WO2020211951A1

WO2020211951A1 - Devices and methods for increasing scheduling capacity for bidirectional communication in a 5g system

Info

Publication number: WO2020211951A1
Application number: PCT/EP2019/060166
Authority: WO
Inventors: Sandip GANGAKHEDKAR; Karthikeyan Ganesan; Daniel Medina; Josef Eichinger; Zhongfeng Li
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2019-04-18
Filing date: 2019-04-18
Publication date: 2020-10-22

Abstract

New control signaling formats are used to efficiently schedule bidirectional communication between communicating nodes in a 5G system, particularly aiming to increase scheduling capacity in the 5G system. A scheduling node is assigns at least one first resource for a first communication direction and at least one second resource for a second communication direction of the bidirectional communication; and sends a scheduling grant message including information indicative of the at least one first resource and the at least one second resource to at least one of the communicating nodes. A communicating node receives a scheduling grant message including information indicative of at least one first resource and at least one second resource from the scheduling node, wherein the at least one first resource is for a first communication direction and the at least one second resource is for a second communication direction of the bidirectional communication.

Description

DEVICES AND METHODS FOR INCREASING SCHEDULING CAPACITY FOR BIDIRECTIONAL COMMUNICATION IN A 5G SYSTEM

TECHNICAL FIELD

The present invention relates to control channel enhancements, in particular, control channel enhancements to support ultra-reliable low-latency communication (URLLC) in 5G. The invention thus proposes control channel enhancements to support URLLC in 5G with the goal of increasing scheduling capacity, i.e., how many user equipments (UEs) can be scheduled simultaneously, e.g., by a base station.

BACKGROUND

Typically, in factory automation use cases, such as motion control or control-to-control communication, communication is cyclic and bidirectional in nature. Cyclic communication, in the context of control systems, implies that a Master sends a command to a Slave, and receives a feedback from the Slave within a strict period known as the cycle time. Bidirectional communication refers to a two-way communication between two or more devices. Both cyclic and bidirectional communication may be deterministic or time- critical, and typically requires low latency and very high reliability, which in itself is a challenge for wireless communication that is inherently stochastic in nature.

The Physical Downlink Control Channel (PDCCH) is used to transmit dynamic scheduling grants from a base station (e.g., gNB) to a user (e.g., UE), which contain Downlink Control Information (DCI) indicating the allocated Physical Downlink Shared Channel (PDSCH), Physical Uplink Shared Channel (PUSCH) or Physical Sidelink Shared Channel (PSSCH) time/frequency resource, modulation and coding scheme (MCS), and other transmission parameters. The gNB provides downlink (DL) assignments as well as uplink (UL) and sidelink (SL) grants for UEs. However, considering future industrial use cases, which require ultra-low latency and high reliability, the required PDCCH reliability to achieve a given data channel reliability is very high. For example, transmitting a URLLC payload (data packet) of 32 Bytes with 99.9999% reliability within 1 ms over the air interface requires the control channel to have at least 99.9999% reliability, and often even up to one order of magnitude higher. However, the resources for control channel signaling are limited, which becomes a bottleneck for supporting many simultaneous URLLC connections. This is the URLLC scheduling capacity problem: namely, how many UEs with URLLC transmissions can be scheduled simultaneously by the gNB.

The URLLC scheduling capacity problem arises due to PDCCH blocking. The larger the number of UEs is, which has to be supported, the more likely it is that packets to different UEs have to be sent simultaneously. Given the potential need for high aggregation levels (due to high reliability requirements of URLLC), one or two PDCCH transmissions might already block the search space for other users, which then cannot be scheduled immediately and might violate the prescribed latency requirement (See Table 1). This drastically reduces the PDCCH scheduling capacity for URLLC traffic and the suitability of 5G for industrial communication.

Table 1: Percentage of PDCCH blocked packets

The aforementioned PDCCH scheduling capacity problem has been addressed in the following ways: 1. Compact DCI:

In 3GPP Release 16 discussions, compact DCI is introduced by reducing the DCI payload size, which in turn improves the PDCCH BLER performance, since the effective code rate is much lower and fewer resources are used. Hence, to achieve the same reliability for a small DCI payload, fewer resources are needed, which reduces the PDCCH blocking probability. However, compact DCI is specified separately for

UL and DL and does not exploit the bidirectional and periodic data traffic. Further optimizations are possible for bidirectional or cyclic traffic patterns. 2. Configured Grant Type 2:

Configured Grant Type 2, which is essentially semi -persistent scheduling (SPS), lacks flexibility for scheduling cyclic deterministic traffic. DL SPS assignment is based on periodically configured slots, whereas UL SPS assignment is based on periodically configured symbols in a slot. This asymmetric scheduling granularity increases the scheduling delay (and cycle time) for cyclic traffic. Furthermore, semi-persistently scheduling bidirectional periodic traffic requires two separate SPS configurations for the DL and UL. Configured grant procedures described in TS 38.321 Sec. 5.8 require enhancements to support short deterministic cycle times and high reliability.

3. Mini- slot scheduling:

5G NR allows for mini- slot scheduling, which can be used to increase the PDCCH scheduling capacity and flexibility by assigning more OFDM symbols in a slot to PDCCH, as shown in FIG. 1. However, this additional PDCCH capacity comes at the cost of reduced data channel (PDSCH, PUSCH and/or PSSCH) capacity. This is because the number of information bits reserved for a particular DCI format on the PDCCH remains unchanged, and only the total number of bits allocated to the PDCCH is increased. Hence, in terms of resource efficiency, mini- slot scheduling does not provide any gains.

4. PDCCH repetitions and Fast feedback:

Time-domain PDCCH repetitions with lower Aggregation Level can alleviate PDCCH blocking. However, PDCCH repetitions are applied for DL and UL grants separately and do not exploit potential gains for bidirectional or cyclic traffic.

Fast feedback (ACK/NACK) between two PDCCH repetitions prevents unnecessary PDCCH repetitions. However, for very short cycle times (e.g., 0.5 ms), repetitions may not meet the latency requirements.

SUMMARY

In view of the above-mentioned problems and disadvantages, the present invention aims to improve the conventional approaches. An objective is to efficiently schedule communication, for example bidirectional communication, in a 5G network. Efficient scheduling of bidirectional communication may, for example, be achieved by providing new control signaling formats which may combine resource assignments for one or more links, nodes or directions of communication, in a single control message, thus should increase the resource efficiency of the control channel. The proposed control signaling formats can be applicable for both single-hop and multi-hop communication (multi- node). Further, the control signaling can be applicable on the cellular link or on the direct link between devices (sidelink). The control message could be a dynamic grant or a configured grant (e.g., for periodic traffic).

The objective is achieved by the embodiments provided in the enclosed independent claims. Advantageous implementations of the embodiments of the present invention are further defined in the dependent claims.

A first aspect of the invention provides a scheduling node for scheduling bidirectional communication between at least two communicating nodes, the scheduling node being configured to: assign at least one first resource for a first communication direction and at least one second resource for a second communication direction of the bidirectional communication; and send a scheduling grant message including information indicative of the at least one first resource and the at least one second resource to at least one of the communicating nodes.

New control signaling formats, which combine resource assignments for one or more links, nodes or directions of communication, can thus be realized by the device. The control signaling provided in a single control message results in an increase of the resource efficiency of the control channel. The proposed control signaling formats are applicable for both single-hop and multi-hop communication (multi-node). Further, the control signaling may be applied on the cellular link or on the direct link between devices (e.g., sidelink). The control message may be a dynamic grant or a configured grant (e.g., for periodic traffic).

In an implementation form of the first aspect, the scheduling node is one of the communicating nodes. The scheduling node may thus schedule bidirectional communication between the scheduling node and other communicating nodes.

In an implementation form of the first aspect, the information indicative of the at least one first resource and the at least one second resource comprises one or more of time and/or frequency allocation for the first communication direction, and a relative time and/or frequency offset for the second communication direction, the offset being relative to the time and/or frequency allocation for the first communication direction.

In an implementation form of the first aspect, the scheduling node is configured to receive at least one scheduling request from at least one of the communicating nodes, wherein the scheduling request includes information about the bidirectional communication; obtain a plurality of transmission parameters; and send the scheduling grant message according to the information in the scheduling request and the obtained transmission parameters.

The scheduling node may thus decide on the grant configuration based on received information about the cycle time, topology, protocol information, payload size, timing information, etc.

In an implementation form of the first aspect, the transmission parameters comprise one or more of: a DL MCS, an UL MCS, a SL MCS, a Channel State Information, CSI, request indicator, an indication of a data or payload size to be transmitted and/or its characteristics, information about a data or payload processing time or an update to an earlier reported processing time.

The transmission parameters may be specified considering both DL and UL traffic. SL traffic may be also considered depending on communication scenarios.

In an implementation form of the first aspect, the bidirectional communication is a single hop communication or a multi- hop communication.

A single grant may schedule a bidirectional communication between any two nodes, and it may also apply to a group of UEs with multi-hop connections for various topologies. In an implementation form of the first aspect, the scheduling grant message is valid for a single instance communication or for a single communication cycle.

In this way, the scheduling grant applied only for a single instance communication or for a single communication cycle may be specified as a dynamic grant.

In an implementation form of the first aspect, the at least one first resource is for a DL transmission or for a SL forward transmission in the bidirectional communication, and/or the at least one second resource is for an UL transmission or for a SL reverse transmission in the bidirectional communication.

In other words, the first communication direction is the DL transmission and/or the SL forward transmission. The second communication direction is the UL transmission and/or the SL reverse transmission.

In an implementation form of the first aspect, the scheduling grant message further comprises information about a symbol offset for the second communication direction, the offset being relative to the time allocation for the first communication direction.

For instance, the symbol offset or slot offset may be a relative offset between DL and UL data transmissions.

In an implementation form of the first aspect, the information indicative of the at least one first resource and the at least one second resource is combined in a DCI format or in a Sidelink Control Information, SCI, format.

As part of the dynamic grant optimization of the PDCCH, combining the DL and UL grant in a single DCI format is employed, in order to support bidirectional communication in a more resource-efficient manner. For a Device-to-Device (D2D) communication scenario, SL forward and reverse communications can also be considered. SL forward and reverse grant may be combined in a single SCI format accordingly.

In an implementation form of the first aspect, if the bidirectional communication is a multi hop communication, the scheduling node is configured to: send the scheduling grant message to at least one of the communicating nodes, in particular to the first communicating node, wherein the scheduling grant message comprises a first grant part for the next hop and a second grant part for the following hops.

The dynamic resource assignments for multi-hop connections may be multicast to the group of UEs, or unicast individually to each UE in the group. As the size of the combined grant depends on the number of UEs in the group, this leads to many different possibilities for the DCI/SCI size/format, which significantly adds to the decoding complexity. To alleviate this problem, the multi-hop combined grant can be split into two parts - a first grant part, which is a fixed- size grant for the next hop, and a second grant part, which is a variable-size grant for the following hops.

In an implementation form of the first aspect, the first grant part comprises a single-hop grant and additional parameters indicating the length, time -frequency location and/or transmission parameters of the second grant part.

Particularly, the fixed- size grant may contain an original unmodified single-hop grant and (optional) additional parameter(s) indicating the length, time -frequency location and/or transmission parameters of the variable- size grant. The first-hop UE receiver decodes the fixed- size grant and decodes its own data. Furthermore, it may extract a second-hop grant (of fixed-size) from the variable-size grant information indicated in the original fixed-size grant and schedule the second-hop transmission according to the information in the second- hop grant.

A second aspect of the present invention provides a communicating node for performing a bidirectional communication, the communicating node being configured to: receive a scheduling grant message including information indicative of at least one first resource and at least one second resource from a scheduling node, wherein the at least one first resource is for a first communication direction and the at least one second resource is for a second communication direction of the bidirectional communication.

A communicating node in bidirectional communication may be a UE, or an integrated access and backhaul (IAB) node. The communicating node receives a combined grant for communications in both directions (e.g., DL and UL) in a single message. In an implementation form of the second aspect, the communicating node is further configured to send a scheduling request to the scheduling node, wherein the scheduling request includes information about the bidirectional communication.

The scheduling request may be an RRC connection request. Information regarding an establish cause and/or a cycle time may be included in the scheduling request.

In an implementation form of the second aspect, the communicating node is further configured to receive the scheduling grant message comprising a first grant part for the next hop and a second grant part for the following hops of a multi-hop communication, and transmit the second grant part to the next communicating node.

The first grant part may be a fixed- size grant containing the original unmodified single-hop grant and (optional) additional parameter(s) indicating the length, time -frequency location and/or transmission parameters of the second grant part. The communicating node (a first- hop UE) may receive the fixed- size grant and decode its own data. Furthermore, the communicating node may extract the second-hop grant (of fixed-size) from the variable- size grant information indicated in the original fixed- size grant and schedule the second- hop transmission according to the information in the second-hop grant.

In an implementation form of the second aspect, the communicating node is configured to obtain from the second grant part a scheduling grant for the next communicating node and a third grant part for the following hops; and transmit the obtained scheduling grant and the third grant part to the next communicating node.

The communicating node may create a new variable-size grant for the following hops from the second grant part. It may further add optional parameters like length, time-frequency location and/or transmission parameters corresponding to the variable-size grant into the new variable-size grant. This process may continue until the last hop in the group combined grant. The variable-size grant may be mapped to the data region of the original grant or a second control region. A third aspect of the present invention provides a method for scheduling a bidirectional communication between at least two communicating nodes, the method comprising: assigning at least one first resource for a first communication direction and at least one second resource for a second communication direction of the bidirectional communication, and sending a scheduling grant message including information indicative of the at least one first resource and second resource to at least one of the communicating nodes.

The method of the third aspect and its implementation forms provide the same advantages and effects as described above for the wireless transmitting device of the first aspect and its respective implementation forms.

A fourth aspect of the present invention provides a method for performing a bidirectional communication, the method comprising: receiving a scheduling grant message including information indicative of at least one first resource and second resource from a scheduling node, wherein the first resource is assigned for a first communication direction and the second resource is assigned for a second communication direction of the bidirectional communication.

The method of the fourth aspect and its implementation forms provide the same advantages and effects as described above for the wireless receiving device of the second aspect and its respective implementation forms.

A further aspect of the invention also relates to a computer program, characterized in program code, which when run by at least one processor causes said at least one processor to execute any method according to embodiments and aspects of the invention. According to still a further aspect, the invention also relates to a computer program product comprising a computer readable medium and said mentioned computer program, wherein said computer program is included in the computer readable medium, and the computer medium comprises of one or more from the group: ROM (Read-Only Memory), PROM (Programmable ROM), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically EPROM) and hard disk drive.

It has to be noted that all devices, elements, units and means described in the present application could be implemented in the software or hardware elements or any kind of combination thereof. All steps which are performed by the various entities described in the present application as well as the functionalities described to be performed by the various entities are intended to mean that the respective entity is adapted to or configured to perform the respective steps and functionalities. Even if, in the following description of specific embodiments, a specific functionality or step to be performed by external entities is not reflected in the description of a specific detailed element of that entity which performs that specific step or functionality, it should be clear for a skilled person that these methods and functionalities can be implemented in respective software or hardware elements, or any kind of combination thereof.

BRIEF DESCRIPTION OF DRAWINGS

The above described aspects and implementation forms of the present invention will be explained in the following description of specific embodiments in relation to the enclosed drawings, in which

FIG. 1 shows an example of mini- slot scheduling as a way to increase PDCCH scheduling capacity. FIG. 2 shows a scheduling node according to an embodiment of the invention.

FIG. 3 shows a single-hop bidirectional DL/UL grant according to an embodiment of the present invention. FIG. 4 shows a multi-hop resource configuration considering ring topology according to an embodiment of the present invention.

FIG. 5 shows a process of piggybacking of combined multi-hop grants according to an embodiment of the present invention.

FIG. 6 shows a combined dynamic grant for bidirectional single-hop communication according to an embodiment of the present invention. FIG. 7 shows an example illustrating arrivals of bidirectional cyclic traffic according to an embodiment of the present invention.

FIG. 8 shows a combined DL and UL time/frequency resource allocation according to an embodiment of the present invention.

FIG. 9 shows a configured grant considering ring topology according to an embodiment of the present invention.

FIG. 10 shows a ring topology with DL, UL and SL connections according to an embodiment of the present invention.

FIG. 11 shows a SPS configuration for ring topology according to an embodiment of the present invention.

FIG. 12 shows an example showing enhancements needed for activation message for combined unicast/multicast cases according to an embodiment of the present invention.

FIG. 13 shows an example of SPS release validation with LI DCI signaling according to an embodiment of the present invention.

FIG. 14 shows a signaling enhancement for combined bidirectional configured grant according to an embodiment of the present invention

FIG. 15 shows a receiving node according to an embodiment of the invention.

FIG. 16 shows a flowchart of a method for scheduling a bidirectional communication between at least two communicating nodes according to an embodiment of the present invention.

FIG. 17 shows a flowchart of a method for receiving a scheduling grant message for a bidirectional communication between at least two communicating nodes according to an embodiment of the present invention. DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 2 shows a scheduling node 200 according to an embodiment of the invention. The scheduling node 200 is configured to schedule a bidirectional communication between at least two communicating nodes. The scheduling node 200 is configured to assign at least one first resource 201 for a first communication direction and at least one second resource 202 for a second communication direction of the bidirectional communication. Particularly, the first communication direction may be a DL transmission and/or a SL forward transmission. The second communication direction may be an UL transmission and/or a SL reverse transmission. The scheduling node 200 is further configured to send a scheduling grant message 203 including information indicative of the at least one first resource 201 and the at least one second resource 202 to at least one of the communicating nodes 210.

The scheduling node 200 can be a Radio Access Network (RAN) node, or a system comprising a RAN node. For example, a RAN node can be a base station (e.g., gNB), a user equipment (UE) and/or an integrated access and backhaul (IAB) node. The new control signaling format according to an embodiment of the invention combines resource assignments for one or more links, nodes or directions of communication, in a single control message. Optionally, the scheduling node 200 may be one of the communicating nodes. The scheduling grant message 203 includes information indicative of the at least one first resource 201 and the at least one second resource 202. In particular, time and/or frequency allocation for the first communication direction may be included in the scheduling grant message 203. Further, a relative time and/or frequency offset for the second communication direction, the offset being relative to the time and/or frequency allocation for the first communication direction, may also be included in the scheduling grant message 203.

As shown in FIG. 3, a single scheduling grant message 203 schedules bidirectional communication between any two RAN nodes, e.g., a scheduling node 200 and a communicating node 210, which could be gNB to UE, or UE to UE, or IAB to IAB/UE. This allows, for instance, a“Master” and a“Slave” to communicate in a closed loop with low delay and with high control resource efficiency. The scheduling node 200 (“Master” in FIG. 3) may assign a DL resource and an UL resource. Then a scheduling grant message 203 carrying information on assigned resources for both DL and UL transmission may be sent to the communicating node 210 (“Slave 1” in FIG. 3).

The combined scheduling grant 203 may be specified as a Dynamic Grant, which means it applies only for a single instance of bidirectional communication or for a single communication cycle. This is achieved by combining both DL and UL (or SL forward and SL reverse links) in a single DCI (or SCI) format.

Alternatively, the combined scheduling grant 203 may be specified as a Configured Grant by enhancing the SPS procedure for bidirectional periodic traffic: essentially by combining the SPS configuration for DL and UL directions (or SL forward and reverse directions).

Combining the bidirectional resource grant in a single control message 203 results in a more optimal use of control channel resources, thus alleviating the PDCCH blocking problem. Instead of two separate (dynamic or configured) grants for the bidirectional communication, a combined bidirectional grant uses less control channel resources.

Further, the bidirectional communication may be a single-hop communication or a multi hop communication. In other words, the combined scheduling grant for the bidirectional traffic also applies to a group of UEs (communicating nodes 210) with multi- hop connections for various topologies like ring, mesh, star, etc. A ring topology is exemplarily shown in FIG. 4.

The dynamic resource assignments for multi-hop connections for a group of UEs, i.e., the communicating nodes 210, containing both cellular links (Uu interface) and direct D2D links (PC5 interface), can be multicast to the group or unicast individually to each communicating node 210 in the group.

The at least one first resource 201 may be for a DL transmission and/or for a SL forward transmission in the bidirectional communication. The at least one second resource 202 may be for an UL transmission and/or for a SL reverse transmission in the bidirectional communication.

The Configured Grant enhancement for multi-hop contains combined resource configuration (using Radio Resource Control, RRC) and activation/deactivation messages (using DCI/SCI) for all hops. The grant may be multicast to the group and may be applicable for both Uu, D2D and/or a combination of both link types. This is an enhancement to the SPS procedure for multi-hop/group communication.

As the size of the combined grant depends on the number of UEs (communicating nodes 210) in the group, this leads to many different possibilities for the DCI/SCI size/format, which significantly adds to the decoding complexity. To alleviate this problem, the multi hop combined grant can be split into two parts - a fixed- size grant for the next hop, and a variable-size grant for the following hops.

Accordingly, in a multi-hop communication, the scheduling node 200 may be configured to send the scheduling grant message 203 to at least one of the communicating nodes 210, in particular to the first communicating node 210, wherein the scheduling grant message 203 comprises a first grant part for the next hop and a second grant part for the following hops.

Optionally, the first grant part comprises a single-hop grant and additional parameters indicating the length, time- frequency location and/or transmission parameters of the second grant part. That means, the fixed-size grant may contain the original unmodified single hop grant and (optional) additional parameter(s) indicating the length, time-frequency location and/or transmission parameters of the variable-size grant. The first-hop UE receiver (the first communicating node 210) decodes the fixed-size grant and decodes its own data. Furthermore, it extracts the second-hop grant (of fixed-size) from the variable- size grant information indicated in the original fixed- size grant and schedules the second- hop transmission according to the information in the second-hop grant. Additionally, it creates a new variable-size grant for the following hops and adds the optional parameters like length, time- frequency location and/or transmission parameters corresponding to the variable-size grant. This process may continue until the last hop in the group combined grant. The variable-size grant may be mapped to the data region of the original grant or a second control region. FIG. 5 illustrates this process of piggybacking of combined multi- hop grants, where the piggybacked grant is mapped to the data region of the fixed- size grant.

The combined multi-hop grant described above applies to any combination of downlink/sidelink/uplink and for both dynamic and configured grants. In case of configured grants, the resource configuration is sent once via higher layer signaling or can be piggybacked as shown in FIG. 5. The activation/deactivation of the grant can be pre configured or sent as a dynamic control message.

The combined multi-hop grant consumes fewer control channel resources compared to N unicast grants, where N is the number of nodes in the multicast group. This is due to the piggybacking feature, where a single fixed- size grant containing piggybacked multi- hop grants for the entire topology is sent on the PDCCH and the grants for the following hops are sent on the uncongested sidelink control channel. This reduces PDCCH congestion and alleviates blocking by mapping the (large) variable -sized grant outside the scarce control channel resources.

Another advantage is that, by scheduling group communication with almost the same control channel overhead (equal to the initial fixed-size grant), more URLLC links can be scheduled simultaneously. Thus, the URLLC scheduling capacity of the 5G system is increased.

As part of the dynamic grant optimization of the PDCCH, it is proposed to combine the DL and UL grant in a single DCI format according to an embodiment of the invention as shown in FIG. 6, thus supporting bidirectional communication in a more resource-efficient manner. In other words, the information indicative of the at least one first resource 201 and the at least one second resource 202 may be combined in a DCI format.

The transmission parameters according to embodiments of the invention are specified considering both DL and UL traffic arrival times, as depicted in FIG. 7. Optionally, the transmission parameters may comprise one or more of a DL/UL/SL MCS, a CSI request indicator, an indication of a data or payload size to be transmitted and/or its characteristics, information about a data or payload processing time or an update to an earlier reported processing time. The Compact DCI format for URLLC under discussion for DL and UL in Release 16, which contains 48 bits, is not optimized to support bidirectional traffic. The unified DCI format proposed here for both DL and UL has a total payload size of 57 bits. The reduction in DCI payload compared to a separate DL and UL Compact DCI is: 48*2 - 57 = 39 bits (~ 40%). UL MCS and UL Frequency domain allocation can be specified implicitly or as a relative offset to their DL counterparts, further reducing the size of the proposed combined DCI.

The idea of the combined DCI can also be extended for a D2D scenario considering SL forward and SL reverse data communication where a transmitting UE on the sidelink provides the respective transmission parameters for both the SL forward link and the SL reverse link. In this scenario, the information indicative of the at least one first resource 201 (for SL forward link) and the at least one second resource 202 (for SL reverse link) may be combined in an SCI format.

According to an embodiment of the invention, the Configured Grant Type 2 procedure, which provides semi-persistent allocation to UEs, i.e., communicating nodes 210, requires the following enhancement for bidirectional traffic, which requires a unified SPS scheduling grant considering both DL and UL traffic arrivals, as shown in FIG. 7.

In the Configured Grant case (SPS), the addition of a symbol offset t₀//_set (and/or a slot offset) between DL and UL data transmission is proposed as part of the Configured Grant as depicted in FIG. 8. Specifically, after a combined DL/UL Configured Grant is configured, the UL grant recurs for each symbol t within the SFN (System Frame Number) cycle (consisting of 1024 radio frames) that satisfies

t = ( tf_art + N x periodicity ) mod n_sym

for all N > 0, where

t UL _fDL , _†

^Lstart ^Lstart ' ^Loffset

t start ⁼ SFN start ^x numberOfSlotsPerFrame x numberOfSymbolsPerSlot

+ slot_start x numberOfSymbolsPerSlot + symbol_start

n_Sym = 1024 x numberOfSlotsPerFrame x numberOfSymbolsPerSlot and SFN_start, slot_start and symbol_start are the SFN, slot, and symbol, respectively, of the first DL transmission where the combined DL/UL Configured Grant was (re-)initialized. According to an embodiment of the invention, periodic messages sent on the chain gNB®UEl®UE2®UE3®UE4®gNB are shown in FIG. 9. Particularly, the gNB is the scheduling node 200, and UEs are the communicating nodes 210. A ring topology and the cycle time according to an embodiment of the invention are illustrated in FIG. 10. The cycle time comprises the time needed for each transmission (DL, SL and UL) as well as for application processing in each slave, as shown in FIG. 10. Hence, the combined SPS procedure contains time/frequency resource allocations for each communicating node 210 on DL, SL and UL, as illustrated in FIG. 9.

The SPS configuration takes into account different transmissions on the Uu (UL/DL) and PC5 (D2D) interfaces. Particularly, after a combined DL/SL/UL Configured Grant is configured, the SL grant for each slave j in the ring (UL grant for the last slave in the ring) recurs for each symbol t within the SFN cycle that satisfies

for all N > 0, where

t _start ⁼ SFN _start ^x numberOfSlotsPerFrame x numberOfSymbolsPerSlot

+ slot_start x numberOfSymbolsPerSlot + symbol_start n_Sym = 1024 x numberOfSlotsPerFrame x numberOfSymbolsPerSlot and SFN_start, slot_start and symbol_start are the SFN, slot, and symbol, respectively, of the first DL transmission where the combined DL/SL/UL Configured Grant was

(re-)initialized. The symbol offset t^_set is explicitly signaled in the SPS configuration (RRC) or included in the DCI that is sent to all slaves. Alternatively, the offset may be fixed or implicitly defined, further reducing the DCI size.

Different MCS may be specified for Uu and PC5 links. Additional information, such as CQI, payload and desired QoS to destination node j may be sent together with the transmissions Txl, Tx2 ... as depicted in FIG. 11. T_proc includes both baseband and application processing delay and is signaled by each node to the network. N1, N2, ... are UEs respectively connected to Slaves 1, 2 ... in the ring.

Further, the activation/deactivation message for the configured grant procedure according to an embodiment of the invention is described. Particularly, the activation/deactivation for SPS is sent via LI DCI signaling. For bidirectional traffic, a single activation/deactivation message via DCI suffices - considering the unicast case where SPS is applicable for both DL/UL and a certain topology where it could be multicast to all communicating nodes 210 scrambled with a group Radio Network Temporary Identifier (RNTI). FIG. 12 and 13 illustrate this for activation and deactivation, respectively.

For the combined multicast configured grant, the scheduling node 200, e.g., the gNB, can decide on the grant configuration based on received information about the cycle time, topology, protocol information, payload sizes and the timing information. The configured grant configuration may then be sent to the entire group via multicast (higher layer/RRC). Activation of the grant can be done via LI DCI signaling, which may use multicast or the piggybacking method described with respect to FIG. 5. The signaling procedure is described in FIG. 14.

In particular, the scheduling node 200 is configured to receive at least one scheduling request from at least one of the communicating nodes 210. The scheduling request includes information about the bidirectional communication. The scheduling node 200 is further configured to obtain a plurality of transmission parameters. Then the scheduling node 200 is also configured to send the scheduling grant message 203 according to the information in the scheduling request and the obtained transmission parameters.

FIG. 15 shows a communicating node 210 according to an embodiment of the invention. The communicating node 210 performs a bidirectional communication. It may be configured to operate inversely to the scheduling node 200 of FIG. 2. In particular, the communicating node 210 is configured to receive a scheduling grant message 203 including information indicative of at least one first resource 201 and at least one second resource 202 from the scheduling node 200. Particularly, the at least one first resource 201 is for a first communication direction and the at least one second resource 202 is for a second communication direction of the bidirectional communication.

The communicating node 210 in bidirectional communication may be a UE, or an IAB node. The communicating node 210 may be a node in a single-hop communication, or one of the nodes in a multi- hop communication. Optionally, the communicating node 210 may receive a combined grant in a multicast message, or in a unicast message. As discussed in the previous embodiments, the combined grant includes resource configurations for both communication directions (e.g., DL and UL, and/or SL forward and reverse).

Optionally, the communicating node 210 may be further configured to send a scheduling request to the scheduling node 200, wherein the scheduling request includes information about the bidirectional communication. In particular, the scheduling request may be an RRC connection request. Information regarding an establish cause, a cycle time, etc. may be included in the scheduling request.

Further, the communicating node 210 may be configured to receive the scheduling grant message 203 comprising a first grant part for the next hop and a second grant part for the following hops of a multi- hop communication. Then the communicating node 210 may be further configured to transmit the second grant part to the next communicating node 210.

In a multi- hop communication scenario, the communicating node 210 may receive the scheduling grant message 203 from a previous hop. The first grant part may be a fixed-size grant containing the original unmodified single-hop grant and (optional) additional parameter(s) indicating the length, time -frequency location and/or transmission parameters of the second grant part. The communicating node 210 may receive the fixed- size grant and decode its own data. Furthermore, the communicating node 210 may extract the second-hop grant (of fixed-size) from the variable-size grant information indicated in the original fixed-size grant and schedule the second-hop transmission according to the information in the second-hop grant.

The communicating node 210 may be further configured to obtain from the second grant part a scheduling grant for the next communicating node and a third grant part for the following hops. The communicating node may create a new variable-size grant for the following hops from the second grant part. It may further add optional parameters like length, time- frequency location and/or transmission parameters corresponding to the variable- size grant into the new variable- size grant.

The communicating node 210 may be further configured to transmit the obtained scheduling grant and the third grant part to the next communicating node. This process continues until the last hop in the group combined grant. The variable-size grant may be mapped to the data region of the original grant or a second control region.

FIG. 16 shows a method 1600 for scheduling a bidirectional communication between at least two communicating nodes according to an embodiment of the present invention. In particular, the method 1600 is performed by a scheduling node, e.g., the scheduling node 200 of FIG. 2. The method 1600 comprises: a step 1601 of assigning at least one first resource 201 for a first communication direction and at least one second resource 202 for a second communication direction of the bidirectional communication; and a step 1602 of sending a scheduling grant message 203 including information indicative of the at least one first resource 201 and second resource 202 to at least one of the communicating nodes.

FIG. 17 shows a method 1700 for receiving a scheduling grant message for a bidirectional communication between at least two communicating nodes according to an embodiment of the present invention. In particular, the method 1700 is performed by a communicating node, e.g., the communication node 210 of FIG. 2 or FIG. 15. The method 1700 comprises: a step 1701 of receiving a scheduling grant message 203 including information indicative of the at least one first resource 201 and second resource 202 from the scheduling node 200, wherein the first resource 201 is assigned for a first communication direction and the second resource 202 is assigned for a second communication direction of the bidirectional communication.

The present invention has been described in conjunction with various embodiments as examples as well as implementations. However, other variations can be understood and effected by those persons skilled in the art and practicing the claimed invention, from the studies of the drawings, this disclosure and the independent claims. In the claims as well as in the description the word“comprising” does not exclude other elements or steps and the indefinite article“a” or“an” does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in the mutual different dependent claims does not indicate that a combination of these measures cannot be used in an advantageous implementation. List of Abbreviations

Claims

1. Scheduling node (200) for scheduling a bidirectional communication between at least two communicating nodes (210), the scheduling node (200) being configured to: assign at least one first resource (201) for a first communication direction and at least one second resource (202) for a second communication direction of the bidirectional communication; and

send a scheduling grant message (203) including information indicative of the at least one first resource (201) and the at least one second resource (202) to at least one of the communicating nodes (210).

2. Scheduling node (200) according to claim 1, wherein:

the scheduling node (200) is one of the communicating nodes (210).

3. Scheduling node (200) according to claim 1 or 2, wherein:

the information indicative of the at least one first resource (201) and the at least one second resource (202) comprises one or more of:

time and/or frequency allocation for the first communication direction a relative time and/or frequency offset for the second communication direction, the offset being relative to the time and/or frequency allocation for the first communication direction.

4. Scheduling node (200) according to one of the claims 1 to 3, further configured to:

receive at least one scheduling request from at least one of the communicating nodes (210), wherein the scheduling request includes information about the bidirectional communication;

obtain a plurality of transmission parameters; and

send the scheduling grant message (203) according to the information in the scheduling request and the obtained transmission parameters.

5. Scheduling node (200) according to claim 4, wherein:

the transmission parameters comprise one or more of:

a Downlink, DL, modulation and coding scheme, MCS, - an Uplink, UL, MCS,

- a Sidelink, SL, MCS,

a Channel State Information, CSI, request indicator,

an indication of a data or payload size to be transmitted and/or its characteristics,

information about a data or payload processing time or an update to an earlier reported processing time.

6. Scheduling node (200) according to one of the claims 1 to 5, wherein:

the bidirectional communication is a single-hop communication or a multi-hop communication.

7. Scheduling node (200) according to one of the claims 1 to 6, wherein:

the scheduling grant message (203) is valid for a single instance communication or for a single communication cycle.

8. Scheduling node (200) according to one of the claims 1 to 7, wherein:

the at least one first resource (201) is for a DL transmission or for a SL forward transmission in the bidirectional communication, and/or

the at least one second resource (202) is for an UL transmission or for a SL reverse transmission in the bidirectional communication.

9. Scheduling node (200) according to one of the claims 1 to 8, wherein:

the scheduling grant message (203) further comprises information about a symbol offset for the second communication direction, the offset being relative to the time allocation for the first communication direction.

10. Scheduling node (200) according to one of the claims 1 to 9, wherein:

the information indicative of the at least one first resource (201) and the at least one second resource (202) is combined in a Downlink Control Information, DCI, format or in a Sidelink Control Information, SCI, format.

11. Scheduling node (200) according to one of claims 6 to 10, wherein, if the bidirectional communication is a multi-hop communication, the scheduling node is configured to:

send the scheduling grant message (203) to at least one of the communicating nodes, in particular to the first communicating node (210),

wherein the scheduling grant message (203) comprises a first grant part for the next hop and a second grant part for the following hops.

12. Scheduling node (200) according to claim 11, wherein

the first grant part comprises a single-hop grant and additional parameters indicating the length, time- frequency location and/or transmission parameters of the second grant part.

13. Communicating node (210) for performing a bidirectional communication, the communicating node (210) being configured to:

receive a scheduling grant message (203) including information indicative of at least one first resource (201) and at least one second resource (202) from a scheduling node (200),

wherein the at least one first resource (201) is for a first communication direction and the at least one second resource (202) is for a second communication direction of the bidirectional communication.

14. Communicating node (210) according to claim 13, further configured to:

send a scheduling request to the scheduling node (200), wherein the scheduling request includes information about the bidirectional communication.

15. Communicating node (210) according to claim 13 or 14, configured to:

receive the scheduling grant message (203) comprising a first grant part for the next hop and a second grant part for the following hops of a multi-hop communication; and

transmit the second grant part to the next communicating node (210).

16. Communicating node (210) according to claim 15, configured to:

obtain from the second grant part a scheduling grant for the next communicating node (210) and a third grant part for the following hops; and

transmit the obtained scheduling grant and the third grant part to the next communicating node (210).

17. Method (1600) for scheduling a bidirectional communication between at least two communicating nodes (200, 210), the method (1600) comprising:

assigning (1601) at least one first resource (201) for a first communication direction and at least one second resource (202) for a second communication direction of the bidirectional communication, and

sending (1602) a scheduling grant message (203) including information indicative of the at least one first resource (201) and second resource (202) to at least one of the communicating nodes (200, 210).

18. Method (1700) for performing a bidirectional communication, the method (1700) comprising:

receiving (1701) a scheduling grant message (203) including information indicative of at least one first resource (201) and second resource (202) from a scheduling node (200),

wherein the first resource (201) is assigned for a first communication direction and the second resource (202) is assigned for a second communication direction of the bidirectional communication.