WO2021023081A1

WO2021023081A1 - Sidelink feedback resource allocation

Info

Publication number: WO2021023081A1
Application number: PCT/CN2020/105534
Authority: WO
Inventors: Sebastian Wagner
Original assignee: JRD Communication (Shenzhen) Ltd.
Priority date: 2019-08-04
Filing date: 2020-07-29
Publication date: 2021-02-11
Also published as: CN114175803A

Abstract

There is provided a method of allocating resources of a resource pool of a UE for PSFCH transmissions comprising configuring at least one PSFCH resource set in the resource pool consisting of one or more time-frequency resources for the PSFCH transmissions. Configuring the at least one PSFCH resource set in the resource pool may comprise configuring the at least one PSFCH resource set to be specific to a single or multiple PSFCH formats. Configuring the at least one PSFCH resource set in the resource pool may comprise configuring the set to consist of time-frequency resources for the PSFCH transmissions comprising a slot periodicity, a slot periodicity offset, a time gap between a PSFCH and an associated PSSCH.

Description

Sidelink Feedback Resource Allocation

Technical Field

The following disclosure relates to the allocation of resource for sidelink feedback transmissions in a cellular communications network.

Background

Wireless communication systems, such as the third-generation (3G) of mobile telephone standards and technology are well known. Such 3G standards and technology have been developed by the Third Generation Partnership Project (3GPP) . The 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.

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

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

In conventional cellular communication networks, all signalling is between each mobile device and a base station rather than directly between mobile devices, even if the mobile devices are within wireless communication range of each other. This may lead to inefficient use of wireless transmission resources and may increase base station resource utilisation. Sidelink communications allow mobile devices to communicate directly rather than via a base station, potentially improving wireless and base station resource utilisation. Sidelink communications are considered particularly interesting for Machine to Machine communications, particularly Vehicle to Vehicle (V2V) and Vehicle to Everything/Anything (V2X) communications.

Summary

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

There is provided a method of allocating resources of a resource pool of a UE for PSFCH transmissions comprising configuring at least one PSFCH resource set in the resource pool consisting of one or more time-frequency resources for the PSFCH transmissions.

Configuring the at least one PSFCH resource set in the resource pool may comprise configuring the at least one PSFCH resource set to be specific to a single or multiple PSFCH formats.

Configuring the at least one PSFCH resource set in the resource pool may comprise configuring the set to consist of time-frequency resources for the PSFCH transmissions comprising a slot periodicity, a slot periodicity offset, a time gap between a PSFCH and an associated PSSCH. Configuring the at least one PSFCH resource set in the resource pool may comprise configuring the set to support frequency hopping.

There is also provided a method of multiplexing PSFCH resources for different PSFCH transmissions onto at least one PSFCH resource set.

Multiplexing the PSFCH resources may comprise using an implicit mapping between the PSFCH resources and associated PSCCH/PSSCH resources. The implicit mapping between the PSFCH resources and associated PSCCH/PSSCH resources may comprise setting a PSFCH resource offset within a PSFCH resource set equal to the sub-channel number of a first sub-channel of the associated PSCCH/PSSCH resources.

Multiplexing the PSFCH resources may comprise using explicit signalling of the PSFCH resources. The PSFCH resources may be dynamically signalled in DCI/SCI transmissions.

Multiplexing the PSFCH resources may comprise using dynamic signalling of a PSFCH resource offset. Multiplexing the PSFCH resources may comprise using a PSFCH resource multiplexing scheme which is configurable per resource pool. Multiplexing the PSFCH resources for different PSFCH transmissions may comprise allowing a UE to transmit multiple PSFCH transmissions in one slot.

There is also provided a method of allocating resources of a resource pool of a UE for PSFCH transmissions, comprising configuring at least one PSFCH resource set in the resource pool consisting of one or more time-frequency resources for the PSFCH transmissions; where the time-frequency resources are contiguous or non-contiguous in time-frequency; where configuring the at least one PSFCH resource set in the resource pool comprises configuring the set together with configuration of the resource pool.

A selection of optional features is set out in the dependent claims.

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

Brief description of the drawings

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

Figure 1 shows a schematic diagram of a cellular network.

Figure 2 shows an example of a sidelink slot structure, where PSFCH resources are multiplexed with PSCCH/PSSCH resources.

Figure 3 shows an example of inter-slot PSFCH resource allocation for two resource pools.

Figure 4 shows an example of PFSCH resource sets with different periodicities and periodicity offsets.

Figure 5 shows an example of PFSCH resource set hopping.

Figure 6 shows an example of possible PSFCH resource sets with different time-frequency configurations.

Figure 7 shows an example of configuration of a PSFCH resource set.

Figure 8 shows an example of PSFCH resource multiplexing using implicit mapping between PSFCH resources and associated PSCCH/PSSCH resources.

Figure 9 shows an example of PSFCH resource multiplexing using implicit mapping between PSFCH resources and associated PSCCH/PSSCH resources by setting a PSFCH resource offset equal to a first sub-channel number of the associated PSCCH/PSSCH resources.

Figure 10 shows an example of PSFCH resource multiplexing via explicit signalling of PSFCH resource offset.

Figure 11 shows an example of PSFCH multiplexing where PSFCH resources are configured every two slots for unicast transmissions.

Figure 12 shows an example of PFSCH resource multiplexing with periodicity equal to 2.

Detailed description of the preferred embodiments

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

Figure 1 shows a schematic diagram of three base stations (for example, eNB or gNBs depending on the particular cellular standard and terminology) forming a cellular network. Typically, each of the base stations will be deployed by one cellular network operator to provide geographic coverage for UEs in the area. The base stations form a Radio Area Network (RAN) . Each base station provides wireless coverage for UEs in its area or cell. The base stations are interconnected via the X2 interface and are connected to the core network via the S1 interface. As will be appreciated only basic details are shown for the purposes of exemplifying the key features of a cellular network. In the proposed NR protocols, the Uu interface is between the base station and UEs. A PC5 interface is provided between UEs for SideLink (SL) communications. The interface and component names mentioned in relation to Figure 1 are used for example only and different systems, operating to the same principles, may use different nomenclature.

The base stations each comprise hardware and software to implement the RAN’s functionality, including communications with the core network and other base stations, carriage of control and data signals between the core network and UEs, and maintaining wireless communications with UEs associated with each base station. The core network comprises hardware and software to implement the network functionality, such as overall network management and control, and routing of calls and data.

To achieve the required reliability and latency in SL communications in such a network, e.g. NR V2X communications, a Hybrid Automatic Repeat Request (HARQ) scheduling scheme is used for SL communications. For SL communications between a transmit UE and a receive UE, data is received by the receive UE on a Physical Sidelink Shared Channel (PSSCH) and Sidelink Control Information (SCI) is received on a Physical Sidelink Control Channel (PSCCH) . For unicast SL communications, when SL feedback is enabled, when a receive UE successfully receives and decodes SCI and successfully receives associated data, the receive UE will send a HARQ Acknowledgement (HARQ-ACK) feedback as part of Sidelink Feedback Control Information (SFCI) to the transmit UE via a Physical Sidelink Feedback Channel (PSFCH) . When the receive UE successfully receives and decodes the SCI but does not successfully receive the data, the receive UE will send a HARQ Negative Acknowledgement (HARQ-NACK) feedback as part of SFCI to the transmit UE via the PSFCH.

Sidelink transmissions utilise TDD (half duplex) on either a dedicated carrier, or a shared carrier with conventional Uu transmissions between a base station and UE. Resource pools of transmission resources are utilised to manage resource and allocation and manage interference between potentially concurrent transmissions. A resource pool is a set of time-frequency resources from which resources for a transmission can be selected. UEs can be configured with multiple transmit and receive resource pools.

Two modes of operation are proposed for resource allocation for sidelink communication. A first mode (mode 1) is applied when UEs are in coverage of a base station and resources are allocated by the base station. A second mode (mode 2) is utilised when UEs are not in coverage of a base station and the UEs select and utilise resources autonomously, typically utilising a listen-before-transmit process.

UEs reserve resources for a transmission by transmitting a SCI message indicating the resources to be used. The SCI notifies the recipient (which may be a single UE in unicast, a group of UEs in groupcast, or all reachable UEs in broadcast) of the details of the transmission it can expect. UEs may reserve transmission resources both for a first transmission of a Transport Block (TB) of data, and also for transmitting repetitions of the TB to improve reliability if the initial transmission fails.

With respect to scheduling and procedures for SFCI communications via a PSFCH, the following agreements have been reached. At least for sidelink HARQ feedback, NR sidelink supports at least a PSFCH format which uses resources comprising one or more last symbol (s) available for sidelink communications in a slot. At least from a transmission perspective of a UE, at least TDM between PSCCH/PSSCH resources and PSFCH resources is allowed. At least for the case when the PSFCH in a slot is in response to a single PSSCH, an implicit mechanism is used to determine at least frequency and/or code domain resources for the PSFCH within a resource pool.

An example of a SL slot structure is shown in Figure 2, where PSFCH resources are multiplexed, using TDM, with PSCCH/PSSCH resources. Note that the PSFCH is not necessarily associated with the PSSCH in the same slot. If a UE is scheduled to receive on the PSSCH and subsequently transmit on the PSFCH, then a transient period is needed to switch from reception to transmission. Similarly, if a UE receives a PSFCH communication in the same slot as a PSSCH communication, a transient period is required.

For inter-slot resource scheduling, the following agreements have been reached. (Pre) configuration indicates the time gap between a PSFCH resource and an associated PSSCH resource. Within slots associated with a resource pool, PSFCH resources can be (pre) configured with a period of N slot (s) . A PSFCH resource can be (pre) configured to occur periodically every slot, every 2 slots, every 4 slots. A PSFCH resource can be (pre) configured to not occur at all. This (pre) configuration is resource pool specific. A PSFCH transmission is only transmitted in the same resource pool as the associated PSSCH transmission.

An example of inter-slot resource scheduling of PSFCH resources for two resource pools is shown in Figure 3. The time gap between a PSFCH resource and an associated PSSCH resource is (pre) configured (common understanding is per resource pool) meaning no dynamic signalling is supported. Resource pool 0 has PSFCH resource occurrences every 2 sidelink slots (N = 2) and resource pool 1 has PSFCH resource occurrences every 4 sidelink slots (N = 4) .

Regarding the payload of the PSFCH, i.e. HARQ-ACK/NACK feedback, the following agreements have been reached. HARQ feedback can be enabled or disabled per UE through higher layer signalling. It is also possible that HARQ feedback is disabled in the resource pool configuration of a UE, i.e. there are no PSFCH resources configured in the resource pool. In the case of unicast communication, the HARQ payload is simple, the UE transmits the HARQ ACK/NACK feedback on the associated PSFCH. The situation is more complex in groupcast transmissions since feedback has to be transmitted/received from multiple UEs. At the moment there are two options: all UEs in the group transmit (i) only HARQ-NACK feedback or (ii) HARQ-ACK/NACK feedback . For option 1, all UEs share one PSFCH resource. Since the TX-UE does not need to distinguish the UEs from their feedback, it is possible that all UEs send the same HARQ-NACK feedback sequence. For option 2, each receiver UE uses a separate PSFCH resource for HARQ ACK/NACK feedback. Each PSFCH is mapped to a time, frequency, and code resource.

Only a few agreements have been reached concerning the physical structure of the PSFCH. A sequence-based PSFCH format with one symbol is supported. This is applicable for unicast and

groupcast including options

1 and 2 above. The sequence of PUCCH format 0 is the starting point for developing 5G-V2X PSFCH formats.

A problem with the agreements on PSFCH scheduling is that only one PSFCH resource may be allocated within a slot. Another problem is that (pre) configuring the time gap between a PSSCH resource and an associated PSFCH resource results in (pre) configuring a minimum latency for transmissions and traffic types with different latency requirements cannot be supported within one resource pool.

The time-frequency resources may be contiguous in time-frequency. The time-frequency resources may be non-contiguous in time-frequency. The time-frequency resources may be used by the UE to transmit SFCI.

Configuring the at least one PSFCH resource set in the resource pool may comprise configuring the at least one PSFCH resource set to be specific to a single PSFCH format. The PSFCH resource set specific to a single PSFCH format may consist of time-frequency resources having the same format. The PSFCH resource set specific to a single PSFCH format may consist of time-frequency resources having the same type. The PSFCH resource set specific to a single PSFCH format may consist of time-frequency resources having the same size. For example, a first PSFCH resource set may be specified for a sequence-based PSFCH format similar to PUCCH format 0 and a second PSFCH resource set may be configured for a coded PSFCH format similar to PUCCH format 2. Configuring the PSFCH resource set to be specific to a single PSFCH format facilitates implicit PSFCH multiplexing and using implicit signalling to indicate a PSFCH resource.

Configuring the at least one PSFCH resource set in the resource pool may comprise configuring the at least one PSFCH resource set to be specific to multiple PSFCH formats. The multiple different PSFCH formats of the PSFCH resource set will use the same number of symbols. The multiple different PSFCH formats can be multiplexed in the PSFCH resource set through explicit signalling of the PSFCH resource, e.g. explicit signalling is used to indicate the frequency location.

Configuring the at least one PSFCH resource set in the resource pool may comprise configuring the set to consist of time-frequency resources for the PSFCH transmissions comprising a slot periodicity and a slot periodicity offset. Multiple PSFCH resource sets can be configured, each consisting of different periodicities and periodicity offsets. This allows, for example, a first PSFCH resource set to be available every even slot and a second PSFCH resource set to be available every odd slot. Further the UE, or a base station of the UE, may schedule PSFCH transmission requiring a lot of PSFCH resources (e.g. groupcast transmission with ACK/NACK feedback) such that the PSFCH transmission occurs in a slot with a large PSFCH resource set. An example is shown in Figure 4, where PSFCH0 is configured in every SL slot (slot periodicity = 1) , PSFCH1 is configured in every even SL slot (slot periodicity = 2) and PSFCH3 is configured in every odd SL slot (slot periodicity = 2, slot periodicity offset = 1) .

Configuring the at least one PSFCH resource set in the resource pool may comprise configuring the set to consist of a time-frequency resource for the PSFCH transmissions comprising a time gap between a PSFCH and an associated PSSCH. This enables traffic types with different latency requirements. For example, in Figure 4 the resource set PSFCH0 occurs every slot and hence has the potential to support low latency services. If the PSSCH-PSFCH gap were to be configured to 0 slots, a UE could receive the PSSCH and transmit the associated PSFCH within the same slot (assuming sufficient UE capabilities) . At the same time, mode-2 UEs sensing the PSSCH transmission are aware of the PSFCH resource set configuration and can implicitly deduce the PSFCH resource for the corresponding PSFCH transmission. Thus this UE resource pool with its different PSFCH resource set configurations can be shared between mode-1 and mode-2 users.

Configuring the at least one PSFCH resource set in the resource pool may comprise configuring the set to support frequency hopping according to a configurable pattern. An example is shown in Figure 5, where PSFCH0 is changing frequency location with every SL slot.

Configuring the at least one PSFCH resource set in the resource pool may comprise configuring the set to be specific to a UE group. A base station can configure a group-dedicated PSFCH resource set, e.g. during group configuration. This resource set can then be configured according to the group feedback requirements. The groupcast transmission will then automatically use this PSFCH resource set.

Configuring the at least one PSFCH resource set in the resource pool may comprise configuring the set to allow CBG-based feedback. Feedback for CBG requires more PSFCH resources and thus it may be beneficial to only allow CBG feedback on certain PSFCH resource sets.

Configuring the at least one PSFCH resource set in the resource pool may comprise configuring the set to be associated with a part of frequency resources within the resource pool. The PSFCH resource set may be associated with a certain frequency range within the resource pool. The PFSCH resource set may define an associated PSCCH/PSSCH frequency range. If the first allocated sub-channel for PSCCH/PSSCH lies within the frequency range, then this transmission uses the corresponding PSFCH resource pool for feedback. Note that multiple transmissions can be scheduled in the frequency range and hence they will use the same PSFCH resource set.

Configuring the at least one PSFCH resource set in the resource pool may comprise configuring the set to associate a PSSCH transmission to the PSFCH resource set. The PSSCH transmission may be implicitly associated to the PSFCH resource set. The PSSCH transmission may be explicitly associated to the PSFCH resource set. The PSSCH transmission can be directly associated to the PSFCH resource set through dynamic signalling in DCI/SCI. The dynamic signalling can comprise an ID of the PSFCH resource set. The PSSCH transmission may be implicitly associated to the PSFCH resource set by resource allocation of the associated PSSCH, e.g. if the PSFCH resource set is sub-channel dependent. The PSSCH transmission may be implicitly associated to the PSFCH resource set by PSFCH format to transmit, e.g. if PSFCH format 2 is required for feedback, then only PSFCH resource sets that allow this format are to be considered. The PSSCH transmission may be implicitly associated to the PSFCH resource set by CBG-based feedback, e.g. some PSFCH resource sets might allow CBG feedback and others might not.

Configuring the at least one PSFCH resource set in the resource pool may comprise configuring the set together with configuration of the resource pool.

The method may further comprise configuring the resource pool to comprise a list of PSFCH resource sets. The list of PSFCH resource sets in a resource pool can be empty, i.e. no HARQ feedback is supported in the resource pool.

An example of possible PSFCH resource sets with different time-frequency configurations is given in Figure 6. In this example, the resource sets consist of contiguous time-frequency resources. The resource sets could also contain a list of time-frequency resources each configured separately like NR PUCCH resource allocation.

An example of configuration of a resource pool is given in Figure 7. Note that the PSFCH resource set is configured in terms of sub-channels, because the remaining resources in the frequency domain may be used for PSSCH which can only be allocated on a sub-channel-based granularity. The granularity of the sub-channel is the same as configured for the resource pool and hence is not part of the PSFCH resource set configuration.

It can be seen that a PSFCH resource set can be defined as a group of PSFCH time-frequency resources that can be configured with different properties, e.g. periodicity, periodicity offset, PSSCH-PSFCH gap, frequency hopping, etc. This allows for a very flexible allocation of feedback resources tailored to various requirements of, for example, the new V2X services (low latency, high throughput, etc. ) . The proposed PSFCH resource set allows for a flexible allocation of HARQ feedback resources and increases the feedback resource efficiency in 5G sidelink communications.

We first consider multiplexing PSFCH resources when associated PSCCH/PSSCH transmissions occur on different sub-channels but in the same slot. If PSSCH transmissions are scheduled on different sub-channels in the same slot, their associated PSFCH feedback transmissions have to be multiplexed as well.

Multiplexing the PSFCH resources may comprise using an implicit mapping between the PSFCH resources and associated PSCCH/PSSCH resources.

Implicit allocation of PSFCH resources has the advantage that it allows UEs to sense the associated PSCCH/PSSCH transmission and directly derive the location of the mapped PSFCH resource. However, an implicit mapping is not resource efficient due to its inflexibility. Implicit mapping of PSFCH resources with associated PSCCH/PSSCH resources is supported. One straightforward scheme is to map the PSFCH resource to the first sub-channel used by the associated PSCCH/PSSCH resource. An example is depicted in Figure 8, where four UEs are transmitting on different sub-channels. Although the mapping is simple, it is clear from Figure 8 that the PSFCH resource utilization is poor. From 20 PRBs available, only 4 are used for transmitting PSFCH transmissions.

The implicit mapping between the PSFCH resources and associated PSCCH/PSSCH resources may comprise setting a PSFCH resource offset within a PSFCH resource set equal to the sub-channel number of a first sub-channel of the associated PSCCH/PSSCH resources.

Association of the PSFCH resource offset with the sub-channel number of the associated PSCCH/PSSCH transmission within the resource set improves the PSFCH resource utilization. For example, in Figure 9 there are 5 sub-channels, the first sub-channel of the transmission of UE2 is sub-channel 3 and hence the PSFCH resource offset is 3. It can be observed from Figure 9 that the PSFCH resource set needs to be at least 5 PRBs in bandwidth (more generally n _subCHsize PRBs ²) . However, since PSFCH resource allocation is likely in terms of sub-channels, two sub-channels must be available. Hence, out of 8 PSFCH resource only 4 are used in this example. This scheme is efficient if a large number of transmissions are scheduled that each only occupy a small number of sub-channels. On the contrary, it is less efficient if only a small number of transmissions are scheduled each spanning many sub-channels.

Dynamic signalling is very efficient but comes with a signalling overhead as well as the fact that UEs need to decode control information to know the exact PSFCH resource location. To improve resource efficiency the PSFCH resources should be allocated as shown in Figure 10. In this example the PSFCH resources of all four transmissions can be allocated to only 4 PRBs. The remaining resources can be used for instance to schedule PSSCH resources (if no half-duplex issues arise) or to configure another PSFCH resource set. In the example UE0, UE1 and UE2 could use the last 2 symbols for PSSCH resources assuming they transmit feedback in another slot. To enable such a scheme, an offset has to be associated with each transmission. In the example of Figure 10, the PSFCH resource set is allocated on the sub-channel spanning PRBs 0-3. The offset can be relative to the first PRB of the PSFCH resource set, i.e. UE0, UE1, UE2 and UE3 have

offsets

0, 1, 2, 3 PRBs, respectively. To address every PSFCH resource in this resource set example, consequently requires 2 bits. In general the number of bits for the PSFCH resource offset is given by

where n _subCHsize is the sub-channel size,

is the number of sub-channels of the PSFCH resource set and

is the number of PRBs per PSFCH resource, respectively.

Obviously, the larger the PSFCH resource set, the more bits for the offset are required. For optimal multiplexing, the offset needs to be signalled dynamically since the number of transmissions as well as their bandwidths can vary every slot.

Multiplexing the PSFCH resources may comprise using dynamic signalling of a PSFCH resource offset. The PSFCH resource offset may be dynamically signalled in DCI/SCI transmissions.

Multiplexing the PSFCH resources may comprise using a PSFCH resource multiplexing scheme which is configurable per resource pool. Depending on the nature of communication in a resource pool, either implicit or explicit signalling of the PSFCH resources can be beneficial. Thus it is desirable that the multiplexing scheme is configured for each resource pool.

We now discuss PSFCH resource multiplexing of transmissions occurring in different slots.

Multiplexing the PSFCH resources for different PSFCH transmissions may comprise allowing a UE to transmit multiple PSFCH transmissions in one slot.

If the PSFCH periodicity N > 1, it is necessary to multiplex the feedback of transmissions from different slots onto the PSFCH resources in one slot. Figure 11 depicts a simple example of PSFCH multiplexing where PSFCH resources are configured every 2 slots for unicast transmissions. We assume that the time gap between a PSSCH resource and an associated PSFCH resource is configured to 2 slots, i.e. the earliest feedback for a PSSCH transmission in slot n is in slot n + 2.

When reception of a PSSCH transmission is by the same UE in two consecutive slots, a UE receives a transmission in slot n and slot n + 1. The earliest feedback is n + 2 and n + 3 but since there is no PSFCH resource in slot n + 2, the feedback of both transmissions has to be sent in slot n + 3. The UE may transmit a HARQ-ACK feedback on separate PSFCH resources. This requires that a UE is capable of transmitting multiple PSFCH in the same slot. Alternatively, the UE may transmit a HARQ-ACK feedback for both transmissions on the same PSFCH resource. This requires the possibility that a PSFCH can carry multiple bits. PUCCH format 0 can carry only 2 bits and is hence not sufficient for N > 2. Therefore, allowing a UE to transmit multiple PSFCH transmissions in one slot is necessary:

When reception of a PSSCH transmission is by two different UEs in two consecutive slots, the two transmissions can use the same PSFCH resource, but each UE needs to know what sequences to transmit so that they do not interfere with each other.

Multiplexing the PSFCH resources for different PSFCH transmissions in different slots may follow the rule n _PSFCH = n mod N where N is a periodicity of the PSFCH resource, n _PSFCH is a PSFCH resource index and n is a slot number in which an associated PSSCH is received.

The previous sections addressed the problem of multiplexing PSFCH resource for PSFCH transmissions occurring in different slots or in different sub-channels. However, in general a PSFCH resource set can be configured with N > 1 and support multiple PSFCH transmissions per slot, i.e. the resource pool consists of more than one sub-channel.

Figure 12 shows an example of PSFCH resource multiplexing with N = 2. The mapping rule given above for multiplexing different transmissions in different slots is combined with different methods for sub-channel to PSFCH resource mapping. Scheme S1 uses the direct sub-channel mapping rule whereas scheme S2 uses the first sub-channel to PSFCH resource rule. Scheme S3 is the dynamic scheme with signalling of the PSFCH offset. It can be observed that an implicit mapping results in fragmented PSFCH transmissions, i.e. a UE is required to send multiple PSFCH in non-adjacent PRBs. This is undesirable since it can lead to interference from in-band emissions. However, the implicit mapping of sub-channel number to PSFCH resource is more resource efficient and results in less fragmentation. Note that if N is greater than the sub-channel size, the mapping rule in S2 needs to be modified. In this case it could be better to use multiplexing scheme S1. Only a dynamic signalling of the PSFCH resource offset can achieve high resource efficiency and allows contiguous PSFCH resources per UE. Thus we propose to extend the dynamic signalling of the offset to the case N > 1.

Multiplexing the PSFCH resources may comprise using dynamic signalling of a PSFCH resource offset when a periodicity of the PSFCH resource is greater than 1. This may comprise introduction of an offset parameter addressing different PSFCH resources within the PSFCH resource set to map PSFCH resources to the PSFCH resource set. The offset parameter may be signalled in DCI/SCI scheduling the transmission.

The minimum granularity of the offset parameter is the minimum frequency allocation of a PSFCH resource (e.g. one PRB) , but this would result in a high control overhead and is also not necessary. In the multiplexing of the PFSCH resources the PSFCH transmission of one UE may be adjacent. This minimizes in-band emissions. Therefore, PSSCH resources of one UE in consecutive slots are mapped to adjacent PRBs in the PFSCH resource set.

The number of offsets N _offset is limited by the size of the PSFCH resource set to

where n _subCHsize is the sub-channel size of the resource pool and

and N the number of sub-channels and periodicity of the PSFCH resource set, respectively. The offset L should have a granularity in terms of PSFCH resource bandwidth of L = N.

There can only be as much parallel transmission in a resource pool as there are sub-channels in the resource pool. Thus there must be as many PSFCH resources as there are sub-channels. In Figure 12, there are 5 sub-channels and N = 2, therefore the PSFCH resource set should consist of 5 X 2 = 10 PSFCH resources. Thus 5 offsets are required: 0, 2, 4, 6, 8.

A special case is groupcast transmission with ACK/NACK feedback where one transmission is destined to a group of users but each user is required to send feedback on a PSFCH resource. It has been proposed to use the UE ID within the group to derive the PSFCH resource location. In connection-based groupcast another solution could be to reserve a PSFCH resource set to the group (as proposed earlier) and assign a dedicated PSFCH resource within the set for each group member. For instance, the UE in the group is signalled an offset within PSFCH resource set.

Multiplexing the PSFCH resources may comprise for SL groupcast transmissions assigning a dedicated PSFCH resource to each group member during group configuration.

To avoid PSFCH collisions with other transmissions, assign a dedicated PSFCH resource set to the group. The same can be applied for mixed feedback, i.e. part of the users use ACK/NACK feedback and another part use NACK only. In case the whole group is configured with NACK-only feedback, the same PSFCH multiplexing and mapping applies as for unicast.

Advantages of the proposed methods include: Resource utilization: PSFCH resources are minimized and freed-up resource can be utilized for different purposes. Flexibility: PSFCH resources can be configured to the specific requirements of a transmission or service. Coexistence of different services: for example, within a resource pool, two PSFCH resource sets can be configured, a smaller one with high periodicity and a short PSSCH-PSFCH resource gap for low latency services, and a larger one with higher multiplexing capacity, lower periodicity, a larger PSSCH-PSFCH gap for high connectivity services.

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

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

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

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

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

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

In this document, the terms ‘computer program product’ , ‘computer-readable medium’ and the like may be used generally to refer to tangible media such as, for example, a memory, storage device, or storage unit. These and other forms of computer-readable media may store one or more instructions for use by the processor comprising the computer system to cause the processor to perform specified operations. Such instructions, generally 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.

The non-transitory computer readable medium may comprise at least one from a group consisting of: a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a Read Only Memory, a Programmable Read Only Memory, an Erasable Programmable Read Only Memory, EPROM, an Electrically Erasable Programmable Read Only Memory and a Flash memory. In an embodiment where the elements are implemented using software, the software may be stored in a computer-readable medium and loaded into computing system using, for example, removable storage drive. A control module (in this example, software instructions or executable computer program code) , when executed by the processor in the computer system, causes a processor to perform the functions of the invention as described herein.

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

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

Aspects of the invention may be implemented in any suitable form including hardware, software, firmware or any combination of these. The invention may optionally be implemented, at least partly, as computer software running on one or more data processors and/or digital signal processors or configurable module components such as FPGA devices.

Thus, the elements and components of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way. Indeed, the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the present invention is limited only by the accompanying claims. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognise that various features of the described embodiments may be combined in accordance with the invention. In the claims, the term ‘comprising’ does not exclude the presence of other elements or steps.

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

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

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

Claims

A method of allocating resources of a resource pool of a UE for PSFCH transmissions, comprising

configuring at least one PSFCH resource set in the resource pool consisting of one or more time-frequency resources for the PSFCH transmissions;

where the time-frequency resources are contiguous or non-contiguous in time-frequency;

where configuring the at least one PSFCH resource set in the resource pool comprises configuring the set together with configuration of the resource pool.
A method according to claim 1, where the PSFCH resource set is associated with a frequency range within the resource pool and comprises a set of PRBs.
A method according to claim 1, where configuring the at least one PSFCH resource set in the resource pool comprises configuring the at least one PSFCH resource set to consist of a time-frequency resource for PSFCH transmissions such that there is a time gap between a PSFCH and an associated PSSCH.
A method according to claim 3, where the time gap between a PSSCH resource and an associated PSFCH resource is defined as a number of slots.
A method according to claim 4, where the number of slots is 0 or 2.
A method according to claim 1, wherein PSFCH resources for different PSFCH transmissions are multiplexed into the at least one PSFCH resource set, where the multiplexing comprises mapping PSFCH resources to the associated PSCCH/PSSCH resources which comprises setting a PSFCH resource offset within a PSFCH resource set equal to the sub-channel number of a first sub-channel of the associated PSCCH/PSSCH resources.
A method according to claim 1, wherein the at least one PSFCH resource set consists of a number of sub-channels multiplied by the PSFCH periodicity.
A method according to claim 6, where multiplexing PSFCH resources comprises allowing a UE to transmit multiple PSFCH transmissions in one slot.
A method according to claim 1, where configuring the at least one PSFCH resource set in the resource pool comprises configuring the at least one PSFCH resource set to support frequency hopping according to a configurable pattern.