Patent Application
20240147346
The present disclosure relates to the field of cellular networks and in particular to routing data over a wireless communication link in a cellular network.
In cellular networks, network coverage to instances of user equipment (UEs) is provided by radio network nodes, also known as base stations. Traditionally, each radio network node has a backhaul connection to the core network CN using a wired connection, e.g. over an optical cable and/or galvanic cable.
In order to reduce the need for wired connections, modern cellular networks, such as 5G (fifth generation) and LTE (Long-term evolution) support radio based backhaul traffic. For instance, in 5G, this is implemented using integrated access and backhaul (IAB) nodes. An IAB node is a radio network node that provides access for UEs, but does not need to have a wired-based connection for its backhaul communication. Instead, an IAB node connects to an upstream radio network node (towards the core network) over a wireless communication link in accordance with the radio network. In other words, backhaul traffic for the IAB node is provided using the radio network of the cellular network. It is possible to extend the network with additional IAB nodes having their backhaul connection via another IAB node, such that a wire-connected donor IAB node can provide a backhaul connection to a downstream IAB node via one or more intermediate IAB nodes.
Duplex communication can be provided using time-division duplex (TDD). This implies that each radio network node is scheduled between reception and transmission for backhaul communication as well as for regular UE communication to allow the different radio network nodes to interoperate. The time slots are relatively short to keep latency of communication low.
When a downstream signal is provided from an IAB donor node via an intermediate node to a downstream IAB node, the intermediate IAB node needs to perform post-processing of the downstream signal for demodulation and decoding. Furthermore, in order to forward the downstream signal to the downstream IAB node, the signal must be pre-processed to be ready for transmission. Since the time slots for transmission and reception are kept short, there is often not sufficient time for the intermediate IAB node to perform post-processing and pre-processing of the downstream signal for it all to be ready at the next available time slot for IAB downstream transmission. The transmission of the downstream signal to the downstream IAB node thus needs to wait until the next possible time slot, which causes delay. This delay reduces the applicability of IABs, especially where latency requirements are strict, causing wired backhaul to be required.
One object is to reduce delay where a downstream signal is transmitted from an IAB donor node to a downstream IAB node via an intermediate IAB node.
According to a first aspect, it is provided a method for routing data over a wireless communication link in a cellular network, the method being performed in an intermediate integrated access and backhaul, IAB, node. The method comprises the steps of: receiving a downstream signal from an upstream node, the downstream signal comprising control data and payload data, wherein the downstream signal is intended for a downstream IAB node; determining that the downstream IAB node is the recipient of the downstream signal by determining that the control data of the downstream signal can be descrambled using a scrambling identifier of the downstream IAB node; and forwarding the payload data of the downstream signal to the downstream IAB node.
The forwarded payload data of the downstream signal may comprise in-phase quadrature, IQ, samples as received in the downstream signal.
The method may further comprise the step, prior to the step of forwarding the payload data of the downstream signal, of: aligning IQ samples received in the payload data of the downstream signal to constellation points of an assigned modulation scheme of the payload data of the downstream signal.
The scrambling identifier may be a cell radio network temporary identifier, C-RNTI, of the downstream IAB node.
The method may further comprise the steps, after the step of forwarding the payload data of the downstream signal, of: fully decoding the payload data of the downstream signal and determining whether the full demodulating was successful; and providing feedback on success of the full demodulating to the upstream node.
According to a second aspect, it is provided an intermediate integrated access and backhaul, IAB, node, for routing data over a wireless communication link in a cellular network. The intermediate IAB node comprises: a processor; and a memory storing instructions that, when executed by the processor, cause the intermediate IAB node to: receive a downstream signal from an upstream node, the downstream signal comprising control data and payload data, wherein the downstream signal is intended for a downstream IAB node; determine that the downstream IAB node is the recipient of the downstream signal by determining that control data of the downstream signal can be descrambled using the scrambling identifier of the downstream IAB node; and forward the payload data of the downstream signal to the downstream IAB node.
The forwarded payload data of the downstream signal may comprise in-phase quadrature, IQ, samples as received in the downstream signal.
The intermediate IAB node may further comprise instructions that, when executed by the processor, cause the intermediate IAB node to: align IQ samples received in the payload data of the downstream signal to constellation points of an assigned modulation scheme of the payload data of the downstream signal.
The scrambling identifier may be a cell radio network temporary identifier, C-RNTI, of the downstream IAB node.
The intermediate IAB node may further comprise instructions that, when executed by the processor, cause the intermediate IAB node to, prior to forwarding the payload data of the downstream signal: fully decode the payload data of the downstream signal and determining whether the full demodulating was successful; and provide feedback on success of the full demodulating to the upstream node.
According to a third aspect, it is provided a computer program for routing data over a wireless communication link in a cellular network. The computer program comprises computer program code which, when executed on an intermediate integrated access and backhaul, IAB, node, causes the intermediate IAB node, to: receive a downstream signal from an upstream node, the downstream signal comprising control data and payload data, wherein the payload data comprises the data for the user device, wherein the downstream signal is intended for a downstream IAB node; and determine that the downstream IAB node is the recipient of the downstream signal by determining that control data of the downstream signal can be descrambled using a scrambling identifier of the downstream IAB node; and forward the payload data of the downstream signal to the downstream IAB node.
According to a fourth aspect, it is provided a computer program product comprising a computer program according to the third aspect and a computer readable means on which the computer program is stored.
According to a fifth aspect, it is provided a method for routing data over a wireless communication link in a cellular network, the method being performed in an integrated access and backhaul, IAB, donor node. The method comprises the steps of: receiving data for a user device; determining that the data is to be routed via an intermediate IAB node to a downstream IAB node; generating a downstream signal intended for the downstream IAB node, which comprises scrambling control data of the downstream signal using a scrambling identifier of the downstream IAB node, wherein the downstream signal comprises the control data and payload data, wherein the payload data comprises the data for the user device; and transmitting the downstream signal to the intermediate IAB node.
The scrambling identifier may be a cell radio network temporary identifier, C-RNTI, of the downstream IAB node.
According to a sixth aspect, it is provided an integrated access and backhaul, IAB, donor node, for routing data over a wireless communication link in a cellular network. The IAB donor node comprises: a processor; and a memory storing instructions that, when executed by the processor, cause the IAB donor node to: receive data for a user device; determine that the data is to be routed via an intermediate IAB node to a downstream IAB node; generate a downstream signal intended for the downstream IAB node, which comprises scrambling control data of the downstream signal using a scrambling identifier of the downstream IAB node, wherein the downstream signal comprises the control data and payload data, wherein the payload data comprises the data for the user device; and transmitting the downstream signal to the intermediate IAB node.
The scrambling identifier is a cell radio network temporary identifier, C-RNTI, of the downstream IAB node.
According to a seventh aspect, it is provided a computer program for routing data over a wireless communication link in a cellular network. The computer program comprises computer program code which, when executed on an integrated access and backhaul, IAB, donor node, causes the IAB donor node to: receive data for a user device; determine that the data is to be routed via an intermediate IAB to a downstream IAB node; generate a downstream signal intended for the downstream IAB node, which comprises scrambling control data of the downstream signal using a scrambling identifier of the downstream IAB node, wherein the downstream signal comprises the control data and payload data, wherein the payload data comprises the data for the user device; and transmitting the downstream signal to the intermediate IAB node.
According to an eighth aspect, it is provided a computer program product comprising a computer program according to the seventh aspect and a computer readable means on which the computer program is stored.
Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to “a/an/the element, apparatus, component, means, step, etc.” are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.
Aspects and embodiments are now described, by way of example, with reference to the accompanying drawings, in which:
The aspects of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown. These aspects may, however, be embodied in many different forms and should not be construed as limiting; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and to fully convey the scope of all aspects of invention to those skilled in the art. Like numbers refer to like elements throughout the description.
The cellular network 8 may e.g. comply with any suitable cellular network standards, such as 5G NR (New Radio), 6G, etc. or any other current or future wireless network, as long as the principles described herein are applicable.
Over the wireless interface, downstream communication is defined as the direction from the core network 13 towards one of the UEs 2 and upstream communication is defined as the direction from one of the UEs 2 towards the core network 13. Downlink communication is defined as transmission from a particular radio network node and uplink communication is reception at a radio network node. The quality of the wireless radio interfaces can vary over time and depending on the position of the transmitters and receivers, due to effects such as fading, multipath propagation, interference, noise, etc.
Each radio network node 3a-c transmits both control data and payload data. Please note that the structure and naming of the channels and signals used herein are not limiting and can vary depending on the radio access technology that is used. The channel and signal structure is exemplified herein as applied for 5G NR. Control data can be transmitted from each radio network node 3a-c as Downlink Control Information (DCI) on a Physical Downlink Control Channel (PDCCH). The DCI can specify where payload data occurs on a Physical Downlink Shared Channel (PDSCH) for the recipient UE 2. Conventionally, the DCI is scrambled with a scrambling identifier. Such a scrambling identifier can e.g. be a Cell Radio Network Temporary Identifier (for the UE 2). The UE 2 descrambles its DCI using its scrambling identifier, determines where to find its downlink payload data on the PDSCH. This allows the UE 2 to receive, demodulate and decode its downlink data. It is to be noted that the UE attempts to descramble DCIs addressed to other UEs, but only succeeds in descrambling and decoding DCIs that are scrambled with its own scrambling identifier, and according to embodiments presented herein, scrambling identifiers for any downstream IAB nodes.
The core network 13 provides central functions and connection to a wide area network, such as the Internet.
The radio network nodes 3a-c in
There is an IAB donor node 3a with a wired connection to the core network 13. The IAB donor node 3a provides a radio network accessible for UEs 2 as well as a wireless communication link for the intermediate IAB node 3b. The intermediate IAB node 3b, in turn, provides a radio network accessible for UEs 2 as well as a wireless communication link for a downstream IAB node 3c. The term downstream IAB node 3c defines that the downstream IAB node is downstream from the intermediate IAB node 3b. The downstream IAB node 3c provides a radio network accessible for UEs. Each IAB node 3b, 3c implements UE functionality for the nearest upstream radio network node. In other words, the intermediate IAB node 3b implements UE functionality for communication with the IAB donor node 3a and the downstream IAB node 3c implements UE functionality for communication with the intermediate IAB node 3b.
Using the structure of
It is to be noted that there could be multiple intermediate IAB nodes in sequence between the IAB donor node 3a and the downstream IAB node 3c, even though only one intermediate IAB node 3b is shown in
In TDD, transmission and reception does not take place simultaneously. For a non-IAB node, this is handled by alternating between transmission timeslots and receiving timeslots. The radio network nodes of a network can be synchronized so that they all transmit at the same time and receive at the same time. With IAB, this simple structure does not work, since the nodes have both the UE role (the MT) and the base station role (the DU). A more complex transmit/receive structure is needed which limits the available slots for upstream and downstream backhaul communication even more. Hence, for low latency, it is important to be able to utilize the first available slot.
In a first time slot 11a, the IAB donor node 3a is in a transmit (Tx) state and transmits both IAB downstream (DS) communication to the MT of the intermediate IAB node 3b as well as downlink (DL) communication to any connected UEs 2. Similarly, the downstream IAB node 3c is in a Tx state; its MT transmits IAB upstream (US) communication to the intermediate IAB node 3b and the DU transmits DL communication to any connected UEs 2. The intermediate IAB node 3b is in a receiving (Rx) state; its MT receives the IAB DS communication from the IAB donor node 3a and its DU received the IAB US communication from the downstream IAB node 3c.
In a second time slot 11b, no IAB backhaul communication occurs, and all three nodes 3a-c are in an RX state and receive UL communication from their connected UEs 2.
In a third time slot 11c, the intermediate IAB node 3b is in a Tx state; its MT transmits IAB US communication to the IAB donor node 3a and its DU transmits IAB DS communication to the MT of the downstream IAB node 3c. Also, the DU of the intermediate IAB node 3b transmits DL communication to its connected UEs 2. Both the IAB donor node 3a and the downstream IAB node 3c are in an Rx state here.
In a fourth time slot 11d, no IAB backhaul communication occurs, and all three nodes 3a-c are in a TX state, transmitting DL communication to their connected UEs 2.
The fifth time slot 11e is the same as the second time slot 11b.
Looking into this communication in some more detail, in the first slot 11a, the IAB donor node 3a transmits the downstream signal 15. The intermediate IAB node 3b receives the downstream signal 15 and performs postprocessing 16. If the intermediate IAB node 3b is to transmit corresponding downstream signal 15 in the third slot 11c, pre-processing 17 needs to occur to prepare the signal (e.g. scheduling, encoding, modulating).
However, due to the limited processing power of the intermediate IAB node 3b, there is a time conflict 18 since there the pre-processing 17 would need to start before the postprocessing 16 has finished. Since this is not possible, the corresponding downlink signal will need to wait until the next available time slot (not shown) after the third time slot 11c when downstream IAB communication can be transmitted by the intermediate IAB node 3b. Referring to
According to embodiments presented herein, the intermediate IAB node can determine that the downstream signal is destined for another IAB node before demodulating and decoding the downstream signal when received from the upstream node. This is achieved by the intermediate IAB node 3b finding that control signals of the downstream signal are scrambled for the downstream IAB node using its scrambling identifier, e.g. its C-RNTI.
Looking into this in some more detail, the IAB donor node 3a generates 20 the downstream signal, and encodes control data for the downstream signal using the scrambling identifier of the downstream IAB node 3c. The IAB donor node 3a then transmits the downstream signal 15 over its radio interface to the intermediate IAB node 3b.
The intermediate IAB node 3b determines 23 that it should forward the downstream signal 15 to the downstream IAB node 3c by determining that the control information for the downstream signal 15 can be descrambled using the scrambling identifier of the downstream IAB node 3c. At this point, the intermediate IAB node 3b forwards the downstream signal 15 to the downstream IAB node 3c.
From the perspective of the downstream IAB node 3c, the downstream signal 15 can be received in a conventional manner. The downstream IAB node 3c determines 25 the UE 2 to transmit to and transmits the downstream signal 15 to the determined UE 2 as known in the art per se.
Compared to the timing illustrated in
In a receive signal step 40, the intermediate IAB node 3b receives a downstream signal from an upstream node. The downstream signal comprises control data and payload data. The downstream signal is intended for a downstream IAB node 3c. The upstream node can be an IAB donor node 3a or an upstream intermediate IAB node. The control data be in the form of DCI on the PDCCH. The control data is received over the wireless access provided by the nearest upstream radio network node, i.e. the IAB donor node 3a or upstream intermediate IAB node.
In a determine downstream node step 44, the intermediate IAB node 3b determines that the downstream IAB node 3c is the recipient of the downstream signal. This is achieved by determining that control data of the downstream signal can be descrambled using a scrambling identifier of the downstream IAB node 3c. The scrambling identifier can be obtained from local memory. The scrambling identifier can be the C-RNTI of the downstream IAB node 3c. The intermediate IAB node 3b obtains one or more scrambling identifiers of respective downstream IAB nodes to which downstream data could potentially need to be forwarded. This depends on the network topology and is preconfigured (manually, automatically or semi-automatically) prior to this method commencing.
The control data is in the form of DCI on PDCCH. Hence, in addition to descrambling its own DCI using its own scrambling identifier, the intermediate IAB node 3b attempts to descramble DCI for the downstream IAB node 3c using the scrambling identifier of the downstream IAB node 3c. If there are several downstream IAB nodes, the intermediate IAB node 3b attempts to descramble for each one of the downstream IAB nodes. When this descrambling (and subsequent decoding) is successful for at least one downstream IAB node, that indicates that the downlink signal should be forwarded to the downstream IAB node 3c.
This can be the same procedure as the blind decoding known from the prior art per se, but this is here performed multiple scrambling identifiers, i.e. not only for its own scrambling identifier, as in the prior art.
When the downstream node has been determined, the intermediate IAB node 3b has thus both demodulated and decoded the DCI scrambled with the scrambling identifier of the downstream IAB node 3c, to determine where the payload data is scheduled. The intermediate IAB node receives the payload data on the PDSCH as pointed to by the DCI. The payload data is received first as analogue data, converted to digital data and is represented as samples in complex data form as in-phase quadrature (IQ).
In one embodiment, instead of determining the downstream IAB node 3c based on the scrambling identifier, the downstream IAB node 3c is determined based on presence of an indication in the payload data, received on PDSCH. This step then comprises demodulating and decoding a strict subset of the payload data of the downstream signal, yielding a decoded and demodulated section; and determining that the demodulated and decoded section comprises an indication that the downstream IAB node 3c is the recipient of the downstream signal. The strict subset of the downstream signal can be in a section of the payload data that is received first, to reduce any delay of forwarding the payload data, see also the corresponding perspective from the IAB donor node in the description for step 146 below.
The control data is typically transmitted first in each time slot. This allows the intermediate IAB node 3b to quickly understand that the payload data of the downstream signal is to be forwarded, and gives more time for the intermediate IAB node 3b to pre-process for downstream transmission, e.g. for scheduling.
In a forward step 48, the intermediate IAB node 3b forwards the payload data of the downstream signal (received on PDSCH) to the downstream IAB node 3c. It is to be noted that the intermediate IAB node 3b can generate the control data for the forwarding, even if the payload data is the same. This is done to give the intermediate IAB node freedom to schedule the payload data where it is most appropriate.
When the payload data includes an indication that the downstream IAB node 3c is the recipient of the downstream signal, this indication is removed from the payload data prior to forwarding. If there are multiple intermediate IAB nodes 3b, only the last intermediate IAB node removes the indication.
In one embodiment, the forwarded payload data of the downstream signal comprises IQ samples as received in the downstream signal, i.e. the IQ sample values are not altered prior to forwarding, to reduce any time for forwarding the signal.
It is to be noted that the forwarded payload data can be data destined for a UE, operation and maintenance data for a radio network node, application control data for the radio network node, or any other suitable data, such as data for any equipment connected to the downstream IAB node.
Looking now to
In an optional align IQ samples step 46, the intermediate IAB node 3b aligns IQ samples received in the downstream signal to constellation points of an assigned modulation scheme of the downstream signal. The aligning here implies that the value, corresponding to the IQ sample, is set to be the nearest constellation point in an IQ plane. The modulation scheme is defined e.g. as part of a Modulation and Coding Scheme (MCS), communicated from the upstream radio network node, and can be e.g. one of Quadrature phase-shift keying (QPSK), 16 Quadrature Amplitude Modulation (QAM), 64 QAM, 256 QAM, etc.
In an optional fully decode step 50, the intermediate IAB node 3b fully decodes the payload data of downstream signal (on PDSCH) and determines whether the full decoding was successful.
In an optional provide feedback step 52, the intermediate IAB node 3b provides feedback on success of the full demodulating to the upstream node, e.g. as a Hybrid Automatic Repeat Request (HARQ) response.
When steps 50 and 52 are implemented, the IAB donor node 3a is provided with feedback on transmission performance on the hop to the intermediate IAB node, at the cost of the intermediate IAB node having to fully decode the payload data of the downstream data, It is to be noted that the forwarding of payload data in step 48 can proceed without await the completion of steps 50 and 52, whereby the execution of steps 50 and 52 does not impose any delay on the forwarding.
It is to be noted that steps 50 and 52 do not need to be performed. In other words, the intermediate IAB node 3b would in this case not demodulate or decode the payload data of the downstream signal (on PDSCH), and only forwards the IQ samples, resulting in a simpler and faster implementation of the forwarding in the intermediate IAB node 3b. In this case, feedback on reception is provided from downstream nodes, such as the downstream IAB node 3c and/or the UE 2. The feedback is then relayed back upstream via the intermediate IAB node 3b.
In a receive data step 140, the IAB donor node 3a receives data for a user device, the IAB donor node 3a.
In a determine routing step 142, the IAB donor node 3a determines that the data is to be routed via an intermediate IAB node 3b to a downstream IAB node 3c.
In a generate downstream signal step 146 the IAB donor node 3a generates a downstream signal intended for the downstream IAB node 3c. This comprises scrambling control data (of the DCI) of the downstream signal using a scrambling identifier of the downstream IAB node 3c. As explained above, the scrambling identifier can be the C-RNTI of the downstream IAB node 3c. The downstream signal comprises the control data and payload data. The payload data comprises the data for the user device.
When the intermediate IAB node 3b is to determine the downstream IAB node 3c based on information in the payload data, the generate downstream signal step 146 does not need to scramble the control data using the scrambling identifier of the downstream IAB node, and instead scrambles control data using the scrambling identifier of the intermediate IAB node, as known in the art per se. In such an embodiment, the generate downstream signal step 146 comprises generating an indication that the downstream IAB node 3c is the recipient of the downstream signal and including the indication in the payload data, i.e. in the PDSCH part. The indication can be provided in a section of the payload data that is transmitted first. The structure and content of the indication is according to a predefined format allowing the intermediate IAB node 3b to determine that the data of the signal should be forwarded to the downstream IAB node 3c.
In a transmit step 148 the IAB donor node 3a transmits the downstream signal to the intermediate IAB node 3b, over the wireless backhaul link to the intermediate IAB node 3b.
The allocation of scrambling identifiers within a network of IAB nodes can be performed such that duplicates are avoided, unless the number of possible identifiers is so large that the risk is virtually zero. This will be exemplified here in a pair of nodes denoted the upstream radio network node and an IAB node. The upstream radio network node is the one that provides the radio access for the backhaul communication for the IAB node. The pair can e.g. be the IAB donor node 3a being the upstream radio network node and the intermediate IAB node 3b being the IAB node. Alternatively, the pair can be the intermediate IAB node 3b being the upstream radio network node and the downstream IAB node 3c being the IAB node. In one embodiment, when an upstream radio network node allocates a scrambling identifier when an IAB node performs random access, the upstream radio network node might not be aware that the random access is from an IAB node. To avoid the risk of duplicates of scrambling identifiers within the network of IABs, the upstream radio network node can provide a list of all scrambling identifiers already allocated when the IAB node is brought into service. Thus, a potential new upstream radio network node can assign a unique scrambling identifier, as it knows its own scrambling identifier and all other scrambling identifiers in the network of IAB nodes.
Other schemes are possible, such as rule based (e.g. only allowed to allocate scrambling identifiers at a certain offset and range from your own scrambling identifiers). The scrambling identifiers can be allocated such that all IAB nodes have unique scrambling identifiers under a single IAB donor node. Alternatively, a scheme can be applied where some reuse of the scrambling identifiers is made possible, as long as the principles presented herein can be applied.
The memory 64 can be any combination of random-access memory (RAM) and/or read-only memory (ROM). The memory 64 also comprises persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid-state memory or even remotely mounted memory.
A data memory 66 is also provided for reading and/or storing data during execution of software instructions in the processor 6o. The data memory 66 can be any combination of RAM and/or ROM.
An I/O interface 62 is provided for communicating with external and/or internal entities. Optionally, the I/O interface 62 also includes a user interface.
Other components are omitted in order not to obscure the concepts presented herein.
A signal receiver 70 corresponds to step 4o. A downstream node determiner 74 corresponds to step 44. An IQ sample aligner 76 corresponds to step 46. A forwarder 78 corresponds to step 48. A full demodulator 80 corresponds to step 50. A feedback provider 82 corresponds to step 52.
A data receiver 170 corresponds to step 14o. A routing determiner 172 corresponds to step 142. A downstream signal generator 176 corresponds to step 146. A transmitter 178 corresponds to step 148.
The aspects of the present disclosure have mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims. Thus, while various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/SE2021/050242 | 3/18/2021 | WO |
