CN101083497B - Multiuser transmission diversity and relay method and system - Google Patents

Abstract

The invention relates to a multi-communication terminal transmit diversity and transmit diversity relay method in wireless communication system, comprising the steps: multiple communication terminals use their respective source transmission channels to transmit signals; signal gathering point receives these signals and makes linear conversion on these signals and uses multiple channels to transmit linear converted signals, where each channel in multiple channels transmits a linear combination of signals transmitted by multiple communication terminals; and at the receiving end, demodulating the signals transmitted by the signal gathering point.

Description

Multiuser transmission diversity and trunking method and system

Technical field

The present invention relates to the method and system of multiuser transmission diversity and relaying; More particularly; Relate in the wireless communication system of multi-user and multi-channel; Send the some combined coding with the method and system of realization transmission minute collection at signal gathering, thereby improve the validity and the reliability of wireless communication system with relaying.

Background technology

In mobile radio system, pass through wireless mobile channel from mobile radio station or base station through the signal of antenna emission, arrive the reception antenna of receiving terminal through complicated communication environments.Because the effect of communication environments, the signal that reception antenna receives is the compound of each reflection, diffraction and scattering component and interchannel noise, thereby can produce serious distortion.In addition, in mobile channel, because the motion of mobile radio station or the change of channel circumstance can make the characteristic of channel change in time, the signal that receives can produce even more serious distortion owing to Doppler effect.Like this, wireless mobile channel is actually a time varying frequency Selective Fading Channel.In this case, use wireless mobile channel to realize that the high-speed multimedia service access faces great challenge undoubtedly.In addition, except multipath transmisstion and time-varying characteristics, the path loss of wireless mobile channel is the growth of index ground with the growth of transmission range.

The signal fadeout that people use the method for wireless relay and branch collection to resist wireless channel usually.For radio honeycomb communication net, mobile Ad hoc network and radio sensing network, the radio repeater station that some is set in the sphere of action of network can significantly improve network throughput or transmission reliability.Research shows that the relaying that cooperates with each other between the user in the network also can reach the purpose that improves network throughput or transmission reliability.Aria Nosratinna; The article that is entitled as " Coopertive communication in wireless networks " that Todd E.Hunter and AhmadrezaHedayat deliver has been done this and has been explained that (particular content is referring to IEEE Communications magazine; Oct.2005, pp.74-80).

Figure 1A and 1B show respectively and between two users, pass through the sequential schematic that relaying is realized duplex communication.Shown in Figure 1A, two users that participate in two-way communication are respectively with numbering U ₀And U ₁Expression.At first, user U ₀The data symbol S that will send ₀Send through wireless channel, after relay station R accepts and detects this signal, uses a trunk channel that this symbol is forwarded to reception user U ₁Then, user U ₁Send data symbol S ₁, relay station detects and transmits this data symbol S ₁To user U ₀Like this, if adopt time division way, accomplishing a bi-directional data transmission needs 4 time slots altogether.For adopting frequency division and sign indicating number to divide the system of mode, then need 4 frequency bands and 4 code channels respectively.

Fig. 2 shows the block diagram of traditional wireless relay.User U wherein ₀With user U ₁Send corresponding data symbol S through source transmitting channel 1 and 2 respectively ₀And S ₁ Single user detector 3,4 in the relay station receives user U respectively ₀With user U ₁The data symbol S that sends ₀And S ₁, and transmit data symbol S respectively through trunk channel 5 and 6 ₀And S ₁To receiving terminal.In the mobile radio system of reality, can adopt the combination of time-division, frequency division, sign indicating number branch mode and these modes.For simplicity, no longer distinguish time slot, frequency band and code channel below and be referred to as channel.Peter Larsson (compare. draw Ademilson) etc. the article that is entitled as " Coded b-directional relaying " delivered of people (particular content is referring to The 5th Scandianvian WS on wireless AD-hoc networks (AdHoc ' 05); Stockholm; Sweden May2005) improves traditional trunking scheme.Figure 1B and Fig. 3 show this two-way relay system of coding that is called as.

In the sequential schematic shown in Figure 1B, user U ₀With user U ₁Send the signal S that need transmit separately respectively ₀And S ₁To relay station, relay station detects two signal S ₀And S ₁, and with signal S ₀And S ₁Be superimposed, use a trunk channel to forward then.Since the broadcast characteristic of wireless channel itself, corresponding receiving terminal user U ₀With user U ₁Can both receive this superposed signal.In addition, because user U ₀With user U ₁All know the own signal that is sent exactly, the signal that receiving terminal deducts own transmission from composite signal just can extract the other side and send the signal of oneself to.Fig. 3 shows the block diagram of the wireless relay of the method that adopts people such as La Ersen.User U wherein ₀With user U ₁Send corresponding data symbol S through source transmitting channel 1 and 2 respectively ₀And S ₁ Single user detector 3,4 in the relay station receives user U respectively ₀With user U ₁The data symbol S that sends ₀And S ₁, and in modular two addition device 5 the data symbol S to receiving ₀And S ₁Carry out addition and obtain composite signal, transmit data symbol S through a trunk channel 6 then ₀And S ₁To corresponding receiving terminal.The signal that receiving terminal deducts own transmission from the composite signal that receives just can extract the other side and send the signal of oneself to.In Fig. 1, S ₀And S ₁Representative is defined in the information of finite field, and the addition of two symbols is for to be defined in the addition in the finite field gf (q) among the figure, and q is an order of modulation.

Can find out that accomplishing two-way communication with people's such as La Ersen method only needs 3 channels.If do not consider that because the flow loss that brings of transmission error, people's such as La Ersen method is compared with conventional method, its bandwidth efficiency has improved 1/3.In other words, under identical transmission bandwidth condition, its network throughput has improved 1/3.

In the wireless system of reality, the requirement to the transmission reliability of system sometimes will be higher than the requirement to the transmission availability of system.In wireless communications application, adopt diversity technique exactly through the method that is commonly used to improve transmission reliability.Worked out the multiple diversity technique that comprises multiaerial system.Multiaerial system can improve the validity and the reliability of wireless communication system effectively, but this method need dispose more antenna for transmitter and receiver, has increased hardware cost, also is unfavorable for the miniaturization and the microminiaturization of mobile device simultaneously.

In addition, in the multi-user and multi-channel wireless communication system, traditional transmission and trunking scheme are the independent allocated channel of each user, and each user uses separately independently its signal of channel transmission, be difficult to resist channel fading, thereby its transmission reliability is relatively poor; Draw and method that signal that the gloomy two-way trunking method of coding that waits the people is sent two users at relay station adopts mould two to add is superimposed; Use a trunk channel transmission; Compare with traditional relaying, per two users can use a channel less, have improved the validity of transmission.Yet people's such as La Ersen trunking method is not considered the reliability transmitted.

Summary of the invention

In view of the above problems; The purpose of this invention is to provide the multiuser transmission diversity in a kind of wireless communication system and send the concentrated method and system that continues of branch; The signal gathering that a plurality of users are sent is at the signal gathering point; And multiple user signals carried out linear transformation, will send into a plurality of channels through the signal of conversion then and transmit.

According to an aspect of the present invention, provide the many communication terminals transmissions in a kind of wireless communication system to divide collection and send the concentrated method that continues of branch, comprise step: said a plurality of communication terminals use source transmitting channel separately to send signal; Signal gathering point receives the signal that sends through said a plurality of communication terminals; The signal that said a plurality of communication terminals are sent carries out linear transformation; Use a plurality of channels to transmit the signal through linear transformation, each channel in said a plurality of channels is transmitted a linear combination of the signal of a plurality of communication terminals transmissions; Carry out demodulation with the signal of signal gathering point being transmitted at receiving terminal.

According to another aspect of the present invention, provide the many communication terminals transmissions in a kind of wireless communication system to divide collection and send the concentrated system that continues of branch, comprising: a plurality of transmitting terminals, use source transmitting channel separately to send signal; Relay station is used to receive the signal that sends through said a plurality of communication terminals, and the signal that said a plurality of communication terminals are sent carries out linear transformation, and transmits the signal through linear transformation; With a plurality of receiving terminals, the signal that relay station is transmitted carries out demodulation.

The present invention sends the website combined coding with multiple user signals at signal gathering, adopts a plurality of transmitting channels to send the signal of combined coding then.Because the signal of each transmitting channel of signal gathering website has all comprised a plurality of subscriber signals, thereby realized sending and divided collection, can improve the transmission reliability of wireless fading channel effectively.Simultaneously,, can change the bandwidth efficiency of system neatly, guarantee transmission availability through the transmitting channel quantity of selecting number of users and signal gathering to send website.Like this, transmission of the present invention divides collection and sends and divides that concentrating continues has taken into account transmission availability and two aspects of reliability.Simultaneously, at receiving terminal, transmission of the present invention divides collection and sends and divide concentrated continuing can adopt lattice type coding/decoding method to carry out Maximum Likelihood Detection to received signal, thereby the demodulated complex degree is low.

Description of drawings

The detailed description of below reading and understanding, with reference to accompanying drawing the preferred embodiment of the present invention being done will make of the present invention these become obvious with other purpose, characteristic and advantage.Wherein:

Figure 1A and 1B show respectively and between two users, pass through the sequential schematic that relaying is realized duplex communication in the prior art;

Fig. 2 shows the block diagram of traditional wireless relay;

Fig. 3 shows the block diagram of wireless relay of people's such as available technology adopting La Ersen method;

Fig. 4 representes that the user sends the sketch map that branch is concentrated the process that continues according to an embodiment of the invention, and the transmission that has wherein provided under two users' situation divides the process that continues of concentrating;

Fig. 5 is a sketch map of representing to divide in the transmission of N user, a N source transmitting channel, a N trunk channel according to another embodiment of the invention the concentrated process that continues;

Fig. 6 is a sketch map of representing to divide in the transmission of N user, a N source transmitting channel, a M trunk channel according to still a further embodiment the concentrated process that continues;

To be expression divide the block diagram of concentrating the system that continues according to the transmission of the N user of the embodiment of the invention, N source transmitting channel, M trunk channel to Fig. 7;

Fig. 8 is lattice type decoding algorithm is adopted in expression according to the embodiment of the invention a flow chart;

Fig. 9 is that QPSK and 16QAM transmission signal constellation (in digital modulation) sketch map and Gray's mapping as an example adopted in expression according to the present invention;

Figure 10 and Figure 11 show the comparison sketch map of multiuser transmission diversity relaying of the present invention and the bit error performance of traditional trunking method under the situation of using QPSK modulation and 16QAM modulation respectively;

Figure 12 shows the La Ersen two-way relaying of encoding and concentrates and continue when using the 8PSK modulation using QPSK modulation and two users of the present invention to send branchs, and the BER performance under the different bandwidth efficient situation compares sketch map;

Figure 13 shows the La Ersen relatively sketch map of two-way relaying and multiuser transmission diversity relaying of the present invention BER performance under same band efficient situation of encoding; With

The bit error performance compared sketch map when Figure 14 showed the down direction base station use of wireless cellular system and do not use multiuser transmission diversity.

Embodiment

With reference to the accompanying drawings to dividing the concentrated method and system that continues to be elaborated as multiuser transmission diversity in the wireless communication system of the embodiment of the invention and transmission; In the description process, having omitted is unnecessary details and function for the present invention, obscures to prevent understanding of the present invention caused.

As one embodiment of the present of invention, consider that at first 2 users in the wireless communication system pass through the situation that a relay station is realized two-way communication.Fig. 4 has provided under two users' situation, and the transmission of present embodiment divides the sketch map of concentrating the process that continues.

In order to improve the transmission reliability of wireless communication system, can consider to use 4 channels.Different with conventional method is that relay station is not to use two trunk channels to send two users' signal independently, but two signals are carried out linear combination, linear combination result of each channel transmission.Specifically, as shown in Figure 4, No. 0 trunk channel transmits two user U ₀And U ₁The signal S that sends ₀And S ₁With (S ₀+ S ₁), No. 1 trunk channel transmits two user U ₀And U ₁The signal S that sends ₀And S ₁Poor (S ₀-S ₁).Be noted that the addition and subtraction here is defined in complex field, and the use of people's such as La Ersen method is finite field operations.In other words, in process shown in Figure 4, S ₀And S ₁Representative is defined in the information of finite field gf (q), x ₀And x ₁Represent S respectively ₀And S ₁Complex signal point after q system constellation mapping.Each access channel has all comprised two users' signal now, thereby has realized sending the branch collection.

Yet, the invention is not restricted to two users, but can directly be generalized to N user.According to another embodiment of the invention, can at first consider N user, the situation of N source end transmitting channel and N trunk channel.N user uses 2N channel altogether, and on average each user uses 2 channels.Under two users' situation, the signal that two users is sent at relay station calculates signal poor of signal sum and the two transmission of the two transmission respectively.In fact, can regard this calculating as 2 point Fourier conversion or 2 Hadamard transforms.Be appreciated that when in communication system, having N user to communicate, at N under 2 the situation, can adopt conversion of N point Fourier or N point Hadamard transform.As N>2 the time, N point Hadamard transform has only when N is 4 integral multiple and could use, and Fourier transform can adopt and quadrature for any natural number N.Therefore can use Fourier transform to divide the collection matrix as sending.That is to say, after relay station detects the signal code of N information source transmission, use fourier matrix that this N point signal code is carried out linear transformation, the N that an obtains result is sent into N trunk channel send.At this moment, the signal that sends to each access channel all is the linear combination of N user's signal code, has comprised a plurality of users' signal, thereby has realized sending the branch collection.The transmission of N user, N source transmitting channel, (N)-relay channel divide concentrate continue as shown in Figure 5.In Fig. 5, z _iBe x ₀, x ₁..., x _N-1The result of linear combination, wherein x _jBe the signal s that the user sends _jComplex signal point i after q system constellation mapping, j=0,1 ..., N-1.

In the wireless communications application of reality, need take into account validity and two aspects of reliability of transmission sometimes.At this moment, can adopt N user as shown in Figure 6, N source transmitting channel, M trunk channel to send diversity mode.The block diagram of this system (will be described later) as shown in Figure 7.When N < during M, adopts the method for Fig. 5 to encode, but only sends preceding M linear combination result shown in Figure 5.If N is>M can get the complex signal point x after the constellation mapping ₀, x ₁..., x _N-1And the volume of being total to, use the matrix of a linear transformation on 2N rank that it is carried out linear transformation (at this, supposing that M is less than or equal to 2N) then.Then, will preceding M element correspondence in the sequence that conversion obtains sending into M trunk channel sends.Because total channel quantity is (M+N), on average the number of channel of each user's use is (M+N)/N.The value of this explanation change N and M is the bandwidth efficiency of configuration-system neatly.Simultaneously,, thereby realized sending and divided collection, and guaranteed the reliability of signal transmission because the signal that each channel transmits all comprises a plurality of users' signal.

Fig. 7 shows according to multiuser transmission diversity of the present invention and the block diagram that sends the concentrated system that continues of branch.This system comprises a plurality of user U1 as transmitting terminal, U2 ..., Un, relay station 71 and as a plurality of user U1 of receiving terminal, U2 ..., Un.Comprise single user detector 711,712 in the relay station 71 ..., 71n, and multi-user association encoder 72.As an example, transmitting terminal and receiving terminal can be such as cell phone, PDA(Personal Digital Assistant), the mobile communication terminal of portable computer and so on.In addition, at user terminal (mobile communication terminal) U1, U2 ..., comprise demodulator 731,732 among the Un ..., 73n.As an example, can adopt lattice type sign indicating number demodulator.Be noted that to the invention is not restricted to this, also can adopt the demodulator of other type.

The user that the embodiment of the invention is described below sends the branch collection and sends the operation that divides the concentrated system that continues.As a plurality of user U1 of transmitting terminal, U2 ..., Un passes through source transmitting channel 1,2 ..., N transmission signal separately is to relay station 71.Single user detector 711,712 in the relay station 71 ..., 71n detects a plurality of user U1 respectively, U2 ..., Un passes through source transmitting channel 1,2 ..., the signal that N sends.After this, detected subscriber signal is offered multi-user association encoder 72, multi-user association encoder 72 adopts fourier matrix that this N point signal code is carried out linear transformation, the N that an obtains result is sent into M trunk channel send.At this moment, the signal that sends to each access channel all is the linear combination of N user's signal code, has comprised a plurality of users' signal, thereby has realized sending the branch collection.Be noted that and adopt fourier matrix that this N point signal code is carried out linear transformation in the present embodiment.Yet, the invention is not restricted to this, also can adopt other linear transformation method, for example, Hadamard transform.In the processing of multi-user association encoder 72, as the quantity M of relaying channel<during N, z _iBe x ₀, x ₁..., x _N-1The result of linear combination.As M>N, z _iBe x ₀, x ₁..., x _N-1And the result of the linear combination of the volume of being total to.x _jBe s _jComplex signal point i=0 after q system constellation mapping, 1 ..., N-1, j=0,1 ..., M-1.Then, will preceding M element correspondence in the sequence that conversion obtains sending into M trunk channel sends.Because total channel quantity is (M+N), on average the number of channel of each user's use is (M+N)/N.Receiving terminal U1, U2 ..., the lattice type sign indicating number demodulator 731,732 among the Un ..., 73n divides the concentrated signal that continues to carry out demodulation to the transmission that receives, and finally recovers the primary signal that transmitting terminal sends.

(particular content can be referring to IEEE Trans.Inform.Theory for the article that is entitled as " A universal lattice code decoder forfading channel " that E.Viterbo and J.Boutros deliver; Vol.45; July1999, pp.1639-1642); O.Damen; (particular content can be referring to IEEE Communication Letters for the article that is entitled as " Lattice code decoder for space-time codes " that A.Chkeif and J.C.Belfiore deliver; Vol.4 (5), May2001, pp.161-163); The article that is entitled as " A new reduced-complexity sphere decoder for multipleantenna systems " that A.M.Chan and I.Lee deliver (particular content can be referring to In ICC02, vol.1,, May2002, pp.460-464); And the article that is entitled as " Application of lattice codedecoder to SC-CP for short block length " delivered of X.Li and X.Cui (particular content can be referring to IEEElectronics letters; Vol.40 (15); July2004, pp.954-955) plaid matching type sign indicating number is described.To obscure in order preventing understanding of the present invention caused, to have omitted described at this.

Multiuser transmission diversity is applicable to the situation that a portable terminal uses a plurality of channels and a plurality of portable terminal to communicate.Typical example is that independently wireless channel and M portable terminal communicate (can establish M < N) through N for base station in the cellular system.Consider downlink communication, the linear conversion of N point is at first carried out with N subscriber signal in the base station, uses then and uses M channel to send preceding M signal after the conversion.This has just realized that the multi-user directly sends the branch collection.

In fact, in multi-user wireless communication system,, that is, exist signal gathering to send website, can use transmission deversity scheme of the present invention and improve transmission reliability as long as exist some subscriber signals to converge at certain any situation.

Use multiuser transmission diversity, receiving signal is the results of a plurality of subscriber signals after linear transition coding matrix and channel matrix effect, and what each receive channel obtained all is multi-user's composite signal.In order to obtain optimum detection performance, can use maximum likelihood detection method.When number of users and order of modulation were all very little, can be direct exhaustive the burst that might send carried out Maximum Likelihood Detection.But when number of users or order of modulation were higher, the complexity of the method for exhaustion was too high, is can not be receptible in real system.Therefore,, proposed the multiuser transmission diversity signal and can be expressed as the form of lattice type sign indicating number, carried out Maximum Likelihood Detection to sending diversity signal thereby can use lattice type decoding algorithm at receiving terminal as an instance of the present invention.Therefore, can be with send to divide collection and send to divide that concentrating continues and convert lattice type code calculation to and handle.Be appreciated that to the invention is not restricted to this, also can adopt other decoding algorithm.

In order to understand the present invention better, multiuser transmission diversity of the present invention is described below divides concentrated continuing and the expression of lattice type yardage with transmission.

Can consider a plurality of user terminal direct communications or the wireless system of communicating by letter through the relaying completion.At this, need not consider that which two users or which user of multi-user in organizing communicates, and accomplishes because this work can be given the upper strata.The signal gathering that can establish N user terminal transmission is sent to the purpose user terminal by this convergent point then in a certain website.For the system of a user terminal and a plurality of user terminal direct communications, be example with communicating by letter between the base station in the wireless cellular system and a plurality of mobile radio stations, can be with the source end subscriber, just the base station is as user's convergent point.For the system that a plurality of users transmit through relay station, relay station can be used as the convergent point of subscriber signal.Because convergent point is identical to the mode that a plurality of user terminals send signal, will be that example is described below with the trunking scheme.Be appreciated that and the invention is not restricted to this.

In order to be without loss of generality, can suppose that N user terminal uses N source transmitting channel and N trunk channel to communicate through relay station, as shown in Figure 5.At first, each user terminal use one independently the source transmitting channel send signal to relay station.Relay station detects the signal that N information source send and transmits.Because each user uses a source transmitting channel, use single user detector to detect the signal of each user terminal independently at relay station, this detection method is simple and complexity is low.Therefore the input of transmission of relay station signal and final receiving station will be described below.

Can establish the signal phasor that the detected N of a relay station user sends is x _s=[x ₀, x ₁..., x _N-1] ^T, x wherein _i(i=0,1 ..., N-1) be detected i subscriber signal.Subscript T representing matrix transposition wherein.Different users can use different modulation modes, also can use different transmitted powers.For simplicity and be without loss of generality, use identical modulation system and transmitted power at these all user terminals of supposition of can deriving.Collect the signal x that the matrix that the formula (1) below relay station uses provides sends the user for realizing sending dividing _s=[x ₀, x ₁..., x _N-1] ^TCarry out linear transformation.

Wherein W satisfies W ^HW=WW ^H=I is the matrix of a linear transformation.Can use N rank hadamard matrix or fourier transform matrix.When for example adopting the Fourier transform battle array, can obtain $W_{u,v}=\frac{1}{\sqrt{N}}\mathrm{Exp}(-2\mathrm{\&pi;\; Uvj}/N)$ (u, v=o, 1 ..., N-1).In order to be without loss of generality, can suppose that user U0 detects to received signal.If it is H that user U0 observes the path loss of i trunk channel _i(i=0,1 ..., N-1) and suppose that the recipient accurately estimates channel information.So the signal phasor that user U0 receives can be used following formula (2) expression.

V=[v in the formula ₀, v ₁..., v _N-1] ^TFor receiving signal phasor, n=[n ₀, n ₁..., n _N-1] ^TRepresent the Gaussian noise vector, wherein n _i(i=0 ..., be to be distributed as n N-1) _i～CN (0, N ₀) the multiple Gaussian noise of independence.Be noted that user terminal U0 knows the own signal that is sent fully, this known signal is eliminated from receive signal, can obtain following formula (3).

In the superincumbent formula (3), for simplicity, can make y=[y ₀, y ₁..., y _N-1] ^T, the signal and the noise at other terminal that expression user terminal U0 is received, x=[x ₁..., x _N-1] ^TAnd H=[H _iW _{I, j}] (i, j=0,1 ..., N-1), rewriting formula (3) obtains the reception signal by following formula (4) expression.

y＝H·x+n(4)

For complex vector or complex matrix z, can introduce mark z=z _I+ jz _Q, z wherein _IAnd z _QRepresent its real part and imaginary part respectively.Like this, formula (4) can further be expressed as formula (5).

$\left[y_I^T{y}_Q^T\right]=\left[x_I^T{x}_Q^T\right]\left[\begin{array}{cc}{H}_I^T& H_Q^T\\ -H_Q^T& H_I^T\end{array}\right]+\left[n_I^T{n}_Q^T\right]---\left(5\right)$

At this, can make $r=\left[y_I^T{y}_Q^T\right],$ $u=\left[x_I^T{x}_Q^T\right],$ $\mathrm{\&eta;}=\left[n_I^T{n}_Q^T\right]$ And $A=\left[\begin{array}{cc}{H}_I^T& H_Q^T\\ {-H}_Q^T& H_I^T\end{array}\right],$ So can formula (5) be expressed as following formula (6).

r＝u·A+η (6)

Like this, the multiuser transmission diversity signal just has been expressed as the lattice type sign indicating number form of standard at receiving terminal.In the superincumbent expression formula (6), A is equivalent to the trellis code generator matrix of one 2 (N-1) * 2N, and u is equivalent to 1 * 2 (N-1) coordinate vector of trellis code.So, can adopt lattice type decoding algorithm that the multiuser transmission diversity signal is carried out Maximum Likelihood Detection at receiver end.

The algorithm of following plaid matching type decoding is described.At this, be that example is explained lattice type decoding algorithm with the lattice type sign indicating number problem of above-mentioned 2 (N-1) * 2N rank generator matrixes.

Can establish L ₁=2N, L ₂=2N-2.Thereby will seek the problem that multiuser transmission diversity receives the maximum likelihood sequence of signal and in fact be converted into such problem, that is, in all possible transmission sequence, choose vector u and make ‖ r-uA ‖ minimum.At this, symbol ‖ ‖ representes the general number of euclidean (Euclidean).Promptly change into the problem of formula (7) expression

argmin‖r-u·A‖?(7)

For simplicity, can establish ω=r-uA.Owing to known matrix A exactly, therefore, can establish r=ρ A, and $\mathrm{\&rho;}=[{\mathrm{\&rho;}}_1,{\mathrm{\&rho;}}_2,\&CenterDot;\&CenterDot;\&CenterDot;{,\mathrm{\&rho;}}_{L_2}]=r\&CenterDot;A^{+}.$ At this, the pseudoinverse of matrix is asked in subscript+expression.Get ξ=ρ-u ω=ξ A is then arranged.Like this, minimization ‖ r-uA ‖ can equivalence be minimization ‖ ω ‖ just ²‖ ω ‖ ²Can be expressed as formula (8).

‖ω‖ ²＝(ξ·A)(ξ·A) ^T＝ξ(AA ^T)ξ ^T(8)

Can make G=AA ^TBecause G is a symmetric positive definite matrix, therefore can uses Cholesky to decompose it is decomposed into G=R ^TR, the R in the formula (8) can be expressed as the upper triangular matrix that provides like following formula (9).

Like this, ‖ ω ‖ ²But the form that provides of telogenesis such as following formula (10) just,

Can given in advance constant C, then with this process as being to seek to make ‖ ω ‖ ²The vector ξ of≤C.Just seek ξ, following inequality (11) is set up.

$\underset{i=1}{\overset{L_2}{\mathrm{\&Sigma;}}}{(r_{\mathrm{ii}}{\mathrm{\&xi;}}_i+\underset{j=i+1}{\overset{L_2}{\mathrm{\&Sigma;}}}{r}_{\mathrm{ij}}{\mathrm{\&xi;}}_j)}^2\&le;C---\left(11\right)$

For inequality (11) is set up, following formula (12) is arranged then

$\underset{i=s}{\overset{L_2}{\mathrm{\&Sigma;}}}{(r_{\mathrm{ii}}{\mathrm{\&xi;}}_i+\underset{j=i+1}{\overset{L_2}{\mathrm{\&Sigma;}}}{r}_{\mathrm{ij}}{\mathrm{\&xi;}}_j)}^2\&le;C---\left(12\right)$

To s=L ₂, L ₂-1 ..., 1 all should set up.So, can establish $q_{\mathrm{Ii}}={\mathrm{<figure-callout\; id="2"\; label="r\; Ii"\; filenames="S06189984020060620E000023.png,S06189984020060620E000053.png"\; state="\{\{state\}\}">r</figure-callout>}}_{\mathrm{Ii}}^{},i={\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="S06189984020060620E000023.png,S06189984020060620E000053.png"\; state="\{\{state\}\}">L</figure-callout>}}_2,L_2-1,\&CenterDot;\&CenterDot;\&CenterDot;,1$ And q _Jj=r _Ij/ r _Ii, i=L ₂, L ₂-1 ..., 1, j=i+1, i+2 ... L ₂Use these symbols and rewrite formula (12) formula, can obtain following inequality (13),

$\underset{i=s}{\overset{L_2}{\mathrm{\&Sigma;}}}{q}_{\mathrm{ii}}{({\mathrm{\&xi;}}_i+\underset{j=i+1}{\overset{L_2}{\mathrm{\&Sigma;}}}{q}_{\mathrm{ij}}{\mathrm{\&xi;}}_j)}^2\&le;C,s=\mathrm{1,2},\&CenterDot;\&CenterDot;\&CenterDot;,L_2---\left(13\right)$

Can be from s=L ₂Begin to carry out inverse iteration.Get s=L ₂, solve from inequality (13)

The scope of component is represented with formula (14).

Inequality (14) the symbol and

, respectively, for α to the positive and negative infinity direction rounding operation.Can draw the scope of the correspondence

of inequality (15) expression for each

of satisfying inequality (14).

If got fixed

then get s=i, use inequality (13) and obtain expression (16).

i＝L ₂，L ₂-1，…，1(16)

Can be provided with $S_i=S_i({\mathrm{\&xi;}}_{i+1},\&CenterDot;\&CenterDot;\&CenterDot;,{\mathrm{\&xi;}}_{L_2})={\mathrm{\&rho;}}_i+\underset{t=i+1}{\overset{L_2}{\mathrm{\&Sigma;}}}{q}_{\mathrm{It}}{\mathrm{\&xi;}}_t.$ In addition, can be provided with $T_{i-1}=T_{i-1}({\mathrm{\&xi;}}_i,\&CenterDot;\&CenterDot;\&CenterDot;,{\mathrm{\&xi;}}_{L_2})=C-\underset{t=i}{\overset{L_2}{\mathrm{\&Sigma;}}}{q}_{\mathrm{Tt}}{({\mathrm{\&xi;}}_t+\underset{j=t+1}{\overset{L_2}{\mathrm{\&Sigma;}}}{q}_{\mathrm{Tj}}{\mathrm{\&xi;}}_j)}^2=T_i-q_{\mathrm{Ii}}{(S_i-u_i)}^2.$ When i=1, the vector that obtains $u=[{\mathrm{<figure-callout\; id="2"\; label="u\; L"\; filenames="S06189984020060620E000023.png,S06189984020060620E000053.png"\; state="\{\{state\}\}">u</figure-callout>}}_{L_{}},u_{L_2-1},\&CenterDot;\&CenterDot;\&CenterDot;,u_1]$ Should be hypersphere ‖ ω ‖ ²A point the in≤C.In addition, following expression (17)

${\hat{d}}^2=C-{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="S06189984020060620E000023.png,S06189984020060620E000051.png"\; state="\{\{state\}\}">T</figure-callout>}}_1+q_{11}{(S_1-u_1)}^2---\left(17\right)$

Expression point u and actual reception signaling point are at hypersphere ‖ ω ‖ ²Distance in the≤C.If this distance is less than C, then the value of C is upgraded in use

, carries out iteration once more.Make ‖ ω ‖ when can not find a new u ²Then stop iteration during≤C, what will obtain last time simultaneously satisfies ‖ ω ‖ ²The vector u of≤C exports as detector.

According to above-mentioned derivation, Fig. 8 gives the flow chart of offscale type decoding algorithm.In Fig. 8, γ representes the component u of vector u _i(i=1,2 ..., L ₂) value set.For example, if use QPSK and 16QAM constellation, γ be respectively 1,1} and 3 ,-1,1,3} (as shown in Figure 9).In addition, length (L _i, U _i, γ) be illustrated in lower bound L _iWith upper bound U _iBetween from the element number that can get of set γ, enum (L _i, U _i, γ) all these elements, sort (y are enumerated out in expression _i, S _i) represent y _iElement is to S _iAsk distance, and these elements are sorted by distance from small to large.Attention parameters L ₁=2N, L ₂=2N-2.Decoding algorithm is described below.At first; At step S801; The signal that sends according to the signal that receives and this terminal calculates vector r with channel parameter and transmission encoder matrix; Trellis code generator matrix A, and be provided with original ball radius

(because Alberta. the work of money (A.M.Chan), this convergence does not rely on choosing of initial value; Convergence rate is also basic, and it doesn't matter with initial value, and therefore needing only has the signaling point just passable in the selected original ball).Determine signal set γ according to sending signal constellation (in digital modulation).With the r that is determined, A, C and γ input as decoding algorithm.After this, at step S802, calculate symmetric positive definite matrix G=AA ^T, and use the Cholesky decomposition that matrix G is decomposed into G=RR ^T, wherein R is a upper triangular matrix.Element according to matrix R calculates q _Ii, i=L ₂, L ₂-1 ..., 1 and q _Ij, i=L ₂, L ₂-1 ..., 1, j=i+1, i+2 ..., L ₂The pseudoinverse A of compute matrix A ⁺, and obtain ρ=A in view of the above ⁺R.Next, at step S803, the original ball radius C is composed the distance metric d that need use to iterative process ²And the back is to the iteration parameter

With

Adopt count value i record back to the iteration step position.At step S804, be provided with.Count value was L when iteration began ₂Then, at step S805, this iteration count value is along with the carrying out of iteration will be revised by step S814.For i=L ₂, at first calculate the upper and lower bound that acceptance point maybe value according to front (14) formula And

Calculating the signal that can get according to signal value set γ counts

And these signaling points are enumerated out to obtain enumerating vector

Then according to these signaling points with

Distance sort from small to large, obtain vector

For i step iteration, use x _iAs i step signaling point counter, the signal that record had been soundd out is counted.For example for L ₂In the step, possible signaling point quantity does

Therefore the signaling point quantity that possibly sound out at most does

At step S806, signaling point counter x _iAdd 1, point to i and go on foot the signaling point that to sound out.At step S807, detect and whether all signaling points in i step are all soundd out.If x _i>N _i, explain and all sound out, show from i to go on foot the path that i-1 does not have P Passable.Turn to step S808 this moment, and at step S808 detection counter i, if this count value is L ₂, explain at the current radius of a ball

Do not comprise any signaling point in the ball of being searched for down.In this case; Forward step S810 to, will walk to lead to and write down signaling point

sphericity amount parameter

output and the terminator that obtain last time.If step S808 finds that count value i is less than L ₂, then turning to step S809, counter i adds 1, returns backward, turns to S806 to begin to sound out one and goes on foot the signaling point of not souning out as yet.At step S807, if x _i≤N _i, then turn to step S811 to carry out x _iThe exploration of signaling point.At step S811, detection counter i.If i=1 explains successfully to feel out a paths.Turn to step S815 this moment, calculates this path metric (this path respective signal is put the distance of acceptance point).Judge at step S816 whether the tolerance that newly obtains is littler than existing record tolerance.If new tolerance is littler, the signaling point that the signaling point that newly obtains is superior to writing down is described.Forward step S817 this moment to, adopt new signal point tolerance to upgrade tolerance d ²And other parameter, forward step S806 then to and carry out the next round iteration.If step S816 judges that the metric that newly obtains is bigger than the record tolerance of record, abandon this signaling point, flow process turns to step S806 to sound out next signaling point in this step.At step S811, if i>1 establishment, read-me also mediates the step, turns to step S812 this moment.Calculate iterative parameter T at step S812 _I-1And ξ _i, calculate S at step S812 then _I-1, and, turn to step S805 to begin new round iteration then at step S814 modification counter i.

Figure 10 to Figure 14 shows based on multiuser transmission diversity of the present invention respectively and send to divide concentrates and continues and tradition is sent and traditional relaying, and with the encode bit error performance comparison result of two-way relaying of La Ersen.Employed channel is a rayleigh fading channel in contrast, and to different user, different channels, various information source symbol packets, its channel independent random changes, and promptly employed channel is a fast fading channel.In the instance that provides, when having relay station, each sends the symbol energy mean allocation to information source station and relay station.The modulation system that all users use is identical.At the signal gathering point, send diversity mode and use fourier transform matrix that multiple user signals is encoded, send the purpose of dividing collection to reach.For trunking method, relay station receives signal and then the forwarding that send at the information source station.For multiuser transmission diversity, final reception user uses lattice type coding/decoding method that signal is carried out Maximum Likelihood Detection.

Figure 10 and Figure 11 show multiuser transmission diversity relaying of the present invention and the bit error performance comparison result of traditional trunking scheme when using the QPSK modulation respectively.Wherein Figure 10 representes is to be 1 hertz in every channel width, and then bandwidth efficiency is the comparative result under 1 bps/hertz the situation.What Figure 11 represented is that bandwidth efficiency is 2 bps/hertz comparative results under the situation in the 16QAM modulation.Can find out that the BER performance increases with the number of users of combined coding and improves, when number of users was very big, to QPSK and 16QAM, multiuser transmission diversity all can provide about 3 decibels performance gain (among the figure with the reference of 16 users as infinite number of users).When number of users is smaller, increases number of users and can improve the bit error performance comparatively significantly.But when number of users is big, increases number of users and just can not bring tangible performance improvement.For example, for QPSK, 2 users unite the transmission of branch collection can provide 2.1dB gain, and 2.6dB is provided during 6 users gain.For 16QAM, 2 users unite the transmission of branch collection can provide 1.7dB gain, and 2.1dB is provided during 6 users gain.During practical application, can the number of users of uniting the transmission of branch collection suitably be chosen, and need not be provided with too greatly according to performance and complexity requirement.

Figure 12 shows the La Ersen two-way relaying of encoding and concentrates and continue when using 8PSK to modulate (1.5 bps/hertz of bandwidth efficiencies) comparative result of the BER performance during different bandwidth efficient using QPSK modulation (1.33 bps/hertz of bandwidth efficiencies) and 2 users to send branchs.As can beappreciated from fig. 12, the BER performance of the two is basic identical.Because 2 users send branch and concentrate the bandwidth efficiency that continues to be higher than the bandwidth efficiency of La Ersen relaying, so removal is owing to transmit the flow loss that mistake is brought, 2 users send concentrated the continuing of branch and have realized the clean throughput of higher network.

Figure 13 shows the La Ersen two-way relaying of encoding and concentrates to continue and using 16QAM to modulate using 8PSK modulation and 2 users to send branchs, and bandwidth efficiency is identical, the comparative result of BER performance when being 2 bps/hertz.Can see that from Figure 13 according to scheme of the present invention, 2 users send branch and concentrate the BER performance that continues to be superior to the performance of La Ersen relaying.For example, be 10 at BER ^-4The time, 2 users send concentrated the continuing of branch and are superior to the about 1.7dB of La Ersen relaying.Equally, remove owing to transmit the flow loss that mistake is brought, 2 users send concentrated the continuing of branch and have realized the clean throughput of higher network.

Figure 14 shows a user and a plurality of user's direct communication; For example communicate by letter between the base station in the radio honeycomb communication system and a plurality of mobile radio stations; Use when not using multiuser transmission diversity the bit error performance comparison result when using QPSK modulation (2 bps/hertz of bandwidth efficiencies).Bit error performance when as can beappreciated from fig. 14, multiuser transmission diversity of the present invention obviously is superior to being regardless of collection.The number of users that increases combined coding is to improving playing a role clearly of performance.Simultaneously, can also see that multiuser transmission diversity is much obvious to the improvement of the performance improvement when having relaying.This is that the transmission from the information source station to relay station can cause transmission error because for multi-user's relay system, and this mistake can limit to a great extent sends the improvement that divides the set pair performance.This explanation is in actual multiuser transmission diversity relay system, and improving first section transmission performance is vital to the transmission performance that improves whole system.The method that improves first section transmission performance is a lot, for example uses suitable chnnel coding, is source station distribution ratio relay station more power etc.

The present invention sends the website combined coding with multiple user signals at signal gathering, adopts the signal of a plurality of transmitting channels transmission combined codings then, and in addition, transmission of the present invention divides collection and sends and divide concentrated continuing to take into account transmission availability and reliability.Simultaneously, at receiving terminal, transmission of the present invention divides collection and sends and divide concentrated continuing can adopt the method such as the decoding of lattice type to carry out Maximum Likelihood Detection to received signal, thereby the demodulated complex degree is low.

So far invention has been described in conjunction with the preferred embodiments.It should be appreciated by those skilled in the art that under the situation that does not break away from the spirit and scope of the present invention, can carry out various other change, replacement and interpolations.Therefore, scope of the present invention should not be understood that to be limited to above-mentioned specific embodiment, and should be limited accompanying claims.

Claims (16)

1. the many communication terminals in the wireless communication system send and divide collection and send to divide and concentrate the method that continues, and comprise step:

A plurality of communication terminals use source transmitting channel separately to send signal;

Signal gathering point receives the signal that sends through said a plurality of communication terminals, and the complex signal that the signal that said a plurality of communication terminals are sent obtains through constellation mapping carries out linear transformation,

Use a plurality of channels to transmit the complex signal through linear transformation, each channel in said a plurality of channels is transmitted a linear combination of complex signal; With

The signal of the lattice type sign indicating number form of signal gathering point being transmitted at receiving terminal carries out demodulation.

2. method according to claim 1, the step of wherein complex signal being carried out linear transformation comprise and adopt Fourier transform that complex signal is carried out conversion.

3. method according to claim 1, the step of wherein complex signal being carried out linear transformation comprise and adopt Hadamard transform that complex signal is carried out conversion.

4. the step that method according to claim 1, the signal of the lattice type sign indicating number form of wherein signal gathering point being transmitted at receiving terminal are carried out demodulation comprises uses lattice type coding/decoding method the signal of the lattice type sign indicating number form that receives to be carried out the step of Maximum Likelihood Detection.

5. method according to claim 1, wherein said signal gathering point is a relay station.

6. method according to claim 1, wherein said signal gathering point is the base station.

7. method according to claim 1; Wherein have N independently source transmitting channel and M said channel; And under the situation of M＜N; Said signal gathering point carries out linear transformation to the constellation mapping complex signal of the signal that receives through N source transmitting channel, then through preceding M signal after said M the channel forwarding conversion.

8. method according to claim 1, wherein employed channel comprises the time slot of time-division system.

9. method according to claim 1, wherein employed channel comprises the code channel of yard subsystem.

10. method according to claim 1, wherein employed channel comprises the frequency band of frequency division systems.

11. method according to claim 1, wherein employed channel comprises the time slot of time-division system, the combination of the code channel of sign indicating number subsystem and the frequency band of frequency division systems.

12. the many communication terminals in the wireless communication system send and divide collection and send to divide and concentrate the system that continues, and comprising:

A plurality of transmitting terminals use source transmitting channel separately to send signal;

Relay station is used to receive the signal that sends through said a plurality of transmitting terminals, and the complex signal that the signal that said a plurality of transmitting terminals are sent obtains through constellation mapping carries out linear transformation, and transmits the complex signal through linear transformation; With

A plurality of receiving terminals, the signal of the lattice type sign indicating number form that relay station is transmitted carries out demodulation.

13. system according to claim 12; Wherein said relay station also comprises the multi-user association code device; Be used for the complex signal that the signal that said a plurality of transmitting terminals send obtains through constellation mapping is carried out linear transformation; And using a plurality of channels to transmit complex signal through linear transformation, each channel in said a plurality of channels is transmitted a linear combination of complex signal.

14. system according to claim 13, wherein said multi-user association code device adopts Fourier transform that complex signal is carried out conversion.

15. system according to claim 13, wherein said multi-user association code device adopts Hadamard transform that complex signal is carried out conversion.

16. system according to claim 12, wherein said receiving terminal comprises lattice type sign indicating number demodulator, is used for the signal of the lattice type sign indicating number form that receives is carried out lattice type decoding operation, so that the signal of the lattice type sign indicating number form that receives is carried out Maximum Likelihood Detection.

Images