CN103236908B - A kind of network coding method in conjunction with orthogonal processing - Google Patents

Abstract

The invention discloses a kind of network coding method in conjunction with orthogonal processing, belong to multi-user's multi-relay cooperation communication technical field.The method comprises the following steps: step one: the data of transmission are carried out lower frequency quadrature process by originating mobile subscriber, make the user profile after process meet pairwise orthogonal；Step 2: be broadcast to via node after the user profile after orthogonal processing being modulated；Step 3: the via node user profile to receiving is sent to receiving terminal after carrying out network code；Step 4: receiving terminal goes out user profile by the coding packets received.A kind of network coding method in conjunction with orthogonal processing of the present invention has well used this feature of pairwise orthogonal between the user profile after processing, make receiving terminal just can directly decode out user profile after receiving a coding information bag, truly embody the advantage of network code, both receiving terminal decoding real-time had been met, reduce system break probability, be effectively improved again systematic entirety energy.

Description

A kind of network coding method in conjunction with orthogonal processing

Technical field

The invention belongs to multi-user's multi-relay cooperation communication technical field, relate to a kind of network coding method in conjunction with orthogonal processing.

Background technology

The cardinal principle of network code is the ability utilizing via node to process information, is transmitted to next-hop node after the multiple information received are carried out merging treatment linearly or nonlinearly, improves the network throughput of system.Network code is propose in cable network at first, along with the development of wireless communication technology is applied in the wireless network gradually, and the broadcast characteristic of wireless network, further promote the development of network coding technique.

At present, the network coding technique used in radio communication mostly is exclusive-OR network coding, physical-layer network coding, finite field network code and complex field network code etc..The system of most study is that two users cooperate/junction network.In order to make network code research in a wireless communication system have more the suitability, multi-user Cooperation/junction network becomes the further research field using network code.

For multi-user Cooperation/junction network, the coding bag that employing binary system exclusive-OR network coding obtains isReceiving terminal needs to receive enough originating mobile subscriber information bag that direct transfers just can be successfully decoded out user profile, without direct transfer link and by relay forwarding system in be generally difficult to and meet being correctly decoded of receiving terminal；Finite field network code makes full use of relay forwarding characteristic, network code (must being fulfilled for via node number N >=originating mobile subscriber number M here) is carried out for information to receiving of the code coefficient of multiple relay selection linear independences, the coded system of single via node is: choosing the code coefficient originating mobile subscriber information to receiving from finite field (Gauss territory) and carry out network code, the coding bag obtained is γ_{1, j}x₁+γ_2,jx₂+…+γ_n,jx_n+ ..., when receiving terminal receives enough coding bags, the matrix that just can be constituted by the code coefficient of multiple linear independences, decode user profile, therefore, finite field network code application advantage in multi-user system shows gradually.The diversity network code proposed in document Multiple-usercooperativecommunicationsbasedonlinearnetwo rkcoding；The network code based on ultimate range distribution code proposed in Designofnetworkcodesformultiple-usermultiplerelaywireles snetworks；The collaborative network based on cluster proposed in Cluster-basedcooperativecommunicationwithnetworkcodingin wirelessnetworks encodes, all utilize the linear independence between the code coefficient of coding bag, by solving the matrix that multiple coding bag is constituted, decode user profile.

But, adopt the system of finite field network code, the coding information bag that receiving terminal can not pass through to receive directly decodes out user profile, and needs abundant packet just can decode user profile, and real-time and the system break probability of decoding are proposed new requirement by this.

Summary of the invention

In view of this, it is an object of the invention to provide a kind of network coding method in conjunction with orthogonal processing, quadrature processing techniques is applied in network service by the method, has both met receiving terminal decoding real-time, reduce system break probability, be effectively improved again systematic entirety energy.

For reaching above-mentioned purpose, the present invention provides following technical scheme:

A kind of network coding method in conjunction with orthogonal processing, comprises the following steps: step one: the data of transmission are carried out lower frequency quadrature process by originating mobile subscriber, make the user profile after process meet pairwise orthogonal；Step 2: be broadcast to via node after the user profile after orthogonal processing being modulated；Step 3: the via node user profile to receiving is sent to receiving terminal after carrying out network code；Step 4: receiving terminal goes out user profile by the coding packets received.

Further, in step one, the element multiplication in the set E that originating mobile subscriber data are constituted with orthogonal low frequency signal, make the originating mobile subscriber information after orthogonal processing meet pairwise orthogonal, wherein: E=(cos2 π f₁t,cos2πf₂t,…,cos2πf_Mt,…)。

Further, in step one, the frequency (f of set E medium and low frequency orthogonal signalling₁,f₂,…,f_M...) and it is far smaller than modulation carrier wave cos ω_cThe mid frequency ω of t_c, when meeting receiving terminal demodulation, orthogonal processing signal will not be produced impact.

Further, in step 2, the information bag after orthogonal processing is all adopted BPSK modulation system by each source.

Further, in step 3, the network code mode that via node adopts is stacking network coded system.

Further, in step 3, the network code mode that via node adopts is finite field network code mode.

Further, when choosing code coefficient, need to ensure to meet linear independence between the code coefficient vector of coding bag.

The beneficial effects of the present invention is: a kind of network coding method in conjunction with orthogonal processing of the present invention has well used this feature of pairwise orthogonal between the user profile after processing, make receiving terminal just can directly decode out user profile after receiving a coding information bag, truly embody the advantage of network code, both receiving terminal decoding real-time had been met, reduce system break probability, be effectively improved again systematic entirety energy.

Accompanying drawing explanation

In order to make the purpose of the present invention, technical scheme and beneficial effect clearly, the present invention provides drawings described below to illustrate:

Fig. 1 is the system framework schematic diagram of institute of the present invention application network；

Fig. 2 is the schematic diagram that the source of this method processes specific coding flow process；

Fig. 3 is that receiving terminal directly decodes schematic diagram；

Fig. 4 is the decoding schematic diagram that receiving terminal adopts dematrix mode；

Fig. 5 is the schematic flow sheet of the method for the invention.

Detailed description of the invention

The multi-user multi-hop hierarchical network that the present invention is transmitted with a kind of applicable high-speed data service is for system model, for meeting receiving terminal decoding real-time and the reliability of signal transmission, it is proposed that a kind of network coding method in conjunction with orthogonal processing.Here illustrating for double bounce multi-user Cooperation network, system model is as shown in Figure 1.The transmitting procedure of information bag is made up of source-via node, via node-receiving terminal double bounce.

The main thought of the present invention is as shown in Figure 2.Before the modulation of originating mobile subscriber data sends, the data message first each originating mobile subscriber produced carries out orthogonal processing, and namely so-called orthogonal processing is from one group of orthogonal set E=(cos2 π f being made up of quadrature carrier₁t,cos2πf₂t,…,cos2πf_MT ...) in select element be multiplied with originating mobile subscriber data, make the user data after process meet pairwise orthogonal.Frequency (the f of each carrier wave element in set E₁,f₂,…,f_M...) and it is far smaller than modulation carrier wave cos ω_cThe mid frequency ω of t_c, adopt cos ω_cSignal after t modulation can move high frequency, and gather the element in E and after signal multiplication, signal only carry out small moving, and orthogonal processing signal will not be produced impact when making receiving terminal demodulate.

The orthogonal processing thought mathematical form of source is expressed as follows:

At 0≤t≤T_bInterior originating mobile subscriber S_i, i=1,2 ..., M sends 1 pulse data, the element cos2 π f in orthogonal set E_iLow frequency signal x after t process_iT () is represented by following form:

$x_i\left(t\right)=\left\{\begin{array}{c}\cos 2{\mathrm{\πf}}_{i}t,1_{\′}^{\′}\\ -\cos 2\mathrm{\π}{f}_{i}t,0_{\′}^{\′}\end{array}\right.---\left(1\right)$

Signal after orthogonal processing is carried out 2PSK modulation, obtains at 0≤t≤T_bIn, the signal expression after modulation:

$X_i\left(t\right)=\left\{\begin{array}{c}\cos {\mathrm{\ω}}_{c}t\·\cos 2\mathrm{\π}{f}_{i}t,1_{\′}^{\′}\\ -{\cos \mathrm{\ω}}_{c}t\·\cos 2\mathrm{\π}{f}_{i}t,0_{\′}^{\′}\end{array}\right.---\left(2\right)$

Wherein, ω_c> > f_i, i=1,2 ..., M.

When carrying out mathematical formulae modeling, lower frequency quadrature processes and symbol-modulated is not conceptually distinguished by modulation treatment completely, has been added in the concept (symbol has been formulated to+1 ,-1) of symbol-modulated in formula (1).

M originating mobile subscriber S_iAdopt time division multiple access way by information X_i(t), i=1,2 ..., M is to via node.Assume that the channel gain coefficient between node is h_i,j, suffered noise is average is 0, and variance is N₀White Gaussian noise, then the source information that via node receives can be expressed from the next:

W_i,j(t)=h_i,jX_i(t)+n_i,j(3)

Wherein, subscript i=1,2 ..., M represents M source end node respectively, j=1, and 2 ..., N represents the N number of via node listening to signal respectively.

Via node recovers modulation signal X after the source information received is detected_iT (), is sent to receiving terminal after then the user profile being properly received being carried out network code.If via node adopts the stacking network coded system information to receiving to carry out network code, then the information after repeated nodes encoding is:

$C_j=X_1\left(t\right)+X_2\left(t\right)+\·\·\·+X_M\left(t\right)=\underset{i=1}{\overset{M}{\mathrm{\Σ}}}{X}_i---\left(4\right)$

If via node adopts the finite field network code mode information to receiving to carry out network code, then the information after repeated nodes encoding is:

$\begin{array}{c}{C}_j=X_1\left(t\right)\·{\mathrm{\γ}}_{1,j}+X_2\left(t\right)\·{\mathrm{\γ}}_{2,j}+\·\·\·+X_M\left(t\right)\·{\mathrm{\γ}}_{M,j}\\ =\underset{i=1}{\overset{M}{\mathrm{\Σ}}}{X}_i\·{\mathrm{\γ}}_{i,j}\end{array}---\left(5\right)$

Wherein, γ_i,jFor the finite field code coefficient that originating mobile subscriber information is corresponding, C_jFor coding information bag.Stacking network coding can regard γ as_i,jEntirely take the finite field network code of 1.

After receiving terminal receives coding information bag, can adopt and gather the mode that directly decodes of corresponding orthogonal processing element multiplication in E and decode user data.If the finite field network code mode that via node adopts, then receiving terminal is except adopting the mode of directly decoding to decode user data, also can adopt the indirect decoding process decoding user data by solving the matrix that multiple information bag is constituted of conventional finite territory network code.Two kinds of decoding processes are as shown in Figure 3, Figure 4.

The main thought that receiving terminal directly decodes after receiving coding information bag is with reference to shown in Fig. 3, orthogonal processing has been carried out owing to user is sent data in source by the given network coding method in conjunction with orthogonal processing, make the user profile pairwise orthogonal after process, therefore after the coding information bag that receiving terminal demodulation receives, can by the inverse orthogonal processing mode that corresponding orthogonal processing element is multiplied being obtained the user profile of needs with the information after demodulation.

Concretely comprise the following steps: the coding bag C that receiving terminal will receive_jAfter carrying out equilibrium, demodulation obtains:

$\begin{array}{c}{c}_j=\frac{1}{2}\mathrm{LPF}(C_j\·\cos {\mathrm{\ω}}_{c}t)\\ ={\mathrm{\γ}}_{1,j}\·x_1\left(t\right)+{\mathrm{\γ}}_{2,j}\·x_2\left(t\right)+\·\·\·+{\mathrm{\γ}}_{M,j}\·x_M\left(t\right)\end{array}---\left(6\right)$

Wherein, x₁(t),x₂(t),…,x_MT () is through cos2 π f₁t,cos2πf₂t,…,cos2πf_MSignal after the process of t lower frequency quadrature, they pairwise orthogonals.

Due to orthogonality:

$\left\{\begin{array}{c}\cos 2\mathrm{\π}{f}_{i}t\·\cos 2\mathrm{\π}{f}_{j}t(i=j)=\frac{1}{2}+\mathrm{\θ}\\ \cos 2\mathrm{\π}{f}_{i}t\·\cos 2\mathrm{\π}{f}_{j}t(i\≠j)=\mathrm{\θ}\end{array}\right.---\left(7\right)$

Therefore, receiving terminal can decode corresponding user information by following two formulas:

$\begin{array}{c}{\hat{X}}_i=c_j\·\cos 2\mathrm{\π}{f}_{i}t\\ =(x_1\left(t\right)+x_2\left(t\right)+\·\·\·+x_M\left(t\right))\·\cos 2\mathrm{\π}{f}_{i}t\\ ={\mathrm{\γ}}_{i,j}\·X_i\·{\left|\cos 2\mathrm{\π}{f}_{i}t\right|}^2+\mathrm{\θ}\end{array}---\left(8\right)$

$X_i=\frac{1}{2\·{\mathrm{\γ}}_{i,j}}\mathrm{LPF}\left({\hat{X}}_i\right)---\left(9\right)$

Wherein,Represent the frequency signal intersection higher than direct current signal, LPF() represent that signal passes through low pass filter.

The main thought of decoding is with reference to shown in Fig. 4 indirectly, and it adopts the decoding process of conventional finite territory network code dematrix, decodes user profile.Comprise the following steps that.

After N number of via node has forwarded coding bag, the relation between N number of coding information bag and source information bag after finite field network code can be represented by the formula:

$\left(\begin{array}{c}{c}_1\\ c_2\\ \·\\ \·\\ \·\\ c_N\end{array}\right)={\left(\begin{array}{cccc}{\mathrm{\γ}}_{\mathrm{1,1}}& {\mathrm{\γ}}_{\mathrm{2,1}}& \·\·\·& {\mathrm{\γ}}_{M,1}\\ {\mathrm{\γ}}_{\mathrm{1,2}}& {\mathrm{\γ}}_{\mathrm{2,2}}& \·\·\·& {\mathrm{\γ}}_{M,2}\\ & & \·& \\ & & \·& \\ & & \·& \\ {\mathrm{\γ}}_{1,N}& {\mathrm{\γ}}_{2,N}& \·\·\·& {\mathrm{\γ}}_{M,N}\end{array}\right)}_{N\×M}\·\left(\begin{array}{c}{x}_1\\ x_2\\ \·\\ \·\\ \·\\ x_M\end{array}\right)---\left(10\right)$

Above formula can be further represented as:

Y=K x (11)

Wherein, Y is the coding information bag Y=(c after the demodulation that receiving terminal receives₁,c₂,…,c_N)；(x₁,x₂,…,x_M)^TFor the pairwise orthogonal information after demodulation.K is coefficient matrix:

$K=={\left(\begin{array}{cccc}{\mathrm{\γ}}_{\mathrm{1,1}}& {\mathrm{\γ}}_{\mathrm{2,1}}& \·\·\·& {\mathrm{\γ}}_{M,1}\\ {\mathrm{\γ}}_{\mathrm{1,2}}& {\mathrm{\γ}}_{\mathrm{2,2}}& \·\·\·& {\mathrm{\γ}}_{M,2}\\ & & \·& \\ & & \·& \\ & & \·& \\ {\mathrm{\γ}}_{1,N}& {\mathrm{\γ}}_{2,N}& \·\·\·& {\mathrm{\γ}}_{M,N}\end{array}\right)}_{N\×M}---\left(12\right)$

Wherein, γ_i,jRepresent the code coefficient selected from finite field.User's number in the row representative system of matrix K, row represents the information bag number that receiving terminal receives.

Then, receiving terminal passes through equation (9), decodes user profile in the way of dematrix.Here, dematrix working mechanism can be described as, if a certain M rank submatrix K of transfer matrix K^MFull rank, receiving terminal just can pass through to solve augmented matrix (K^M|Y^M) form decode source information, Y^MFor K^MCorresponding Receiving coded information bag.

Adopt below and solve augmented matrix (K^M|Y^M) inverse matrix mode decode information x:

X=(K^M)^-1·Y^M(13)

X=(the x decoded₁(t),x₂(t),…,x_M(t)) process for lower frequency quadrature after information, then obtain the user profile needed after the x decoded is carried out lower frequency quadrature inversely processing:

$X_i=\frac{1}{2}\mathrm{LPF}(x_i\left(t\right)\·\cos 2\mathrm{\π}{f}_{i}t)=\frac{1}{2}\mathrm{LPF}(\±{\left|\cos 2\mathrm{\π}{f}_{i}t\right|}^2)---\left(14\right)$

If via node adopts stacking network coded system that the information bag received is carried out network code, then the user profile that receiving terminal obtains by directly decoding mode is the final user profile needed；If via node adopts finite field network code mode that the information bag received is carried out network code, then receiving terminal not only can adopt the mode of directly decoding to obtain user profile, indirect decoding process also can be adopted to obtain user profile, therefore, via node adopts the system of finite field network code mode can pass through to compare multiple originating mobile subscriber information that receiving terminal decodes, and obtains more excellent end user information after these information are processed.

What finally illustrate is, preferred embodiment above is only in order to illustrate technical scheme and unrestricted, although the present invention being described in detail by above preferred embodiment, but skilled artisan would appreciate that, in the form and details it can be made various change, without departing from claims of the present invention limited range.

Claims (3)

1. the network coding method in conjunction with orthogonal processing, it is characterised in that: comprise the following steps:

Step one: the data of transmission are carried out lower frequency quadrature process by originating mobile subscriber, make the originating mobile subscriber information after process meet pairwise orthogonal；

Step 2: be broadcast to via node after the originating mobile subscriber information after lower frequency quadrature processes being modulated；

Step 3: via node is sent to receiving terminal after the originating mobile subscriber information received is carried out network code, the network code mode that via node adopts is finite field network code mode；

Step 4: receiving terminal goes out user profile by the coding packets received, wherein, receiving terminal adopts to directly decode and is decoded with decoding two ways indirectly；

In step one, the set that originating mobile subscriber data are constituted with lower frequency quadrature signal:

E=(cos2 π f₁t,cos2πf₂t,…,cos2πf_MT) element multiplication in, makes the originating mobile subscriber information after lower frequency quadrature processes meet pairwise orthogonal, and wherein, originating mobile subscriber is expressed as S_i, i=1,2 ... M, t express time parameter；

In step one, the frequency (f of set E medium and low frequency orthogonal signalling₁,f₂,…,f_M) it is far smaller than modulation carrier wave cos ω_cThe mid frequency ω of t_c, namely adopt cos ω_cOriginating mobile subscriber data after t modulation can move high frequency, and gather and only originating mobile subscriber data are carried out after the element in E is multiplied with originating mobile subscriber data small moving, the originating mobile subscriber information after lower frequency quadrature processes will not be produced impact when making receiving terminal demodulate.

2. the network coding method in conjunction with orthogonal processing according to claim 1, it is characterised in that: in step 2, the originating mobile subscriber information after lower frequency quadrature processes all is adopted BPSK modulation system by each originating mobile subscriber.

3. the network coding method in conjunction with orthogonal processing according to claim 1, it is characterised in that: when choosing code coefficient, need to ensure to meet linear independence between the code coefficient vector of coding information bag.