CN107113912A - A kind of device-to-device communicator, system and method - Google Patents

A kind of device-to-device communicator, system and method Download PDF

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CN107113912A
CN107113912A CN201480083200.6A CN201480083200A CN107113912A CN 107113912 A CN107113912 A CN 107113912A CN 201480083200 A CN201480083200 A CN 201480083200A CN 107113912 A CN107113912 A CN 107113912A
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terminal
time slot
signal
transmitting
receiving
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马洁
刘陈
傅友华
宦澄
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Huawei Technologies Co Ltd
Nanjing University of Posts and Telecommunications
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Huawei Technologies Co Ltd
Nanjing University of Posts and Telecommunications
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    • 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

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Abstract

The present invention provides a kind of device-to-device communicator, system and method, carries out the processing that prelists to sent data symbol according to precoding vector by D2D launch terminals, obtains transmission signal；D2D launch terminals send the transmission signal to the first D2D terminals as D2D receiving terminals and as the 2nd D2D terminals of relaying respectively；D2D launch terminals will be sent to the first D2D terminals based on the transmission signal obtained after precoding vector processing, so that the first D2D terminals are decoded based on decoded vector to the reception signal received after transmission signal channel decline and path loss, the interference of other cellular terminals can be prevented effectively from.Also, because relaying is D2D terminals, which reduce the extra load of the base station of same cell.

Description

Device-to-device communication device, system and method Technical Field
The present invention relates to the field of wireless communication technologies, and in particular, to a device-to-device communication apparatus, system, and method.
Background
In recent years, with the increasing demand for data transmission rates by communication services, the spectrum resources in cellular networks have become increasingly scarce. A Device-to-Device (D2D) communication system is used as an extension of a cellular network, and the spectrum utilization rate of the network is effectively improved through a spectrum resource sharing mode, so that the problem of spectrum shortage is solved. D2D communication is an extension of cellular networks to improve network spectral efficiency and system performance by multiplexing the resources of the cellular network. Therefore, modeling the D2D communication system is mainly based on different shared resource patterns. Currently, there are two main modes for D2D communication to share resources: a non-orthogonal sharing mode and an orthogonal sharing mode. In the non-orthogonal sharing mode, the D2D user and the cellular user use the same resource and have interference with each other, and the base station needs to coordinate the transmission power of the two links. In the orthogonal sharing mode, D2D communication uses part of the resources and the remaining part is given to the cellular user. The base station in the cellular network determines whether the D2D communication adopts the orthogonal sharing mode or the non-orthogonal sharing mode according to the cell communication condition, the existing channel state, the cellular user location information, the link gain, the noise, the signal-to-interference-and-noise ratio and other network states, and the resource usage of other devices in the cell. The current research is mainly directed to a non-orthogonal sharing mode, and since interference exists between a D2D link and an existing cellular link after D2D communication is introduced, how to effectively control the interference caused by spectrum sharing becomes an urgent problem to be solved in order to ensure that D2D communication is reliably performed in a cellular network.
In order to reduce the influence of the above interference on D2D communication, in the prior art, relay forwarding is performed by using a base station in a cellular network to implement interference control, which mainly aims at medium interference in cellular communication, the base station converts a medium interference signal into a strong interference signal as a relay, and forwards the strong interference signal to a D2D device, and the D2D device that receives the strong interference signal cancels the interference of the strong interference signal by using an interference cancellation technique. Specifically, the D2D device demodulates/decodes the strong interference signal, reconstructs the strong interference signal, and subtracts the strong interference signal from the received signal, thereby obtaining a received signal without interference.
However, in the prior art, the base station in the cellular network is used for performing the interference resistance processing of the D2D communication, and when the base station is used as a relay and participates in the interference processing process, the base station needs to decode and encode signals, and then the processed signals are forwarded to the D2D device through the cellular network, which increases the extra load of the base station.
Disclosure of Invention
The invention provides a device-to-device communication device, a system and a method, which are used for reducing extra load of a base station.
A first aspect of the present invention provides a device-to-device D2D transmitting terminal, comprising:
the processing module is used for carrying out pre-coding processing on the data symbols to be sent according to the pre-coding vectors to obtain transmission signals;
a transceiving module for transmitting the transmission signals to a first D2D terminal and a second D2D terminal, respectively;
wherein the first D2D terminal is a receiving end of the transmission signal, and the second D2D terminal is a relay;
the expression of the precoding vector is as follows:
v＝[v1 v2]T
v is a precoding vector, v1Precoding vector elements employed in a first slot for the D2D transmitting terminal, the v2Precoding vector elements employed in a second time slot for the D2D transmitting terminal, the T representing a transpose of a vector;
v is1The expression of (a) is as follows:
Figure PCTCN2014090999-APPB-000001
v is2The expression of (a) is as follows:
Figure PCTCN2014090999-APPB-000002
wherein, the a1＝(dSD)-αhSDSaid b is1＝β(dSRdRD)-αhSRhRDSaidA ═ dCD)-αhCDWherein b is β (d)CRdRD)-αhCRhRDβ is the amplification factor of the second D2D terminal, DSDThe path distance of the D2D transmitting terminal from the first D2D terminal, the hSDFor the D2D transmitting terminal and the first D2D terminal's channel coefficients, the DSRFor the path distance of the D2D transmitting terminal from the second D2D terminal, the DRDThe path distance of the second D2D terminal from the first D2D terminal, the DCRThe path distance of the cellular terminal from the second D2D terminal, hSRFor the D2D transmitting terminal and the second D2D terminal's channel coefficients, the hRDThe h is a channel coefficient of the second D2D terminal and the first D2D terminalCRIs the channel coefficient of the cellular terminal and the second D2D terminal, the DCDThe path distance h is the distance between the cellular terminal and the first D2D terminalCDThe α represents a path loss exponent for the channel coefficients of the cellular terminal and the first D2D terminal.
With reference to the first aspect, in a first possible implementation manner, the transmission signal includes: a transmission signal of a first time slot and a transmission signal of a second time slot;
the transceiver module is specifically configured to send the transmission signal of the first time slot to a first D2D terminal and a second D2D terminal in the first time slot, respectively; transmitting a transmission signal of the second time slot to the first D2D terminal in the second time slot;
wherein, the transmission signal expression of the first time slot is:
S1＝v1s
said S1The s is the data symbol, which is a transmission signal of the first time slot;
the transmission signal expression of the second time slot is as follows:
S2＝v2s
said S2Is a transmission signal of the second time slot.
With reference to the first aspect or the first possible implementation manner of the first aspect, in a second possible implementation manner, the v satisfies the following equation:
Figure PCTCN2014090999-APPB-000004
wherein, said emaxRepresenting the eigenvector corresponding to the largest eigenvalue of the matrix, saidThe H represents the conjugate transpose and the u is the decoded vector.
Figure PCTCN2014090999-APPB-000005
With reference to the second possible implementation manner of the first aspect, in a third possible implementation manner, the expression of u is as follows:
Figure PCTCN2014090999-APPB-000006
with reference to the first aspect or any one of the foregoing possible implementation manners of the first aspect, in a fourth possible implementation manner, the processing module is further configured to select any one of a plurality of D2D terminals in an idle state except the first D2D terminal as the second D2D terminal before the transceiver module sends the transmission signal to the first D2D terminal and the second D2D terminal, respectively.
With reference to the first aspect or any one of the foregoing possible implementation manners of the first aspect, in a fifth possible implementation manner, the transceiver module is further configured to:
before the processing module performs precoding processing on data symbols to be transmitted according to precoding vectors to obtain transmission signals, pilot signals are respectively transmitted to the first D2D terminal and the second D2D terminal, so that the first D2D terminal determines the h according to the pilot signalsSDSo that the second D2D terminal determines the h according to the pilot signalSR；
Receiving feedback information sent by the first D2D terminal, wherein the feedback information includes the hSDH is describedRDAnd h is saidSRhRD。
A second aspect of the present invention is to provide a device-to-device D2D receiving terminal, comprising:
a transceiver module, configured to receive a first received signal in a first time slot, where the first received signal is a received signal after channel fading and path loss of a transmission signal of the first time slot sent by the D2D transmitting terminal; receiving a second received signal in a second time slot, where the second received signal is formed by superimposing a transmission signal in the second time slot sent by the D2D transmitting terminal and an amplified signal in the second time slot sent by a second D2D terminal after channel fading and path loss;
the processing module is used for decoding the first receiving signal according to the decoding vector to obtain first data information; decoding the second receiving signal according to the decoding vector to obtain second data information; combining the first data information and the second data information to obtain a data symbol;
the second D2D terminal is a relay, and the amplified signal of the second time slot is obtained by amplifying the transmission signal of the first time slot sent by the D2D transmitting terminal by the second D2D terminal; the expression of the decoding vector is as follows:
u＝[u1 u2]T
the u is a decoding vector, the u1A decoding vector element of a first time slot, configured to perform decoding processing on the first received signal to obtain the first data information; said u is2A decoding vector element of a second slot, configured to perform decoding processing on the second received signal to obtain the second data information, where T represents a transpose of a vector;
said u is1The expression of (a) is as follows:
Figure PCTCN2014090999-APPB-000007
said u is1The expression of (a) is as follows:
Figure PCTCN2014090999-APPB-000008
wherein, the
Figure PCTCN2014090999-APPB-000009
A ═ dCD)-αhCDWherein b is β (d)CRdRD)-αhCRhRDD is saidCDThe path distance h for a cellular terminal to the D2D receiving terminalCDChannel coefficients for the cellular terminal and the D2D receiving terminal, DRDFor the path distance of the second D2D terminal from the D2D receiving terminal, the DCRThe path distance of the cellular terminal from the second D2D terminal, hRDThe h is a channel coefficient of the second D2D terminal and the first D2D terminalCRThe α represents a path loss exponent for the channel coefficients of the cellular terminal and the second D2D terminal.
In combination with the second aspect, in a first possible implementation manner, the u satisfies the following equation:
wherein, said emaxRepresenting the eigenvector corresponding to the largest eigenvalue of the matrix, saidThe H represents the conjugate transpose.
Figure PCTCN2014090999-APPB-000011
With reference to the second aspect or the first possible implementation manner of the second aspect, in a second possible implementation manner, the transceiver module is further configured to: receiving a first pilot signal sent by the D2D transmitting terminal before receiving a first receiving signal in a first time slot, and determining h according to the first pilot signalSDH is saidSDChannel coefficients for the D2D transmitting terminals and the D2D receiving terminals;
receiving a second pilot signal sent by the second D2D terminal, and determining the h according to the second pilot signalSRhRDWherein the second pilot signal is obtained by amplifying the first pilot signal by the second D2D terminal;
receiving a third pilot signal sent by the second D2D terminal, and determining h according to the third pilot signalRDH is saidRDChannel coefficients for the second D2D terminal and the D2D receiving terminals;
sending feedback information to the D2D transmitting terminal, wherein the feedback information comprises the hSDH is describedRDAnd h is saidSRhRD。
A third aspect of the present invention is to provide a relay, which is a D2D terminal, including:
a transceiver module, configured to receive a first received signal in a first time slot, where the first received signal is a received signal of a transmission signal of the first time slot sent by the D2D transmitting terminal after channel fading and path loss; transmitting the amplified signal of the second time slot to a first D2D terminal at the second time slot;
and the amplifying module is used for amplifying the first receiving signal to obtain an amplified signal of a second time slot.
With reference to the third aspect, in a first possible implementation manner, the transceiver module is further configured to: receiving a first pilot signal sent by the D2D transmitting terminal before receiving a first receiving signal in a first time slot, and determining h according to the first pilot signalSRH is saidSRTransmitting channel coefficients for the D2D transmitting terminal and the second D2D terminal;
transmitting the second pilot signal to the first D2D terminal;
transmitting a third pilot signal to the first D2D terminal;
the amplifying module is further configured to amplify the first pilot signal to obtain a second pilot signal.
A fourth aspect of the present invention is to provide a device-to-device D2D transmitting terminal, comprising:
the processor is used for pre-coding the data symbols to be sent according to the pre-coding vectors to obtain transmission signals;
a transceiver for transmitting the transmission signals to a first D2D terminal and a second D2D terminal, respectively;
wherein the first D2D terminal is a receiving end of the transmission signal, and the second D2D terminal is a relay;
the expression of the precoding vector is as follows:
v＝[v1 v2]T
v is a precoding vector, v1Precoding vector elements employed in a first slot for the D2D transmitting terminal, the v2Precoding vector elements employed in a second time slot for the D2D transmitting terminal, the T representing a transpose of a vector;
v is1The expression of (a) is as follows:
v is2The expression of (a) is as follows:
Figure PCTCN2014090999-APPB-000013
wherein, the a1＝(dSD)-αhSDSaid b is1＝β(dSRdRD)-αhSRhRDSaid
Figure PCTCN2014090999-APPB-000014
A ═ dCD)-αhCDWherein b is β (d)CRdRD)-αhCRhRDβ is the amplification factor of the second D2D terminal, DSDThe path distance of the D2D transmitting terminal from the first D2D terminal, the hSDFor the D2D transmitting terminal and the first D2D terminal's channel coefficients, the DSRFor the path distance of the D2D transmitting terminal from the second D2D terminal, the DRDThe path distance of the second D2D terminal from the first D2D terminal, the DCRThe path distance of the cellular terminal from the second D2D terminal, hSRFor the D2D transmitting terminal and the second D2D terminal's channel coefficients, the hRDThe h is a channel coefficient of the second D2D terminal and the first D2D terminalCRIs the channel coefficient of the cellular terminal and the second D2D terminal, the DCDThe path distance h is the distance between the cellular terminal and the first D2D terminalCDThe α represents a path loss exponent for the channel coefficients of the cellular terminal and the first D2D terminal.
With reference to the fourth aspect, in a first possible implementation manner, the transmission signal includes: a transmission signal of a first time slot and a transmission signal of a second time slot;
the transceiver is specifically configured to transmit the transmission signal of the first time slot to a first D2D terminal and a second D2D terminal, respectively, in the first time slot; transmitting a transmission signal of the second time slot to the first D2D terminal in the second time slot;
wherein, the transmission signal expression of the first time slot is:
S1＝v1s
said S1The s is the data symbol, which is a transmission signal of the first time slot;
the transmission signal expression of the second time slot is as follows:
S2＝v2s
said S2Is a transmission signal of the second time slot.
With reference to the fourth aspect or the first possible implementation manner of the fourth aspect, in a second possible implementation manner, the v satisfies the following equation:
Figure PCTCN2014090999-APPB-000015
wherein, said emaxRepresenting the eigenvector corresponding to the largest eigenvalue of the matrix, saidThe H represents the conjugate transpose and the u is the decoded vector.
Figure PCTCN2014090999-APPB-000016
With reference to the second possible implementation manner of the fourth aspect, in a third possible implementation manner, the expression of u is as follows:
Figure PCTCN2014090999-APPB-000017
with reference to the fourth aspect or any one of the foregoing possible implementation manners of the fourth aspect, in a fourth possible implementation manner, the processor is further configured to select, before the transceiver transmits the transmission signal to a first D2D terminal and a second D2D terminal, any one of a plurality of D2D terminals in an idle state except the first D2D terminal as the second D2D terminal.
With reference to the fourth aspect or any one of the foregoing possible implementations of the fourth aspect, in a fifth possible implementation, the transceiver is further configured to:
before the processor performs precoding processing on data symbols to be transmitted according to precoding vectors to obtain transmission signals, pilot signals are respectively transmitted to the first D2D terminal and the second D2D terminal, so that the first D2D terminal determines the h according to the pilot signalsSDSo that the second D2D terminal determines the h according to the pilot signalSR；
Receiving feedback information sent by the first D2D terminal, wherein the feedback information includes the hSDH is describedRDAnd h is saidSRhRD。
A fifth aspect of the present invention is to provide a device-to-device D2D receiving terminal, including:
a transceiver, configured to receive a first received signal in a first time slot, where the first received signal is a received signal after channel fading and path loss of a transmission signal of the first time slot sent by the D2D transmitting terminal; receiving a second received signal in a second time slot, where the second received signal is formed by superimposing a transmission signal in the second time slot sent by the D2D transmitting terminal and an amplified signal in the second time slot sent by a second D2D terminal after channel fading and path loss;
the processor is used for decoding the first receiving signal according to the decoding vector to obtain first data information; decoding the second receiving signal according to the decoding vector to obtain second data information; combining the first data information and the second data information to obtain a data symbol;
the second D2D terminal is a relay, and the amplified signal of the second time slot is obtained by amplifying the transmission signal of the first time slot sent by the D2D transmitting terminal by the second D2D terminal; the expression of the decoding vector is as follows:
u＝[u1 u2]T
the u is a decoding vector, the u1A decoding vector element of a first time slot, configured to perform decoding processing on the first received signal to obtain the first data information; said u is2A decoding vector element of a second slot, configured to perform decoding processing on the second received signal to obtain the second data information, where T represents a transpose of a vector;
said u is1The expression of (a) is as follows:
Figure PCTCN2014090999-APPB-000018
said u is1The expression of (a) is as follows:
wherein, the
Figure PCTCN2014090999-APPB-000020
A ═ dCD)-αhCDWherein b is β (d)CRdRD)-αhCRhRDD is saidCDThe path distance h for a cellular terminal to the D2D receiving terminalCDChannel coefficients for the cellular terminal and the D2D receiving terminal, DRDFor the path distance of the second D2D terminal from the D2D receiving terminal, the DCRThe path distance of the cellular terminal from the second D2D terminal, hRDThe h is a channel coefficient of the second D2D terminal and the first D2D terminalCRThe α represents a path loss exponent for the channel coefficients of the cellular terminal and the second D2D terminal.
With reference to the fifth aspect, in a first possible implementation manner, the u satisfies the following equation:
Figure PCTCN2014090999-APPB-000021
wherein, said emaxRepresenting the eigenvector corresponding to the largest eigenvalue of the matrix, saidThe H represents the conjugate transpose.
Figure PCTCN2014090999-APPB-000022
With reference to the fifth aspect or the first possible implementation manner of the fifth aspect, in a second possible implementation manner, the transceiver is further configured to: receiving a first pilot signal sent by the D2D transmitting terminal before receiving a first receiving signal in a first time slot, and determining h according to the first pilot signalSDH is saidSDChannel coefficients for the D2D transmitting terminals and the D2D receiving terminals;
receiving a second pilot signal sent by the second D2D terminal, and determining the h according to the second pilot signalSRhRDWherein the second pilot signal is obtained by amplifying the first pilot signal by the second D2D terminal;
receiving a third pilot signal sent by the second D2D terminal, and determining h according to the third pilot signalRDH is saidRDChannel coefficients for the second D2D terminal and the D2D receiving terminals;
sending feedback information to the D2D transmitting terminal, wherein the feedback information comprises the hSDH is describedRDAnd h is saidSRhRD。
A sixth aspect of the present invention provides a relay device, where the relay device is a D2D terminal, and the relay device includes:
a transceiver, configured to receive a first received signal in a first time slot, where the first received signal is a received signal of a transmission signal of the first time slot sent by the D2D transmitting terminal after channel fading and path loss; transmitting the amplified signal of the second time slot to a first D2D terminal at the second time slot;
and the processor is used for amplifying the first receiving signal to obtain an amplified signal of a second time slot.
With reference to the sixth aspect, in a first possible implementation manner, the transceiver is further configured to: receiving a first pilot signal sent by the D2D transmitting terminal before receiving a first receiving signal in a first time slot, and determining h according to the first pilot signalSRH is saidSRTransmitting channel coefficients for the D2D transmitting terminal and the second D2D terminal;
transmitting the second pilot signal to the first D2D terminal;
transmitting a third pilot signal to the first D2D terminal;
the processor is further configured to amplify the first pilot signal to obtain a second pilot signal.
A seventh aspect of the present invention provides a device-to-device communication system comprising: at least one D2D transmitting terminal according to any one of the possible implementations of the first aspect or the first aspect, at least one D2D receiving terminal according to any one of the possible implementations of the second aspect or the second aspect, and a relay according to any one of the possible implementations of the third aspect or the third aspect.
An eighth aspect of the present invention is to provide a device-to-device communication method, including:
the D2D transmitting terminal carries out pre-coding processing on the data symbol to be transmitted according to the pre-coding vector to obtain a transmission signal;
the D2D transmitting terminal sends the transmission signal to a first D2D terminal and a second D2D terminal, respectively;
wherein the first D2D terminal is a receiving end of the transmission signal, and the second D2D terminal is a relay;
the expression of the precoding vector is as follows:
v＝[v1 v2]T
v is a precoding vector, v1Precoding vector elements employed in a first slot for the D2D transmitting terminal, the v2Precoding vector elements employed in a second time slot for the D2D transmitting terminal, the T representing a vector towardsTransposing the quantity;
v is1The expression of (a) is as follows:
Figure PCTCN2014090999-APPB-000023
v is2The expression of (a) is as follows:
Figure PCTCN2014090999-APPB-000024
wherein, the a1＝(dSD)-αhSDSaid b is1＝β(dSRdRD)-αhSRhRDSaidA ═ dCD)-αhCDWherein b is β (d)CRdRD)-αhCRhRDβ is the amplification factor of the second D2D terminal, DSDThe path distance of the D2D transmitting terminal from the first D2D terminal, the hSDFor the D2D transmitting terminal and the first D2D terminal's channel coefficients, the DSRFor the path distance of the D2D transmitting terminal from the second D2D terminal, the DRDThe path distance of the second D2D terminal from the first D2D terminal, the DCRThe path distance of the cellular terminal from the second D2D terminal, hSRFor the D2D transmitting terminal and the second D2D terminal's channel coefficients, the hRDThe h is a channel coefficient of the second D2D terminal and the first D2D terminalCRIs the channel coefficient of the cellular terminal and the second D2D terminal, the DCDThe path distance h is the distance between the cellular terminal and the first D2D terminalCDBeing the cellular terminal and the first D2D terminalSaid α represents a path loss exponent.
With reference to the eighth aspect, in a first possible implementation manner, the transmission signal includes: a transmission signal of a first time slot and a transmission signal of a second time slot;
the D2D transmitting terminal respectively transmits the transmission signals to a first D2D terminal and a second D2D terminal, including:
the D2D transmitting terminal sending the transmission signal of the first time slot to a first D2D terminal and a second D2D terminal, respectively, in the first time slot;
the D2D transmitting terminal sending a transmission signal for the second slot in the second slot to a first D2D terminal;
wherein, the transmission signal expression of the first time slot is:
S1＝v1s
said S1The s is the data symbol, which is a transmission signal of the first time slot;
the transmission signal expression of the second time slot is as follows:
S2＝v2s
said S2Is a transmission signal of the second time slot.
With reference to the eighth aspect or the first possible implementation manner of the eighth aspect, in a second possible implementation manner, the v satisfies the following equation:
wherein, said emaxRepresenting the eigenvector corresponding to the largest eigenvalue of the matrix, saidThe H represents the conjugate transpose and the u is the decoded vector.
Figure PCTCN2014090999-APPB-000027
With reference to the second possible implementation manner of the eighth aspect, in a third possible implementation manner, the expression of u is as follows:
Figure PCTCN2014090999-APPB-000028
with reference to the eighth aspect or any one of the foregoing possible implementation manners of the eighth aspect, in a fourth possible implementation manner, before the D2D transmitting terminal sends the transmission signal to the first D2D terminal and the second D2D terminal, respectively, the method further includes:
the D2D transmitting terminal selects any one of a plurality of D2D terminals in an idle state except the first D2D terminal as the second D2D terminal.
With reference to the eighth aspect or any one of the foregoing possible implementation manners of the eighth aspect, in a fifth possible implementation manner, before the D2D sending terminal performs precoding processing on a data symbol to be sent according to a precoding vector to obtain a transmission signal, the method further includes:
the D2D transmitting terminal sends pilot signals to the first D2D terminal and the second D2D terminal, respectively, to cause the first D2D terminal to determine the h from the pilot signalsSDSo that the second D2D terminal determines the h according to the pilot signalSR；
The D2D transmitting terminal receiving feedback information sent by the first D2D terminal, the feedback information including the hSDH is describedRDAnd h is saidSRhRD。
A ninth aspect of the present invention provides a device-to-device-to-device communication method, comprising:
a first D2D terminal receives a first received signal in a first time slot, wherein the first received signal is a received signal of a transmission signal of the first time slot sent by the D2D transmitting terminal after channel fading and path loss;
the first D2D terminal decodes the first received signal according to the decoding vector to obtain first data information;
the first D2D terminal receives a second received signal in a second time slot, where the second received signal is formed by superimposing a transmission signal in the second time slot sent by the D2D transmitting terminal and an amplified signal in the second time slot sent by the second D2D terminal after channel fading and path loss;
the second D2D terminal is a relay, and the amplified signal of the second time slot is obtained by amplifying the transmission signal of the first time slot sent by the D2D transmitting terminal by the second D2D terminal;
the first D2D terminal decodes the second received signal according to the decoding vector to obtain second data information;
the first D2D terminal combines the first data information and the second data information to obtain a data symbol;
wherein the decoding vector has the following expression:
u＝[u1 u2]T
the u is a decoding vector, the u1A decoding vector element of a first time slot, configured to perform decoding processing on the first received signal to obtain the first data information; said u is2A decoding vector element of a second slot, configured to perform decoding processing on the second received signal to obtain the second data information, where T represents a transpose of a vector;
said u is1The expression of (a) is as follows:
Figure PCTCN2014090999-APPB-000029
said u is1The expression of (a) is as follows:
Figure PCTCN2014090999-APPB-000030
wherein, the
Figure PCTCN2014090999-APPB-000031
A ═ dCD)-αhCDWherein b is β (d)CRdRD)-αhCRhRDD is saidCDThe path distance h is the distance between the cellular terminal and the first D2D terminalCDIs the channel coefficient of the cellular terminal and the first D2D terminal, the DRDThe path distance of the second D2D terminal from the first D2D terminal, the DCRThe path distance of the cellular terminal from the second D2D terminal, hRDThe h is a channel coefficient of the second D2D terminal and the first D2D terminalCRThe α represents a path loss exponent for the channel coefficients of the cellular terminal and the second D2D terminal.
With reference to the ninth aspect, in a first possible implementation manner, the u satisfies the following equation:
Figure PCTCN2014090999-APPB-000032
wherein, said emaxRepresenting the eigenvector corresponding to the largest eigenvalue of the matrix, saidThe H represents the conjugate transpose.
Figure PCTCN2014090999-APPB-000033
With reference to the ninth aspect or the first possible implementation manner of the ninth aspect, in a second possible implementation manner, before the first D2D terminal receives the first received signal in the first time slot, the method further includes:
the first D2D terminal receives the first pilot signal sent by the D2D transmitting terminal and determines h from the first pilot signalSDH is saidSDTransmitting channel coefficients for the D2D transmitting terminals with the first D2D terminal;
the first D2D terminal receives the second pilot signal transmitted by the second D2D terminal and determines the h according to the second pilot signalSRhRDWherein the second pilot signal is obtained by amplifying the first pilot signal by the second D2D terminalObtaining;
the first D2D terminal receives a third pilot signal transmitted by the second D2D terminal and determines h according to the third pilot signalRDH is saidRDChannel coefficients for the second D2D terminal and the first D2D terminal;
the first D2D terminal sending feedback information to the D2D transmitting terminal, the feedback information including the hSDH is describedRDAnd h is saidSRhRD。
A tenth aspect of the present invention provides a device-to-device communication method, comprising:
a second D2D terminal receives a first received signal in a first time slot, wherein the first received signal is a received signal of a transmission signal of the first time slot sent by the D2D transmitting terminal after channel fading and path loss;
the second D2D terminal amplifies the first received signal to obtain an amplified signal of a second time slot;
the second D2D terminal transmits the amplified signal of the second slot to the first D2D terminal in the second slot.
With reference to the tenth aspect, in a first possible implementation manner, before the second D2D terminal receives the first received signal in the first time slot, the method further includes:
the second D2D terminal receives the first pilot signal sent by the D2D transmitting terminal and determines h according to the first pilot signalSRH is saidSRTransmitting channel coefficients for the D2D transmitting terminal and the second D2D terminal;
the second D2D terminal amplifies the first pilot signal to obtain a second pilot signal, and sends the second pilot signal to the first D2D terminal;
the second D2D terminal transmits a third pilot signal to the first D2D terminal.
According to the device-to-device communication device, the system and the method provided by the embodiment of the invention, the data symbols to be sent are pre-coded through the D2D transmitting terminal according to the pre-coding vector, so that transmission signals are obtained; the D2D transmitting terminal respectively transmits the transmission signals to a first D2D terminal as a D2D receiving terminal and a second D2D terminal as a relay; because the precoding vector adopts the above-mentioned design mechanism, the D2D transmitting terminal sends the transmission signal obtained after the processing based on the precoding vector to the first D2D terminal, so that the first D2D terminal decodes the received signal received after the channel fading and path loss of the transmission signal based on the above-mentioned decoding vector, and can effectively avoid the interference of other cellular terminals. Also, since the D2D transmitting terminal transmits a transmission signal to the second D2D terminal as a relay in the embodiment of the present invention, it reduces the additional load of the base station of the same cell. And because the relay can help the single-antenna user network to form a virtual MIMO system, the channel expansion is effectively realized, and implementation conditions are provided for utilizing the precoding vector (or matrix) and the decoding vector (or matrix) provided above.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic diagram of a device-to-device communication system according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a D2D transmitting terminal according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a D2D receiving terminal according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a relay structure according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a general apparatus according to an embodiment of the present invention;
fig. 6 is a flowchart illustrating a device-to-device communication method according to an embodiment of the present invention;
fig. 7 is a flowchart illustrating another device-to-device communication method according to an embodiment of the present invention;
fig. 8 is a flowchart illustrating another device-to-device communication method according to an embodiment of the present invention;
fig. 9 is a flowchart illustrating another device-to-device communication method according to an embodiment of the present invention;
fig. 10 is a flowchart illustrating another device-to-device communication method according to an embodiment of the present invention;
fig. 11 is a flowchart illustrating another device-to-device communication method according to an embodiment of the present invention;
fig. 12 is a diagram illustrating SINR for the case where different schemes are based on full CSI;
FIG. 13 shows σeA schematic diagram of the performance impact on the scheme provided by the embodiment of the invention;
fig. 14 is a SINR diagram comparing the scheme provided in the embodiment of the present invention with other schemes in the case of incomplete CSI;
fig. 15 is a schematic diagram of the bit error rate of D2D communication under different schemes.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In addition to the above technical problems in the prior art, after the D2D device receives a strong interference signal forwarded by a relay, the D2D device in the prior art often has a large error in the decoding process due to its own decoding capability, thereby reducing the interference rejection capability of the D2D device.
In addition, there are other solutions in the prior art for reducing the interference of D2D communication, for example, the transmission power of D2D device is adjusted by designing a back off value (backoff value) under the condition of ensuring that the transmission power of the cellular communication device is unchanged, so that the interference to the cellular device is within a reasonable range. However, this approach does not take into account the interference of cellular communications with D2D communications, thereby reducing the interference rejection capability of D2D terminals.
As another example, intra-cell interference is balanced through power optimization under conditions where communication rates of cellular devices and D2D devices are constrained. However, this approach optimizes the intra-cell interference by maximizing system capacity at the expense of power.
To avoid the technical problems caused by the solutions of the prior art, embodiments of the present invention provide a device-to-device communication apparatus, system and method. The following description will be made by way of specific examples.
First, fig. 1 is a schematic diagram of a device-to-device communication system according to an embodiment of the present invention, and referring to fig. 1, the system takes a single-cell cellular network as an example, and there are 1 base station, 1 cellular terminal (C), 1D 2D communication pair (D2D transmitting terminal S and D2D receiving terminal D) and 1 relay (R) in the network. The D2D terminal and the cellular terminal share the uplink spectrum resource of the network. At this time, because the base station receives signals and has the advantage of hardware equipment, the influence of interference of the D2D communication is negligible, and therefore, the interference of the cellular communication on the D2D communication is focused.
Further, the present invention employs a more efficient interference control mechanism to achieve reliable communication of D2D. Currently, the most dominant Interference control mechanism is Interference Alignment (IA) technology. The basic idea of IA is to rationally design the precoding vector (or precoding matrix) of the transmission symbols at the transmitting terminal such that the interfering signal of the receiving terminal remains linearly independent from the desired signal and to minimize network interference through the action of the decoding vector (or decoding matrix) of the receiving terminal. Based on the idea of IA, the invention provides an interference suppression algorithm aiming at the interference problem in D2D communication from the viewpoints of precoding of transmitted signals and decoding of received signals, a precoding vector and a decoding vector are designed and obtained according to the interference suppression algorithm, and the precoding vector and the decoding vector are applied to carry out D2D communication, so as to avoid the interference of cellular terminals and improve the anti-interference capability of D2D terminals.
In addition, because the base station is used as the relay in the prior art, the load of the base station itself is increased, and therefore, to solve the technical problem, in the embodiment of the present invention, an idle D2D terminal is used as the relay, and the advantage of the D2D terminal as the relay is that: the extra load caused by the base station is avoided, and the D2D terminals of the relay and transceiving ends communicate through the D2D, so that the transmission efficiency is improved. Further, the embodiment of the invention introduces a relay to assist in realizing channel expansion. Because the relay can help the single-antenna user network to form a virtual Multiple-Input Multiple-Output (MIMO) system, the channel expansion is effectively realized, and implementation conditions are provided for the design of the precoding vector (or matrix) and the decoding vector (or matrix).
Based on the introduction of the relay and aiming at the D2D system in the invention, the embodiment of the invention provides an interference suppression algorithm. The algorithm improves the Signal to Interference plus Noise Ratio (SINR) performance of D2D communication through the step-by-step coding and decoding of a D2D transceiving terminal, and mainly aims to suppress cellular Interference at a receiving end and maximize the receiving SINR at a transmitting end. The method comprises the following specific steps: in the first step, the interference suffered by the D2D communication is suppressed by designing the decoding vector of the D2D receiving terminal. And secondly, on the basis of interference suppression, improving the SINR of the D2D receiving terminal by designing a precoding vector of the D2D transmitting terminal. Compared with the existing spectrum orthogonal scheme (D2D communication and cellular communication occupy different spectrum resources) and the MMSE receiving scheme (D2D receiving terminal adopts the MMSE receiving mode), the SINR and the communication performance of the D2D communication are obviously improved by the algorithm of the invention.
The principles of the precoding vector for the D2D transmitting terminal and the decoding vector for the D2D receiving terminal provided by the embodiment of the present invention are explained below with reference to fig. 1.
It should be noted that in the embodiment of the present invention, one cycle of D2D communication includes two slots, i.e., a first slot and a second slot, and the following embodiments describe a scheme using these two slots, while D2D communication may last for multiple cycles, and the D2D terminal uses the same processing manner in the first slot and the second cycle in each cycle.
Referring to fig. 1, when a single relay participates in communication, a time period is generally divided into two slots that are peer-to-peer. In the first time slot, the cellular terminal C and the D2D transmitting terminal S send signals, respectively
Figure PCTCN2014090999-APPB-000034
And
Figure PCTCN2014090999-APPB-000035
since the relay receives only the signal, the reception signals of D2D reception terminal D and relay R are:
Figure PCTCN2014090999-APPB-000036
Figure PCTCN2014090999-APPB-000037
wherein d isijRepresents the path distance between terminal i (i ∈ { S, R, C }) and terminal j (j ∈ { R, D }). h isijIndicating that the channel coefficients between terminal i and terminal j all obey a (0,1) distribution. α represents a path loss exponent. x is the number ofiRepresenting the transmitted signal of terminal i. n isjAdditive noise representing terminal j, all obeying (0, σ)2) And (4) distribution. The numbers in the channel coefficients, the transmit signal, and the additive noise superscript all represent the number of time slots for communication.
In the second time slot, the signal received in the first time slot is relayed and simultaneously the cellular terminal C and the D2D transmitting terminal S respectively send signals
Figure PCTCN2014090999-APPB-000038
And
Figure PCTCN2014090999-APPB-000039
at this time, the reception signal of the terminal D, D2D, is:
Figure PCTCN2014090999-APPB-000040
wherein β represents a relay amplification factor, and it should be noted that, in the embodiment of the present invention, an Amplify-and-Forward (AF) strategy is adopted as a relay forwarding mode.
According to formulae (1) to (3), defined hereinWherein the content of the first and second substances,and
Figure PCTCN2014090999-APPB-000043
independent of each other and mean obedience
Figure PCTCN2014090999-APPB-000044
PCRepresenting the transmit power of cellular terminal C. v and S represent the precoding vector and the data symbols (transmission symbols) of the D2D transmitting terminal S, respectively, the precoding vector satisfying the power constraint vHv＝1，E[|s|2]＝PS，PSRepresenting the transmit power of D2D transmitting terminal S. Since the relay adopts AF strategy, the relay amplification factor is preferable
Figure PCTCN2014090999-APPB-000045
PRIs the transmit power of the relay R. According to the above definition, the receiving signal of the terminal D by the D2D can be expressed as:
Figure PCTCN2014090999-APPB-000041
yD＝HSxS+HCxC+n (4)
wherein the content of the first and second substances,
Figure PCTCN2014090999-APPB-000046
Figure PCTCN2014090999-APPB-000047
furthermore, defining the 2 × 1-dimensional column vector u as the decoding vector of the receiving terminal D2D, the decoded signal can be obtained according to equation (4):
Figure PCTCN2014090999-APPB-000048
the first term is a useful signal, the second term is an interference signal, and the third term is noise. The decoded vector satisfies the power constraint uHu＝1。[]HRepresenting the conjugate transpose of a vector (or matrix).
According to equation (5), the SINR of D2D receiving terminal D can be expressed as:
Figure PCTCN2014090999-APPB-000049
wherein the content of the first and second substances,
Figure PCTCN2014090999-APPB-000050
the embodiment of the invention maximizes the SINR of D2D communication by adopting proper precoding vectors and decoding vectors. Thus, in conjunction with the objective function (6), the optimization problem of the present invention is represented as:
the interference suppression algorithm provided by the above embodiment of the present invention improves the SINR performance of D2D communication through the step-by-step coding and decoding of the D2D transceiving terminal, that is, considering the minimization of the dominant interference term and the maximization of the power of the dominant useful signal in equation (7), mainly the receiving end suppresses the cellular interference, and the originating end maximizes the received SINR, and the specific steps are as follows:
step 1: the interference suffered by the D2D communication is suppressed by designing the decoding vector of the D2D receiving terminal.
The optimization problem is represented as:
Figure PCTCN2014090999-APPB-000052
step 2: on the basis of the completion of interference suppression, the SINR of the D2D receiving terminal is improved by designing the precoding vector of the D2D transmitting terminal.
As can be seen from the above equation (7), in the case of D2D receiving terminal decoding vector u determination, SINR mainly depends on the power of the useful signal, so the optimization problem is expressed as:
Figure PCTCN2014090999-APPB-000053
further, in order to solve the above optimization problem, a specific derivation process is given below:
the first step is as follows: as can be seen from Rayleigh-Ritz (Rayleigh-Ritz) theorem, when a decoded vector satisfies the following equation (10):
the objective function in equation (8) above can obtain the minimum value
Figure PCTCN2014090999-APPB-000055
Wherein λ ismin[]Minimum eigenvalue of the representation matrix, said emaxAnd representing the eigenvector corresponding to the maximum eigenvalue of the matrix.
According to the formula (10), the solution method of the matrix eigenvector is used and the constraint u is usedHCalculating a decoding vector u of the D2D receiving terminal by taking u as 1:
Figure PCTCN2014090999-APPB-000056
wherein a ═ dCD)-αhCD，b＝β(dCRdRD)-αhCRhRD，
Figure PCTCN2014090999-APPB-000057
[]TRepresenting the transpose of a vector (or matrix).
The second step is that: due to the fact that
Figure PCTCN2014090999-APPB-000058
As can be seen from Rayleigh-Ritz (Rayleigh-Ritz) theorem, when a precoding vector satisfies the following equation (12):
Figure PCTCN2014090999-APPB-000059
the maximum value can be obtained by the objective function in the above formula (9)
Figure PCTCN2014090999-APPB-000060
Wherein λ ismax[]Maximum eigenvalue of the representation matrix, emax[]And representing the eigenvector corresponding to the maximum eigenvalue of the matrix.
According to equation (12), the solution method for the matrix eigenvectors is also used and depends on the limiting conditions vHv ═ 1 may yield the precoding vector v for the D2D transmitting terminal:
Figure PCTCN2014090999-APPB-000061
wherein, a1＝(dSD)-αhSD，b1＝β(dSRdRD)-αhSRhRDAnd δ is as defined in formula (11).
In conclusion, the obtained decoding vector u is a matrix
Figure PCTCN2014090999-APPB-000062
The feature vector corresponding to the minimum feature value, thenIs a matrix
Figure PCTCN2014090999-APPB-000064
I.e., the interference of the D2D receiving terminal has been minimized by the action of the decoded vector u. In the case of u being determined, the precoding vector v obtained is a matrix
Figure PCTCN2014090999-APPB-000065
The eigenvector corresponding to the largest eigenvalue, then
Figure PCTCN2014090999-APPB-000066
Is a matrix
Figure PCTCN2014090999-APPB-000067
I.e. the useful signal power of the D2D receiving terminal has been maximized by the action of the precoding vector v. Therefore, the SINR performance of the D2D receiving terminal is improved.
Further, in order to determine the precoding vector v and the decoding vector u as described above, the D2D transmitting end S is required to obtain channel feedback information, and a specific implementation is given below:
step 1: according to the pilot signal sent by the D2D transmitting terminal S, the relay R estimates the channel gain hSRD2D receiving end D estimates channel gain hSD；
Step 2: the relay R amplifies the received pilot signal sent by the D2D transmitting terminal S and forwards the pilot signal to the D2D receiving terminal D, and the D2D receiving terminal D estimates the channel gain product hSRhRD；
And step 3: according to the pilot signal sent by the relay R, the D2D receiving end D estimates the channel gain hRD；
And 4, step 4: according to the channel gain estimated by the D2D receiving end D, the channel gain is fed back to the D2D transmitting end S, and the D2D transmitting end S can obtain the channel gain hSD、hRDAnd hSRhRD。
Note: for the decoding vector u, the channel gain of the interfering channel takes its statistical value, i.e. the mean is 0 and the variance is 1.
TABLE 1 channel gain feedback procedure
Figure PCTCN2014090999-APPB-000068
Further, for the D2D transmitting end S, from the viewpoint of SNR of the channel, to estimate the channel gain, the specific process is as follows:
as shown in table 1, in step 1, the D2D transmitting end S sends a pilot signal xS,pilotAt this time, the pilot signals received by the receiver D of the relay R and the receiver D of D2D are pilot signals
Figure PCTCN2014090999-APPB-000069
Figure PCTCN2014090999-APPB-000070
Wherein, PSIs the preset power, x, of the S pilot signal at the transmitting end of D2DS,pilotThe power is normalized to 1. n isRAndrespectively representing additive noise at the receiving ends D of the relay R and the D2D, the mean value of the additive noise is 0, and the variance is sigma2A gaussian distribution of (a). From equations (14) - (15), the channel gain h can be estimatedSRAnd hSD：
Figure PCTCN2014090999-APPB-000072
In step 2, the relay R amplifies the received pilot signal yRAnd forwarding the pilot signal to the D2D receiving end D, wherein the pilot signal received by the D2D receiving end D is
Wherein, beta represents a relay amplification factor,
Figure PCTCN2014090999-APPB-000075
representing a mean of 0 and a variance of σ2Gaussian additive noise. From equation (18), the channel gain product h can be estimatedSRhRD：
Figure PCTCN2014090999-APPB-000076
In step 3, relay R transmits pilot signal xR,pilotAt this time, the pilot signal received by the receiving end D of D2D is:
Figure PCTCN2014090999-APPB-000077
wherein, PRIs the predetermined power, x, of the relayed R pilot signalR,pilotThe power is normalized to 1.
Figure PCTCN2014090999-APPB-000078
The additive noise of the receiving end D of D2D is represented, and is also subjected to mean value of 0 and variance of sigma2A gaussian distribution of (a). From equation (20), the channel gain h can be estimatedRD：
Figure PCTCN2014090999-APPB-000079
The channel gain product h can be further estimated by combining equation (19) and equation (21)SRhRD：
Figure PCTCN2014090999-APPB-000080
Finally, according to the channel gain estimated by the receiving end D of D2D, the channel gain is fed back to the transmitting end S of D2D, and the transmitting end S of D2D can obtain the channel gain | hSD|2、|hRD|2And | hSRhRD|2。
The following describes specific functions of the D2D transmitting terminal, the D2D receiving terminal, and the relay according to embodiments of the present invention, respectively, by using specific embodiments.
Fig. 2 is a schematic structural diagram of a D2D transmitting terminal according to an embodiment of the present invention, where the D2D transmitting terminal may specifically be a user equipment, a vehicle-mounted communication device, or the like having a D2D communication function, and referring to fig. 2, the D2D transmitting terminal includes: a processing module 100 and a transceiver module 101.
A processing module 100, configured to perform precoding processing on a data symbol to be sent according to a precoding vector to obtain a transmission signal;
a transceiving module 101 for transmitting the transmission signals to a first D2D terminal and a second D2D terminal, respectively;
wherein the first D2D terminal is a receiving end of the transmission signal, and the second D2D terminal is a relay;
the expression of the precoding vector is as follows:
v＝[v1 v2]T
v is a precoding vector, v1Precoding vector elements employed in a first slot for the D2D transmitting terminal, the v2Precoding vector elements employed in a second time slot for the D2D transmitting terminal, the T representing a transpose of a vector;
v is1The expression of (a) is as follows:
v is2The expression of (a) is as follows:
wherein, the a1＝(dSD)-αhSDSaid b is1＝β(dSRdRD)-αhSRhRDSaidA ═ dCD)-αhCDWherein b is β (d)CRdRD)-αhCRhRDβ is the amplification factor of the second D2D terminal, DSDThe path distance of the D2D transmitting terminal from the first D2D terminal, the hSDFor the D2D hairChannel coefficients of the radio terminal and the first D2D terminal, DSRFor the path distance of the D2D transmitting terminal from the second D2D terminal, the DRDThe path distance of the second D2D terminal from the first D2D terminal, the DCRThe path distance of the cellular terminal from the second D2D terminal, hSRFor the D2D transmitting terminal and the second D2D terminal's channel coefficients, the hRDThe h is a channel coefficient of the second D2D terminal and the first D2D terminalCRIs the channel coefficient of the cellular terminal and the second D2D terminal, the DCDThe path distance h is the distance between the cellular terminal and the first D2D terminalCDThe α represents a path loss exponent for the channel coefficients of the cellular terminal and the first D2D terminal.
In the D2D transmitting terminal provided in the embodiment of the present invention, a processing module performs precoding processing on a data symbol to be transmitted according to a precoding vector, so as to obtain a transmission signal; the transceiving module respectively transmits the transmission signals to a first D2D terminal and a second D2D terminal; because the precoding vector adopts the above-mentioned design mechanism, the D2D transmitting terminal sends the transmission signal obtained after the processing based on the precoding vector to the first D2D terminal, so that the first D2D terminal decodes the received signal received after the channel fading and path loss of the transmission signal based on the above-mentioned decoding vector, and can effectively avoid the interference of other cellular terminals. Also, since the D2D transmitting terminal transmits a transmission signal to the second D2D terminal as a relay in the embodiment of the present invention, it reduces the additional load of the base station of the same cell. And because the relay can help the single-antenna user network to form a virtual MIMO system, the channel expansion is effectively realized, and implementation conditions are provided for utilizing the precoding vector (or matrix) and the decoding vector (or matrix) provided above.
Further, as can be seen from the above, in one period, the D2D transmitting terminal sends transmission signals in two time slots, respectively, and therefore, the transmission signals include: a transmission signal of a first time slot and a transmission signal of a second time slot;
the transceiver module 101 is specifically configured to send the transmission signal of the first time slot to a first D2D terminal and a second D2D terminal in the first time slot, respectively; transmitting a transmission signal of the second time slot to the first D2D terminal in the second time slot;
wherein, the transmission signal expression of the first time slot is:
S1＝v1s
said S1The s is the data symbol, which is a transmission signal of the first time slot;
the transmission signal expression of the second time slot is as follows:
S2＝v2s
said S2Is a transmission signal of the second time slot.
As can be seen from the above, v satisfies the above formula (12).
The expression of u is referred to above in equation (11).
Optionally, the processing module 100 is further configured to select any one of a plurality of D2D terminals in an idle state except the first D2D terminal as the second D2D terminal before the transceiver module 101 sends the transmission signal to the first D2D terminal and the second D2D terminal, respectively.
Optionally, the transceiver module 101 is further configured to:
before the processing module 100 performs precoding processing on data symbols to be transmitted according to precoding vectors to obtain transmission signals, pilot signals are respectively transmitted to the first D2D terminal and the second D2D terminal, so that the first D2D terminal determines the h according to the pilot signalsSDSo that the second D2D terminal determines the h according to the pilot signalSR；
Receiving feedback information sent by the first D2D terminal, wherein the feedback information includes the hSDH is describedRDAnd h is saidSRhRD. Fig. 3 is a schematic structural diagram of a D2D receiving terminal according to an embodiment of the present invention, and referring to fig. 3, the D2D receiving terminal includes: a processing module 200, a transceiver module 201;
a transceiver module 201, configured to receive a first received signal in a first time slot, where the first received signal is a received signal after channel fading and path loss of a transmission signal of the first time slot sent by the D2D transmitting terminal; receiving a second received signal in a second time slot, where the second received signal is formed by superimposing a transmission signal in the second time slot sent by the D2D transmitting terminal and an amplified signal in the second time slot sent by a second D2D terminal after channel fading and path loss;
a processing module 200, configured to decode the first received signal according to the decoding vector to obtain first data information; decoding the second receiving signal according to the decoding vector to obtain second data information; combining the first data information and the second data information to obtain a data symbol;
the second D2D terminal is a relay, and the amplified signal of the second time slot is obtained by amplifying the transmission signal of the first time slot sent by the D2D transmitting terminal by the second D2D terminal; the expression of the decoding vector is as follows:
u＝[u1 u2]T
the u is a decoding vector, the u1A decoding vector element of a first time slot, configured to perform decoding processing on the first received signal to obtain the first data information; said u is2A decoding vector element of a second slot, configured to perform decoding processing on the second received signal to obtain the second data information, where T represents a transpose of a vector;
said u is1The expression of (a) is as follows:
Figure PCTCN2014090999-APPB-000084
said u is1The expression of (a) is as follows:
Figure PCTCN2014090999-APPB-000085
wherein, the
Figure PCTCN2014090999-APPB-000086
A ═ dCD)-αhCDWherein b is β (d)CRdRD)-αhCRhRDD is saidCDThe path distance h for a cellular terminal to the D2D receiving terminalCDChannel coefficients for the cellular terminal and the D2D receiving terminal, DRDFor the path distance of the second D2D terminal from the D2D receiving terminal, the DCRThe path distance of the cellular terminal from the second D2D terminal, hRDThe h is a channel coefficient of the second D2D terminal and the first D2D terminalCRThe α represents a path loss exponent for the channel coefficients of the cellular terminal and the second D2D terminal.
In the D2D receiving terminal provided in the embodiment of the present invention, the transceiver module receives the first received signal and the second received signal in the first time slot and the second time slot, respectively, and the processing module decodes the first received signal and the second received signal according to the decoding vector, and combines the first data information and the second data information obtained by decoding, so as to obtain the required data symbol. In this process, the second received signal includes a transmission signal of the second time slot sent by the D2D transmitting terminal and an amplified signal of the second time slot sent by the second D2D terminal, which are superimposed after channel fading and path loss; the second D2D terminal can effectively avoid extra load of the base station when serving as the relay, and meanwhile, because the second D2D terminal serves as the relay to transmit the amplified signal of the second time slot, channel expansion is achieved, and under such a condition, the first D2D terminal obtains the required data symbol after decoding processing by adopting the decoding processing in the above manner, so that the interference of cellular communication can be effectively avoided, and the interference resistance of D2D communication is improved.
Further, u satisfies the above formula (10).
Further, as can be seen from table 1 above, in order to determine the precoding vector v and the decoding vector u described above, the D2D transmitting end needs to obtain channel feedback information, and therefore the D2D receiving end also needs to perform corresponding steps, specifically, the transceiver module 201 is further configured to:
receiving a first pilot signal sent by the D2D transmitting terminal before receiving a first receiving signal in a first time slot, and determining h according to the first pilot signalSDH is saidSDChannel coefficients for the D2D transmitting terminals and the D2D receiving terminals;
receiving a second pilot signal sent by the second D2D terminal, and determining the h according to the second pilot signalSRhRDWherein the second pilot signal is obtained by amplifying the first pilot signal by the second D2D terminal;
receiving a third pilot signal sent by the second D2D terminal, and determining h according to the third pilot signalRDH is saidRDChannel coefficients for the second D2D terminal and the D2D receiving terminals;
sending feedback information to the D2D transmitting terminal, wherein the feedback information comprises the hSDH is describedRDAnd h is saidSRhRD。
Fig. 4 is a schematic diagram of a relay structure according to an embodiment of the present invention, where the relay is a D2D terminal, and referring to fig. 4, the relay includes: an amplifying module 300, a transceiver module 301;
a transceiver module 301, configured to receive a first received signal in a first time slot, where the first received signal is a received signal of a transmission signal of the first time slot sent by the D2D transmitting terminal after channel fading and path loss; transmitting the amplified signal of the second time slot to a first D2D terminal at the second time slot;
the amplifying module 300 is configured to amplify the first received signal to obtain an amplified signal of a second time slot.
The relay provided by the embodiment of the invention firstly takes the D2D terminal as the relay, which avoids unnecessary complexity added to the base station when the base station is used as the relay, and secondly, the transceiver module receives the first receiving signal sent by the D2D transmitting terminal in the first time slot; the amplifying module amplifies the first receiving signal to obtain an amplified signal of a second time slot; the transceiver module sends the amplified signal of the second time slot to the first D2D terminal in the second time slot. The amplifying module only needs to perform simple power amplification processing on the received signal, so that additional signaling control is not needed while effective anti-interference decoding is guaranteed at a D2D receiving end due to effective channel expansion, and complexity of relay processing is reduced.
Further, referring to table 1, in order to determine the precoding vector v and the decoding vector u described above, the D2D transmitting end needs to obtain channel feedback information, and a corresponding relay also needs to perform corresponding steps, specifically, the transceiver module 301 is further configured to:
receiving a first pilot signal sent by the D2D transmitting terminal before receiving a first receiving signal in a first time slot, and determining h according to the first pilot signalSRH is saidSRTransmitting channel coefficients for the D2D transmitting terminal and the second D2D terminal;
transmitting the second pilot signal to the first D2D terminal;
transmitting a third pilot signal to the first D2D terminal;
the amplifying module 300 is further configured to amplify the first pilot signal to obtain a second pilot signal.
Optionally, for the above D2D transmitting terminal, D2D receiving terminal and relay, fig. 5 is a schematic diagram of a structure of a general device provided in the embodiment of the present invention, and the D2D transmitting terminal, the D2D receiving terminal and the relay may all adopt the structure of the general device shown in fig. 5.
When the general-purpose device is a D2D transmitting terminal, the general-purpose device has the following functions:
a processor 400, configured to perform precoding processing on a data symbol to be sent according to a precoding vector, so as to obtain a transmission signal;
a transceiver 401 for transmitting the transmission signals to a first D2D terminal and a second D2D terminal, respectively;
wherein the first D2D terminal is a receiving end of the transmission signal, and the second D2D terminal is a relay;
the expression of the precoding vector is as follows:
v＝[v1 v2]T
v is a precoding vector, v1Precoding direction adopted in first time slot for D2D transmitting terminalA quantity element, said v2Precoding vector elements employed in a second time slot for the D2D transmitting terminal, the T representing a transpose of a vector;
v is1The expression of (a) is as follows:
v is2The expression of (a) is as follows:
Figure PCTCN2014090999-APPB-000088
wherein, the a1＝(dSD)-αhSDSaid b is1＝β(dSRdRD)-αhSRhRDSaid
Figure PCTCN2014090999-APPB-000089
A ═ dCD)-αhCDWherein b is β (d)CRdRD)-αhCRhRDβ is the amplification factor of the second D2D terminal, DSDThe path distance of the D2D transmitting terminal from the first D2D terminal, the hSDFor the D2D transmitting terminal and the first D2D terminal's channel coefficients, the DSRFor the path distance of the D2D transmitting terminal from the second D2D terminal, the DRDThe path distance of the second D2D terminal from the first D2D terminal, the DCRThe path distance of the cellular terminal from the second D2D terminal, hSRFor the D2D transmitting terminal and the second D2D terminal's channel coefficients, the hRDThe h is a channel coefficient of the second D2D terminal and the first D2D terminalCRIs the channel coefficient of the cellular terminal and the second D2D terminal, the DCDThe path distance h is the distance between the cellular terminal and the first D2D terminalCDThe α represents a path loss exponent for the channel coefficients of the cellular terminal and the first D2D terminal.
In the D2D transmitting terminal provided in the embodiment of the present invention, a processor performs precoding processing on a data symbol to be transmitted according to a precoding vector, so as to obtain a transmission signal; the transceiver transmits the transmission signals to a first D2D terminal and a second D2D terminal, respectively; because the precoding vector adopts the above-mentioned design mechanism, the D2D transmitting terminal sends the transmission signal obtained after the processing based on the precoding vector to the first D2D terminal, so that the first D2D terminal decodes the received signal received after the channel fading and path loss of the transmission signal based on the above-mentioned decoding vector, and can effectively avoid the interference of other cellular terminals. Also, since the D2D transmitting terminal transmits a transmission signal to the second D2D terminal as a relay in the embodiment of the present invention, it reduces the additional load of the base station of the same cell. And because the relay can help the single-antenna user network to form a virtual MIMO system, the channel expansion is effectively realized, and implementation conditions are provided for utilizing the precoding vector (or matrix) and the decoding vector (or matrix) provided above.
Preferably, the transmission signal includes: a transmission signal of a first time slot and a transmission signal of a second time slot;
the transceiver 401 is specifically configured to transmit the transmission signal of the first time slot to a first D2D terminal and a second D2D terminal in the first time slot, respectively; transmitting a transmission signal of the second time slot to the first D2D terminal in the second time slot;
wherein, the transmission signal expression of the first time slot is:
S1＝v1s
said S1The s is the data symbol, which is a transmission signal of the first time slot;
the transmission signal expression of the second time slot is as follows:
S2＝v2s
said S2Is a transmission signal of the second time slot.
As can be seen from the above, v satisfies the above formula (12).
The expression of u is referred to above in equation (11).
Optionally, the processor 400 is further configured to select any one of a plurality of D2D terminals in an idle state except the first D2D terminal as the second D2D terminal before the transceiver 401 sends the transmission signal to the first D2D terminal and the second D2D terminal, respectively.
Optionally, the transceiver 401 is further configured to:
before the processor 400 performs precoding processing on data symbols to be transmitted according to a precoding vector to obtain transmission signals, pilot signals are respectively transmitted to the first D2D terminal and the second D2D terminal, so that the first D2D terminal determines the h according to the pilot signalsSDSo that the second D2D terminal determines the h according to the pilot signalSR；
Receiving feedback information sent by the first D2D terminal, wherein the feedback information includes the hSDH is describedRDAnd h is saidSRhRD。
When the general-purpose device is a D2D receiving terminal, it has the following functions:
a transceiver 401, configured to receive a first received signal in a first time slot, where the first received signal is a received signal after channel fading and path loss of a transmission signal of the first time slot sent by the D2D transmitting terminal; receiving a second received signal in a second time slot, where the second received signal is formed by superimposing a transmission signal in the second time slot sent by the D2D transmitting terminal and an amplified signal in the second time slot sent by a second D2D terminal after channel fading and path loss;
a processor 400, configured to perform decoding processing on the first received signal according to a decoding vector to obtain first data information; decoding the second receiving signal according to the decoding vector to obtain second data information; combining the first data information and the second data information to obtain a data symbol;
the second D2D terminal is a relay, and the amplified signal of the second time slot is obtained by amplifying the transmission signal of the first time slot sent by the D2D transmitting terminal by the second D2D terminal; the expression of the decoding vector is as follows:
u＝[u1 u2]T
the u is a decoding vector, the u1A decoding vector element of a first time slot, configured to perform decoding processing on the first received signal to obtain the first data information; said u is2A decoding vector element of a second slot, configured to perform decoding processing on the second received signal to obtain the second data information, where T represents a transpose of a vector;
said u is1The expression of (a) is as follows:
Figure PCTCN2014090999-APPB-000090
said u is1The expression of (a) is as follows:
Figure PCTCN2014090999-APPB-000091
wherein, the
Figure PCTCN2014090999-APPB-000092
A ═ dCD)-αhCDWherein b is β (d)CRdRD)-αhCRhRDD is saidCDThe path distance h for a cellular terminal to the D2D receiving terminalCDChannel coefficients for the cellular terminal and the D2D receiving terminal, DRDFor the path distance of the second D2D terminal from the D2D receiving terminal, the DCRThe path distance of the cellular terminal from the second D2D terminal, hRDThe h is a channel coefficient of the second D2D terminal and the first D2D terminalCRThe α represents a path loss exponent for the channel coefficients of the cellular terminal and the second D2D terminal.
In the D2D receiving terminal provided in the embodiment of the present invention, the transceiver receives the first received signal and the second received signal in the first time slot and the second time slot, respectively, and the processor decodes the first received signal and the second received signal according to the decoding vector, and combines the first data information and the second data information obtained by decoding, so as to obtain the required data symbol. In this process, the second received signal includes a transmission signal of the second time slot sent by the D2D transmitting terminal and an amplified signal of the second time slot sent by the second D2D terminal, which are superimposed after channel fading and path loss; the second D2D terminal can effectively avoid extra load of the base station when serving as the relay, and meanwhile, because the second D2D terminal serves as the relay to transmit the amplified signal of the second time slot, channel expansion is achieved, and under such a condition, the first D2D terminal obtains the required data symbol after decoding processing by adopting the decoding processing in the above manner, so that the interference of cellular communication can be effectively avoided, and the interference resistance of D2D communication is improved.
Further, u satisfies the above formula (10).
Further, as can be seen from table 1 above, in order to determine the precoding vector v and the decoding vector u described above, the D2D transmitting end needs to obtain channel feedback information, and therefore the D2D receiving end also needs to perform corresponding steps, and specifically, the transceiver 401 is further configured to:
receiving a first pilot signal sent by the D2D transmitting terminal before receiving a first receiving signal in a first time slot, and determining h according to the first pilot signalSDH is saidSDChannel coefficients for the D2D transmitting terminals and the D2D receiving terminals;
receiving a second pilot signal sent by the second D2D terminal, and determining the h according to the second pilot signalSRhRDWherein the second pilot signal is obtained by amplifying the first pilot signal by the second D2D terminal;
receiving a third pilot signal sent by the second D2D terminal, and determining h according to the third pilot signalRDH is saidRDReceiving the second D2D terminal with the D2DChannel coefficients of the terminal;
sending feedback information to the D2D transmitting terminal, wherein the feedback information comprises the hSDH is describedRDAnd h is saidSRhRD。
When the general-purpose device is a relay, the general-purpose device has the following functions:
a transceiver 401, configured to receive a first received signal in a first time slot, where the first received signal is a received signal of a transmission signal of the first time slot sent by the D2D transmitting terminal after channel fading and path loss; transmitting the amplified signal of the second time slot to a first D2D terminal at the second time slot;
a processor 400, configured to amplify the first received signal to obtain an amplified signal of a second time slot.
The relay provided by the embodiment of the invention firstly takes the D2D terminal as the relay, which avoids unnecessary complexity added to the base station when the base station is used as the relay, and secondly, the transceiver receives the first receiving signal sent by the D2D transmitting terminal in the first time slot; the processor amplifies the first receiving signal to obtain an amplified signal of a second time slot; the transceiver transmits the amplified signal of the second time slot to the first D2D terminal in the second time slot. The processor only needs to perform simple power amplification processing on the received signal, so that additional signaling control is not needed while effective anti-interference decoding is guaranteed at a D2D receiving end due to effective channel expansion, and complexity of relay processing is reduced.
Further, the transceiver 401 is further configured to:
receiving a first pilot signal sent by the D2D transmitting terminal before receiving a first receiving signal in a first time slot, and determining h according to the first pilot signalSRH is saidSRTransmitting channel coefficients for the D2D transmitting terminal and the second D2D terminal;
transmitting the second pilot signal to the first D2D terminal;
transmitting a third pilot signal to the first D2D terminal;
the processor 400 is further configured to amplify the first pilot signal to obtain a second pilot signal.
With reference to the above and fig. 1, the present invention also provides a device-to-device communication system, comprising: the D2D transmitting terminal of fig. 2 or 5, the D2D receiving terminal of fig. 3 or 5, and the relay device of fig. 4 or 5. Further, the D2D transmitting terminal, the D2D receiving terminal, and the relay can achieve the functions and technical effects of the respective embodiments.
Fig. 6 is a flowchart of a device-to-device communication method according to an embodiment of the present invention, where an implementation subject of the method is a D2D transmitting terminal, the D2D transmitting terminal may adopt the structure shown in fig. 2 or fig. 5, and the D2D transmitting terminal may specifically be a user equipment, a vehicle-mounted communication device, and the like having a D2D communication function, and with reference to fig. 6, the method includes the following steps:
step 100, the D2D transmitting terminal pre-encodes the Data Symbol (Data Symbol) to be transmitted according to the pre-coding vector to obtain a transmission signal;
step 101, the D2D transmitting terminal respectively sends the transmission signals to a first D2D terminal and a second D2D terminal;
wherein the first D2D terminal is a receiving end of the transmission signal, and the second D2D terminal is a relay;
the expression of the precoding vector is as follows:
v＝[v1 v2]T
v is a precoding vector, v1Precoding vector elements employed in a first slot for the D2D transmitting terminal, the v2Precoding vector elements employed in a second time slot for the D2D transmitting terminal, the T representing a transpose of a vector;
v is1The expression of (a) is as follows:
Figure PCTCN2014090999-APPB-000093
v is2The expression of (a) is as follows:
wherein, the a1＝(dSD)-αhSDSaid b is1＝β(dSRdRD)-αhSRhRDSaidA ═ dCD)-αhCDWherein b is β (d)CRdRD)-αhCRhRDβ is the amplification factor of the second D2D terminal, DSDThe path distance of the D2D transmitting terminal from the first D2D terminal, the hSDFor the D2D transmitting terminal and the first D2D terminal's channel coefficients, the DSRFor the path distance of the D2D transmitting terminal from the second D2D terminal, the DRDThe path distance of the second D2D terminal from the first D2D terminal, the DCRThe path distance of the cellular terminal from the second D2D terminal, hSRFor the D2D transmitting terminal and the second D2D terminal's channel coefficients, the hRDThe h is a channel coefficient of the second D2D terminal and the first D2D terminalCRIs the channel coefficient of the cellular terminal and the second D2D terminal, the DCDThe path distance h is the distance between the cellular terminal and the first D2D terminalCDThe α represents a path loss exponent for the channel coefficients of the cellular terminal and the first D2D terminal.
In the device-to-device communication method provided by the embodiment of the present invention, a D2D transmitting terminal performs precoding processing on a data symbol to be transmitted according to a precoding vector, so as to obtain a transmission signal; the D2D transmitting terminal sends the transmission signal to a first D2D terminal and a second D2D terminal, respectively; because the precoding vector adopts the above-mentioned design mechanism, the D2D transmitting terminal sends the transmission signal obtained after the processing based on the precoding vector to the first D2D terminal, so that the first D2D terminal decodes the received signal received after the channel fading and path loss of the transmission signal based on the above-mentioned decoding vector, and can effectively avoid the interference of other cellular terminals. Also, since the D2D transmitting terminal transmits a transmission signal to the second D2D terminal as a relay in the embodiment of the present invention, it reduces the additional load of the base station of the same cell. And because the relay can help the single-antenna user network to form a virtual MIMO system, the channel expansion is effectively realized, and implementation conditions are provided for utilizing the precoding vector (or matrix) and the decoding vector (or matrix) provided above.
Further, as can be seen from the above, in one period, the D2D transmitting terminal sends transmission signals in two time slots, respectively, and therefore, the transmission signals include: a transmission signal of a first time slot and a transmission signal of a second time slot;
step 101 of fig. 6 includes:
step 101a, the D2D transmitting terminal sends the transmission signal of the first time slot to a first D2D terminal and a second D2D terminal respectively in the first time slot;
step 101b, the D2D transmitting terminal sending a transmission signal of the second slot to the first D2D terminal in the second slot;
wherein, the transmission signal expression of the first time slot is:
S1＝v1s
said S1The s is the data symbol, which is a transmission signal of the first time slot;
the transmission signal expression of the second time slot is as follows:
S2＝v2s
said S2Is a transmission signal of the second time slot.
As can be seen from the above, v satisfies the above formula (12).
The expression of u is referred to above in equation (11).
Further, before step 101, the method further includes: the D2D transmitting terminal selects any one of a plurality of D2D terminals in an idle state except the first D2D terminal as the second D2D terminal.
Further, in order to determine the precoding vector v and the decoding vector u as described above, the D2D is required to obtain channel feedback information at the transmitting end, so, with reference to table 1 above, on the basis of fig. 6, fig. 7 is a flowchart illustrating another device-to-device communication method provided by an embodiment of the present invention, and with reference to fig. 7, before step 100, the method further includes:
step 102, the D2D transmitting terminal sending pilot signals to the first D2D terminal and the second D2D terminal, respectively;
the purpose of step 102 is to: so that the first D2D terminal determines the h according to the pilot signalSDSo that the second D2D terminal determines the h according to the pilot signalSR；
103, the D2D transmitting terminal receiving the feedback information sent by the first D2D terminal;
wherein the feedback information comprises the hSDH is describedRDAnd h is saidSRhRD。
Fig. 8 is a flowchart illustrating another device-to-device communication method according to an embodiment of the present invention, where an execution subject of the method is a D2D receiving end (i.e., a first D2D terminal), and the D2D receiving end may adopt the structure shown in fig. 3 or fig. 5, and referring to fig. 8, the method includes the following steps:
step 200, a first D2D terminal receives a first received signal in a first time slot, where the first received signal is a received signal of a transmission signal of the first time slot sent by the D2D transmitting terminal after channel fading and path loss;
step 201, the first D2D terminal performs decoding processing on the first received signal according to a decoding vector to obtain first data information;
step 202, the first D2D terminal receives a second received signal in a second time slot;
specifically, the second received signal is obtained by superimposing a transmission signal of a second time slot sent by the D2D transmitting terminal and an amplified signal of the second time slot sent by a second D2D terminal after channel fading and path loss;
the second D2D terminal is a relay, and the amplified signal of the second time slot is obtained by amplifying the transmission signal of the first time slot sent by the D2D transmitting terminal by the second D2D terminal;
step 203, the first D2D terminal performs decoding processing on the second received signal according to the decoding vector to obtain second data information;
step 204, the first D2D terminal combines the first data information and the second data information to obtain a data symbol;
wherein the decoding vector has the following expression:
u＝[u1 u2]T
the u is a decoding vector, the u1A decoding vector element of a first time slot, configured to perform decoding processing on the first received signal to obtain the first data information; said u is2A decoding vector element of a second slot, configured to perform decoding processing on the second received signal to obtain the second data information, where T represents a transpose of a vector;
said u is1The expression of (a) is as follows:
Figure PCTCN2014090999-APPB-000096
said u is1The expression of (a) is as follows:
Figure PCTCN2014090999-APPB-000097
wherein, the
Figure PCTCN2014090999-APPB-000098
A ═ dCD)-αhCDWherein b is β (d)CRdRD)-αhCRhRDD is saidCDThe path distance h is the distance between the cellular terminal and the first D2D terminalCDIs the channel coefficient of the cellular terminal and the first D2D terminal, the DRDThe path distance of the second D2D terminal from the first D2D terminal, the DCRDistance of path for cellular terminal from said second D2D terminalH is saidRDThe h is a channel coefficient of the second D2D terminal and the first D2D terminalCRThe α represents a path loss exponent for the channel coefficients of the cellular terminal and the second D2D terminal.
In the device-to-device communication method provided by the embodiment of the present invention, the first D2D terminal receives the first received signal and the second received signal in the first time slot and the second time slot, respectively, and performs decoding processing on the first received signal and the second received signal according to the decoding vectors, and combines the first data information and the second data information obtained by the decoding processing to obtain the required data symbol. In this process, the second received signal includes a transmission signal of the second time slot sent by the D2D transmitting terminal and an amplified signal of the second time slot sent by the second D2D terminal, which are superimposed after channel fading and path loss; the second D2D terminal can effectively avoid extra load of the base station when serving as the relay, and meanwhile, because the second D2D terminal serves as the relay to transmit the amplified signal of the second time slot, channel expansion is achieved, and under such a condition, the first D2D terminal obtains the required data symbol after decoding processing by adopting the decoding processing in the above manner, so that the interference of cellular communication can be effectively avoided, and the interference resistance of D2D communication is improved.
Further, u satisfies the above formula (10).
Further, as can be seen from table 1 above, in order to determine the precoding vector v and the decoding vector u described above, the D2D transmitting end needs to obtain channel feedback information, and therefore the first D2D terminal serving as the D2D receiving end also needs to perform corresponding steps, on the basis of fig. 8, fig. 9 is a schematic flow chart of another device-to-device communication method provided by the embodiment of the present invention, and before step 200, the method further includes:
step 205, the first D2D terminal receives the first pilot signal sent by the D2D transmitting terminal and determines h according to the first pilot signalSD。
Wherein, the hSDTransmitting channel coefficients for the D2D transmitting terminals with the first D2D terminal;
step 206, the first D2D terminal receiving the second D2D terminal transmissionAnd determining said h from the second pilot signalSRhRD。
The second pilot signal is obtained by amplifying the first pilot signal by the second D2D terminal;
step 207, the first D2D terminal receives the third pilot signal sent by the second D2D terminal, and determines h according to the third pilot signalRD；
Wherein, the hRDChannel coefficients for the second D2D terminal and the first D2D terminal;
step 208, the first D2D terminal sending feedback information to the D2D transmitting terminal, the feedback information including the hSDH is describedRDAnd h is saidSRhRD。
Fig. 10 is a flowchart illustrating another device-to-device communication method according to an embodiment of the present invention, where an execution subject of the method is a D2D terminal (i.e., a second D2D terminal) serving as a relay, and the relay may adopt the structure shown in fig. 4 or fig. 5, with reference to fig. 10, where the method includes the following steps:
step 300, the second D2D terminal receives a first received signal in a first time slot, where the first received signal is a received signal of a transmission signal of the first time slot sent by the D2D transmitting terminal after channel fading and path loss;
step 301, the second D2D terminal amplifies the first received signal to obtain an amplified signal of a second time slot;
step 302, the second D2D terminal transmitting the amplified signal of the second slot to the first D2D terminal in the second slot.
The device-to-device communication method provided by the embodiment of the invention firstly takes the D2D terminal as the relay, which avoids the unnecessary complexity added to the base station when the base station is used as the relay, and secondly, the second D2D terminal as the relay receives the first receiving signal sent by the D2D transmitting terminal in the first time slot; amplifying the first receiving signal to obtain an amplified signal of a second time slot; and then transmits the amplified signal of the second time slot to the first D2D terminal in the second time slot. The second D2D terminal only needs to perform simple power amplification on the received signal, so that additional signaling control is not needed while effective channel expansion is effectively achieved to ensure effective anti-interference decoding at the D2D receiving end, thereby reducing the complexity of relay processing.
Further, referring to table 1, in order to determine the precoding vector v and the decoding vector u described above, the D2D transmitting end needs to obtain channel feedback information, and a corresponding second D2D terminal serving as a relay also needs to perform corresponding steps, on the basis of fig. 10, fig. 11 is a schematic flow chart of another device-to-device communication method provided by the embodiment of the present invention, and before step 300, the method further includes:
step 303, the second D2D terminal receives the first pilot signal sent by the D2D transmitting terminal, and determines h according to the first pilot signalSR；
Wherein, the hSRTransmitting channel coefficients for the D2D transmitting terminal and the second D2D terminal;
step 304, the second D2D terminal amplifies the first pilot signal to obtain a second pilot signal, and sends the second pilot signal to the first D2D terminal;
step 305, the second D2D terminal transmitting a third pilot signal to the first D2D terminal.
The effect of the scheme provided by the above embodiment of the present invention is simulated through a specific scenario.
The present invention contemplates a D2D communication system in a cellular network, the network comprising 1 base station, 1 cellular terminal, 1D 2D communication pair and one relay. Assuming that all channel coefficients are subjected to independent complex Gaussian distribution with same distribution and zero mean and unit variance, the cellular terminal, the D2D terminal and the relay terminal are all configured with a single antenna. The key simulation parameters are shown in table 2:
TABLE 2 simulation parameters
Figure PCTCN2014090999-APPB-000099
Fig. 12 is a diagram illustrating SINR for the case where different schemes are based on full CSI, referring to fig. 12, and the spectrum orthogonal scheme (D2D communication occupies different spectrum resources from cellular communication), least mean squareCompared with an Error (MMSE for short) receiving scheme (the MMSE receiving mode is adopted by a D2D receiving terminal), because the relay is added as the assistance of channel expansion, the relay transmitting power P is assumed for the fairness of performance comparisonRTransmitting terminal power P with D2DSEqual and the sum of the two powers is equal to the transmission power P of the cellular terminalCI.e. by
Figure PCTCN2014090999-APPB-000100
As can be seen from fig. 12, the solution provided by the embodiment of the present invention can significantly improve the SINR of the D2D receiving terminal. For example, when the ratio of the cellular terminal transmission power to the noise power is 20dB, the SINR gain of the scheme provided by the embodiment of the present invention can reach 39.07% compared with the spectrum orthogonal scheme, and the SINR gain of the scheme provided by the embodiment of the present invention can reach 44.45% compared with the MMSE receiving scheme.
It should be noted that, because there is an error in the feedback value of the Channel gain (CSI for short) of the D2D transmitting terminal, the actually obtained precoding vector v will be different from the above-obtained result, and therefore, in order to understand the performance influence of the CSI error on the scheme provided by the embodiment of the present invention, the following analysis and simulation are performed.
Here, a random error (SE) model is used, in which the channel state information error follows an independent complex gaussian distribution. Based on the SE model, the actual full csi (approximate csi) obtained by the D2D transmitting end can be expressed as
Figure PCTCN2014090999-APPB-000101
Wherein h isABIs the complete CSI between terminal A and terminal B, eABIs a CSI error variable, assuming eABObedience mean 0 and variance
Figure PCTCN2014090999-APPB-000102
Independent complex gaussian distributions. Specific impact on SINR Performance with respect to feedback CSI error variablesDetailed results are given below by simulation, with σ in FIG. 13eFig. 14 is a SINR diagram comparing the scheme provided by the embodiment of the present invention with other schemes under the condition of incomplete CSI. Referring to FIG. 13, the standard deviation σ of the feedback CSI error variable is showneThe performance of the scheme provided by the embodiment of the invention is affected. Wherein the ratio of the cellular terminal transmission power to the noise power is 15dB,
Figure PCTCN2014090999-APPB-000103
as can be seen from FIG. 13, as σ is increasedeIn addition, the SINR performance of the solution provided by the embodiment of the present invention may be degraded to a certain extent, for example, when σ is increasedeAt 0.5, the performance loss of the algorithm is about 8.79%. Although the feedback CSI error may affect the scheme provided by the embodiment of the present invention, compared with the spectrum orthogonal scheme and the MMSE receiving scheme, the scheme provided by the embodiment of the present invention can still obtain a significant SINR gain under the incomplete CSI, as shown in fig. 14, which shows SINR of a D2D receiving terminal under different schemes. Wherein the content of the first and second substances,
Figure PCTCN2014090999-APPB-000104
σetake 0.1 and 0.5, respectively. As can be seen from fig. 14, when the ratio of the cellular terminal transmission power to the noise power is large, the scheme provided by the embodiment of the present invention is at σeIn the presence of this, significant SINR performance gain can still be obtained compared to the spectrum orthogonal scheme and MMSE reception scheme. That is, when the SINR of the scheme provided by the embodiment of the present invention is compared with the SINR of other schemes in the case of complete CSI in the case of incomplete CSI, there is still an obvious SINR performance gain. For example, when the ratio of the cellular terminal transmission power to the noise power is 20dB, the SINR gain obtained by the scheme provided by the embodiment of the present invention is 37.97% (σ), compared with the spectrum orthogonal schemee＝0.1)、26.88％(σe0.5), the SINR gain obtained by the scheme provided by the embodiment of the present invention is 43.34% compared with the MMSE receiving scheme(σe＝0.1)、31.82％(σe＝0.5)。
Further, fig. 15 is a schematic diagram of Bit Error rates of D2D communication under different schemes, and fig. 15 shows Bit Error rates (Bit Error rates, abbreviated as BER) of D2D communication under different schemes. Wherein each terminal transmit power sum sigmaeThe parameter settings of (2) are the same as those of fig. 14. As can be seen from fig. 15, when the ratio of the cellular terminal transmission power to the noise power is large, the BER is significantly reduced compared to the spectrum orthogonal scheme and the MMSE receiving scheme provided by the embodiment of the present invention. And with sigmaeThe BER performance is affected to some extent, for example, when the ratio of the cellular terminal transmission power to the noise power is 20dB, the performance loss of the scheme provided by the embodiment of the present invention is about 6.73% (σ)e＝0.3)、15.91％(σe0.5). Although sigmaeThe BER performance is influenced, but compared with the spectrum orthogonal scheme and the MMSE receiving scheme, the BER performance gain obtained by the scheme provided by the embodiment of the invention is still obvious even if the sigma is largereIn the case of 0.5, the BER gain obtained by the scheme provided by the embodiment of the present invention still reaches 30.11% (compared with the spectrum orthogonal scheme) and 33.47% (compared with the MMSE receiving scheme).
Those of ordinary skill in the art will understand that: all or part of the steps for implementing the method embodiments may be implemented by hardware related to program instructions, and the program may be stored in a computer readable storage medium, and when executed, the program performs the steps including the method embodiments; and the aforementioned storage medium includes: various media that can store program codes, such as ROM, RAM, magnetic or optical disks.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims (34)

  1. A D2D transmitting terminal, comprising:
    the processing module is used for carrying out pre-coding processing on the data symbols to be sent according to the pre-coding vectors to obtain transmission signals;
    a transceiving module for transmitting the transmission signals to a first D2D terminal and a second D2D terminal, respectively;
    wherein the first D2D terminal is a receiving end of the transmission signal, and the second D2D terminal is a relay;
    the expression of the precoding vector is as follows:
    v＝[v1 v2]T
    v is a precoding vector, v1Precoding vector elements employed in a first slot for the D2D transmitting terminal, the v2Precoding vector elements employed in a second time slot for the D2D transmitting terminal, the T representing a transpose of a vector;
    v is1The expression of (a) is as follows:
    Figure PCTCN2014090999-APPB-100001
    v is2The expression of (a) is as follows:
    Figure PCTCN2014090999-APPB-100002
    wherein, the a1＝(dSD)-αhSDSaid b is1＝β(dSRdRD)-αhSRhRDSaid
    Figure PCTCN2014090999-APPB-100003
    A ═ dCD)-αhCDWherein b is β (d)CRdRD)-αhCRhRDβ is the amplification factor of the second D2D terminal, DSDThe path distance of the D2D transmitting terminal from the first D2D terminal, the hSDFor the D2D transmitting terminal and the first D2D terminal's channel coefficients, the DSRFor the path distance of the D2D transmitting terminal from the second D2D terminal, the DRDThe path distance of the second D2D terminal from the first D2D terminal, the DCRThe path distance of the cellular terminal from the second D2D terminal, hSRFor the D2D transmitting terminal and the second D2D terminal's channel coefficients, the hRDThe h is a channel coefficient of the second D2D terminal and the first D2D terminalCRIs the channel coefficient of the cellular terminal and the second D2D terminal, the DCDThe path distance h is the distance between the cellular terminal and the first D2D terminalCDThe α represents a path loss exponent for the channel coefficients of the cellular terminal and the first D2D terminal.
  2. The D2D transmitting terminal of claim 1, wherein the transmission signal comprises: a transmission signal of a first time slot and a transmission signal of a second time slot;
    the transceiver module is specifically configured to send the transmission signal of the first time slot to a first D2D terminal and a second D2D terminal in the first time slot, respectively; transmitting a transmission signal of the second time slot to the first D2D terminal in the second time slot;
    wherein, the transmission signal expression of the first time slot is:
    S1＝v1s
    said S1The s is the data symbol, which is a transmission signal of the first time slot;
    the transmission signal expression of the second time slot is as follows:
    S2＝v2s
    the above-mentionedS2Is a transmission signal of the second time slot.
  3. The D2D transmitting terminal of claim 1 or 2, wherein v satisfies the following equation:
    Figure PCTCN2014090999-APPB-100004
    wherein, said emaxRepresenting the eigenvector corresponding to the largest eigenvalue of the matrix, saidThe H represents the conjugate transpose and the u is the decoded vector.
  4. The D2D transmitting terminal of claim 3, wherein u is expressed as follows:
  5. the D2D transmitting terminal of any one of claims 1-4, wherein the processing module is further configured to select any one of a plurality of D2D terminals in idle state except the first D2D terminal as the second D2D terminal before the transceiving module sends the transmission signal to the first D2D terminal and the second D2D terminal, respectively.
  6. The D2D transmitting terminal of any of claims 1-5, wherein the transceiver module is further configured to:
    dividing the data symbols to be sent into a plurality of data symbols before the processing module carries out pre-coding processing on the data symbols to be sent according to the pre-coding vectors to obtain transmission signalsTransmitting pilot signals to the first D2D terminal and the second D2D terminal, respectively, such that the first D2D terminal determines the h according to the pilot signalsSDSo that the second D2D terminal determines the h according to the pilot signalSR；
    Receiving feedback information sent by the first D2D terminal, wherein the feedback information includes the hSDH is describedRDAnd h is saidSRhRD。
  7. A D2D receiving terminal, comprising:
    a transceiver module, configured to receive a first received signal in a first time slot, where the first received signal is a received signal after channel fading and path loss of a transmission signal of the first time slot sent by the D2D transmitting terminal; receiving a second received signal in a second time slot, where the second received signal is formed by superimposing a transmission signal in the second time slot sent by the D2D transmitting terminal and an amplified signal in the second time slot sent by a second D2D terminal after channel fading and path loss;
    the processing module is used for decoding the first receiving signal according to the decoding vector to obtain first data information; decoding the second receiving signal according to the decoding vector to obtain second data information; combining the first data information and the second data information to obtain a data symbol;
    the second D2D terminal is a relay, and the amplified signal of the second time slot is obtained by amplifying the transmission signal of the first time slot sent by the D2D transmitting terminal by the second D2D terminal; the expression of the decoding vector is as follows:
    u＝[u1 u2]T
    the u is a decoding vector, the u1A decoding vector element of a first time slot, configured to perform decoding processing on the first received signal to obtain the first data information; said u is2A decoding vector element of a second slot, configured to perform decoding processing on the second received signal to obtain the second data information, where T represents a transpose of a vector;
    said u is1The expression of (a) is as follows:
    Figure PCTCN2014090999-APPB-100007
    said u is1The expression of (a) is as follows:
    Figure PCTCN2014090999-APPB-100008
    wherein, the
    Figure PCTCN2014090999-APPB-100009
    A ═ dCD)-αhCDWherein b is β (d)CRdRD)-αhCRhRDD is saidCDThe path distance h for a cellular terminal to the D2D receiving terminalCDChannel coefficients for the cellular terminal and the D2D receiving terminal, DRDFor the path distance of the second D2D terminal from the D2D receiving terminal, the DCRThe path distance of the cellular terminal from the second D2D terminal, hRDThe h is a channel coefficient of the second D2D terminal and the first D2D terminalCRThe α represents a path loss exponent for the channel coefficients of the cellular terminal and the second D2D terminal.
  8. The D2D receiving terminal of claim 7, wherein u satisfies the following equation:
    Figure PCTCN2014090999-APPB-100010
    wherein, said emaxRepresenting the eigenvector corresponding to the largest eigenvalue of the matrix, saidThe H represents the conjugate transpose.
  9. The D2D receiving terminal according to claim 7 or 8, wherein the transceiver module is further configured to: receiving a first pilot signal sent by the D2D transmitting terminal before receiving a first receiving signal in a first time slot, and determining h according to the first pilot signalSDH is saidSDChannel coefficients for the D2D transmitting terminals and the D2D receiving terminals;
    receiving a second pilot signal sent by the second D2D terminal, and determining the h according to the second pilot signalSRhRDWherein the second pilot signal is obtained by amplifying the first pilot signal by the second D2D terminal;
    receiving a third pilot signal sent by the second D2D terminal, and determining h according to the third pilot signalRDH is saidRDChannel coefficients for the second D2D terminal and the D2D receiving terminals;
    sending feedback information to the D2D transmitting terminal, wherein the feedback information comprises the hSDH is describedRDAnd h is saidSRhRD。
  10. A relay, characterized in that the relay is a D2D terminal, comprising:
    a transceiver module, configured to receive a first received signal in a first time slot, where the first received signal is a received signal of a transmission signal of the first time slot sent by the D2D transmitting terminal after channel fading and path loss; transmitting the amplified signal of the second time slot to a first D2D terminal at the second time slot;
    and the amplifying module is used for amplifying the first receiving signal to obtain an amplified signal of a second time slot.
  11. The relay according to claim 10, wherein the transceiver module is further configured to: receiving a first pilot signal sent by the D2D transmitting terminal before receiving a first receiving signal in a first time slot, and determining h according to the first pilot signalSRH is saidSRTransmitting channel coefficients for the D2D transmitting terminal and the second D2D terminal;
    transmitting the second pilot signal to the first D2D terminal;
    the second D2D terminal transmitting a third pilot signal to the first D2D terminal;
    the amplifying module is further configured to amplify the first pilot signal to obtain a second pilot signal.
  12. A D2D transmitting terminal, comprising:
    the processor is used for pre-coding the data symbols to be sent according to the pre-coding vectors to obtain transmission signals;
    a transceiver for transmitting the transmission signals to a first D2D terminal and a second D2D terminal, respectively;
    wherein the first D2D terminal is a receiving end of the transmission signal, and the second D2D terminal is a relay;
    the expression of the precoding vector is as follows:
    v＝[v1 v2]T
    v is a precoding vector, v1Precoding vector elements employed in a first slot for the D2D transmitting terminal, the v2Precoding vector elements employed in a second time slot for the D2D transmitting terminal, the T representing a transpose of a vector;
    v is1The expression of (a) is as follows:
    Figure PCTCN2014090999-APPB-100012
    the above-mentionedv2The expression of (a) is as follows:
    Figure PCTCN2014090999-APPB-100013
    wherein, the a1＝(dSD)-αhSDSaid b is1＝β(dSRdRD)-αhSRhRDSaid
    Figure PCTCN2014090999-APPB-100014
    A ═ dCD)-αhCDWherein b is β (d)CRdRD)-αhCRhRDβ is the amplification factor of the second D2D terminal, DSDThe path distance of the D2D transmitting terminal from the first D2D terminal, the hSDFor the D2D transmitting terminal and the first D2D terminal's channel coefficients, the DSRFor the path distance of the D2D transmitting terminal from the second D2D terminal, the DRDThe path distance of the second D2D terminal from the first D2D terminal, the DCRThe path distance of the cellular terminal from the second D2D terminal, hSRFor the D2D transmitting terminal and the second D2D terminal's channel coefficients, the hRDThe h is a channel coefficient of the second D2D terminal and the first D2D terminalCRIs the channel coefficient of the cellular terminal and the second D2D terminal, the DCDThe path distance h is the distance between the cellular terminal and the first D2D terminalCDThe α represents a path loss exponent for the channel coefficients of the cellular terminal and the first D2D terminal.
  13. The D2D transmitting terminal of claim 12, wherein the transmission signal comprises: a transmission signal of a first time slot and a transmission signal of a second time slot;
    the transceiver is specifically configured to transmit the transmission signal of the first time slot to a first D2D terminal and a second D2D terminal, respectively, in the first time slot; transmitting a transmission signal of the second time slot to the first D2D terminal in the second time slot;
    wherein, the transmission signal expression of the first time slot is:
    S1＝v1s
    said S1The s is the data symbol, which is a transmission signal of the first time slot;
    the transmission signal expression of the second time slot is as follows:
    S2＝v2s
    said S2Is a transmission signal of the second time slot.
  14. The D2D transmitting terminal of claim 12 or 13, wherein v satisfies the following equation:
    Figure PCTCN2014090999-APPB-100015
    wherein, said emaxRepresenting the eigenvector corresponding to the largest eigenvalue of the matrix, saidThe H represents the conjugate transpose and the u is the decoded vector.
    Figure PCTCN2014090999-APPB-100016
  15. The D2D transmitting terminal of claim 14, wherein u is expressed as follows:
    Figure PCTCN2014090999-APPB-100017
  16. the D2D transmitting terminal of any of claims 12-15, wherein the processor is further configured to select any one of the plurality of D2D terminals in an idle state except the first D2D terminal as the second D2D terminal before the transceiver sends the transmission signals to the first D2D terminal and the second D2D terminal, respectively.
  17. The D2D transmitting terminal of any of claims 12-16, wherein the transceiver is further configured to:
    before the processor performs precoding processing on data symbols to be transmitted according to precoding vectors to obtain transmission signals, pilot signals are respectively transmitted to the first D2D terminal and the second D2D terminal, so that the first D2D terminal determines the h according to the pilot signalsSDSo that the second D2D terminal determines the h according to the pilot signalSR；
    Receiving feedback information sent by the first D2D terminal, wherein the feedback information includes the hSDH is describedRDAnd h is saidSRhRD。
  18. A D2D receiving terminal, comprising:
    a transceiver, configured to receive a first received signal in a first time slot, where the first received signal is a received signal after channel fading and path loss of a transmission signal of the first time slot sent by the D2D transmitting terminal; receiving a second received signal in a second time slot, where the second received signal is formed by superimposing a transmission signal in the second time slot sent by the D2D transmitting terminal and an amplified signal in the second time slot sent by a second D2D terminal after channel fading and path loss;
    the processor is used for decoding the first receiving signal according to the decoding vector to obtain first data information; decoding the second receiving signal according to the decoding vector to obtain second data information; combining the first data information and the second data information to obtain a data symbol;
    the second D2D terminal is a relay, and the amplified signal of the second time slot is obtained by amplifying the transmission signal of the first time slot sent by the D2D transmitting terminal by the second D2D terminal; the expression of the decoding vector is as follows:
    u＝[u1 u2]T
    the u is a decoding vector, the u1A decoding vector element of a first time slot, configured to perform decoding processing on the first received signal to obtain the first data information; said u is2A decoding vector element of a second slot, configured to perform decoding processing on the second received signal to obtain the second data information, where T represents a transpose of a vector;
    said u is1The expression of (a) is as follows:
    Figure PCTCN2014090999-APPB-100018
    said u is1The expression of (a) is as follows:
    Figure PCTCN2014090999-APPB-100019
    wherein, theA ═ dCD)-αhCDWherein b is β (d)CRdRD)-αhCRhRDD is saidCDThe path distance h for a cellular terminal to the D2D receiving terminalCDChannel coefficients for the cellular terminal and the D2D receiving terminal, DRDFor the path distance of the second D2D terminal from the D2D receiving terminal, the DCRThe path distance of the cellular terminal from the second D2D terminal, hRDIs a stand forChannel coefficients of the second D2D terminal and the first D2D terminal, the hCRThe α represents a path loss exponent for the channel coefficients of the cellular terminal and the second D2D terminal.
  19. The D2D receiving terminal of claim 18, wherein u satisfies the following equation:
    Figure PCTCN2014090999-APPB-100021
    wherein, said emaxRepresenting the eigenvector corresponding to the largest eigenvalue of the matrix, saidThe H represents the conjugate transpose.
    Figure PCTCN2014090999-APPB-100022
  20. The D2D receiving terminal of claim 18 or 19, wherein the transceiver is further configured to: receiving a first pilot signal sent by the D2D transmitting terminal before receiving a first receiving signal in a first time slot, and determining h according to the first pilot signalSDH is saidSDChannel coefficients for the D2D transmitting terminals and the D2D receiving terminals;
    receiving a second pilot signal sent by the second D2D terminal, and determining the h according to the second pilot signalSRhRDWherein the second pilot signal is obtained by amplifying the first pilot signal by the second D2D terminal;
    receiving a third pilot signal sent by the second D2D terminal, and determining h according to the third pilot signalRDH is saidRDChannel coefficients for the second D2D terminal and the D2D receiving terminals;
    sending feedback information to the D2D transmitting terminal, wherein the feedback information comprises the hSDH is describedRDAnd h is saidSRhRD。
  21. A relay, wherein the relay device is a D2D terminal, comprising:
    a transceiver, configured to receive a first received signal in a first time slot, where the first received signal is a received signal of a transmission signal of the first time slot sent by the D2D transmitting terminal after channel fading and path loss; transmitting the amplified signal of the second time slot to a first D2D terminal at the second time slot;
    and the processor is used for amplifying the first receiving signal to obtain an amplified signal of a second time slot.
  22. The relay device of claim 21, wherein the transceiver is further configured to: receiving a first pilot signal sent by the D2D transmitting terminal before receiving a first receiving signal in a first time slot, and determining h according to the first pilot signalSRH is saidSRTransmitting channel coefficients for the D2D transmitting terminal and the second D2D terminal;
    transmitting the second pilot signal to the first D2D terminal;
    the second D2D terminal transmitting a third pilot signal to the first D2D terminal;
    the processor is further configured to amplify the first pilot signal to obtain a second pilot signal.
  23. A device-to-device communication system, comprising: at least one D2D transmitting terminal of any one of claims 1-6, at least one D2D receiving terminal of any one of claims 7-9, and a relay of claim 10 or 11.
  24. A device-to-device communication method, comprising:
    the D2D transmitting terminal carries out pre-coding processing on the data symbol to be transmitted according to the pre-coding vector to obtain a transmission signal;
    the D2D transmitting terminal sends the transmission signal to a first D2D terminal and a second D2D terminal, respectively;
    wherein the first D2D terminal is a receiving end of the transmission signal, and the second D2D terminal is a relay;
    the expression of the precoding vector is as follows:
    v＝[v1 v2]T
    v is a precoding vector, v1Precoding vector elements employed in a first slot for the D2D transmitting terminal, the v2Precoding vector elements employed in a second time slot for the D2D transmitting terminal, the T representing a transpose of a vector;
    v is1The expression of (a) is as follows:
    Figure PCTCN2014090999-APPB-100023
    v is2The expression of (a) is as follows:
    Figure PCTCN2014090999-APPB-100024
    wherein, the a1＝(dSD)-αhSDSaid b is1＝β(dSRdRD)-αhSRhRDSaid
    Figure PCTCN2014090999-APPB-100025
    A ═ dCD)-αhCDWherein b is β (d)CRdRD)-αhCRhRDβ is the amplification factor of the second D2D terminal, DSDThe path distance of the D2D transmitting terminal from the first D2D terminal, the hSDFor the D2D transmitting terminal and the first D2D terminal's channel coefficients, the DSRIs said D2Distance of path of D transmitting terminal from said second D2D terminal, said DRDThe path distance of the second D2D terminal from the first D2D terminal, the DCRThe path distance of the cellular terminal from the second D2D terminal, hSRFor the D2D transmitting terminal and the second D2D terminal's channel coefficients, the hRDThe h is a channel coefficient of the second D2D terminal and the first D2D terminalCRIs the channel coefficient of the cellular terminal and the second D2D terminal, the DCDThe path distance h is the distance between the cellular terminal and the first D2D terminalCDThe α represents a path loss exponent for the channel coefficients of the cellular terminal and the first D2D terminal.
  25. The method of claim 24, wherein transmitting the signal comprises: a transmission signal of a first time slot and a transmission signal of a second time slot;
    the D2D transmitting terminal respectively transmits the transmission signals to a first D2D terminal and a second D2D terminal, including:
    the D2D transmitting terminal sending the transmission signal of the first time slot to a first D2D terminal and a second D2D terminal, respectively, in the first time slot;
    the D2D transmitting terminal sending a transmission signal for the second slot in the second slot to a first D2D terminal;
    wherein, the transmission signal expression of the first time slot is:
    S1＝v1s
    said S1The s is the data symbol, which is a transmission signal of the first time slot;
    the transmission signal expression of the second time slot is as follows:
    S2＝v2s
    said S2Is a transmission signal of the second time slot.
  26. The method of claim 24 or 25, wherein v satisfies the following equation:
    Figure PCTCN2014090999-APPB-100026
    wherein, said emaxRepresenting the eigenvector corresponding to the largest eigenvalue of the matrix, saidThe H represents the conjugate transpose and the u is the decoded vector.
    Figure PCTCN2014090999-APPB-100027
  27. The method of claim 26, wherein u is expressed as follows:
    Figure PCTCN2014090999-APPB-100028
  28. the method of any of claims 24-27, further comprising, before the D2D transmitting terminal sends the transmission signal to a first D2D terminal and a second D2D terminal, respectively:
    the D2D transmitting terminal selects any one of a plurality of D2D terminals in an idle state except the first D2D terminal as the second D2D terminal.
  29. The method according to any of claims 24-28, wherein before the D2D transmitting terminal precoding data symbols to be transmitted according to a precoding vector to obtain a transmission signal, the method further comprises:
    the D2D transmitting terminal sends pilot signals to the first D2D terminal and the second D2D terminal, respectively, to cause the first D2D terminal to determine the h from the pilot signalsSDSo that the second D2D terminal determines the h according to the pilot signalSR；
    The D2D transmitting terminal receiving feedback information sent by the first D2D terminal, the feedback information including the hSDH is describedRDAnd h is saidSRhRD。
  30. A device-to-device communication method, comprising:
    a first D2D terminal receives a first received signal in a first time slot, wherein the first received signal is a received signal of a transmission signal of the first time slot sent by the D2D transmitting terminal after channel fading and path loss;
    the first D2D terminal decodes the first received signal according to the decoding vector to obtain first data information;
    the first D2D terminal receives a second received signal in a second time slot, where the second received signal is formed by superimposing a transmission signal in the second time slot sent by the D2D transmitting terminal and an amplified signal in the second time slot sent by the second D2D terminal after channel fading and path loss;
    the second D2D terminal is a relay, and the amplified signal of the second time slot is obtained by amplifying the transmission signal of the first time slot sent by the D2D transmitting terminal by the second D2D terminal;
    the first D2D terminal decodes the second received signal according to the decoding vector to obtain second data information;
    the first D2D terminal combines the first data information and the second data information to obtain a data symbol;
    wherein the decoding vector has the following expression:
    u＝[u1 u2]T
    the u is a decoding vector, the u1A decoding vector element of a first time slot, configured to perform decoding processing on the first received signal to obtain the first data information; said u is2A decoding vector element of a second slot, configured to perform decoding processing on the second received signal to obtain the second data information, where T represents a transpose of a vector;
    said u is1The expression of (a) is as follows:
    Figure PCTCN2014090999-APPB-100029
    said u is1The expression of (a) is as follows:
    Figure PCTCN2014090999-APPB-100030
    wherein, the
    Figure PCTCN2014090999-APPB-100031
    A ═ dCD)-αhCDWherein b is β (d)CRdRD)-αhCRhRDD is saidCDThe path distance h is the distance between the cellular terminal and the first D2D terminalCDIs the channel coefficient of the cellular terminal and the first D2D terminal, the DRDThe path distance of the second D2D terminal from the first D2D terminal, the DCRThe path distance of the cellular terminal from the second D2D terminal, hRDThe h is a channel coefficient of the second D2D terminal and the first D2D terminalCRThe α represents a path loss exponent for the channel coefficients of the cellular terminal and the second D2D terminal.
  31. The method of claim 30, wherein u satisfies the following equation:
    Figure PCTCN2014090999-APPB-100032
    wherein, said emaxRepresenting the eigenvector corresponding to the largest eigenvalue of the matrix, saidThe H represents the conjugate transpose.
    Figure PCTCN2014090999-APPB-100033
  32. The method according to claim 30 or 31, wherein before the first D2D terminal receives the first received signal in the first time slot, the method further comprises:
    the first D2D terminal receives the first pilot signal sent by the D2D transmitting terminal and determines h from the first pilot signalSDH is saidSDTransmitting channel coefficients for the D2D transmitting terminals with the first D2D terminal;
    the first D2D terminal receives the second pilot signal transmitted by the second D2D terminal and determines the h according to the second pilot signalSRhRDWherein the second pilot signal is obtained by amplifying the first pilot signal by the second D2D terminal;
    the first D2D terminal receives a third pilot signal transmitted by the second D2D terminal and determines h according to the third pilot signalRDH is saidRDChannel coefficients for the second D2D terminal and the first D2D terminal;
    the first D2D terminal sending feedback information to the D2D transmitting terminal, the feedback information including the hSDH is describedRDAnd h is saidSRhRD。
  33. A device-to-device communication method, comprising:
    a second D2D terminal receives a first received signal in a first time slot, wherein the first received signal is a received signal of a transmission signal of the first time slot sent by the D2D transmitting terminal after channel fading and path loss;
    the second D2D terminal amplifies the first received signal to obtain an amplified signal of a second time slot;
    the second D2D terminal transmits the amplified signal of the second slot to the first D2D terminal in the second slot.
  34. The method of claim 33, wherein before the second D2D terminal receives the first received signal in the first time slot, further comprising:
    the second D2D terminal receives the first pilot signal sent by the D2D transmitting terminal and determines h according to the first pilot signalSRH is saidSRTransmitting channel coefficients for the D2D transmitting terminal and the second D2D terminal;
    the second D2D terminal amplifies the first pilot signal to obtain a second pilot signal, and sends the second pilot signal to the first D2D terminal;
    the second D2D terminal transmits a third pilot signal to the first D2D terminal.
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