CN101873161A - Virtual MIMO (Multiple Input Multiple Output) relay transmission method and system based on cluster user cooperation - Google Patents

Abstract

The invention discloses virtual MIMO (Multiple Input Multiple Output) relay transmission method and system based on cluster user cooperation. The method comprises the following steps of: dividing a plurality of user terminals adjacent in space into a cluster according to the distribution condition of the user terminals in cells by taking a virtual MIMO transmission technology between each user terminal and a base station, wherein each cell includes a plurality of clusters; modeling a channel between every two user terminals in the cluster to form a Ricean channel; modeling a channel between each user terminal and the base station to form a multipath reyleigh fading channel; and enabling two user terminals in the same cluster to mutually cooperate so as to finish the information transmission from each user terminal to the base station within three time slots. The system comprises the plurality of user terminals and the base station communicated with the plurality of user terminals, wherein clusters formed by the plurality of adjacent user terminals are mutually cooperated to finish the information transmission from each user terminal to the base station within three time slots. The invention remarkably improves the reliability of link transmission of the user terminals in a cellular mobile communication system by sufficiently utilizing the space diversity gain provided by the cooperation of users and also obtains higher utilization ratio of the channel.

Description

Virtual MIMO relay transmission method and system based on cluster user cooperation

Technical field

The present invention relates to a kind of relay transmission system.Particularly relate to a kind of virtual MIMO relay transmission method and system based on cluster user cooperation.

Background technology

For satisfying the demand of user to wide-band mobile communication, 3GPP started the LTE research project in 2004.The LTE system up-link adopts single-carrier frequency division multiple access (SC-FDMA) access scheme, and down link adopts the OFDMA transmission plan.Through the work in 4 years, 3GPP finished LTE Rel 8 system standardizations in December, 2008.

Plan determined target for further satisfying the ITU of International Telecommunications Union proposition IMT-advanced, 3GPP started the LTE-advanced project in 2008, this planned target is on the fundamental norms basis that LTE Rel 8 determines, the LTE fundamental system is strengthened, and reach following target: system transmission bandwidth expands to 100MHz from 20MHz, and the down link hardware circuit solution reaches 1Gbps (band efficiency 10bps/Hz); The up link hardware circuit solution is 500Mbps (band efficiency 5bps/Hz); Further increase the throughput of Cell Edge User.

The LTE-Advanced system down link need solve key problem: the throughput that improves the interference-limited user of sub-district middle part/cell edge, intend adopting the major technique means:, adopt single sub-district MU-MIMO technology to improve the downlink tone spectrum efficiency to the non-interference-limited user of center of housing estate; For the interference-limited user of cell edge, adopt multi-cell cooperating formula multicast communication (CoMP) to improve the throughput of Cell Edge User.Ul transmissions need solve key problem: overcome that limited and shadow fading produces network blind area of coverage owing to user's terminal transmitting power, improve Cell Edge User transmission reliability and spectrum efficiency.Intend adopting the major technique means: relay transmission.Correlative study shows: in cell mobile communication systems, can increase network coverage, improve the link transmission reliability by relay transmission.But since relay station need use when extra/the frequency resource just can be finished relay transmission, and (in the time-division relay communications system, relay station need use the extra slots resource; In the frequency division relay communications system, relay station need use the extra frequency resource), thus cause the system channel utilance to descend.Therefore in the LTE-Advanced ul transmissions, how to improve the link reliability of Cell Edge User and network blind area of coverage, the higher channel utilization of the system that guarantees simultaneously is a problem demanding prompt solution.

Existing solution is as follows:

1, based on DFT-S-OFDM single antenna relay transmission scheme

Shown in Figure 1, provided schematic diagram based on DFT-S-OFDM relay transmission system, system is made up of three kinds of different type network equipment: base station (eNodeB), relay station (Relay) and subscriber equipment (UE).System down link adopts the OFDMA mode to work, and up link adopts the DFT-S-OFDM mode to work.In ul transmissions, be positioned at the base station range user terminal and directly directly communicate with DFT-S-OFDM mode and base station; Being positioned at network black spots or Cell Edge User terminal then keeps communicating by letter by relay station and base station.

User terminal is as follows with the base station communication process by relay station: before suppose relay is communicated by letter and begun, user terminal by relay station to base station application running time-frequency resource that trunking traffic is used (the user terminal employed running time-frequency resource (abbreviating user's running time-frequency resource as) of communicating by letter with relay station, relay station is transmitted the employed running time-frequency resource of user terminal information (abbreviating the relaying running time-frequency resource as) to the base station), user's running time-frequency resource that the user terminal using system distributes is launched user profile in the DFT-S-OFDM mode and is given relay station, relay station adopts to detect and transmits, receiving user terminal in user's running time-frequency resource of system's appointment transmits, and through FFT, frequency domain equalization, IDFT, after demodulation and the channel decoding, obtain the bit information that the user sends, again carry out chnnel coding then, modulation, DFT, mapping, IFFT and insertion Cyclic Prefix obtain the relaying forward signal, and using system distributes the relaying running time-frequency resource to be transmitted to base station receiver, the base station receives the signal that relay station is transmitted in the relaying running time-frequency resource of system assignment, and recovers user terminal emission information.

Compare with non-trunking scheme ul transmissions scheme, have the following advantages based on DFT-S-OFDM single antenna relay transmission scheme: can improve network coverage, overcome the network service blind area.But there is following shortcoming simultaneously:, make power system capacity and spectrum efficiency significantly reduce because user terminal～relay station link additionally takies running time-frequency resource; The spatial reuse and the diversity gain that can't utilize multiaerial system to provide make the transmission capacity of user-terminal up-link and transmission reliability can not get abundant assurance; Need in existing mobile communication system, additionally arrange and significantly increase construction cost by relay station equipment.

2. based on the virtual MIMO relay transmission scheme of D-STBC coding

For overcoming the low and low shortcoming of link throughput, a kind of virtual MIMO relay transmission scheme based on distributed space time group coding (D-STBC) has been proposed based on single antenna DFT-S-OFDM relay system repeated link reliability.In this scheme, user terminal and relay station are formed virtual MIMO system, adopt based on the DFT-S-OFDM transmission plan and the base station of D-STBC coding and carry out message transmission, improve the reliability of link.

Fig. 2 has provided the virtual MIMO relay transmission scheme based on the D-STBC coding.Its course of work is as follows: before suppose relay communication begins, user terminal is to base station application running time-frequency resource that trunking traffic is used, user terminal carries out space-time block code (STBC) to its user profile, and user's running time-frequency resource that using system distributes is launched first row of STBC sign indicating number matrix in the DFT-S-OFDM mode, relay station and base station receive the signal from user terminal simultaneously in user's running time-frequency resource of system assignment, relay station adopts to detect and transmits, receiving user terminal in user's running time-frequency resource of system's appointment transmits, and through FFT, frequency domain equalization, IDFT, after demodulation and the channel decoding, obtain the bit information that the user sends, again carry out chnnel coding then, modulation, DFT, the STBC coding, mapping, IFFT and insertion Cyclic Prefix obtain the relaying forward signal, and using system distributes the relaying running time-frequency resource that the secondary series of STBC sign indicating number matrix is transmitted to base station receiver, the base station receives the signal that relay station is transmitted in the relaying running time-frequency resource of system assignment, and carry out space-time joint according to two time slot received signals and detect, recover user terminal emission information.

With comparing that Fig. 1 provides based on DFT-S-OFDM single antenna relay system, virtual MIMO relay transmission system based on the D-STBC coding has following advantage: make full use of the space diversity gain that virtual MIMO system provides, improve the reliability of user terminal and base station uplink transmission; But still there is following shortcoming:, make power system capacity and spectrum efficiency significantly reduce because relay station needs the outer running time-frequency resource of occupying volume; The spatial reuse and the diversity gain that can't utilize multiaerial system to provide make the transmission capacity of user-terminal up-link and transmission reliability can not get abundant assurance; Need in existing mobile communication system, additionally arrange and significantly increase construction cost by relay station equipment.

Summary of the invention

Technical problem to be solved by this invention is, can make full use of the gain of space diversity gain that collaboration user provides and spatial reuse and improve the link transmission reliability and obtain the higher channel utilization of more traditional relay transmission system simultaneously thereby provide a kind of, and adopt space-time block coding to keep the virtual MIMO relay transmission method and system based on cluster user cooperation of the low peak average ratio characteristic that transmits.

The technical solution adopted in the present invention is: a kind of virtual MIMO relay transmission method based on cluster user cooperation, adopt the virtual MIMO transmission technology between user terminal and base station, according to the distribution situation of user terminal in the sub-district, space plurality of adjacent user terminal is divided into one bunch, and the sub-district is formed by a plurality of bunches; Will bunch between user terminal Channel Modeling be Rice channel; With Channel Modeling between user terminal and base station is the multipath Rayleigh fading channel; Making cooperates mutually with two user terminals in the cluster finishes the message transmission of user terminal to base station in three time slots.

When two user terminals are cooperated mutually in cluster, the cooperation terminal of another user terminal each other.

Described make with cluster in two user terminals cooperate mutually and in three time slots, finish in the message transmitting procedure of user terminal to base station, suppose that user terminal keeps invariable with the channel transfer characteristic of the terminal of cooperating, user terminal and base station in three time slots of collaboration communication; Simultaneously in the hypothesis bunch user terminal when setting up collaboration communication and concern, can obtain the channel fading information of communications user terminal with it, the base station can obtain the channel information of user terminal to base station uplink by channel estimating, consider that the user terminal volume is limited, suppose that user terminal all installs individual antenna, a plurality of reception antennas are installed in the base station, and system is with time division duplex work.

The cooperation terminal is finished estimation and the detection to user terminal emission modulation symbol, and carries out space-time block coding to estimating with testing result, and cooperation terminal and base station link time slot subsequently are transmitted to base station receiver with it.

In up link, under base station scheduling, use identical running time-frequency resource and base station receiver to realize communicating by letter with each user terminal in the cluster.

In the up link base station receiver,, finish the separation of subscriber signal by adopting two users' space-time joint equalization algorithm according to three time slot received signals.

Described three time slots are: first time slot, and user terminal emission information, cooperation terminal and base station receive the signal of user terminal emission; Second time slot, user terminal emission information, cooperation terminal and base station receive the signal of user terminal emission; The 3rd time slot, user terminal and user terminal carry out the information of first time slot and the reception of second time slot to be forwarded to the base station behind the space-time block coding, and the information that obtains user terminal and user terminal emission is detected according to three signals that time slot received in the base station by space-time joint.

A kind of relay communications system of the virtual MIMO relay transmission method based on cluster user cooperation, the base station that includes a plurality of user terminals and communicate with a plurality of user terminals, described plurality of adjacent user terminal form bunch, the message transmission of user terminal to base station is finished in cooperation in three time slots mutually.

The user terminal transmitter includes successively coding, modulation, L point DFT, mapping, N (N＞L) some IFFT, insertion CP, Tx and the transmitting antenna of serial connection in described first time slot and second time slot; The user terminal receiver includes successively serial connection: reception antenna, Rx, remove CP, N point FFT, separate mapping, equilibrium, L point IDFT, detect, separate mediation and decipher; The 3rd time slot user terminal transmitter includes successively serial connection: coding, modulation, L point DFT, B-STBC coding, mapping, N point IFFT, insertion CP, Tx and transmitting antenna.

Described base station receiver includes reception antenna, Rx, removes CP, N point FFT, separate mapping, space-time joint equilibrium, L point IDFT, detect, separate and be in harmonious proportion decoding.

Virtual MIMO relay transmission method and system based on cluster user cooperation of the present invention, adopt and detect the forward relay mode of operation, cooperate mutually with two users in the cluster and in three time slots, to finish the message transmission of user terminal to base station, the present invention makes full use of the space diversity gain that user collaboration provides, and significantly improves user terminal link transmission reliability in the cell mobile communication systems; Make full use of the spatial reuse gain that virtual MIMO technology provides simultaneously, obtain the higher channel utilization of more traditional relay transmission system; In addition, the space-time block coding transmission plan that is adopted has also kept the good characteristic of LTE system up-link low peak average ratio.Virtual MIMO relay transmission method and system based on cluster user cooperation of the present invention can be applicable to LTE-Advanced and 4G wide-band mobile communication system.

Description of drawings

Fig. 1 is based on the formation schematic diagram of DFT-S-OFDM single antenna relay transmission system;

Fig. 2 is based on the formation schematic diagram of the virtual MIMO relay transmission system of D-STBC coding;

Fig. 3 is that the relay transmission based on cluster user cooperation of the present invention constitutes schematic diagram;

Fig. 4 is the relay transmission process of cluster user cooperation of the present invention;

Fig. 5 is the user terminal transmitter block diagram;

Fig. 6 is a user terminal receiver block diagram;

Fig. 7 is a TS3 time slot user terminal transmitter block diagram;

Fig. 8 is the base station receiver block diagram;

Fig. 9 is cluster two users, the single reception antenna block diagram in base station;

Figure 10 is cluster two users, base station two reception antenna block diagrams;

Figure 11 is two bunches of four-function families, base station two reception antenna block diagrams;

Figure 12 be bunch in the bit error performance curve of user collaboration link;

Figure 13 is based on cluster user cooperation relay system bit error performance curve.

Wherein,

DFT: discrete Fourier transform IFFT: inverse fast Fourier transform

CP: Cyclic Prefix Tx: intermediate frequency and rf transmitter unit

Rx: intermediate frequency and rf receiver unit FFT: fast Fourier transform

IDFT: inverse discrete Fourier transform B-STBC: space-time block coding

Embodiment

Below in conjunction with embodiment and accompanying drawing the virtual MIMO relay transmission method and system based on cluster user cooperation of the present invention are made a detailed description.

Virtual MIMO relay transmission method based on cluster user cooperation of the present invention, adopt the virtual MIMO transmission technology between its user terminal and base station, according to the distribution situation of user terminal in the sub-district, space plurality of adjacent user terminal is divided into one bunch (cluster), and the sub-district is formed by a plurality of bunches; With in the cluster between user terminal distance nearer, channel transfer characteristic is good, will bunch between user terminal Channel Modeling be Rice channel; And bunch in user terminal and base station distance far away, be the multipath Rayleigh fading channel with Channel Modeling between user terminal and base station; Making cooperates mutually with two user terminals in the cluster finishes the message transmission of user terminal to base station in three time slots.

Fig. 4 is the relay transmission process of cluster user cooperation of the present invention.Wherein,

The frequency domain symbol vector that representative of consumer terminal u is transmitted at the s time slot.

As shown in Figure 4, described three time slots are: the first time slot TS1, and user terminal MS1 launches information, and cooperation terminal MS 2 receives the signal that user terminal MS1 launches with the base station; The second time slot TS2, user terminal MS2 launches information, and cooperation terminal MS 1 receives the signal that user terminal MS2 launches with the base station; The 3rd time slot TS3, user terminal MS1 and user terminal MS2 carry out the information of the first time slot TS1 and second time slot TS2 reception to be forwarded to base station BS behind the space-time block coding, and base station BS detects the information that obtains user terminal MS1 and user terminal MS2 emission according to three signals that time slot received by space-time joint.Can significantly improve the user-terminal up-link transmission reliability like this, remedy the shortcoming that link spectral efficiency significantly descends in the traditional relay transmission system simultaneously.

When two user terminals are cooperated mutually in cluster, be called the cooperation terminal of another user terminal mutually.

Described make with cluster in two user terminals cooperate mutually and in three time slots, finish in the message transmitting procedure of user terminal to base station, suppose that user terminal keeps invariable with the channel transfer characteristic of the terminal of cooperating, user terminal and base station in three time slots of collaboration communication; Simultaneously in the hypothesis bunch user terminal when setting up collaboration communication and concern, can obtain the channel fading information of communications user terminal with it, the base station can obtain the channel information of user terminal to base station uplink by channel estimating, consider that the user terminal volume is limited, suppose that user terminal all installs individual antenna, a plurality of reception antennas are installed in the base station, and system is with time division duplex work (being that user terminal can not be launched and receive simultaneously).

The cooperation terminal is finished estimation and the detection to user terminal emission modulation symbol, and carries out space-time block coding to estimating with testing result, and cooperation terminal and base station link time slot subsequently are transmitted to base station receiver with it.The low peak average ratio characteristic that transmits that the cooperation terminal has adopted the space-time block coding technique guarantee.Also guaranteed the low complex degree that base station receiver detects in addition.

In up link, under base station scheduling, use identical running time-frequency resource and base station receiver to realize communicating by letter with each user terminal in the cluster.

In the up link base station receiver,, finish the separation of subscriber signal by adopting two users' space-time joint equalization algorithm according to three time slot received signals.

As shown in Figure 3, employing of the present invention is based on the relay communications system of the virtual MIMO relay transmission method of cluster user cooperation, the base station (eNodeB) that includes a plurality of user terminal UE and communicate with a plurality of user terminal UE, bunch A that described plurality of adjacent user terminal UE forms, the message transmission of user terminal to base station is finished in cooperation in three time slots mutually.

As Fig. 4, shown in Figure 5, the user terminal transmitter includes coding 1, modulation 2, L point DFT3, mapping 4, N point IFFT5, insertion CP6, Tx7 and the transmitting antenna 8 of serial connection successively among the described first time slot TS1 and the second time slot TS2.

At the first time slot TS1, user terminal MS1 transmits, and cooperation terminal MS 2 received signals also detect, and the base station only receives user terminal MS1 terminal and transmits.Fig. 5 shows the composition frame chart that provides based on user terminal transmitter in the cluster user cooperation uplink relay transmission plan.The user terminal MS1 process that transmits is as follows: the information bit of user terminal MS1 is at first sent into encoder and is carried out chnnel coding, encoder output bit sequence is sent into modulator and is finished symbol-modulated, and modulator output complex symbol is unit divide into groups (L represent the number of subchannels of base station assigns to user terminal) with the length L.User terminal MS1 is expressed as in first time slot TS1 symbol packets waiting for transmission

Through being expressed as after the L point DFT preliminary treatment:

$A_1^{\left(1\right)}={\mathrm{Da}}_1^{\left(1\right)},---\left(1\right)$

Wherein, D represents L point DFT transformation matrix,

M, n ∈ 0,1 ..., L-1}.Suppose that the SC-FDMA system adopts continuous subchannel mapping mode, i.e. signal phasor after the user terminal MS1 preliminary treatment

Be mapped to L the continuous subchannel that v+1 begins, then mapping back signal phasor can be expressed as:

$B_1^{\left(1\right)}={\mathrm{MA}}_1^{\left(1\right)},---\left(2\right)$

Wherein,

Represent the channel Mapping matrix, N representative system subchannel sum.Mapping back signal phasor is converted to the time-domain signal vector through N point IDFT computing

$b_1^{\left(1\right)}=F^H{B}_1^{\left(1\right)},---\left(3\right)$

Wherein,

F represents N point IDFT transformation matrix.The time-domain signal vector

Inserting N _gBe expressed as after the dot cycle prefix:

$b_{c1}^{\left(1\right)}=P_{\mathrm{in}}{b}_1^{\left(1\right)},---\left(4\right)$

Wherein,

P _InFor Cyclic Prefix inserts matrix, its concrete form is as follows:

$P_{\mathrm{in}}{=\left[\begin{array}{cc}{0}_{N_g\×(N-N_g)}& I_{N_g}\\ I_N& \end{array}\right]}_{(N+N_g)\×N}.---\left(5\right)$

Be converted to analog baseband signal by D/A, and be converted to radiofrequency signal, send into the antenna emission at last by transmitter unit.

As shown in Figure 6, the user terminal receiver includes successively serial connection: reception antenna 9, Rx10, remove CP11, N point FFT12, separate mapping 13, balanced 14, L point IDFT15, detection 16, demodulation 17 and decipher 18.

The first time slot TS1, cooperation terminal MS 2 receives user terminal MS1 and transmits.The signal that receives Can be expressed as:

$r_{c2}^{\left(1\right)}\left(k\right)=\underset{\mathrm{\&lambda;}=0}{\overset{p-1}{\mathrm{\&Sigma;}}}{\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="HDA0000022605630000041.png,HDA0000022605630000062.png"\; state="\{\{state\}\}">h</figure-callout>}}_{\mathrm{2,1}}\left(\mathrm{\&lambda;}\right)\&CenterDot;b_{c1}^{\left(1\right)}(k-\mathrm{\&lambda;})+n_2^{\left(1\right)}\left(k\right),---\left(6\right)$

Wherein, h _2,1(k) (k=0,1 ..., p-1) representative of consumer terminal MS 1 arrives the channel impulse response of cooperation terminal MS 2,

Representative of consumer terminal MS 2 receives the white complex gaussian noise signal in the TS1 time slot, its average is zero, and variance is

Formula (6) further is expressed as matrix form:

$r_{c2}^{\left(1\right)}={\mathrm{<figure-callout\; id="2"\; label="H"\; filenames="HDA0000022605630000041.png,HDA0000022605630000062.png"\; state="\{\{state\}\}">H</figure-callout>}}_{\mathrm{2,1}}{b}_{c1}^{\left(1\right)}+n_2^{\left(1\right)},---\left(7\right)$

Wherein, H _2,1Be (N+N _g) * (N+N _g) user terminal MS1 to the cooperation terminal MS 2 the Channel Transmission matrix.Receiver is expressed as after removing Cyclic Prefix:

$r_2^{\left(1\right)}=P_{\mathrm{out}}{r}_{c2}^{\left(1\right)},---\left(8\right)$

Wherein,

Represent Cyclic Prefix to remove matrix.Further will by N point DFT computing

Being expressed as frequency domain form obtains:

$R_2^{\left(1\right)}={\mathrm{Fr}}_2^{\left(1\right)},---\left(9\right)$

Wherein,

Utilize again and separate mapping matrix M ^HFrom

In extract transmission signals in the user terminal L subchannel

$Y_2^{\left(1\right)}=M^H{R}_2^{\left(1\right)},---\left(10\right)$

Wherein,

Formula (10) can further be expressed as:

$Y_2^{\left(1\right)}=M^{H}F{P}_{\mathrm{out}}{\mathrm{<figure-callout\; id="2"\; label="H"\; filenames="HDA0000022605630000041.png,HDA0000022605630000062.png"\; state="\{\{state\}\}">H</figure-callout>}}_{\mathrm{2,1}}{P}_{\mathrm{in}}{F}^H{\mathrm{MA}}_1^{\left(1\right)}+M^{H}F{P}_{\mathrm{out}}{n}_2^{\left(1\right)},---\left(11\right)$

$={\mathrm{<figure-callout\; id="2"\; label="H\; eq"\; filenames="HDA0000022605630000041.png,HDA0000022605630000062.png"\; state="\{\{state\}\}">H</figure-callout>}}_{\mathrm{eq}}{A}_1^{\left(1\right)}+N_2^{\left(1\right)}$

Wherein, H _{Eq 2,1}Be L * L diagonal matrix, its k (k=0,1 ..., L-1) individual diagonal element H _Eq2,1(k k) is the frequency domain response of user terminal MS1 to v+k+1 subchannel of cooperation terminal MS 2,

Be the white complex gaussian noise vector, its each component average is zero, and variance still is Introduce linear ZF diagonal matrix

Its k diagonal element is:

$E_2^{\left(1\right)}(k,k)=\frac{{\mathrm{<figure-callout\; id="2"\; label="H\; eq"\; filenames="HDA0000022605630000041.png,HDA0000022605630000062.png"\; state="\{\{state\}\}">\; <figure-callout\; id="1"\; label="H\; eq"\; filenames="HDA0000022605630000022.png,HDA0000022605630000031.png"\; state="\{\{state\}\}">H</figure-callout>\; </figure-callout>}}_{\mathrm{eq}}^{\mathrm{2,1}}(k,k)}{{|\mathrm{<figure-callout\; id="2"\; label="H\; eq"\; filenames="HDA0000022605630000041.png,HDA0000022605630000062.png"\; state="\{\{state\}\}">H</figure-callout>}}_{\mathrm{eq}}{(k,k)|}^2},k=\mathrm{0,1},...,L-1.---\left(12\right)$

Receiver utilizes

Vector to received signal

Carrying out linear equalization obtains:

$A_2^{\%\left(1\right)}=E_2^{\left(1\right)}{Y}_2^{\left(1\right)}$

$=A_1^{\left(1\right)}+{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HDA0000022605630000041.png,HDA0000022605630000062.png"\; state="\{\{state\}\}">N</figure-callout>}}_2^{\%\left(1\right)},---\left(13\right)$

Wherein, Representative improves noise vector.Further be transformed into time domain again by the signal phasor of L point IDFT computing after with equilibrium

$a_2^{\%\left(1\right)}=D^H{A}_2^{\%\left(1\right)},---\left(14\right)$

Wherein, Right at last Pursue symbol detection and obtain user terminal MS1 in TS1 time slot emission dope vector

Estimation Again it is carried out channel decoding and obtain user terminal output bit sequence.

As shown in Figure 8, described base station receiver include base station reception antenna 28, Rx29, remove CP30, N point FFT31, separate mapping 32, space-time joint equilibrium 33, L point IDFT34, detection 35, demodulation 36 and decipher 37.

In the first time slot TS1, the base station receives the signal of user terminal MS1 emission simultaneously, for sake of convenience, supposes base station use single receive antenna here, and this programme can conveniently be generalized to the situation that a plurality of reception antennas are used in the base station.Fig. 8 provides the base station receiver block diagram.Base station receiver is after removing Cyclic Prefix, carry out the FFT conversion that N orders and separating mapping, and received signal is expressed as:

$Y_b^{\left(1\right)}=H_{\mathrm{eqb},1}{A}_1^{\left(1\right)}+N_b^{\left(1\right)},---\left(15\right)$

Wherein, H _{Eq b, 1}Representative of consumer terminal MS 1 arrives base station equivalent channel frequency domain response matrix,

Be TS1 time slot base station receiver white complex gaussian noise vector, each component average is zero, and variance is

Similarly, at the second time slot TS2, user terminal MS2 sends symbol packets and is designated as

Its L point DFT is transformed to

Cooperation terminal MS 1 adopts with TS1 time slot user terminal MS2 identical process reception user terminal MS2 and transmits, and detection obtains

Estimation

Simultaneously, signal phasor was expressed as after base station receiver was separated mapping

$Y_b^{\left(2\right)}=H_{\mathrm{eqb},2}{A}_2^{\left(2\right)}+N_b^{\left(2\right)},---\left(16\right)$

Wherein, H _{Eq b, 2}Representative of consumer terminal MS 2 arrives base station equivalent channel frequency domain response matrix,

Be TS2 time slot base station receiver white complex gaussian noise vector, each component average is zero, and variance is

To be expressed as after formula (15) and (16) merging

$Y_b^{\left(\mathrm{1,2}\right)}=Y_b^{\left(1\right)}+Y_b^{\left(2\right)}---\left(17\right)$

$H_{\mathrm{eqb},1}{A}_1^{\left(1\right)}+H_{\mathrm{eqb},2}{A}_2^{\left(2\right)}+N_b^{\left(\mathrm{1,2}\right)},$

Wherein,

Its each component average is zero, and variance is

As shown in Figure 7, the 3rd time slot TS3 user terminal transmitter includes successively serial connection: coding 19, modulation 20, L point DFT21, B-STBC coding 22, mapping 23, N point IFFT24, insertion CP25, Tx26 and transmitting antenna 27.

Fig. 7 has provided the transmitter block diagram of user terminal at the 3rd time slot TS3 (cooperation transmission time slot).In considering bunch between collaboration user channel transfer characteristic good, suppose that here user terminal can correctly detect its collaboration user information transmitted, promptly in the first time slot TS1 and the second time slot TS2 time slot

In the 3rd time slot TS3 time slot, the collaboration user terminal is carried out channel decoding and modulation again to detected bit sequence, the modulation symbolic vector is done L point DFT conversion, and the frequency domain symbol vector is carried out space-time block coding, promptly

(noticing that space-time block coding can not influence the peak-to-average force ratio that the SC-FDMA system transmits) carries out processing backs such as subchannel mapping, N point IDFT, insertion Cyclic Prefix subsequently and launches from antenna.The base station receives the signal from user terminal 1,2 simultaneously, is removing Cyclic Prefix, the DFT conversion of N point and is separating processing such as mapping, and then base station receiver is separated mapping back signal phasor and can be expressed as:

$Y_b^{\left(3\right)}=H_{\mathrm{eqb},1}{A}_1^{\left(3\right)}+H_{\mathrm{eqb},2}{A}_2^{\left(3\right)}+N_b^{\left(3\right)}---\left(18\right)$

$=-H_{\mathrm{eqb},1}{A}_2^{\left(2\right)*}+H_{\mathrm{eqb},2}{A}_1^{\left(1\right)*}+N_b^{\left(3\right)},$

Wherein,

Represent the 3rd time slot TS3 base station to receive the white complex gaussian noise signal phasor, formula (18) is carried out conjugate operation and is obtained:

$Y_b^{\left(3\right)*}=-H_{\mathrm{eqb},1}^{*}{A}_2^{\left(2\right)}+H_{\mathrm{eqb},2}^{*}{A}_1^{\left(1\right)}+N_b^{\left(3\right)*},---\left(19\right)$

Matrix form is merged in formula (17) and (19) to be obtained:

$\left[\begin{array}{c}{Y}_b^{\left(\mathrm{1,2}\right)}\\ Y_b^{\left(3\right)*}\end{array}\right]=\left[\begin{array}{cc}{H}_{\mathrm{eqb},1}& H_{\mathrm{eqb},2}\\ H_{\mathrm{eqb},2}^{*}& {-H}_{\mathrm{eqb},1}^{*}\end{array}\right]\left[\begin{array}{c}{A}_1^{\left(1\right)}\\ A_2^{\left(2\right)}\end{array}\right]+\left[\begin{array}{c}{N}_b^{\left(\mathrm{1,2}\right)}\\ N_b^{\left(3\right)*}\end{array}\right].---\left(20\right)$

Base station receiver can provide signal model according to (20) formula, directly uses linear ZF or least mean-square error detection algorithm to obtain

Estimated value.But count L when big when user's allocated sub-channels, the computational complexity that directly uses matrix inversion technique to detect is higher.Below provide a kind of low complex degree receiver detection algorithm, (20) formula further be expressed as:

Y＝HA+N， (21)

Wherein,

Utilize the class Alamouti characteristic structure signal of H matrix

$Y^{\%}=H^{H}Y$

$=H^H\mathrm{HA}+H^{H}N,---\left(22\right)$

$=H^H\mathrm{HA}+N^{\%}$

According to H ^HThe H operation result obtains:

$Y^{\%}=\left[\begin{array}{c}{\mathrm{<figure-callout\; id="1"\; label="Y"\; filenames="HDA0000022605630000022.png,HDA0000022605630000031.png"\; state="\{\{state\}\}">Y</figure-callout>}}_1^{<figure-callout\; id="2"\; label="\%\; Y"\; filenames="HDA0000022605630000041.png,HDA0000022605630000062.png"\; state="\{\{state\}\}">\%</figure-callout>}& \\ Y_{}^{}{}_2^{\%}\end{array}\right]=\left[\begin{array}{cc}{H}_{\mathrm{eqb},1}^{*}{H}_{\mathrm{eqb},1}+H_{\mathrm{eqb},2}^{*}{H}_{\mathrm{eqb},2}& 0\\ 0& {H_{\mathrm{eqb},1}^{*}H}_{\mathrm{eqb},1}+H_{\mathrm{eqb},2}^{*}{H}_{\mathrm{eqb},2}\end{array}\right]\left[\begin{array}{c}{A}_1^{\left(1\right)}\\ A_2^{\left(1\right)}\end{array}\right]+\left[\begin{array}{c}{\mathrm{<figure-callout\; id="1"\; label="N"\; filenames="HDA0000022605630000022.png,HDA0000022605630000031.png"\; state="\{\{state\}\}">N</figure-callout>}}_1^{<figure-callout\; id="2"\; label="\%\; N"\; filenames="HDA0000022605630000041.png,HDA0000022605630000062.png"\; state="\{\{state\}\}">\%</figure-callout>}& \\ N_{}^{}{}_2^{\%}\end{array}\right],---\left(23\right)$

Wherein,

Following formula further abbreviation is:

${\mathrm{<figure-callout\; id="1"\; label="Y"\; filenames="HDA0000022605630000022.png,HDA0000022605630000031.png"\; state="\{\{state\}\}">Y</figure-callout>}}_1^{\%}=(H_{\mathrm{eqb},1}^{*}{H}_{\mathrm{eqb},1}+H_{\mathrm{eqb},2}^{*}{H}_{\mathrm{eqb},2})A_1^{\left(1\right)}+{\mathrm{<figure-callout\; id="1"\; label="N"\; filenames="HDA0000022605630000022.png,HDA0000022605630000031.png"\; state="\{\{state\}\}">N</figure-callout>}}_1^{\%}$

${\mathrm{<figure-callout\; id="2"\; label="Y"\; filenames="HDA0000022605630000041.png,HDA0000022605630000062.png"\; state="\{\{state\}\}">Y</figure-callout>}}_2^{\%}=(H_{\mathrm{eqb},1}^{*}{H}_{\mathrm{eqb},1}+H_{\mathrm{eqb},2}^{*}{H}_{\mathrm{eqb},2})A_2^{\left(2\right)}+{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HDA0000022605630000041.png,HDA0000022605630000062.png"\; state="\{\{state\}\}">N</figure-callout>}}_2^{\%},---\left(24\right)$

Consider

Be diagonal matrix, can conveniently obtain

Estimated value:

$A_1^{\%\left(1\right)}={(H_{\mathrm{eqb},1}^{*}{H}_{\mathrm{eqb},1}+H_{\mathrm{eqb},2}^{*}{H}_{\mathrm{eqb},2})}^{-1}{\mathrm{<figure-callout\; id="1"\; label="Y"\; filenames="HDA0000022605630000022.png,HDA0000022605630000031.png"\; state="\{\{state\}\}">Y</figure-callout>}}_1^{\%}=A_1^{\left(1\right)}+{(H_{\mathrm{eqb},1}^{*}{H}_{\mathrm{eqb},1}+H_{\mathrm{eqb},2}^{*}{H}_{\mathrm{eqb},2})}^{-1}{\mathrm{<figure-callout\; id="1"\; label="N"\; filenames="HDA0000022605630000022.png,HDA0000022605630000031.png"\; state="\{\{state\}\}">N</figure-callout>}}_1^{\%}$

$A_2^{\%\left(2\right)}={(H_{\mathrm{eqb},1}^{*}{H}_{\mathrm{eqb},1}+H_{\mathrm{eqb},2}^{*}{H}_{\mathrm{eqb},2})}^{-1}{\mathrm{<figure-callout\; id="2"\; label="Y"\; filenames="HDA0000022605630000041.png,HDA0000022605630000062.png"\; state="\{\{state\}\}">Y</figure-callout>}}_2^{\%}=A_2^{\left(2\right)}+{(H_{\mathrm{eqb},1}^{*}{H}_{\mathrm{eqb},1}+H_{\mathrm{eqb},2}^{*}{H}_{\mathrm{eqb},2})}^{-1}{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HDA0000022605630000041.png,HDA0000022605630000062.png"\; state="\{\{state\}\}">N</figure-callout>}}_2^{\%},---\left(25\right)$

Right more subsequently

Be the IDFT that L is ordered,

Again each component is carried out Maximum Likelihood Detection at last, obtain the transmission symbol vector

Estimated value.Again it is done and separate the mediation channel decoding, finally obtain user terminal output bit sequence.

Fig. 9 of the present invention, 10,11 has provided the virtual MIMO relay transmission method part embodiment based on cluster user cooperation.It is 2/4/6/8 that the scheme that the present invention proposes also can conveniently be generalized to bunch number of users, and the base station receiver antenna number is a situation such as 1/2/4/6/8.While is many more with bunch user that the signal transmission is carried out in the base station, and then the obtainable spectrum efficiency of system is high more, and the complexity of base station detection algorithm is also high more.The base station receiver antenna number is many more, and then the obtainable diversity gain of system is big more, and the bit error performance is good more.

Table 1 provides direct transmission, based on DFT-S-OFDM single antenna relay transmission, based on the virtual MIMO relay transmission of D-STBC coding and spectrum efficiency based on cluster user cooperation relay transmission scheme (bunch number of users is 2).In the table, on behalf of modulation constellation, Q comprise number of constellation points, and Δ f represents SC-FDMA system subchannel at interval, T conventional letter cycle, L representative of consumer terminal distribution number of subchannels.Table 1 comparative result shows: with respect to other existing relay transmission scheme, have higher spectrum efficiency based on cluster user cooperation relay transmission scheme.

The analysis of table 1 junction efficiency

It is 2 that the present invention provides bunch number of users, and the base station reception antenna is 1 or 2 o'clock, based on the virtual MIMO relay transmission systematic bits error performance of cluster user cooperation.

The bit error performance of user collaboration link and the relation of this factor K of channel Lay in Figure 12 provides bunch, simulation result shows: along with the increase of this factor K of channel Lay, user collaboration link transmission reliability significantly improves in bunch.Pertinent literature studies show that: the typical span of the user collaboration link K factor is 5-11 in bunch, and good and exist more tetanicly when penetrating signal component when the characteristic of channel, the K factor can get 17.6.

Figure 13 provides based on the bit error performance of cluster user cooperation relay transmission scheme (this factor K of cooperation channel Lay is 10 or 15 in bunch, and signal to noise ratio is 12/15/18dB, and base station reception antenna number is 1 and 2).Simulated conditions: this factor value of the Lay of collaboration user channel is 10 or 15 in bunch, and the signal to noise ratio value is 12/15/18dB, and base station reception antenna number is 1 or 2.Simulation result comparison shows that: when single receive antenna is used in the base station, can obtain double diversity gain based on bunch association's relay transmission scheme; When two reception antennas are used in the base station, can obtain the quadruple diversity gain based on bunch association's relay transmission scheme, promptly bunch cooperating relay transmission can significantly be improved the link transmission reliability; In addition, when bunch in the less or cooperation channel signal to noise ratio of this factor value of Lay of cooperation channel when low because the restriction of cooperation channel error performance in being subjected to bunch, wrong platform appears in simulation curve, and along with bunch in the increase of cooperation channel this factor of Lay and signal to noise ratio, the mistake platform significantly descends.

Claims (10)

1. virtual MIMO relay transmission method based on cluster user cooperation, it is characterized in that: adopt the virtual MIMO transmission technology between user terminal and base station, according to the distribution situation of user terminal in the sub-district, space plurality of adjacent user terminal is divided into one bunch, and the sub-district is formed by a plurality of bunches; Will bunch between user terminal Channel Modeling be Rice channel; With Channel Modeling between user terminal and base station is the multipath Rayleigh fading channel; Making cooperates mutually with two user terminals in the cluster finishes the message transmission of user terminal to base station in three time slots.

2. the virtual MIMO relay transmission method based on cluster user cooperation according to claim 1 is characterized in that: when two user terminals are cooperated mutually in cluster, and the cooperation terminal of another user terminal each other.

3. the virtual MIMO relay transmission method based on cluster user cooperation according to claim 1, it is characterized in that: described make with cluster in two user terminals cooperate mutually and in three time slots, finish in the message transmitting procedure of user terminal to base station, suppose that user terminal keeps invariable with the channel transfer characteristic of the terminal of cooperating, user terminal and base station in three time slots of collaboration communication; Simultaneously in the hypothesis bunch user terminal when setting up collaboration communication and concern, can obtain the channel fading information of communications user terminal with it, the base station can obtain the channel information of user terminal to base station uplink by channel estimating, consider that the user terminal volume is limited, suppose that user terminal all installs individual antenna, a plurality of reception antennas are installed in the base station, and system is with time division duplex work.

4. the virtual MIMO relay transmission method based on cluster user cooperation according to claim 1, it is characterized in that: the cooperation terminal is finished estimation and the detection to user terminal emission modulation symbol, and carrying out space-time block coding with testing result to estimating, cooperation terminal and base station link time slot subsequently are transmitted to base station receiver with it.

5. the virtual MIMO relay transmission method based on cluster user cooperation according to claim 1 is characterized in that: in up link, use identical running time-frequency resource and base station receiver to realize communicating by letter under base station scheduling with each user terminal in the cluster.

6. the virtual MIMO relay transmission method based on cluster user cooperation according to claim 1, it is characterized in that: in the up link base station receiver, according to three time slot received signals, finish the separation of subscriber signal by adopting two users' space-time joint equalization algorithm.

7. the virtual MIMO relay transmission method based on cluster user cooperation according to claim 1, it is characterized in that: described three time slots are: first time slot (TS1), user terminal (MS1) emission information, cooperation terminal (MS2) receives the signal that user terminal (MS1) is launched with the base station; Second time slot (TS2), user terminal (MS2) emission information, cooperation terminal (MS1) receives the signal that user terminal (MS2) is launched with the base station; The 3rd time slot (TS3), user terminal (MS1) and user terminal (MS2) carry out the information of first time slot (TS1) and second time slot (TS2) reception to be forwarded to base station (BS) behind the space-time block coding, and base station (BS) detects the information that obtains user terminal (MS1) and user terminal (MS2) emission according to three signals that time slot received by space-time joint.

8. relay communications system that adopts the described virtual MIMO relay transmission method based on cluster user cooperation of claim 1, the base station (eNodeB) that includes a plurality of user terminals (UE) and communicate with a plurality of user terminals (UE), it is characterized in that: bunch (A) that described plurality of adjacent user terminal (UE) is formed, the message transmission of user terminal to base station is finished in cooperation in three time slots mutually.

9. the relay communications system of the virtual MIMO relay transmission method based on cluster user cooperation according to claim 8 is characterized in that: the user terminal transmitter includes coding (1), modulation (2), L point DFT (3), mapping (4), N (N＞L) some IFFT (5), insertion CP (6), Tx (7) and the transmitting antenna (8) of serial connection successively in described first time slot (TS1) and second time slot (TS2); The user terminal receiver includes successively serial connection: reception antenna (9), Rx (10), remove CP (11), N point FFT (12), separate mapping (13), balanced (14), L point IDFT (15), detection (16), demodulation (17) and decipher (18); The 3rd time slot (TS3) user terminal transmitter includes successively serial connection: coding (19), modulation (20), L point DFT (21), B-STBC coding (22), mapping (23), N point IFFT (24), insertion CP (25), Tx (26) and transmitting antenna (27).

10. the relay communications system of the virtual MIMO relay transmission method based on cluster user cooperation according to claim 8 is characterized in that: described base station receiver includes reception antenna (28), Rx (29), removes CP (30), N point FFT (31), separate mapping (32), space-time joint equilibrium (33), L point IDFT (34), detect (35), demodulation (36) and decipher (37).

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