Improved Retransmission Handling in a Wireless Communication Network

Abstract

The present disclosure relates to nodes (AP2, U in a wireless communication system (1) 11 ), wherein the nodes (AP2, U 11 ) are adapted to communicate with at least two other nodes (AP1, AP0) in the wireless communication system (1), and wherein the other nodes (AP1, AP0) are first type nodes (AP1, AP0) adapted to communicate with each other in a backhaul communication manner. The nodes (AP2, U 11 ) are adapted to receive a signal (xA) transmitted from an adjacent first type node (AP1), wherein the signal (xA) has been forwarded from at least one more distant first type node (AP0). In the case where the decoding of the signal (xA) is unsuccessful, the nodes (AP2, U 11 ) are adapted to request a retransmission (NACK) of the signal (xA), and directly receive a retransmission of the signal (xA) from the more distant first type node (AP0).

Description

Technical Field

[0001] The present disclosure relates to relay in a wireless communication network, and more particularly, to relay in an integrated access and backhaul (IAB) network. Background Art

[0002] The fifth generation wireless network (5G) must provide high-speed data streams for everyone everywhere at all times. To meet such requirements, large bandwidths need to be used. Here, it mainly focuses on potential massive multiple-input multiple-output (MMIMO) links based on millimeter waves as a key enabling technology for obtaining a large enough bandwidth / data rate. Importantly, the presence of very wide bandwidths allows wireless backhaul transmission to be included in the same spectrum as wireless access. In such a setup, there is thus a sharing of radio resources between the access link and the backhaul link, which implies that the access link and the backhaul link compete on the same radio resource pool.

[0003] For this purpose, 3GPP has considered such integrated access and backhaul (IAB) network configurations, where an access point (AP) (which can be fiber-connected, for example) provides wireless backhaul and access connections to other APs and customer premise equipment (CPE) within its cell area, respectively. The backhaul link integrating access can be a single-hop or multi-hop link in an IAB network. In a multi-hop deployment, the IAB network is relayed from one AP along a specific route from AP to AP until it reaches its destination. Thus, the IAB network can have a star configuration with multiple APs wirelessly backhauled to a fiber-connected AP through direct single-hop connections, or a cascade configuration with APs wirelessly connected to the fiber-connected AP in a multi-hop manner.

[0004] It is desirable to densify the network with a large number of access points (APs), where each access point serves multiple CPEs within its corresponding relatively small cell area. Compared with the case of having few macro base stations covering wide areas, in a dense small cell network, less path loss / shadowing and a higher line-of-sight (LOS) connection probability are expected. Therefore, better channel quality is experienced in these short-range links compared with the case of having few macro base stations.

[0005] The advantages of the IAB network are as follows:

[0006] Cost reduction:

[0007] Fiber optic links are relatively expensive in large urban areas, where most of the total is related to excavation and installation. For this reason, as well as traffic congestion and infrastructure relocation, some cities have considered suspending fiber optic excavation, especially in historical areas. In such scenarios, millimeter wave-based wireless backhaul is the best alternative to provide almost the same rate as fiber optic, and is significantly lower in price and does not require excavation.

[0008] Link quality enhancement:

[0009] Compared with the direct macro base station (BS)-CPE link, for the AP-CPE connection of wireless backhaul in a small cell, less path loss / shadow and a higher line-of-sight (LOS) connection probability are expected. Therefore, better channel quality is experienced in such small cells compared to the case with a direct macro BS-CPE connection.

[0010] Long-term network planning:

[0011] In a small cell backhaul and fixed wireless access (FWA) network with fixed AP / CPE, the IAB system is of most interest. This enables predicting the channel quality and performing accurate network planning for multiple packet transmissions.

[0012] In a multi-hop IAB network, the backhaul link is the bottleneck of the transmission setup. As an example, the IAB node directly connected to the fiber-connected IAB donor node is the most loaded node in the network that needs to send / receive messages for its associated CPE and all other IAB nodes. This results in high end-to-end and scheduling delays for the last few hops of the network. In the case of message transmission failure in the heavily loaded node, the problem becomes prominent because the spectrum is used for retransmissions, such as multiple hybrid automatic repeat request (HARQ)-based retransmissions. This is especially because the IAB network is mainly designed for, e.g., fixed wireless access (FWA) networks, where fixed nodes suffer from low network diversity and require multiple retransmissions in the case of message transmission failure.

[0013] For these reasons and to support a large number of hops and / or per-hop CPE, it is desirable to have an intelligent data transmission scheme to not only reduce the load of highly loaded IAB nodes, but also avoid underutilization of the spectrum of other nodes and increase network diversity. Summary of the Invention

[0014] The object of the present disclosure is to provide a node in a wireless communication system that communicates with at least one other node, where it is desired to reduce the load of highly loaded nodes and avoid underutilization of the spectrum of other nodes.

[0015] This object is achieved by a node in a wireless communication system, where the node is adapted to communicate with at least two other nodes in the wireless communication system, and the other nodes are first-type nodes adapted to communicate with each other in a backhaul communication manner. The node is also adapted to receive a signal sent from an adjacent first-type node, where the signal has been forwarded from at least one more distant first-type node. In the case of unsuccessful decoding of the signal, the node is adapted to request retransmission of the signal (NACK) and directly receive the retransmission of the signal from the more distant first-type node.

[0016] In this way, the load and buffer requirements of adjacent first-type nodes are reduced, and thus the scheduling delay is also reduced, because part of the data is transferred without using adjacent first-type nodes. In terms of this, retransmission is performed without any system cost in terms of spectrum and scheduling delay, where network diversity is increased, thus reducing the possibility of requiring multiple retransmission rounds.

[0017] According to some aspects, the node is adapted to send a retransmission request for a signal directly to a farther first-type node.

[0018] In this way, after the initial transmission to the node, adjacent first-type nodes do not participate in processing the signal.

[0019] According to some aspects, the node is a first-type node that is adapted to communicate with adjacent first-type nodes via a corresponding backhaul channel and communicate with the farther first-type node via a direct backhaul channel.

[0020] This means that the present disclosure can be applied to backhaul communication between access points. Using the direct backhaul channel relieves all the burdens from adjacent first-type nodes after the initial transmission to the node.

[0021] According to some aspects, the farther first-type node is a first-type node connected to the core network in a fiber-optic connection manner.

[0022] According to some aspects, the node is a second-type node that is adapted to communicate with adjacent first-type nodes via a corresponding access channel and communicate with the farther first-type node via a direct access channel.

[0023] This means that a second-type node (such as a CPE) can initially communicate with an adjacent first-type node (such as an access point) and directly receive possible retransmissions from the farther first-type node. Using the direct access channel between the second-type node and the farther first-type node relieves all the burdens from adjacent first-type nodes after the initial transmission to the node.

[0024] According to some aspects, the communication between first-type nodes is backhaul communication via at least one corresponding backhaul channel, and wherein at least one first-type node is adapted to communicate with a corresponding group of second-type nodes via a corresponding access channel. Each group of second-type nodes includes at least one second-type node, and both the backhaul communication and the access communication are performed by a common device at each type of first-type node.

[0025] This means that the present disclosure can be applied to backhaul communication between an access point and a CPE in an IAB network.

[0026] In some aspects, retransmission of signals is issued during a temporarily inactive period in which the node and more distant nodes do not participate in any communication with other nodes.

[0027] This results in lower end-to-end transmission latency, reduced buffer requirements, and higher throughput for the second type of nodes served by the node.

[0028] In some aspects, a retransmission request (NACK) for a signal is based on Hybrid Automatic Repeat reQuest (HARQ).

[0029] This object is also achieved by a first type of node in a wireless communication system, where the first type of node is adapted to communicate with at least two other nodes in the wireless communication system. At least one of the other nodes is a first type of node adapted to communicate with other first type of nodes via a backhaul communication means. The node is also adapted to receive a signal transmitted from an adjacent first type of node and forward the signal to a receiving node. The first type of node is adapted to delete the forwarded signal from its buffer after having forwarded the signal, regardless of whether the receiving node is able to decode the signal.

[0030] In this way, the load and buffer requirements of the first type of node are reduced, and thus the scheduling delay is also reduced, because part of the data is transferred without involving the first type of node. Retransmission is performed without any system cost in terms of spectrum and scheduling delay, where network diversity is also increased, and thus the possibility of requiring multiple retransmission rounds is reduced.

[0031] In some aspects, adjacent first type of nodes are connected to the core network in a fiber-optic connection manner.

[0032] This object is also achieved by a method and a communication system associated with the above advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present disclosure will now be described in more detail with reference to the accompanying drawings, in which:

[0034] Figure 1 A view of a wireless communication system according to a first example at a first time is schematically shown;

[0035] Figure 2 A view of a wireless communication system according to a first example at a second time is schematically shown;

[0036] Figure 3 A view of a wireless communication system according to a first example in a subsequent time slot is schematically shown;

[0037] Figure 4 Schematically shows Figure 3 a timing diagram of the wireless communication system in

[0038] Figure 5 Schematically shows a view of a wireless communication system according to a first example at a first time;

[0039] Figure 6 Schematically shows a view of a wireless communication system according to a first example at a second time;

[0040] Figure 7 Shows a flowchart of a method according to an embodiment;

[0041] Figure 8 Shows a flowchart of a method according to an embodiment;

[0042] Figure 9A Schematically shows a first type of node;

[0043] Figure 9B Schematically shows a first type of node; and

[0044] Figure 10 Schematically shows a graphical representation of the cumulative SNR. Detailed Description

[0045] Aspects of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings. However, the different devices, systems, computer programs, and methods disclosed herein may be implemented in many different forms and should not be construed as limited to the aspects set forth herein. Like reference numerals throughout the drawings refer to like elements.

[0046] The terms used herein are for the purpose of describing aspects of the present disclosure only and are not intended to limit the present invention. As used herein, the singular forms "a", "an", and "the" are also intended to include the plural forms unless the context clearly indicates otherwise.

[0047] Network densification makes use of wireless backhaul; due to the relatively high cost of fiber optic link installation as well as traffic congestion and infrastructure relocation, high-speed LOS wireless backhaul links are required to support relatively small application points (APs), which has motivated the so-called integrated access and backhaul (IAB) networks.

[0048] Reference Figure 1, the wireless communication system 1 includes an IAB network 7 with four hops. In the wireless communication system 1, there are first type nodes AP0, AP1, AP2, AP3, here in the form of a first access point AP0, a second access point AP1, a third access point AP2, and a fourth access point AP3. The access points AP0, AP1, AP2, AP3 are arranged to communicate with each other in the wireless communication system 1 via corresponding first backhaul channels H1, second backhaul channels H2, and third backhaul channels H3 having specific channel qualities, typically by means of at least one type of signal relay that employs decoding and encoding according to some aspects. According to some aspects, the signal relay consists of a decode - encode - forward (DF) relay of the signal.

[0049] Each access point AP0, AP1, AP2, AP3 is adapted to communicate with a corresponding group of second type nodes U 01 , h 02 ; h 11 , h 12 ; h 21 , h 22 ; h 31 , h 32 via corresponding access channels h 01 , U 02 ; U 11 , U 12 ; U 21 , U 22 ; U 31 , U 32 for access communication. The second type nodes U 01 , U 02 ; U 11 , U 12 ; U 21 , U 22 ; U 31 , U 32 are here in the form of customer premise equipment (CPE), and typically, each group of CPE U 01 , U 02 ; U 11 , U 12 ; U 21 , U 22 ; U 31 , U 32 includes at least one CPE. The number of CPEs for each access point AP0, AP1, AP2, AP3 in Figure 1 is only an example; there can be any number of CPEs for each access point AP0, AP1, AP2, AP3. According to some aspects, one or more access points may lack CPEs to be served and only act as relay nodes. Typically, the network has N access points and m CPEs for each access point. In addition, by APi The CPEs of the service are typically labeled as U ij , j = 1, …, m.

[0050] According to some aspects, both the backhaul communication and the access communication are performed by a common device at the access points AP0, AP1, AP2, AP3. The second access point AP1, the third access point AP2, and the fourth access point AP3 are wirelessly backhauled by the first access point AP0, which is connected to the core network 2 using a fiber optic connection 5. The access point AP0 connected to the core network may be referred to as an IAB donor node.

[0051] In an IAB network, the uplink (UL) and downlink (DL) transmissions do not follow the common definitions because both endpoints of the backhaul link are access points. However, for simplicity, the data transmission towards (respectively, from) the first access point AP0 is referred to as UL (respectively, DL) transmission. The present disclosure is applicable to DL transmissions from the first access point AP0 to other nodes.

[0052] Different scheduling protocols can be considered, and in the following example, as Figure 2 shown, the time slot 6 is divided into a receive (Rx) sub - slot RX s and a transmit (Tx) sub - slot TX s for the first access point AP0, and there are both backhaul connections and access connections in each sub - slot. This means that the discussion involves UL transmissions from CPE U 01 、U 02 ;U 11 、U 12 ;U 21 、U 22 ;U 31 、U 32 to the first access point AP0, and DL transmissions from the first access point AP0 to CPE U 01 、U 02 ;U 11 、U 12 ;U 21 、U 22 ;U 31 、U 32 . In addition, the settings for a time - division multiple access (TDMA) setup are also discussed. However, the same scheme can also be applied to other resource allocation methods, such as frequency - division multiple access (FDMA).

[0053] As the number of hops / the number of CPEs per hop increases, the AP needs to transfer the aggregated data of multiple CPEs accumulated from the previous hop. Consequently, the AP-AP backhaul link is overloaded, which can result in high decoding complexity / latency and buffering cost for the AP and large end-to-end transmission latency / low end-to-end throughput for the CPE. This becomes increasingly evident as the AP gets closer to the access point AP0 connected to the core network 2.

[0054] More specifically, in the general case where each access point has m CPEs (which can be applied to this example), for each time slot, the first access point AP0 needs to send 2Nm signals for its m CPEs and the (N - 1)m CPEs of the other access points AP1, AP2, AP3, including m DL and m UL signals on the access and DL / UL backhaul signals. Then, the access point i>0 needs to transfer a total of 2(2Nm - im) signals, including access and backhaul as well as DL and UL. Therefore, the second access point AP1 is the busiest node that is active throughout the time slot, while the other access points AP2, Ap3 may be turned off during some periods and wait for the previous hop to complete their data transmission.

[0055] This is because:

[0056] - Part of the spectrum is underutilized because different access points need to wait until the data transmission of the more loaded access points is completed, and

[0057] - The high load of the second access point AP1 and other highly loaded nodes results in large scheduling delays for all CPEs.

[0058] If the data transmission fails in the link between the second access point AP1 and the third access point AP2 via the second backhaul channel H2, the problem becomes even more significant. This is because the IAB network is mainly designed for, for example, fixed wireless access (FWA) networks, and the network diversity for fixed CPEs in FWA networks is low. Therefore, multiple retransmissions based on HARQ (Hybrid Automatic Repeat reQuest) may be required with a high probability, which leads to even higher scheduling delays and buffer requirements for the second access point AP1.

[0059] In Figure 1 、 Figure 2 、 Figure 3 and Figure 4 a first example is shown. In Figure 1 and Figure 2 , for clarity, only one signal is shown, while in Figure 3 and Figure 4 all the signals during time slot 6 are shown, where Figure 4 shows the Figure 3 corresponding timing diagram.

[0060] In Figure 1 , the first signal x A is sent from the first access point AP0 to the second access point AP1. In Figure 2 , the first signal x A is sent from the second access point AP1 to the third access point AP2. However, the third access point AP2 cannot successfully decode the first signal x A .

[0061] According to the present disclosure, with reference to Figure 3 and Figure 4 , for example, during the receive sub-slot RX s , the third access point AP2 is adapted to directly send a retransmission request NACK of the first signal x A to the first access point AP0 via a direct backhaul channel H4 between the first access point AP0 and the third access point AP2. According to some aspects, the retransmission request NACK of the first signal x A is based on HARQ. The NACK can be sent in different ways, even at completely different frequencies.

[0062] This means that the third access point AP2 does not request a retransmission from the second access point AP1, which will relieve the second access point AP1 that is usually overloaded.

[0063] During a subsequent transmit sub-slot TX s , the first access point AP0 is adapted to directly retransmit the first signal x A to the third access point AP2 via the direct backhaul channel H4, and the third access point AP2 is adapted to directly receive the retransmitted first signal x A from the first access point AP0 via the direct backhaul channel H4.

[0064] In this context, for the third access point AP2, the second access point AP1 is an adjacent first type of node, and the first access point AP0 is a farther first type of node.

[0065] This means that after the first signal x A has been sent to the third access point AP2, the second access point AP1 no longer participates in the further processing of the first signal x A , which reduces the burden on the third access point AP2. According to some aspects, after the first signal x A has been sent, the first signal x A is deleted from the buffer memory of the second access point AP1. However, the first signal x A is retained in the buffer memory of the first access point AP0.

[0066] When the first signal x AWhen successfully decoded by the third access point AP2, depending on the final destination of the first signal x A the first signal x A is forwarded to the CPE U served by the third access point AP2 21 U 22 or is forwarded to the fourth access point AP3.

[0067] According to some aspects, a subsequent retransmission of the first signal x is performed during a time period T1 in which the third access point AP2 and the first access point AP0 do not participate in any communication with other nodes A This will be described below with reference to Figure 3 and Figure 4 and

[0068] In the receive sub - slot RX s the first access point AP0 receives information x2, x4 from the CPE U it serves 01 U 02 and receives information x from the second access point AP1 18 The second access point AP1 sends the information x 20 to the third access point AP2, sends the information x 18 to the first access point AP0, and sends the information x5, x7 to the CPE U it serves 11 U 12 The third access point AP2 receives the information x from the second access point AP1 20 receives the information x from the fourth access point AP3 22 and receives the information x 21 U 22 from the CPE U it serves 10 x 12 The fourth access point AP3 sends the information x 22 to the third access point AP2 and sends the information x 14 x 16 to the CPE U it serves 31 U 32 U

[0069] In the transmit sub - slot TX s the first access point AP0 sends the information x1, x3 to the CPE U it serves 01 U 02 and sends the information x 17 to the second access point AP1. The second access point AP1 receives the information x from the third access point AP2 19 receives the information x from the first access point AP0 17 and receives from the CPE U it serves 11 U12 Receive information x6, x8. The third access point AP2 sends information x to the second access point AP1 19 , and sends information x to the fourth access point AP3 21 , and to the CPE U 21 , U 22 it serves, sending information x9, x 11 . The fourth access point AP3 receives information x from the third access point AP2 21 , and receives information x from the CPE U 31 , U 32 it serves 13 , x 15 .

[0070] In addition, according to the present disclosure, when the first access point AP0 and the third access point AP2 are temporarily inactive, the first access point AP0 can use the first time period T1 in the transmission sub-slot TX s to retransmit the first signal x to the third access point AP2 A . This retransmission occurs via the direct backhaul channel H4 between the first access point AP0 and the third access point AP2

[0071] Therefore, the temporarily inactive time periods T1 of different hops can be used to reduce the network end-to-end transmission delay and buffer requirements

[0072] The present disclosure will now be discussed in more detail for this embodiment

[0073] Through the present disclosure, in order to reduce the buffer requirements of the second access point AP1 and reduce the scheduling delay, the second access point AP1 is only responsible for the initial transmission of the first signal x A to the third access point AP2. Then, immediately after the initial transmission, the second access point AP1 discards the first signal x A , and does not wait for an acknowledgment / non-acknowledgment (ACK / NACK) from the third access point AP2. That is, in terms of HARQ-based retransmission, the second access point AP1 is only responsible for the retransmission to its own CPE, i.e., U 1j , j = 1,..., m, and is not responsible for the signals of the third access point AP2 or the fourth access point AP3

[0074] Having received the initial first signal x from the second access point AP1 A , the third access point AP2 attempts to decode the received first signal x A . If the first signal x A is correctly decoded, the third access point AP2 sends an ACK to the first access point AP0, and then the first access point AP0 discards the associated buffered first signal x AOtherwise, the third access point AP2 sends a NACK to the first access point AP0. Then, HARQ-based retransmission starts, where the first access point AP0 uses a temporarily inactive time period (e.g., the time period T1 in Figure 4 to directly retransmit the signal to the third access point AP2. The retransmission continues until the signal is correctly decoded or the maximum number of retransmissions, duly considered by the network designer, is reached. Note that during the retransmission round, the second access point AP1 is completely bypassed, and the first access point AP0 is directly connected to the third access point AP2.

[0075] When and how the ACK / NACK is sent to the first access point AP0 can be different. In this example, once the second access point AP1 has sent the initial first signal x A , then the signal is removed from the buffer of the second access point AP1, and the second access point AP1 no longer cares whether the third access point AP2 can decode the first signal x A . Then, for possible retransmissions, the third access point AP2 communicates directly with the first access point AP0 via the direct backhaul channel H4, for both retransmissions and ACK / NACK feedback. Preferably, according to some aspects, the signal retransmission from AP0 to AP2 is performed in the temporarily inactive time period T1, as they are typically expensive and relatively long signals. ACK / NACK is typically relatively short and inexpensive, and can be transmitted in the same or different frequency bands.

[0076] When the first signal x A is sent to the third access point AP2 via the second access point AP1, the first access point AP0 buffers the first signal x A . Then, the first access point AP0 waits for the ACK / NACK feedback from the third access point AP2. If the third access point AP2 cannot decode the first signal x A of the initial data transmission from the second access point AP1, the first access point AP0 will handle the retransmission to the third access point AP2 within the temporarily inactive time period. Compared with the data transmission in the AP0-AP1 link, when the first signal x A that fails to be retransmitted directly to the third access point AP2 within the temporarily inactive time period, the first access point AP0 can adapt the transmission power / rate and use a different beamforming scheme. In addition, depending on whether the second access point AP1 or the third access point AP2 is receiving a signal from the first access point AP0, the timing is adapted.

[0077] The AP-AP link is fixed, and the second access point AP1 can determine the appropriate transmission rate / power with high accuracy so that the third access point AP2 can correctly decode the received signal with high probability. Therefore, retransmissions may be rarely needed. Thus, considering the high load of the second access point AP1, for the rare cases where retransmissions are needed, it is almost unnecessary for the second access point AP1 to buffer all signals to the third access point AP2. On the other hand, due to accurate parameter adaptation, if the third access point AP2 cannot decode the received signal, the signals that are successfully decoded are usually almost obtained, and the third access point AP2 only needs a small boost to decode the failed signals. This small boost can be well provided by the first access point AP0 via the direct backhaul channel H4, even if the link via the direct backhaul channel H4 may be weak.

[0078] This is shown in Figure 10 where it is shown that most of the SNR required for successful message decoding by the third access point AP2 is provided by the initial transmission of the first signal x from the second access point AP1. The third access point AP2 cannot decode the first signal x in the first transmission 10 A , because the SNR drops below the threshold γ for successful decoding. The retransmission 11 results in the SNR exceeding the threshold γ for successful decoding. Since the first signal x in the first transmission 10 A is relatively close to the threshold γ for successful decoding, only a relatively small boost in SNR is needed in the retransmission to exceed the threshold γ for successful decoding. A

[0079] In this way, the load and buffer requirements of the second access point AP1 are reduced, and thus the scheduling delay is also reduced because part of the data is transferred without using the second access point AP1.

[0080] Retransmissions such as using HARQ are performed without any system cost in terms of spectrum and scheduling delay, where spectrum utilization is improved by using the temporarily inactive period T1. Performing the initial transmission via the second backhaul channel H2 and the retransmission via the direct backhaul channel H4 increases network diversity and thus reduces the probability of requiring multiple HARQ-based retransmission rounds.

[0081] Furthermore, spectrum utilization is improved by using the temporarily inactive period T1, which results in lower end-to-end transmission delay and higher throughput for the CPE U 21 , U 22 ; U 31 , U 32 served by the third access point AP2 and the fourth access point AP3.

[0082] According to some aspects, the third access point AP2 sends an ACK / NACK to the first access point AP0 via the first access point AP1, via the second backhaul channel H2 and the first backhaul channel H1, rather than via the direct backhaul channel H4, depending on whether the decoding is successful. The retransmitted signal x A is always sent via the direct backhaul channel H4. This is a possible aspect because, compared to normal data messages, the ACK / NACK signal contains relatively little information and contributes relatively little to the load of the AP. This can apply to all examples and other possible signal routings.

[0083] Reference Figure 5 and Figure 6 provide a second example. Here, for clarity, only one signal is shown.

[0084] In Figure 5 two time instances are shown. First, the first signal x A is sent from the first access point AP0 to the second access point AP1 and then from the second access point AP1 to the first CPE U 11 served by the second access point AP1. However, the first CPE U 11 cannot successfully decode the first signal x A .

[0085] According to the present disclosure, with reference to Figure 6 , the first CPE U 11 is adapted to send a retransmission request NACK for the first signal x 11 directly to the first access point AP0 via the direct access channel h 13 . According to some aspects, the retransmission request NACK for the signal x A is based on HARQ. A 11

[0086] This means that the first CPE U 11 does not request a retransmission from the second access point AP1, which will relieve the work of the second access point AP1 that is usually heavily loaded.

[0087] The first access point AP0 is adapted to directly retransmit the first signal x 13 to the first CPE U A via the direct access channel h 11 , and the first CPE U 11 is adapted to directly receive the retransmitted first signal x 13 from the first access point AP0 via the direct access channel h A .

[0088] In this context, for the first CPE U11 The second access point AP1 is an adjacent node of the first type, and the first access point AP0 is a farther node of the first type.

[0089] Therefore, the present disclosure can be implemented for both backhaul communication and access communication.

[0090] With the present disclosure, scheduling and end-to-end data transmission latency are reduced, network diversity is increased, buffer requirements of AP nodes are reduced, and different AP nodes in the network will have balanced loads, which results in a better balance of loads in different AP nodes. In particular, the load / buffer requirements of the most loaded AP node (the second application point AP1 in the above example) are reduced, and the spectrum utilization of low-loaded nodes and network diversity are increased so as to avoid underutilization of the spectrum of low-loaded nodes.

[0091] In the case of data transmission failure in a reloaded link, the temporarily inactive period of an AP node with low spectrum utilization is used for HARQ-based retransmission, which increases network diversity and reduces the probability of requiring multiple HARQ-based retransmissions. As a further result, the reloaded nodes are not responsible for HARQ-based retransmissions and can discard messages from their buffers after the first transmission. In addition, depending on the data transmission method in different time slots, the timing, beamforming, and buffering methods of IAB nodes are updated. In this way, this results in improved end-to-end throughput of CPEs, better energy efficiency, and reduced buffer requirements of AP nodes.

[0092] Therefore, the number of hops and / or the number of CPEs per hop can be increased.

[0093] Referring to Figure 7 the present disclosure also relates to a method in nodes AP2, U in the wireless communication system 1 11 wherein the method includes communicating S1 with at least two other nodes AP1, AP0 in the wireless communication system 1, wherein the other nodes AP1, AP0 are of the first type and constitute the first type of nodes AP1, AP0 that use backhaul communication when communicating with each other. The method further includes: receiving S2 a signal x sent from an adjacent first type node AP1 A wherein the signal x A has been forwarded from at least one farther first type node AP0. In the case where the decoding S3 of the signal x A is unsuccessful, the method includes requesting S4 a retransmission NACK of the signal x A and directly receiving S5 a retransmission of the signal x from the farther first type node AP0 A .

[0094] According to some aspects, the method includes directly sending the S41 signal x to a farther first type node AP0 A a retransmission request NACK of

[0095] According to some aspects, the node is a first type node AP2, which is used to communicate with an adjacent first type node AP1 through a corresponding backhaul channel H1, and is used to communicate with the farther first type node AP0 via a direct backhaul channel H4.

[0096] According to some aspects, the farther first type node is a first type node AP0 connected to the core network 2 in the manner of an optical fiber connection 5.

[0097] According to some aspects, the node is a second type node U 11 , which is used to communicate with an adjacent first type node AP1 through a corresponding access channel h 11 and is used to communicate with the farther first type node AP0 via a direct access channel h 13

[0098] According to some aspects, the communication between the first type nodes AP0, AP1, AP2, AP3 is backhaul communication via at least one corresponding backhaul channel H1, H2, H3, H4, and wherein at least one of the first type nodes AP0, AP1, AP2, AP3 is used to communicate with a corresponding group of second type nodes U 11 h 12 ; h 21 h 22 ; h 31 h 32 via the corresponding access channels h 11 U 12 ; U 21 U 22 ; U 31 U 32 . Each group of second type nodes U 11 U 12 ; U 21 U 22 ; U 31 U 32 includes at least one second type node U 11 U 12 ; U 21 U 22 ; U 31 U 32 , wherein both the backhaul communication and the access communication are performed by a common device at each of the first type nodes AP0, AP1, AP2, AP3.

[0099] ​According to some aspects, the method includes: retransmitting signal x during a temporarily inactive time period T1 in which node AP2 and more distant node AP0 are not used for communication with other nodes A .

[0100] According to some aspects, the retransmission request NACK for signal x A is based on Hybrid Automatic Repeat reQuest (HARQ).

[0101] Referring Figure 8 to, the present disclosure also relates to a method in a first type of node AP1 in a wireless communication system 1, wherein the method includes: communicating T1 with at least two other nodes AP2, U 11 , AP0 in the wireless communication system 1, wherein at least one of the other nodes AP2, AP0 is a first type of node that uses backhaul communication when communicating with other first type of nodes; and receiving T2 signal x sent from an adjacent first type of node AP0 A . The method further includes: forwarding T3 signal x to receiving nodes AP2, U A , and deleting T4 the forwarded signal x from its buffer after having forwarded signal x 11 , regardless of whether the receiving nodes AP2, U A are able to decode signal x A . 11 A .

[0102] According to some aspects, the adjacent first type of node AP0 is connected to the core network 2 in a fiber optic connection 5 manner.

[0103] As Figure 9A shown, according to some aspects, nodes AP2, U 11 in the wireless communication system 1 include a processor unit 3, which is adapted to control communication with at least two other first type of nodes AP1, AP0 in the wireless communication system 1. The processor unit 3 is further adapted to control receiving signal x sent from an adjacent first type of node AP1 A , wherein signal x A has been forwarded from at least one more distant first type of node AP0. In the case where the decoding of signal x A is unsuccessful, the processor unit 3 is further adapted to request a retransmission (NACK) of signal x A ; and control the retransmission of directly receiving signal x A from the more distant first type of node AP0.

[0104] According to some aspects, the processor unit 3 is adapted to control directly sending a retransmission request (NACK) for signal x A to the more distant first type of node AP0.​

[0105] According to some aspects, the node is a first type of node AP2, which is adapted to communicate with an adjacent first type of node AP1 via a corresponding backhaul channel H1, and is adapted to communicate with the farther first type of node AP0 via a direct backhaul channel H4.

[0106] According to some aspects, the farther first type of node is the first type of node AP0 connected to the core network 2 in the form of a fiber connection 5.

[0107] According to some aspects, the node is a second type of node U 11 , which is adapted to communicate with an adjacent first type of node AP1 via a corresponding access channel h 11 and is adapted to communicate with the farther first type of node AP0 via a direct access channel h 13 .

[0108] As Figure 9B shown, according to some aspects, the first type of node AP1 in the wireless communication system 1 includes a processor unit 4, which is adapted to control communication with at least two other first type of nodes AP2, U 11 , AP0 in the wireless communication system, wherein at least one of the other nodes AP2, AP0 is a first type of node adapted to communicate with other first type of nodes in a backhaul communication manner. The processor unit 4 is further adapted to control receiving the signal x A sent from the adjacent first type of node AP0, and forwarding the signal x A to the receiving nodes AP2, U 11 . The processor unit 3 is further adapted to delete the forwarded signal x A from the buffer memory after sending the signal x A , regardless of whether the receiving node can decode the signal x A .

[0109] According to some aspects, the adjacent first type of node is the first type of node AP0 connected to the core network 2 in the form of a fiber connection 5.

[0110] The present disclosure also relates to a wireless communication system 1, which includes an integrated access and backhaul IAB network 7, and the IAB network in turn includes the nodes AP2, U Figure 9A and Figure 9B discussed above; AP1. 11

[0111] The present disclosure is not limited to the above, but may vary freely within the scope of the appended claims. For example, in the example discussed above, the first access point AP0 is directly connected to the third access point AP2 to provide the CPE U served by both the third access point AP2 and the fourth access point AP3 21 and U 22 ; U 31 and U 32 signals. However, according to some aspects, the first access point AP0 is adapted to receive a NACK for a specific signal directly from any access point that is not the closest to the first access point AP0 (e.g., directly from the fourth access point AP3). Then, the first access point AP0 is adapted to directly retransmit the specific signal to any access point that is not the closest to the first access point AP0, e.g., directly retransmit to the fourth access point AP3, during a second time period T2 in which the first access point AP0 and the fourth access point AP3 are temporarily inactive.

[0112] In the example discussed above, time slot 6 is divided into sub - slots RX s and TX s , each sub - slot having an access connection and a backhaul connection. In another approach, the time slot is divided into an access sub - slot and a backhaul sub - slot, where each sub - slot has DL and UL transmissions. Generally, the present disclosure can be applied to different time - allocation schemes.

[0113] According to some aspects, the efficiency of the present disclosure depends on the amount of interference added to the access link between the second access point AP1 and the CPE U 11 and U 12 served by it, in a manner such as direct transmission from the first access point AP0 to the third access point AP2. However, since APs are typically equipped with many antennas and advanced beam - forming methods, and also because direct communication via the direct channel H4 does not need to have a high rate and may thus have relatively low transmission power, the interference to the access link between the second access point AP1 and the CPE U 11 and U 12 served by it will be negligible. This is especially because IAB networks are typically used for fixed networks where channel measurements and parameter settings can be performed before data transmission.

[0114] According to some aspects, examples of important parts of the present disclosure are:

[0115] 1) As discussed previously, the present disclosure can be applied to establish a direct channel between two nodes such that one node is bypassed and removed. For example, the fourth access point AP3 can communicate directly with the first access point AP0 via a corresponding direct backhaul channel.

[0116] 2) In the described example, a time slot is divided into RX / TX sub - time slots RX s , TX s , and each sub - time slot has an access connection and a backhaul connection. In another approach, a time slot is divided into an access sub - time slot and a backhaul sub - time slot, and each sub - time slot has DL and UL transmissions. The present disclosure can be applied to different time - allocation schemes.

[0117] 3) The efficiency of the proposed method depends on whether a reasonably good direct backhaul channel H4 can be found. However, since most of the minimum SNR required for successful decoding has already been provided by the initial transmission of the signal x Figure 10 as shown A , a lower data rate can be used for the direct backhaul channel H4 without affecting the end - to - end data - transmission latency.

[0118] According to some aspects, the present disclosure can be easily extended to cases with an arbitrary number of hops, different relay methods, or star - network configurations.

[0119] According to some aspects, in this context, the term "signal" corresponds to a data signal or a data message. According to some aspects, in this context, the term "relay" corresponds to the term "forward".

[0120] According to some aspects, the node AP2, U A that sends a re - transmission request NACK for the signal x 11 can send it directly to the first access point AP0, or send it to the second access point AP1, and the second access point AP1 forwards the NACK to the first access point AP0.

[0121] The present disclosure has been described for a simple case with a relatively small number of hops, but the present disclosure can be applied to cases with an arbitrary number of hops and CPEs.

[0122] In the example, the third access point AP2 has been adapted to communicate directly with the first access point AP0 via the direct backhaul channel H4 instead of the fourth access point AP3 (which has to rely on relaying via the third access point AP2) for both uplink and downlink. According to some aspects, the fourth access point AP3 and possibly one or more other (not shown) access points can also be adapted to communicate directly with the first access point AP0 or other suitable access points via the corresponding direct backhaul channels.

[0123] According to some aspects, the wireless communication system 1 can be any suitable communication system including any suitable wireless network. According to some aspects, the wireless communication system 1 includes one or more IAB networks 7.

[0124] The present disclosure can be applied to both uplink (UL) transmissions and downlink (DL) transmissions as well as different types of HARQ.

[0125] Generally, the present disclosure relates to nodes AP2, U in a wireless communication system 1 11 , where the nodes AP2, U 11 are adapted to communicate with at least two other nodes AP1, AP0 in the wireless communication system 1, where the other nodes AP1, AP0 are first type nodes AP1, AP0 adapted to communicate with each other in a backhaul communication manner. The nodes AP2, U 11 are also adapted to receive a signal x sent from an adjacent first type node AP1 A , where the signal x A has been forwarded from at least one more distant first type node AP0. In the case where the decoding of the signal x A is unsuccessful, the nodes AP2, U 11 are adapted to request a retransmission (NACK) of the signal x A , and directly receive a retransmission of the signal x from the more distant first type node AP0 A .

[0126] According to some aspects, the nodes AP2, U 11 are adapted to directly send a retransmission request NACK of the signal x to the more distant first type node AP0 A .

[0127] According to some aspects, the node is a first type node AP2, which is adapted to communicate with an adjacent first type node AP1 through a corresponding backhaul channel H1, and is adapted to communicate with the more distant first type node AP0 via a direct backhaul channel H4.

[0128] According to some aspects, the more distant first type node is a first type node AP0 connected to the core network 2 in a fiber optic connection 5 manner.

[0129] According to some aspects, the node is a second type node U 11 , which is adapted to communicate with an adjacent first type node AP1 through a corresponding access channel h 11 , and is adapted to communicate with the more distant first type node AP0 via a direct access channel h 13 .

[0130] According to some aspects, the communication between the first type nodes AP0, AP1, AP2, AP3 is backhaul communication via at least one corresponding backhaul channel H1, H2, H3, H4, and where at least one first type node AP0, AP1, AP2, AP3 is adapted to via a corresponding access channel h 11 , h 12 ; h 21 , h 22 ; h31 and h 32 communicate with a corresponding set of second type nodes U 11 and U 12 ; U 21 and U 22 ; U 31 and U 32 Each set of second type nodes U 11 and U 12 ; U 21 and U 22 ; U 31 and U 32 includes at least one second type node U 11 and U 12 ; U 21 and U 22 ; U 31 and U 32 , wherein both the backhaul communication and the access communication are performed at each of the first type nodes AP0, AP1, AP2, AP3 through a common device.

[0131] According to some aspects, a retransmission of signal x is signaled during a temporarily inactive period T1 in which node AP2 and more distant node AP0 do not participate in any communication with other nodes A .

[0132] According to some aspects, the retransmission request (NACK) for signal x A is based on Hybrid Automatic Repeat reQuest (HARQ).

[0133] Generally, the present disclosure also relates to a first type node AP1 in a wireless communication system 1, wherein the first type node AP1 is adapted to communicate with at least two other nodes AP2, U 11 , AP0 in the wireless communication system 1, wherein at least one of the other nodes AP2, AP0 is a first type node adapted to communicate with other first type nodes in a backhaul communication manner. The first type node AP1 is adapted to receive signal x A sent from an adjacent first type node AP0, and forward signal x A to receiving nodes AP2, U 11 . The first type node AP1 is adapted to delete the forwarded signal x A from its buffer after having forwarded signal x A , regardless of whether the receiving node is able to decode signal x A .

[0134] According to some aspects, the adjacent first type node AP0 is connected to the core network 2 in a fiber optic connection 5 manner.

[0135] In general, the present disclosure also relates to a wireless communication system 1, which includes an integrated access and backhaul IAB network 7, which in turn includes at least the node AP2, U according to the above 11 and the first type of node AP1 according to the above.

Claims

1. A node (AP2, U 11 ) in a wireless communication system (1), wherein, The node (AP2, U 11 ) is adapted to: communicate with at least two other nodes (AP1, AP0) in the wireless communication system (1), wherein the other nodes (AP1, AP0) are first type nodes (AP1, AP0) adapted to communicate with each other in a backhaul communication manner; and Receiving a signal (x A ) sent from an adjacent first type of node (AP1), wherein the signal (x A ) has been forwarded from at least one more distant first type of node (AP0) to the adjacent first type of node (AP1); wherein, in the case where decoding of the signal (x A ) is unsuccessful, the node (AP2, U 11 ) is adapted to: Request a retransmission NACK for the said signal (x A ); and Receiving a retransmission of the signal (x A ) directly from a more distant node of the first type (AP0), wherein during the retransmission round, the adjacent node of the first type (AP1) is completely bypassed.

2. The node (AP2) according to claim 1, wherein, The node (AP2, U 11 ) is adapted to directly send a retransmission request NACK of the signal (x A ) to a farther first type node (AP0).

3. The node (AP2) according to claim 1 or 2, wherein, the node is a first type node (AP2) adapted to communicate with the adjacent first type node (AP1) through a corresponding backhaul channel (H1) and communicate with the farther first type node (AP0) via a direct backhaul channel (H4).

4. The node (AP2) according to claim 1 or 2, wherein, The farther first type node is a first type node (AP0) connected to the core network (2) by means of an optical fiber connection (5).

5. The node (U 11 ) according to claim 1 or 2, wherein, The node is a second type of node (U 11 ), which is adapted to communicate with the adjacent first type of node (AP1) through a corresponding access channel (h 11 ), and communicate with the farther first type of node (AP0) via a direct access channel (h 13 ).

6. The node (AP2, U 11 ) according to claim 1 or 2, wherein, The communication between the first type of nodes (AP0, AP1, AP2, AP3) is backhaul communication via at least one corresponding backhaul channel (H1, H2, H3, H4), and wherein at least one first type of node (AP0, AP1, AP2, AP3) is adapted to communicate via a corresponding access channel (h 11 , h 12 ; h 21 , h 22 ; h 31 , h 32 ) with a corresponding group of second type of nodes (U 11 , U 12 ; U 21 , U 22 ; U 31 , U 32 ), each group of second type of nodes (U 11 , U 12 ; U 21 , U 22 ; U 31 , U 32 ) includes at least one second type of node (U 11 , U 12 ; U 21 , U 22 ; U 31 , U 32 ), wherein both the backhaul communication and the access communication are performed at each first type of node among the first type of nodes (AP0, AP1, AP2, AP3) by a common device.

7. The node (AP2) according to claim 1 or 2, wherein, During a temporarily inactive period (T1) in which the node (AP2) and the further node (AP0) do not participate in any communication with other nodes, the retransmission of the signal (x A ) is issued.

8. The node (AP2, U 11 ) according to claim 1 or 2, wherein, The retransmission request NACK of the signal (x A ) is based on Hybrid Automatic Repeat reQuest (HARQ).

9. A method in a node (AP2, U 11 ) in a wireless communication system (1), wherein, The method includes: communicating (S1) with at least two other nodes (AP1, AP0) in the wireless communication system (1), wherein the other nodes (AP1, AP0) are of the first type and constitute first type nodes (AP1, AP0) that use backhaul communication when communicating with each other; and Receive (S2) a signal (x A ) sent from an adjacent first-type node (AP1), where the signal (x A ) has been forwarded from at least one more distant first-type node (AP0) to the adjacent first-type node (AP1); wherein, in the case where the decoding (S3) of the signal (x A ) is unsuccessful, the method includes: Request for retransmission of NACK for the signal (x A ) and Receiving (S5) the signal (x A ) directly from a more distant first type node (AP0), wherein during the retransmission round, the adjacent first type node (AP1) is completely bypassed.

10. The method according to claim 9, wherein, The method includes: directly sending (S41) the signal (x A ) a retransmission request NACK to a farther first type of node (AP0).

11. The method according to claim 9 or 10, wherein, the node is a first type node (AP2) for communicating with the adjacent first type node (AP1) through a corresponding backhaul channel (H1) and communicating with the farther first type node (AP0) via a direct backhaul channel (H4).

12. The method according to claim 9 or 10, wherein, The farther first type node is a first type node (AP0) connected to the core network (2) by means of an optical fiber connection (5).

13. The method according to claim 9 or 10, wherein, The node is a second type of node (U 11 ), which is used to communicate with the adjacent first type of node (AP1) through the corresponding access channel (h 11 ), and communicate with the farther first type of node (AP0) via the direct access channel (h 13 ).

14. The method according to claim 9 or 10, wherein The communication between the first type of nodes (AP0, AP1, AP2, AP3) is backhaul communication via at least one corresponding backhaul channel (H1, H2, H3, H4), and wherein at least one first type of node (AP0, AP1, AP2, AP3) is used to communicate with a corresponding group of second type of nodes (U 11 , h 12 ; h 21 , h 22 ; h 31 , h 32 ) via a corresponding access channel (h 11 , U 12 ; U 21 , U 22 ; U 31 , U 32 ), each group of second type of nodes (U 11 , U 12 ; U 21 , U 22 ; U 31 , U 32 ) includes at least one second type of node (U 11 , U 12 ; U 21 , U 22 ; U 31 , U 32 ), wherein both the backhaul communication and the access communication are performed by a common device at each of the first type of nodes (AP0, AP1, AP2, AP3).

15. The method according to claim 9 or 10, wherein The method includes: retransmitting the signal (x A ) during a temporarily inactive period (T1) in which the node (AP2) and the further node (AP0) are not used for communication with other nodes 16. The method according to claim 9 or 10, wherein The retransmission request NACK of the signal (x A ) is based on Hybrid Automatic Repeat reQuest (HARQ).

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