjustment received in the RAR (step 1 14). The UE and the eNB then use RRC signaling to exchange information to complete establishment of the radio link between the eNB and the UE (steps 1 16 through 124).

[0010] As illustrated in Figure 2, the random access preamble, which is also referred herein to as a RACH preamble, includes the random access preamble sequence (also referred to herein as the RACH preamble sequence) having a time duration of T_SEQ, and a Cyclic Prefix (CP) having a time duration of T_Cp. The CP is added to the random access preamble sequence in order to reduce Inter- Symbol Interference ( IS I ) . The random access preamble sequence is a N_Zcr point Zadoff-Chu sequence, wherein N_Zc = 839. N_Zc is the length of the Zadoff- Chu sequence and thus the length of the random access preamble sequence. In 3GPP LTE, cell sizes up to approximately 150 kilometers (km) (radius) are supported. In order to provide this support, the time duration of the random access preamble sequence (T_SEQ) must be significantly greater than the round- trip time for the largest supported cell size. Specifically, 3GPP LTE defines four random access configurations (Configurations 0-3). For each configuration, the random access preamble sequence spans one or more 0.8 millisecond (ms)

(transmission) cycles. The typical random access configuration is Configuration 0. In Configuration 0, the random access preamble sequence is a 0.8 ms sequence and, as such, the random access preamble sequence spans only one 0.8 ms cycle. In particular, in Configuration 0, T_SEQ = 0.8 ms, T_Cp = 0.1 ms, and a guard time (not shown) is also equal to 0.1 ms. Configuration 0 allows for cell sizes (radius) of up to 15 km. In order to support even larger cell sizes (i.e., up to 150 km), Configurations 1 -3 use longer CPs and, in the case of Configurations 2 and 3, longer sequence lengths (i.e., T_SEQ = 1 -6 ms), but over multiple

subframes. For example, in Configuration 2, T_SEQ = 1 -6 ms, T_Cp = 0.2 ms, and the guard time (not shown) is also 0.2 ms. In Configuration 2, the random access preamble sequence (duration of T_SEQ = 1 -6 ms) spans two 0.8 ms cycles. However, each cycle has a duration of 0.8 ms, which corresponds to a subcarrier frequency spacing (Af_PRAcH) for the PRACH subcarriers of 1 .25 kilohertz (kHz) (i.e., Af PRACH = 1/TcYc = 1 /0.8 ms = 1 .25 kHz, where T_CYC is referred to herein as the cycle time).

[001 1 ] The PRACH used to transmit the random access preamble is six Resource Blocks (RBs) in the frequency domain. In the time domain, the

PRACH is either one subframe (1 ms) (Configuration 0), two subframes (2 ms) (Configurations 1 or 2), or three subframes (3 ms) (Configuration 3). Figure 3 illustrates the PRACH for Configuration 0. As illustrated, in order to fit the 0.8 ms random access preamble sequence into six RBs in the frequency domain and provide orthogonality between the PRACH subcarriers, the subcarrier frequency spacing (Af_PRAcH) for the PRACH subcarriers is 1 .25 kHz (i.e., Af_PRAcH = /TCYC = 1/0.8 ms = 1 .25 kHz). Thus, as illustrated, the subcarrier frequency spacing (AfpRACH) for the PRACH subcarriers is 1/12^th of the subcarrier frequency spacing (Af TRAFFIC) for the subcarriers of the other uplink channels (e.g., Physical Uplink Shared Channel (PUSCH)), which is 15 kHz. There are 864 PRACH subcarriers within the six RBs allocated for PRACH. Of these 864 PRACH subcarriers, 839 PRACH subcarriers are used for transmissions of an 839-point Zadoff-Chu sequence.

NB-loT Random Access

[0012] In the current 3GPP specifications, random access for NB-loT follows substantially the same procedure as that for legacy LTE. However, a

Narrowband Physical Random Access Channel (NPRACH) is defined for random access for NB-loT in which the random access preamble consists of a CP and five symbol groups that are transmitted on a single subcarrier in accordance with a defined frequency hopping pattern. Further, the random access preamble may be repeated 1 , 2, 4, 5, 16, 32, 64, or 128 times, depending on the coverage level.

[0013] More specifically, in the uplink, NB-loT applies Single Carrier

Frequency Division Multiple Access (SC-FDMA) with either a 3.75 kHz or 15 kHz subcarrier spacing. The NPRACH uses 3.75 kHz subcarrier spacing. A resource grid for an uplink slot using 3.75 kHz subcarrier spacing is illustrated in Figure 4. As illustrated, in NB-loT, the uplink system bandwidth is 180 kHz. As such, when using 3.75 kHz subcarrier spacing, there are 48 subcarriers in the 180 kHz bandwidth. There are seven Orthogonal Frequency Division Multiplexing

(OFDM) symbols within a slot. According to OFDM principles, the symbol duration for 3.75 kHz subcarrier spacing is approximately 286 microseconds (με), which gives a slot length of 2 ms.

[0014] A random access preamble (also referred to herein as an NPRACH preamble) for NB-loT consists of four symbol groups. Figure 5 illustrates the structure of one symbol group (also referred to herein as preamble symbol group). As illustrated, the symbol group includes a CP having a duration T_Cp followed by five symbols. The five symbols have a duration of TSEQ = 1 -333 ms. The duration of the CP (T_Cp) depends on the format. Currently, two different formats are defined, format 0 and format 1. T_Cp = 67 με for format 0, and T_Cp = 267 με for format 1 . The format to use is broadcast in the system information.

[0015] The NPRACH defines a set of time and frequency resources on which one or more repetitions of the preamble are transmitted. For each repetition, the four symbol groups forming the random access preamble are transmitted without gaps (in time) on different subcarriers in accordance with a defined frequency hopping pattern. Frequency hopping is applied on symbol group granularity. This means that each symbol group is transmitted on a different subcarrier.

While the NPRACH may span a contiguous set of 12, 24, 36, or 48 subcarriers in the frequency domain, the frequency hopping pattern is restricted to a set of 12 continuous subcarriers in the frequency domain.

[0016] NPRACH resources (i.e., the sets of time and frequency resources on which repetitions of preambles can be transmitted) occur periodically. The periodicity is configured by the network and can be between 40 ms and 2.56 seconds. Specifically, the start times of the periodic NPRACH resources are defined in system information, and the end times of the period NPRACH resources are determined by the preamble format and the number of repetitions. [0017] Figure 6 illustrates one example of the transmission of multiple repetitions of an NPRACH preamble. The UE first selects one of the twelve possible subcarriers for transmission of the first symbol group for the first repetition. Alternatively, the eNB may provide an indication of the first subcarrier. Once the subcarrier for the first symbol group is selected, the subcarriers for the second, third, and fourth symbol groups are defined by a frequency hopping pattern that depends only on the first subcarrier. In this example, for the first repetition of the preamble, the first symbol group is transmitted on subcarrier X, then the second symbol group is transmitted on subcarrier X+1 , then the third symbol group is transmitted on subcarrier X+7, and finally the fourth symbol group is transmitted on subcarrier X+6. For the second repetition, a pseudorandom algorithm is used to select the subcarrier for the first symbol group in the second repetition. Once the subcarrier for the first symbol group in the second repetition is selected, then the subcarriers for the second, third, and fourth symbol groups are selected in accordance with a defined frequency hopping pattern that depends only on the subcarrier selected for the first symbol group for the second repetition. The process repeats in this manner until the final repetition is transmitted. Together, the time and frequency resources used for transmission of the multiple repetitions of the preamble form a set of time and frequency resources for transmission of the multiple repetitions of the preamble.

Data Transmission in Massive MTC

[0018] For loT and massive MTC, the number of devices that a base station will need to support is estimated to be up 200,000 devices per cell. A typical characteristic of MTC devices (e.g., sensors and other monitoring devices) is that such devices send small amounts of data (e.g., status/health OK or not OK) to a server once every few minutes. Thus, the payload is small but frequent. For such a scenario, the legacy data transfer procedure is inefficient and sub-optimal.

[0019] For NB-loT devices like sensors where the amount of uplink data is small, the data can be embedded in the random access procedure. For example, U.S. Patent Application Publication No. 2014/0177525 A1 entitled MACHINE TYPE COMMUNICATIONS IN A RADIO NETWORK discloses a mechanism for embedding data in the random access procedure by transmitting multiple random access preambles with frequency offsets at different points in time and/or with different content that define a unique signature for a sensor device. The base station detects the frequency, time, and/or content of the received random access preambles with stored information about pre-configured signatures for different sensor devices to thereby identify a specific sensor device that transmitted the random access preambles. By transmitting the random access preambles in this manner, a specific sensor can utilize the random access procedure to transmit status information to the base station (e.g., transmit the preambles using its frequency, time, and/or content signature to thereby indicate a "status OK" to the base station). However, the frequency offsets, timing, and/or content of the random access preambles that define the unique signature of the sensor are either preconfigured in the sensor upon installation of the sensor or, if the sensor is mobile, explicitly signaled to the sensor from the network. While this may be suitable for tens or hundreds of sensors, it would become highly inefficient and difficult to manage if thousands of sensors were to be served by a single cell.

[0020] Thus, there is a need for systems and methods to efficiently transmit data embedded in the random access procedure where up to many thousands of devices are served by one cell. Further, the end-to-end cost for massive MTC or massive loT applications must be low enough for the business case to make sense. Hence, there is a need to support many MTC or loT connections with a limited amount of network resources and low device complexity.

Summary

[0021 ] Systems and methods are disclosed herein that provide efficient transmission of data embedded in the random access procedure even in scenarios where up to many thousands of devices are served by one cell. In some embodiments, a method of operation of a wireless communication device comprises determining a random access preamble pattern, at least a portion of which uniquely identifies the wireless communication device within a given cell, as a function of an identity of the wireless communication device. The random access preamble pattern defines a plurality of random access preamble sequences and a plurality of time-frequency resource sets for the plurality of random access preamble sequences, respectively. The method further comprises transmitting the plurality of random access preamble sequences on the plurality of time-frequency resource sets in accordance with the random access preamble pattern. In this manner, efficient transmission of data embedded in the random access procedure is provided.

[0022] In some embodiments, at least a portion of the plurality of random access preamble sequences uniquely identifies the wireless communication device within the cell. In some other embodiments, at least a portion of a combination of the plurality of random access preamble sequences and the plurality of time-frequency resource sets uniquely identify the wireless

communication device within the cell.

[0023] In some embodiments, each random access preamble sequence is derived from a respective root sequence and a cyclic shift of the root sequence and, for each random access preamble sequence, the time-frequency resource set defined by the random access preamble pattern for the random access preamble sequence is a time-frequency resource set in which only random access preambles derived from the respective root sequence can be transmitted within the cell such that random access preambles transmitted in the time- frequency resource set are orthogonal.

[0024] In some embodiments, the identity of the wireless communication device is an International Mobile Subscriber Identity (IMSI), an International

Mobile Equipment Identity (IMEI), an Internet Protocol (IP) address, or a Medium Access Control (MAC) address of the wireless communication device.

[0025] In some embodiments, determining the random access preamble pattern comprises determining the random access preamble pattern as a function of the identity of the wireless communication device and user data to be conveyed by transmission of the plurality of random access preamble sequences on the plurality of time-frequency resource sets in accordance with the random access preamble pattern.

[0026] In some embodiments, a length of the random access preamble pattern is dynamic. In some embodiments, a length of the random access preamble pattern is a function of: a distance between the wireless

communication device and a radio access node serving the cell, feedback from the radio access node, a total number of wireless communication devices anchored to the radio access node, one or more parameters indicative of a channel condition for a radio propagation channel between the wireless communication device and the radio access node, user data to be conveyed by transmission of the plurality of random access preamble sequences on the plurality of time-frequency resource sets in accordance with the random access preamble pattern, and/or periodicity at which the wireless communication device desires to convey user data via transmission of random access preamble sequences in accordance with respective random access sequence patterns.

[0027] In some embodiments, the plurality of random access preamble sequences comprise random access preamble sequences derived from two or more different root sequences.

[0028] In some embodiments, each time-frequency resource set of the plurality of time-frequency resource sets is a set of six contiguous physical

Resource Blocks (RBs) in the frequency domain and a defined amount of time in the time domain.

[0029] In some embodiments, each time-frequency resource set of the plurality of time-frequency resource sets is, for each random access preamble sequence of the plurality of random access preamble sequences, time-frequency resources for two or more repetitions of the random access preamble sequence on a plurality of subcarriers in accordance with a respective frequency hopping pattern.

[0030] Embodiments of a wireless communication device for a wireless communication system are also disclosed. In some embodiments, a wireless communication device for a wireless communication system is adapted to determine a random access preamble pattern, at least a portion of which uniquely identifies the wireless communication device within a given cell, as a function of an identity of the wireless communication device. The random access preamble pattern defines a plurality of random access preamble sequences and a plurality of time-frequency resource sets for the plurality of random access preamble sequences, respectively. The wireless communication device is further adapted to transmit the plurality of random access preamble sequences on the plurality of time-frequency resource sets in accordance with the random access preamble pattern.

[0031 ] In some embodiments, the wireless communication device is further adapted to perform the method of any one of the additional embodiments of the method of operation of a wireless communication device disclosed herein.

[0032] In some embodiments, a wireless communication device for a wireless communication system comprises at least one transmitter and circuitry

associated with the at least one transmitter, where the circuitry is operable to determine a random access preamble pattern, at least a portion of which uniquely identifies the wireless communication device within a given cell, as a function of an identity of the wireless communication device. The random access preamble pattern defines a plurality of random access preamble sequences and a plurality of time-frequency resource sets for the plurality of random access preamble sequences, respectively. The circuitry is further operable to transmit the plurality of random access preamble sequences on the plurality of time- frequency resource sets in accordance with the random access preamble pattern.

[0033] In some embodiments, a wireless communication device for a wireless communication system comprises a determining module and a transmitting module. The determining module is operable to determine a random access preamble pattern, at least a portion of which uniquely identifies the wireless communication device within a given cell, as a function of an identity of the wireless communication device. The random access preamble pattern defines a plurality of random access preamble sequences and a plurality of time-frequency resource sets for the plurality of random access preamble sequences, respectively. The transmitting module is operable to transmit the plurality of random access preamble sequences on the plurality of time-frequency resource sets in accordance with the random access preamble pattern.

[0034] Embodiments of a computer program are also disclosed in which the computer program comprises instructions which, when executed on at least one processor, cause the at least one processor to carry out the method of operation of a wireless communication device according to any one of the embodiments disclosed herein. Embodiments of a carrier containing the aforementioned computer program are also disclosed in which the carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium.

[0035] Embodiments of a method of operation of a radio access node in a wireless communication system are also disclosed. In some embodiments, a method of operation of a radio access node in a wireless communication system comprises detecting a plurality of random access preamble sequences transmitted by a wireless communication device on a plurality of time-frequency resource sets, respectively, in accordance with a random access preamble pattern and decoding an identity of the wireless communication device based on the random access preamble pattern. The random access preamble pattern is a function of the identity of a wireless communication device, and at least a portion of the random access preamble pattern uniquely identifies the wireless communication device within a cell served by the radio access node.

[0036] In some embodiments, at least a portion of the plurality of random access preamble sequences uniquely identifies the wireless communication device within the cell. In some other embodiments, at least a portion of a combination of the plurality of random access preamble sequences and the plurality of time-frequency resource sets uniquely identify the wireless

communication device within the cell.

[0037] In some embodiments, each random access preamble sequence is derived from a respective root sequence and, for each random access preamble sequence, the time-frequency resource set defined by the random access preamble pattern for the random access preamble sequence is a time-frequency resource set in which only random access preambles derived from the respective root sequence can be transmitted within the cell.

[0038] In some embodiments, the identity of the wireless communication device is an IMSI, an IMEI, an IP address, or a MAC address of the wireless communication device.

[0039] In some embodiments, the random access preamble pattern is a function of the identity of the wireless communication device and user data to be conveyed by the wireless communication device by transmission of the plurality of random access preamble sequences on the plurality of time-frequency resource sets in accordance with the random access preamble pattern.

[0040] In some embodiments, a length of the random access preamble pattern is dynamic. In some embodiments, a length of the random access preamble pattern is a function of a distance between the wireless communication device and the radio access node serving the cell, feedback provided to the wireless communication device by the radio access node, a total number of wireless communication devices anchored to the radio access node, one or more parameters indicative of a channel condition for a radio propagation channel between the wireless communication device and the radio access node, user data to be conveyed by the wireless communication device by transmission of the plurality of random access preamble sequences on the plurality of time- frequency resource sets in accordance with the random access preamble pattern, and/or periodicity at which the wireless communication device desires to convey user data via transmission of random access preamble sequences in accordance with respective random access sequence patterns.

[0041] In some embodiments, the plurality of random access preamble sequences comprise random access preamble sequences derived from two or more different root sequences.

[0042] In some embodiments, each time-frequency resource set of the plurality of time-frequency resource sets is a set of six contiguous physical RBs in the frequency domain and a defined amount of time in the time domain. [0043] In some embodiments, each time-frequency resource set of the plurality of time-frequency resource sets is, for each random access preamble sequence of the plurality of random access preamble sequences, time-frequency resources for two or more repetitions of the random access preamble sequence on a plurality of subcarriers in accordance with a respective frequency hopping pattern.

[0044] Embodiments of a radio access node for a wireless communication system are also disclosed. In some embodiments, a radio access node for a wireless communication system is adapted to detect a plurality of random access preamble sequences transmitted by a wireless communication device on a plurality of time-frequency resource sets, respectively, in accordance with a random access preamble pattern and decode an identity of a wireless

communication device based on the random access preamble pattern. The random access preamble pattern is a function of the identity of the wireless communication device, and at least a portion of the random access preamble pattern uniquely identifies the wireless communication device within a cell served by the radio access node.

[0045] In some embodiments, the radio access node is further adapted to perform the method of operation of a radio access node according to any additional one of the embodiments disclosed herein.

[0046] In some embodiments, a radio access node for a wireless

communication system comprises at least one receiver and circuitry associated with the at least one receiver operable to detect a plurality of random access preamble sequences transmitted by a wireless communication device on a plurality of time-frequency resource sets, respectively, in accordance with a random access preamble pattern and decode an identity of the wireless communication device based on the random access preamble pattern. The random access preamble pattern is a function of the identity of the wireless communication device, and at least a portion of the random access preamble pattern uniquely identifies the wireless communication device within a cell served by the radio access node. [0047] In some embodiments, a radio access node for a wireless

communication system comprises a detecting module and a decoding module. The detecting module is operable to detect a plurality of random access preamble sequences transmitted by a wireless communication device on a plurality of time-frequency resource sets, respectively, in accordance with a random access preamble pattern. The decoding module is operable to decode an identity of the wireless communication device based on the random access preamble pattern. The random access preamble pattern is a function of the identity of the wireless communication device, and at least a portion of the random access preamble pattern uniquely identifies the wireless communication device within a cell served by the radio access node.

[0048] Embodiments of a computer program are also disclosed in which the computer program comprises instructions which, when executed on at least one processor, cause the at least one processor to carry out the method of operation of a radio access node according to any one of the embodiments disclosed herein. Embodiments of a carrier containing the aforementioned computer program are also disclosed in which the carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium.

[0049] Those skilled in the art will appreciate the scope of the present disclosure and realize additional aspects thereof after reading the following detailed description of the embodiments in association with the accompanying drawing figures.

Brief Description of the Drawings

[0050] The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure.

[0051] Figure 1 illustrates the conventional Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) random access procedure;

[0052] Figure 2 illustrates the conventional random access preamble for 3GPP LTE; [0053] Figure 3 illustrates the Physical Random Access Channel (PRACH) for Configuration 0 in 3GPP LTE;

[0054] Figure 4 illustrates a resource grid for uplink using 3.75 kilohertz (kHz) subcarrier spacing for Narrowband Internet of Things (NB-loT);

[0055] Figure 5 illustrates the structure of one symbol group for the random access preamble in NB-loT;

[0056] Figure 6 illustrates one example of the transmission of multiple repetitions of a Narrowband Physical Random Access Channel (NPRACH) preamble in NB-loT;

[0057] Figure 7 illustrates one example of a wireless communication system in which embodiments of the present disclosure may be implemented;

[0058] Figure 8 illustrates the operation of a radio access node and a wireless communication device according to some embodiments of the present disclosure;

[0059] Figure 9 illustrates one example of determining the random access preamble pattern in the process of Figure 8;

[0060] Figure 10 illustrates one example of sets of random access preamble sequences that uniquely identify six different wireless communication devices according to some embodiments of the present disclosure;

[0061 ] Figure 1 1 illustrates one example of a random access preamble pattern that uniquely identifies a wireless communication device within a cell according to some other embodiments of the present disclosure;

[0062] Figure 12 is a flow chart that illustrates the operation of a wireless communication device according to some embodiments of the present disclosure;

[0063] Figure 13 illustrates the operation of a radio access node according to some embodiments of the present disclosure;

[0064] Figures 14 and 15 illustrate example embodiments of a wireless communication device; and

[0065] Figures 16 through 18 illustrate example embodiments of a network node. Detailed Description

[0066] The embodiments set forth below represent information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims.

[0067] Radio Node: As used herein, a "radio node" is either a radio access node or a wireless communication device.

[0068] Radio Access Node: As used herein, a "radio access node" or "radio network node" is any node in a radio access network of a wireless (e.g., cellular) communications network that operates to wirelessly transmit and/or receive signals. Some examples of a radio access node include, but are not limited to, a base station (e.g., a New Radio (NR) base station (gNB) in a Third Generation Partnership Project (3GPP) Fifth Generation (5G) NR network or an enhanced or evolved Node B (eNB) in a 3GPP Long Term Evolution (LTE) network), a high- power or macro base station, a low-power base station (e.g., a micro base station, a pico base station, a home eNB, or the like), and a relay node.

[0069] Core Network Node: As used herein, a "core network node" is any type of node in a core network. Some examples of a core network node include, e.g., a Mobility Management Entity (MME), a Packet Data Network Gateway (P- GW), a Service Capability Exposure Function (SCEF), or the like.

[0070] Wireless communication device: As used herein, a "wireless communication device" is any type of device that has access to (i.e., is served by) a wireless (e.g., cellular) communications network by wirelessly transmitting and/or receiving signals to a radio access node(s). Some examples of a wireless communication device include, but are not limited to, a User Equipment device (UE) in a 3GPP network, a Machine Type Communication (MTC) device, and an Internet of Things (loT) device. [0071 ] Network Node: As used herein, a "network node" is any node that is either part of the radio access network or the core network of a wireless (e.g., cellular) communications network/system.

[0072] Random Access Preamble Pattern: As used herein a random access preamble pattern defines: (a) a set of random access preamble sequences {SEQ^ SEQ₂, SEQ_Lp} where l__p is a length of the random access preamble pattern and (b) sets of time-frequency resources for the random access preamble sequences, respectively.

[0073] Random Access Preamble Sequence: As used herein, a random access preamble sequence is a Zadoff-Chu or similar sequence corresponding to a root sequence (R) and a cyclic shift (C). The root sequence (R) is also referred to herein as a Random Access Channel (RACH) root sequence. As such, a random access preamble sequence is sometimes denoted herein as (R,C).

Random access preamble sequences having the same root sequence but different cyclic shifts are orthogonal to one another.

[0074] Set of Time-Frequency Resources or Time-Frequency Resource Set: As used herein, a set of time-frequency resources or a time-frequency resource set is a set of time-frequency resources on which a random access preamble sequence (e.g., as in LTE) or a number of repetitions of a random access preamble sequence (e.g., as in random access in Narrowband Internet of Things (NB-loT)) is/are transmitted. As an example, for LTE, the time-frequency resource set on which a random access preamble sequence is transmitted is a set of six physical Resource Blocks (RBs) in the frequency domain and, typically, 1 millisecond (ms) in the time domain. As another example, for NB-loT, the time- frequency resource set on which a random access preamble sequence is transmitted includes, for each random access preamble sequence in the random access preamble pattern, time-frequency resources for two or more repetitions of the random access preamble sequence on a number of subcarriers (e.g., some subset of twelve continuous (in the frequency domain) subcarriers in the current specifications for NB-loT) in accordance with a respective frequency hopping pattern (i.e., each repetition has its own frequency hopping pattern). [0075] Note that the description given herein focuses on a 3GPP cellular communications system and, as such, 3GPP terminology or terminology similar to 3GPP terminology is oftentimes used. However, the concepts disclosed herein are not limited to a 3GPP system.

[0076] Note that, in the description herein, reference may be made to the term "cell;" however, particularly with respect to 5G NR concepts, beams may be used instead of cells and, as such, it is important to note that the concepts described herein are equally applicable to both cells and beams.

[0077] Systems and methods are disclosed herein that provide efficient transmission of data embedded in the random access procedure even in scenarios where up to many thousands of devices are served by one cell.

Further, the systems and methods disclosed herein provide support for connections to many wireless communication devices (e.g., MTC or loT devices) with a limited amount of network resources and low device complexity.

[0078] In general, each wireless communication device is allocated a random access preamble pattern. The random access preamble pattern uniquely identifies a device. The random access preamble pattern is a set of random access preamble pattern preamble sequences that are transmitted in specific positions in a resource grid, i.e., transmitted in respective sets of time-frequency resources. The random access preamble pattern, specifically the set of random access preamble sequences and/or the sets of time-frequency resources on which the set of random access preamble sequences is to be transmitted, is a function of an identity of the wireless communication device (e.g., subscriber identity such as International Mobile Equipment Identity (IMEI), International Mobile Subscriber Identity (IMSI), or the like). Further, in some embodiments, the random access preamble pattern is further a function of available RACH root sequences and cyclic shifts.

[0079] The random access preamble pattern is transmitted by the wireless communication device. Transmission of the random access preamble pattern conveys information to the radio access node. For example, in some

embodiments, transmission of the random access preamble sequence by the wireless communication device is used to covey a status of the wireless communication device (e.g., transmission of the random access preamble pattern conveys information that the wireless communication device is "OK"). Thus, if the random access preamble pattern is successfully received by the radio access node, then the corresponding data has been conveyed to the radio access node (e.g., successful reception of the random access preamble pattern by the radio access node is interpreted by the radio access node to mean that the wireless communication device is "OK"). Different and extended patterns can be used to convey different information as well. For example, the wireless communication device may transmit one random access preamble pattern to indicate that it is "OK" and a different random access preamble pattern to indicate that it is "Not OK."

[0080] In some embodiments, the preamble sequences belonging to the wireless communication device are spread across the entire time-frequency resource grid and sent on the Physical Random Access Channel (PRACH) channel.

[0081 ] In some embodiments, the random access preamble pattern transmitted by the wireless communication device is chosen such that orthogonality is maintained when multiple wireless communication devices transmit their random access preamble pattern in the same time-frequency resources.

[0082] In some embodiments, the length of the random access preamble pattern is dynamic and is based on one or more parameters such as, but not limited to:

· distance between the wireless communication device and the radio access node, where the distance can be indicated by any suitable parameter such as, e.g., a Reference Signal Received Quality (RSRQ) measurement performed by the wireless communication device with respect to the radio access node; • feedback from the radio access node (e.g., Acknowledgements (ACKs) sent to the wireless communication device from the radio access node);

• total number of wireless communication devices anchored by the radio access node which is, e.g., provided by the radio access node to the wireless communication device as a semi-static input to the pattern selection/determination algorithm at the wireless communication device (e.g., provided in an Over-The-Air (OTA) message or system information);

· channel conditions; and/or

• information to be conveyed by the transmission of the random

access preamble pattern.

With regard to feedback from the radio access node, if the radio access node is able to successfully receive and decode the pattern to identify the wireless communication device, the radio access node sends a signal (e.g., a RAR) to acknowledge receipt of the pattern. If the radio access node is not able to identify the wireless communication device, then no acknowledgement is received by the wireless communication device and, as such, the wireless communication device may add more redundancy by, e.g., increasing the length of the pattern. This redundancy is different from the coverage enhancement level in NB-loT. Note that the length of the random access preamble pattern may be dynamically determined by the wireless communication device based on, e.g. any one or more of the aforementioned parameters or determined by the radio access node and indicated in, e.g., system information.

[0083] The random access preamble pattern for one wireless communication device is constructed such that the random access preamble pattern includes random access preamble sequences derived from different RACH root sequences. The random access preamble sequences for the random access preamble patterns transmitted by two or more wireless communication devices in any subframe are orthogonal to one other. That is, in some embodiments, the random access preamble sequences sent from two or more wireless communication devices on the same time/frequency resources are Zadoff-Chu sequences derived from the same RACH root sequence but with different cyclic shifts.

[0084] Figure 7 illustrates one example of a wireless communication system 10 in which embodiments of the present disclosure may be implemented. The wireless communication system 10 preferably supports NB-loT, but is not limited thereto. As illustrated, the wireless communication system 10 includes a number of wireless communication devices 12, some of which are MTC devices or loT devices. In addition, the wireless communication system 10 includes a radio access network that includes a number of radio access nodes 14 (e.g., eNBs) serving corresponding cells 16. The radio access nodes 14 are connected to a core network 18, which includes a number of core network nodes, as will be appreciated by one of skill in the art.

[0085] Figure 8 illustrates the operation of a radio access node 14 and a wireless communication device 12 according to some embodiments of the present disclosure. Optional steps are indicated by dashed lines. As illustrated, the radio access node 14 optionally transmits system information including an indication of one or more RACH root sequences available in the corresponding cell 16 and an indication of time-frequency resource sets available for random access preamble transmission in the cell 16 (step 200). In addition or

alternatively, the radio access node 14 may provide additional or alternative information to seed the algorithm used by the wireless communication device 12 to determine its random access preamble pattern. This information may include, for example, the total number of wireless communication devices 12 anchored to the radio access node 14, information regarding the channel conditions, type of wireless communication device 12 (e.g., type of MTC device), timeout for the wireless communication device 12 in embodiments in which the wireless communication device 12 is a MTC device such as a Sensor device, or the like. Optionally, the wireless communication device 12 decodes the system

information and extracts the set of available RACH root sequences and the set of available time-frequency resource sets for random access preamble transmission (step 202).

[0086] The wireless communication device 12 determines a random access preamble pattern that uniquely identifies the wireless communication device 12 (e.g., within the cell 16) as a function of an identity (e.g., IMSI, IMEI, Internet Protocol (IP) address, Medium Access Control (MAC) address, or the like) of the wireless communication device 12 (step 204). The identity can be any type of identity. In general, the identity length (i.e., the length of the value used as the identity of the wireless communication device 12) needs to be large enough to support the number of wireless communication devices 12. The set of random access preamble sequences in the pattern includes multiple random access preamble sequences derived from two or more different RACH root sequences.

[0087] As stated above, the random access preamble pattern uniquely identifies the wireless communication device 12. In general, the random access sequence pattern includes three parameters, namely, (1 ) a set of RACH root sequences, (2) a set of cyclic shifts applied to the set of RACH root sequences to thereby provide the set of random access preamble sequences for the pattern, and (3) the sets of time-frequency resources to be used for transmission of the random access preamble sequences. In some embodiments, one of these parameters (e.g., the set of RACH root sequences) is used to uniquely identify the wireless communication device 12. For example, the set of RACH root sequences uniquely identifies the wireless communication device 12 and, e.g., the cyclic shifts are randomly selected, selected based on distance between the wireless communication device 12 and the radio access node 14, selected based on RSRP for the respective cell, or the like. In some other embodiments, a combination of two or more of these parameters is used to uniquely identify the wireless communication device 12. As an example, in some embodiments, the set of random access preamble sequences (i.e., the combination of the set of RACH root sequences and the respective cyclic shifts) uniquely identify the wireless communication device 12. As another example, in some embodiments, the combination of the set of random access preamble sequences (i.e., the combination of the set of RACH root sequences and the respective cyclic shifts) together with the respective sets of time-frequency resources uniquely identify the wireless communication device 12.

[0088] As an example, in some embodiments, the random access preamble pattern is generated using a pseudo-random number generator that generates a pseudo random number that is indicative of (e.g., has a pre-defined mapping to) a unique random access preamble pattern. The identity of the wireless communication device 12 and, in some embodiments, one or more other parameters (e.g., the set of available RACH root sequences in the cell 16, the sets of available time-frequency resources for random access preamble sequence transmission in the cell 16, information to be conveyed by the transmission of the random access preamble pattern by the wireless

communication device 12, and/or periodicity/sensor expiration timer) is/are the seed to the pseudo-random number generator. The generated number/pattern is deterministic and it follows certain constraint(s), namely, a pattern is unique, i.e., given a seed, the pattern should be generatable and vice-versa and, optionally, one or more other constraints such as, e.g., ensuring orthogonality, dynamic length, etc. Note that a pseudo-random number generator is only an example. Any suitable mechanism can be used to generate the random access preamble pattern based on the identity of the wireless communication device 12 and, optionally, one or more additional parameters.

[0089] In some embodiments, the random access preamble pattern as a whole (e.g., the full set of random access preamble sequences) uniquely identifies the wireless communication device 12. In some other embodiments, a portion of the random access preamble pattern (e.g., a subset of the full set of random access preamble sequences in the pattern) uniquely identifies the wireless communication device 12. As an example, in a tree deployment (MTC devices deployed in a hierarchical fashion), there are root nodes and leaf nodes. The first part of the root sequence pattern uniquely identifies the root MTC device and the later part of the sequence identifies the child node anchored within the root node. [0090] The random access preamble pattern may also be a function of one or more other parameters such as, e.g., the set of available RACH root sequences in the cell 16, the sets of available time-frequency resources for random access preamble sequence transmission in the cell 16, information to be conveyed by the transmission of the random access preamble pattern by the wireless communication device 12, and/or periodicity/sensor expiration timer. In this manner, the random access preamble pattern can be dynamic. Note that the periodicity/sensor expiration timer is a timer used to trigger wake-up of the wireless communication device 12 for transmission and/or reception of data (e.g., wake-up to transmit a status signal). The periodicity/sensor expiration timer corresponds to the type and/or criticality of the wireless communication device 12 (e.g., a critical MTC device may have a much shorter expiration timer than a non- critical MTC device).

[0091 ] Further, in some embodiments, the length of the random access preamble pattern is dynamic. For example, the length of the random access preamble pattern (i.e., the number of random access preamble sequences in the pattern) can be a function of one or more parameters such as, but not limited to, total number of wireless communication devices 12 anchored by the radio access node 14, channel conditions, information to be conveyed by the transmission of the random access preamble pattern, and/or periodicity/sensor expiration timer.

[0092] In some embodiments, redundancies may be introduced into the random access preamble pattern in order to, e.g., increase the likelihood of successfully receiving the pattern at the radio access node 14.

[0093] There is a one-to-one or one-to-many mapping between the identity of the wireless communication device 12 and the random access preamble pattern. Specifically, there is a one-to-one mapping when the random access preamble pattern is a function of only the identity of the wireless communication device 12. There is a one-to-many mapping when the random access preamble pattern is a function of the identity of the wireless communication device 12 and one or more additional parameters (i.e., the same identity may map to any one of multiple different random access preamble patterns depending on the one or more additional parameters). However, within the cell 16, no two identities map to the same random access preamble pattern.

[0094] Notably, the determined random access preamble pattern is known by the radio access node 14. In other words, the radio access node 14 is able to determine the random access preamble pattern allocated for the wireless communication device 12 based on the identity of the wireless communication device 12 and, optionally, one or more additional parameters such as, e.g., the set of available RACH root sequences in the cell 16, the sets of available time- frequency resources for random access preamble sequence transmission in the cell 16, and/or information to be conveyed by the transmission of the random access preamble pattern by the wireless communication device 12.

[0095] The wireless communication device 12 generates and transmits the random access preamble pattern determined in step 204 (step 206). More specifically, the wireless communication device 12 generates and transmits the set of random access preamble sequences on the respective sets of time and frequency resources as defined by the random access preamble pattern. While not illustrated, for each random access preamble sequence in the pattern, the wireless communication device 12 may more specifically generate and transmit a corresponding random access preamble that includes a Cyclic Prefix (CP) and the random access preamble sequence, as will be appreciated by one of skill in the art.

[0096] At the radio access node 14, the radio access node 14 detects the random access preamble pattern (step 208) and decodes the identity of the wireless communication device 12 and, optionally, information conveyed by the transmission of the random access preamble pattern based on the detected random access preamble pattern (step 210). The radio access node 14 may optionally take one or more actions upon detecting the random access preamble pattern and decoding the identity of the wireless communication device 12 (step 212). The one or more actions may include, e.g., storing user data conveyed by the transmission of the random access preamble pattern and/or communicating the user data conveyed by the transmission of the random access preamble pattern to another network node or application server (e.g., an loT server).

[0097] Figure 9 illustrates one example of determining the random access preamble pattern in step 204 of Figure 8. As illustrated, the wireless

communication device 12 determines a set of random access preamble sequences based on the identity of the wireless communication device 12. In this example, the available set of RACH root sequences includes RACH root sequences Ri to R_N where in this example N > 9, and the available cyclic shifts include cyclic shifts Ci to C_M, wherein M > 2. The set of random access preamble sequences that uniquely identify the wireless communication device 12 are, in this example, {P(Ri ,Ci), P(R₃,Ci), P(R₅,Ci), P(R₇,Ci)}, where P(R_X, C_y) is, in this example, a Zadoff-Chu sequence derived by applying cyclic shift C_y to RACH root sequence R_x. Note that Zadoff-Chu is only one example. Other types of sequences may be used.

[0098] Further, in this example, there are a number of random access occasions (as represented by the boxes along the time axis) that include a number of available random access time-frequency resource sets, respectively. The random access occasions may, in the time domain, correspond to

subframes. For 3GPP LTE, a time-frequency resource set on which a random access preamble sequence is transmitted in a set of six physical RBs in the frequency domain and, typically, 1 ms in the time domain. For NB-loT, a time- frequency resource set on which a random access preamble sequence is transmitted includes, for each random access preamble sequence in the random access preamble pattern, time-frequency resources for two or more repetitions of the random access preamble sequence on a number of subcarriers (e.g., some subset of twelve continuous (in the frequency domain) subcarriers in the current specifications for NB-loT) in accordance with a respective frequency hopping pattern (i.e., each repetition has its own frequency hopping pattern). Further, in order to provide orthogonality, each random access time-frequency resource set is constrained to random access preamble sequences derived from the same RACH root sequence. As illustrated in Figure 9, some of the random access time-frequency resource sets are constrained to RACH root sequence Ri , others of the random access time-frequency resource sets are constrained to RACH root sequence R₂, and so on. Therefore, the wireless communication device 12 determines the sets of random access time-frequency resource sets by mapping the set of random access preamble sequences {P(Ri ,Ci), P(R₃,Ci), P(R₅,Ci), P(R_7JCI)} to appropriate time-frequency resource sets. Thus, the random access preamble sequence P(Ri , Ci) is mapped to a random access time-frequency resource set constrained to RACH root sequence R^ the random access preamble sequence P(R₃, C^ is mapped to a random access time-frequency resource set constrained to RACH root sequence R₃, and so on. The set of random access preamble sequences {P(Ri ,Ci), P(R₃,Ci), P(R₅,Ci), P(R₇,Ci)} and the respective sets of random access time-frequency resources to which the random access preamble sequences P(Ri ,Ci), P(R₃,Ci), P(R₅,Ci), and P(R₇,Ci) are mapped form the random access preamble pattern.

[0099] Figure 1 0 illustrates one example of sets of random access preamble sequences that uniquely identify six different wireless communication devices 12 {\NDi through WD₆). The sets of random access preamble sequences are mapped to random access time-frequency request sets as described above with respect to Figure 9. Note that since the random access preamble sequences in the sets for WDi , WD₂, and WD₃ use the same sequence of RACH root sequences (i.e., Ri , R₃, R₅, and R₇), then these sets of random access preamble sequences can be mapped to the same sets of random access time-frequency resources. Likewise, since the random access preamble sequences in the sets for WD₄, WD₅, and WD₆ use the same sequence of RACH root sequences (i.e., R₂, R₄, R6, and R₈), then these sets of random access preamble sequences can be mapped to the same sets of random access time-frequency resources.

[0100] As an example, in some embodiments, the random access time- frequency resources are constrained to RACH root sequences in accordance with the following:

R = SFNmodX where R is the RACH root sequence to be used for the given subframe in which a particular random access time-frequency resource is located (i.e., for a particular random access occasion), SFN is the subframe number for the given subframe, and X is a RACH root sequence reuse coefficient, which could, for example, be scaled based on an expiration timer of the wireless communication device 12 (e.g., where the wireless communication device 12 is an MTC or loT device that periodically wakes up upon expiration of the expiration timer).

[0101 ] As illustrated in the example of Figure 10, the random access preamble patterns can be chosen such that the number of wireless

communication devices (i.e., users) at one time and frequency can be

maximized. For example, by only allowing wireless communication devices with R1 to transmit in one set of time-frequency resources together with generating different cyclic shifts C, allows more wireless communication devices utilizing orthogonality.

[0102] The robustness is increased if the sequences are spread in bandwidth, i.e. a first sequence in the pattern is transmitted in one set of frequency resources and a second sequence in the pattern is transmitted in another set of frequency resources. By doing this, frequency selective fading is circumvented.

[0103] In the example of Figures 9 and 10, at any given time, at most one random access time-frequency resource is available in the cell 16. However, the present disclosure is not limited thereto. Additional random access time- frequency resources may be available on different frequency resources. Using 3GPP LTE as an example, one random access time-frequency resource may use a first set of six physical RBs in the frequency domain and another random access time-frequency resource may use a second set of six physical RBs, where there is no overlap between these two sets of physical RBs (i.e., the intersection is null). These two sets of physical RBs may partially or completely overlap in the time domain. In this manner, at any given time, there may be more than one available random access time-frequency resource, where each is preferably constrained to a respective RACH root sequence to provide

orthogonality when multiple wireless communication devices 12 transmit random access preamble sequences using the same random access time-frequency resource.

[0104] Figure 1 1 illustrates one example of a random access preamble pattern that uniquely identifies a wireless communication device 12 within a cell 16 according to some other embodiments of the present disclosure. This example is particularly directed to an NB-loT embodiment, but may also be used for other similar technologies. For NB-loT, as described above with respect to Figures 4-6, a number of repetitions of the random access preamble are transmitted. Each repetition includes the transmission of four symbol groups on different subcarriers as defined by a frequency hopping pattern. The aggregate of the frequency hopping patterns across all repetitions is referred to here as an aggregate frequency hopping pattern.

[0105] In Figure 1 1 , each box in the time-frequency grid represents multiple random access time-frequency resource sets that use different, non-overlapping aggregate frequency hopping patterns. Specifically, each box in the time- frequency grid represents a random access occasion that includes multiple random access time-frequency resource sets. Briefly looking back at Figure 6, one aggregate frequency hopping pattern is shown. However, multiple different, non-overlapping aggregate frequency hopping patterns can be defined within the same time-frequency resource grid. Returning to Figure 1 1 , each box in the time-frequency resource grid includes, in this example, N random access time- frequency resource sets each having a different, non-overlapping aggregate frequency hopping pattern and each being constrained to a different RACH root sequence. For example, one random access time-frequency resource set is defined by aggregate frequency hopping pattern (AGGR FH PAT. 1 ) and constrained to RACH root sequence Ri , another random access time-frequency resource set is defined by aggregate frequency pattern (AGGR FH PAT. 2) and constrained to RACH root sequence R₂, and so on.

[0106] In the illustrated example, the random access preamble pattern that uniquely identifies the wireless communication device 12 includes the set of random access preamble sequences {P(Ri ,Ci), P(R₃,Ci), P(R₅,Ci), P(R₇,Ci)}. The wireless communication device 12 determines the sets of random access time-frequency resource sets by mapping the set of random access preamble sequences {PiR^d), P(R₃,Ci), P(R₅,Ci), P(R₇,Ci)} to appropriate time-frequency resource sets. Thus, the random access preamble sequence P(Ri , Ci) is mapped to a random access time-frequency resource set constrained to RACH root sequence Ri , the random access preamble sequence P(R₃, Ci) is mapped to a random access time-frequency resource set constrained to RACH root sequence R₃, and so on. The set of random access preamble sequences {P(Ri ,Ci), P(R₃,Ci), P(R₅,Ci), P(R₇,Ci)} and the respective sets of random access time-frequency resources to which the random access preamble sequences P(Ri ,Ci), P(R₃,Ci), P(R₅,Ci), and P(R₇,Ci) are mapped form the random access preamble pattern. Note that, in this illustrated example, the random access preamble sequences P(Ri ,Ci), P(R₃,Ci), P(R₅,Ci), and P(R₇,Ci) are mapped to random access time-frequency resource sets that occur at different times. However, this embodiment is not limited thereto. For example, all four of the random access preamble sequences P(Ri ,Ci), P(R₃,Ci), P(R₅,Ci), and P(R₇,Ci) may be mapped to the random access time-frequency resource sets that occur during the same time period (i.e., occur during the same time period but use different aggregate frequency hopping patterns).

[0107] Figure 12 is a flow chart that illustrates the operation of a wireless communication device 12 according to some embodiments of the present disclosure. This process is substantially the same as that described above with respect to Figure 8. As such, not all details will be repeated. Optional steps are represented by dashed boxes. As illustrated, the wireless communication device 12 optionally obtains inputs for a random access preamble sequence

determination procedure to be performed by the wireless communication device 12 (step 300). These inputs may be obtained by receiving and decoding system information for the cell 16 and/or by receiving information via OTA signaling, or the like. For example, in some embodiments, the inputs for the procedure include, e.g., the RACH root sequences that are available and the time-frequency resource sets available, and the wireless communication device 12 receives and decodes system information including an indication of RACH root sequences that are available in the cell 16 and an indication of time-frequency resource sets available for random access preamble transmission. In addition or alternatively, the wireless communication device 12 may receive, from the radio access node 14, additional information to seed the algorithm used by the wireless

communication device 12 to determine its random access preamble sequence. For example, this information may include the total number of wireless

communication devices 12 anchored to the radio access node 14, information regarding the channel conditions, type of wireless communication device 12 (e.g., type of MTC device), timeout for the wireless communication device 12 in embodiments in which the wireless communication device 12 is a MTC device such as a sensor device, or the like. The wireless communication device 12 determines a random access preamble pattern that uniquely identifies the wireless communication device 12 as a function of an identity of the wireless communication device 12, as described above (step 302).

[0108] The wireless communication device 12 determines whether it is time to transmit uplink data (step 304). If not, the process returns to step 304 and waits until it is time to transmit uplink data. When it is time to transmit uplink data (e.g., when a timer at the wireless communication device 12 has expired), the wireless communication device 12 generates and transmits the set of random access preamble sequences on the respective sets of time-frequency resources as defined by the determined random access preamble pattern, as described above (step 306). For example, in some embodiments, the wireless communication device 12 determines a set of random access preamble sequences that uniquely identifies the wireless communication device 12 based on the identity of the wireless communication device 12. Then, for each random access occasion, the wireless communication device 12 determines whether the next (or first for the first iteration) random access preamble sequence in the determined set can be transmitted in the random access occasion. The wireless communication device 12 continues in this manner until all of the random access preamble sequences in the set have been transmitted. In this particular example, the set of random access preamble sequences uniquely identifies the wireless communication device 12. However, in other embodiments, the combination of the set of random access preamble sequences and the time-frequency resource sets used for transmission of the random access preamble sequences uniquely identifies the wireless communication device 12.

[0109] Figure 13 illustrates the operation of a radio access node 14 according to some embodiments of the present disclosure. This process is substantially the same as that described above with respect to Figure 8. As such, not all details will be repeated. Optional steps are represented by dashed boxes. As illustrated, the radio access node 14 optionally broadcasts system information that includes an indication of RACH root sequences that are available in the cell 16 and an indication of time-frequency resource sets that are available for transmission of random access preambles in the cell 16 (step 400). The radio access node 14 detects a random access preamble pattern (step 402). The radio access node 14 attempts to decode an identity of the wireless

communication device 12 that transmitted the detected random access preamble pattern based on the detected random access preamble pattern (step 404). In particular, the radio access node 14 attempts to match the random access preamble pattern (i.e., the entire pattern or only the set of random access preamble sequences transmitted in the pattern) to a known random access preamble pattern allocated to a particular identity (e.g., IMSI, IMEI, or the like). Alternatively, the radio access node 14 provides the detected random access preamble pattern to another network node that then attempts to decode the identity of the wireless communication device 12. If the identity of the wireless communication device 12 is successfully decoded (step 406, YES), the radio access node 14 optionally sends a random access response to the wireless communication device 12 to acknowledge receipt of the transmission of the random access preamble pattern (step 408). Successful decoding also results in the radio access node 14 determining that the identified wireless communication device 12 has communicated some defined user data (e.g., an OK status). If the identity of the wireless communication device 12 is not successfully decoded, e.g., within a defined amount of time (step 406, NO), the radio access node 14 optionally falls back to a conventional random access procedure, the details of which will be appreciated by one of skill in the art (step 410).

[0110] Figure 14 is a schematic block diagram of the wireless communication device 12 (e.g., MTC or loT device) according to some embodiments of the present disclosure. As illustrated, the wireless communication device 12 includes circuitry 20 comprising one or more processors 22 (e.g., Central Processing Units (CPUs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), Digital Signal Processors (DSPs), and/or the like) and memory 24. The wireless communication device 12 also includes one or more transceivers 26 each including one or more transmitters 28 and one or more receivers 30 coupled to one or more antennas 32. In some

embodiments, the functionality of the wireless communication device 12 described herein may be implemented in hardware (e.g., via hardware within the circuitry 20 and/or within the processor(s) 22) or be implemented in a

combination of hardware and software (e.g., fully or partially implemented in software that is, e.g., stored in the memory 24 and executed by the processor(s) 22).

[0111 ] In some embodiments, a computer program including instructions which, when executed by the at least one processor 22, causes the at least one processor 22 to carry out at least some of the functionality of the wireless communication device 12 according to any of the embodiments described herein is provided. In some embodiments, a carrier containing the aforementioned computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory).

[0112] Figure 15 is a schematic block diagram of the wireless communication device 12 (e.g., MTC or loT device) according to some other embodiments of the present disclosure. The wireless communication device 12 includes one or more modules 34, each of which is implemented in software. The module(s) 34 provide the functionality of the wireless communication device 12 described herein. For example, the modules(s) 34 may include a determining module operable to perform the function of step 204 of Figure 8 or step 302 of Figure 12 and a transmitting module operable to perform the function of step 206 of Figure 8 or step 306 of Figure 12.

[0113] Figure 16 is a schematic block diagram of a network node 36 (e.g., a radio access node 14 such as, for example, an eNB or gNB) according to some embodiments of the present disclosure. As illustrated, the network node 36 includes a control system 38 that includes circuitry comprising one or more processors 40 (e.g., CPUs, ASICs, DSPs, FPGAs, and/or the like) and memory 42. The control system 38 also includes a network interface 44. In embodiments in which the network node 36 is a radio access node 14, the network node 36 also includes one or more radio units 46 that each include one or more transmitters 48 and one or more receivers 50 coupled to one or more antennas 52. In some embodiments, the functionality of the network node 36 (specifically the functionality of the radio access node 14) described above may be fully or partially implemented in software that is, e.g., stored in the memory 42 and executed by the processor(s) 40.

[0114] Figure 17 is a schematic block diagram that illustrates a virtualized embodiment of the network node 36 (e.g., the radio access node 14) according to some embodiments of the present disclosure. As used herein, a "virtualized" network node 36 is a network node 36 in which at least a portion of the functionality of the network node 36 is implemented as a virtual component (e.g., via a virtual machine(s) executing on a physical processing node(s) in a network(s)). As illustrated, the network node 36 optionally includes the control system 38, as described with respect to Figure 16. In addition, if the network node 36 is the radio access node 14, the network node 36 also includes the one or more radio units 46, as described with respect to Figure 16. The control system 38 (if present) is connected to one or more processing nodes 54 coupled to or included as part of a network(s) 56 via the network interface 44.

Alternatively, if the control system 38 is not present, the one or more radio units 46 (if present) are connected to the one or more processing nodes 54 via a network interface(s). Alternatively, all of the functionality of the network node 36 (e.g., all of the functionality of the radio access node 14) described herein may be implemented in the processing nodes 54. Each processing node 54 includes one or more processors 58 (e.g., CPUs, ASICs, DSPs, FPGAs, and/or the like), memory 60, and a network interface 62.

[0115] In this example, functions 64 of the network node 36 (e.g., the functions of the radio access node 14) described herein are implemented at the one or more processing nodes 54 or distributed across the control system 38 (if present) and the one or more processing nodes 54 in any desired manner. In some particular embodiments, some or all of the functions 64 of the network node 36 described herein are implemented as virtual components executed by one or more virtual machines implemented in a virtual environment(s) hosted by the processing node(s) 54. As will be appreciated by one of ordinary skill in the art, additional signaling or communication between the processing node(s) 54 and the control system 38 (if present) or alternatively the radio unit(s) 46 (if present) is used in order to carry out at least some of the desired functions.

Notably, in some embodiments, the control system 38 may not be included, in which case the radio unit(s) 46 (if present) communicates directly with the processing node(s) 54 via an appropriate network interface(s).

[0116] In some particular embodiments, higher layer functionality (e.g., layer 3 and up and possibly some of layer 2 of the protocol stack) of the network node 36 may be implemented at the processing node(s) 54 as virtual components (i.e., implemented "in the cloud") whereas lower layer functionality (e.g., layer 1 and possibly some of layer 2 of the protocol stack) may be implemented in the radio unit(s) 46 and possibly the control system 38.

[0117] In some embodiments, a computer program including instructions which, when executed by the at least one processor 40, 58, causes the at least one processor 40, 58 to carry out the functionality of the network node 36 or a processing node 54 according to any of the embodiments described herein is provided. In some embodiments, a carrier containing the aforementioned computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as the memory 42, 60).

[0118] Figure 18 is a schematic block diagram of the network node 36 (e.g., the radio access node 14) according to some other embodiments of the present disclosure. The network node 36 includes one or more modules 66, each of which is implemented in software. The module(s) 66 provide the functionality of the network node 36 described herein. In some embodiments, the module(s) 66 comprise, for example, a detecting module operable to perform the function of step 208 of Figure 8 and step 402 of Figure 13 and a decoding module operable to perform the function of step 210 of Figure 8 and step 404 of Figure 13.

[0119] The following acronyms are used throughout this disclosure.

• με Microsecond

• 3GPP Third Generation Partnership Project

• 5G Fifth Generation

• ACK Acknowledgement

• ASIC Application Specific Integrated Circuit

• CP Cyclic Prefix

• CPU Central Processing Unit

• DSP Digital Signal Processor

• eNB Enhanced or Evolved Node B

• FPGA Field Programmable Gate Array

• gNB New Radio Base Station

• ID Identifier

• IMEI International Mobile Equipment Identity

• IMSI International Mobile Subscriber Identity

• loT Internet of Things

• IP Internet Protocol

• ISI Inter-Symbol Interference

• kHz Kilohertz

• km Kilometer • LTE Long Term Evolution

• MAC Medium Access Control

• MME Mobility Management Entity

• ms Millisecond

• MTC Machine Type Communication

• NB-loT Narrowband Internet of Things

• NPRACH Narrowband Physical Random Access Channel

• NR New Radio

• OFDM Orthogonal Frequency Division Multiplexing

• OTA Over-The-Air

• P-GW Packet Data Network Gateway

• PRACH Physical Random Access Channel

• PSS Primary Synchronization Signal

• PUSCH Physical Uplink Shared Channel

• RACH Random Access Channel

• RAR Random Access Response

• RB Resource Block

• RRC Radio Resource Control

• RSRQ Reference Signal Received Quality

• SCEF Service Capability Exposure Function

SC-FDMA Single Carrier Frequency Division Multiple Access SSS Secondary Synchronization Signal

UE User Equipment

[0120] Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein and the claims that follow.

Claims

Claims What is claimed is:

1 . A method of operation of a wireless communication device (12), comprising:

determining (204) a random access preamble pattern, at least a portion of which uniquely identifies the wireless communication device (12) within a given cell (16), as a function of an identity of the wireless communication device (12), wherein the random access preamble pattern defines:

- a plurality of random access preamble sequences; and

- a plurality of time-frequency resource sets for the plurality of

random access preamble sequences, respectively; and transmitting (206) the plurality of random access preamble sequences on the plurality of time-frequency resource sets in accordance with the random access preamble pattern.

2. The method of claim 1 wherein at least a portion of the plurality of random access preamble sequences uniquely identify the wireless communication device (12) within the cell (16).

3. The method of claim 1 wherein at least a portion of a combination of the plurality of random access preamble sequences and the plurality of time- frequency resource sets uniquely identify the wireless communication device (12) within the cell (16).

4. The method of any one of claims 1 to 3 wherein:

each random access preamble sequence is derived from a respective root sequence and a cyclic shift of the root sequence; and

for each random access preamble sequence of the plurality of random access preamble sequences, the time-frequency resource set defined by the random access preamble pattern for the random access preamble sequence is a time-frequency resource set in which only random access preambles derived from the respective root sequence can be transmitted within the cell (16) such that random access preambles transmitted in the time-frequency resource set are orthogonal.

5. The method of any one of claims 1 to 4 wherein the identity of the wireless communication device (12) is an International Mobile Subscriber Identity, IMSI, of the wireless communication device (12), an International Mobile Equipment Identity, IMEI, of the wireless communication device (12), an Internet Protocol, IP, address of the wireless communication device (12), or a Medium Access Control, MAC, address of the wireless communication device (12).

6. The method of any one of claims 1 to 5 wherein determining (204) the random access preamble pattern comprises determining (204) the random access preamble as a function of the identity of the wireless communication device (12) and user data to be conveyed by transmission of the plurality of random access preamble sequences on the plurality of time-frequency resource sets in accordance with the random access preamble pattern.

7. The method of any one of claims 1 to 6 wherein a length of the random access preamble pattern is dynamic.

8. The method of any one of claims 1 to 6 wherein a length of the random access preamble pattern is a function of:

a distance between the wireless communication device (12) and a radio access node (14) serving the cell (16);

feedback from the radio access node (14);

a total number of wireless communication devices anchored to the radio access node (14); one or more parameters indicative of a channel condition for a radio propagation channel between the wireless communication device (12) and the radio access node (14);

user data to be conveyed by transmission of the plurality of random access preamble sequences on the plurality of time-frequency resource sets in accordance with the random access preamble pattern; and/or

periodicity at which the wireless communication device (12) desires to convey user data via transmission of random access preamble sequences in accordance with respective random access sequence patterns.

9. The method of any one of claims 1 to 8 wherein the plurality of random access preamble sequences comprise random access preamble sequences derived from two or more different root sequences.

10. The method of any one of claims 1 to 9 wherein each time-frequency resource set of the plurality of time-frequency resource sets is a set of six contiguous physical resource blocks in the frequency domain and a defined amount of time in the time domain.

1 1 . The method of any one of claims 1 to 9 wherein each time-frequency resource set of the plurality of time-frequency resource sets is, for each random access preamble sequence of the plurality of random access preamble sequences, time-frequency resources for two or more repetitions of the random access preamble sequence on a plurality of subcarriers in accordance with a respective frequency hopping pattern.

12. A wireless communication device (12), for a wireless communication system (10), the wireless communication device (12) adapted to:

determine a random access preamble pattern, at least a portion of which uniquely identifies the wireless communication device (12) within a given cell (16), as a function of an identity of the wireless communication device (12), wherein the random access preamble pattern defines:

- a plurality of random access preamble sequences; and

- a plurality of time-frequency resource sets for the plurality of

random access preamble sequences, respectively; transmit the plurality of random access preamble sequences on the plurality of time-frequency resource sets in accordance with the random access preamble pattern.

13. The wireless communication device (12) of claim 12 wherein the wireless communication device (12) is further adapted to perform the method of any one of claims 2 to 1 1 .

14. A wireless communication device (12), for a wireless communication system (10), comprising:

at least one transmitter (28); and

circuitry (20) associated with the at least one transmitter (28), the circuitry (20) operable to:

- a plurality of random access preamble sequences; and

- a plurality of time-frequency resource sets for the plurality of random access preamble sequences, respectively; and transmit the plurality of random access preamble sequences on the plurality of time-frequency resource sets in accordance with the random access preamble pattern.

15. A wireless communication device (12), for a wireless communication system (10), comprising: a determining module (34) operable to determine a random access preamble pattern, at least a portion of which uniquely identifies the wireless communication device (12) within a given cell (16), as a function of an identity of the wireless communication device (12), wherein the random access preamble pattern defines:

- a plurality of random access preamble sequences; and

- a plurality of time-frequency resource sets for the plurality of

random access preamble sequences, respectively; and a transmitting module (34) operable to transmit the plurality of random access preamble sequences on the plurality of time-frequency resource sets in accordance with the random access preamble pattern.

16. A computer program comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the method according to any one of claims 1 to 1 1 .

17. A carrier containing the computer program of claim 16, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium.

18. A method of operation of a radio access node (14) in a wireless communication system (10), comprising:

detecting (208) a plurality of random access preamble sequences transmitted by a wireless communication device (12) on a plurality of time- frequency resource sets, respectively, in accordance with a random access preamble pattern; and

decoding (210) an identity of the wireless communication device (12) based on the random access preamble pattern, the random access preamble pattern being a function of the identity of a wireless communication device (12) and at least a portion of the random access preamble pattern uniquely identifies the wireless communication device (12) within a cell (16) served by the radio access node (14).

19. The method of claim 18 wherein at least a portion of the plurality of random access preamble sequences uniquely identify the wireless

communication device (12) within the cell (16).

20. The method of claim 18 wherein at least a portion of a combination of the plurality of random access preamble sequences and the plurality of time- frequency resource sets uniquely identify the wireless communication device (12) within the cell (16).

21 . The method of any one of claims 18 to 20 wherein:

each random access preamble sequence is derived from a respective root sequence; and

for each random access preamble sequence of the plurality of random access preamble sequences, the time-frequency resource set defined by the random access preamble pattern for the random access preamble sequence is a time-frequency resource set in which only random access preambles derived from the respective root sequence can be transmitted within the cell (16).

22. The method of any one of claims 18 to 21 wherein the identity of the wireless communication device (12) is an International Mobile Subscriber Identity, IMSI, of the wireless communication device (12), an International Mobile Equipment Identity, IMEI, of the wireless communication device (12), an Internet Protocol, IP, address of the wireless communication device (12), or a Medium Access Control, MAC, address of the wireless communication device (12).

23. The method of any one of claims 18 to 22 wherein the random access preamble is a function of the identity of the wireless communication device (12) and user data to be conveyed by the wireless communication device (12) by transmission of the plurality of random access preamble sequences on the plurality of time-frequency resource sets in accordance with the random access preamble pattern.

24. The method of any one of claims 18 to 23 wherein a length of the random access preamble pattern is dynamic.

25. The method of any one of claims 18 to 23 wherein a length of the random access preamble pattern is a function of:

a distance between the wireless communication device (12) and the radio access node (14) serving the cell (16);

feedback provided to the wireless communication device (12) by the radio access node (14);

a total number of wireless communication devices anchored to the radio access node (14);

one or more parameters indicative of a channel condition for a radio propagation channel between the wireless communication device (12) and the radio access node (14);

user data to be conveyed by the wireless communication device (12) by transmission of the plurality of random access preamble sequences on the plurality of time-frequency resource sets in accordance with the random access preamble pattern; and/or

26. The method of any one of claims 18 to 25 wherein the plurality of random access preamble sequences comprise random access preamble sequences derived from two or more different root sequences.

27. The method of any one of claims 18 to 26 wherein each time-frequency resource set of the plurality of time-frequency resource sets is a set of six contiguous physical resource blocks in the frequency domain and a defined amount of time in the time domain.

28. The method of any one of claims 18 to 26 wherein each time-frequency resource set of the plurality of time-frequency resource sets is, for each random access preamble sequence of the plurality of random access preamble sequences, time-frequency resources for two or more repetitions of the random access preamble sequence on a plurality of subcarriers in accordance with a respective frequency hopping pattern.

29. A radio access node (14) for a wireless communication system (10), the radio access node (14) adapted to:

detect a plurality of random access preamble sequences transmitted by a wireless communication device (12) on a plurality of time-frequency resource sets, respectively, in accordance with a random access preamble pattern; and decode an identity of a wireless communication device (12) based on the random access preamble pattern, the random access preamble pattern being a function of the identity of the wireless communication device (12) and at least a portion of the random access preamble pattern uniquely identifies the wireless communication device (12) within a cell (16) served by the radio access node (14).

30. The radio access node (14) of claim 29 wherein the radio access node (14) is further adapted to perform the method of any one of claims 19 to 28.

31 . A radio access node (14) for a wireless communication system (10), comprising:

at least one receiver (50); and circuitry (40, 42, 58, 60) associated with the at least one receiver (50) operable to:

detect a plurality of random access preamble sequences transmitted by a wireless communication device (12) on a plurality of time- frequency resource sets, respectively, in accordance with a random access preamble pattern; and

decode an identity of the wireless communication device (12) based on the random access preamble pattern, the random access preamble pattern being a function of the identity of the wireless

communication device (12) and at least a portion of the random access preamble pattern uniquely identifies the wireless communication device (12) within a cell (16) served by the radio access node (14).

32. A radio access node (14) for a wireless communication system (10), comprising:

a detecting module (66) operable to detect a plurality of random access preamble sequences transmitted by a wireless communication device (12) on a plurality of time-frequency resource sets, respectively, in accordance with a random access preamble pattern; and

a decoding module (66) operable to decode an identity of the wireless communication device (12) based on the random access preamble pattern, the random access preamble pattern being a function of the identity of the wireless communication device (12) and at least a portion of the random access preamble pattern uniquely identifies the wireless communication device (12) within a cell (16) served by the radio access node (14).

33. A computer program comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the method according to any one of claims 18 to 28.

34. A carrier containing the computer program of claim 33, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium.