WO2017182053A1

WO2017182053A1 - Method and device for establishing transmission over a predefined physical channel

Info

Publication number: WO2017182053A1
Application number: PCT/EP2016/058555
Authority: WO
Inventors: Long QIN; Zhao ZHAO; Qi Wang; Mingyue Zhou
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2016-04-18
Filing date: 2016-04-18
Publication date: 2017-10-26
Anticipated expiration: 2018-10-18
Also published as: CN109076500A

Abstract

The disclosure relates to a method (900a, 900b) for establishing data transmission over a predefined physical channel, the method comprising: broadcasting, by a base station, configuration information of a predefined physical channel wherein the configuration information (914) comprises physical resource allocation and transmit parameters; receiving (910, a), by a user equipment, (UE) (101, 102), configuration information (914) via a downlink broadcast channel (912, 913) from a base station (BS) (103); determining (910, b), by the UE (101, 102), whether the UE (101, 102) is qualified for transmission based on the received configuration information (914) and given capabilities of the UE (101, 102); and if the UE (101, 102) is qualified (503) for the transmission, selecting (920, c), by the UE (101, 102), a subset of the physical resource within the pre-defined physical channel (701, 702, 703, 801, 803) and transmitting uplink data (921, 923) to the BS (103) on the selected subset of the physical resource.

Description

Method and device for establishing transmission over a predefined physical channel

TECHNICAL FIELD

The present disclosure relates to a method and a device for establishing transmission over a predefined physical channel in mobile wireless communication networks, in particular for User Equipment (UE) initiated data connections. The present disclosure further relates to random access procedures for grant-free and Timing Adjustment (TA)- free transmission.

BACKGROUND In a mobile wireless communication network 100 as shown in Fig. 1 , a UE 101 , 102 carries out the so-called random access procedure before uplink data transmission to the Base Station (BS) 103. In this procedure, the UE 101 , 102 exchanges several signalling messages with the BS 103 in order to be synchronized and/or scheduled. According to Next Generation Mobile Networks (NGMN), 5G White Paper, Feb. 2015, the next wave of mobile communication is to mobilize and automate industries and industry processes, widely referred to as machine-type communication. It is foreseen that the number of devices that access the mobile radio network will be dramatically increased. Also, the machine-type devices differ in terms of requirements with respect to power consumption, latency and throughput etc. This poses new challenges to the next generation mobile wireless networks.

The state-of-the-art random access procedure aims to establish synchronous, orthogonal data transmission. Firstly, the uplink synchronization is obtained using the timing advance 121 , 122 which corresponds to the time a signal takes to reach the BS 103 from the UE 101 , 102. A UE 101 , 102 is informed by the BS 103 about its timing advance 121 , 122 in order to adjust its timing 1 1 1 , 1 12 so that the signals from all UEs 101 , 102 are aligned at the BS 103. Such a process is illustrated in Figure 1 . After the uplink transmission timing 1 1 1 , 1 12 is synchronized with the BS timing 1 13, the BS 103 grants each UE 101 , 102 a fraction 21 1 , 212 of the resource 201 , 202 and ensures that resources 21 1 , 212 for different UEs 101 , 102 are orthogonal to one another (illustrated in Figure 2). Finally, data transmission can be carried out. The drawbacks this random access scheme lie in the following two aspects: For large packet transmission, the signalling overhead required for the random access procedure can be neglected; however, for small packet transmission generated by the machine-type devices, this signalling overhead becomes significant. In addition, as the number of devices increases, the random access procedure may create huge traffic load to the network. Since the timing misalignments of different UEs are in fact the propagation delays which the electromagnetic signal travels from the base station 103 to the UEs 101 , 102, as the UEs move in high velocity, there exists higher probability that the

synchronization got lost. In a high velocity scenario, the random access procedure needs to be carried out more frequently, which leads to significant signalling overhead.

Therefore, a new random access procedure that allows for asynchronous non-orthogonal access, i.e., TA-free and grant-free, is desired.

SUMMARY

It is the object of the invention to provide an improved random access procedure for mobile wireless communications, in particular for high velocity communication

environments and machine-type communication scenarios.

This object is achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

A basic idea of the invention is to provide a novel random access procedure which allows TA-free and grant-free transmission. The timing adjustment is carried out either in an open-loop or in an "on request" manner. The new approach simplifies the existing random access procedure and can be applied to massive machine-type communications.

Typical applications include mobile radio access of massive machine type communication which is described as sporadic low data-rate traffic and mobile radio services with latency constraint. The devices described herein may be configured to transmit and/or receive radio signals. Radio signals may be or may include radio frequency signals radiated by a radio transmitting device (or radio transmitter or sender) with a radio carrier frequency lying in a range of about 3 Hz to 300 GHz. The frequency range may correspond to frequencies of alternating current electrical signals used to produce and detect radio waves.

The devices described herein may be applied in OFDM and OFDMA systems. OFDM and OFDMA are schemes for encoding digital data on multiple carrier frequencies. A large number of closely spaced orthogonal sub-carrier signals may be used to carry data. Due to the orthogonality of the sub-carriers crosstalk between sub-carriers may be

suppressed. The devices described herein may be applied in 802.1 1 ax systems. In 802.1 1 ax standard development, control mechanisms, like random access (RA), acknowledgment (ACK), association request etc., are applied immediately after a trigger frame (TF) that is transmitted by the access point (AP) or base station (BS). Thus the stations (STAs) or User Equipments (UEs) wait for the AP to trigger them. A Trigger Frame may be followed by one or more uplink (UL) frames, where each frame comprises a control signal transmitted by one or more UEs.

The devices described herein may perform random access procedures. Random access (RA) is a procedure that allows client type communication devices to request from an access point (AP) type communication device resources for transmission by use of a resource request and by another procedure to initiate an association procedure with the AP. In other words, this mechanism is usually applied by the client type communication devices that need to request the resources. The client type communication devices can achieve an association with a specific AP. Currently, in the 802.1 1 ax standard, RA is applied immediately after a trigger frame (TF), which is transmitted by the AP. Thus the client type communication devices wait for AP to trigger them (indicate the existence of a random access opportunity). A TF frame may be followed by several RA opportunities. Within each opportunity, clients can try to access the channel. For doing so they contend with each other.

The devices described herein may be configured to perform contention-based 300 or non- contention-based 400 random access, e.g. according to 3GPP TS 36.300 Release 12, 2014-09. The random access procedure in LTE comes in two forms, allowing access to be either contention based or non-contention based. Prior to any of the two, a UE acquires time and frequency synchronization 303 with a cell and decodes the Master Information Block (MIB) and System Information Block (SIB) 301 in the Broadcast Channel (BCH) 302 to obtain essential system information of the cell. As illustrated in Figure 3, the contention based 300 random access procedure 320 comprises the following four steps: Preamble 304 transmission, Random Access

Response (RAR) 306, Layer 2/Layer 3 (L2/L3) message 309 and contention resolution message 31 1 . In Preamble transmission in LTE, the dedicated Physical Random Access Channel (PRACH) 305 is allocated for random access (RA) preamble 304 transmission. The UE selects one of the available PRACH contention-based preambles and transmits in the PRACH 305. In Random Access Response (RAR) 306, the RAR is sent by the BS 103 on the downlink shared channel (DL-SCH) 307 and addressed with an ID which identifies the time-frequency slot in which the preamble was detected. The RAR 306 also conveys a timing alignment instruction to synchronize subsequent uplink transmission 321 from the UE 101 , an initial uplink resource grant for transmission of the Step 3 message, and an assignment of a Temporary Cell Radio Network Temporary Identifier (C-RNTI). The Layer 2/Layer 3 (L2/L3) message 309 is the first scheduled uplink transmission on the uplink shared channel (UL-SCH) 310 and makes use of Hybrid Automatic Repeat request (HARQ). It conveys the actual RA procedure message, such as an RRC connection request 309, tracking area update, or scheduling request. The contention resolution message 31 1 is addressed to the C-RNTI or Temporary C- RNTI. Upon Reception of this message 312, the UE 101 decides if a positive

ACKnowledgement (ACK) should be sent.

When low latency is required, such as handover and resumption of downlink traffic for a UE, the non-contention based 400 random access procedure 420 is performed. Instead of a randomly selected RA preamble 304, a dedicated preamble 403 is allocated 401 to the UE 101 via dedicated signalling 402 in DL. Then the assigned preamble 403 is transmitted 305. The step 2 in contention based (RAR, 306) is carried out to obtain uplink

synchronization 407. Such a procedure is outlined in Figure 4.

In order to describe the invention in detail, the following terms, abbreviations and notations will be used:

TA: Timing Adjustment

AP: Access Point, also base station

OFDM: Orthogonal Frequency Division Multiplexing

CP-OFDM: Cyclic Prefix Orthogonal Frequency Division Multiplexing P-OFDM: Pulse-shaped Orthogonal Frequency Division Multiplexing

TF: Trigger Frame

RA: Random Access

ACK: Acknowledgement

NACK: Non-Acknowledgement

UL: Uplink

DL: Downlink

MIMO: Multiple Input Multiple Output

BS: Base Station

UE: User Equipment

GF: Grant-Free

GFACH: Grant-Free Access Channel

SIB: System Information Block

MIB: Management Information Block

LTE: Long Term Evolution

BCH: Broadcast Channel

RAR: Random Access Response

ID: Identifier

DL-SCH: Downlink shared channel

RACH: Random Access Channel

PRACH: Physical Random Access Channel

C-RNTI: Cell Radio Network Temporary Identifier

UL-SCH: Uplink Shared Channel

L2/L3: Layer 2/Layer 3 according to the OSI model communication standard

HARQ: Hybrid Automatic Repeat Request

PUSCH: Physical Uplink Shared Channel

BLER: Block Error Rate

PRB: Physical Resource Block, physical resources in time and frequency

MCS: Modulation and Coding Scheme

SDMA: Space Division Multiple Access

SNR: Signal to Noise Ratio

FDD: Frequency Division Duplex

According to a first aspect, the invention relates to a method for establishing data transmission over a predefined physical channel, the method comprising: broadcasting, by a base station, configuration information of a predefined physical channel wherein the configuration information comprises physical resource allocation and transmit parameters; receiving, by a user equipment, UE, the configuration information via a downlink broadcast channel from the base station, BS; determining, by the UE, whether the UE is qualified for transmission based on the received configuration information and given capabilities of the UE; and if the UE is qualified for the transmission, selecting, by the UE, a subset of the physical resource within the pre-defined physical channel and transmitting uplink data to the BS on the selected subset of the physical resource.

By using that transmission, a number of signaling messages for initiating communication between UE and BS can be reduced. Hence, this method provides an improved random access procedure for mobile wireless communications and can be applied in particular for high velocity communication environments and machine-type communication scenarios.

In a first possible implementation form of the method according to the first aspect, the uplink data comprises signaling information and payload data, wherein the payload data comprises an identifier of the UE.

This provides the advantage that when transporting both signaling information and payload data including the UE ID, the number of messages can be reduced. This can be advantageously applied in high velocity communication environments and machine-type communication scenarios, e.g. according to LTE standardization.

In a second possible implementation form of the method according to the first aspect as such or according to the first implementation form of the first aspect, determining, by the UE, whether the UE is qualified for the transmission comprises: evaluating a UE category tag or a UE configuration which indicate whether the UE is qualified for the transmission.

In a third possible implementation form of the method according to the first aspect as such or according to any of the preceding implementation forms of the first aspect, the transmission comprises grant-free and timing-advance (TA)-free data transmission.

This provides the advantage that without waiting for a grant and/or without waiting for a timing advance, the data transmission can be established faster, thereby achieving higher data throughput. In a fourth possible implementation form of the method according to the first aspect as such or according to any of the preceding implementation forms of the first aspect, the method comprises: receiving feedback information for the transmitted uplink data from the BS; indicating a successful data transmission if the feedback information comprises an acknowledgement (ACK); repeating the selection of a subset of the physical resource within the pre-defined physical channel and the transmission of the uplink data on the selected subset of the physical resource if the feedback information comprises a non- acknowledgement (NACK) or no feedback is received; repeating the random selection of a subset of the physical resource within the pre-defined physical channel and the transmission of the uplink data until either feedback information comprising an ACK is received or a given number of retransmissions, in particular a number of retransmissions configured by the BS, is reached; and if the given number of retransmissions is reached, triggering a timing adjustment and synchronization procedure.

This provides the advantage that by the feedback information a number of

retransmissions can be efficiently controlled. Using feedback information increases data throughput because only erroneously transmitted data is retransmitted. Efficiency of the transmission is improved because only non-acknowledged data is retransmitted.

Efficiency of the transmission is further improved due to definition of a stop criterion, i.e. a maximum number of retransmissions, which triggers a timing adjustment and

synchronization procedure for improving transmission. In a fifth possible implementation form of the method according to the first aspect as such or according to any of the preceding implementation forms of the first aspect, the method further comprises: if a timing adjustment and synchronization procedure is triggered, initiating an open-loop timing adjustment by advancing a timing for transmission of the uplink data to the BS by a pre-defined amount of time; and repeating the random selection of a subset of the physical resource within the pre-defined physical channel and the transmission of the uplink data using the advanced symbol timing for transmission of the uplink data to the BS.

This provides the advantage that by advancing the symbol timing by a pre-defined amount of time allows the UE to achieve resynchronization with the timing of the base station. This provides the further advantage that the grant-free and TA-free data transmission can be used again with a different symbol timing which allows to reduce a number of signaling messages for initiating communication between UE and BS. In a sixth possible implementation form of the method according to any of the fourth or fifth implementation forms of the first aspect, the method further comprises: if the timing adjustment and synchronization procedure is triggered, starting a closed-loop timing adjustment by initiating a contention based random access procedure.

This provides the advantage that in case of errors, i.e. when number of retransmissions crosses a threshold, the method may change to a different procedure which is the contention based random access procedure thereby increasing efficiency of data transmission.

In a seventh possible implementation form of the method according to the first aspect as such or according to any of the preceding implementation forms of the first aspect, the pre-defined physical channel comprises physical resources which allow for grant-free and TA-free uplink data transmission.

This provides the advantage that by using grant-free and TA-free data transmission, a number of signaling messages for initiating communication between UE and BS can be reduced which speed up data transmission and increases throughput.

In an eighth possible implementation form of the method according to the first aspect as such or according to any of the preceding implementation forms of the first aspect, the configuration information comprises a size and allocation and transmission scheme of the pre-defined physical channel, in particular at least one of a physical resource, modulation and coding schemes, a maximum payload size and a number of allowed retransmissions.

This provides the advantage that the configuration is highly flexible and supports a lot of different configurations.

According to a second aspect, the invention relates to a data transmission device for a user equipment, UE for establishing data transmission over a predefined physical channel, the data transmission device comprising: a receive module, configured to receive configuration information via a downlink broadcast channel from a base station, BS, wherein the configuration information comprises physical resource allocation and transmit parameters of the predefined physical channel; a determination module, configured to determine whether the UE is qualified for transmission based on the received

configuration information and given capabilities of the UE; and a transmission module, configured to select a subset of the physical resource within the pre-defined physical channel and to transmit uplink data to the BS on the selected subset of the physical resource, if the UE is qualified for the transmission. By using that transmission, a number of signaling messages for initiating communication between UE and BS can be reduced. Hence, such a data transmission device provides an improved random access procedure for asynchronous non-orthogonal mobile wireless communications and can be applied in particular for data transmission in high velocity communication environments and machine-type communication scenarios.

In a first possible implementation form of the device according to the second aspect, the transmission comprises grant-free and timing-adjustment (TA)-free data transmission.

This provides the advantage that without waiting for a grant and/or without waiting for a timing advance, the data transmission can be established faster, thereby achieving higher data throughput and lower latency. According to a third aspect, the invention relates to a radio cell, comprising: a decision module configured to determine configuration information of a predefined physical channel, wherein the configuration information comprises physical resource allocation and transmit parameters of the predefined physical channel; and a broadcast transmission module configured to broadcast the configuration information via a downlink broadcast channel to at least one UE for establishing data transmission with the at least one UE over the predefined physical channel.

The radio cell may be a base station (BS) for supporting communication with a UE.

Alternatively, the radio cell may be another UE for supporting device-to-device

communication with a UE. In the device-to-device case, the downlink and uplink operations are applicable to the sidelink.

Such a radio cell provides the advantage that by using that transmission, a number of signaling messages for initiating communication between UE and radio cell can be reduced. Hence, such a radio cell provides an improved random access procedure for mobile wireless communications and can be applied in particular for high velocity communication environments and machine-type communication scenarios.

In a first possible implementation form of the radio cell according to the third aspect, the pre-defined physical channel comprises physical resources which allow for grant-free and TA-free uplink data transmission. This provides the advantage that such a radio cell using grant-free and TA-free data transmission, allows to reduce a number of signaling messages for initiating

communication between UE and radio cell which speeds up data transmission and increases throughput.

According to a fourth aspect, the invention relates to a transmission system, comprising: a user equipment (UE) comprising a data transmission device according to the second aspect or the implementation forms of the second aspect claim; and a radio cell according the third aspect or the implementation forms of the third aspect, wherein the transmission system is configured to establish data transmission between the UE and the radio cell over the predefined physical channel.

Such a transmission system provides the advantage that by using that transmission, a number of signaling messages for initiating communication between UE and radio cell, e.g. BS or other UE, can be reduced. Hence, that transmission system provides an improved transmission and a random access procedure for mobile wireless

communications and can be applied in particular for high velocity communication environments and machine-type communication scenarios. According to a fifth aspect, the invention relates to a computer program comprising program code for performing the method according to the first aspect or any of the implementation forms of the first aspect when executed on a computer.

In a second possible implementation form of the device according to the second aspect, the data transmission device is configured to trigger a timing adjustment and

synchronization procedure if a given number of retransmissions is reached.

This improves efficiency of the transmission because a stop criterion is defined, i.e. a maximum number of retransmissions, which triggers a timing adjustment and

synchronization procedure for improving transmission.

In a third possible implementation form of the device according to the second aspect as such or according to the implementation forms of the second aspect, the device further comprises an open loop-timing adjustment module configured to advance a symbol timing for transmission of the uplink data to the BS by a pre-defined amount of time based on a triggering of the trigger module. This provides the advantage that the grant-free and TA-free data transmission can be used again with a different symbol timing which allows to reduce a number of signaling messages for initiating communication between UE and BS. In a ninth possible implementation form of the method according to the sixth

implementation form of the first aspect, the contention based random access procedure comprises: randomly selecting a preamble that corresponds to transmission over a Physical Random Access Channel (PRACH). This provides the advantage that in case of severe errors, preamble selection can be applied which improves efficiency of data transmission.

Further aspects of the invention are related to a transport/physical channel which allows grant-free access; a timing adjustment procedure which is triggered by the sync status; Random access procedures (combination of above-indicated decision module and timing adjustment procedure) which enable grant-free and TA-free access; a parameter which specifies the maximum number of grant-free retransmission allowed in the cell; and Pulse shape design that allows non-orthogonal asynchronous multiple access transmission.

BRIEF DESCRIPTION OF THE DRAWINGS

Further embodiments of the invention will be described with respect to the following figures, in which:

Fig. 1 shows a schematic diagram illustrating uplink synchronization 100 using timing advance;

Fig. 2 shows a schematic diagram illustrating an example of Orthogonal multiple access 200;

Fig. 3 shows a schematic diagram illustrating a contention based random access procedure 300; Fig. 4 shows a schematic diagram illustrating a non-contention based random access procedure 400; Fig. 5 shows a schematic diagram illustrating a method 500 for establishing transmission over a predefined physical channel according to an implementation form;

Fig. 6 shows a block diagram illustrating a data transmission device 600 for establishing transmission over a predefined physical channel according to an implementation form;

Fig. 7 shows a schematic diagram illustrating a physical resource 700 including GFACH (Grant-free access channel) allocated to fixed physical resource 701 , 702, 703 according to an implementation form;

Fig. 8 shows a schematic diagram illustrating a physical resource 800 including GFACH (Grant-free access channel) allocated to physical resource 801 , 803 by using dynamic resource allocation according to an implementation form; Fig. 9 shows a schematic diagram illustrating a method for performing a random access procedure 900a according to a first variant;

Fig. 10 shows a schematic diagram illustrating a method for performing a random access procedure 900b according to a second variant;

Fig. 1 1 shows an amplitude over time diagram illustrating different exemplary pulse shapes used for testing the random access procedures 900a and 900b; and

Fig. 12 shows a performance diagram illustrating BLER over SNR for different OFDM configurations.

DETAILED DESCRIPTION OF EMBODIMENTS In the following detailed description, reference is made to the accompanying drawings, which form a part thereof, and in which is shown by way of illustration specific aspects in which the disclosure may be practiced. It is understood that other aspects may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims. It is understood that comments made in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if a specific method step is described, a corresponding device may include a unit to perform the described method step, even if such unit is not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary aspects described herein may be combined with each other, unless specifically noted otherwise.

Fig. 5 shows a schematic diagram illustrating a method 500 for establishing transmission over a predefined physical channel according to an implementation form.

The method 500 includes broadcasting 501 , by a base station, configuration information of a predefined physical channel wherein the configuration information comprises physical resource allocation and transmit parameters, e.g. as described below with respect to Fig. 9.

The method further includes receiving 502, by a user equipment, UE 101 , 102, configuration information via a downlink broadcast channel from a base station BS 103. The method further includes determining 503, by the UE 101 , 102, whether the UE 101 , 102 is qualified for transmission based on the received configuration information and given capabilities of the UE 101 , 102.

The method further includes: if the UE 101 , 102 is qualified 503 for the transmission, selecting 504, by the UE 101 , 102, a subset of the physical resource within the predefined physical channel and transmitting uplink data to the BS 103 on the selected subset of the physical resource.

The subset of the physical resource 700, 800 may be a GFACH channel 701 , 702, 703 allocated to a fixed physical resource as described below with respect to Fig. 7 or a GFACH channel 801 , 803 dynamically allocated to a physical resource as described below with respect to Fig. 8.

The transmission may be a grant-free and/or timing adjustment (TA)-free data

transmission. The uplink data may include an uplink transport block which may include signaling information and uplink payload data. The uplink payload data may include an identifier (ID) of the UE. The method 500 may further include: receiving feedback information for the transmitted uplink data from the BS. The method 500 may further include: indicating a successful data transmission if the feedback information comprises an acknowledgement (ACK); and repeating the selection of a subset of the physical resource within the predefined physical channel and the transmission of the uplink data on the selected subset of the physical resource if no feedback information is received or the feedback information comprises a non-acknowledgement (NACK).

The method 500 may further include: repeating the random selection of a subset of the physical resource within the pre-defined physical channel and the transmission of the uplink data until either feedback information comprising an ACK is received or a given number of retransmissions, in particular a number of retransmissions configured by the BS, is reached; and if the given number of retransmissions is reached, triggering a timing adjustment and synchronization procedure.

The method 500 may further include: if a timing adjustment and synchronization procedure is triggered, initiating an open-loop timing adjustment by advancing a symbol timing for transmission of the uplink data to the BS by a pre-defined amount of time.

The method 500 may further include: repeating the random selection of a subset of the physical resource within the pre-defined physical channel and the transmission of the uplink data using the advanced symbol timing for transmission of the uplink data to the BS.

The method 500 may further include: if the timing adjustment and synchronization procedure is triggered, starting a closed-loop timing adjustment by initiating a contention based random access procedure. The contention based random access procedure may include: randomly selecting a preamble that corresponds to transmission over a Physical Random Access Channel (PRACH).

The pre-defined physical channel may include physical resources which allow for grant- free and TA-free uplink data transmission. The pre-defined physical channel may be a grant-free access channel (GFACH) as introduced in this disclosure. The configuration information may include a size or transmission scheme of the pre-defined physical channel, in particular at least one of a physical resource, modulation and coding schemes, a maximum payload size and a number of allowed retransmissions.

Fig. 6 shows a block diagram illustrating a data transmission device 600 for a user equipment (UE) for establishing transmission over a predefined physical channel according to an implementation form. The data transmission device 600 includes a receive module 601 , a determination module 603 and a transmission module 605.

The receive module 601 receives configuration information 604 via a downlink broadcast channel 602 from a base station (BS). The configuration information 604 includes physical resource allocation and transmit parameters of the predefined physical channel. The determination module 603 determines whether the UE is qualified for transmission based on the received configuration information 604 and given capabilities of the UE. The transmission module 605 selects a subset of the physical resource within the pre-defined physical channel and transmits uplink data 608 to the BS on the selected subset of the physical resource, if the UE is qualified 606 for the transmission.

The transmission may be a grant-free and/or TA-free data transmission. The data transmission device 600 may further include a trigger module that may trigger a timing adjustment and synchronization procedure if a given number of retransmissions is reached. The data transmission device 600 may further include an open loop-timing adjustment module that may advance a symbol timing for transmission of the uplink data to the BS by a pre-defined amount of time based on a triggering of the trigger module.

The data transmission device 600 may implement the method 500 described above with respect to Fig. 5 and the methods 900a, 900b described below with respect to Figures 9 and 10. The configuration information may be determined by a base station, e.g. a BS 103 as described above with respect to Fig. 1. Such a base station includes a decision module and a broadcast transmission module. The decision module determines configuration information 604 of a predefined physical channel, wherein the configuration information 604 comprises physical resource allocation and transmit parameters of the predefined physical channel. The broadcast transmission module broadcasts the configuration information via a downlink broadcast channel to at least one UE 101 , 102 for establishing data transmission with the at least one UE 101 , 102 over the predefined physical channel. The pre-defined physical channel may include physical resources which allow for grant- free and TA-free uplink data transmission.

A transmission system, e.g. as shown in Fig. 1 , includes a user equipment (UE) comprising a data transmission device 600 and a base station 103 as described above. The transmission system is configured to establish data transmission between the UE and the BS over the predefined physical channel.

Fig. 7 shows a schematic diagram illustrating a physical resource 700 including GFACH (Grant-free access channel) allocated to fixed physical resource 701 , 702, 703 according to an implementation form and Fig. 8 shows a schematic diagram illustrating a physical resource 800 including GFACH allocated to physical resource 801 , 803 by using dynamic resource allocation according to an implementation form. The present disclosure introduces a transport or physical channel dedicated for TA-free and grant-free transmissions. Such a channel defines how and with what characteristics the information is transmitted over the radio interface. Here the name Grant-Free Access Channel (GFACH) is used as an example. A channel like GFACH is a pre-condition of the presented random access procedure and may be defined as part of the system

specification. The configuration of GFACH in a cell may be included in the master information block (MIB) or system information block (SIB) which is broadcasted to all UEs within the cell.

The configuration of GFACH consists of the following aspects: a) Resource allocation: The allocation of GFACH can be either fixed or dynamic in terms of the physical resource, as illustrated in Figures 7 and 8. For the dynamic case, the base station can determine the size or allocation of the GFACH according to the network traffic, b) Transmit parameters, namely modulation/coding schemes, the maximum size of payload which is allowed, the maximum number of retransmissions R, timing adjustment interval etc. These parameters can either be semi-static or dynamically determined by the base station in accordance to the resource allocation.

Figures 9 and 10 as described in the following illustrate two random access procedures 900a, 900b which can be applied to realize grant-free and TA-free uplink transmission. Both procedures 900a, 900b are implementation forms of the general method 500 described above with respect to Fig. 5. Fig. 9 shows a schematic diagram illustrating a method for performing a random access procedure 900a according to a first variant. The method 900a is an implementation form of the method 500 described above with respect to Fig. 5. The method 900a establishes a grant-free and TA-free data transmission over a predefined physical channel 701 , 702, 703, 801 , 803.

The method 900a includes: receiving 910, a, by a user equipment, UE 101 , 102, configuration information 914 via a downlink broadcast channel 912, 913 from a base station (BS) 103. The configuration information 914 includes physical resource allocation and transmit parameters of the predefined physical channel 701 , 702, 703, 801 , 803.

The method 900a further includes: determining 910, b, by the UE 101 , 102, whether the UE 101 , 102 is qualified for a grant-free and TA-free data transmission based on the received configuration information 914 and given capabilities of the UE 101 , 102.

The method 900a further includes: If the UE 101 , 102 is qualified for a grant-free and TA- free data transmission, selecting 920, c, by the UE 101 , 102, a subset of the physical resource, e.g. a subset of the physical resource 701 , 702, 703, 801 , 803 as described above with respect to Figures 7 and 8, within the pre-defined physical channel 701 , 702, 703, 801 , 803 and transmitting uplink data 921 , 923 to the BS 103 on the selected subset of the physical resource.

The uplink data 921 , 923 may include an uplink transport block which comprises uplink payload data.

The method 900a may further include: receiving feedback information 927, 928 for the transmitted uplink data 921 , 923 from the BS 103. The method 900a may further include: indicating a successful data transmission if the feedback information comprises an acknowledgement (ACK) 927; and repeating the random selection 920, c of a subset of the physical resource within the pre-defined physical channel 701 , 702, 703, 801 , 803 and the transmission of the uplink data 921 , 923 on the selected subset of the physical resource if either the feedback information comprises a non-acknowledgement (NACK) 928 or no feedback information is received. The method 900a may further include: repeating 930, f the random selection 920, c of a subset of the physical resource within the pre-defined physical channel 701 , 702, 703, 801 , 803 and the transmission of the uplink data 923 until either feedback information comprising an ACK 927 is received or a given number of retransmissions, in particular a number of retransmissions configured by the BS 103, is reached.

The method 900a may further include: if the given number of retransmissions is reached, triggering 939, 959 a timing adjustment and synchronization procedure 940, 960.

The method 900a may further include: if a timing adjustment and synchronization procedure 940 is triggered 939, initiating an open-loop timing adjustment 940 by advancing a symbol timing 951 for transmission of the uplink data 923 to the BS 103 by a pre-defined amount of time τ .

The method 900a may further include: repeating 930, g the random selection of a subset of the physical resource within the pre-defined physical channel 701 , 702, 703, 801 , 803 and the transmission of the uplink data 923 using the advanced symbol timing 951 for transmission of the uplink data 923 to the BS 103.

The original symbol timing 951 may be a maximum number of retransmissions R times a transmission time interval (TTI), i.e. a time interval required for one transmission. The advanced symbol timing 951 may be the original symbol timing 951 reduced by a predefined amount of time τ .

The pre-defined physical channel 701 , 702, 703, 801 , 803 may include physical resources, e.g. physical time-frequency resources as described above with respect to Figures 7 and 8 which allow for grant-free and TA-free uplink data transmission. The pre- defined physical channel 701 , 702, 703, 801 , 803 may be a grant-free access channel (GFACH) as introduced in this disclosure.

The configuration information 914 may include a size or transmission scheme of the predefined physical channel 701 , 702, 703, 801 , 803, for example a physical resource, e.g. a physical time-frequency resource as described above with respect to Figures 7 and 8, modulation and coding schemes, a maximum payload size, a number of allowed retransmissions etc.

In the following section a further implementation of the method 900a is described. For this implementation it may be assumed that there is a misalignment between downlink synchronization and uplink timing. Before the random access procedure 900a starts, downlink (DL) synchronization is established. This includes two aspects, namely the carrier frequency of the UE is tuned according to that of the base station and the downlink timing is acquired at the UE. Due to the propagation delays that the signals take to arrive at all UEs at different positions in the cell, the UE individual timings are not aligned. The maximum misalignment of the UE individual timing within a cell may be determined by the cell radius r, more precisely ^θπιαχ = ^r/^c _> with c denoting the speed of light.

In a TA-free transmission, a UE 101 , 102 does not adjust its uplink timing and simply starts uplink transmission following its individual timing. Thus, the uplink timing

misalignment, also known as uplink asynchronicity, at the base station 103 may sum up to

In a first step 910, a, the UE 101 , 102 establishes downlink synchronization to the primary cell and obtains the GFACH configuration information 914 by decoding the broadcast channel 912, 913. The configuration information 914 may include the GFACH resource allocation and transmit parameters.

In a second step 910, b, upon the arrival of UL data, a UE 101 , 102 checks the conditions, e.g. UE capability, service category, latency requirement of the traffic, payload size, availability of GFACH in the current cell, etc. and determines if a TA-free and grant-free transmission can be carried out. In case that the UE supports single service type with certain pre-defined requirement, e.g., a sensor, a TA-free and grant-free transmission may start directly.

In a third step 920, c, the UE 101 , 102 initiates a TA-free grant-free transmission on selected, e.g. randomly selected resource within GFACH 701 , 702, 703, 801 , 803. A transport block 921 , 923 consists of the data payload. It is assumed that a certain UE identifier is included in the payload.

In a fourth step 920, d, the BS 103 decodes the received GFACH transport blocks 921 , 923 and feedbacks ACK 927 or NACK 928 over the Physical Hybrid-ARQ Indicator Channel (PHICH). If the BS cannot decode, no feedback message is sent. In a fifth step 930, f, if a UE 102 receives an ACK 927, the TA-free and grant-free transmission is completed successfully. If a UE 101 receives a NACK 928, steps 910, b, 920, c and 920, d are repeated 930 until either an ACK 927 is received or the maximum number of retransmission R is reached.

Upon R times unsuccessful grant-free transmission, the UE 101 assumes itself out of sync and triggers 939 an open-loop timing adjustment 940 by advancing its symbol timing 951 by a pre-defined amount τ. Steps 920, c and 920, d are carried out again.

Fig. 10 shows a schematic diagram illustrating a method for performing a random access procedure 900b according to a second variant.

Steps 910, a, 910, b, 920, c, 920, d, 920, e and 930, f remain the same as in variant 1 described above with respect to Fig. 9. However, upon R times unsuccessful GF transmission, a close-loop TA procedure 960 is activated. Hence, the method 900b may further include: if the timing adjustment and synchronization procedure 960 is triggered 959, starting a closed-loop timing adjustment 960 by initiating a contention based random access procedure 960, g. The contention based random access procedure 960, g may include: randomly selecting a preamble 961 that corresponds to transmission over a Physical Random Access Channel (PRACH) 962. The contention based random access procedure 960 may correspond to the procedure 300 as described above with respect to Fig. 3.

For both variants 900a, 900b, the number of retransmissions R may be a parameter to be determined by the base station. The base station may adjust this parameter according to the traffic load on its GFACH.

Fig. 1 1 shows an amplitude over time diagram 1 100 illustrating different exemplary pulse shapes used for testing the random access procedures 900a and 900b. The first pulse 1 101 is a long pulse example. The second pulse 1 102 is a CP-OFDM transmit pulse. The third pulse 1 103 is a CP-OFDM receive pulse.

The requirement of uplink synchronization in LTE is down-to-earth determined by the waveform design adopted by the physical layer, namely, cyclic prefix orthogonal frequency division multiplexing (CP-OFDM). A CP-OFDM system is able to accommodate time misalignment within the CP range, although the CP is designed mainly to combat the channel time dispersion. Since the longer the CP is, the lower the system spectral efficiency, a typical CP-OFDM system is designed so that the maximum excess delay spread can be fully covered by the CP, while leaves accurate symbol timing to be acquired before the transmission starts.

In order to support grant-free and TA-free accesses, new waveform which allows asynchronous uplink transmission may be desired. In this example, pulse-shaped OFDM (P-OFDM) is considered as the physical layer technique. Given pulse shaping as an additional degree of freedom, the system can be adapted to the corresponding scenario. For example, by extending the pulse duration in the time domain, a pulse-shaped OFDM system becomes more robust against timing synchronization errors. In this example, pulse shapes are employed and link level performance is evaluated as well as the system level performance using the disclosed random access procedure.

Fig. 12 shows a performance diagram 1200 illustrating block error ratio (BLER) over SNR for different OFDM configurations. The first curve 1201 shows a BLER versus SNR performance for a pulse-shaped OFDM MCS25 configuration. The second curve 1202 shows a BLER versus SNR performance for an OFDM MCS25 configuration. The third curve 1203 shows a BLER versus SNR performance for a pulse-shaped OFDM MCS16 configuration. The fourth curve 1204 shows a BLER versus SNR performance for an OFDM MCS16 configuration. The fifth curve 1205 shows a BLER versus SNR performance for a pulse-shaped OFDM MCS9 configuration. The sixth curve 1206 shows a BLER versus SNR performance for an OFDM MCS9 configuration. The seventh curve 1207 shows a BLER versus SNR performance for a pulse-shaped OFDM MCS4 configuration. The eighth curve 1208 shows a BLER versus SNR performance for an OFDM MCS4 configuration.

The numerology of LTE for CP-OFDM is used and that with the same spectral efficiency for the pulse shaped OFDM. Meanwhile, the pilot structure, transceiver algorithms for equalization and channel estimation remain the same for the both OFDM schemes. A detailed simulation parameter setting is given in Table 1 . Table 1: simulation parameters

Parameter Value

System bandwidth 3 MHz

Duplex FDD UL

Subcarrier spacing 15 KHz

1 1.07

CP duration 4.7 μ s

Antenna Configuration 1 Tx at UE, 4 Rx at BS

User configuration 2 UE

P B allocation 15 PRBs to one UE

Channel estimation Least squares

MCS LTE MCS 4, % 16, 25

Hybrid ARQ Not modelled

Receiver LMMSE

Channel models LiTU 3 kni/li, uncorrelated MEMO links

Timing iiiisaligiirnent (open loop) 0 ~

Cell radius R, 2 km

A non-orthogonal multiple access scenario is considered where two UEs access the same frequency resource simultaneously. There are single antenna employed at the UE side and two antenna employed at the BS station side, namely a space-division multiple access (SDMA) configuration. The block error ratio (BLER) results are depicted in Fig. 12.

Given a CP length of 4.7μ8, the timing misalignment up to 13.3μ8 cannot be fully accommodated. Since the symbols in a pulse-shaped OFDM system are shaped with the long pulse 1 101 shown in Figure 1 1 , each symbol spreads four times as long as those in CP-OFDM. This leads to better robustness against timing misalignment for all simulated MCSs.

As performance baseline, the state-of-the-Art LTE FDD setup of 5MHz system bandwidth, with the orthogonal design, namely only a single UE is allowed to access one resource block, is considered. For comparison, physical layers based on CP-OFDM and on P-

OFDM are considered. For both cases, grant-free and TA-free transmission is allowed. On the receiver side, an enhanced receiver design which allows four times overloading is employed. Simulations are carried out for three mobility settings, namely 3km/h, 12km/h and 30km/h. The results in terms of maximum number of connections, 1^st shot grant-free connection success rate as well as the net connection numbers are evaluated. Table 2 system level simulation results for one-shot grant-free access

In Table 2, it can be observed that the P-OFDM with non-orthogonal access offers higher one-shot success rate for all three mobility scenarios. The gain is more significant in medium high velocity case (30km/h). Correspondingly, the number of successful connections in the first shot is nearly four times as that for the state-of-the-art orthogonal design. Further analysis shows that thanks to the grant-free random access, access latency can be reduced by 18 ms in comparison to LTE.

The present disclosure also supports a computer program product including computer executable code or computer executable instructions that, when executed, causes at least one computer to execute the performing and computing steps described herein, in particular the steps of the methods 500, 900a, 900b described above. Such a computer program product may include a readable non-transitory storage medium storing program code thereon for use by a computer. The program code may perform the performing and computing steps described herein, in particular the methods 500, 900a, 900b described above. A computer program may include program code for performing the methods 500, 900a, 900b as described above with respect to Figures 5 and 9 when executed on a computer.

While a particular feature or aspect of the disclosure may have been disclosed with respect to only one of several implementations, such feature or aspect may be combined with one or more other features or aspects of the other implementations as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the terms "include", "have", "with", or other variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term "comprise". Also, the terms "exemplary", "for example" and "e.g." are merely meant as an example, rather than the best or optimal. The terms "coupled" and "connected", along with derivatives may have been used. It should be understood that these terms may have been used to indicate that two elements cooperate or interact with each other regardless whether they are in direct physical or electrical contact, or they are not in direct contact with each other.

Although specific aspects have been illustrated and described herein, it will be

appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific aspects shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific aspects discussed herein.

Although the elements in the following claims are recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence.

Many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the above teachings. Of course, those skilled in the art readily recognize that there are numerous applications of the invention beyond those described herein. While the present invention has been described with reference to one or more particular embodiments, those skilled in the art recognize that many changes may be made thereto without departing from the scope of the present invention. It is therefore to be understood that within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described herein.

Claims

CLAIMS:

1 . A method (900a, 900b) for establishing data transmission over a predefined physical channel, the method comprising: broadcasting, by a base station (BS) (103), configuration information of a predefined physical channel wherein the configuration information (914) comprises physical resource allocation and transmit parameters; receiving (910, a), by a user equipment, (UE) (101 , 102), the configuration information (914) via a downlink broadcast channel (912, 913) from the base station (BS) (103); determining (910, b), by the UE (101 , 102), whether the UE (101 , 102) is qualified for transmission based on the received configuration information (914) and given capabilities of the UE (101 , 102); and if the UE (101 , 102) is qualified for the transmission, selecting (920, c), by the UE (101 , 102), a subset of the physical resource (701 , 702, 703, 801 , 803) within the predefined physical channel and transmitting uplink data (921 , 923) to the BS (103) on the selected subset of the physical resource.

2. The method (900a, 900b) of claim 1 , wherein the uplink data (921 , 923) comprises signaling information and payload data, wherein the payload data comprises an identifier of the UE.

3. The method (900a, 900b) of claim 1 or 2, wherein determining (910, b), by the UE (101 , 102), whether the UE (101 , 102) is qualified for the transmission comprises: evaluating a UE category tag or a UE configuration which indicate whether the UE is qualified for the transmission.

4. The method (900a, 900b) of one of the preceding claims, wherein the transmission comprises grant-free and timing-adjustment (TA)-free data transmission.

5. The method (900a, 900b) of one of the preceding claims, comprising: receiving feedback information (927, 928) for the transmitted uplink data (921 , 923) from the BS (103); indicating a successful data transmission if the feedback information comprises an acknowledgement (ACK) (927); repeating the selection (920, c) of a subset of the physical resource (700, 800) within the pre-defined physical channel (701 , 702, 703, 801 , 803) and the transmission of the uplink data (923) on the selected subset of the physical resource if the feedback information comprises a non-acknowledgement (NACK) (928) or no feedback is received; repeating (930, f) the random selection (920, c) of a subset of the physical resource within the pre-defined physical channel (701 , 702, 703, 801 , 803) and the transmission of the uplink data (923) until either feedback information comprising an ACK (927) is received or a given number of retransmissions, in particular a number of retransmissions configured by the BS (103), is reached; and if the given number of retransmissions is reached, triggering (939, 959) a timing adjustment and synchronization procedure (940, 960).

6. The method (900a, 900b) of one of the preceding claims, comprising: if a timing adjustment and synchronization procedure (940) is triggered (939), initiating an open-loop timing adjustment (940) by advancing the timing (950) for transmission of the uplink data (923) to the BS (103) by a pre-defined amount of time ( τ ); and repeating (930, f) the random selection of a subset of the physical resource within the pre-defined physical channel (701 , 702, 703, 801 , 803) and the transmission of the uplink data (923) using the advanced symbol timing (951 ) for transmission of the uplink data (923) to the BS (103).

7. The method (900a, 900b) of claim 5 or 6, comprising: if the timing adjustment and synchronization procedure (960) is triggered (959), starting a closed-loop timing adjustment (960) by initiating a contention based random access procedure (960, g).

8. The method (900a, 900b) of one of the preceding claims, wherein the pre-defined physical channel (701 , 702, 703, 801 , 803) comprises physical resources which allow for grant-free and TA-free uplink data transmission.

9. The method (900a, 900b) of one of the preceding claims, wherein the configuration information (914) comprises a size and allocation and transmission scheme of the pre-defined physical channel, in particular at least one of a physical resource (700, 800), modulation and coding schemes, a maximum payload size and a number of allowed retransmissions.

10. A data transmission device (600) for a user equipment (UE) for establishing transmission over a predefined physical channel, the data transmission device (600) comprising: a receive module (601 ), configured to receive configuration information (604) via a downlink broadcast channel (602) from a base station (BS), wherein the configuration information (604) comprises physical resource allocation and transmit parameters of the predefined physical channel; a determination module (603), configured to determine whether the UE is qualified for transmission based on the received configuration information (604) and given capabilities of the UE; and a transmission module (605), configured to select a subset of the physical resource within the pre-defined physical channel and to transmit uplink data (608) to the BS on the selected subset of the physical resource, if the UE is qualified (606) for the transmission.

1 1 . The data transmission device (600) of claim 10, wherein the transmission comprises grant-free and timing-adjustment (TA)-free data transmission.

12. A radio cell, comprising: a decision module configured to determine configuration information (604) of a predefined physical channel, wherein the configuration information (604) comprises physical resource allocation and transmit parameters of the predefined physical channel; and a broadcast transmission module configured to broadcast the configuration information via a downlink broadcast channel (912, 913) to at least one UE for establishing data transmission with the at least one UE over the predefined physical channel (701 , 702, 703, 801 , 803).

13. The radio cell of claim 12, wherein the pre-defined physical channel (701 , 702, 703, 801 , 803) comprises physical resources which allow for grant-free and TA-free uplink data transmission.

14. A transmission system, comprising: a user equipment (UE) comprising a data transmission device according to claim 10 or 1 1 ; and a radio cell according to claim 12 or 13, wherein the transmission system is configured to establish data transmission between the UE and the radio cell over the predefined physical channel.

15. A computer program comprising program code for performing the method (900a, 900b) of one of claims 1 to 9 when executed on a computer.