WO2018224146A1 - Système de communication sans fil utilisant des liaisons latérales - Google Patents

Système de communication sans fil utilisant des liaisons latérales Download PDF

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Publication number
WO2018224146A1
WO2018224146A1 PCT/EP2017/063930 EP2017063930W WO2018224146A1 WO 2018224146 A1 WO2018224146 A1 WO 2018224146A1 EP 2017063930 W EP2017063930 W EP 2017063930W WO 2018224146 A1 WO2018224146 A1 WO 2018224146A1
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Prior art keywords
client device
precoder
network node
precoded
symbols
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PCT/EP2017/063930
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English (en)
Inventor
Junshi Chen
Chaitanya TUMULA
Sergei SEMANOV
Neng Wang
Zuleita HO
Thanos DIMITRIOU
Fredrik RUSEK
Krishna CHITTI
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Huawei Technologies Co., Ltd.
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Priority to PCT/EP2017/063930 priority Critical patent/WO2018224146A1/fr
Publication of WO2018224146A1 publication Critical patent/WO2018224146A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/022—Site diversity; Macro-diversity
    • H04B7/026—Co-operative diversity, e.g. using fixed or mobile stations as relays
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0452—Multi-user MIMO systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J11/00—Orthogonal multiplex systems, e.g. using WALSH codes
    • H04J11/0023—Interference mitigation or co-ordination
    • H04J11/0026—Interference mitigation or co-ordination of multi-user interference
    • H04J11/0036—Interference mitigation or co-ordination of multi-user interference at the receiver
    • H04J11/004—Interference mitigation or co-ordination of multi-user interference at the receiver using regenerative subtractive interference cancellation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0041—Arrangements at the transmitter end
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0045—Arrangements at the receiver end
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L2001/0092—Error control systems characterised by the topology of the transmission link
    • H04L2001/0097—Relays
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/02—Terminal devices
    • H04W88/04—Terminal devices adapted for relaying to or from another terminal or user

Definitions

  • the invention relates to methods and devices for use in a wireless communication system.
  • the invention relates to methods and devices used in a wireless communication system using side links.
  • the network is configured to connect client devices such as User Equipments (UEs) to the network.
  • client devices such as User Equipments (UEs)
  • UEs User Equipments
  • a client device is enabled to communicate via the network.
  • NOMA non- orthogonal multiple access
  • the performance of the network can be further improved with collaborative NOMA, in which, there exists a licensed or unlicensed communication link between the UEs served by the network node.
  • the communication link between the UEs is called side-link.
  • the UEs using the side-link are called cooperative (or collaborative) UEs.
  • the network node can design efficient transmission schemes by exploiting the side-link between the UEs.
  • the side link between the UEs can be used either for interference cancellation (IC) or for relaying data.
  • the network node In the collaborative NOMA, the network node multiplexes two UEs over the same time-frequency resource but separates them in the power domain as in the conventional NOMA. However, in addition to the decoding by successive interference cancellation (SIC) at one of the UEs as in the conventional NOMA, relaying of information from one or more collaborating UEs is also performed.
  • SIC successive interference cancellation
  • the network node can design efficient transmission schemes to improve the throughput of the network. Similar to the link between the network node and the cooperative UEs, the side-link also has a finite capacity.
  • a network node comprising at least two antennas.
  • the network node is configured to receive information that a first client device and a second client device are in communication with each other over a side link and to determine a first precoder for transmitting symbols directly to the first client device and to the second client device.
  • the network node is also configured to determine a second precoder for transmitting symbols to the first client device and to the second client device, by exploiting the side link between the first client device and the second client device and to obtain a precoded symbol vector from a symbol vector comprising symbols intended for the first client device and the second client device, using the first precoder and the second precoder.
  • the network node can then broadcast the precoded symbol vector using said at least two antennas.
  • the network node is configured to receive capacity information about the capacity of the side link between the first client device and the second client device, and to determine the first precoder and the second precoder based on the received capacity information.
  • the first and the second precoder design can be further enhanced.
  • the network node is configured to receive the capacity information about the capacity of the side link between the first client device and the second client device from at least one of the first client device and the second client device.
  • the capacity information about the capacity of the side link can be sent directly from a client device to the network node.
  • the network node is configured to receive direction information about if the side link is bi-directional or uni-directional, and to determine the first precoder and the second precoder based on the received direction information.
  • the second precoder is configured to match the set-up between the client devices and thereby to enhance the transmission.
  • the network node is configured to set up an optimization problem for determining i) the first precoder and second precoder ii) code rates of the symbols precoded using the first precoder and the second precoder iii) the power allocation for the symbols precoded using the first precoder and the second precoder, based on the solution that best solves the optimization problem.
  • the solution to the optimization problem provides optimal parameters to improve the transmission from the network node to the first client device and the second client device.
  • the network node is configured to set up the optimization problem with the objective to maximize a balanced sum-rate of the first client device and the second client device.
  • the same data rates are delivered to the first client device and the second client device. This can be useful from the quality of service point of view.
  • a balanced sum-rate implies that the sum-rate when the data rates delivered to the first client device and the second client device are the same.
  • the network node can be configured to formulate any other optimization problem in the context of delivering data to the first client device and the second client device according to the first aspect of the invention.
  • the network node is configured to set the first precoder to be a minimum mean square error, MMSE, precoder.
  • minimum MSE can be achieved for the data symbols precoded using the first precoder.
  • the network node is configured to precode every symbol but the last symbol of the symbol vector transmitted to a client device with the second precoder and to precode the last symbol of the symbol vector transmitted to the client device using the first precoder.
  • an efficient precoding can be achieved that optimizes the transmission from the network node to the first client device and the second client device.
  • the network node is configured to transmit a decoding order of symbols in the symbol vector precoded using the second precoder to at least one of the first client device and the second client device.
  • a decoding order of symbols in the symbol vector precoded using the second precoder to at least one of the first client device and the second client device.
  • the network node is configured to determine which of the first client device and the second client device is to use the side link first, and to transmit sequence information about which of the first client device and the second client device that is to first use the side link when the first client device and the second client device are bi-directionally connected.
  • sequence information about which of the first client device and the second client device that is to first use the side link when the first client device and the second client device are bi-directionally connected.
  • a client device comprising a first transceiver for communication with a network node and a second transceiver for direct communication with at least one second client device over a side link.
  • the client device is configured to receive using the first transceiver a broadcasted precoded symbol vector from the network node, the symbols of the broadcasted precoded symbol vector obtained by precoding a symbol vector with a first precoder and a second precoder, and to receive a decoding order of the symbols of the symbol vector precoded with the second precoder.
  • the client device is also configured to decode the symbols of the symbol vector precoded with the second precoder based on the decoding order, and to transmit the decoded symbols of the symbol vector precoded with the second precoder to the second client device using the second transceiver over the side link.
  • a client device that is enabled to better exploit the side link is provided, whereby, the overall transmission in a radio communication system can be improved.
  • the client device may transmit the demodulated symbols instead of the decoded symbols, of the symbol vector precoded with the second precoder to the second client device using the second transceiver over the side link. That is, throughout the text, a decoded symbol maybe replaced with a demodulated symbol.
  • the client device is configured to send capacity information to the network node indicating the capacity of the side link.
  • the network node is enabled to use the capacity information when computing the first precoder and the second precoder, which can improve the transmission efficiency.
  • the client device is configured to receive from the second client device a decoded symbol of the symbol vector precoded with the second precoder, and further configured to use interference cancellation to remove an interference caused by the received decoded symbol from the received broadcasted precoded symbol vector.
  • an efficient decoding mechanism that uses interference cancellation of the symbols decoded by the other client device can be achieved.
  • the client device is configured to send to the network node direction information about if the side link is bi-directional or unidirectional.
  • the network node can gain improved knowledge of the side link and design the precoders accordingly.
  • the invention in further aspects provide methods and computer program products that can be used in the devices set out above.
  • Fig. 1 shows a wireless communication system
  • Fig. 2 shows a flowchart illustrating steps performed in a network node
  • Fig. 3 shows a flowchart illustrating steps performed in a client device
  • Fig. 4 schematically illustrates a network node
  • Fig. 5 schematically illustrates a client device
  • Fig. 6 is a flow chart illustrating symbol decoding for a pair of UEs configured to communicate bi- directionally over a side link
  • Fig. 7 is a flow chart illustrating symbol decoding for a pair of UEs configured to communicate uni- directionally over a side link.
  • a cooperative decoding mechanism can be used for a closely spaced pair of client devices such as UEs or other communicating entities that cooperate directly over a, typically, unlicensed side-link with little or no assistance from any network node.
  • the UEs also referred to as terminals or client devices
  • the UEs should have two different radio interfaces.
  • one of the radio interfaces at the UEs can use the Long-term evolution (LTE) or the fifth-generation wireless technology and the second radio interface can use Wi-Fi, Bluetooth or any near filed- communication technology.
  • LTE Long-term evolution
  • the second radio interface can use Wi-Fi, Bluetooth or any near filed- communication technology.
  • the side-link communication can also take place over a licensed frequency band that uses a different frequency compared to the frequency band used for the communication from the network node to the UEs.
  • the system 100 comprises a network node 104 (such as a base station) in communication with a number of client devices 101 , 102 over a radio interface.
  • the network node is provided with an antenna arrangement comprising at least two antennas 105.
  • the channels from the network node to the client devices can be Multiple Input Single Output, MISO, channels.
  • the client devices 101 , 102 are also in radio communication with each other over a side link.
  • the resource allocation in a transmission from the network node to the client devices typically involves finding the power allocation and implementing a precoder design that takes into consideration the side-link capacity and the decoding mechanism of the client devices. Further, the effects of both power imbalance and correlation between the client devices can be included.
  • the precoder consists of two parts, a first, cooperative part for which cooperative decoding can be performed at the client devices and a second, non-cooperative part.
  • the second, non- cooperative part can typically be a minimum mean square error, MMSE, precoder.
  • the first part can take into consideration the finite side-link capacity in its design while the second part is included to utilize the remaining total transmit power to transmit the data.
  • the cooperative part can be based on channel inversion and the non-cooperative part can be based on the minimum mean squared error (MMSE) metric. Interference from the cooperative part can be managed at the client devices using interference cancellation in the cooperative phase. A part of the total power is used to design the cooperative part of the precoder and the remaining power is used for the MMSE part of the precoder.
  • MMSE minimum mean squared error
  • a flowchart illustrating some steps performed when determining the precoders in the network node with at least two antennas is shown.
  • the network node receives information that a first client device and a second client device are in communication with each other over a side link. The information can for example be received directly from one of the client devices.
  • the network node determines a first precoder for transmitting symbols directly to the first client device and to the second client device, and determines a second precoder for transmitting symbols to the first client device and to the second client device, by exploiting the side link between the first client device and the second client device.
  • the first and second precoders can advantageously be determined in accordance with the detailed embodiments set out below.
  • the network node then, in a step 25, obtains a precoded symbol vector from a non- precoded symbol vector comprising symbols intended for the first client device and the second client device, using the first precoder and the second precoder. Finally, in a step 27, the network node broadcasts the precoded symbol vector using the at least two antennas.
  • the decoding can be performed as shown in Fig. 3.
  • the client device comprises a first transceiver for communication with the network node and a second transceiver for direct communication with at least one second client device over a side link.
  • the client device receives, using the first transceiver, a broadcasted precoded symbol vector from the network node.
  • the symbols of the broadcasted precoded symbol vector are obtained by precoding a non-precoded symbol vector with a first precoder and a second precoder.
  • the client device receives a decoding order of the symbols of the non-precoded symbol vector precoded with the second precoder.
  • the symbols of the non-precoded symbol vector precoded with the second precoder are then decoded in a step 35 based on the decoding order.
  • the client device transmits the decoded symbols of the non-precoded symbol vector precoded with the second precoder to the second client device using the second transceiver over the side link.
  • a precoding can be performed with one of the cooperating client devices 1 01 , 102 reporting to the network node 1 04 the side-link capacity C and the network node can use that capacity information when designing the precoders.
  • the network node 104 can be configured to decide the decoding order of the symbols (precoded with the second precoder) at the client devices 101 , 102. Also, the network node 104 can decide which client device 101 , 102 that is to access the side-link first if the client devices 101 , 102 communicate bi-directionally. The network node 104 can further formulate optimization problems and solve them to obtain the first precoder corresponding to the non-cooperative part and the second precoder corresponding to the cooperative part.
  • the network node 104 obtains the code rates and the power allocation corresponding to different symbols precoded using the first precoder and the second precoder.
  • the network node can in some implementations design the second precoder corresponding to the cooperative part, to precode some of the intended symbols transmitted to each client device.
  • the network node can also design the first precoder corresponding to the non-cooperative part to precode the remaining symbol(s) of the intended symbols transmitted to each client device.
  • the first precoder corresponding to the non-cooperative part can advantageously be a minimum mean square error, MMSE, precoder.
  • the network node could also use another suitable precoder as the first precoder corresponding to the non- cooperative part.
  • only the last symbol intended for each client device is precoded using the first precoder.
  • the network node may take into consideration the reported capacity value C of the side-link between the client devices. To increase the data rate for each client device, the network node implements the first precoder corresponding to the non-cooperative part and splits the transmit power between the first and the second precoders.
  • the network node can encode an incoming binary stream and digitally modulate the binary stream to generate modulated symbols.
  • Multiple binary streams can be sent to a given client device by modulating each stream separately to generate modulation symbols corresponding to different layers.
  • the symbols corresponding to different layers of a given client device can correspond to codewords with different code rates that are obtained as a solution of the optimization problem solved by the network node.
  • the modulated symbols corresponding to different layers are stacked into a vector in a given order that is decided by the network node. This order directly relates to the decoding order used at the client devices since there is a code-rate defined for each symbol.
  • the network node decides the decoding order.
  • the first client device to access the side-link while cooperatively decoding the received symbols can also be decided.
  • the client devices can then receive the multiplexed data symbols and can also receive information regarding which client device that is to use the cooperative link first. Further, the decoding order each client device should use corresponding to its layers can be received. The two decoding orders received by two client devices can be different. Once the multiplexed data symbols are received, one of the client devices (the first client device) starts the decoding process by decoding its first symbol (corresponding to the decoding order information received from the network node) in the presence of the intra-layer and inter-layer interference. This decoded symbol is transmitted over the side-link to the second client device.
  • the second client device can now remove the inter-user (or inter-layer) interference corresponding to the received decoded symbol from its received signal and decode its first symbol (corresponding to the decoding order information received from the network node) in the presence of remaining interference.
  • This decoded symbol is transmitted to the first client device over the side-link.
  • the first client device will now remove the inter-layer interference corresponding to this received decoded symbol, and decode its second symbol (corresponding to the decoding order information received from the network node) as before.
  • This decoded symbol is sent over the side-link to the second client device.
  • the second client device can now decode its second symbol (corresponding to the decoding order information received from the network node) in the similar manner as for its first symbol.
  • each client device accesses the side-link and decodes the symbols in a round robin manner till all the layers (or symbols) are decoded. This terminates the cooperative decoding phase for the symbols multiplexed using the second precoder. For the last symbols corresponding to the non-cooperative part, which are precoded with the first precoder, the UEs decode their respective symbols without any cooperation.
  • the transmit symbol vector can be modified.
  • the side-link is used only once after all the inter-layer symbols are decoded at the client device which uses the side link.
  • the network node 104 can for example be a Base station in a cellular radio system such as a base station for an LTE radio network or any other central node in a wireless communication network.
  • the network node 104 comprises transceiver circuitry formed by a receiver 310 and a transmitter 330 for wireless communication with client devices 101 ,102.
  • the network node 104 further comprises a processor 340 that can use a memory 320.
  • the processor 340 can perform all the activities of the network node 104 as described herein and is operatively connected to the receiver 310 and transmitter 330.
  • the client device 101 can for example be a UE for use in a cellular radio network or any other type of client device used in a wireless communication network.
  • the client device 101 comprises transceiver circuitry formed by a receiver 210 and a transmitter 230 for wireless communication with a wireless network.
  • the transceiver circuitry is configured to support two different radio interfaces.
  • the radio interfaces can for example be Long-term evolution (LTE) and Bluetooth.
  • the client device 101 further comprises a processor 240 that can use a memory 220.
  • the processor 240 can perform all the activities of the client device as described herein and is operatively connected to the receiver 210 and transmitter 230.
  • the pair of UEs may be assumed to be a part of a larger network.
  • the constituent UEs are closely located and cooperate over a side-link to sequentially decode the symbols and cancel the interference.
  • M transmit antennas at a network node formed by a base station, BS and a single antenna at each UE the received signal model at the UEs can be written as:
  • y is the overall received signal vector, is the noise vector, is the (2 x M) MIMO channel matrix from the BS to the two UEs, s is the non-
  • the linear precoder PV in eqn. (1 ) has two parts, and is given by:
  • N denotes the number of layers sent to each of the UEs using the second precoder corresponding to the cooperative part.
  • the (2 x 2N) size second precoder W coop can be based on the channel inversion.
  • the (2 x 2) MMSE precoder is the first precoder corresponding to the non-cooperative part.
  • the second precoder is given as
  • the second precoder is defined as the cooperative precoder since the interference terms
  • the first precoder W mmse is non-cooperative since there is no UE cooperation while decoding the symbols precoded using this precoder.
  • the structure of should ideally be (M x 2N) since H is a (2
  • the derived channel matrix H can be mathematically expressed as a (2 x 2) matrix, hence the (2 x 2N) structure for W coop .
  • the matrix H can be obtained by the eigen-value decomposition or by the Cholesky decomposition of HH". This makes H independent of M.
  • the effective channel matrix for the cooperative part is F and for the non-cooperative part is the (2 x 2) matrix H.
  • the elements of the matrix F and the non-precoded symbol vector s depend on the assumed decoding mechanism and the decoding sequence.
  • the ((2 ⁇ /+2) x 1 ) symbol vector s is given as In relation to the spatial-multiplexing phenomena, each symbol in s is referred to as corresponding to a transmission layer. Usually very few symbols (or layers) may be transmitted (as small as N ⁇ 3) but to generalize the case, N symbols are considered here.
  • incoming encoded binary bits corresponding to one or more data streams are digitally modulated to form the symbols in s.
  • the BS decides the code-rate corresponding to each symbol, and also the order in which the symbols are stacked in s.
  • the code rate corresponding to each symbol in the non-precoded symbol vector s may vary.
  • the stacking order directly relates to the order in which the UEs decode their symbols. These symbols are multiplexed by the precoder (as Ws) and broadcasted (over the same time-frequency unit) to the UEs. As a result, each UE receives a single multiplexed symbol which includes a superposition of both the desired symbols and the inter-user symbols.
  • the structure of F and s shows the symbols stacked in a particular order. Such an arrangement is shown for easy understanding of the decoding process which is explained later.
  • Each symbol of the symbol vector s may be assumed to be modulated such that and where denotes the
  • each cooperative layer experiences intra-layer or intra-user interference (
  • Inter-layer or inter-user interference(/ mter ) from the cooperative layers of the other UE and interference (which is also inter-user but not from the cooperative part) from the non-cooperative MMSE layers of both the UEs (/ mmse ).
  • the i mmse for each UE is the same for all of its N cooperative layers, i.e., Tne expression of the cooperative rate of layer,, at UE/( as seen in equation (10) is a function of the ratio of received power of the layer,, data and the total interference experienced by it.
  • the total interference experienced by the symbol s kn corresponding to layer,, at U is the sum of the additive noise power, the intra-layer interference, the inter-user interference and the interference due to non-cooperative MMSE part.
  • the total achievable rate corresponding to all the layers of the cooperative part is given by
  • the achievable rate of the symbol corresponding to the non-cooperative MMSE layer at each does not involve the interference from the cooperative symbols of either UE. It is only a function of the effective non-cooperative channels as seen in equation ( is the overall achievable rate of UE*. In general, ⁇ and .
  • the bi-directional cooperative IC mechanism described next. Bi-directional Cooperative Decoding via side-link.
  • the symbols corresponding to cooperative transmission for UEi are denoted as s 11 , s 12
  • the symbols corresponding to cooperative transmission for UE 2 are denoted as s 21 , s 22 .
  • the optimization problems are formulated as functions of the rates achievable by each layer of the cooperative part and the rates corresponding to the non-cooperative part. The calculation of the rates is explained next.
  • the base station After receiving the capacity information of side-link capacity C from one of the UEs, the base station decides the ordering of layers for each UE and which of the two UEs accesses the side- link first.
  • the UE that uses the side-link first is labelled UEi and the other UE is UE 2 .
  • the base station then computes the rates of the layers corresponding to each UE as follows:
  • the BS evaluates the achievable rate of the first layer corresponding to the cooperative part of the transmission intended for UEi as
  • the interference term in the rate expression of includes from equation (7)
  • the BS assumes that decoded is sent to UE 2 via side-link, and UE 2 cancels the interference corresponding to from and decodes Hence, the BS computes the
  • the BS assumes that decoded is sent to UEi via side-link, and UEi cancels the
  • the BS assumes that decoded is sent to UE 2 via side-link, and UE 2 cancels the interference corresponding to and s from y and decodes . Hence the BS computes
  • the BS assumes that decoded is sent to UEi via side-link. Now the BS computes the achievable rate corresponding to the MMSE part of the transmission intended for UEi as
  • each UE's interference (which is also inter-
  • the base station uses the described rate expressions in the optimization problem to determine the matrices optimal achievable rates corresponding to the symbols transmitted to each of the UEs, and the associated power splitting between the cooperative precoder and the MMSE precoder based on the sidelink capacity C.
  • the BS also informs the
  • a step 61 the BS broadcasts the symbols 1 precoded
  • UEi decodes in the presence of interference from and transmits to UE 2 over
  • UE 2 removes the interference caused by from its received signal and decodes in the presence of interference from and the UE 2 transmits
  • UEi removes the interference caused by s and from its received signal and decodes s 12 in the presence of interference from s and
  • UE 2 transmits to UE 2 over the side link. Then, in a step 65, UE 2 removes the interference caused by and from its received signal and decodes in the presence of interference from
  • UEi removes the interference caused by and from its received signal and decodes in the presence of
  • UEi has no while UE 2 has no i intra .
  • the UEi has both the cooperative and
  • the BS uses the rate expressions for UEi based only on the decoded layers at UEi .
  • BS After decoding s n , BS assumes that UEi can subtract the interference corresponding to from its received signal y x and decode s 12 .
  • the corresponding rate expression for the second layer of the cooperative part is given by
  • the BS assumes that the UEi relays the information about and s to UE 2 using the side- link.
  • the UE 2 can cancel the interference corresponding to and from its received signal y 2 .
  • the BS then calculates the MMSE rates corresponding to the two UEs as
  • the base station uses the described rate expressions for the uni-directional case in the optimization problem corresponding to the uni-directional case to determine the matrices F, W, the achievable rates of the symbols transmitted to both the UEs, and the associated power splitting between the cooperative precoder and the MMSE precoder based on the side-link capacity C.
  • Fig. 7 the steps associated with the operations to be performed at the UEs for the uni-directional side-link case are described using a flow chart.
  • the BS broadcasts the symbols s 11( s 12 precoded using the cooperative precoder and the symbols precoded using the MMSE precoder.
  • the BS also sends the information about the decoding order of the symbols precoded using the cooperative precoder to UEi .
  • UEi decodes in the presence of interference from Next, in a step 73,
  • UEi removes the interference caused by from its received signal and decodes s 12 in the
  • UEi removes the interference caused by s from its received signal and decodes s t in
  • UE 2 removes the interference caused by s lx and decodes in the presence of interference from 3 ⁇ 4 .
  • Problem P 1 gives the formulation for the precoder design with the bi-directional cooperative decoding and non-cooperative MMSE. Balanced rates are given by constraint cl. Power P is allocated to the cooperative part F in constraint c2 and is bounded by the maximum available power P in constraint c4. The remaining power (P - P)is allocated to the MMSE part in constraint c3. Here it is required that for each UE be at most equal to the finite side-link capacity C [nats/sec] as given in constraint
  • P 3 gives the formulation for the design with only the cooperative-MMSE precoder along with raw-data transmission. P 3 is different from P 1 and P 2 since in does not exist and
  • constraint c9 where the sum of the retained rate and the received rate is the same for both UEs.
  • the power constraint is modified to
  • Problem P 4 gives the formulation for precoder design with uni-directional cooperative decoding and non-cooperative MMSE.
  • the elements of the F matrix even though these elements do not contribute to the rate expressions.
  • Balanced rates are given by constraint cl2, where the only term for UE 2 is from its MMSE part.
  • the side-link rate constraint which applies only to UEi is given in cl3.
  • the power constraints in remain the same as in .
  • Using the methods and devices as set out herein can provide an efficient wireless communication system for transmission to a pair of closely spaced client devices.
  • the client devices can directly cooperate over an out-of-band licensed or unlicensed side-links, i.e. a direct radio link between the client devices having a finite capacity.
  • the cooperative decoding mechanism reduces the load on the network node by sharing the signal processing task with the client devices.
  • the side-link can be used bi-directionally where each client device accesses the side link sequentially for interference cancellation while decoding or for relaying data between them.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

L'invention concerne des procédés et des dispositifs destinés à être utilisés dans un système de communication sans fil. Pour améliorer la transmission dans un système de communication radio, un mécanisme de décodage coopératif peut être utilisé pour une paire étroitement espacée de dispositifs clients tels que des équipements utilisateurs (UE) ou d'autres entités communicantes qui coopèrent directement, de façon générale, sur une liaison latérale sans licence, avec peu ou pas d'assistance d'un nœud de réseau. Le nœud de réseau peut utiliser deux précodeurs pour utiliser efficacement la liaison latérale. FIG. 2 :
PCT/EP2017/063930 2017-06-08 2017-06-08 Système de communication sans fil utilisant des liaisons latérales WO2018224146A1 (fr)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20140273862A1 (en) * 2013-03-15 2014-09-18 Futurewei Technologies, Inc. System and Method for Interference Cancellation Using Terminal Cooperation
US20150358971A1 (en) * 2014-06-10 2015-12-10 Qualcomm Incorporated Devices and methods for facilitating non-orthogonal wireless communications
EP3016307A1 (fr) * 2013-06-28 2016-05-04 NTT DoCoMo, Inc. Station de base sans fil, terminal utilisateur, méthode de communication sans fil, et système de communication sans fil

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20140273862A1 (en) * 2013-03-15 2014-09-18 Futurewei Technologies, Inc. System and Method for Interference Cancellation Using Terminal Cooperation
EP3016307A1 (fr) * 2013-06-28 2016-05-04 NTT DoCoMo, Inc. Station de base sans fil, terminal utilisateur, méthode de communication sans fil, et système de communication sans fil
US20150358971A1 (en) * 2014-06-10 2015-12-10 Qualcomm Incorporated Devices and methods for facilitating non-orthogonal wireless communications

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