EP4695913A1

EP4695913A1 - Systems and methods for channel precoding for distributed multiple-input-multiple-output (mimo)

Info

Publication number: EP4695913A1
Application number: EP23936158.7A
Authority: EP
Inventors: Ning Wei
Original assignee: ZTE Corp
Current assignee: ZTE Corp
Priority date: 2023-05-11
Filing date: 2023-05-11
Publication date: 2026-02-18
Also published as: CN121285962A; WO2024229843A1

Abstract

Presented are systems and methods for channel precoding for distributed Multiple-Input-Multiple-Output (MIMO). A first one of a first one of a plurality of wireless communication nodes that are communicatively coupled to a network node may identify a channel space. The channel space can be formed by channel response vectors from the first wireless communication node to a plurality of wireless communication devices. The first wireless communication node may derive a common space from the channel space. The first wireless communication node may determine, according to a difference between the common space and the channel space, an individual space for precoding a downlink (DL) transmission per each of the plurality of wireless communication devices.

Description

SYSTEMS AND METHODS FOR CHANNEL PRECODING FOR DISTRIBUTED MULTIPLE-INPUT-MULTIPLE-OUTPUT (MIMO)

TECHNICAL FIELD

The disclosure relates generally to wireless communications, including but not limited to systems and methods for channel precoding for distributed Multiple-Input-Multiple-Output (MIMO) .

BACKGROUND

The standardization organization Third Generation Partnership Project (3GPP) is currently in the process of specifying a new Radio Interface called 5G New Radio (5G NR) as well as a Next Generation Packet Core Network (NG-CN or NGC) . The 5G NR will have three main components: a 5G Access Network (5G-AN) , a 5G Core Network (5GC) , and a User Equipment (UE) . In order to facilitate the enablement of different data services and requirements, the elements of the 5GC, also called Network Functions, have been simplified with some of them being software based, and some being hardware based, so that they could be adapted according to need.

SUMMARY

The example embodiments disclosed herein are directed to solving the issues relating to one or more of the problems presented in the prior art, as well as providing additional features that will become readily apparent by reference to the following detailed description when taken in conjunction with the accompany drawings. In accordance with various embodiments, example systems, methods, devices and computer program products are disclosed herein. It is understood, however, that these embodiments are presented by way of example and are not limiting, and it will be apparent to those of ordinary skill in the art who read the present disclosure that various modifications to the disclosed embodiments can be made while remaining within the scope of this disclosure.
At least one aspect is directed to a system, method, apparatus, or a computer-readable medium of the following. A first one of a first one of a plurality of wireless communication nodes (e.g., access points (APs) ) that are communicatively coupled to a network node (e.g., a central processing unit (CPU) ) may identify a channel space. The channel space can be formed by channel response vectors from the first wireless communication node (e.g., APm) to a plurality of wireless communication devices (e.g., user equipments (UEs) ) . The first wireless communication node may derive a common space from the channel space. The first wireless communication node may determine, according to a difference between the common space and the channel space, an individual space for precoding a downlink (DL) transmission per each of the plurality of wireless communication devices.
In some embodiments, the first wireless communication node may derive the common space based on measured channel responses between the first wireless communication node and the plurality of wireless communication devices. The first wireless communication node may calculate a first parameter based on the common space. The first wireless communication node may send the first parameter to the network node. The first wireless communication node may receive a second parameter from the network node. The individual space can be determined based on the second parameter, the common space, and the channel space.
In some embodiments, the first wireless communication node may determine an anchor one of the plurality of wireless communication devices. The first wireless communication node may derive the common space based on measuring channel responses between the first wireless communication node and the anchor wireless communication device. The first wireless communication node may send the first parameter. The plurality of wireless communication nodes can be not communicatively coupled to each other.
In some embodiments, the first wireless communication node may derive the common space based on measured channel responses between the first wireless communication node and the plurality of wireless communication devices. The first wireless communication node may calculate a first parameter based on the common space. The first wireless communication node may send the first parameter to a second one of the plurality of wireless communication nodes. The first wireless communication node may receive a second parameter from a last one of the plurality of wireless communication nodes. The individual space can be determined based on the second parameter, the common space, and the channel space.
In some embodiments, the first wireless communication node may determine an anchor one of the plurality of wireless communication devices. The first wireless communication node may derive the common space based on measuring channel responses between the first wireless communication node and the anchor wireless communication device. The first wireless communication node may send the first parameter to a second one of the plurality of wireless communication nodes. Each of the plurality of wireless communication nodes can be configured to receive the first parameter (e.g., α_m) from a preceding one of the plurality of wireless communication nodes. α_M can be a second parameter shared by all AP nodes. The difference between α_M and α_m can be that α_m is used for indicating the first parameter calculated at the mth AP, wherein 1≤m<M. The plurality of wireless communication nodes can be communicatively coupled to one another unidirectionally or bidirectionally.
In some embodiments, the first wireless communication node may derive the common space based on measuring channel responses between the first wireless communication node and the plurality of wireless communication devices. The first wireless communication node may calculate a first parameter based on the common space. The first wireless communication node may send the first parameter to second one of the plurality of wireless communication nodes. The first wireless communication node may receive a second parameter from the network node. The individual space can be determined based on the second parameter, the common space, and the channel space.
In some embodiments, the first parameter can be a component of a global normalization factor for all the wireless communication nodes. The first parameter can be a user identification of the anchor wireless communication device. The first and second wireless communication nodes may belong to one of a plurality of subsets of the plurality of wireless communication nodes. The subsets of wireless communication nodes can be not communicatively coupled to each other.

BRIEF DESCRIPTION OF THE DRAWINGS

Various example embodiments of the present solution are described in detail below with reference to the following figures or drawings. The drawings are provided for purposes of illustration only and merely depict example embodiments of the present solution to facilitate the reader's understanding of the present solution. Therefore, the drawings should not be considered limiting of the breadth, scope, or applicability of the present solution. It should be noted that for clarity and ease of illustration, these drawings are not necessarily drawn to scale.
FIG. 1 illustrates an example cellular communication network in which techniques disclosed herein may be implemented, in accordance with an embodiment of the present disclosure;
FIG. 2 illustrates a block diagram of an example base station and a user equipment device, in accordance with some embodiments of the present disclosure;
FIG. 3 illustrates a block diagram of an example of channel responses for UEs in Cell-Free Multiple-Input-Multiple-Output (MIMO) network, in accordance with some embodiments of the present disclosure;
FIG. 4 illustrates a flow chart for channel precoding, in accordance with some embodiments of the present disclosure;
FIG. 5 illustrates a block diagram of an example network diagram Type I, in accordance with some embodiments of the present disclosure;
FIG. 6 illustrates a block diagram of an example network diagram Type II, in accordance with some embodiments of the present disclosure;
FIG. 7 illustrates a block diagram of an example network diagram Type III, in accordance with some embodiments of the present disclosure; and
FIG. 8 illustrates a flow diagram for channel precoding for distributed Multiple-Input-Multiple-Output (MIMO) , in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

1. Mobile Communication Technology and Environment
FIG. 1 illustrates an example wireless communication network, and/or system, 100 in which techniques disclosed herein may be implemented, in accordance with an embodiment of the present disclosure. In the following discussion, the wireless communication network 100 may be any wireless network, such as a cellular network or a narrowband Internet of things (NB-IoT) network, and is herein referred to as “network 100. ” Such an example network 100 includes a base station 102 (hereinafter “BS 102” ; also referred to as wireless communication node) and a user equipment device 104 (hereinafter “UE 104” ; also referred to as wireless communication device) that can communicate with each other via a communication link 110 (e.g., a wireless communication channel) , and a cluster of cells 126, 130, 132, 134, 136, 138 and 140 overlaying a geographical area 101. In Figure 1, the BS 102 and UE 104 are contained within a respective geographic boundary of cell 126. Each of the other cells 130, 132, 134, 136, 138 and 140 may include at least one base station operating at its allocated bandwidth to provide adequate radio coverage to its intended users.
For example, the BS 102 may operate at an allocated channel transmission bandwidth to provide adequate coverage to the UE 104. The BS 102 and the UE 104 may communicate via a downlink radio frame 118, and an uplink radio frame 124 respectively. Each radio frame 118/124 may be further divided into sub-frames 120/127 which may include data symbols 122/128. In the present disclosure, the BS 102 and UE 104 are described herein as non-limiting examples of “communication nodes, ” generally, which can practice the methods disclosed herein. Such communication nodes may be capable of wireless and/or wired communications, in accordance with various embodiments of the present solution.
FIG. 2 illustrates a block diagram of an example wireless communication system 200 for transmitting and receiving wireless communication signals (e.g., OFDM/OFDMA signals) in accordance with some embodiments of the present solution. The system 200 may include components and elements configured to support known or conventional operating features that need not be described in detail herein. In one illustrative embodiment, system 200 can be used to communicate (e.g., transmit and receive) data symbols in a wireless communication environment such as the wireless communication environment 100 of Figure 1, as described above.
System 200 generally includes a base station 202 (hereinafter “BS 202” ) and a user equipment device 204 (hereinafter “UE 204” ) . The BS 202 includes a BS (base station) transceiver module 210, a BS antenna 212, a BS processor module 214, a BS memory module 216, and a network communication module 218, each module being coupled and interconnected with one another as necessary via a data communication bus 220. The UE 204 includes a UE (user equipment) transceiver module 230, a UE antenna 232, a UE memory module 234, and a UE processor module 236, each module being coupled and interconnected with one another as necessary via a data communication bus 240. The BS 202 communicates with the UE 204 via a communication channel 250, which can be any wireless channel or other medium suitable for transmission of data as described herein.
As would be understood by persons of ordinary skill in the art, system 200 may further include any number of modules other than the modules shown in Figure 2. Those skilled in the art will understand that the various illustrative blocks, modules, circuits, and processing logic described in connection with the embodiments disclosed herein may be implemented in hardware, computer-readable software, firmware, or any practical combination thereof. To clearly illustrate this interchangeability and compatibility of hardware, firmware, and software, various illustrative components, blocks, modules, circuits, and steps are described generally in terms of their functionality. Whether such functionality is implemented as hardware, firmware, or software can depend upon the particular application and design constraints imposed on the overall system. Those familiar with the concepts described herein may implement such functionality in a suitable manner for each particular application, but such implementation decisions should not be interpreted as limiting the scope of the present disclosure.
In accordance with some embodiments, the UE transceiver 230 may be referred to herein as an "uplink" transceiver 230 that includes a radio frequency (RF) transmitter and a RF receiver each comprising circuitry that is coupled to the antenna 232. A duplex switch (not shown) may alternatively couple the uplink transmitter or receiver to the uplink antenna in time duplex fashion. Similarly, in accordance with some embodiments, the BS transceiver 210 may be referred to herein as a "downlink" transceiver 210 that includes a RF transmitter and a RF receiver each comprising circuity that is coupled to the antenna 212. A downlink duplex switch may alternatively couple the downlink transmitter or receiver to the downlink antenna 212 in time duplex fashion. The operations of the two transceiver modules 210 and 230 may be coordinated in time such that the uplink receiver circuitry is coupled to the uplink antenna 232 for reception of transmissions over the wireless transmission link 250 at the same time that the downlink transmitter is coupled to the downlink antenna 212. Conversely, the operations of the two transceivers 210 and 230 may be coordinated in time such that the downlink receiver is coupled to the downlink antenna 212 for reception of transmissions over the wireless transmission link 250 at the same time that the uplink transmitter is coupled to the uplink antenna 232. In some embodiments, there is close time synchronization with a minimal guard time between changes in duplex direction.
The UE transceiver 230 and the base station transceiver 210 are configured to communicate via the wireless data communication link 250, and cooperate with a suitably configured RF antenna arrangement 212/232 that can support a particular wireless communication protocol and modulation scheme. In some illustrative embodiments, the UE transceiver 210 and the base station transceiver 210 are configured to support industry standards such as the Long Term Evolution (LTE) and emerging 5G standards, and the like. It is understood, however, that the present disclosure is not necessarily limited in application to a particular standard and associated protocols. Rather, the UE transceiver 230 and the base station transceiver 210 may be configured to support alternate, or additional, wireless data communication protocols, including future standards or variations thereof.
In accordance with various embodiments, the BS 202 may be an evolved node B (eNB) , a serving eNB, a target eNB, a femto station, or a pico station, for example. In some embodiments, the UE 204 may be embodied in various types of user devices such as a mobile phone, a smart phone, a personal digital assistant (PDA) , tablet, laptop computer, wearable computing device, etc. The processor modules 214 and 236 may be implemented, or realized, with a general purpose processor, a content addressable memory, a digital signal processor, an application specific integrated circuit, a field programmable gate array, any suitable programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof, designed to perform the functions described herein. In this manner, a processor may be realized as a microprocessor, a controller, a microcontroller, a state machine, or the like. A processor may also be implemented as a combination of computing devices, e.g., a combination of a digital signal processor and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a digital signal processor core, or any other such configuration.
Furthermore, the steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in firmware, in a software module executed by processor modules 214 and 236, respectively, or in any practical combination thereof. The memory modules 216 and 234 may be realized as RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. In this regard, memory modules 216 and 234 may be coupled to the processor modules 210 and 230, respectively, such that the processors modules 210 and 230 can read information from, and write information to, memory modules 216 and 234, respectively. The memory modules 216 and 234 may also be integrated into their respective processor modules 210 and 230. In some embodiments, the memory modules 216 and 234 may each include a cache memory for storing temporary variables or other intermediate information during execution of instructions to be executed by processor modules 210 and 230, respectively. Memory modules 216 and 234 may also each include non-volatile memory for storing instructions to be executed by the processor modules 210 and 230, respectively.
The network communication module 218 generally represents the hardware, software, firmware, processing logic, and/or other components of the base station 202 that enable bi-directional communication between base station transceiver 210 and other network components and communication nodes configured to communication with the base station 202. For example, network communication module 218 may be configured to support internet or WiMAX traffic. In a typical deployment, without limitation, network communication module 218 provides an 802.3 Ethernet interface such that base station transceiver 210 can communicate with a conventional Ethernet based computer network. In this manner, the network communication module 218 may include a physical interface for connection to the computer network (e.g., Mobile Switching Center (MSC) ) . The terms “configured for, ” “configured to” and conjugations thereof, as used herein with respect to a specified operation or function, refer to a device, component, circuit, structure, machine, signal, etc., that is physically constructed, programmed, formatted and/or arranged to perform the specified operation or function.
The Open Systems Interconnection (OSI) Model (referred to herein as, “open system interconnection model” ) is a conceptual and logical layout that defines network communication used by systems (e.g., wireless communication device, wireless communication node) open to interconnection and communication with other systems. The model is broken into seven subcomponents, or layers, each of which represents a conceptual collection of services provided to the layers above and below it. The OSI Model also defines a logical network and effectively describes computer packet transfer by using different layer protocols. The OSI Model may also be referred to as the seven-layer OSI Model or the seven-layer model. In some embodiments, a first layer may be a physical layer. In some embodiments, a second layer may be a Medium Access Control (MAC) layer. In some embodiments, a third layer may be a Radio Link Control (RLC) layer. In some embodiments, a fourth layer may be a Packet Data Convergence Protocol (PDCP) layer. In some embodiments, a fifth layer may be a Radio Resource Control (RRC) layer. In some embodiments, a sixth layer may be a Non Access Stratum (NAS) layer or an Internet Protocol (IP) layer, and the seventh layer being the other layer.
Various example embodiments of the present solution are described below with reference to the accompanying figures to enable a person of ordinary skill in the art to make and use the present solution. As would be apparent to those of ordinary skill in the art, after reading the present disclosure, various changes or modifications to the examples described herein can be made without departing from the scope of the present solution. Thus, the present solution is not limited to the example embodiments and applications described and illustrated herein. Additionally, the specific order or hierarchy of steps in the methods disclosed herein are merely example approaches. Based upon design preferences, the specific order or hierarchy of steps of the disclosed methods or processes can be re-arranged while remaining within the scope of the present solution. Thus, those of ordinary skill in the art will understand that the methods and techniques disclosed herein present various steps or acts in a sample order, and the present solution is not limited to the specific order or hierarchy presented unless expressly stated otherwise.
2. Systems and Methods for Channel Precoding for Distributed Multiple-Input-Multiple- Output (MIMO)
In the context of distributed massive Multiple-Input-Multiple-Output (MIMO) systems, there is a need for a method that enables efficient distributed channel precoding with minimal exchange of information and computational complexity. Cell-Free MIMO, known as a canonical distributed MIMO technology, is being discussed to develop a vision of ubiquitous data service to each accessible user. A prominent characteristic of Cell-Free MIMO at physical layer can be channel precoding-based coherent transmission. Closely similar to centralized MIMO systems, coherent transmission can be inherently with a capability of providing a large quantities of macro-diversity gains by softly programming electromagnetic signal propagation. In terms of optimal precoding, the underlying assumption for distributed MIMO can be that global channel state information (CSI) is available for each BS/access point (AP) for boosting quality interference mitigation among UEs. On the other hand, making a global CSI depends on ample information exchange which is nearly impossible when taking account of practical requirements of latency and overhead. In this context, a distributed precoding scheme featured in extremely low information-exchange burden and computation complexity can be considered for Cell-Free MIMO. To address this problem, conjugate precoding (e.g., maximal ratio transmission (MRT) ) for distributed massive MIMO system can be performed. Specifically, advantages of conjugate precoding can be: (a) theoretically, the conjugate precoding may need no information exchange; (b) computation complexity of the conjugate precoding. Nevertheless, the challenge is that if channel responses of UEs are correlated, it can be fairly difficult for conjugate precoding to manage UE-to-UE interference, at least partially destroying orthogonality among channel responses. In present disclosure, an investigation of distributed conjugate precoding is to leverage differences between channel responses instead of directly utilizing complete channel responses. FIG. 3 illustrates a block diagram of an example of channel responses for UEs in Cell-Free Multiple-Input-Multiple-Output (MIMO) network, in accordance with some embodiments of the present disclosure.
The precoding solution in present disclosure is that AP node may explicitly derive a common space from channel (response) spaces for a plurality of UEs and in term of differences between the common space and channel spaces, may determine a certain number of precoding vectors of transforming channel space into an individual space for DL transmission. In some embodiments, a channel space is a linear combination of common space and individual space. In some embodiments, constraints imposed on the common and individual space are : (1) the common space is orthogonal to individual spaces for a plurality of UEs; and (2) individual spaces for UEs are mutually orthogonal. FIG. 4 illustrates a flow chart for channel precoding, in accordance with some embodiments of the present disclosure.
FIG. 5 illustrates a block diagram of an example network diagram Type I (scenario-A) , in accordance with some embodiments of the present disclosure. In FIG. 5, a central processing unit (CPU) (e.g., center control node/device) can be a function module of information control and collection, and cables (or wireless links) can be considered for connecting CPU module with AP nodes. According to pilots of reference signal of a received uplink (UL) wireless frame, AP_m (1≤m≤M) node may derive a common (channel) space from channel spaces spanned by channel response vectors from different UEs, may estimate a first parameter based on the common channel space, and may send the first parameter to CPU. As a response, CPU module may calculate a second parameter in accordance with received first parameters and may correspondingly broadcast the second parameter to target AP nodes. When a second parameter is received, AP_mnode may adjust the local common space for forming a global common space (e.g., one of feasible approaches to adjusting the local common space is to normalize the common space by a scale factor from the second parameter) . An individual (channel) space can be determined if following a principle that a linear combination of the individual channel space and common channel space spans the channel space. A downlink (DL) signal transmission precoded by the individual space (or its variants) can be performed per UE and relevant implementation examples are provided as below.
Implementation Example A
An AP node may measure a channel response H between the AP node and a UE through received reference signals in a wireless frame. Optionally, an expression for a common space can be m, k and d may denote indices of the UE, AP node and spatial dimension (e.g., the number of antennas/ports/layers) of the UE, respectively. Supposing thatis a known quantity, AP_m node may deliver α_m (e.g., a norm of) to the CPU. Providing that l₂_norm is selected, the CPU may attain a scale factor written in notationand may send β_CPUto AP nodes. After removing the component regarding a common space normalized by β_CPU, AP_mnode can find (e.g., individual space) of H_m, _k, _d of UE_kand may perform a DL transmission precoded by
Implementation Example B
The discrepancy between implementation example A and implementation example B is the manner of determining a common space. Instead of information exchange for seeking a common space occurred in implementation example A, CPU module in implementation example B may assign UE_λ as an anchor, implicitly mandating that a common space is
Accordingly, a mathematical expression of the parameter α_m can be given by where norm (·) is a norm operator herein. Furthermore, CPU may inform AP nodes of index λ of anchor UE before parameter α_mis reported.
FIG. 6 illustrates a block diagram of an example network diagram Type II (scenario-B) , in accordance with some embodiments of the present disclosure.
Similar to FIG. 6, assume that a plurality of AP nodes are concatenated into a distributed network, which is conditioned by sequential information exchange between AP nodes. Similar to preceding implementations, AP_m (1≤m＜M) node may search for a common channel space embedding in channel space, may perform an estimation on a first parameter based on the common space, and may transmit a third parameter to next neighbour AP node (e.g., AP_m+1) . If without a third parameter from neighbor node, a third parameter for AP_mnode can be a variable about the first parameter. Otherwise, a third parameter for AP_mnode can be equal to a sum of a third parameter from neighbor node (e.g., AP_m-1) and a variable about the first parameter. When the current node is a final AP node (e.g., AP_M) , a third parameter can be inversely passed to its neighbour node (e.g., AP_M-1) . This procedure can also be followed by other AP nodes for enabling that a third parameter from AP_Mnode is a global variable. Using a scale factor that is usually a function of the third parameter, AP node may make a normalization to the common channel space and may seek an individual space under the constraint that channel space is a linear combination of the normalized common and individual channel spaces. AP node may perform the precoding of DL signal based on the individual space and may transmit the precoded DL signal to every target UE. Several implementation examples are described.
Implementation Example C
While estimating channel response H_1, _k, a starting AP node (e.g., AP₁) may obtain a common space, and may deliverto AP₂. Similarly, AP_m (m>1) node may proceed to deliver α_m to a next neighbor AP node. A selection for α_m can be whereis a common channel space of AP_mnode and can be written as
If parameter α_Mis derived, a final AP (e.gAP_M) may commence relaying α_Mto AP_M-1.
Likewise, AP_m (1<m<M) may relay α_Mto AP_m-1. Furthermore, if an unidirectional stripe in FIG. 6 (a) is considered as the topology for AP deployment, AP_Mmay pass α_Mto AP₁ and AP₁may transmit α_Mand an ID indication to AP₂, where the ID indication is a signaling of identifying the parameter α_M. In such way, α_Mcan be sequentially delivered to each AP_mnode. If the layout of network diagram is a bidirectional strip as FIG. 6 (b) shows, parameter α_Mmay be passed from AP_Mto AP_M-1, from AP_M-1to AP_M-2, . . ., and from AP₂ to AP₁. Whichever network diagram is assumed, α_Mcan be relayed to all of AP nodes without changes. After a component regarding a common space normalized by β_CPUis removed, AP_m can find a corresponding individual spaceof H_m, _k, _dfor UE_kand may perform a DL transmission precoded by
Implementation Example D
A space comprised of channel response H_m, _λ of anchor UE_λcan be approximated as a common channel space in this implementation. Moreover, anchor UE can be predetermined and optionally can be assigned by a CPU. As a consequence, α_m is reformulated as whereIn addition, a substitute for H_m, _λmay be one or more codewords in a predetermined codebook (e.g., a number of bases in a predetermined space) .
FIG. 7 illustrates a block diagram of an example network diagram Type III (scenario-C) , in accordance with some embodiments of the present disclosure. Network diagram Type III is a combination/fusion of network diagram Type I and network diagram Type II. FIG. 7 illustrates that a plurality of AP stripes are connected to CPU and the number of AP for each stripe is independent.
AP_m, _p (1≤m≤M, 1≤p≤N_m) may calculate a first parameter according to a common space for channel spaces. Subsequently, a second parameter can be transmitted by AP_m, _pto AP_m, _p-1. If without a third parameter from neighbor node, a third parameter for AP_m, _pnode can be configured into a variable about the first parameter. Otherwise, a third parameter for AP_m, _pnode can be a sum of a third parameter from AP_m, _p-1node and a variable about the first parameter. During central processing, a CPU may merge all of third parameters into a second parameter and may forward the second parameter to respective AP stripes. The common channel space can be multiplied by a scale factor for space basis normalization and an individual channel space can be obtained considering the relation that channel space is a linear combination of a common channel space and an individual channel space. Based on precodes generated by an individual space, AP_m, _pnode may implement a precoded DL transmission to every target UE.
Implementation Example E
By channel responses from AP_mto UEs, may estimate a common channel space and may sendtowhereis represented as
When α_m, _p+1 is received, AP_m, _p (1≤p＜N_m) may calculate the parameter α_m, _p and may send α_m, _pto AP_m, _p-1node. In the particular case p=1, the underlying receiver of α_m, _p can be CPU. Accordingly, a CPU module can be responsible for estimating parameter α_CPUin the formula as followsand may distribute α_CPUto each AP_m, ₁. The reception of α_CPUmay trigger that AP_m, _pproceeds with parameter passing, e.g., transmitting α_CPUfrom AP_m, _pto AP_m, _p+1, and may terminate the parameter passing procedure if p=N_m. AP_m, _p may find a normalized common channel spaceby multiplyingby α_CPUand correspondingly based onnamed an individual space of H_m, _p, _k, can also be found under the condition thatandare orthogonal. Precoding transmission can be performed by AP_m, _pnode when an individual space is available.
It should be understood that one or more features from the above implementation examples are not exclusive to the specific implementation examples, but can be combined in any manner (e.g., in any priority and/or order, concurrently or otherwise) .
FIG. 8 illustrates a flow diagram of a method 800 for channel precoding for distributed Multiple-Input-Multiple-Output (MIMO) . The method 800 may be implemented using any one or more of the components and devices detailed herein in conjunction with FIGs. 1–2. In overview, the method 800 may be performed by a wireless communication node, in some embodiments. Additional, fewer, or different operations may be performed in the method 800 depending on the embodiment. At least one aspect of the operations is directed to a system, method, apparatus, or a computer-readable medium.
A first one of a first one of a plurality of wireless communication nodes (e.g., access points (APs) ) that are communicatively coupled to a network node (e.g., a central processing unit (CPU) ) may identify a channel space. The channel space can be formed by channel response vectors from the first wireless communication node (e.g., APm) to a plurality of wireless communication devices (e.g., user equipments (UEs) ) . The first wireless communication node may derive a common space from the channel space. The first wireless communication node may determine, according to a difference between the common space and the channel space, an individual space for precoding a downlink (DL) transmission per each of the plurality of wireless communication devices.
In some embodiments, the first wireless communication node may derive the common space based on measured channel responses between the first wireless communication node and the plurality of wireless communication devices. The first wireless communication node may calculate a first parameter based on the common space. The first wireless communication node may send the first parameter to the network node. The first wireless communication node may receive a second parameter from the network node. The individual space can be determined based on the second parameter, the common space, and the channel space.
In some embodiments, the first wireless communication node may determine an anchor one of the plurality of wireless communication devices. The first wireless communication node may derive the common space based on measuring channel responses between the first wireless communication node and the anchor wireless communication device. The first wireless communication node may send the first parameter. The plurality of wireless communication nodes can be not communicatively coupled to each other.
In some embodiments, the first wireless communication node may derive the common space based on measured channel responses between the first wireless communication node and the plurality of wireless communication devices. The first wireless communication node may calculate a first parameter based on the common space. The first wireless communication node may send the first parameter to a second one of the plurality of wireless communication nodes. The first wireless communication node may receive a second parameter from a last one of the plurality of wireless communication nodes. The individual space can be determined based on the second parameter, the common space, and the channel space.
In some embodiments, the first wireless communication node may determine an anchor one of the plurality of wireless communication devices. The first wireless communication node may derive the common space based on measuring channel responses between the first wireless communication node and the anchor wireless communication device. The first wireless communication node may send the first parameter to a second one of the plurality of wireless communication nodes. Each of the plurality of wireless communication nodes can be configured to receive the first parameter (e.g., α_m) from a preceding one of the plurality of wireless communication nodes. α_M can be a second parameter shared by all AP nodes. The difference between _αM and α_m can be that α_m is used for indicating the first parameter calculated at the mth AP, wherein 1≤m<M. The plurality of wireless communication nodes can be communicatively coupled to one another unidirectionally or bidirectionally.
In some embodiments, the first wireless communication node may derive the common space based on measuring channel responses between the first wireless communication node and the plurality of wireless communication devices. The first wireless communication node may calculate a first parameter based on the common space. The first wireless communication node may send the first parameter to second one of the plurality of wireless communication nodes. The first wireless communication node may receive a second parameter from the network node. The individual space can be determined based on the second parameter, the common space, and the channel space.
In some embodiments, the first parameter can be a component of a global normalization factor for all the wireless communication nodes. The first parameter can be a user identification of the anchor wireless communication device. The first and second wireless communication nodes may belong to one of a plurality of subsets of the plurality of wireless communication nodes. The subsets of wireless communication nodes can be not communicatively coupled to each other.
While various embodiments of the present solution have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. Likewise, the various diagrams may depict an example architectural or configuration, which are provided to enable persons of ordinary skill in the art to understand example features and functions of the present solution. Such persons would understand, however, that the solution is not restricted to the illustrated example architectures or configurations, but can be implemented using a variety of alternative architectures and configurations. Additionally, as would be understood by persons of ordinary skill in the art, one or more features of one embodiment can be combined with one or more features of another embodiment described herein. Thus, the breadth and scope of the present disclosure should not be limited by any of the above-described illustrative embodiments.
It is also understood that any reference to an element herein using a designation such as "first, " "second, " and so forth does not generally limit the quantity or order of those elements. Rather, these designations can be used herein as a convenient means of distinguishing between two or more elements or instances of an element. Thus, a reference to first and second elements does not mean that only two elements can be employed, or that the first element must precede the second element in some manner.
Additionally, a person having ordinary skill in the art would understand that information and signals can be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits and symbols, for example, which may be referenced in the above description can be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.
A person of ordinary skill in the art would further appreciate that any of the various illustrative logical blocks, modules, processors, means, circuits, methods and functions described in connection with the aspects disclosed herein can be implemented by electronic hardware (e.g., a digital implementation, an analog implementation, or a combination of the two) , firmware, various forms of program or design code incorporating instructions (which can be referred to herein, for convenience, as "software" or a "software module) , or any combination of these techniques. To clearly illustrate this interchangeability of hardware, firmware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware, firmware or software, or a combination of these techniques, depends upon the particular application and design constraints imposed on the overall system. Skilled artisans can implement the described functionality in various ways for each particular application, but such implementation decisions do not cause a departure from the scope of the present disclosure.
Furthermore, a person of ordinary skill in the art would understand that various illustrative logical blocks, modules, devices, components and circuits described herein can be implemented within or performed by an integrated circuit (IC) that can include a general purpose processor, a digital signal processor (DSP) , an application specific integrated circuit (ASIC) , a field programmable gate array (FPGA) or other programmable logic device, or any combination thereof. The logical blocks, modules, and circuits can further include antennas and/or transceivers to communicate with various components within the network or within the device. A general purpose processor can be a microprocessor, but in the alternative, the processor can be any conventional processor, controller, or state machine. A processor can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other suitable configuration to perform the functions described herein.
If implemented in software, the functions can be stored as one or more instructions or code on a computer-readable medium. Thus, the steps of a method or algorithm disclosed herein can be implemented as software stored on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that can be enabled to transfer a computer program or code from one place to another. A storage media can be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer.
In this document, the term "module" as used herein, refers to software, firmware, hardware, and any combination of these elements for performing the associated functions described herein. Additionally, for purpose of discussion, the various modules are described as discrete modules; however, as would be apparent to one of ordinary skill in the art, two or more modules may be combined to form a single module that performs the associated functions according embodiments of the present solution.
Additionally, memory or other storage, as well as communication components, may be employed in embodiments of the present solution. It will be appreciated that, for clarity purposes, the above description has described embodiments of the present solution with reference to different functional units and processors. However, it will be apparent that any suitable distribution of functionality between different functional units, processing logic elements or domains may be used without detracting from the present solution. For example, functionality illustrated to be performed by separate processing logic elements, or controllers, may be performed by the same processing logic element, or controller. Hence, references to specific functional units are only references to a suitable means for providing the described functionality, rather than indicative of a strict logical or physical structure or organization.
Various modifications to the embodiments described in this disclosure will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the scope of this disclosure. Thus, the disclosure is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the novel features and principles disclosed herein, as recited in the claims below.

Claims

A wireless communication method, comprising:

identifying, by a first one of a plurality of wireless communication nodes that are communicatively coupled to a network node, a channel space, wherein the channel space is formed by channel response vectors from the first wireless communication node to a plurality of wireless communication devices;

deriving, by the first wireless communication node, a common space from the channel space; and

determining, by the first wireless communication node, according to a difference between the common space and the channel space, an individual space for precoding a downlink (DL) transmission per each of the plurality of wireless communication devices.
The wireless communication method of claim 1, further comprising:

deriving, by the first wireless communication node, the common space based on measured channel responses between the first wireless communication node and the plurality of wireless communication devices;

calculating, by the first wireless communication node, a first parameter based on the common space;

sending, by the first wireless communication node to the network node, the first parameter; and

receiving, by the first wireless communication node from the network node, a second parameter;

wherein the individual space is determined based on the second parameter, the common space, and the channel space.
The wireless communication method of claim 1, further comprising:

determining, by the first wireless communication node, an anchor one of the plurality of wireless communication devices;

deriving, by the first wireless communication node, the common space based on measuring channel responses between the first wireless communication node and the anchor wireless communication device;

sending, by the first wireless communication node to the network node, the first parameter.
The wireless communication method of any of claim 2 or 3, wherein the plurality of wireless communication nodes are not communicatively coupled to each other.
The wireless communication method of claim 1, further comprising:

deriving, by the first wireless communication node, the common space based on measured channel responses between the first wireless communication node and the plurality of wireless communication devices;

calculating, by the first wireless communication node, a first parameter based on the common space;

sending, by the first wireless communication node to a second one of the plurality of wireless communication nodes, the first parameter; and

receiving, by the wireless communication node from a last one of the plurality of wireless communication nodes, a second parameter;

wherein the individual space is determined based on the second parameter, the common space, and the channel space.
The wireless communication method of claim 1, further comprising:

determining, by the first wireless communication node, an anchor one of the plurality of wireless communication devices;

deriving, by the first wireless communication node, the common space based on measured channel responses between the first wireless communication node and the anchor wireless communication device;

sending, by the first wireless communication node to a second one of the plurality of wireless communication nodes, the first parameter.
The wireless communication method of any of claim 5 or 6, wherein each of the plurality of wireless communication nodes is configured to receive the first parameter from a preceding one of the plurality of wireless communication nodes.
The wireless communication method of any of claim 5 or 6, wherein the plurality of wireless communication nodes are communicatively coupled to one another unidirectionally or bidirectionally.
The wireless communication method of claim 1, further comprising:

deriving, by the first wireless communication node, the common space based on measuring channel responses between the first wireless communication node and the plurality of wireless communication devices;

calculating, by the first wireless communication node, a first parameter based on the common space;

sending, by the first wireless communication node to a second one of the plurality of wireless communication nodes, the first parameter; and

receiving, by the wireless communication node from the network node, a second parameter;

wherein the individual space is determined based on the second parameter, the common space, and the channel space.
The wireless communication method of any of claim 2, 5, or 9, wherein the first parameter is a component of a global normalization factor for all the wireless communication nodes.
The wireless communication method of any of claim 3 or 6, wherein the first parameter is a user identification of the anchor wireless communication device.
The wireless communication method of claim 9, wherein the first and second wireless communication nodes belong to one of a plurality of subsets of the plurality of wireless communication nodes.
The wireless communication method of claim 10, wherein the subsets of wireless communication nodes are not communicatively coupled to each other.
A wireless communications apparatus comprising a processor and a memory, wherein the processor is configured to read code from the memory and implement a method recited in any of claims 1 to 13.
A computer program product comprising a computer-readable program medium code stored thereupon, the code, when executed by a processor, causing the processor to implement a method recited in any of claims 1 to 13.