WO2019192411A1

WO2019192411A1 - Control and data transmission

Info

Publication number: WO2019192411A1
Application number: PCT/CN2019/080725
Authority: WO
Inventors: Umer Salim; Bruno Jechoux; Sebastian Wagner
Original assignee: Jrd Communication (Shenzhen) Ltd
Priority date: 2018-04-06
Filing date: 2019-04-01
Publication date: 2019-10-10
Also published as: GB2572646B; CN112005518B; GB201805790D0; CN112005518A; GB2572646A

Abstract

Methods for the transmission of data and control information, in which resources in which transmissions may be expected are pre-defined. Messages may be transmitted in the pre-defined regions and decoded at the receiver. The messages may include both control information and data.

Description

Control and Data Transmission

Technical Field

The following disclosure relates to the transmission of downlink data, and particularly to systems for improving the efficiency of downlink communications.

Background

Wireless communication systems, such as the third-generation (3G) of mobile telephone standards and technology are well known. Such 3G standards and technology have been developed by the Third Generation Partnership Project (3GPP) . The 3 ^rd generation of wireless communications has generally been developed to support macro-cell mobile phone communications. Communication systems and networks have developed towards a broadband and mobile system.

In cellular wireless communication systems User Equipment (UE) is connected by a wireless link to a Radio Access Network (RAN) . The RAN comprises a set of base stations which provide wireless links to the UEs located in cells covered by the base station, and an interface to a Core Network (CN) which provides overall network control. As will be appreciated the RAN and CN each conduct respective functions in relation to the overall network. For convenience the term cellular network will be used to refer to the combined RAN &CN, and it will be understood that the term is used to refer to the respective system for performing the disclosed function.

The 3rd Generation Partnership Project has developed the so-called Long Term Evolution (LTE) system, namely, an Evolved Universal Mobile Telecommunication System Territorial Radio Access Network, (E-UTRAN) , for a mobile access network where one or more macro-cells are supported by a base station known as an eNodeB or eNB (evolved NodeB) .More recently, LTE is evolving further towards the so-called 5G or NR (new radio) systems where one or more cells are supported by a base station known as a gNB. NR is proposed to utilise an Orthogonal Frequency Division Multiplexed (OFDM) physical transmission format.

A trend in wireless communications is towards the provision of lower latency and higher reliability services. For example, NR is intended to support Ultra-reliable and low-latency communications (URLLC) . A user-plane latency of 1ms has been proposed with a reliability of 99.99999%) . Other types of services to be provided include enhanced Mobile BroadBand (eMBB) for high data rate transmission, and massive Machine-Type Communication (mMTC) to support a large number of devices over a long life-time with highly energy efficient communication channels.

Communications over the physical wireless link are defined by a number of channels, for example the Physical Downlink Control Channel (PDCCH) which is used to transmit control information, in particular Downlink Control Information (DCI) , which defines how data will be transmitted to the UE over the Physical Downlink Shared Channel (PDSCH) . Successful reception of data at a UE requires the reception and decoding of the PDCCH and the PDSCH channels.

DCI in PDCCH carries scheduling and control information relevant for data (PDSCH) . Scheduling information primarily indicates to UE which time-frequency resources are allocated for its relevant data (PDSCH) transmission. The control information in DCI for downlink transmission comprises of other necessary parameters which enable the UE to decode the scheduled data. These parameters may include the modulation, coding scheme, Hybrid- automatic-repeat-request related parameters and the parameters related to uplink response for example.

The DCI is a specific message defined for NR in TS 38.212 and is carried on the PDCCH channel. As defined in Section 7.3 of TS 38.212, DCI transports downlink and uplink scheduling information, requests for aperiodic CQI reports, or uplink power control commands for one cell and one RNTI.

The following terminology is commonly utilised in relation to downlink physical channels, and in particular the PDCCH. The specific examples are in relation to NR, but the principles are applicable to other physical channel protocols.

A resource block (RB) is the smallest unit of time/frequency resources that can be allocated to a user. The resource block is x-kHz wide in frequency and 1 slot long in time. The number of subcarriers used per resource block for PDCCH is 12 and the exact value x depends on the subcarrier spacing (x=12＊SCS) which can be 15 kHz, 30 kHz, 60 kHz, etc. In terms of time, the default slot duration in NR is 14 OFDM symbols but there is also mini-slot duration possible (e.g. 1, 2, 3, up to 13 OFDM symbols) . The exact time duration of a slot in milliseconds (ms) depends on the consisting number of OFDM symbols and on SCS, e.g. for 15 kHz SCS and 14 OFDM symbols, 1 slot is 1ms long.

A resource-element group (REG) equals one RB during one OFDM symbol.

A control-channel element (CCE) consists of 6 REGs.

A PDCCH consists of one or more CCEs (e.g. L∈ {1, 2, 4, 8} ) . This number is defined as the CCE aggregation level (AL) .

For PDCCH blind decoding, the set of ALs and the number of PDCCH candidates per CCE AL per DCI format size that the UE monitors can be configured.

For each serving cell, each UE is configured with a number of control resource sets (CORESETs) to monitor for PDCCH. Each CORESET is defined by: starting OFDM symbol, time duration (consecutive symbols, up to 3) , set of RBs, CCE-to-REG mapping (and REG bundle size in case of interleaved mapping) .

B consecutive REGs in time (and frequency, in case B is larger than the size of CORESET in symbols) form a REG bundle.

The distributed resource mapping is realised by interleaving and the interleaving is operated on the REG bundles. In case of non-interleaved CCE-to-REG mapping, B=6.

In case of interleaved CCE-to-REG mapping, B∈ {2, 6} for 1 or 2 symbol CORESET, B∈ {3, 6} for 3 symbol CORESET.

A PDCCH search space at CCE AL L is defined by a set of PDCCH candidates for this CCE AL.

Cellular wireless communication systems commonly utilise HARQ-based protocols to improve reliability, but at the cost of increasing latency. Meeting the latency requirements of URLLC services with a HARQ protocol for PDCCH and PDSCH is challenging, and new approaches to the transmission of those channels may be required.

3GPP defines generally the term “reliability” in TR 38.802 as the success probability R of transmitting X bits within L seconds. L is the time it takes to deliver a small data packet from the radio protocol layer 2/3 SDU ingress point to the radio protocol layer 2/3 SDU egress point of the radio interface, at a certain channel quality Q (e.g., coverage-edge) .

The latency bound L includes transmission latency, processing latency, retransmission latency (if any) , and queuing/scheduling latency (including scheduling request and grant reception if any) .

It is also noted in that document that spectral efficiency should be considered when trying to achieve a reliability target.

Regarding reliability target for the URLLC scenario, NR considers in TR 38.913 that “A general URLLC reliability requirement for one transmission of a packet is (1-10 ^-5) for 32 bytes with a user plane latency of 1ms. ”

Considering a normal one-shot transmission (i.e. no HARQ retransmissions or repetitions) , the reliability R can be given by the following equation.

R=R _cR _d

where R _c and R _d denote the probability of successful PDCCH and PDSCH transmission, respectively. For simplicity, negligible effect of false-alarm probability is assumed (i.e. error due to falsely valid PDCCH detection by the UE while there is no DCI transmission) . Large enough CRC (e.g. 24 bits) , when coding the DCI, can achieve this.

Inversely, the probability of erroneous packet transmission P (=1-R) is given by:

P=1- (1-P _c) (1-P _d)

where P _c and P _d denote the probability of erroneous PDCCH and PDSCH transmission, respectively.

Thus, the NR reliability target (＞99.999%reliability or, inversely, ＜0.001%error probability) can be achieved for example with a combination of channels’ error probabilities such as P _c=8·10 ^-6and P _d=2·10 ^-6, etc.

In case of multi-shot transmission, several additional factors control the reliability of the transmission. For example, assuming no HARQ combining, for a conventional two-shot transmission the reliability can be given by:

R=R _cR _d1+ (1-R _c) R _DTXR _cR _d2+R _c (1-R _d1) R _NR _cR _d2

where R _d1 and R _d2 denote the probability of successful initial PDSCH transmission and PDSCH retransmission, respectively; R _DTX denotes the probability of gNB detecting DTX or NACK, when UE “sends” DTX (i.e. does not send anything) in UL; R _N denotes the probability of gNB detecting DTX or NACK, when UE sends NACK.

On the right hand side of the equation above, the first term of the summation regards the successful receipt of initial transmission, the second term regards the successful receipt of retransmission in case PDCCH detection fails, and the third term regards the successful receipt of retransmission in case the initial PDSCH decoding fails.

There are many ways of improving the reliability of control channel transmissions, but these may involve the utilisation of greater transmission resources. It is possible that insufficient control channel resources are available to schedule transmissions to fully utilise data transmission capacity and hence such data transmission capacity may go unused leading to inefficient use of resources.

Multi-shot transmission with or without adaptive HARQ can improve the reliability but this can be limiting under latency constraints. Under heavy traffic situations combined with strict latency requirements, it is quite possible that the network has to do its best with single shot transmission to meet the latency and the reliability at the same time.

For PDCCH design, when the network realises that a user is not able to properly decode the control information, it generally increases the aggregation level. Increasing the aggregation level means using more resources to encode the control information which results in decreasing the code rate and thus making the transmission more robust to errors. The use of higher aggregation level consumes a lot of resources and this would result in unavailability of control resources for other users.

Figure 1 shows a schematic diagram of transmission resources in an OFDM transmission system. Each slot 100 is split into a control region 101 and a data region 102. The control region is utilised to transmit control information, for example PDCCH, to schedule transmission of the PDSCH channel 103 in the data region 102 of the slot.

URLLC services are commonly utilised for the transmission of small data packets at unpredictable intervals. The transmission of a control message to schedule each data packet requires significant resources and the control overhead can become comparable to the size of the data being transmitted. This is an inefficient use of resources. Furthermore, the transmission of control information followed later by the data adds latency to the communication channel, particularly if retransmission is required to achieve required reliability levels.

The present invention is seeking to solve at least some of the outstanding problems in this domain.

Summary

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

There is provided a method of transmitting data from a base station to a user equipment (UE) in a wireless cellular communications network, the wireless link utilising an OFDM transmission format, the method comprising the steps of at a base station allocating a resource region in an OFDM slot for the transmission of a combined data and control information message; transmitting an indication of the allocated resource region to a UE; and transmitting a combined data and control information message comprising a data part and a control part to the UE in the allocated resource region.

The indication of the allocated resource region may further comprise the periodicity with which this resource region repeats.

The allocated resource region may have full or partial overlap with a control region of the OFDM slot.

The indication of the allocated resource region may further comprise information defining the transmission format of the combined data and control information message.

The indication of the allocated resource region may be transmitted in an RRC message.

The combined data and control information message may comprise an indication of resources in the data region of the OFDM slot for a subsequent transmission of the data transmitted in the combined data and control information message.

The subsequent transmission may utilise the same frequency resources as the transmission of the combined data and control information message.

The data part of the combined transmission may be of a predefined length.

The method may further comprise the step of padding data for transmission to match the predefined length.

The predefined length may be selected from a plurality of predefined lengths.

The base station may transmit the combined control and data information message for a UE over a subset of resources in the allocated resource region.

A pre-defined rule known to both the base station and the UE may be utilized to select the subset of resources.

The rule may use as inputs at least one of the UE ID, slot number, sub-frame number and the size of the allocated resource region.

There is also provided a method of receiving data from a base station at a user equipment (UE) in a wireless cellular communications network, the wireless link utilising an OFDM transmission format, the method comprising the steps of at a UE receiving an indication of a resource region in an OFDM slot in which a combined data and control information message may be received; receiving a combined data and control information message comprising a data part and a control part at the UE in the allocated resource region; and decoding the received combined data and control information message.

The indication of the allocated resource region may be received in an RRC message.

The combined data and control information message may comprise an indication of resources in the data region of the OFDM slot on which a subsequent transmission of the data transmitted in the combined data and control information message may be received.

Decoding the received subsequent transmission may utilise a DMRS signal utilised to decode the combined data and control transmission.

The data part of the combined transmission may be of a predefined length.

The predefined length may be selected from a plurality of predefined lengths.

There is provided a method of transmitting data from a base station to a user equipment (UE) in a wireless cellular communications network, the wireless link utilising an OFDM transmission format, the method comprising the steps of at a base station allocating a resource region in an OFDM slot for the transmission of a data message, wherein the allocated resource region has full or partial overlap with a control region of the OFDM slot; transmitting an indication of the allocated resource region to a UE; and transmitting a data message to the UE in the allocated resource region.

The indication of the allocated resource region may further comprise information defining the transmission format of the data message.

The data message may comprise an indication of resources in the data region of the OFDM slot for a subsequent transmission of the data transmitted in the data message.

The data message may be of a predefined length.

The predefined length may be selected from a plurality of predefined lengths.

The base station may transmit the data message for a UE over a subset of resources in the allocated resource region.

There is also provided a method of receiving data from a base station at a user equipment (UE) in a wireless cellular communications network, the wireless link utilising an OFDM transmission format, the method comprising the steps of at a UE receiving an indication of a resource region in an OFDM slot in which a data message may be received wherein the allocated resource region has full or partial overlap with a control region of the OFDM slot; receiving a data message in the allocated resource region at the UE; and decoding the received data message.

The data message may comprise an indication of resources in the data region of the OFDM slot on which a subsequent transmission of the data transmitted in the data message may be received.

The data message may be of a predefined length.

The predefined length may be selected from a plurality of predefined lengths.

The data message may be received over a subset of resources in the allocated resource region.

The non-transitory computer readable medium may comprise at least one from a group consisting of: a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a Read Only Memory, a Programmable Read Only Memory, an Erasable Programmable Read Only Memory, EPROM, an Electrically Erasable Programmable Read Only Memory and a Flash memory.

Brief description of the drawings

Further details, aspects and embodiments of the invention will be described, by way of example only, with reference to the drawings. Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. Like reference numerals have been included in the respective drawings to ease understanding.

Figure 1 shows transmission resources with conventional scheduling;

Figure 2 shows a flow chart of a method of data transmission; and

Figure 3 shows timing of transmissions.

Detailed description of the preferred embodiments

Those skilled in the art will recognise and appreciate that the specifics of the examples described are merely illustrative of some embodiments and that the teachings set forth herein are applicable in a variety of alternative settings.

As set out above, in conventional systems a control message is transmitted in a control region of a frame to schedule the later transmission of data in the data region of the frame (or a subsequent frame) . As well as scheduling information (time and frequency resources) , the control message includes parameters to be used for the transmission such as modulation format, coding scheme, HARQ process number, precoding etc., and details of resources relating to ACK/NAK transmission on the uplink.

As explained above UEs are configured to listen for a PDCCH channel including control information on pre-defined CORESET resources. Following receipt of a DCI message on PDCCH a UE receives a PDSCH transmission on the indicated resources and decodes it using the provided parameters. The separate control information and data transmission allows the base station to schedule transmissions according to current network requirements, and minimises the resources each UE is required to monitor (as each UE only has to monitor its allocated CORESET for a DCI message, not all possible locations of data) .

Figure 2 shows a method for transmitting control and data from a base station to a UE over a wireless link in a cellular communication network.

At step 20 a base station allocates a resource region in a slot which may be utilised for the transmission of a combined control and data message. Such a combined message includes both data for the UE, and control information relating to that data. The configuration of the resource region includes the periodicity with which this region repeats. Furthermore this resource region may be inside the control region or independent. Thus, the allocated resources may be a CORESET, or other set of resources. With a pre-defined rule known to both the base station and the UE, there is a set of possible resources in this region to transmit the combined control and data message. An example rule is the rule which defines the allowed control resources (Control channel elements) used to transmit PDCCH for a specific UE within a CORESET. That is resources within the resource region may be selected in the same as resources may be selected for transmission of PDCCH. Other rules may be defined using one or more parameters like UE ID, slot number etc which define the transmission opportunities for a specific UE within the resource region.

At step 21 the base station transmits an indication of the allocated resource region to the UE. For example, this transmission may be an RRC message. The indication of resource region may also include some of the details that would normally be included in a control transmission defining the format of the subsequent data transmission; for example modulation format, coding scheme, HARQ process number, precoding etc., and details of resources relating to ACK/NAK transmission on the uplink. All of the transmission details do not need to be defined within this indication message. Many of the transmission parameters may be known a-priori to both the base station and the UE, for example by defining in the specification.

At step 22, upon receipt of the indication of resources, the UE configures itself to listen on the indicated resource region for a message transmitted with the indicated characteristics. At step 23, when data is ready to send, the base station transmits the data in a message in the indicated resource region, using the pre-defined parameters. This message is sent on one resource possibility within the configured resource region according to the pre-defined rule which identifies the set of transmission possibilities within the region. The message transmitted by the base station includes any control data required by the UE, as well the data. That is, a combined control information and data message is transmitted in the configured region of the slot. The rule to identify the resource used for transmission within the resource region may use one or more UE specific parameters, namely UE ID or connection RNTI. It may also use some system parameters, like size of the configured resource region, slot number, sub-frame number, and frame number. With this pre-defined rule, both the base station and the UE may determine a one or more of the resource sets where the combined control and data message may be transmitted to the UE. The advantage of using these parameters is to randomize the transmission resource sets within the configured region for every UE and for every transmission occasion. This mechanism may be similar to what is used for the conventional control transmission (PDCCH) to determine which resource sets can be used to transmit control information to a specific UE in a specific CORESET.

At step 24 the UE is listening in the indicated resource region over the transmission possibilities defined by the known rule. It checks all these possible resource allocations within the configured resource region and receives and decodes the message to recover the data. The required data is thus transmitted to the UE in a single message (in the control region) , thereby reducing latency. Control overheads are reduced because many of the parameters that would previously have been sent for each message are either configured by the indication of resources message or are fixed to specific values and thus do not need to be transmitted for every data transmission. Also, since the data is transmitted in the pre-configured resource region with control message, no scheduling information is required thus reducing the overhead further. Furthermore, CRC overhead is reduced. Conventionally CRC bits are added to both the control and data messages, but in this example only one set of CRC bits are required as there is only a single message.

The combined transmission allows efficient use of demodulation reference symbols (DMRS) to prepare better quality channel estimates compared to individual control and data transmission. As the typical setting here is the transmission of small packets with higher reliability requirement, the individual transmissions may need a certain density of DMRS in each transmission to ensure good quality channel estimates. Due to even smaller combined control and data information, the combined transmission may get better channel estimates for a given DMRS overhead. Stated the other way round, for a given quality of channel estimates the DMRS overhead of the combined transmission may be reduced compared to classical control and data transmissions.

In a variation of the method of Figure 2, the control and data message in the control region may also include scheduling information for a data transmission in the data region of the frame (or later frame) . This later data transmission may be utilised for the re-transmission of the data sent in the control region in order to improve the transmission reliability. Control overheads may still be reduced by the pre-configuration, and latency is also improved together with improved quality of service as two transmissions of the data can be achieved in a shorter time.

In another method, if the data repetition which follows the combined control and data transmission is scheduled on the same frequency resources, the UE may reuse the DMRS of first combined transmission to obtain and improve the channel estimates for the data repetition (PDSCH) . This may impose some restrictions on the antenna configuration of the PDSCH transmission. The antenna configuration (and beamforming used if any) to transmit PDSCH should be such that the channel estimates may be derived from the channel estimates of the combined transmission.

The use of combined data and control information transmission may increase the number of blind decodes the UE must perform. In order to limit the number of blind decodes parameters relating to the transmission may be fixed in advance by the indication of resources, or only a subset of possible options may be utilised to limit the number of tests the UE has to perform.

In conventional systems, a UE listens to pre-configured control resources to receive a DCI message indicating that a data transmission is scheduled. In the search space within the control region, the UE has to do multiple blind decodes to find its relevant PDCCH. The multiple blind decodes result from the following factors:

· There are multiple positions within the control resources where PDCCH for a certain UE can be mapped.

· There are multiple aggregation levels associated to DCIs and one of the these could be employed by the gNB to send the PDCCH.

· A UE may be configured to listen to multiple DCIs of different sizes.

Thus for all of the above possibilities, including for each different size of DCI, the UE needs to do separate blind decodes. This is acceptable for control only transmission as UE is pre-configured with a set of DCIs to which it should listen to in control occasions, thus for most users, they would know a limited set of DCI sizes to which they are configured to and can receive the corresponding DCIs. However, for a combined control information and data transmission, the data size may not always be known in advance by the UE. If the user has to do multiple blind decodes, say to accommodate the data length ranging from N1 to N2 where for example N1=10 bits and N2=60 bits and each integer length falling in this range is a valid data size, this will result in large blind decoding burden. In this case, there are N2-N1 (50) blind decodes due to length, this will get multiplied by the possible number of aggregation levels and their placement in the time-frequency resource. Thus, the blind decoding burden may quickly render the combined transmission impractical from UE complexity perspective.

In order to manage the number of blind decodes a threshold may be defined for the data size which may be transmitted in a combined message. That is, the data part of the combined message may be limited to a certain size. Furthermore, if there are fewer bits of data than the threshold, the data may be packed with filler bits to the threshold. This enables the size of the data to be predefined and thus the UE has prior knowledge of the data length to minimise blind decoding tests. Although the transmission of filler or dummy bits will reduce somehow the advantage of combined transmission, the reduction in blind decodings may be important to make the combined transmission scheme practically feasible.

In a variation a set of predefined data sizes may be defined to provide increased flexibility but still limit the number of required blind decodes.

The possibility of combined data and control information transmission may be activated by the network, and may be done on a per-UE basis. The technique is principally applicable for URLLC type services where the data is small with strict latency requirements and is thus amenable to be transmitted in the control region. Activating on a per-UE basis avoids UEs unlikely to utilise this type of transmission to avoid the additional blind decoding burden.

As most of the transmission parameters required to decode the combined transmission are either fixed or configured for the UE as part of the configuration, the control information content in the combined control and data transmission may be very limited. In a variation of the proposed scheme, all of the control parameters are either fixed to specific values or a UE can determine them with a rule (using an equation for example) or are pre-configured with the resource configuration such that the base station does not need to send any control information with the data. Thus, the combined transmission only consists of data transmitted to the UE in the configured resource region. This way the data is transmitted alone without the need to transmit any dynamic control parameters. This will make these transmission highly resource efficient.

Figure 3 shows the latency-reliability of combined transmission compared to conventional transmissions where the data transmission follows the control transmission. Figure 3 (a) shows the legacy scheme where one symbol control resource is configured, followed by 2 symbols for data transmission for URLLC users. The URLLC packet arrives at the base station from higher layers at 30. Tw denotes the wait time before the packet gets scheduled. Tt denotes the total transmission time, including control and data. This is followed by the UE processing time and the time to send HARQ ACK/NAK in the UL direction, denoted by T_HARQ. T_HARQ is taken to be equal to 2 symbol times. Suppose the first transmission was not successful and the UE sent a NAK, the gNB makes a retransmission for the same packet after having received the NAK from the UE. Thus, in the interval portrayed by Figure 3 (a) above (of 12 OFDM symbols with a certain numerology) , the gNB can send the packet twice, i.e. one retransmission following the original transmission.

For the same resource duration, with combined transmission as shown in Figure 3 (b) , the target user is configured with resources where control and data can be transmitted in a single transmission. For the same amount of HARQ processing and uplink transmission time for ACK/NAK, one observes that the base station can make 3 transmissions of the data, i.e., 2 retransmissions following the original transmission.

The combined control and data leads to more efficient resource utilization for small data packets. In addition, with reference to Figure 3, combined transmission has two exploitation possibilities. If a specific reliability target needs a certain number of retransmissions, combined transmission provides a latency advantage, which also means that under heavy traffic conditions when a user cannot be served quickly, the increased scheduling wait times may be accommodated better by the combined transmission. Another advantage may be in terms of reliability. If the user’s channel conditions are quite poor such that it needs more retransmission within its latency target, the combined transmission will be able to have more retransmissions over a specific time interval compared to the conventional scheme. Thus, overall the combined transmission will allow the network to have a better percentage of users satisfying the reliability and latency bounds compared to the conventional scheme.

For the ease of exposition, Figure 3 shows the transmission occasions consisting of control and data part. NR allows simultaneous scheduling of slot-based data, non-slot-based data and the use of mini-slots for different users. Similarly, NR allows the network to use different numerologies over different time durations and different frequency intervals. We don’t go into the details of all such transmission possibilities but the idea of combined control and data transmission applies to all such transmission configurations.

Set out below are simulation results showing the potential impact of allowing combined control and data transmissions versus the conventional transmissions where data (PDSCH) is scheduled through control (PDCCH) .

For the normal transmission, the control information DCI is sent in PDCCH. The code rates for Polar codes which result in a certain block error rate at a fixed SNR have been computed, and then with this how many coded bits will be transmitted is computed. In these coded bits, the DMRS overhead of PDCCH is added which is every 4th PDCCH resource element in all resource blocks used for PDCCH. The data transmission also follows the normal PDSCH transmission with DMRS configuration Type 1 in its first symbol which bears a 50%resource overhead in the front loaded DMRS symbol. Both control and data use 24-bit CRC in these simulation results.

For the combined control and data transmission, the total information bits (combined data and control) are transmitted with Polar code and with PDCCH DMRS on every 4th resource element.

The control information size is taken to be 40 bits for the conventional transmission and the control data is assumed to be 20 bits for the combined control and data transmission. This due to the combined transmission not needing to schedule any resource in terms of frequency PRBs and the OFDM symbols. Similarly, MCS indication is not required for the combined transmission, rather it should be fixed or a set with limited possibilities which need to be checked through blind decodes. On top of that, the HARQ choices etc also need none or fewer bits compared to normal DCI. With all this, actually 20 bit used for the control of combined transmission is pessimistic for the proposed approach and in reality the control overhead can easily be reduced further for the combined transmission. The other advantage that helps optimize the payload for combined data and control is the presence of 24-bit CRC once.

If a transmission has to be operated at a BLER of 10^ (-N) , this would be the BLER of the combined control and data transmission. On the other hand, to ensure this BLER of 10^ (- N) for conventional scheme with data scheduled by the control transmission, as the reliability of the successful transmission is given by

P=P _c P _d

1-BLER= (1-BLER _c) (1-BLER _d)

BLER =BLER _c+BLER _d-BLER _cBLER _d

As BLER _cBLER _d is very small, it can be ignored to get

BLER =BLER _c+BLER _d

Thus, to ensure a BLER of 10^ (-N) with conventional transmission, both control and data should be operating with a BLER lower than 10^ (-N) , one example operating point would be 0.5x10^ (-N) for each of the control and data transmissions.

Table 1 shows the resource comparison needed to ensure a specific BLER of 10^ (-5) at SNR=-5dB for the two schemes, one for the classical transmission scheme where the data (PDSCH) follows the control information (PDCCH) and the one for the combined transmission of control and data is carried out in PDCCH. Each entry in the table shows the number of PRBs required to transmit a specific number of data information bits (mentioned on top of the column) for a specific transmission scheme (schemes are shown in the left most column) . In general, there are rules for PRB assignments so there is some granularity in real assignments but for simplicity of exposition, we show the minimum PRBs required without quantizing them. The channel model for the simulations and thus for the comparison below is TDL-A 10 n-sec at 3 Km/h with 2 Tx and 2 Rx antennas.

Table 1

The combined transmission sends the data in much the same way control information is transmitted in the classical scheme with DMRS overhead of 1/4 (standardized for 5G NR PDCCH) . For the conventional approach, the DMRS used are front-loaded in the first symbol. Thus, if it uses only a single symbol data, the DMRS overhead becomes very large. For this reason, the resource usage of conventional schemes is shown with 3 different data lengths, 1, 2 and 4 OFDM symbols used to carry PDSCH. As there is only one front-loaded DMRS symbol, the DMRS overhead is the largest for 1 symbol scheme and the lowest for 4 symbol scheme.

The resource consumption comparison shows the benefit of the combined transmission for small amount of information data packets. For 32-bit information data, the combined transmission uses 163 PRBs compared to 233 PRBs required by the conventional scheme with 4 data symbols. The conventional transmission with 2 and 1 data symbol use respectively 249 and 305 PRBs, making the communication even more inefficient.

For this channel model and operating point, the combined transmission and the conventional scheme become comparable at information data size of 200 bits where both are using 522 and 521 PRBs respectively. Below this size, the combined transmission shows better performance becoming more and more efficient as the information data size reduces.

Some of the advantage of the combined transmission for small packets comes from the efficient channel coding for small packets. As combined transmission uses the transmission strategy including channel coding as of the conventional control transmission, it uses polar coding. The polar coding used for PDCCH in NR has performance advantage for small packets compared to LDPC, whereas LDPC outperforms polar coding for larger packets. The proposed scheme, as it targets smaller packets, uses the polar coding for combined control and data transmissions and thus shows better results.

The above disclosure was mainly presented in the context of URLLC UEs, but the disclosure may also be useful for massive MTC devices. Most of the MTC devices will have small infrequent data transfer per device. In many cases, these data transfers may be periodic as well. Due to infrequent activity, the channel state information for these devices is not known at the base station so the base station will normally choose quite conservative transmission techniques to communicate with these devices. Furthermore, most of these devices are inexpensive devices so may not be able to perform sophisticated techniques anyways. 5G allows creation of CORESETs (resource for PDCCH) anywhere in the slot and the users may be configured to multiple user specific CORESETs. This will give base stations a lot of flexibility to create smaller CORESETS for groups of users (MTC devices) where they can receive their control information or combined control and data for example without having a lot of impact on PDCCH capacity. This would have been impossible in 4G LTE as PDCCH is sent only in the first 2 or 3 symbols of the slot and the capacity of PDCCH can become a blocking point very quickly. The base station may exploit the 5G flexible CORESET configurations to handle massive number of MTC devices with small data packets using the disclosure given herein.

As will be appreciated from the context, references herein to the transmission of “data” are to “user data” being carried on the downlink to the UE.

Although not shown in detail any of the devices or apparatus that form part of the network may include at least a processor, a storage unit and a communications interface, wherein the processor unit, storage unit, and communications interface are configured to perform the method of any aspect of the present invention. Further options and choices are described below.

The signal processing functionality of the embodiments of the invention especially the gNB and the UE may be achieved using computing systems or architectures known to those who are skilled in the relevant art. Computing systems such as, a desktop, laptop or notebook computer, hand-held computing device (PDA, cell phone, palmtop, etc. ) , mainframe, server, client, or any other type of special or general purpose computing device as may be desirable or appropriate for a given application or environment can be used. The computing system can include one or more processors which can be implemented using a general or special-purpose processing engine such as, for example, a microprocessor, microcontroller or other control module.

The computing system can also include a main memory, such as random access memory (RAM) or other dynamic memory, for storing information and instructions to be executed by a processor. Such a main memory also may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by the processor. The computing system may likewise include a read only memory (ROM) or other static storage device for storing static information and instructions for a processor.

The computing system may also include an information storage system which may include, for example, a media drive and a removable storage interface. The media drive may include a drive or other mechanism to support fixed or removable storage media, such as a hard disk drive, a floppy disk drive, a magnetic tape drive, an optical disk drive, a compact disc (CD) or digital video drive (DVD) read or write drive (R or RW) , or other removable or fixed media drive. Storage media may include, for example, a hard disk, floppy disk, magnetic tape, optical disk, CD or DVD, or other fixed or removable medium that is read by and written to by media drive. The storage media may include a computer-readable storage medium having particular computer software or data stored therein.

In alternative embodiments, an information storage system may include other similar components for allowing computer programs or other instructions or data to be loaded into the computing system. Such components may include, for example, a removable storage unit and an interface , such as a program cartridge and cartridge interface, a removable memory (for example, a flash memory or other removable memory module) and memory slot, and other removable storage units and interfaces that allow software and data to be transferred from the removable storage unit to computing system.

The computing system can also include a communications interface. Such a communications interface can be used to allow software and data to be transferred between a computing system and external devices. Examples of communications interfaces can include a modem, a network interface (such as an Ethernet or other NIC card) , a communications port (such as for example, a universal serial bus (USB) port) , a PCMCIA slot and card, etc. Software and data transferred via a communications interface are in the form of signals which can be electronic, electromagnetic, and optical or other signals capable of being received by a communications interface medium.

In this document, the terms ‘computer program product’ , ‘computer-readable medium’ and the like may be used generally to refer to tangible media such as, for example, a memory, storage device, or storage unit. These and other forms of computer-readable media may store one or more instructions for use by the processor comprising the computer system to cause the processor to perform specified operations. Such instructions, generally referred to as ‘computer program code’ (which may be grouped in the form of computer programs or other groupings) , when executed, enable the computing system to perform functions of embodiments of the present invention. Note that the code may directly cause a processor to perform specified operations, be compiled to do so, and/or be combined with other software, hardware, and/or firmware elements (e.g., libraries for performing standard functions) to do so.

The non-transitory computer readable medium may comprise at least one from a group consisting of: a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a Read Only Memory, a Programmable Read Only Memory, an Erasable Programmable Read Only Memory, EPROM, an Electrically Erasable Programmable Read Only Memory and a Flash memory

In an embodiment where the elements are implemented using software, the software may be stored in a computer-readable medium and loaded into computing system using, for example, removable storage drive. A control module (in this example, software instructions or executable computer program code) , when executed by the processor in the computer system, causes a processor to perform the functions of the invention as described herein.

Furthermore, the inventive concept can be applied to any circuit for performing signal processing functionality within a network element. It is further envisaged that, for example, a semiconductor manufacturer may employ the inventive concept in a design of a stand-alone device, such as a microcontroller of a digital signal processor (DSP) , or application-specific integrated circuit (ASIC) and/or any other sub-system element.

It will be appreciated that, for clarity purposes, the above description has described embodiments of the invention with reference to a single processing logic. However, the inventive concept may equally be implemented by way of a plurality of different functional units and processors to provide the signal processing functionality. Thus, references to specific functional units are only to be seen as references to suitable means for providing the described functionality, rather than indicative of a strict logical or physical structure or organisation.

Aspects of the invention may be implemented in any suitable form including hardware, software, firmware or any combination of these. The invention may optionally be implemented, at least partly, as computer software running on one or more data processors and/or digital signal processors or configurable module components such as FPGA devices. Thus, the elements and components of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way. Indeed, the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units.

Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the present invention is limited only by the accompanying claims. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognise that various features of the described embodiments may be combined in accordance with the invention. In the claims, the term ‘comprising’ does not exclude the presence of other elements or steps.

Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented by, for example, a single unit or processor. Additionally, although individual features may be included in different claims, these may possibly be advantageously combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. Also, the inclusion of a feature in one category of claims does not imply a limitation to this category, but rather indicates that the feature is equally applicable to other claim categories, as appropriate.

Furthermore, the order of features in the claims does not imply any specific order in which the features must be performed and in particular the order of individual steps in a method claim does not imply that the steps must be performed in this order. Rather, the steps may be performed in any suitable order. In addition, singular references do not exclude a plurality. Thus, references to ‘a’ , ‘an’ , ‘first’ , ‘second’ , etc. do not preclude a plurality.

Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the present invention is limited only by the accompanying claims. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognise that various features of the described embodiments may be combined in accordance with the invention. In the claims, the term ‘comprising’ or “including” does not exclude the presence of other elements.

Claims

A method of transmitting data from a base station to a user equipment (UE) in a wireless cellular communications network, the wireless link utilising an OFDM transmission format, the method comprising the steps of

at a base station allocating a resource region in an OFDM slot for the transmission of a combined data and control information message;

transmitting an indication of the allocated resource region to a UE; and

transmitting a combined data and control information message comprising a data part and a control part to the UE in the allocated resource region.
A method according to claim 1, wherein the indication of the allocated resource region further comprises the periodicity with which this resource region repeats.
A method according to claim 1 or claim 2, wherein the allocated resource region has full or partial overlap with a control region of the OFDM slot.
A method according to claim 1, wherein the indication of the allocated resource region further comprises information defining the transmission format of the combined data and control information message.
A method according to any preceding claim , wherein the indication of the allocated resource region is transmitted in an RRC message.
A method according to any preceding claim, wherein the combined data and control information message comprises an indication of resources in the data region of the OFDM slot for a subsequent transmission of the data transmitted in the combined data and control information message.
A method according to claim 6, wherein the subsequent transmission utilises the same frequency resources as the transmission of the combined data and control information message.
A method according to any preceding claim, wherein the data part of the combined transmission is of a predefined length.
A method according to claim 8, further comprising the step of padding data for transmission to match the predefined length.
A method according to claim 8 or claim 9 wherein the predefined length is selected from a plurality of predefined lengths.
A method according to any preceding claim, wherein the base station transmits the combined control and data information message for a UE over a subset of resources in the allocated resource region.
A method according to claim 11, wherein a pre-defined rule known to both the base station and the UE is utilized to select the subset of resources.
A method according to claim 12, wherein the rule uses as inputs at least one of the UE ID, slot number, sub-frame number and the size of the allocated resource region.
A method of receiving data from a base station at a user equipment (UE) in a wireless cellular communications network, the wireless link utilising an OFDM transmission format, the method comprising the steps of

at a UE receiving an indication of a resource region in an OFDM slot in which a combined data and control information message may be received;

receiving a combined data and control information message comprising a data part and a control part at the UE in the allocated resource region; and

decoding the received combined data and control information message.
A method according to claim 14, wherein the indication of the allocated resource region further comprises the periodicity with which this resource region repeats.
A method according to claim 14 or claim 15, wherein the allocated resource region has full or partial overlap with a control region of the OFDM slot.
A method according to claim 14, wherein the indication of the allocated resource region further comprises information defining the transmission format of the combined data and control information message.
A method according any of claims 14 to 17, wherein the indication of the allocated resource region is received in an RRC message.
A method according to any of claims 14 to 18, wherein the combined data and control information message comprises an indication of resources in the data region of the OFDM slot on which a subsequent transmission of the data transmitted in the combined data and control information message may be received.
A method according to claim 19, wherein the subsequent transmission utilises the same frequency resources as the transmission of the combined data and control information message.
A method according to claim 20, wherein the received subsequent transmission is decoded utilising a DMRS signal utilised to decode the combined data and control transmission.
A method according to any of claims 14 to 21, wherein the data part of the combined transmission is of a predefined length.
A method according to claim 22 wherein the predefined length is selected from a plurality of predefined lengths.
A method according to any of claims 14 to 23, wherein the combined control and data information message is received over a subset of resources in the allocated resource region.
A method according to claim 24, wherein a pre-defined rule known to both the base station and the UE is utilized to select the subset of resources.
A method according to claim 25, wherein the rule uses as inputs at leastone of the UE ID, slot number, sub-frame number and the size of the allocated resource region.
A method of transmitting data from a base station to a user equipment (UE) in a wireless cellular communications network, the wireless link utilising an OFDM transmission format, the method comprising the steps of

at a base station allocating a resource region in an OFDM slot for the transmission of a data message, wherein the allocated resource region has full or partial overlap with a control region of the OFDM slot;

transmitting an indication of the allocated resource region to a UE; and

transmitting a data message to the UE in the allocated resource region.
A method according to claim 27, wherein the indication of the allocated resource region further comprises the periodicity with which this resource region repeats.
A method according to claim 27, wherein the indication of the allocated resource region further comprises information defining the transmission format of the data message.
A method according to any of claims 27 to 29, wherein the indication of the allocated resource region is transmitted in an RRC message.
A method according to any of claims 27 to 30, wherein the data message is of a predefined length.
A method according to claim 31, further comprising the step of padding data for transmission to match the predefined length.
A method according to claim 31 or claim 32 wherein the predefined length is selected from a plurality of predefined lengths.
A method according to any of claims 27 to 33, wherein the base station transmits the data message for a UE over a subset of resources in the allocated resource region.
A method according to claim 34, wherein a pre-defined rule known to both the base station and the UE is utilized to select the subset of resources.
A method according to claim 35, wherein the rule uses as inputs at least one of the UE ID, slot number, sub-frame number and the size of the allocated resource region.
A method of receiving data from a base station at a user equipment (UE) in a wireless cellular communications network, the wireless link utilising an OFDM transmission format, the method comprising the steps of

at a UE receiving an indication of a resource region in an OFDM slot in which a data message may be received wherein the allocated resource region has full or partial overlap with a control region of the OFDM slot;

receiving a data message in the allocated resource region at the UE; and

decoding the received data message.
A method according to claim 37, wherein the indication of the allocated resource region further comprises the periodicity with which this resource region repeats.
A method according to claim 37, wherein the indication of the allocated resource region further comprises information defining the transmission format of the data message.
A method according any of claims 37 to 39, wherein the indication of the allocated resource region is received in an RRC message.
A method according to any of claims 37 to 40, wherein the data message is of a predefined length.
A method according to claim 41 wherein the predefined length is selected from a plurality of predefined lengths.
A method according to any of claims 37 to 42, wherein the data message is received over a subset of resources in the allocated resource region.
A method according to claim 43, wherein a pre-defined rule known to both the base station and the UE is utilized to select the subset of resources.
A method according to claim 44, wherein the rule uses as inputs at least one of the UE ID, slot number, sub-frame number and the size of the allocated resource region.