GB2576034A

GB2576034A - Uplink transmission resource sharing

Info

Publication number: GB2576034A
Application number: GB1812600.3A
Authority: GB
Inventors: Salim Umer
Original assignee: TCL Communication Ltd
Current assignee: TCL Communication Ltd
Priority date: 2018-08-02
Filing date: 2018-08-02
Publication date: 2020-02-05
Anticipated expiration: 2038-08-02
Also published as: GB2576034B; WO2020025032A1; GB201812600D0; CN112335316A; CN112335316B

Abstract

A base station transmits an indication to a UE of available uplink resources and of uplink resources allocated (401), in a period prior to the start of the available resources, to other UEs associated with the same base station. In some embodiments, the period is a listen-before-talk (LBT) period, and the UE may identify utilized resources in that period. In such embodiments, if the identified utilized resources are identical to, are a subset of, or are similar to (403), the identified resources then the UE may transmit (404). In this way, a resource band may be used concurrently by a group of distinct UEs whilst avoiding interference with other UEs, or other groups, that may be in contention for the uplink resources, which may be unlicensed. The resources may be interlaces to allow each UE to span a wide bandwidth. The indication of resource availability may comprise a bitmap field.

Description

Technical Field [1] The following disclosure relates to sharing transmission resources in a cellular wireless network, and in particular to the sharing of uplink transmission resources in unlicensed spectrum.

Background [2] 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 3rd 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.

[3] 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.

[4] 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.

[5] The NR protocols are intended to offer options for operating in unlicensed radio bands, to be known as NR-U. When operating in an unlicensed radio band the gNB and UE must compete with other devices for physical medium access. For example, Wi-Fi, NR-U, and LAA may utilise the same physical medium resources.

[6] In order to share resources a Listen Before Talk (LBT) protocol is proposed in which a gNB or UE monitors the available resources and only commences a transmission if there is no conflict with another device already utilising the resources. Once an LBT process is successful (the resources are “won”), the gNB or UE gains access to the resources for up to the Channel Occupancy Time (COT) provided there is no interruption of transmissions for more than a predefined interval (for example 16με).

[7] Two types of LBT process were standardized for LAA and have been proposed for UL transmissions in NR. In Type 1 a series of slots have to be detected on a channel to indicate a Clear Channel Assessment (CCA) and that the channel is available. The number of slots to be sensed is defined by the Contention Window Size (CWS) which is selected by the UE, dependent on factors including the priority class of the UE. In Type 2, a single short period is used to perform CCA whose duration has been fixed to be 25 micro seconds in 3GPP.

[8] Transmissions in unlicensed spectrum must comply with various regulations in force for that spectrum. For example, many regulations specify an Occupied Channel Bandwidth (OCB) and Nominal Channel Bandwidth (NCB) which must be complied with. The NCB defines the widest band of frequencies, including guard bands, allocated to a channel, and the OCB defines the bandwidth containing a defined fraction (typically 99%) of a signal’s power. Often the OCB must be must be between 80% and 100% of the NOB. As an example, ETSI EN 301.893 defines requirements in the EU for the 5GHz band.

[9] It is proposed that UL transmissions are made using an interlace-based resource allocation. This allows each UE to span a wide bandwidth and transmit a high overall power, without needing to occupy the whole bandwidth. Figure 1 shows an interlace structure having ten interlaces. Data is transmitted over interlaced resource blocks which are multiplexed in frequency. The basic resource allocation unit is considered to be one interlace, which is arranged to meet the OCB requirements discussed above thus allowing multiplexing of multiple UEs on different interlaces.

[10] The interlace structure also allows the spread of energy to meet the PSD requirements and still have a sufficient energy transmission to ensure the signal is decodable at the receiver. In an example interlace structure from LTE eLAA the interlace structure includes 10 RBs/interlaces for both 10 MHz and 20 MHz system bandwidths. RBs within an interlace are equidistant, and Demodulation Reference Symbols (DMRS) in unlicensed spectrum utilise legacy generation sequence and symbol positions, while keeping the same frequency positions as PUSCH REs in the middle symbol of each slot.

[11] NR can utilise with both slot-based and non-slot-based scheduling. In the slot-based system control messages (PDCCH) are transmitted in the first 2 or 3 symbols of each slot and schedule resources for the slot, whereas in non-slot-based scheduling PDCCH may be transmitted during the slot and with different periodicities. These arrangements allow efficient use of resources and tailoring to each UE’s requirements.

[12] To initiate transmission of UL data on the Physical Uplink Shared Channel (PUSCH) an eNB indicates to a UE the type of channel access procedure it should use in an uplink grant scheduling message. In general, the type 1 uplink channel access procedure is utilized to initialize an MCOT containing PUSCH transmission, while the type 2 uplink channel access procedure is utilized within the MCOT for resuming a suspended transmission or for changing the transmission direction from downlink to uplink. For transmission of a Sounding Reference Signal (SRS) without a PUSCH from a UE, the UE always utilises the type 1 uplink channel access procedure with the highest priority class.

[13] The type 1 and 2 LBT processes operate successfully where devices are only permitted to commence transmission at a single symbol, but do not permit different devices to start transmission at different symbols in an efficient manner. Figure 2 shows allocation of two UEs, UE1 and UE2, to interlaces 0 and 2. This figure shows an interlace as a scheduling entity even though in reality each single interlace may comprise multiple distributed resource blocks. For UE1 conventional LBT can identify channel availability and commence transmission at the scheduled time. However, UE2 is scheduled to commence transmission part-way through the slot, after UE1 has already started transmission. Since UE1 and UE2 are associated with the same gNB it can in theory commence transmission even though UE1 is already transmitting. However, when performing its LBT process UE2 will detect the transmission power of UE1 and hence cannot commence transmission as the medium has been seized by UE1, even though UE2 has been scheduled to use a different interlace.

[14] Figure 3 shows the same resource allocation, but here the relevant gNB lost access to the transmission medium and UE1 did not start transmitting at the start of the slot. A Wi-Fi device seized access and started transmitting across the bandwidth allocated to UE1 and UE2. The gNB may have lost access due to the Wi-Fi device seizing the channel during the switching time between DL and UL, the Wi-Fi device may have seized the channel during UETs LBT interval, or UE1 might have missed its UL grant and hence did not start transmitting.

[15] In both Figure 2 and Figure 3 UE2 will detect transmission power and so is unable to commence transmission even though in Figure 2 it is entitled to do so if both UE1 and UE2 are scheduled by the same gNB. Even if UE2 can identify that the detected power during LBT is a transmission on a particular interlace which does not conflict with its allocated interlace it still cannot transmit as it is not aware if the relevant device is part of the same group as UE2 and hence whether it is permitted to commence transmissions.

[16] There is therefore a requirement for an LBT process that will allow effective multiplexing of devices.

Summary [17] 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.

[18] There is provided a method of resource sharing in a cellular communication system, the method performed by a base station and comprising the steps of transmitting an indication from the base station to a UE indicating resources available for uplink (UL) transmissions from the UE to the base station; and transmitting an indication from the base station to the UE of UL transmission resources allocated to other UEs associated with the base station in a period prior to the start of the resources indicated as available to the UE for UL transmissions.

[19] There is also provided a method of resource sharing in a cellular communication system, the method performed by a UE and comprising the steps of receiving an indication from a base station indicating resources available for uplink (UL) transmissions from the UE to the base station; and receiving an indication from the base station of UL transmission resources allocated to other UEs associated with the base station in a period prior to the start of the resources indicated as available to the UE for UL transmissions.

[20] The resources may be located in an unlicensed band.

[21] The resources may comprise a plurality of interlaces.

[22] The indication of UL transmission resources allocated to other UEs may comprise a bitmap field.

[23] Each bit of the bitmap may correspond to a group of physical resources.

[24] The groups of physical resources may be interlaces.

[25] The indication of UL transmission resources allocated to other UEs may be transmitted in a group-common DCI message.

[26] The group-common DCI message may be a DCI 1-C format DCI message.

[27] The indication of UL transmission resources allocated to other UEs may be transmitted in a UE-specific DCI message.

[28] The UE-specific DCI message may be a DCI message which also includes the indication of resources available for transmissions from the UE to the base station.

[29] The indication of resources available for transmission from the UE to the base station may comprise an indication of a subsequent message indicating the UL transmission resources allocated to other UEs.

[30] The UL transmission resources allocated to other UEs may include resources allocated for configured-grant-based transmissions.

[31] The UL transmission resources allocated to other UEs may include resources allocated to UEs associated with the base station but operating in a different beam to the UE.

[32] The resource indication may be the resource occupation for the symbol preceding the first symbol of the UE’s allocated resources.

[33] The indication of UL transmission resources allocated to other UEs may include the utilisation at a plurality of different times.

[34] The period may be a Listen Before Talk (LBT) period of the UE.

[35] The indication of UL transmission resources allocated to other UEs may be received in a group-common DCI message.

[36] The group-common DCI message may be a DCI 1-C format DCI message.

[37] The indication of UL transmission resources allocated to other UEs may be received in a UE-specific DCI message.

[38] The UE-specific DCI message may be a DCI message which also includes the indication of resources available for transmissions from the UE to the base station.

[39] The method may further comprise performing a LBT process to identify utilised resources in the LBT period, wherein the UL only transmits in its allocated UL transmission resources if the utilised resources are the same as the resources indicated as allocated to other UEs.

[40] The method may further comprise the step of performing a LBT process to identify utilised resources in the LBT period, wherein the UL only transmits in its allocated UL transmission resources if the utilised resources are the same as, or a subset of, the resources indicated as allocated to other UEs.

[41] The method may further comprise the step of performing a LBT process to identify utilised resources in the LBT period, wherein the UL only transmits in its allocated UL transmission resources if the utilised resources are different to the resources indicated as allocated to other UEs by less than a predefined threshold.

[42] There are provided a UE and a base station to perform the relevant methods.

[43] 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 [44] 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.

[45] Figure 1 shows a set of interlaces;

[46] Figure 2 shows scheduling of two UEs on different interlaces;

[47] Figure 3 shows an example of a competing transmitter seizing the transmission medium;

[48] Figure 4 shows an LBT process; and [49] Figures 5 to 8 show scheduling of UEs on resources.

Detailed description of the preferred embodiments [50] 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.

[51] The following disclosure provides an improved LBT mechanism which seeks to enable more efficient multiplexing of UE UL transmissions. The unlicensed spectrum regulations specify that only one device, or group of devices, is permitted to access the spectrum at a time. A cell of a cellular system and all UEs associated with that cell are defined as a group. In the scenario shown in Figure 2 above, UE1 and UE2 are associated with the same cell and hence it is permissible for UE2 to commence transmissions, even though UE1 is already transmitting in the spectrum.

[52] In an enhanced LBT process, described in more detail below, a base station notifies UEs of the spectrum allocation of other UEs in the same cell. The UEs themselves are configured such that, when performing an LBT process, they can identify which frequency resources are being utilised. The UE can thus correlate the base station’s indication of spectrum utilisation with the measurement data to determine if the power detected in the LBT process is from other UEs of the same cell, or not. If detected power is related to UEs scheduled by the same cell the UE is free to transmit as scheduled as it is part of the same group. In the example of Figure 2, UE2 would receive an indication that a UE is scheduled on interlace 0. When performing LBT UE2 would identify that power is being transmitted on that interlace and be able to confirm that it is free to transmit. However, in the example of Figure 3 the power and resource occupancy detected by UE2 would not match the indication from the base station and the UE would not transmit.

[53] Figure 4 shows a flowchart of an enhanced LBT procedure. At step 400 a base station transmits a scheduling message to a UE indicating DL and/or UL scheduling for a slot. At step 401 (which may be performed prior to, in conjunction with, or after step 400) the base station transmits an indication of resources allocated to other UEs in the relevant slot.

[54] At step 402 the UE performs an LBT process, prior to commencing UL transmission as indicated by the scheduling message. At step 403 the UE compares the spectrum utilisation identified at step 402 with the indication of resources received at step 401. If the indicated resources and utilised spectrum correlate (for example as set out below) the UE transmits as scheduled at step 404. In contrast, if the indicated resources and utilised spectrum do not correlate (for example as set out below) the UE does not transmit 405 as scheduled as it appears another device has seized the spectrum.

[55] The resource indication could be on a physical resource block (PRB) group basis where the group size can be adapted. For example, Rel-14 eLAA the interlace based transmission has been adapted for UL transmission design where each interlace is composed of interleaved sets of PRBs, as described hereinbefore. Thus, an interlace is the basic unit of resource allocation, and each UE can be assigned one or more interlaces. By way of example only, Rel-14 eLAA defines 10 RB/interlace for UL, giving 5 and 10 interlaces for 10MHz and 20MHz spectrum respectively.

[56] The resource indication should thus indicate to the UE which interlaces are occupied by other UEs associated with the same cell. Such an indication may be provided utilising a bitmap in which each bit represents the occupancy or allocation status of a respective interlace (or other resource block as appropriate). A bitmap is an efficient method of encoding the required information and thus may reduce the signalling overhead. If the relevant protocol uses a different interlace design or different grouping of PRBs which can be allocated to the users for UL transmission, the resource occupancy bitmap should correspond to the grouping of PRBs which is adopted for resource allocation.

[57] Figure 5 shows an example in which two UEs, UEO & UE1, are scheduled on different interlaces at different times in a slot. In this example there are 5 interlaces available. In Figure 5(a) UEO is scheduled to transmit two transport blocks in two slots (slot #1 and slot #2), and UE1 is scheduled to transmit one transport block in slot 2. In Figure 5(b) UEO is scheduled to transmit one transport block across both slot #1 and slot #1, and UE2 is scheduled as for Figure 5(a).

[58] In both Figure 5(a) and (b) UE1 has the same challenge in deciding whether it can transmit or not. In Figure 5(a), UE1 and UEO are scheduled in slot 2 but UE1 upon doing LBT will detect the energy of UEO from slot 1. One strategy to overcome the issue in Figure 5(a) could be to introduce a gap in the transmission of UEO, e.g., by base station scheduling UEO to stop a certain time before the end of slot 1 or by scheduling both UEO and UE1 start their transmissions a little later after the slot 2 starts. This may provide a short interval where no transmission is scheduled but this is resource inefficient. There is further risk that some other devices occupy the unlicensed resource in this gap. This strategy of enforcing gaps between the scheduling intervals would not work in Figure 5(b) as UE1 starts in slot 2 in the middle of the transmission of UE 0. When performing LBT UE1 will therefore detect the power of UEO.

[59] However, according to the process described hereinbefore, if UE1 can correlate the detected resource occupancy and power to an indication of scheduling received from the base station, UE1 can identify that it is permitted to transmit. The base station thus transmits an indication to UE1 of the resource allocation in the relevant slot (in which UE1 is performing its LBT process). For example, if a bitmap format is utilised, the message “01000” may be transmitted to UE1 indicating that when it is scheduled to perform LBT prior to starting its transmissions, only interlace 1 is scheduled to be occupied. If the estimated resource utilisation matches this indication, then UE1 can commence transmissions on interlace 3. In contrast if UE1 senses a different resource utilisation it can be determined that the sensed power is from a different source and that hence it is not permitted to transmit. For example, a different device may have seized the spectrum before UEO commenced its scheduled transmissions and hence it could not transmit as scheduled. In an example, a Wi-Fi device may be transmitting across all interlaces. The sensed resource utilisation would, in the described message format, be “11111”.

[60] If UEO did not start transmissions, for example due a missed UL grant, and no other device is utilising the spectrum, the sensed resource utilisation would be “00000”. In this case, the sensed utilisation does not match the indicated utilisation, but the UE is free to transmit as the spectrum is available according to the LBT measurement. This can be phrased more generally by stating that a UE can transmit if the sensed resource utilisation is a subset of the indicated utilisation. Such a rule also allows for correct transmission by a UE according to the indicated utilisation if at least one of the other UEs scheduled by the same base station misses transmission.

[61] If a UE receives an indication that other UEs are scheduled, but does not detect their transmissions, the UE may perform a short conventional LBT (for example, a Type 2 LBT in the 3GPP standards) before starting transmissions to verify the spectrum is available. If the sensing duration to estimate the resource occupancy are no less than the duration of conventional LBT and the energy detected has been found to be less than the threshold of the conventional LBT , the UE can directly transmit without performing an additional conventional LBT.

[62] A refinement of the above transmission rule is that a UE is allowed to transmit only if the following two conditions are satisfied: (1) the sensed resource occupancy is same or a subset of the indicated resource occupancy, (2) and the discrepancy (for example Exclusive-OR operation of indicated and sensed resource occupancy indications) is smaller than a certain number of resources/interlaces.

[63] The threshold can be preconfigured for all UEs according to specifications, or transmitted to each UE by the network, for example via RRC signalling. If zero discrepancy is allowed, then the sensed resource utilisation must be a perfect match to the indicated resource utilisation. If the allowed discrepancy is equal to the number of interlaces, then the combined two conditions allow the UE to transmit if the sensed resource utilisation is any subset of the indicated resource utilisation.

[64] As opposed to transmission being permitted if a subset of indicated resources is utilised, transmission may be allowed if the discrepancy between the sensed and indicated resource utilisation is below a predefined threshold. That is, if the sensed usage is larger or smaller than the indicated usage by up to a predetermined amount (which may be different for larger or smaller discrepancies). Such a system allows transmission to proceed if there is a false alarm of a transmission on an interlace that is not in fact being utilised. For example, there may be an erroneous measurement, or stray energy from a user in a neighbouring cell may be detected. In such situations, where one or a few interlaces are sensed as utilised, but were indicated as unutilised, transmission may be permitted provided the discrepancy is less than the predetermined amount. A further condition may be added such that if the UE’s assigned resource is sensed as being utilised transmission is not permitted, thus avoiding a direct conflict for use of resources.

[65] In the example of Figure 3 in which a Wi-Fi device has taken control of the resources, energy will be sensed on all interlaces, giving a discrepancy larger than the permitted discrepancy and hence transmission will not be permitted.

[66] The proposed NR radio formats include a range of sub-carrier configurations. For example, a 20 MHz spectrum may give 10 interlaces for 15KHz sub-carrier spacing (SCS) but only 10 and 5 interlaces for 10 RB/interlace if SCS is scaled to 30KHz and 60KHz respectively. There could yet exist further interlace designs with different footprints in time and frequency. The proposed resource utilisation indications may require different formats to accommodate the varying number of interlaces available. For example, a bitmap corresponding to the configuration with the largest number of interlaces may be utilised, and the information for other SCS based interlaces can be derived from this bitmap. Another possibility can be to design a bitmap for each specific interlace design only.

[67] Figure 6 shows further examples of resource allocation and utilisation. In particular, examples in which utilisation changes through a slot are shown. In Figures 6(a) and (b) UEO starts transmission at symbol #7 of a first slot (n). Figure 6(c) shows an example of UEO being allocated an entire slot, but UE1 is allocated a mini-slot, and Figure 6(d) shows an example where both UEs are allocated mini/sub-slot resources. In each of these examples UE1 is scheduled to start transmission when at least one other UE (UEO) is transmitting and hence conventional LBT mechanisms will not allow UE1 if it has the right to transmit or not, and hence requires knowledge that those transmissions are related to the same device group as UE1 in order to be able to commence transmission.

[68] A signalling mechanism is required to indicate resource utilisation to UEs such that they can assess their ability to transmit. Any UE related to a cell utilising the unlicensed resources, and configured to the current disclosure, may benefit from the resource utilisation indication.

[69] Group common signalling may be utilised to transmit resource utilisation to UEs. Each UE which is scheduled for transmission, or is in an RRC active state, may be placed in a group by allocating a RNTI. Control resources are allocated which can carry common resource utilisation signalling to the UEs with the assigned RNTI. Such a system allows sharing of control resources which may be attractive if there are a large number of UEs scheduling for UL transmission with different start symbols.

[70] The resource utilisation may be transmitted to UEs utilising a common DCI message. For example, the common DCI 1-C format may be utilised for which a known fixed RNTI is used, see Section 5.3.3.1.4 of 3GPP TS36.212-f10. An additional field may be added to the DCI 1-C format to carry the utilisation information. For example, a bitmap field as described above may be utilised. This DCI provides the sub-frame configuration for LAA. Resource utilisation information may be provided with a trigger as is the current two-stage DCI trigger mechanism for PUSCH on LAA in LTE. In this mechanism detailed in Section 8.0 of 3GPP TS36.213, the base station sends a first DCI with PUSCH trigger A (using one of the DCI formats 0A/0B/4A/4B) which schedules the resources for the UE with relative timing and defines a duration within which the scheduling is valid. The UE then waits to receive the 2^nd trigger, named as PUSCH trigger B, which provides the UL duration and offset and hence lets the UE compute its precise scheduling timing information. This PUSCH trigger B is sent in enhanced LAA using the DCI format 1C with a common RNTI. Thus, PUSCH trigger B is utilised to activate a PUSCH transmission by indicating UL duration and offset for a transmission which has been pre-scheduled to the user in a userspecific DCI with a PUSCH trigger A. The proposed resource occupancy indication can be embedded in this two stage PUSCH control mechanism by adding the resource occupancy information in the 2^nd DCI which serves as 2^nd trigger and provides the information to compute the precise timing information to the UE. In this way, the resource utilisation indication, although sent in the form of common signalling, can target the specific users.

[71] Although DCI 1-C signalling is common (or group-common) signalling, the use of a trigger helps to target the information to a specific UE. Thus, the information is sent such that it is decodable by the group, but the UE to which the information is relevant is able to use the information. In this sense, when a single user or very few users are targets of the information, DCI 1-C style common signalling can be efficient. However, when there are a large number of UEs related to a cell and scheduled in a given interval, the use of group DCI signalling may be less effective depending on the scheduling scenarios and start times of the UEs.

[72] If a large portion of the UEs (for example, over 50%, or all UEs) are scheduled to start transmission on the same, or a small sub-set of symbols, then group signalling may be efficient. However, the scheme may have limitations if the UEs are scheduled to start on a larger number of different symbols since the information relevant to each different start symbol is different.

[73] Figure 7 shows an example in which 4 UEs are scheduled on 5 interlaces during a slot. UEO is scheduled to occupy interlace 1 for the whole slot, UE1 and UE2 are both scheduled on interlace 3 but in different symbols. UE 4 is scheduled to transmit on interlace 4, starting at symbol 7. Resource utilisation bitmaps for each symbol are shown along the bottom of the figure.

[74] If the resource utilisation information is transmitted at the start of the slot it may indicate that only interlace 1 is utilised (01000), and it may be assumed this is valid for the duration of the slot. This information is valid for UE1 and UE4 and will enable those UEs to take a correct decision to start transmission if they detect that only interlace 1 is utilised, assuming sensing is performed immediately prior to their start symbol. A longer sensing period may cause UE4 to detect UETs transmission and may be an issue in deciding its transmission right. However, the information is less useful for UE2, since the interlace utilisation immediately prior to UE2 commencing transmission (01001) is different to that at the start of the slot (01000).

[75] To improve the relevance of the resource utilisation information, a time indication may be included. For example, two bits may be utilised for each interlace, with a first bit indicating utilisation in the first half of the slot, and a second bit indicating utilisation in the second half of the slot. The bitmap for the first half slot (relevant for UE1 and UE4) would be 01000, and for the second half of the slot would be 01001 (relevant for UE2). Utilising additional bits (up to, for example, one bit per symbol) improves the accuracy of the information and hence its relevance, but also increases the control overhead. Each UE only requires the resource utilisation prior to its allocated start symbol, and hence utilising additional bits in this way transmits redundant information to each UE (in the 2 bits per slot example, one bit is redundant for each UE as the UE’s start symbol is either in the first or second half of the slot, meaning the bit for the other half is not required). On the other hand, resource occupancy may still be different within the half-slot in certain cases and may need resource indication for a further smaller granularity.

[76] Where there are a wide range of start symbols it may be more efficient to utilise individual UE signalling such that only the required information is transmitted to each UE.

[77] UE-specific signalling of resource utilisation can be performed utilising user-specific DCI messages, for example the DCI which schedules the UL transmission can also include resource utilisation information for the cell. For example, an additional field may be added to the DCI message to indicate the resource utilisation. In the existing standards, DCI formats 0A, 0B, 4A, and 4B are utilised for resource scheduling and may be modified to include a resource utilisation indication.

[78] UE-specific signalling allows the information transmitted to each UE to match the situation it will experience at the time of performing its LBT function. That is, the resource utilisation may indicate the resource utilisation prior to the UE’s scheduled start symbol. For example, if the UE is scheduled to start its UL transmission in symbol N, the resource utilisation (e.g. a bitmap as described above) may be provided in relation to symbol N-1 where the UE will perform its LBT function.

[79] Due to short symbol times in some radio configurations, LBT sensing may be performed over more than one symbol prior to transmission starting, and hence the resource indication may be provided over a longer period, for example N-2 symbols. As will be apparent the relevant indication point can be defined according to the specific configuration, and the resource utilisation may be indicated for the most relevant symbol N-x, where x is an integer defining how many symbols in advance of the start symbol the utilisation information is relevant for. x may be indicated to the UE, or preconfigured.

[80] Figure 8 shows an example of UE-specific resource utilisation signalling for the same example shown in Figure 7. Assuming x = 1, the network transmits a utilisation indication of 01000 for UE1 and UE4. The indication transmitted to UE2 is 01001 since UE4 has started transmitting prior to UE2’s start symbol. Each UE thus receives a true indication of resource utilisation at the time of performing an LBT function and can hence perform an accurate comparison when determining whether to start transmission.

[81] The resource utilisation information is not an essential element of every DCI message, even for UEs operating in NR-U. The field(s) containing the information can there be declared optional and included by the base station only when they are required or are considered useful to a UE. UEs may be configured to blind-decode two DCI formats, one with and one without utilisation information and to use the information as required if it is included. Blind decoding adds some processing overhead but enables the reduction of control signalling overheads. Alternatively, each UE may be configured to expect, or not expect, utilisation information in its DCI messages. For example, the network may use RRC signalling to configure UEs about decoding the larger DCI with resource indication.

[82] A further signalling protocol includes a flag in a DCI message scheduling an UL transmission. The flag indicates if a second DCI message will be transmitted which includes resource utilisation information. This protocol reduces the overhead in the first DCI which is always transmitted to a single bit and enables UE-specific utilisation information to be transmitted in a second DCI message only when required or useful. In a variation, the second DCI message could be directed to a group of UEs having the same start symbol, or other grouping as may be useful.

[83] The techniques described above are equally applicable in a beam-sweeping system. However, it may be more likely that when performing LBT a UE may sense transmissions from UE’s in neighbouring beams due to physical constraints and the beam-forming capability of UEs. A UE may thus detect a mismatch between the indication of resources from the base station and the sensed resource utilisation, even though the UE is free to transmit within its beam area.

[84] This situation may be mitigated by the base station including resource utilisation from adjacent beams in the information transmitted to a UE. The base station has full scheduling information for all beams, and awareness of the location of UEs, and can thus make a reasonable estimate of the signals each UE may detect. The indicated resource utilisation may thus include resources utilised by different beams but which are likely to be detected by the UE.

[85] For grant-based UL transmissions, as discussed above, the base station is aware of all scheduled transmissions and can hence provide accurate indications of scheduled resource utilisation. However, in the case of grant-free transmission, semi-persistent scheduling or configured-grant a base station configures periodic resources as available to a UE and the UE decides whether to use those resources depending on its transmissions needs. In such cases the base station is not aware of which resources will actually be utilised for UL in each symbol, but only that certain resources may be utilised. The above systems would allow an indication of resources that might be used in each symbol, but that indication may not be accurate depending on the choice of each UE to use, or not use, its allocated resources.

[86] A base station may indicate resource utilisation to a configured-grant-based UE using a group-common DCI which is decodable by every user configured for configured-grant transmission. The indication whether they need this resource occupancy indication or not may be the part of the configured-grant based setup.

[87] As noted above the base station is not aware whether each UE will actually use an allocated resource, and hence cannot give a definitive indication. However, the base station is aware of which resources might be utilised and this can be indicated to each UE using the techniques described above. If resources have been allocated to a UE, they are indicated as utilised in the utilisation indication.

[88] The UEs may be configured to apply the subset rule discussed above, such that if the sensed resources are a subset of the indicated resources the UE is allowed to transmit. Sensing a subset of the indicated resources shows that some of the allocated resources have not been used and the discrepancy between sensed and indicated resources should not prevent transmission.

[89] In an alternative signalling protocol the indication field may include three options - free, busy, or configured for configured-grant-based transmissions. This provides a more precise indication to the UEs of the resource configuration and hence allows a more effective comparison and decision.

[90] The standards have standardized bandwidth part (BWP) operation in which a base station can configure multiple portions of the carrier bandwidth to the UE and one of these can be activated by the base station. This activation can be through RRC signalling or DCI based signalling. BWP operation facilitates the UE operation where carrier bandwidths are large. This is also the case in unlicensed bands where very large bandwidths are available. If a UE has been configured to use BWP operation in the unlicensed band, the resource occupancy indication signalling is provided in relation to the active BWP for the relevant UE.

[91] Throughout the disclosure, the embodiments have been described for 5G NR systems. The reader will appreciate that the principles and methods disclosed are applicable to any system for efficient user multiplexing operating over unlicensed spectrum. One example is LTE where future enhancements can use the methods disclosed here. As short-TTIs have been incorporated into LTE, if users scheduled for short-TTI UL transmissions have to be multiplexed, the problem is similar to the one treated here and can be solved by the principles described in this disclosure.

[92] 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.

[93] 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.

[94] 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.

[95] 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.

[96] 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.

[97] 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.

[98] 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 45 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.

[99] 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.

[100] 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.

[101] 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.

[102] 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.

[103] 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.

[104] 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.

[105] 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.

[106] 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 resource sharing in a cellular communication system, the method performed by a base station and comprising the steps of transmitting an indication from the base station to a UE indicating resources available for uplink (UL) transmissions from the UE to the base station; and transmitting an indication from the base station to the UE of UL transmission resources allocated to other UEs associated with the base station in a period prior to the start of the resources indicated as available to the UE for UL transmissions.

2. A method according to claim 1, wherein the resources are located in an unlicensed band.

3. A method according to claim 1 or claim 2, wherein the resources comprise a plurality of interlaces.

4. A method according to any preceding claim, wherein the indication of UL transmission resources allocated to other UEs comprises a bitmap field.

5. A method according to claim 4, wherein each bit of the bitmap corresponds to a group of physical resources.

6. A method according to claim 5, wherein the groups of physical resources are interlaces.

7. A method according to any preceding claim, wherein the indication of UL transmission resources allocated to other UEs is transmitted in a group-common DCI message.

8. A method according to claim 7, wherein the group-common DCI message is a DCI 1-C format DCI message.

9. A method according to any of claims 1 to 6, wherein the indication of UL transmission resources allocated to other UEs is transmitted in a UE-specific DCI message.

10. A method according to claim 9, wherein the UE-specific DCI message is a DCI message which also includes the indication of resources available for transmissions from the UE to the base station.

11. A method according to any of claims 1 to 6, wherein the indication of resources available for transmission from the UE to the base station comprises an indication of a subsequent message indicating the UL transmission resources allocated to other UEs.

12. A method according to any preceding claim, wherein the UL transmission resources allocated to other UEs includes resources allocated for configured-grant-based transmissions.

13. A method according to any preceding claim, wherein the UL transmission resources allocated to other UEs includes resources allocated to UEs associated with the base station but operating in a different beam to the UE.

14. A method according to any preceding claim, wherein the resource indication is the resource occupation for the symbol preceding the first symbol of the UE’s allocated resources.

15. A method according to any preceding claim, wherein the indication of UL transmission resources allocated to other UEs includes the utilisation at a plurality of different times.

16. A method according to any preceding claim, wherein the period is a Listen Before Talk (LBT) period of the UE.

17. A method of resource sharing in a cellular communication system, the method performed by a UE and comprising the steps of receiving an indication from a base station indicating resources available for uplink (UL) transmissions from the UE to the base station; and receiving an indication from the base station of UL transmission resources allocated to other UEs associated with the base station in a period prior to the start of the resources indicated as available to the UE for UL transmissions.

18. A method according to claim 17, wherein the resources are located in an unlicensed band.

19. A method according to claim 17 or claim 18, wherein the resources comprise a plurality of interlaces.

20. A method according to any of claims 17 to 19, wherein the indication of UL transmission resources allocated to other UEs comprises a bitmap field.

21. A method according to claim 20, wherein each bit of the bitmap corresponds to a group of physical resources.

22. A method according to claim 21, wherein the groups of physical resources are interlaces.

23. A method according to any of claims 17 to 22, wherein the indication of UL transmission resources allocated to other UEs is received in a group-common DCI message.

24. A method according to claim 23, wherein the group-common DCI message is a DCI 1-C format DCI message.

25. A method according to any of claims 17 to 22, wherein the indication of UL transmission resources allocated to other UEs is received in a UE-specific DCI message.

26. A method according to claim 25, wherein the UE-specific DCI message is a DCI message which also includes the indication of resources available for transmissions from the UE to the base station.

27. A method according to any of claims 17 to 26, wherein the indication of resources available for transmission from the UE to the base station comprises an indication of a subsequent message indicating the UL transmission resources allocated to other UEs.

28. A method according to any of claims 17 to 27, wherein the UL transmission resources allocated to other UEs includes resources allocated for configured-grant-based transmissions.

29. A method according to any of claims 17 to 28, wherein the UL transmission resources allocated to other UEs includes resources allocated to UEs associated with the base station but operating in a different beam to the UE.

30. A method according to any of claims 17 to 29, wherein the resource indication is the precise resource occupation for the symbol preceding the first symbol of the UE’s allocated resources.

31. A method according to any of claims 17 to 30, wherein the indication of UL transmission resources allocated to other UEs includes the utilisation at a plurality of different times.

32. A method according to any of claims 17 to 31, further comprising the step of performing a LBT process to identify utilised resources in the LBT period, wherein the UL only transmits in its allocated UL transmission resources if the utilised resources are the same as the resources indicated as allocated to other UEs.

33. A method according to any of claims 17 to 31, further comprising the step of performing a LBT process to identify utilised resources in the LBT period, wherein the UL only transmits in its allocated UL transmission resources if the utilised resources are the same as, or a subset of, the resources indicated as allocated to other UEs.

34. A method according to any of claims 17 to 31, further comprising the step of performing a LBT process to identify utilised resources in the LBT period, wherein the UL only transmits in its allocated UL transmission resources if the utilised resources are different to the resources indicated as allocated to other UEs by less than a predefined threshold.

35. A method according to any of claims 17 to 34, wherein the period is a Listen Before Transmit period of the UE.

36. A base station configured to perform the methods of any of claims 1 to 16.

37. A UE configured to perform the methods of any of claims 17 to 35.