Patent Description:
Efforts are currently underway to define next generation wireless communication networks that provide greater deployment flexibility, support for a multitude of devices and services and different technologies for efficient bandwidth utilization. The next generation wireless communication networks are also expected to deploy new core networks that provide additional services and flexibility beyond currently available core networks.

<CIT> relates to a physical channel communication method and apparatus for random access in a cellular communication system including a plurality of relay nodes and user equipments using the same system information.

<CIT> relates to a mechanism within a mobile radio communications network whereby a User Equipment device performs an initial access procedure to a node of a Radio Access Network in a manner where such procedure is relayed by way of a further UE device serving as a UE Relay.

3GPP Draft R1-<NUM> relates to new radio (NR) initial access procedure design.

<CIT> discloses a random access through a relay station which is smoothly performed. The relay station performs wireless communications with a base station, and a mobile station performs wireless communications with the base station or relay station. The relay station limits reception of a radio signal from the base station at timing at which a radio signal is transmitted to the mobile station.

This document describes technologies that can be used by network devices to allocate random access resources to a class of wireless devices such as the integrated access and backhaul (IAB) node.

In one example aspect, a method of wireless communication is disclosed. The method includes configuring, by a first communication node, a first set of parameters related to random access procedure by a second communication node on a first communication link between the first communication node and the second communication node, and receiving, by the first communication node, from the second communication node, a random access signal that uses the first set of parameters on the first communication link. The first communication node also provides wireless connectivity to a third communication node via a second communication link that shares at least some transmission resources for random access transmissions with the first communication link. The first set of parameters include random access time-frequency resources, wherein the first communication node independently configures time domain resources of transmission resources for random access transmissions for the second communication node and the third communication node.

In another example aspect, another method of wireless communication is disclosed. The method includes, receiving, from a first communication node, a first set of parameters related to random access procedure by a second communication node on a first communication link between the first communication node and the second communication node, and transmitting, by the second communication node, to the first communication node, a random access signal that uses the first set of parameters on the first communication link, wherein the first communication node also provides wireless connectivity to a third communication node via a second communication link that shares at least some transmission resources for random access transmissions with the first communication link, wherein the first set of parameters include random access time-frequency resources, wherein the first communication node independently configures time domain resources of transmission resources for random access transmissions for the second communication node and the third communication node.

In yet another example aspect, a wireless communications apparatus comprising a processor is disclosed. The processor is configured to implement methods described herein.

In another example aspect, the various techniques described herein may be embodied as processor-executable code and stored on a computer-readable program medium.

The details of one or more implementations are set forth in the accompanying drawings, and the description below.

The present document relates to the field of wireless communications and, in particular, to a method and an apparatus for allocating random access resources of an IAB node in a mobile communication system.

Section headings are used in this document to facilitate readability and do not limit the embodiments and techniques described in each section to that section only. Accordingly, embodiments may use together with each other techniques described in different sections.

To make the objectives, technical solutions, and advantages of the present invention clearer, the following describes the embodiments of the present invention in detail with reference to the accompanying drawings. It should be noted that, in the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other arbitrarily.

The new generation of mobile communication system NR (new radio) allows more flexible network networking modes than the <NUM>, <NUM>, and <NUM> systems and the existence of new types of network nodes. Currently integrated IBA Nodes (Integrated Access and Backhaul Node) integrating a backhaul link and a normal NR access link can provide more flexible coverage and networking than a single cellular coverage. The method will be an important part of the future mobile communications network.

For a new generation of mobile communication systems using IAB nodes, IAB nodes can be regarded as ordinary terminals as well as base stations accessed by other terminals, as shown in <FIG>: IAB Node and IAB Donor for communication, the communication link is a backhaul link. In this case, the IAB Node1 can be regarded as an ordinary terminal; but the IAB Node1 can also communicate with other common terminal UEs in group A (Group A) and other IAB Node2, and the communication link is an access link from IAB Node1 aspect. This time, this IAB Node1 can be regarded as a special kind of base station. It becomes the relay between other ordinary terminals and other IAB Nodes with IAB donors. The special part lies in the fact that the IAB Node is a special type of integration of base station and terminal. Its deployment location is very different from that of ordinary terminals. For example, IAB Nodes are often fixed below the eaves, and they are much higher than ordinary terminals, this is easy for IAB Donor establishing a direct radio path to IAB Nodes; for example, the IAB Node often has more antennas ports than the normal terminal; also, for example, the IAB Node may need to be placed farther away from the IAB donor than the normal terminal (such as the IAB Node3 in the <FIG>) coverage of ordinary terminals, etc. These different points put different demands on the transmission of random access between the IAB Node and the IAB donor. It is necessary to consider the arrangement and configuration of the IAB Node's random access resources and formats in a targeted manner.

When the IAB node is deployed in the next generation of mobile communication network, the IAB node deployment location and the multi-antenna characteristic of the IAB node itself cause the random access format selection of the IAB node to be different from that of an ordinary terminal such as user equipment (UE). The random access format selection needs to match the coverage of different distances, different RF transmission environments, and the additional path loss values that need to be compensated. The IAB nodes generally have higher heights, and often have more direct radio paths with other network nodes such as a base station. This is in contrast to the lower height of ordinary terminals, which leads to significantly different propagation environments in urban areas where the radio path is mostly indirect. For example, most user devices may be operated within <NUM> feet of ground, where many other interfering objects such as cars, buildings and trees are found. On the other hand, IAB devices may often be deployed near roof tops, and may be operating at heights of <NUM> to <NUM> feet or above, thus avoiding many interferers or reflectors experienced by user devices.

In general, because an ordinary terminal is mainly in an indirect path scenario, the path loss value that needs to be compensated is also relatively high. This scenario may force the wireless system to use the random access format B4 or longer format. The random access format B4 has a large number of short sequences (<NUM>, to be precise). More short sequences are accumulated to achieve energy gain to compensate for higher path loss. However, since the guard time of the prefix and suffix of the B4 format is shorter than that of the random access format C2, under the scenario that the coverage distance is determined only by the round-trip time of the electromagnetic signal between the base station and the terminal, the effective coverage of a B4 transmission extends over an area that is less than that of C2. That is to say, the format C2 is suitable for the scenario that the coverage is wider than the normal terminal and is based on the direct radio path.

In addition, typically, an IAB node has more antennas than a typical UE. Therefore, path loss is not the main transmission obstacle that the IAB node needs to overcome when sending a random access signal. The random access format C2 has a long enough prefix and guard time suffix to resist large time delays due to propagation delay. Therefore, IAB nodes may prefer to use C2 format random access signals over another format such as the B4 random access format.

<FIG> shows the random access format B4, A1 and C2 signal structure.

Table <NUM> shows examples of parameters of random access formats B4, C2, and A1. The column headers use the following abbreviations: CP For the cyclic prefix, GP is the guard time, Ts is the sampling point.

However, in the existing draft standards of new generation communication systems, only one random access signal format is allowed to be allocated in the same BWP (bandwidth part), and it is not allowed to simultaneously configure the formats B4 and C2. Because if the formats B4 and C2 are configured at the same time, since the prefix lengths of the two formats are different, the relative starting points of the effective short sequence symbols are different, which may cause ambiguity in the timing determination. In addition, because the number of short sequence symbols supported by the two formats is different, random access preamble signals cannot be blindly detected in a longer format, which may cause access failure. Therefore, when two or more random access signal formats are possible for a same bandwidth part (BWP), the type of the random access signal format actually being used by a transmission can be effectively distinguished at the base station side using techniques described herein. The following four examples illustrate the related solutions.

As shown in <FIG>, the IAB Node1 is within the normal coverage of the IAB donor. The normal coverage refers to the maximum coverage that an ordinary terminal that is not an IAB node can support. In the normal coverage, code division, specifically, the specific index of the IAB node within the range of the random access preamble index can be used to distinguish from the normal terminal. In general, BWP in the next-generation mobile communication system supports the terminal to randomly select among <NUM> random access preambles. In addition to this, some embodiments may follow a rule that some of the <NUM> random preamble indexes are dedicated to the IAB node, and the base station can identify whether a received random access preamble sequence was sent by the IAB node or by the non-IAB node by identifying the index of the received random access preamble from all possible preambles (e.g., <NUM> preambles), and then checking whether the index was from dedicated portion or from the non-dedicated portion of the random access indexes.

As shown in <FIG>, the IAB Node3 is outside the normal coverage of the IAB donor. Here, the "normal" coverage may refer to a nominal range of coverage for which the corresponding base station that is the IAB donor. Due to the difference in coverage with ordinary terminals, e.g., different physical layer characteristics of the wireless channel between the IAB donor and the IAB node, in some embodiments, the IAB nodes may use different random access preamble formats to meet the need for enhanced coverage, such as using the format C2 that is specifically used for coverage enhancement.

The set of random access preamble sequences for the next generation mobile communication system may be obtained by cyclically shifting a root sequence multiple times. If all cyclic shifts under the same root sequence do not satisfy the <NUM> indexes in BWP, embodiments should use more root sequences to generate more random access sequence indexes until a total of <NUM> indexes are generated. The size of the cyclic shift (Ncs) determines the number of sequences that can be generated under a single root sequence. The larger the Ncs is, the fewer the sequences that can be generated, and vice versa. Since the value of Ncs should meet the requirement of the zero correlation window, its value depends on the size of the coverage area of the cell. The larger the coverage area of the cell, the larger the value of Ncs should be, and the smaller the coverage area, smaller the value of Ncs is. Since the coverage of IAB Node3 is larger than that of normal terminals, the Ncs_IAB of IAB Node3 should be larger than the cyclic shift Ncs_UE of random access sequences of normal terminals or UEs.

In the case where Ncs is different, the IAB node's root sequence of the random access preamble sequence should not be the same as the random access root sequence of an ordinary terminal. Furthermore, its root sequence should be independent of the random access root sequence of an ordinary terminal. In addition to the normal terminal's random access root sequence and Ncs, the system also should configure an independent random access root sequence and Ncs_IAB for IAB nodes. The IAB-specific root sequence and Ncs_IAB determine the set of random access sequences available for IAB nodes.

Compared with ordinary terminals (e.g., UEs), IAB nodes have a smaller density in the network deployments, and therefore require fewer random access resources. Thus, a random access time-frequency resource arrangement for IAB nodes could be sparser than for ordinary UEs. Even so, there is always a possibility of occurrence of collision of random access transmissions initiated between the two (IAB node and UE), and thus cannot fundamentally avoid the problem that the random access sequence transmitted by the ordinary terminal and the IAB node collides on the same time-frequency resource. Although from the perspective of the IAB donor node, when the random access sequences sent by the ordinary terminal and the IAB node collides on the same time-frequency resource, it may be possible to determine whether the detected random access sequence is an IAB-dedicated random access preamble sequence. The mapping relationship between the random access resource of the IAB node and the downlink signal and the mapping relationship between the normal terminal random access resource and the downlink signal are not the same, and when in the same time-frequency resource being used for signal transmission, if transmissions with two random access formats that collide with each other, the best receiving beam cannot simply be taken into consideration at the receiving side of the base station, which greatly increases the probability of detection failure.

<FIG> illustrates an example of collision between the receive beams of the IAB random access and random access of ordinary users. As shown in <FIG>, the ordinary terminal uses the B4 format. There is only one random access sequence <NUM> that can fit within a time slot. In this case, the mapped downlink signal is a sync block <NUM> (SSB <NUM>). In this configuration, an IAB node uses a C2 format. Since C2 is shorter than B4, it is possible to have two consecutive random access sequences <NUM> and <NUM> in the time slot, and the corresponding mapped sync blocks are <NUM> and <NUM>. The base station may use either receive beam <NUM> corresponding to sync block <NUM> or receive beams <NUM> and <NUM> corresponding to sync blocks <NUM> and <NUM> at this random access opportunity (RO: RACH occasion). If the base station uses beam1, this is not the best beam for sequences <NUM> and <NUM>, and if the base station uses beam2 and beam3, these are not the best beams for sequence <NUM>. A single best beam cannot fit for all situations.

Therefore, one way to solve the conflict problem is still to configure the random access time-frequency resources of IAB nodes and the random access time-frequency resources of ordinary terminals independently, and to ensure that there is no overlap between them. The sub-optimal method is the independent configuration of both time-frequency resources, but allows a certain percentage of overlap. If it is indeed because of resource limitation, the random access time-frequency resources of the IAB node and the ordinary terminal cannot be configured independently, then it is beneficial to ensure that the downlink signals mapped by the corresponding random access occasions on the same time-frequency resource are consistent.

Still taking <FIG> as an example, an ordinary terminal uses the B4 format. There is only one random access sequence <NUM> in a time slot. The mapped downlink signal is a sync block <NUM>, the IAB node uses a C2 format, and there are two random access sequence in one time slot. The successive random access sequences <NUM> and <NUM> must also have a mapped sync block of <NUM>. This particular mapping relationship guarantees that it is not difficult to implement because the ratio of the number of available B4 and C2 in a time slot is determined, and the mapping relationship between the downlink signal and the random access occasion can be set according to this ratio. For example, if the mapping relationship between the downlink signal and the random access opportunity is set to <NUM>:<NUM> for the B4 format, the mapping relationship between the downlink signal and the random access opportunity configured in the C2 format is <NUM>:<NUM>.

The IAB node is a hybrid of a network node and a terminal. The node itself has an independent cell identifier (Cell ID) and independent radio resource management capability. The IAB node can configure random access parameters that are independent of ordinary terminals for IAB terminals within the coverage of the IAB node. Since the conventional coverage controlled by IAB nodes is much smaller than that of the ordinary anchor base station , and the multi-antenna capability of IAB is also different from that of anchor base stations, it is also useful to configure the IAB terminals within the coverage of IAB nodes to be independent of ordinary terminal's random access parameters. For example, the random access format A1 is configured for the IAB terminal that within the coverage of the IAB node, and the random access format of the terminal under the control of the anchor node or the IAB parent node base station is B4, and the total length of the random access format A1 sequence is shorter. This makes the format suitable for a cell with a very smaller coverage and also facilitates control of interference to random access signals sent by ordinary terminals. The IAB node should therefore configure the IAB terminal with a random access root sequence and Ncs independent of the normal terminal and the IAB node.

The parameters of the random access procedure, configured by the IAB node to the IAB terminal, may also be reported to the IAB donor or the IAB parent node. Reporting the corresponding random access resource parameter is beneficial to the IAB donor or the IAB parent node to properly configure the RACH resources of the IAB node and the IAB node to receive the downlink backhaul link resources according to the RACH resources of the IAB terminal so as to avoid the collision with RACH access link of the IAB terminal. Resolving resource conflicts on the access link is especially important when the IAB uses wavelength division multiplexing to isolate return links and access links.

<FIG> is a flowchart depiction of a method <NUM> of wireless communication. The method <NUM> includes configuring (<NUM>), by a first communication node, a first set of parameters related to random access procedure by a second communication node on a first communication link between the first communication node and the second communication node, and receiving (<NUM>), from the second communication node, a random access signal that uses the first set of parameters on the first communication link. The first communication node also provides wireless connectivity to a third communication node via a second communication link that shares at least some transmission resources with the first communication link. The first set of parameters includes one or more of a random access format, a random access sequence index set, a random access sequence root sequence index, a random access cyclic shift, and random access time-frequency resources.

<FIG> is a flowchart depiction of an example method <NUM> of wireless communication. The method <NUM> includes, receiving (<NUM>), from a first communication node, a first set of parameters related to random access procedure by a second communication node on a first communication link between the first communication node and the second communication node, and transmitting (<NUM>), from the second communication node, a random access signal that uses the first set of parameters on the first communication link. The first communication node also provides wireless connectivity to a third communication node via a second communication link that shares at least some transmission resources with the first communication link. The first set of parameters includes one or more of a random access format, a random access sequence index set, a random access sequence root sequence index, a random access cyclic shift, and random access time-frequency resources.

With reference to methods <NUM> and <NUM>, in some embodiments, the first communication node may be an IAB parent node (e.g., a base station or another network node). In such a case, the second communication node may be an IAB node and the first communication link may be a backhaul link. In some embodiments, the first communication node, e.g., the IAB parent node, may also be configured to provide wireless connectivity to a third communication node such as a user device or UE. In such a case, the communication link between the first and third communication nodes may be the wireless channel to/from the user device and from/to the base station.

With reference to methods <NUM> and <NUM>, in some embodiments, the configuration of the random access format in the first set of parameters is not related to the random access format in the second set of parameters used by the third node for random access using the second communication link, and therefore these parameters may be independently assigned.

As described, several of the parameters associated with random access channel procedure may be used during methods <NUM> and <NUM>. These parameters may include random access format, a random access sequence index set, a random access sequence root sequence index, a random access cyclic shift, and random access time-frequency resources. Furthermore, these parameters may be independently assigned on the first and second communication links. For example, these assignments may be based on the conditions of each communication link, and decision taken regarding which parameter to select for use on one link may not have any influence on the decision taken for the other link. In some embodiments, the second communication node (e. g, an IAB node) may provide wireless connectivity to another network node. This another network node may be an IAB node or may be a UE.

<FIG> shows an example of a wireless communication apparatus <NUM>. The apparatus <NUM> may implement the methods <NUM> or <NUM> or other techniques described in the present document. The apparatus <NUM> may be, for example, the first communication node, the second communication node, or the third communication node described herein. For example, the apparatus <NUM> may implement functionality of a base station (e.g., eNB or gNB). In some embodiments, the apparatus <NUM> may be used to implement a user device such as a smartphone, an IoT device, a laptop, a tablet, and so on.

The apparatus <NUM> includes one or more processor <NUM>. The apparatus <NUM> may include one or more memories <NUM>. The apparatus <NUM> may include one or more transmitters <NUM>. The apparatus <NUM> may include one or more receivers <NUM>. The processor <NUM> may be configured to execute code and implement a wireless communication method such as method <NUM> or method <NUM>. The memory <NUM> may be used to store processor-executable code, data, results of intermediate calculations during the execution of wireless communication methods, and so on. The transmitter <NUM> may be configured to transmit, via a network interface, at least some of the various messages and signals described herein. The receiver <NUM> may be configured to receive, via a network interface, at least some of the signals and messages described herein. The apparatus <NUM> may use multiple transmitters and or receivers, for example, for performing communication on a cellular wireless and a backhaul connection.

Claim 1:
A method for wireless communications, comprising:
configuring (<NUM>), by a base station, a first set of parameters related to random access procedure, wherein the random access procedure is performed by an integrated access and backhaul, IAB, node on a first communication link between the base station and the IAB node; and
receiving (<NUM>), by the base station, from the IAB node, a random access signal that uses the first set of parameters on the first communication link;
wherein a second communication link between the base station and a user equipment, UE, shares at least some transmission resources for random access transmissions with the first communication link;
wherein the first set of parameters include random access time-frequency resources;
wherein the base station independently configures the time-frequency resources for random access transmissions for the first communication link and the second communication link, wherein the at least some transmission resources overlap; and
wherein an arrangement of the time-frequency resources of the transmission resources configured for the IAB node is sparser than an arrangement of the time-frequency resources of the transmission resources configured for the UE.