GB2571073A

GB2571073A - Control information transmission

Info

Publication number: GB2571073A
Application number: GB1802187.3A
Authority: GB
Inventors: Salim Umer; Wagner Sebastian; Jechoux Bruno
Original assignee: TCL Communication Ltd
Current assignee: TCL Communication Ltd
Priority date: 2018-02-09
Filing date: 2018-02-09
Publication date: 2019-08-21
Anticipated expiration: 2038-02-09
Also published as: GB2571073B; GB201802187D0; WO2019154105A1; CN111886844A; CN111886844B

Abstract

User equipment (UE) receives and stores signals from a base station, then receives scheduling information 22 identifying the resources used for a data transmission 20 only after transmission of the signals has begun. The UE then uses the scheduling information to recover the data from the stored signals. The data may be transmitted on the PDSCH and the scheduling information on the PDCCH in a downlink control information (DCI) message. An indication may be sent to the UE that data signals may be transmitted prior to the relevant scheduling information, and this may be sent in dependence on control resource availability or UE class. The scheduling information may be transmitted in any slot subsequent to the slot used for the data, and the indication may include a maximum delay in terms of a number of PDCCH occasions. The frequency resources used for the data transmission may be restricted to reduce the storage requirement for the UE. This back-scheduling may be used to alleviate the problems associated with PDCCH blocking, hence helping to reduce latency in URLLC systems.

Description

Control Information Transmission

Technical Field [0001] The following disclosure relates to the transmission of downlink data, and particularly to systems for improving the efficiency of downlink communications.

Background [0002] 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.

[0003] 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.

[0004] 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), fora 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.

[0005] A trend in wireless communications is towards the provision of lower latency and higher reliability channels. 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%).

[0006] Communications over the physical wireless link are defined by a number 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.

[0007] 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, Hybridautomatic-repeat-request related parameters and the parameters related to uplink response for example.

[0008] 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.

[0009] 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.

[0010] A resource-element group (REG) equals one RB during one OFDM symbol.

[0011] A control-channel element (CCE) consists of 6 REGs.

[0012] A PDCCH consists of one or more CCEs (e.g. Le{1,2,4,8}). This number is defined as the CCE aggregation level (AL).

[0013] 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.

[0014] 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).

[0015] B consecutive REGs in time (and frequency, in case B is larger than the size of CORESET in symbols) form a REG bundle.

[0016] 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.

[0017] In case of interleaved CCE-to-REG mapping, Be{2,6} for 1 or 2 symbol CORESET, Be{3,6] for 3 symbol CORESET.

[0018] A PDCCH search space at CCE AL L is defined by a set of PDCCH candidates for this CCE AL.

[0019] 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.

[0020] 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).

[0021] 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).

[0022] It is also noted in that document that spectral efficiency should be considered when trying to achieve a reliability target.

[0023] 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.” [0024] 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 [0025] 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.

[0026] Inversely, the probability of erroneous packet transmission P (=1-R) is given by:

P = 1-(1-P_c)(l-P_d) [0027] where P_c and P_d denote the probability of erroneous PDCCH and PDSCH transmission, respectively.

[0028] 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^-6 and P_d = 2 10^-6, etc.

[0029] 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_cRdi + (1 — R/)RdtxRcRc12 + «_c(l ^— Rdi)RNRcRd2 [0030] where R_dl and R_d2 denote the probability of successful initial PDSCH transmission and PDSCH retransmission, respectively; R_{D7 Y} denotes the probability of gNB detecting DTX or NACK, when UE “sends” DTX (i.e. does not send anything) in UL; R_w denotes the probability of gNB detecting DTX or NACK, when UE sends NACK.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] Figure 1 shows a schematic diagram of transmission resources. 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 of the slot. In the example of Figure 1, in the first slot, the PDCCH for a certain UE (shown dotted) occupies all control resources but the associated PDSCH for this UE (also shown dotted) only utilises a subset of the data resources. PDCCH may require a large amount of resources due to the use of higher aggregation levels to improve reliability, for example due to the UE being at the cell edge, or having poor channel conditions.

[0036] Data resources 104 are thus unused, but cannot be utilised by another UE due to the lack of control resources in which a scheduling transmission can be made. Another UE which also needs to be serviced and whose data is available at the gNB in the same time interval is thus not serviced in this occasion as there are no control resources available to transmit the required PDCCH, potentially breaking latency constraints for the services of the other UE. Such a situation occurs due to PDCCH blocking, even though there are resources available to transmit the data.

[0037] The present invention is seeking to solve at least some of the outstanding problems in this domain.

Summary [0038] 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.

[0039] There is provided a method of transmitting data from a base station to a user equipment (UE) in a wireless cellular communications network, the method comprising the steps of transmitting signals representing data from a base station to a UE via a wireless link; receiving the signals representing the data at the UE and storing those signals; subsequent to starting transmitting the signals representing the data, transmitting from the base station to the UE scheduling information, wherein the scheduling information identifies the resources utilised to transmit the signals representing the data; and receiving at the UE the scheduling information; and utilising, at the UE, the scheduling information to recover the data from the stored signals.

[0040] The scheduling information may be transmitted after transmission of the signals representing the data is completed.

[0041] The scheduling information may indicate the end of data transmission signals during the transmission or after the end of the control transmission signals.

[0042] The signals representing the data may be transmitted in a data transmission region of a first slot, and the scheduling information is transmitted in a control region of a second slot.

[0043] The signals representing the data may be transmitted on a PDSCH and the scheduling information is transmitted on a PDCCH.

[0044] The scheduling information may be transmitted in a downlink control information message.

[0045] The signals representing the data may be transmitted in a first slot, and the scheduling information is transmitted in a subsequent slot.

[0046] The scheduling information may be transmitted in the slot adjacent to the first slot.

[0047] The scheduling information may not be transmitted in the slot adjacent to the first slot.

[0048] The scheduling/control information may comprise an indication of time domain PDSCH resource comprising the signals representing the data, utilising a row index of an RRC configured table.

[0049] Additional rows may be configured in the RRC configured table to represent data transmitted prior to scheduling information.

[0050] The method may further comprise the step of, prior to transmission of the signal representing the data, transmitting an indication to the UE that data signals may be received prior to scheduling information relating to those data signals.

[0051] The indication may be an RRC message.

[0052] The indication may be transmitted dependent on control resource availability.

[0053] The indication may be transmitted dependent on the class or type of UE.

[0054] The indication may be transmitted as a broadcast message or as a message to a particular UE.

[0055] The indication may further comprise an indication of the maximum delay between the signals representing the data, and the scheduling information.

[0056] The maximum delay may be indicated as a number of PDCCH occasions.

[0057] The indication may further comprise an indication of frequency resources which may be utilised for the transmission of data prior to related scheduling information.

[0058] There is also provided a method of transmitting data from a base station to a user equipment (UE) in a wireless cellular communications network, the method comprising the steps of transmitting signals representing data from a base station to a UE via a wireless link; and subsequent to starting transmitting the signals representing the data, transmitting from the base station to the UE scheduling information, wherein the scheduling information identifies the resources utilised to transmit the signals representing the data.

[0059] The scheduling information may indicate the end of data transmission signals during the transmission or after the end of the control transmission signals.

[0060] The scheduling information may be transmitted after transmission of the signals representing the data is completed.

[0061] The signals may represent the data are transmitted in a data transmission region of a first slot, and the scheduling information is transmitted in a control region of a second slot.

[0062] The signals representing the data may be transmitted on a PDSCH and the scheduling information is transmitted on a PDCCH.

[0063] The scheduling information may be transmitted in a downlink control information message.

[0064] The signals representing the data may be transmitted in a first slot, and the scheduling information is transmitted in a subsequent slot.

[0065] The scheduling information may be transmitted in the slot adjacent to the first slot.

[0066] The scheduling information may not be transmitted in the slot adjacent to the first slot.

[0067] The indication may comprises an indication of time domain PDSCH resource comprising the signals representing the data, utilising a row index of an RRC configured table.

[0068] Additional rows may be configured in the RRC configured table to represent data transmitted prior to scheduling information.

[0069] The method may further comprise the step of, prior to transmission of the signal representing the data, transmitting an indication to the UE that data signals may be received prior to scheduling information relating to those data signals.

[0070] The indication may be is an RRC message.

[0071] The indication may be transmitted dependent on control resource availability.

[0072] The indication may be transmitted dependent on the class or type of UE.

[0073] The indication may be transmitted as a broadcast message.

[0074] The indication may be transmitted as a message to a particular UE.

[0075] The indication may further comprise an indication of the maximum delay between the signals representing the data, and the scheduling information.

[0076] The maximum delay may be indicated as a number of PDCCH occasions.

[0077] The indication may further comprises an indication of frequency resources which may be utilised for the transmission of data prior to related scheduling information.

[0078] There is also provided a base station configured to perform the method described above.

[0079] There is also provided a method of transmitting data from a base station to a user equipment (UE) in a wireless cellular communications network, the method comprising the steps of receiving signals representing data at a UE and storing those signals; subsequent to starting transmitting the signals representing the data, transmitting from the base station to the UE scheduling information, wherein the scheduling information identifies the resources utilised to transmit the signals representing the data; and subsequently receiving at the UE scheduling information which identifies the resources utilised to transmit the signals representing the data; and utilising, at the UE, the scheduling information to recover the data from the stored signals.

[0080] The scheduling information may indicate the end of data transmission signals during the transmission or after the end of the control transmission signals.

[0081] The scheduling information may be received after reception of the signals representing the data is completed.

[0082] The signals representing the data may be received in a data region of a first slot, and the scheduling information is received in a control region of a second slot.

[0083] The signals representing the data may be received on a PDSCH and the scheduling information is received on a PDCCH.

[0084] The scheduling information may be received in a downlink control information message.

[0085] The signals representing the data may be received in a first slot, and the scheduling information is received in a subsequent slot.

[0086] The scheduling information may be received in the slot adjacent to the first slot.

[0087] The scheduling information may not be received in the slot adjacent to the first slot.

[0088] The indication may comprise an indication of time domain PDSCH resource comprising the signals representing the data, utilising a row index of an RRC configured table.

[0089] Additional rows may be configured in the RRC configured table to represent data transmitted prior to scheduling information.

[0090] The method may further comprise the step of, prior to receiving the signal representing the data, receiving an indication that data signals may be received prior to scheduling information relating to those data signals.

[0091] The indication may be an RRC message.

[0092] The indication may be received as a broadcast message.

[0093] The indication may be received as a message to the particular UE.

[0094] The indication may further comprise an indication of the maximum delay between the signals representing the data, and the scheduling information.

[0095] The maximum delay may be indicated as a number of PDCCH occasions.

[0096] The indication may further comprise an indication of frequency resources on which signals representing data prior to related scheduling information may be received.

[0097] The UE may store the signals representing data for at least the maximum delay indicated.

[0098] There is also provided a UE configured to perform the methods described above. [0099] 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 [0100] 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 transmission resources using back-scheduling;

Figure 3 shows a method of data transmission and reception with back scheduling;

Figure 4 shows latency benefit of back scheduling in the event of PDCCH blocking;

Figure 5 shows different possibilities of back scheduling delay between control and data; and

Figures 6 and 7 show simulation results for data transmission using back scheduling.

Detailed description of the preferred embodiments [0101] 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.

[0102] Figure 2 shows a diagram of transmission resources in which data is transmitted prior to control information according to the method shown in Figure 3.

[0103] At step 30 data is available for transmission from a base station to a UE. At step 31 it is identified that data transmission resources in a forthcoming slot are available, but that no control resources are available to transmit a PDCCH indication of the data scheduling. This is the situation shown in Figure 1.

[0104] At step 32 the base station transmits the signals 20 representing the data using the available resources, despite no PDCCH transmission being made first. At step 33 the signals 20 are received by the UE which has been configured to monitor transmissions, even in the absence of relevant scheduling information, and to save received signals for later processing.

[0105] At step 34 the base station identifies available control resources in the subsequent slot 21 and transmits scheduling information 22 using those resources, where the scheduling information relates to the data 20 already transmitted. The transmission of scheduling information after the data to which it relates may be referred to as back-scheduling.

[0106] At step 35 the UE receives the scheduling information 22, and can thus identify that the previously received signals are for the UE. At step 36 the UE uses the scheduling information to decode the previously received signals and retrieve the data. The scheduling information is typically contained in a DCI message.

[0107] The scheduling information must indicate the time domain resources allocated to the relevant PDSCH. In conventional systems this is achieved by including a reference to a row in an RRC configured table which defines the slot offset, start symbol and length, and PDSCH mapping type. This technique can be adapted for the back-scheduling system, for example by adding additional rows to the RRC configured table. These additional rows have slot offset and start symbol combinations allowing back scheduling. One option is to introduce new rows in this table with negative slot offset values. The existence of rows relating to back scheduling could be used as an indicator for a UE to configure itself for the reception of back scheduled data, but this arrangement is rather static and may be undesirable.

[0108] The method of Figures 2 and 3 thus improves resource utilisation since a greater portion of the data resources are utilised, and reduces latency as the UE is ready to decode the data as soon as the scheduling information is received. Demodulation and decoding can be very fast since the whole data set is available in memory as soon as the scheduling information is received. In contrast, if the base station waited for available control and data resources in the same slot, transmission of the data would not have yet started.

[0109] The transmission of scheduling information after data has been transmitted requires UEs to speculatively monitor signals in the data resources and to save received signals in case scheduling information subsequently indicates the signals were for the UE. Such monitoring may increase power consumption as the UE cannot enter a sleep mode if it does not receive scheduling information, and may require increased memory to store the received signals until it is confirmed they are not related to the UE. However, resource efficiency may be improved and latency may be reduced.

[0110] Figure 4 shows the latency benefit of the proposed invention compared to the conventional transmission in the case of shortage of control resources. Figure 4(a) represents the conventional approach in which control and data can be transmitted in the first available slot after receipt of a packet at the base station for transmission. Tw represents the wait time before transmission is started and Tt is the total transmission time for both data and control. Tp is the UE processing time, giving a total duration between availability of the packet for transmission and completion of decoding of T at the UE.

[0111] Figure 4(b) shows the conventional approach when insufficient control resources are available in the first transmission occasion. The control and data are thus scheduled in the next available slot giving a large wait time Tw and hence large total time T.

[0112] In contrast, in Figure 4(c) where the control resources are short in the first occasion like in Figure 4(b), the data is still transmitted in available data resources in the first transmission occasion and the control information is transmitted subsequently in the next available control occasion, referring back to the earlier-transmitted data. A significant improvement is seen in both wait time Tw and total time T compared to the conventional approach in Figure 4(b) for coping with lack of control resources. Improved use is thus made of transmission resources, and total latency for data transmission is reduced for cases where control resources limit transmission possibilities.

[0113] The time margin gained by using back scheduling can be useful for applications/users requiring low latencies and high reliabilities. In some cases, this time margin can allow the users to meeting their latency targets. In some other cases, if the first data packet decoding fails, this time margin may translate in a retransmission possibility. The user can then try to combine the two retransmissions to achieve better decodability for the data packet. This adds to the reliability of the data within certain time limit.

[0114] In the above examples the scheduling information has been transmitted in the first control resources after transmission of the data. However, the scheduling information can be transmitted at any time after transmission of the data. A longer delay increases the total transmission time, and may increase storage requirements at the UE and so it may be desirable to limit the total allowable delay. However, some delay may improve flexibility where, for example, the first control resources after data transmission are fully occupied. As shown in Figure 5 the scheduling resources can then be transmitted in the second slot/transmission occasion after the data. Longer delays are possible, and may lead to further improvements, but also increase UE power consumption and storage requirements. The maximum delay may be defined for the UEs supporting back scheduling dependent on their class/category. For example, for some classes of UE, such as medical equipment able to communicate, communicating self-driving cars, sensitive industrial control etc, the additional cost of power consumption and storage may be an appropriate trade-off for improved performance and quality of service in terms of latency and reliability. Such UEs may thus allow a larger delay than, for example, a budget UE where cost of manufacture is more important than performance. Maximum delay may be defined according to UE category, or specifically for a UE. The maximum allowable delay may be defined as a time value, number of slots, PDCCH occasions, or any other appropriate metric.

[0115] In the above examples, the scheduling information was transmitted after the data transmission had been completed by the base station. In modern wireless systems like 5G NR, the occasions for transmission of PDCCH can be configured anywhere in a slot, and the data can be scheduled for a length of 1 OFDM symbol going up to multiple slots. These features combined with back scheduling may lead to the settings where the data (PDSCH) will start before the start of control (due to back scheduling) and may have its end point in the middle of the control (PDCCH) transmission or even after the end of the control transmission.

[0116] Activation of the back-scheduling system may be controlled by the RAN, in particular the base station, and/or CN. Such configuration may be made on a cell-by-cell basis, for groups of UEs, or for individual UEs. The configuration may also be varied to allow for variations in demand over time. When control resources are not scarce the feature may not be configured to minimise UE power usage, and may be enabled when control resources become limiting.

[0117] The techniques described above may be more appropriate for certain categories of UE. For example power consumption is less significant for UEs with a permanent power source (rather than battery powered) and therefore such UEs may be more readily configured to receive back-scheduling transmissions. Activation of a back-scheduling system may therefore be performed dependent on the class of UE.

[0118] The back-scheduling facility may be activated dependent on the category of UE. For example, UEs utilising URLLC communications are more likely to benefit from the system due to the strict latency requirements for such services.

[0119] The signalling to activate or de-activate the back scheduling can in principle be at cell level in the form of broadcast signalling or in the form of group specific or user specific, although there would be considerable overhead of broadcast signalling as it is transmitted so as to be decodable by all the UEs in the cell. Due to the nature and good applicability to some specific users (for example URLLC users), this signalling may preferably be user specific. The network can send RRC signalling to a URLLC user who happens to be active in a cell during the time when there is heavy traffic in the cell and the network envisages some potential PDCCH blockage scenarios may hit the latency and consequently the reliability requirements of this UE.

[0120] The above disclosure has been provided in the context of a slots divided into predefined control and data regions. However, some wireless standards, for example 5G NR, allow more flexible transmission mechanisms including simultaneous scheduling of slotbased 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. The principle of permitting data transmission to start before starting transmission of the related scheduling information is equally applicable to such other formats.

[0121] Certain wireless standards may provide very large bandwidths which are available for data transmission, for example 5G NR may operate at mmWave frequencies with very large bandwidth carriers. Monitoring and storing the full bandwidth in such systems to utilise backscheduling may be impractical due to the storage requirements. The frequency resources on which data with back-scheduled control transmissions can be transmitted may thus be limited to a sub-set of the total bandwidth available. UEs then only need to monitor and store the relevant frequency resources, thus reduced storage requirements. A subset of the carrier bandwidth (or a range of PRBs) may be configured to the UE as part of the back scheduling configuration. Then the UE only monitors and records the configured frequency resources for back scheduling of data. In another example, the back-scheduling resources may be limited to a UE’s active bandwidth part.

[0122] Set out below are simulation results to exemplify the potential benefits of a backscheduling system.

[0123] Figure 6 shows example results showing PDCCH blocking probability against PDCCH bandwidth. The results are based on four users to be scheduled in each transmission occasion. Each UE may use an aggregation level of 4, 8, or 16 with respective probabilities of 0.5, 0.45, 0.05. Sub-carrier spacing is assumed to be 15 kHz, and the results are based on 1 million independent transmission occasions. The results show conventional scheduling (in which control and data are transmitted in the same slot), back-scheduling in which scheduling information is permitted to be transmitted only in the next slot (1 occasion), and in which scheduling information is permitted to be transmitted up to 2 occasions later.

[0124] Figure 6 shows a clear reduction in PDCCH block probability. For the set of points at PDCCH resource of 40 MHz, the conventional scheduling leads to blocking probability of 3.2%. In comparison, with a single occasion back scheduling allowed, the PDCCH blocking probability drops to 0.79%. This is a very significant advantage and can be important for low latency users. Going beyond to allowing the base station to back schedule over 2 transmission occasions, the blocking probability drops to only 0.19%.

[0125] The advantage of back scheduling is particularly significant when blocking probabilities are relative low, which is the likely operating range for URLLC services. These services have strict latency and reliability constraints and hence require low blocking probabilities. As noted above, the types of UEs using such services, for example medical equipment, connected vehicles, and industrial control, the additional cost of expanded memory and higher power consumption may be a suitable trade-off for the improved performance, notably in terms of latency and reliability.

[0126] The results also show little advantage where blocking probabilities are very high due to scarce resources, for example as seen for the 20 and 30MHz bandwidths. This is due to most transmission occasions lacking the PDCCH resources to schedule the active users. However, such scenarios are not practical, even for non-URLLC services, and are not of significant concern.

[0127] Figure 7 shows PDCCH blocking probability for a varying number of users. PDCCH resources are defined to be equivalent in PRBs to a bandwidth of 50MHz and each UE uses aggregation levels of 4, 8, or 16 with probabilities of 0.5, 0.45, and 0.05 respectively. Subcarrier spacing is 15KHz, and 1 million independent transmissions are calculated.

[0128] The results of Figure 7 confirm gains of PDCCH back scheduling over the traditional scheduling scheme. At a PDCCH blocking probability of 0.001 (0.1%), the legacy scheme can accommodate 3 users in each scheduling interval. In comparison, the scheme with back scheduling over a single occasion accommodates 4 users in each scheduling interval with the same resources and the same blocking probability. The back scheduling over two occasions can support 4 users per scheduling interval for the same amount of resources and the same blocking probability.

[0129] For 4 users scheduled in each transmission occasion for fixed PDCCH resources, the legacy scheme results in PDCCH blocking probability of 0.35%, whereas back scheduling over 1 and 2 occasions result in blocking probabilities of 0.019% and 0.0004% respectively. Thus, even the single occasion back scheduling provides more than 10 times the benefit in terms of blocking probability. This benefit directly translates in better system spectral and utilisation efficiency and more importantly more users served with a given latency target.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] 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 [0138] 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.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] 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.

[0143] 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.

[0144] 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.

[0145] 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

1. A method of transmitting data from a base station to a user equipment (UE) in a wireless cellular communications network, the method comprising the steps of transmitting signals representing data from a base station to a UE via a wireless link; receiving the signals representing the data at the UE and storing those signals;

subsequent to starting transmitting the signals representing the data, transmitting from the base station to the UE scheduling information, wherein the scheduling information identifies the resources utilised to transmit the signals representing the data; and receiving at the UE the scheduling information; and utilising, at the UE, the scheduling information to recover the data from the stored signals.

2. A method according to claim 1, wherein the scheduling information is transmitted after transmission of the signals representing the data is completed.

3. A method according to claim 1 or claim 2, wherein the scheduling information indicates the end of data transmission signals during the transmission or after the end of the control transmission signals.

4. A method according to any preceding claim, wherein the signals representing the data are transmitted in a data transmission region of a first slot, and the scheduling information is transmitted in a control region of a second slot.

5. A method according to any preceding claim, wherein the signals representing the data are transmitted on a PDSCH and the scheduling information is transmitted on a PDCCH.

6. A method according to any preceding claim, wherein the scheduling information is transmitted in a downlink control information message.

7. A method according to any preceding claim, wherein the signals representing the data are transmitted in a first slot, and the scheduling information is transmitted in a subsequent slot.

8. A method according to claim 7, wherein the scheduling information is transmitted in the slot adjacent to the first slot.

9. A method according to claim 7, wherein the scheduling information is not transmitted in the slot adjacent to the first slot.

10. A method according to any of the preceding claims, wherein the scheduling/control information comprises an indication of time domain PDSCH resource comprising the signals representing the data, utilising a row index of an RRC configured table.

11. A method according to the previous claim, wherein additional rows are configured in the RRC configured table to represent data transmitted prior to scheduling information.

12. A method according to any preceding claim, further comprising the step of, prior to transmission of the signal representing the data, transmitting an indication to the UE that data signals may be received prior to scheduling information relating to those data signals.

13. A method according to claim 12, wherein the indication is an RRC message.

14. A method according to claim 12, wherein the indication is transmitted dependent on control resource availability.

15. A method according to any of claims claim 12 to 14, wherein the indication is transmitted dependent on the class or type of UE.

16. A method according to any of claims 12 to 15, wherein the indication is transmitted as a broadcast message.

17. A method according to any of claims 12 to 15, wherein the indication is transmitted as a message to a particular UE.

18. A method according to any of claims 12 to 15, wherein the indication further comprises an indication of the maximum delay between the signals representing the data, and the scheduling information.

19. A method according to claim 18, wherein the maximum delay is indicated as a number of PDCCH occasions.

20. A method according to any of claims 12 to 19, wherein the indication further comprises an indication of frequency resources which may be utilised for the transmission of data prior to related scheduling information.

21. A method of transmitting data from a base station to a user equipment (UE) in a wireless cellular communications network, the method comprising the steps of transmitting signals representing data from a base station to a UE via a wireless link; and subsequent to starting transmitting the signals representing the data, transmitting from the base station to the UE scheduling information, wherein the scheduling information identifies the resources utilised to transmit the signals representing the data.

22. A method according to claim 21, wherein the scheduling information indicates the end of data transmission signals during the transmission or after the end of the control transmission signals.

23. A method according to claim 21 or 22, wherein the scheduling information is transmitted after transmission of the signals representing the data is completed.

24. A method according to any of claims 21 to 23, wherein the signals representing the data are transmitted in a data transmission region of a first slot, and the scheduling information is transmitted in a control region of a second slot.

25. A method according to any of claims 21 to 24, wherein the signals representing the data are transmitted on a PDSCH and the scheduling information is transmitted on a PDCCH.

26. A method according to any of claims 21 to 25, wherein the scheduling information is transmitted in a downlink control information message.

27. A method according to any of claims 21 to 26, wherein the signals representing the data are transmitted in a first slot, and the scheduling information is transmitted in a subsequent slot.

28. A method according to claim 27, wherein the scheduling information is transmitted in the slot adjacent to the first slot.

29. A method according to claim 27, wherein the scheduling information is not transmitted in the slot adjacent to the first slot.

30. A method according to any of claims 21 to 29, wherein the indication comprises an indication of time domain PDSCH resource comprising the signals representing the data, utilising a row index of an RRC configured table.

31. A method according to claim 30, wherein additional rows are configured in the RRC configured table to represent data transmitted prior to scheduling information.

32. A method according to any of claims 21 to 31, further comprising the step of, prior to transmission of the signal representing the data, transmitting an indication to the UE that data signals may be received prior to scheduling information relating to those data signals.

33. A method according to claim 32, wherein the indication is an RRC message.

34. A method according to claim 32, wherein the indication is transmitted dependent on control resource availability.

35. A method according to any of claims claim 32 to 34, wherein the indication is transmitted dependent on the class or type of UE.

36. A method according to any of claims 32 to 35, wherein the indication is transmitted as a broadcast message.

37. A method according to any of claims 32 to 35, wherein the indication is transmitted as a message to a particular UE.

38. A method according to any of claims 32 to 35, wherein the indication further comprises an indication of the maximum delay between the signals representing the data, and the scheduling information.

39. A method according to claim 38, wherein the maximum delay is indicated as a number of PDCCH occasions.

40. A method according to any of claims 32 to 39, wherein the indication further comprises an indication of frequency resources which may be utilised for the transmission of data prior to related scheduling information.

41. A base station configured to perform the method of any of claims 21 to 40.

42. A method of transmitting data from a base station to a user equipment (UE) in a wireless cellular communications network, the method comprising the steps of receiving signals representing data at a UE and storing those signals;

subsequent to starting transmitting the signals representing the data, transmitting from the base station to the UE scheduling information, wherein the scheduling information identifies the resources utilised to transmit the signals representing the data; and subsequently receiving at the UE scheduling information which identifies the resources utilised to transmit the signals representing the data; and utilising, at the UE, the scheduling information to recover the data from the stored signals.

43. A method according to claim 42, wherein the scheduling information indicates the end of data transmission signals during the transmission or after the end of the control transmission signals.

44. A method according to claim 42, wherein the scheduling information is received after reception of the signals representing the data is completed.

45. A method according to any of claims 42 to 44, wherein the signals representing the data are received in a data region of a first slot, and the scheduling information is received in a control region of a second slot.

46. A method according to any of claims 42 to 45, wherein the signals representing the data are received on a PDSCH and the scheduling information is received on a PDCCH.

47. A method according to any of claims 42 to 46, wherein the scheduling information is received in a downlink control information message.

48. A method according to any of claims 42 to 47, wherein the signals representing the data are received in a first slot, and the scheduling information is received in a subsequent slot.

49. A method according to claim 48, wherein the scheduling information is received in the slot adjacent to the first slot.

50. A method according to claim 48, wherein the scheduling information is not received in the slot adjacent to the first slot.

51. A method according to any of claims 42 to 55, wherein the indication comprises an indication of time domain PDSCH resource comprising the signals representing the data, utilising a row index of an RRC configured table.

52. A method according to claim 51, wherein additional rows are configured in the RRC configured table to represent data transmitted prior to scheduling information.

53. A method according to any of claims 42 to 52, further comprising the step of, prior to receiving the signal representing the data, receiving an indication that data signals may be received prior to scheduling information relating to those data signals.

54. A method according to claim 53, wherein the indication is an RRC message.

55. A method according to claim 53 or claim 54, wherein the indication is received as a broadcast message.

56. A method according to any of claims 53 to 55, wherein the indication is received as a message to the particular UE.

57. A method according to any of claims 53 to 56, wherein the indication further comprises an indication of the maximum delay between the signals representing the data, and the scheduling information.

58. A method according to claim 57, wherein the maximum delay is indicated as a number of PDCCH occasions.

59. A method according to any of claims 53 to 58, wherein the indication further comprises an indication of frequency resources on which signals representing data prior to related scheduling information may be received.

5

60. A method according to any of claims 53 to 59, wherein the UE stores the signals representing data for at least the maximum delay indicated.

61. A UE configured to perform the method of any of claims 42 to 60.