WO2022188153A1

WO2022188153A1 - Methods and apparatus of concurrent transmission of multicast broadcast service

Info

Publication number: WO2022188153A1
Application number: PCT/CN2021/080473
Authority: WO
Inventors: Xuelong Wang
Original assignee: Mediatek Singapore Pte. Ltd.
Priority date: 2021-03-12
Filing date: 2021-03-12
Publication date: 2022-09-15
Also published as: CN115086883A

Abstract

This disclosure describes methods and apparatus of supporting concurrent transmission of multicast broadcast services from the wireless network to the UEs. The core network indicates the correspondence of two or more MBS sessions or the QoS flows of the same MBS session that are subject to superposition based transmission at physical layer. The UE receives both core layer and enhancement layer. The SDAP entity of the UE combines the two different QoS flows before submitting the data to upper layer.

Description

METHODS AND APPARATUS OF CONCURRENT TRANSMISSION OF MULTICAST BROADCAST SERVICE

FIELD OF THE INVENTION

The present disclosure relates generally to communication systems, and more particularly, the method of enabling concurrent transmission of multicast broadcast services to support efficient multicast broadcast service delivery from the wireless network to the UEs.

BACKGROUND OF THE INVENTION

Various cellular systems, including both 4G/LTE and 5G/NR systems, may provide a multicast functionality, which allows user equipments (UEs) in the system to receive multicast services transported by the cellular system. A variety of applications may rely on communication over multicast transmission, such as live stream, video distribution, vehicle-to-everything (V2X) communication, public safety (PS) communication, file download, and so on. In some cases, there may be a need for the cellular system to enable concurrent multicast transmission in order to improve the spectrum utilization efficiency, since the available spectrum for multicast/broadcast services are transmitted over the air via layer division multiplexed manner, which was developed by Advanced Television System Committee.

SUMMARY OF THE INVENTION

The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

In an aspect of the disclosure, the core network indicate the correspondence of two or more MBS sessions or the QoS flows of the same MBS session that are subject to superposition based transmission at physical layer. Then the gNB allocates independent Radio Bearers to carry the packet streams from such QoS flows or MBS sessions. From scheduler perspective, the gNB ensures the bit alignment at MAC between the two packets streams before physical layer transmission in terms of MAC padding.

In another aspect of the disclosure, the UE receives both core layer and enhancement layer, the UE can combine the two packet streams and offer a combined view to the user. UE needs to remove the MAC padding from reception perspective before delivering the data to RLC layer. The SDAP entity of the UE needs to combine the two different QoS flows before submit the data to upper layer.

To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 (a) is a schematic system diagram illustrating an exemplary Base Station (i.e. BS) , in accordance with certain aspects of the present disclosure.

FIG. 1 (b) is a schematic system diagram illustrating an exemplary UE, in accordance with certain aspects of the present disclosure.

FIG. 2 illustrates an exemplary NR wireless communication system, in accordance with certain aspects of the present disclosure.

FIG. 3 illustrates an exemplary downlink superposition transmission at NR physical layer, in accordance with certain aspects of the present disclosure.

FIG. 4 illustrates an exemplary downlink high layer protocol stack mapping for two QoS flows of one MBS session, in accordance with certain aspects of the present disclosure.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

Several aspects of telecommunication systems will now be presented with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, components, circuits, processes, algorithms, etc. (collectively referred to as “elements” ) . These elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

Aspects of the present disclosure provide methods, apparatus, processing systems, and computer readable mediums for NR (new radio access technology, or 5G technology) or other radio access technology. NR may support various wireless communication services. These services may have different quality of service (QoS) requirements e.g. latency and reliability requirements. Figure 1 (a) is a schematic system diagram illustrating an exemplary Base Station (i.e. BS) . The BS may also be referred to as an access point, an access terminal, a base station, a Node-B, an eNode-B, a gNB, or by other terminology used in the art. As an example, base stations serve a number of mobile stations within a serving area, for example, a cell, or within a cell sector. The Base Station has an antenna, which transmits and receives radio signals. A RF transceiver, coupled with the antenna, receives RF signals from antenna, converts them to baseband signals, and sends them to processor. RF transceiver also converts received baseband signals from processor, converts them to RF signals, and sends out to antenna. Processor processes the received baseband signals and invokes different functions. Memory stores program instructions and data to control the operations of Base Station. Figure 1 (b) is a schematic system diagram illustrating an exemplary UE. The UE may also be referred to as a mobile station, a mobile terminal, a mobile phone, smart phone, wearable, an IoT device, a table let, a laptop, or other terminology used in the art. UE has an antenna, which transmits and receives radio signals. A RF transceiver, coupled with the antenna, receives RF signals from antenna, converts them to baseband signal, and sends them to processor. RF transceiver also converts received baseband signals from processor, converts them to RF signals, and sends out to antenna. Processor processes the received baseband signals and invokes different functional modules to perform features in UE. Memory stores program instructions and data to control the operations of mobile station. Figure 2 illustrates an exemplary NR wireless communication system. Different protocol split options between Central Unit and Distributed Unit of gNB nodes may be possible. In one embodiment, SDAP and PDCP layer are located in the central unit, while RLC, MAC and PHY layers are located in the distributed unit.

The described invention operates in the context of multicast/broadcast service (i.e. MBS) transmission in a cellular system. In certain systems, such as NR systems, NR multicast/broadcast is transmitted in the coverage of a cell. From network perspective, the base station provides the information of a list of NR multicast/broadcast services with ongoing sessions transmitted on MBS logical channels e.g. MTCH (s) . At physical layer, the data from the MBS logical channel is scheduled by gNB. UE decodes the MBS data according to its reception of the MBS logical channel.

In order to enable flexible usage of the limited spectrum for MBS services, from physical layer perspective, two or multiple data streams can be combined and coded together before actual OFDM modulation and its transmission over a single RF channel. As an example described in Figure 3, two independent data flows are created, one per each layer. A Downlink Shared Channel (DL-SCH) transport channel is generated for each layer, and then, the DL-SCH is encapsulated into PDSCH, where the modulation and the coding is applied. The coding size is adapted depending on the modulation and code rate that is used. Once PDSCH are generated for both layers, they are combined into a single NOMA signal ensemble. After superimposing both layers, the output constellation is normalized. Finally, the precoding matrix for the next transmission is calculated using singular value decomposition. Then, the OFDM signal is generated. In a typical implementation, these two data streams over two layers are subject to superposition with different transmission power.

In case of UHD and HD simulcast broadcast delivery, the left view and the right view of a stereoscopic 3D video component can be a UHD video and a HD video, respectively. There is no dependency between two views as two views are coded independently and decoded independently. That is, a receiver with normal channel quality can acquire HD right view video data from a physical channel and offers a HD service to the user. Another receiver with better channel quality can acquire UHD video data from a different physical channel and offers a UHD service to the user. Moreover, when a receiver can get data from two physical channels simultaneously, the receiver acquires an UHD left view and a HD right view video simultaneously and provides a 3D service by combining two views to the user.

By using layered based concurrent transmission (e.g. with the coding scheme of HEVC) , the HD right view can be coded in a base layer and the UHD left view can be coded through enhancement layer. For example, in Figure 3, DL SCH-1/PDSCH-1 can be used to transmit the base layer and DL SCH-2/PDSCH-2 can be used to deliver the enhancement layer. The DL SCH-1/PDSCH-1 (i.e. the base layer) is transmitted with high power and low-level modulation (e.g. QPSK) and coding scheme, which can be received by the UEs at both cell center and cell edge. The DL SCH-2/PDSCH-2 (i.e. the enhancement layer) is transmitted with low power and high-level modulation (e.g. 1024QAM) and coding scheme, which can be only received by the UEs at cell center, as the UEs at cell center have better radio signal quality. In this example, the cell edge users can receive the HD right view of the MBS service. The cell center receiver needs to acquire the 3D UHD view by using both the base and the enhancement layers from two physical channels and the receiver displays 3D service by combining two views.

As can be seen, one video stream can be coded by two different encoders that produce different packet streams (i.e. right view stream and left view stream) . When the parallel coding streams are transmitted via different physical channels subject to superposition transmission, synchronized transmission is required at the transmitter side to ensure the presentation of the picture for an instant sample of a particular video stream at the receiver side. The coding streams are produced at information source by application layer via specific codec. They will go across high layer protocol stack PDCP/RLC/MAC before its transmission over the channel at physical layer.

In legacy system, one MBS service corresponds to one MBS session. In this disclosure, the packet streams coded by two different encoders belongs to a unified MBS session (or PDU session) . As described in Figure 4, different QoS flows are used to express the packet streams coded by two different encoders and each QoS is expressed by one flow. In practice, for a particular video steam, right view can be expressed by one QoS flow, left view can be expressed by another QoS and the voice can be expressed by an additional QoS flow. Then in total it is three flows used to express such video stream. In Figure 4, only right view and left view are depicted and they are expressed by QoS flow-X and Flow-Y respectively. Alternatively, the packet streams coded by two different encoders of the same MBS service can belong to different MBS sessions.

From network perspective, during the MBS session establishment over N2 interface, the core network sends a message e.g. Multicast session establishment to the gNB. The message may include MBS related information and/or UE information. MBS related information includes MBS Session context ID, MBS group identity, and/or MBS flow information such as Multicast QoS Flow ID (s) and associating QoS information. One indicator can be introduced within the MBS flow information to indicate which QoS Flow can be subject to superposition transmission with which QoS Flow at physical layer (e.g. QoS flow-X and Flow-Y can be subject to superposition transmission at physical layer) .

Alternatively, one indicator can be introduced to express the association between two MBS sessions or among multiple MBS sessions to indicate which MBS session can be subject to superposition transmission at physical layer with which MBS session in case different MBS sessions are used to transmit the right view and left view of a single MBS service.

This indicator tells the gNB to perform corresponding handling at high layer protocol stack (i.e. SDAP/PDCP/RLC and MAC) and layer based transmission at physical layer. Accordingly, the gNB may send a RRC message e.g. RRC Reconfiguration to the UE to indicate such QoS flow and/or MBS session correspondence to the UE, in order to help the UE to associate the corresponding QoS Flows or MBS sessions at the receiver before delivery to upper layer.

Alternatively, a cross layer signaling is used from transport layer (e.g. UDP) and/or application layer (e.g. RTP) to high layer (SDAP, PDCP and/or RLC) to indicate that QoS flow-X and Flow-Y corresponds to right view and left view and to indicate that these two QoS flows can be subject to layer based multiplexing before radio transmission over the air.

In Figure 4, the SDAP layer of high layer protocol stack at network side allocates two independent MBS Radio Bearers (i.e. Multicast/Broadcast RB-1 and Multicast/Broadcast RB-2) with independent PDCP entity in order to split the data streams between the QoS flow-X and Flow-Y, corresponding to right view and left view of the same MBS session respectively. Special handling required at MAC layer of the network side is to avoid multiplexing data coming from QoS flow-X together with data coming from Flow-Y, even though both data streams are serving the same MBS session or serving the same MBS services. The aim is to produce two consistent MAC PDUs, each corresponding to an independent Transport Block that is transmitted by a superposition layer at physical layer (e.g. core layer or enhancement layer) .

Although the data flows of core layer transmitting right view and enhancement layer transmitting left view are independently configured, a joint bit alignment is needed, which puts a restriction on the size of the two transport blocks. In order to achieving concurrent transmission of the data streams coming from QoS Flow-X and QoS Flow-Y, MAC padding may be used to meet the TB size required by physical layer. E.g. if QoS Flow-X (representing right view) has not sufficient bits to transmit, MAC padding can be adopted to produce the corresponding bit size before generating the MAC-PDU for core layer. Typically, the core layer and enhancement layer adopted different Modulation and Coding Scheme (i.e. MCS) and then the enhancement layer can carry more bits than core layer. Accordingly, the packet stream of left view (which is UHD) has more bits to transmit than the packet stream of right view (which is HD) . However in reality it may not match that well.

For example, if the enhancement layer has A bits to transmit for one video frame but the corresponding PDSCH can carry B bits, where A<B. The amount of (A minus B) MAC padding bit can be used at the MAC PDU before generating the Transport Block. The same principle can apply to core layer.

From superposition transmission perspective, there is a requirement for the bit alignment between core layer and enhancement layer. For example, it can assume the transmission bits for one superposition transmission interval is S. Assuming that there is a factor of MCS for core layer and enhancement layer are F1 and F2 respectively and assuming that the desired size of the transport blocks for core layer and enhancement layer are A1 and A2 respectively, then F1*A1 =F2*A2=S. If for a particular video frame, the MAC PDU of the core layer and enhancement layer is less than A1 and A2, one transport block for each layer should be used for such superposition transmission, each with different amount of MAC padding. If for a particular video frame, the MAC PDU of the core layer and enhancement layer is larger than A1 and A2, two or more transport blocks should be used for such superposition transmission. If for a particular video frame, one layer’s MAC PDU cannot be transmitted by one transport block but the other one can be transmitted by one transport block, multiple transmission interval based superposition transmission should be used. In this case, other than the first superposition transmission, the layer that has a small MAC PDU may use a full MAC padding bits to assist the superposition transmission.

In this disclosure, the UE receives both core layer and enhancement layer, the UE can combine the two packet streams and offer a combined view to the user. UE needs to remove the MAC padding from reception perspective before delivering the data to RLC layer. A MAC padding indicator should be used by the network to indicate to the UE the amount of the MAC padding bits. The location of the padding bits should be fixed e.g. at the rear of the MAC PDU.

In this disclosure, from the UE reception perspective, its SDAP entity needs to combine the two different QoS flows before submit the data to upper layer. In order to direct the UE to do so, network can indicate such correspondence via a field within SDAP packet, or via control PDU, or via RRC message.

The abovementioned handling can be also applicable to the concurrent layer based transmission for two or more MBS services. In this case, core layer is used to deliver the basic MBS service, and the enhancement layer is used to deliver the other MBS services. For example, CCTV has multiple program channels (from CCTV1 to CCTV14) , CCTV1 can be transmitted at the core layer targeting all users, and CCTV2-CCTV14 can delivered at enhancement layer targeting the cell center users only, who has better radio signal quality. However all of these channels are concurrently transmitted from the perspective network, in order to ensure UE synchronized reception of all these TV channels.

The abovementioned handling can be also applicable to the concurrent layer based transmission between unicast service and one or more MBS services. In this case, core layer is used to deliver the MBS service (s) , and the enhancement layer is used to deliver the unicast service to a specific user. In this case, different users may decode different services. For example, some users that are only interested in MBS service just receive the core layer. The unicast user only receive the enhancement layer to receive the unicast service.

It is understood that the specific order or hierarchy of blocks in the processes /flowcharts disclosed is an illustration of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of blocks in the processes /flowcharts may be rearranged. Further, some blocks may be combined or omitted. The accompanying method claims present elements of the various blocks in a sample order, and are not meant to be limited to the specific order or hierarchy presented.

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more. ” The word “exemplary” is used herein to mean “serving as an example, instance, or illustration. ” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects. Unless specifically stated otherwise, the term “some” refers to one or more. Combinations such as “at least one of A, B, or C, ” “one or more of A, B, or C, ” “at least one of A, B, and C, ” “one or more of A, B, and C, ” and “A, B, C, or any combination thereof” include any combination of A, B, and/or C, and may include multiples of A, multiples of B, or multiples of C. Specifically, combinations such as “at least one of A, B, or C, ” “one or more of A, B, or C, ” “at least one of A, B, and C, ” “one or more of A, B, and C, ” and “A, B, C, or any combination thereof” may be A only, B only, C only, A and B, A and C, B and C, or A and B and C, where any such combinations may contain one or more member or members of A, B, or C. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. The words “module, ” “mechanism, ” “element, ” “device, ” and the like may not be a substitute for the word “means. ” As such, no claim element is to be construed as a means plus function unless the element is expressly recited using the phrase “means for. ”

While aspects of the present disclosure have been described in conjunction with the specific embodiments thereof that are proposed as examples, alternatives, modifications, and variations to the examples may be made. Accordingly, embodiments as set forth herein are intended to be illustrative and not limiting. There are changes that may be made without departing from the scope of the claims set forth below.

Claims

A method of wireless communication comprising:

Concurrent transmission of multicast broadcast service from gNB to the UE.
The method of claim 1, wherein the gNB is indicated by core network with the correspondence of two or more MBS sessions or the QoS flows of the same MBS session that are subject to superposition based transmission at physical layer.
The method of claim 1, wherein the gNB ensures the bit alignment at MAC between the two packets streams before physical layer transmission in terms of MAC padding.
The method of claim 1, wherein the UE removes the MAC padding from reception perspective before delivering the data to RLC layer.
The method of claim 1, wherein the UE combines the two different QoS flows at SDAP layer before submitting the data to upper layer.