CN102739383B - Method for allocating union resource based on limited feedback OFDM-AF (Orthogonal Frequency Division Multiplexing-Audio Frequency) system - Google Patents

Abstract

The invention discloses a method for allocating union resource based on a limited feedback OFDM-AF (Orthogonal Frequency Division Multiplexing-Audio Frequency) system. The method comprises the following steps: a resource allocation policy code book necessary for limited feedback is designed, wherein each code word in the code book is an independent complete power allocation and sub-carrier matching scheme; an information destination D matches an estimation value with the designed code book based on the channel estimation to a communication system, and carries out ergodic search and selects an optimal code word in the code book; the information destination D broadcasts a subscript with the optimal code word; and an information source S and a relay R with the same code book transcripts transmit corresponding code words in accordance with the received subscripts respectively. With the adoption of the method, the system performance can be improved greatly under the condition of extremely few feedback bits; the performance loss when a transmitter has no channel information is made up; and meanwhile the defect that the complete channel information feedback in a traditional OFDM system cannot be realized is overcome; and the method is applicable to more practical communication scenes.

Description

The system combined resource allocation methods of OFDM-AF based on Limited Feedback

Technical field

The present invention relates to the federated resource distribution method of wireless communication field, the federated resource that specifically OFDM amplifies-forwards based on Limited Feedback in (Amplify-and-Forward, AF) relay diversity system distributes.

Background technology

Along with people's improving constantly communicating requirements such as high accuracy, high reliability, strong flexibilities, its non-ideal characteristic problems such as the serious decline that causes due to the continuous expansion of communication range and the more complicated various of communication environment and intersymbol interference that solve just seem particularly important.Its immediate solution is exactly adopt the Radio Transmission Technology that spectrum efficiency is higher, anti-multipath jamming ability is stronger in a wireless communication system.In multiple wireless solution, with the relaying technique that can significantly improve power system capacity with OFDM be representative multi-carrier modulation technology with can show one's talent.In relay cooperative communication system, information source is while sending message to the stay of two nights, and via node also can receive this message simultaneously, after by its directly amplification or decoding recompile, be transmitted to the stay of two nights.The stay of two nights is combined and is utilized all message received to decode.Junction network is equal to not needing, under the condition configuring multiple antennas, to provide certain relay cooperative diversity, while expansion communication, improve communication quality.Based on the efficient availability of frequency spectrum of OFDM technology, and superior anti-multipath fading ability, the relaying technique based on OFDM modulation has become the key technology for PHY of future mobile communication system.

Based on the finiteness of system transmitted power budget, and the independence that the sub-carrier channels in junction network in multi-hop declines, power division and subcarrier coupling have become problem demanding prompt solution in OFDM relay system.

But, no matter be power division, or be subcarrier coupling, all need could realize under the prerequisite obtaining network channel information.Due to the complexity of communication environment and the random mobility of terminal, power allocation vector and subcarrier matching vector must change along with the change of channel status.Because traditional channel reciprocity method is no longer proved effective in carrier frequency subsystem, current industry is main it is considered that forward channel status information is fed back to transmitting terminal by reverse link.But in multi-carrier systems, roundabout delayed owing to existing, the restriction of the factors such as the capacity that channel estimation errors, feedback link are limited and the restriction of code book scale, complete channel information feedback is difficult to realize, the proposition of Limited Feedback technology, effectively overcomes this problem.

Due to the inherent distributed nature of relay cooperative network, be directed to the Limited Feedback research of OFDM junction network and and immature.

N.Zhou and X.Zhu etc. are in 2009 IEEE International Conference on Communications meeting article " Dynamic Resource Allocation with Limited Feedback for OFDM Based CooperativeNetworks ", consider a kind of asymmetric relay transmission structure based on Limited Feedback, add the degree of freedom that system power distributes, but author only considered power division for this model.Above-mentioned achievement carried out expanding in the paper " Optimal asymmetric resource allocation with limitedfeedback for OFDM based relay systems " of IEEETrans. ~ Commun. periodical in 2010 again by they.The people such as Hajiaghayi are in the IEEE InternationalConference on Communications meeting paper " Using Limited Feedback in Power AllocationDesign for a Two-Hop Relay OFDM System " of 2009, discuss the power division of the double bounce AF junction network based on OFDM modulation, author is respectively using maximized system capacity with minimize error sign ratio and carry out algorithm for design as target.Although the document is not discussed to the subcarrier coupling of double bounce, its thought based on Lloyd algorithm is widely adopted.Utilize similar method, propose similar power distribution algorithm in the article of Zhang on Chinese Journal of Electronics " Power Allocation inDecode-and-Forward Cooperative OFDM Systems Using Perfect and Limited Feedback ", but it discusses the DF junction network to liking based on OFDM.F.Li, the article " A relay selection scheme with limit feedback in OFDM relay networks based onsubcarrier mapping " that the people such as X.Ke deliver in 2010IEEE Youth Conference on Information Computing and Telecommunications meeting discusses the relay selection scheme based on Limited Feedback, although the document relate to the coupling of subcarrier, author does not have power division limited in analytical system.Liu Yonghe Chen Wen considered the power division of the AF network based on Limited Feedback in 2011 in IEEE InternationalConference on Communications meeting article " Capacity Based Adaptive Power Allocation forthe OFDM Relay Networks with Limited Feedback ", but in this section of document, author does not consider subcarrier coupling.

Summary of the invention

The object of the invention is to overcome the deficiencies in the prior art, federated resource distribution method based on Limited Feedback in a kind of OFDM amplification-forwarding (AF) relay diversity system is provided, the method utilizes iteration Lloyd algorithm to be divided into independently subspace to channel matrix space, integer is utilized to limit the method for serialization and Lagrange duality decomposition, dexterously mixed integer programming problem to be optimized is solved, and constructing algorithm center criterion based on this, the feedback eventually through stay of two nights limit bit realizes system power and distributes and subcarrier coupling.The present invention has the features such as real-time operation is simple, complexity is low, overhead is few, and data display only needs little bit number, just can make up the performance loss of the system overwhelming majority.

Relay diversity system of the present invention is a kind of single antenna communications system, and this communication system is made up of three nodes, i.e. 1 information source S, 1 AF relaying R and 1 stay of two nights D.Information source, the stay of two nights and relaying are single antenna configuration.The present invention also supposes to there is direct link between information source and the stay of two nights.Subscript, after the subscript choosing Resourse Distribute vector, is sent to information source and relaying by feedback link by the stay of two nights.

In order to make full use of the extra channel degree of freedom that relaying brings, the whole transmitting procedure of collaborative network of the present invention is divided into two time slots.Information source is at the first time slot radio transmission signal, and the stay of two nights and relaying receive respectively, and both Received signal strength are:

$y_{\mathrm{rm}}=\sqrt{P_S^m}{h}_{\mathrm{SR}}^m{s}_m+z_{\mathrm{rm}},$

$y_{\mathrm{dm}}^{\left(1\right)}=\sqrt{P_S^m}{h}_{\mathrm{SD}}^m{s}_m+z_{\mathrm{dm}}^{\left(1\right)},$

The wherein noise introduced for each node of z, subscript " 1 " represents the first time slot.In the second time slot, S keeps quite, and relaying R is to y _rmcarry out amplifying rear forwarding, the stay of two nights receives, and its Received signal strength is:

$y_{\mathrm{dn}}^{\left(2\right)}=\sqrt{\frac{P_R^n}{P_S^m{\left|h_{\mathrm{SR}}^m\right|}^2+{\mathrm{\σ}}_r^2}}{h}_{\mathrm{RD}}^n{y}_{\mathrm{rm}}+z_{\mathrm{dn}}^{\left(2\right)},$

The stay of two nights carries out maximum-ratio combing (MRC) to the signal that two time slots receive, and merged by the signal received, then decoded back sends signal in two time slots.In addition, another work of the stay of two nights is the instantaneous channel state information estimated according to it, searches optimum code word, and its subscript is fed back to transmitting terminal in the Resourse Distribute code book preset.

The present invention realizes by the following technical solutions:

The system combined resource allocation methods of OFDM-AF based on Limited Feedback, comprises the following steps:

Step 1: the design of federated resource allocation strategy code book: each code word in code book is a kind of independent, perfect power division and subcarrier matching scheme, decomposed by integer restriction serialization and Lagrange duality, dexterously former mixed integer programming problem is solved, and construct the center criterion of Lloyd algorithm with this;

Step 2: stay of two nights D is according to all channel matrixes estimating to know, by channel status estimated value is mated with Resourse Distribute code book, in the Resourse Distribute code book of current optimum, traversal search selects optimum code word, and namely optimum power division and subcarrier matching scheme, record this code word subscript;

Step 3: optimum code word subscript is broadcasted by stay of two nights D, information source S and the via node R with same codebook copy receive simultaneously;

The power division of the optimum of step 4: information source S foundation suggested by step 1 and subcarrier matching scheme, carry out the transmission of modulated signal sequences;

Step 5: relaying R to the signal received by step 2 according to the factor carry out amplification process, then forward to stay of two nights D;

Step 6: stay of two nights D is by carrying out maximum-ratio combing (MRC) to the signal received in two time slots, and reduction sends signal, optimum code word subscript corresponding for channel condition information in this transmitting procedure is carried out feedback processing simultaneously.

Optimum code word described in step 2 procurement process is as follows:

In the AF cooperative relay network limited based on system total power, the achievable rate corresponding to subcarrier pair (m, n) is approximately:

$R_{m,n}\≈\frac{1}{2}{\log }_2(1+P_S^m{\mathrm{\γ}}_{\mathrm{SD}}^m+\frac{P_S^m{P}_R^n{\mathrm{\γ}}_{\mathrm{SR}}^m{\mathrm{\γ}}_{\mathrm{RD}}^n}{P_S^m{\mathrm{\γ}}_{\mathrm{SR}}^m+P_R^n{\mathrm{\γ}}_{\mathrm{RD}}^n}),$

Using this achievable rate maximum as target function, system total power is limited as condition, can obtain, and in subcarrier pair (m, n) gross power is time, maximum achievable rate R ^* _{m, n}for:

$R_{m,n}^{*}=\left\{\begin{array}{ccc}\frac{1}{2}{\log }_2(1+\frac{{\mathrm{\&gamma;}}_{\mathrm{SD}}^m\mathrm{\&mu;}({\mathrm{\&gamma;}}_{\mathrm{SR}}^m\mathrm{\&mu;}+{\mathrm{\&gamma;}}_{\mathrm{RD}}^n)+{\mathrm{\&gamma;}}_{\mathrm{SR}}^m{\mathrm{\&gamma;}}_{\mathrm{RD}}^n\mathrm{\&mu;}}{(1+\mathrm{\&mu;})({\mathrm{\&gamma;}}_{\mathrm{SR}}^m\mathrm{\&mu;}+{\mathrm{\&gamma;}}_{\mathrm{RD}}^n)}{P}_{m,n}),& \mathrm{if}& {\mathrm{\&gamma;}}_{\mathrm{SD}}^m<{\mathrm{\&gamma;}}_{\mathrm{RD}}^n,\\ \frac{1}{2}{\log }_2(1+{\mathrm{\&gamma;}}_{\mathrm{SD}}^m{P}_{m,n}),& \mathrm{if}& {\mathrm{\&gamma;}}_{\mathrm{SD}}^m\&GreaterEqual;{\mathrm{\&gamma;}}_{\mathrm{RD}}^n.\end{array}\right.$

If definition equivalent channel gain

${\stackrel{\&OverBar;}{\mathrm{\&gamma;}}}^{m,n}=\left\{\begin{array}{cc}\frac{{\mathrm{\&gamma;}}_{\mathrm{SD}}^m\mathrm{\&mu;}({\mathrm{\&gamma;}}_{\mathrm{SR}}^m\mathrm{\&mu;}+{\mathrm{\&gamma;}}_{\mathrm{RD}}^n)+{\mathrm{\&gamma;}}_{\mathrm{SR}}^m{\mathrm{\&gamma;}}_{\mathrm{RD}}^n\mathrm{\&mu;}}{(1+\mathrm{\&mu;})({\mathrm{\&gamma;}}_{\mathrm{SR}}^m\mathrm{\&mu;}+{\mathrm{\&gamma;}}_{\mathrm{RD}}^n)},& {\mathrm{\&gamma;}}_{\mathrm{SD}}^m<{\mathrm{\&gamma;}}_{\mathrm{RD}}^n,\\ {\mathrm{\&gamma;}}_{\mathrm{SD}}^m,& {\mathrm{\&gamma;}}_{\mathrm{SD}}^m\&GreaterEqual;{\mathrm{\&gamma;}}_{\mathrm{RD}}^n\end{array}\right.$

R _{m, n}can be collectively expressed as form.To integer restrictive condition t _{m, n}{ 0,1} carries out relaxing extremely ∈ afterwards, subcarrier matching attribute t is made _{m, n}become the time domain sharing learning of each subcarrier pair of system, then now former optimization problem can become

$\underset{\{S,t\}}{\max }\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{t}_{m,n}\frac{1}{2}{\log }_2(1+S_{m,n}\frac{{\stackrel{\&OverBar;}{\mathrm{\&gamma;}}}^{m,n}}{t_{m,n}}),$

$s.t.t_{m,n}\&GreaterEqual;0,\&ForAll;m,n,\underset{m=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{S}_{m,n}\&le;P_t,S_{m,n}\&GreaterEqual;0,\&ForAll;m,n,$

$\underset{m=1}{\overset{N}{\mathrm{\&Sigma;}}}{t}_{m,n}=1,\&ForAll;n,\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{t}_{m,n}=1,\&ForAll;m,$

Wherein S _{m, n}=t _{m, n}p _{m, n}the actual power that finger system consumes in subcarrier pair (m, n).The present invention is by restrictive condition and carry out dualization operation, can construct Lagrangian is:

$L(S,t,\mathrm{\&alpha;},\mathrm{\&beta;})=\frac{1}{2}\underset{m=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{t}_{m,n}{\log }_2(1+S_{m,n}\frac{{\stackrel{\&OverBar;}{\mathrm{\&gamma;}}}^{m,n}}{t_{m,n}})+\mathrm{\&alpha;}(P_t-\underset{m=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{S}_{m,n})+\underset{m=1}{\overset{N}{\mathrm{\&Sigma;}}}{\mathrm{\&beta;}}_m(1-\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{t}_{m,n}),$

Wherein α>=0 and β=(β ₁, β ₂..., β _n) ± 0 is dual variable.Now, dual objective function and dual problem thereof are respectively:

$g(\mathrm{\&alpha;},\mathrm{\&beta;})=\underset{\{S,t\}}{\max }L(S,t,\mathrm{\&alpha;},\mathrm{\&beta;}),s.t.\underset{m=1}{\overset{N}{\mathrm{\&Sigma;}}}{t}_{m,n}=1,\&ForAll;n,t_{m,n}\&GreaterEqual;0,\&ForAll;m,n,\underset{m=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{S}_{m,n}\&le;P_t,$

$\begin{array}{cc}\underset{\{\mathrm{\&alpha;},\mathrm{\&beta;}\}}{\min }g(\mathrm{\&alpha;},\mathrm{\&beta;})& s.t.\mathrm{\&alpha;}\&GreaterEqual;0,\mathrm{\&beta;}\&PlusMinus;0.\end{array}$

Solve optimal power allocation vector and optimum subcarrier matching attribute be respectively:

$S_{m,n}^{*}=t_{m,n}{[\frac{1}{2\mathrm{\&alpha;}}-\frac{1}{{\stackrel{\&OverBar;}{\mathrm{\&gamma;}}}^{m,n}}]}^{+},t_{m,n}^{*}=\left\{\begin{array}{cc}1& m=\arg \underset{m=1,...,N}{\max }{T}_{m,n},\\ 0& \mathrm{otherwise}.\end{array}\right.$

For dual problem, dual variable value can be obtained by gradient descent method iteration:

$\left\{\begin{array}{cc}{\mathrm{\&alpha;}}^{(i+1)}={\mathrm{\&alpha;}}^{\left(i\right)}-{\mathrm{\&alpha;}}^{\left(i\right)}(P_t-\underset{m=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{S}_{m,n}^{\left(i\right)}),& \\ {\mathrm{\&beta;}}_m^{(i+1)}={\mathrm{\&beta;}}_m^{\left(i\right)}-b^{\left(i\right)}(1-\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{t}_{m,n}^{\left(i\right)}),& m=1,...,N,\end{array}\right.$

Wherein, i is iterations, a ⁽ⁱ⁾and b ⁽ⁱ⁾for iteration step length.Based on α and β obtained in iteration each time _m, we can upgrade optimal power allocation vector and optimum subcarrier matching attribute, until algorithmic statement, export optimal power allocation vector and optimum subcarrier matching attribute, and construct optimum code word with this.

Operation principle of the present invention:

Based in the relay cooperative system of OFDM modulation, because sub-channel amount of information is various, the restriction of the factors such as the capacity that feedback link is limited and the restriction of code book scale, makes feedback of channel information be difficult to realize, and then the carrying out of the power division limited in real system and subcarrier coupling.The present invention adopts the technology of Limited Feedback, by the design to feedback code book, represents complete Resourse Distribute vector, thus realize the dynamic assignment of subcarrier and power with few feedback bits.The present invention adopts Lloyd algorithm to construct the Resourse Distribute code book needed for feedback.In the design part for center criterion, utilize the time domain sharing characteristic of multicarrier system, integer restriction serialization is carried out to former mixed integer programming problem, and adopts Lagrange duality method to solve the optimization problem after process.By the interactive iteration of center criterion and the most contiguous criterion, the optimal resource allocation vector obtained after convergence is the prototype of code word in optimum code book.

Compared with prior art, contemplated by the invention application scenarios more actual in radio communication, dynamic sub carrier when namely cannot obtain complete channel information at sending node place mates and power division.Mate with existing joint subcarrier and compare with power distribution strategies, only need the feedback of very limit bit number just can make up the performance gain of the system overwhelming majority.

Accompanying drawing explanation

Fig. 1 is the trunk channel system block diagram based on feedback.

Fig. 2 is the iterative process schematic diagram of Lloyd algorithm.

Fig. 3 is Lloyd convergence of algorithm performance.

Fig. 4 is the comparison of distinct methods in given SNR ranges in the end-to-end speed of system.

Fig. 5 is the comparison of method end-to-end speed of system when different number of bits of feedback.

Fig. 6 be method when number of sub carrier wave changes, the comparison of the end-to-end speed of the system that diverse ways can obtain.

In Fig. 4, Fig. 6:

EPA w/o SP represents on the basis without subcarrier coupling and carries out average power allocation;

OPA w/o SP represents on the basis without subcarrier coupling and carries out optimal power allocation;

EPA with SP then represent optimum subcarrier coupling basis on carry out average power allocation.

Embodiment

Below in conjunction with accompanying drawing and simulation example, embodiments of the invention are elaborated: the present embodiment is implemented premised on technical solution of the present invention; give detailed execution mode and concrete operating process, but protection scope of the present invention is not limited to following embodiment.

As the OFDM AF trunk channel in accompanying drawing 1, the signal received is carried out amplification forwarding by relaying.System adopts QPSK modulation system.The channel gain of all sub-carrier channels remains unchanged in the transmitting procedure of complete two time slots, the equal Rayleigh distributed of each sub-carrier channels, and path-loss factor is 3.Noise hypothesis is obeyed gradient descent method iteration step length is the scale of channel status collection is 10 ⁴.In emulation, every prescription case all carries out 10,000 l-G simulation test.Each test is carried out according to following steps:

1: according to maximum system rate criterion design resource feedback code book, its code word is made up of power allocation vector and subcarrier matching attribute.First construct optimization problem, restrictive condition is the integer attribute of system total power limited and subcarrier coupling; Problem is converted into and solves Lagrange duality resolution problem by the integer condition of being mated by serialization subcarrier; The closed solutions of optimal power allocation and optimum subcarrier coupling when the dual problem optimizing this dual objective function and correspondence thereof obtains set channel status.Then initialization Lloyd algorithm parameter, comprises the channel status collection H={h of definition great scale _l, l=1 ..., M}, definition iteration step length and constant ε.Then from midamble code collection T={c (h) that channel status set pair is answered | choose B code word h ∈ H} and form initial codebook and realize the alternating iteration of the most contiguous criterion and center criterion based on this code book, in the distortion factor of algorithm meet time, stop iteration, and export optimum code book.

As shown in Figure 2, codebook design and code word renewal process, be specifically expressed as:

Step 1: a large amount of forward channel matrix h=(h of random generation _sD, h _sR, h _rD) form the sample space H={h_{1} of channel as training sequence, 1=1 ..., M}, wherein, $h_{\mathrm{SD}}=(h_{\mathrm{SD}}^1,...,h_{\mathrm{SD}}^N),h_{\mathrm{SR}}=(h_{\mathrm{SR}}^1,...,h_{\mathrm{SR}}^N),h_{\mathrm{RD}}=(h_{\mathrm{RD}}^1,...,h_{\mathrm{RD}}^N)$ Refer to the channel status of S-D, S-R and R-D in a certain transmission cycle respectively, N is the sub-carrier number of this ofdm system;

Step 2: produce initialized code book at random based on channel matrix sample space, i.e. codeword set wherein j is that iterations now gets j=0, and B is code book scale, depends on system feedback bit number k, and the relationship of the two is k=log ₂b, for code word, wherein refer to that information source S is in m sub-carrier channels and the transmitted power of relaying R in the n-th sub-carrier channels respectively, t _{m, n}{ 0,1} is subcarrier matching attribute to ∈, and when its value is 1, subcarrier m and n mates, otherwise the two does not mate;

Step 3: according to set code book be the sub-channel space that B does not overlap mutually channel matrix spatial division $Q_k^j,k=1,...,B,$ And have

$Q_k^j=\{h=h(h_{\mathrm{SD}},h_{\mathrm{SR}},h_{\mathrm{RD}})|\left(R\left(c_k^j\right|h)\right)\&GreaterEqual;\left(R\left(c_l^j\right|h)\right),\&ForAll;l\&Element;\{\mathrm{1,2},...,B\}\},$

Wherein R (c|h) is defined as and corresponds to based on channel samples space H={h _l, l=1 ..., the end-to-end total speed of system of the arbitrary given channel conditions h in M} and optimum code word c, it can be tried to achieve by following formula:

$R=\underset{m=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}\frac{1}{2}{t}_{m,n}{\log }_2(1+P_S^m{\mathrm{\&gamma;}}_{\mathrm{SD}}^m+\frac{P_S^m{P}_R^n{\mathrm{\&gamma;}}_{\mathrm{SR}}^m{\mathrm{\&gamma;}}_{\mathrm{RD}}^n}{P_S^m{\mathrm{\&gamma;}}_{\mathrm{SR}}^m+P_R^n{\mathrm{\&gamma;}}_{\mathrm{RD}}^n}),$

Wherein, refer to the normalized channel gain on corresponding subcarrier link respectively, and have:

${\mathrm{\&gamma;}}_{\mathrm{SD}}^m={\left|h_{\mathrm{SD}}^m\right|}^2/{\mathrm{\&sigma;}}_d^2,{\mathrm{\&gamma;}}_{\mathrm{SR}}^m={\left|h_{\mathrm{SR}}^m\right|}^2/{\mathrm{\&sigma;}}_r^2$ And ${\mathrm{\&gamma;}}_{\mathrm{RD}}^n={\left|h_{\mathrm{RD}}^n\right|}^2/{\mathrm{\&sigma;}}_d^2;$

Step 4: realize the renewal of code book, corresponding to new code book by more newly arriving to each code word in code book a kth code word be updated to:

$c_k^{j+1}=\arg \underset{c\&Element;T}{\max }{E}_{h\&Element;Q_k}\left(R\left(c\right|h)\right),k=\mathrm{1,2},...,B;$

This step can be realized by following calculating:

$\arg \underset{c\&Element;T}{\max }{E}_{h\&Element;Q_k}\left(R\left(c\right|h)\right)=\arg \underset{c\&Element;T}{\max }{E}_{h\&Element;Q_k}\left(\underset{m=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}\frac{1}{2}{t}_{m,n}{\log }_2(1+P_S^m{\mathrm{\&gamma;}}_{\mathrm{SD}}^m+\frac{P_S^m{P}_R^n{\mathrm{\&gamma;}}_{\mathrm{SR}}^m{\mathrm{\&gamma;}}_{\mathrm{RD}}^n}{P_S^m{\mathrm{\&gamma;}}_{\mathrm{SR}}^m+P_R^n{\mathrm{\&gamma;}}_{\mathrm{RD}}^n})\right);$

Step 5: definition error distance function is distortion function:

And calculate new code book with this overall distortion degree;

Step 6: observe algorithm and whether restrain, and if stop iteration, export optimum code book code word, otherwise jump to step 2 until algorithmic statement, wherein ε is a minimum numeral preset.

2: instantaneous channel state information h=(h is carried out in the stay of two nights _sD, h _sR, h _rD) estimation, and based on this estimated value, in the codebook traversal search, search for and obtain the subscript of the code word with maximum end-to-end speed q is fed back to information source and relaying with binary coded form.

3: information source S according to the code word corresponding to q in power division and optimum subcarrier matching vector carry out signal transmission, via node R and stay of two nights D receives simultaneously.

4: via node R according to the code word corresponding to q in optimum subcarrier matching vector t _{m, n}carry out the subcarrier coupling of double bounce, simultaneously according to power the signal that first time slot receives is amplified, and carries out the Signal transmissions of the second time slot, now only have stay of two nights D to receive.

5: the stay of two nights, by carrying out maximum-ratio combing (MRC) to the signal received in two time slots, is decoded and obtained former transmission signal, then decode.Channel condition information in this transmitting procedure is estimated, and then the optimum code word subscript of search correspondence carries out feedback processing simultaneously.

In the present embodiment, the communication scenes of setting is: information source S, via node R and stay of two nights D distribution on the same line; The range normalization supposing between information source S to stay of two nights D is the distance definition between 1, information source S to via node R is d, then the distance of via node R to stay of two nights D is just 1-d.Above-mentioned all figure are all attained at d=0.4.According to above-mentioned steps, respectively repeatedly carried out 10,000 independent l-G simulation test, the total speed of the system that calculates, draws result as shown in drawings.

As can be seen from accompanying drawing 3, in 4 independent statistics carried out, Lloyd algorithm all just realizes convergence in limited number of times (being less than 6 times), this show the present invention carry algorithm there is certain feasibility.

As can be seen from accompanying drawing 4, the federated resource allocative decision of the present embodiment, when number of bits of feedback k=3, performance is considerably beyond EPA w/o SP, OPA w/o SP, EPA with SP tri-kinds of schemes.This explanation, the solution of the present invention, compared to during without feedback, performance is greatly improved, in addition, accompanying drawing 3 can also find, performance when the total speed of the system obtained during number of bits of feedback k=3 and transmitting terminal have ideal communication channel information is more or less the same, and this illustrates, the solution of the present invention, only need few overhead, just can make up the performance loss of the overwhelming majority.This means that the employing of Limited Feedback technology has certain feasibility and frontier nature.It is excavated further and is developed there is actively far-reaching realistic meaning.

As can be seen from accompanying drawing 5, the federated resource allocative decision of the present embodiment, only needs few bit feedback, just can realize the significantly lifting of performance.Such as in 4 bit feedback situations, when system velocity is 2.5, this Limited Feedback and transmitting terminal have the performance difference that perfect condition information situation only has-0.7dB.In addition, accompanying drawing 4 it can also be seen that, it is more and more less that number of bits of feedback increases the performance boost amplitude brought, and this illustrates, the solution of the present invention, and number of bits of feedback and code book scale do not need setting too large.

As can be seen from accompanying drawing 6, along with the continuous increase of system subcarrier number, the poor performance of the solution of the present invention and EPA w/o SP, OPA w/o SP, EPA with SP tri-kinds of schemes increases gradually, and this larger distribution degree of freedom can be brought to cause by larger number of sub carrier wave.

Although content of the present invention has done detailed introduction by above preferred embodiment, will be appreciated that above-mentioned description should not be considered to limitation of the present invention.After those skilled in the art have read foregoing, for multiple amendment of the present invention and substitute will be all apparent.Therefore, protection scope of the present invention should be limited to the appended claims.

Claims (5)

1. based on the system combined resource allocation methods of OFDM-AF of Limited Feedback, it is characterized in that, described relay system is a kind of single antenna communications system, and this system comprises an information source S, an amplification-forward relay R, a stay of two nights D; Described method step comprises:

Step 1: the design of federated resource allocation strategy code book: each code word in code book is a kind of independent, perfect power division and subcarrier matching scheme, decomposed by integer restriction serialization and Lagrange duality, former mixed integer programming problem is solved, and constructs the center criterion of Lloyd algorithm with this;

Step 2: stay of two nights D is according to all channel matrixes estimating to know, by channel status estimated value is mated with Resourse Distribute code book, in the Resourse Distribute code book of current optimum, traversal search selects optimum code word, and namely optimum power division and subcarrier matching scheme, record this code word subscript;

Step 3: optimum code word subscript is broadcasted by stay of two nights D, information source S and the via node R with same codebook copy receive simultaneously;

The power division of the optimum of step 4: information source S foundation suggested by step 1 and subcarrier matching scheme, carry out the transmission of modulated signal sequences;

Step 5: relaying R carries out amplification process to the signal received by step 2, then forwards to stay of two nights D;

Step 6: stay of two nights D, by carrying out maximum-ratio combing (MRC) to the signal received in two time slots, attempts to reduce former transmission signal, optimum code word subscript corresponding for channel condition information in this transmitting procedure carried out feedback processing simultaneously.

2. the system combined resource allocation methods of the OFDM-AF based on Limited Feedback according to claim 1, it is characterized in that: stay of two nights D is as hub node, channel status is carried out to estimation and and in code book after codeword matching, subscript is fed back to relaying R and information source S, thus determine the Resourse Distribute factor of fl transmission.

3. the system combined resource allocation methods of the OFDM-AF based on Limited Feedback according to claim 1 and 2, is characterized in that, codebook design and code word renewal process, be specifically expressed as:

Step 1: a large amount of forward channel matrix h=(h of random generation _sD, h _sR, h _rD) form the sample space H={h_{l} of channel as training sequence, l=1 ..., M}, wherein, $h_{\mathrm{SD}}=(h_{\mathrm{SD}}^1,...,h_{\mathrm{SD}}^N),h_{\mathrm{SR}}=(h_{\mathrm{SR}}^1,...,h_{\mathrm{SR}}^N),h_{\mathrm{RD}}=(h_{\mathrm{RD}}^1,...,h_{\mathrm{RD}}^N)$ Refer to the channel status of S-D, S-R and R-D in a certain transmission cycle respectively, N is the sub-carrier number of this ofdm system;

Step 2: produce initialized code book at random based on channel matrix sample space, i.e. codeword set wherein j is that iterations now gets j=0, and B is code book scale, depends on system feedback bit number k, and the relationship of the two is k=log ₂b, for code word, wherein refer to that information source S is in m sub-carrier channels and the transmitted power of relaying R in the n-th sub-carrier channels respectively, t _m,n{ 0,1} is subcarrier matching attribute to ∈, and when its value is 1, subcarrier m and n mates, otherwise the two does not mate;

Step 3: according to set code book be the sub-channel space that B does not overlap mutually channel matrix spatial division

k=1 ..., B, and have

$Q_k^j=\{h=h(h_{\mathrm{SD}},h_{\mathrm{SR}},h_{\mathrm{RD}})|\left(R\left(c_k^j\right|h)\right)\&GreaterEqual;\left(R\left(c_l^j\right|h)\right),\&ForAll;l\&Element;\{\mathrm{1,2},...,B\}\},$

Wherein R (c|h) is defined as and corresponds to based on channel samples space H={h_{l}, l=1 ..., the end-to-end total speed of system of the arbitrary given channel conditions h in M} and optimum code word c, it is tried to achieve by following formula:

$R=\underset{m=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}\frac{1}{2}{t}_{m,n}{\log }_2(1+P_S^m{\mathrm{\&gamma;}}_{\mathrm{SD}}^m+\frac{P_S^m{P}_R^n{\mathrm{\&gamma;}}_{\mathrm{SR}}^m{\mathrm{\&gamma;}}_{\mathrm{RD}}^n}{P_S^m{\mathrm{\&gamma;}}_{\mathrm{SR}}^m+P_R^n{\mathrm{\&gamma;}}_{\mathrm{RD}}^n}),$

Wherein, refer to the normalized channel gain on corresponding subcarrier link respectively, and have:

${\mathrm{\&gamma;}}_{\mathrm{SD}}^m={\left|h_{\mathrm{SD}}^m\right|}^2/{\mathrm{\&sigma;}}_d^2,{\mathrm{\&gamma;}}_{\mathrm{SR}}^m={\left|h_{\mathrm{SR}}^m\right|}^2/{\mathrm{\&sigma;}}_r^2$ And ${\mathrm{\&gamma;}}_{\mathrm{RD}}^n={\left|h_{\mathrm{RD}}^n\right|}^2/{\mathrm{\&sigma;}}_d^2;$

Step 4: realize the renewal of code book, corresponding to new code book by more newly arriving to each code word in code book a kth code word be updated to:

$c_k^{j+1}=\arg \underset{c\&Element;T}{\max }{E}_{h\&Element;Q_k}\left(R\left(c\right|h)\right),k=1,2,...,B;$

This step is realized by following calculating:

$\arg \underset{c\&Element;T}{\max }{E}_{h\&Element;Q_k}\left(R\left(c\right|h)\right)=\arg \underset{c\&Element;T}{\max }{E}_{h\&Element;Q_k}\left(\underset{m=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{t}_{m,n}\frac{1}{2}{\log }_2(1+P_S^m{\mathrm{\&gamma;}}_{\mathrm{SD}}^m+\frac{P_S^m{P}_R^n{\mathrm{\&gamma;}}_{\mathrm{SR}}^m{\mathrm{\&gamma;}}_{\mathrm{RD}}^n}{P_S^m{\mathrm{\&gamma;}}_{\mathrm{SR}}^m+P_R^n{\mathrm{\&gamma;}}_{\mathrm{RD}}^n})\right);$

Step 5: definition error distance function is distortion function:

And calculate new code book with this overall distortion degree;

Step 6: observe algorithm and whether restrain, and if stop iteration, export optimum code book code word, otherwise jump to step 2 until algorithmic statement, wherein ε is a minimum numeral preset.

4. as claimed in claim 3 based on the system combined resource allocation methods of OFDM-AF of Limited Feedback, it is characterized in that, the renewal of code word is embodied in optimizes following mixed integer programming problem:

$\underset{\{P,t\}}{\max }\underset{m=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}\frac{1}{2}{t}_{m,n}{\log }_2(1+P_S^m{\mathrm{\&gamma;}}_{\mathrm{SD}}^m+\frac{P_S^m{P}_R^n{\mathrm{\&gamma;}}_{\mathrm{SR}}^m{\mathrm{\&gamma;}}_{\mathrm{RD}}^n}{P_S^m{\mathrm{\&gamma;}}_{\mathrm{SR}}^m+P_R^n{\mathrm{\&gamma;}}_{\mathrm{RD}}^n}),$

$s.t.\underset{m=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{t}_{m,n}{P}_{m,n}\&le;P_t,P_{m,n}\&GreaterEqual;0,$

$\underset{m=1}{\overset{N}{\mathrm{\&Sigma;}}}{t}_{m,n}=1,\&ForAll;n,\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{t}_{m,n}=1,\&ForAll;m,$

$t_{m,n}\&Element;\{0,1\},\&ForAll;m,n,$

And obtain optimal solution by integer restriction serialization and dualization method.

5., as claimed in claim 4 based on the system combined resource allocation methods of OFDM-AF of Limited Feedback, it is characterized in that, above-mentioned mixed integer programming problem is become optimization dual objective function by dualization method:

$g(\mathrm{\&alpha;},\mathrm{\&beta;})=\underset{\{P,t\}}{\max }L(P,t,\mathrm{\&alpha;},\mathrm{\&beta;}),$

And dual problem:

Wherein α, β are dual variable, and LagrangianL (P, t, α, β) is configured to:

$\begin{array}{c}L(P,t,\mathrm{\&alpha;},\mathrm{\&beta;})=\frac{1}{2}\underset{m=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{t}_{m,n}{\log }_2(1+P_S^m{\mathrm{\&gamma;}}_{\mathrm{SD}}^m+\frac{P_S^m{P}_R^n{\mathrm{\&gamma;}}_{\mathrm{SR}}^m{\mathrm{\&gamma;}}_{\mathrm{RD}}^n}{P_S^m{\mathrm{\&gamma;}}_{\mathrm{SR}}^m+P_R^n{\mathrm{\&gamma;}}_{\mathrm{RD}}^n})\\ +\mathrm{\&alpha;}(P_t-\underset{m=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{P}_{m,n})+\underset{m=1}{\overset{N}{\mathrm{\&Sigma;}}}{\mathrm{\&beta;}}_m(1-\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{t}_{m,n})\end{array}.$