CN103248458A - Physical layer network coding system and method based on FQPSK modulation - Google Patents

Abstract

The invention provides a physical layer network coding system and method based on FQPSK (Feher patented Quadrature Phase Shift Keying) modulation. The method is characterized in that a transmitting terminal unit comprises the following steps: A, respectively emitting raw information xA and xB by two signal sources; B, respectively modulating the two pieces of raw information xA and xB after completion of respective modulation to a high-frequency carrier to be changed into emission signals zA and zB; and C, expressing the mixed signals received by a relay module as YR(t)={zA(t)+n(t)}+{zB(t)+n'(t)}, where YR(t) represents the received mixed waveform signals. The method has the benefits that the FQPSK modulation is adopted to perform constant envelope protection for the physical layer network encoded signals, which successfully solves the problem of detection and classification for stacked signals at the relay; and a waveform cluster classification criteria replaces a constellation classification criteria so as to avoid the defect that the FQPSK modulation constellation is ruleless.

Description

Physical-layer network coding system and method based on the FQPSK modulation

Technical field

The present invention relates to the physical layer network coding technique under the nonlinear channel, relate in particular to the physical-layer network coding system and method based on the FQPSK modulation.

Background technology

Physical-layer network coding:

Network coding technique is considered to an important breakthrough in the communications field in this century, it has become the effective ways that improve network throughput, robustness, load balancing and fail safe etc., boring in the finite element network environment is all to have obtained important achievement in theory or practical application, is subjected to the favor of domestic and international academia.Yet in the wireless cooperation communication network, interference between signals has hindered the utilization of network code in multi-hop wireless networks such as wireless Mesh netword, sensor network and Ad Hoc network.Up to 2006, the proposition of physical-layer network coding concept, it was mapped to galois field (GF(2) with the stack of radio magnetic wave effectively) on the data bit flow computing, make and disturb a part that becomes algorithm operating in the network code.This has not only solved the interference problem between signal, but also utilizes this interference to promote the throughput of network, has reduced time slot, has opened new era of Wireless Ad Hoc network.

Physical-layer network coding has started research boom at home and abroad, at present, physical layer network coding technique has three classes: (the Physical Network Coding over Finite Field of the physical-layer network coding on the finite field, PNCF), analog network coding (Analog Network Coding, ANC), the complex field network code (Complex Field Network Coding, CFNC).Most studies all is devoted to PNCF, and wherein achievement is the most outstanding is the optimal constellation mapping of the two-way relaying denoising system that proposes of Toshiaki, has adopted the scramble network coding to go set of signals under the dividing frequency Selective Fading Channel.Guaranteed the error performance of system with the sacrifice bandwidth efficiency.

At present, relaying sorting criterion based on physical-layer network coding all is aimed at the clear and definite modulation system of phase constellation point, as: BPSK, QPSK, MPSK, mainly be to divide classification according to the position of phase point, but the simple modulation of this class can't be satisfied the requirement of satellite channel transmission at all, for nonlinear channel, time varying channel or big fading channel, need select special efficient modulation techniques for use.Yet the constellation point that some efficient modulation techniques are arranged is uneven distribution, as: the FQPSK modulation, its constellation point is scattered being distributed on the unit circle, in this case, the relaying sorting criterion of existing physical-layer network coding is no longer suitable, needs to seek new sorting criterion.

The accurate permanent envelope modulation technology of FQPSK:

FQPSK is a kind of mode of permanent envelope modulation, and it is the modulation system that a kind of frequency spectrum and power-efficient utilize, and belongs to offset quadrature phase-shift-keying (IJF_OQPSK) family of no intersymbol interference and shake.IJF_OQPSK introduces in order to obtain higher power and spectrum efficiency in satellite communication at first, so it is narrow that FQPSK has further strengthened at frequency domain frequency spectrum main lobe, the secondary lobe fast characteristics of roll-offing, therefore can apply to the communication system of various band resource anxieties, particularly at particularly active of domain of telemetry.

The modulation principle more complicated of FQPSK modulation system, it is at first with the I of offset quadraphase shift keying system (OQPSK), the rectangle video signal pulse waveform that Q goes up mutually, encode by IJF, be transformed into raised cosine waveform, the time interval that makes the waveform zero passage is the integral multiple of I, Q phase code-element period, successful removal phase jitter.And then the road that I, Q are exported mutually with two symbols of two symbols of I phase signals and Q phase more every half symbols carry out the following computing that intersects cross-correlation at interval:

(1) when the I phase signals equals zero, the Q phase signals is got the amplitude peak value of IJF;

(2) when I phase signals amplitude is not equal to zero.Q phase signals maximum decays to the A value $(1/\sqrt{2}\≤A\≤1);$

(3) when the Q phase signals was zero, the I phase signals was got the amplitude peak value of IJF;

(4) when the Q phase signals was not equal to zero, the maximum of I phase signals decayed to the A value.

It is the way of piecing together permanent envelope that this crosscorrelation comes down to a kind of people, and the pressure of radiofrequency signal envelope amplitude is constant, but does not accomplish complete permanent envelope, so the permanent envelope modulation that is referred to as to be as the criterion.

The FQPSK modulation technique is applied to the problem that physical-layer network coding runs into:

In the process of survey of deep space, satellite communication plays a part crucial, the normal operation of only guaranteed satellite communication system just may make the survey of deep space task succeed, and because satellite communication channel has fading characteristic, the operating frequency height, available band is wide, interrupt the chain Louis, on, characteristics such as down link is asymmetric, in order to effectively utilize the power of detector, send signal power amplifier and adopt the high power nonlinear amplifier usually, and this nonlinear amplifier has width of cloth phase (AM/PM) effect, just when the changes in amplitude of input signal, the phase place of corresponding output signal also changes, thereby caused the distortion of signal, causing the deep space communication channel is a kind of typical band limit and non-linear variable-parameter channel.On the other hand, deep space communication has characteristics such as distance, time delay are big, and barrier cover the shadow effect that causes, can cause that transmission rate is low, error rate height etc. is intrinsic determines.Therefore, it is necessary that the relaying collaboration communication applies in the deep space communication, and then can consider that just physical-layer network coding is incorporated in the deep space collaboration communication, can increase throughput of system like this, saves time slot, reduces packet loss.

By the characteristics of above satellite communication as can be known, the BPSK that in the past adopted or QPSK modulating system exist following problem if be applied in the deep space collaboration communication.The first, existing physical-layer network coding modulation technique also is not suitable for the channel characteristic of deep space communication.From analyzing as can be known, we need adopt constant or accurate constant continuous phase modulation technique, and have higher frequency spectrum and power validity.The second, existing relaying sorting criterion all is based on phase place classifies, and for the fuzzy modulation of phase point, as the FQPSK modulation, the sorting criterion of relaying is no longer suitable, needs to seek a kind of new sorting criterion.The phase place of FQPSK is irregular being distributed on the unit circle, and after the stack of relaying two paths of signals, the planisphere after the whole stack is unordered in a jumble, can't adopt existing constellation sorting criterion to go it is classified.

Summary of the invention

In order to solve the problems of the prior art, the invention provides a kind of physical-layer network coding method based on the FQPSK modulation.

The invention provides a kind of physical-layer network coding method based on the FQPSK modulation, the transmitting terminal unit comprises the execution following steps:

A. two signal sources are launched raw information x respectively _AAnd x _B

B. with two raw information x _AAnd x _BBe modulated to after the modulation respectively and become the z that transmits above the high frequency carrier _AAnd z _B

C. trunk module receives mixed signal indication and is: Y _R(t)=[z _A(t)+n (t)]+[z _B(t)+n'(t)], Y _R(t) the hybrid waveform signal that receives of expression.

As a further improvement on the present invention, in described step C, adopt the Waveform Matching technology for detection to go out the hybrid waveform Y of stack _R(t), according to the grid output of Waveform Matching all are formed Y _R(t) waveform signal is divided into two big classifications, and respectively these two classifications is mapped to network code subsymbol x _r∈ { 0,1}.

As a further improvement on the present invention, also comprise step:

D. the trunk module signal x that will newly form _rBe modulated into constant envelope signal y again _r

As a further improvement on the present invention, in described step C, the baseband signal of FQPSK is formed based on 16 special waveforms, and the ability of each small form is different, thereby utilizes the relation that receives between signal and the transmitted signal energy to set sorting criterion.

As a further improvement on the present invention, in described step B, two raw information x _AAnd x _BBecome the z that transmits above the high frequency carrier through being modulated to after LDPC coding module and the FQPSK module successively respectively _AAnd z _B

As a further improvement on the present invention, also comprise receiving terminal unit, in receiving the unit, comprise the execution following steps: at first demodulate the new network signal x that forms of relaying by the MAP algorithm _r, unite then and separate the mapping demodulation, carry out the hard bit reversal decoding of LDPC at last by the LDPC decoder.

The present invention also provides a kind of physical-layer network coding system based on the FQPSK modulation, comprise the transmitting terminal unit, described transmitting terminal unit comprises first signal source and the LDPC coding module and the FQPSK module that link to each other successively with described first signal source, and described first signal source is used for emission raw information x _AAnd become the z that transmits above the high frequency carrier through being modulated to after the modulation of a described LDPC coding module and a FQPSK module _ADescribed transmitting terminal unit also comprises secondary signal source and the 2nd LDPC coding module and the 2nd FQPSK module that link to each other successively with described secondary signal source, and described secondary signal source is used for emission raw information x _BAnd become the z that transmits above the high frequency carrier through being modulated to after the modulation of described the 2nd LDPC coding module and the 2nd FQPSK module _BDescribed transmitting terminal unit also comprises trunk module, and described trunk module is used for receiving z _AAnd z _BMixed signal indication is: Y _R(t)=[z _A(t)+n (t)]+[z _B(t)+n'(t)], Y _R(t) the hybrid waveform signal that receives of expression.

As a further improvement on the present invention, described trunk module comprises:

Detection module: be used for adopting the Waveform Matching technology for detection to go out the hybrid waveform Y of stack _R(t);

Sort module: described sort module links to each other with described detection module, and described sort module is used for according to the grid output of Waveform Matching all being formed Y _R(t) waveform signal is divided into two big classifications, and respectively these two classifications is mapped to network code subsymbol x _r∈ { 0,1};

The 3rd FQPSK module: for the signal x that will newly form _rBe modulated into constant envelope signal y again _r

As a further improvement on the present invention, this physical-layer network coding system also comprises receiving terminal unit, described receiving terminal unit comprises the MAP algoritic module, unites and separate mapping demodulation module and LDPC decoder, described MAP algoritic module output links to each other with the described solution mapping demodulation module input of uniting, and described MAP algoritic module demodulates the new network signal x that forms of relaying by the MAP algorithm _r, the described solution mapping demodulation module output of uniting links to each other with described LDPC decoder input, and described LDPC decoder carries out the hard bit reversal decoding of LDPC.

The invention has the beneficial effects as follows: use the FQPSK modulation that the physical-layer network coding signal is carried out permanent envelope protection; successfully solved at the relaying place detection and the classification problem of superposed signal; use a waveform bunch sorting criterion to replace existing constellation sorting criterion, avoided random this shortcoming of FQPSK modulation constellation.Simultaneously, the Viterbi that the present invention has utilized FQPSK to simplify receives grid chart, uses to unite and separates the mapping rectification, mixed signal is adjudicated out accurately, both reduce the complexity of receiving terminal, effectively increased system survivability again, increased the error performance of system.

Description of drawings

Fig. 1 is transmitting terminal of the present invention unit theory diagram.

Fig. 2 is receiving terminal unit theory diagram of the present invention.

Fig. 3 is the planisphere comparison diagram of FQPSK of the present invention and QPSK.

Fig. 4 is that the Viterbi of simplification of the present invention receives grid chart.

Fig. 5 is that the Viterbi under four states of the present invention receives grid chart.

Fig. 6 is the overall system performance figure under the different modulating parameter q condition of the present invention.

Fig. 7 is systematic function figure under Gauss's nonlinear channel of the present invention and the general channel of Gauss.

Fig. 8 is systematic function figure under the LDPC chnnel coding of the present invention.

Fig. 9 is the performance map of system under the different code check of the present invention.

Embodiment

The invention discloses a kind of physical-layer network coding method based on the FQPSK modulation, the transmitting terminal unit comprises the execution following steps:

In step S1, two signal sources are launched raw information x respectively _AAnd x _B

In step S2, with two raw information x _AAnd x _BBe modulated to after the modulation respectively and become the z that transmits above the high frequency carrier _AAnd z _B

In step S3, trunk module receives mixed signal indication and is: Y _R(t)=[z _A(t)+n (t)]+[z _B(t)+n'(t)], Y _R(t) the hybrid waveform signal that receives of expression;

In step S4, the signal x that trunk module will newly form _rBe modulated into constant envelope signal y again _r

In step S3, adopt the Waveform Matching technology for detection to go out the hybrid waveform Y of stack _R(t), according to the grid output of Waveform Matching all are formed Y _R(t) waveform signal is divided into two big classifications, and respectively these two classifications is mapped to network code subsymbol x _r∈ { 0,1}.

In described step S3, the baseband signal of FQPSK is formed based on 16 special waveforms, and the ability of each small form is different, thereby utilizes the relation that receives between signal and the transmitted signal energy to set sorting criterion.

In described step S2, two raw information x _AAnd x _BBecome the z that transmits above the high frequency carrier through being modulated to after LDPC coding module and the FQPSK module successively respectively _AAnd z _B

Also comprise receiving terminal unit, in receiving the unit, comprise the execution following steps: at first demodulate the new network signal x that forms of relaying by the MAP algorithm _r, unite then and separate the mapping demodulation, carry out the hard bit reversal decoding of LDPC at last by the LDPC decoder.

As shown in Figure 1, the invention also discloses a kind of physical-layer network coding system based on the FQPSK modulation, comprise the transmitting terminal unit, described transmitting terminal unit comprises first signal source 1 and the LDPC coding module 2 and the FQPSK module 3 that link to each other successively with described first signal source 1, and described first signal source 1 is used for emission raw information x _AAnd become the z that transmits above the high frequency carrier through being modulated to after a described LDPC coding module 2 and a FQPSK module 3 modulation _ADescribed transmitting terminal unit also comprises secondary signal source 4 and the 2nd LDPC coding module 5 and the 2nd FQPSK module 6 that link to each other successively with described secondary signal source 4, and described secondary signal source 4 is used for emission raw information x _BAnd become the z that transmits above the high frequency carrier through being modulated to after described the 2nd LDPC coding module 5 and the modulation of the 2nd FQPSK module 6 _BDescribed transmitting terminal unit also comprises trunk module 10, and described trunk module 10 is used for receiving z _AAnd z _BMixed signal indication is: Y _R(t)=[z _A(t)+n (t)]+[z _B(t)+n'(t)], Y _R(t) the hybrid waveform signal that receives of expression.

Described trunk module 10 comprises detection module 7, sort module 8, the 3rd FQPSK module 9.

Detection module 7: be used for adopting the Waveform Matching technology for detection to go out the hybrid waveform Y of stack _R(t);

Sort module 8: described sort module 8 links to each other with described detection module 7, and described sort module 8 is used for according to the grid output of Waveform Matching all being formed Y _R(t) waveform signal is divided into two big classifications, and respectively these two classifications is mapped to network code subsymbol x _r∈ { 0,1};

The 3rd FQPSK module 9: for the signal x that will newly form _rBe modulated into constant envelope signal y again _r

As shown in Figure 2, this physical-layer network coding system also comprises receiving terminal unit, described receiving terminal unit comprises MAP algoritic module 21, unites and separate mapping demodulation module 22 and LDPC decoder 23, described MAP algoritic module 21 outputs link to each other with described solution mapping demodulation module 22 inputs of uniting, and described MAP algoritic module 21 demodulates the new network signal x that forms of relaying by the MAP algorithm _r, described solution mapping demodulation module 22 outputs of uniting link to each other with described LDPC decoder 23 inputs, and described LDPC decoder 23 carries out the hard bit reversal decoding of LDPC.

In Fig. 1, suppose that three nodes all are time synchronized.Alice and Bob launch raw information x respectively _AAnd x _B, become the z that transmits above the high frequency carrier through being modulated to after LDPC chnnel coding and the permanent envelope modulation of FQPSK _AAnd z _BTwo paths of signals passes through respectively after the Gaussian channel, and relaying receives mixed signal and can be expressed as

Y _R(t)=[z _A(t)+n(t)]+[z _B(t)+n′(t)] （1）

Wherein, Y _R(t) the hybrid waveform signal that receives of expression, n (t) all is that average is 0 n'(t), variance is σ ²The Gaussian channel parameter.In the relay, adopt the Waveform Matching technology for detection to go out the hybrid waveform Y of stack _R(t).Subsequently, propose a kind of relaying sorting criterion of novelty among the present invention, according to the grid output of Waveform Matching all have been formed Y _R(t) waveform signal classification two big classifications, and respectively these two classifications are mapped to simple numeral symbol x _r∈ { 0,1}.At down link, the signal x that relaying will newly form _rBe modulated into constant envelope signal y again _r, be transmitted to two end nodes.

Down link, end node are separated earlier the modulation again of relaying with MAP, according to self nodal information and the superposed signal information that receives, infer the other side's information subsequently, and this paper has adopted to unite and separated the mapping demodulation mode and reduced complexity, has improved error performance.

Comprise that in the present invention the relaying superposed signal detects:

Briefly, FQPSK modulation is a kind of artificial modulation system of utilizing the accurate permanent envelope that 16 functions slap together, and it is to be based upon on the basis of QPSK, has eliminated the SPA sudden phase anomalies among the QPSK again, and the constellation comparison diagram of FQPSK and QPSK as shown in Figure 3.For example, after list entries is x=(1,1,0,0,1,0,1,0,0,0) process string and conversion, the x of sequence in the same way that we obtain _i=(1,0,1,1,0), quadrature x _q=(1,0,0,0,0).After through the computing cross-correlation unit, we have obtained the metric numeral of two-way: the I on I road _OutThe Q on=(1,15,6,12,8) and Q road _Out=(13,7,3,2,1).According to this two-way numeral, we select the waveform of appointment to replace corresponding bit from 16 wave functions.Here, the code word waveform on Q road will postpone the half symbols cycle to prevent the jump on the amplitude than I road, just makes modulation waveform keep accurate permanent envelope.

Because FQPSK is waveform modulated rather than phase place modulation system, its phase constellation point is irregular to be distributed on the unit circle, uses the signal of FQPSK modulation after the relaying stack when two-way, and the constellation of its overlaid waveforms is mixed and disorderly especially, has no rule and can say.Traditional physical-layer network coding all detects and divides classification at relay point according to constellation, when modulating based on FQPSK, the constellation sorting criterion is no longer suitable.Therefore, the present invention is directed to this waveform modulated system of FQPSK and proposed a kind of new waveform bunch sorting criterion, no longer rely on constellation classification in the past, but classify according to the feature that constitutes baseband signal waveform, introduce in detail below:

According to the coding rule of FQPSK, at N time slot, the baseband signal on I road and Q road is used x respectively _I(t)=s _i(t-nT _s) and x _Q(t)=s _j(t-nT _s+ T _s/ 2) expression, wherein s _i(t) and s _j(t) be 16 special waveforms forming base band, its following table i and j can directly try to achieve according to the coding rule of FQPSK.Therefore, the intact transmission signal of two-way modulated can be expressed as respectively

z _A(t)=x _I(t)+jx _Q(t)

$=\underset{n}{\mathrm{\Σ}}{s}_i(t-n{T}_s)+j\underset{n}{\mathrm{\Σ}}{s}_j(t-n{T}_s+T_s/2)$

z _B(t)=x _I'(t)+jx _Q'(t) （2）

$=\underset{n}{\mathrm{\Σ}}{s}_{i^{\′}}(t-n{T}_s)+j\underset{n}{\mathrm{\Σ}}{s}_{j^{\′}}(t-n{T}_s+T_s/2)$

The signal that band wherein ' signal that sends of expression Bob end, not with ' representative is sent from the Alice end.s _i(t) and s _j(t) be one-period [T _s/ 2, T _s/ 2] Nei signal.Superposed signal Y when two paths of signals gained after the relaying stack _RCan be expressed as

Y _R=z _A+z _B

$=(\underset{n}{\mathrm{\Σ}}{s}_i(t-n{T}_s)+\underset{n}{\mathrm{\Σ}}{s}_{i^{\′}}(t-n{T}_s))+---\left(3\right)$

$j(\underset{n}{\mathrm{\Σ}}{s}_j(t-{\mathrm{nT}}_s+T_s/2)+\underset{n}{\mathrm{\Σ}}{s}_{j^{\′}}(t-n{T}_s+T_s/2))$

In order to represent conveniently, I road and the Q road signal of superposed signal is expressed as respectively

$S_I=\underset{n}{\mathrm{\Σ}}{s}_i(t-n{T}_s)+\underset{n}{\mathrm{\Σ}}{s}_{i^{\′}}(t-n{T}_s)$

$S_Q=\underset{n}{\mathrm{\Σ}}{s}_j(t-{\mathrm{nT}}_s+T_s/2)+\underset{n}{\mathrm{\Σ}}{s}_{j^{\′}}(t-n{T}_s+T_s/2)---\left(4\right)$

In other words, in relay point reception place, we at first need to detect (S _I, S _Q) this combination.Consider in the superposed signal each component signal s _i(t), s _I'(t), s _j(t), s _J'(t) ∈ { s ₀, s ₁..., s ₁₅Form by these 16 basic waveforms, extrapolate the only S of single channel like this _IOr S _Q256 kinds of different forms are just arranged, let alone detect (S _I, S _Q) this has made up.In order to reduce the complexity that relaying detects, according to the simplification Viterbi reception model of FQPSK, we can be divided into 4 classes with 16 basic waveforms, as formula (5).Because classification has destroyed the correlation of I, Q two paths of signals among the FQPSK, the detection of I and Q road signal branch can being come

$\left.\begin{array}{c}{q}_0\left(t\right)=\frac{1}{4}\underset{i=0}{\overset{3}{\mathrm{\Σ}}}{s}_i\left(t\right)\\ q_1\left(t\right)=\frac{1}{4}\underset{i=4}{\overset{7}{\mathrm{\Σ}}}{s}_i\left(t\right)\\ q_2\left(t\right)=\frac{1}{4}\underset{i=8}{\overset{11}{\mathrm{\Σ}}}{s}_i\left(t\right)=-q_0\left(t\right)\\ q_3\left(t\right)=\frac{1}{4}\underset{i=12}{\overset{15}{\mathrm{\Σ}}}{s}_i\left(t\right)=-q_1\left(t\right)\end{array}\right\}---\left(5\right)$

Viterbi grid chart such as Fig. 4 after FQPSK simplifies.γ wherein _k/ q _i(t), i={0,1,2,3} are the transfering state condition, q _i(t) be the coupling waveform, γ _kBe coupling output.

Thus, same thought applies to detect (S _I, S _Q) combination, earlier with S _IAnd S _QTwo paths of signals is independent.For example, when we consider to detect wherein one road signal (I or Q), the superposed signal that receives can be expressed as table 1

Superposed signal waveform after table 1 is simplified

In table 1, p _Ii'(t)=q _i(t)+q _I'(t), i, i' ∈ 0,1,2,3}, and wherein subscript i represents the signal that the Alice end sends over, the signal that i ' expression Bob end sends, and after the two paths of signals stack, its baseband signal is made up of 16 kinds of waveform signals in the table 1.Thus, adopt the Viterbi decoding grid to receive figure, become four state transition diagrams by two condition, by the energy matched filter, each mark space self-energy biasing formula is

$V_{{\mathrm{ii}}^{\′}}\left(t\right)={\∫}_{-\frac{T_s}{2}}^{\frac{T_s}{2}}{p}_{{\mathrm{ii}}^{\′}}\left(t\right)*S_k\left(t\right)\mathrm{dt}-\frac{1}{2}{\∫}_{-\frac{T_s}{2}}^{\frac{T_s}{2}}{p}_{{\mathrm{ii}}^{\′}}\left(t\right)*p_{{\mathrm{ii}}^{\′}}\left(t\right)\mathrm{dt}---\left(6\right)$

Wherein, S _k(t), { I, Q} represent I road or the Q road signal that relaying receives, p to k ∈ _Ii'(t) be the superposed signal of mentioning in the table 1.According to viterbi algorithm, pick out in each symbol period maximum coupling output

V _max(t)=max(V _ii'(t)) （7）

According to the corresponding numeral sequence of maximum coupling output, Fig. 5 has represented the grid chart under the one of four states.

Comprise grid output category criterion in the present invention:

When the decoding grid chart of relaying according to Fig. 5, output corresponding a series of by the numeral sequence that 0,1,2} forms, this is one group of ternary sequence, directly it is modulated to enlarge bandwidth, this is not that we are desirable.We go above ternary need being mapped to binary sequence, in order to modulate with carrying out FQPSK again, guarantee that this system of down link still can resist non-linear effects.At first, according to Fig. 5, the identical waveform of all outputs is divided into a class sequence

Wherein, k ∈ { I, Q}, Υ _k() expression grid chart output valve.But formula (8) lining is ternary signal, this means the increase system bandwidth.Therefore, consider ternary is become binary signal, proposed a kind of effective denoising mapping Γ (), by being output as 0 and be output as 2 signal waveform and be mapped on a class " 0 " symbol, namely

$\mathrm{\Γ}\left(V_{\max }\left(t\right)\right)=\left\{\begin{array}{cc}0,& \mathrm{for}{V}_{\max }\left(t\right)=\left\{\begin{array}{c}{V}_{00}\left(t\right),V_{01}\left(t\right),V_{10}\left(t\right),V_{11}\left(t\right)\\ V_{22}\left(t\right),V_{23}\left(t\right),V_{32}\left(t\right),V_{33}\left(t\right)\end{array}\right\},\\ 1,& \mathrm{for}{V}_{\max }\left(t\right)=\left\{\begin{array}{c}{V}_{02}\left(t\right),V_{20}\left(t\right),V_{03}\left(t\right),V_{30}\left(t\right)\\ V_{12}\left(t\right),V_{21}\left(t\right),V_{13}\left(t\right),V_{31}\left(t\right)\end{array}\right\},\end{array}\right.---\left(9\right)$

The sort key of superposed signal is can not occur in the same classification several stacking patterns of same signal, in other words, namely in same classification, each superposed signal must be that different signals is formed by stacking, like this at receiving terminal, could can be according to self information and overlapped information, accurately, unique the other side's information of extrapolating.Yet formula but has the signal of obscuring easily in (9), as V ₀₀(t) and V ₀₁(t) two all is by q ₀(t) respectively with q ₀(t) and q ₁(t) metric that forms after the stack, this does not allow to occur in normal classification, because at receiving terminal, according to raw information q ₀(t) and the mapclass of superposed signal " 0 ", can't judge square signal is q ₀(t) still be q ₁(t).But herein, we need not consider this problem, and this paper back relies on to unite separates mapping demodulation meeting with this blurred signal accurately, solution is come out accurately.Subsequently, with the binary symbol sequence x that newly forms _r={ r ₁, r ₂..., r _NReuse FQPSK and be modulated into constant envelope signal, and launch.

Comprise in the present invention uniting and separate the mapping demodulation:

After end node receives repeating signal, receive different with conventional signal, this moment, the signal that receives was not the signal of our other end node directly wanted, neither the signal of two paths of signals after the relaying stack, and corresponding network code subsymbol x after the two paths of signals stack just _r={ r ₁, r ₂..., r _N, by a series of 0 or 1 signal of forming.How to extrapolate our needed information from these network symbols is the key point of technology.For example, the Alice end recovers the information of needed Bob, and certainly, the information that the Bob end recovers Alice also is same principle.Suppose that the signal that Alice receives is y' _r(t)={ r ₁', r ₂' ..., r _L', at first use the MAP algorithm to demodulate the new network signal x that forms of relaying _r, this network signal has only just carried the relation between Alice and the Bob signal.For example, if network signal is " 0 ", according to formula (9), can search out the superposed signal p that belongs to this class _Ii'(t), subsequently according to Alice self information q _i(t) ∈ { q ₀(t), q ₁(t), q ₂(t), q ₃(t) }, can further extrapolate the information q of Bob according to the relation between superposed signal in the table 1 and the primary signal _I'(t) ∈ { (q ₀(t) or q ₁(t)), (q ₂(t) or q ₃(t)) }. still, the way differentiation is not q on earth ₀Or q ₁, and be q ₂Or q ₃, by Fig. 4 Viterbi grid output map as can be seen, in the time of with the Viterbi demodulation, when coupling is q ₀Or q ₁The time, output all is to be 0, when coupling is q ₂Or q ₃The time, what export all is to be 1, therefore, we can be according to these characteristics of grid output, formulated to unite and separated the mapping demodulation, gone to have solved separating the ambiguity that stays after the mapping by demodulation, can easily extrapolate the information of Bob like this, can reduce the error rate again, also reduce the decoding complexity of receiving terminal simultaneously.

Comprise the combining LDPC channel coding in the present invention:

FQPSK can bring high power and high bandwidth efficiency, but because the complexity of himself numeral and we have adopted the simplification pattern when receiving, this must bring the high error rate, in order to improve the error performance of whole system, introduce the LDPC chnnel coding.

The decoding of LDPC is divided into two classes: hard-decision decoding and soft information decoding.Most systems all can be selected soft information decoding for use at present, because its performance can be approached shannon limit.But in native system, because the relaying transmission is not to be the direct information of the other side, being mapped to network numeral information but transmit after both superpose, is to infer according to relevant information needed information at receiving terminal.In whole process, can not extract the soft information of information to be decoded, so cause to use soft information solution LDPC sign indicating number.Therefore, in native system, employing be the hard bit reversal decoding of LDPC, can bring considerable gain for system equally.

Emulation and performance evaluation based on the physical-layer network coding system of FQPSK modulation:

In this section in the content, we have proved the impact of performance of the system that proposes by emulation, and performance is found out from every side, and this system can effectively prevent the non-linear amplification of channel.

Fig. 6 has proved that the q value was more big when the parameter q in the envelope function of FQPSK was even number, and the envelope after the modulation more levels off to permanent envelope, and systematic function will be more good.From Fig. 6 also as can be seen, when the error rate 10 ^-4The time, q=10 has improved the gain of 1dB than q=2.

Fig. 7 is the systematic function curve chart under the nonlinear channel model, has contrasted among the figure under nonlinear channel, because the existence of FQPSK modulation, it is little to make this entire system performance be subjected to non-linear effects, almost can ignore, and has effectively resisted the channel non-linearity amplification.

Fig. 8 and Fig. 9 all select the LDPC code word of the every frame of 1200 bits for use, emulation 1250 frame signals get the error rate that average is calculated.Fig. 8 selects for use code check to be

LDPC coding, the bit reversal iteration is set at 10 times during decoding.Fig. 8 has mainly given prominence to the effect of LDPC chnnel coding, as can be seen, is 10 in the error rate ^-4, the LDPC chnnel coding has improved the 4dB gain with systematic function.And two kinds of different hard bit reversal decoding performances are similar.Fig. 9 has showed the characteristic curve of error code of this system under the different code check situations, and as can be seen from Figure 9, selected code check is more low, and systematic function is more good.

When the present invention is directed to repeater satellite use physical-layer network coding system, the problem that nonlinear channel is bigger to this systematic influence has been set up the physical-layer network coding system based on the FQPSK modulation.Use the FQPSK modulation that the physical-layer network coding signal is carried out permanent envelope protection; successfully solved at the relaying place detection and the classification problem of superposed signal; use a waveform bunch sorting criterion to replace existing constellation sorting criterion, avoided random this shortcoming of FQPSK modulation constellation.Simultaneously, the Viterbi that the present invention has utilized FQPSK to simplify receives grid chart, uses to unite and separates the mapping rectification, mixed signal is adjudicated out accurately, both reduce the complexity of receiving terminal, effectively increased system survivability again, increased the error performance of system.

Passed through simulating, verifying at last based on the performance in the whole communication link of physical-layer network coding system of FQPSK modulation, under nonlinear channel, this system still keeps good performance, is not subjected to nonlinear too many influence.Thereby efficiently solve key issues such as the physical-layer network coding link is subjected to that nonlinear channel influences easily.

Above content be in conjunction with concrete preferred implementation to further describing that the present invention does, can not assert that concrete enforcement of the present invention is confined to these explanations.For the general technical staff of the technical field of the invention, without departing from the inventive concept of the premise, can also make some simple deduction or replace, all should be considered as belonging to protection scope of the present invention.

Claims (9)

1. physical-layer network coding method based on FQPSK modulation is characterized in that the transmitting terminal unit comprises the execution following steps:

A. two signal sources are launched raw information x respectively _AAnd x _B

B. with two raw information x _AAnd x _BBe modulated to after the modulation respectively and become the z that transmits above the high frequency carrier _AAnd z _B

C. trunk module receives mixed signal indication and is: Y _R(t)=[z _A(t)+n (t)]+[z _B(t)+n'(t)], Y _R(t) the hybrid waveform signal that receives of expression.

2. physical-layer network coding method according to claim 1 is characterized in that, in described step C, adopts the Waveform Matching technology for detection to go out the hybrid waveform Y of stack _R(t), according to the grid output of Waveform Matching all are formed Y _R(t) waveform signal is divided into two big classifications, and respectively these two classifications is mapped to network code subsymbol x _r∈ { 0,1}.

3. physical-layer network coding method according to claim 2 is characterized in that, also comprises step:

D. the trunk module signal x that will newly form _rBe modulated into constant envelope signal y again _r

4. physical-layer network coding method according to claim 2, it is characterized in that, in described step C, the baseband signal of FQPSK is formed based on 16 special waveforms, and the ability of each small form is different, thereby utilizes the relation that receives between signal and the transmitted signal energy to set sorting criterion.

5. according to each described physical-layer network coding method of claim 1 to 4, it is characterized in that, in described step B, two raw information x _AAnd x _BBecome the z that transmits above the high frequency carrier through being modulated to after LDPC coding module and the FQPSK module successively respectively _AAnd z _B

6. physical-layer network coding method according to claim 5 is characterized in that, also comprises receiving terminal unit, comprises the execution following steps in receiving the unit: at first demodulate the new network signal x that forms of relaying by the MAP algorithm _r, unite then and separate the mapping demodulation, carry out the hard bit reversal decoding of LDPC at last by the LDPC decoder.

7. physical-layer network coding system based on FQPSK modulation, it is characterized in that, comprise the transmitting terminal unit, described transmitting terminal unit comprises first signal source and the LDPC coding module and the FQPSK module that link to each other successively with described first signal source, and described first signal source is used for emission raw information x _AAnd become the z that transmits above the high frequency carrier through being modulated to after the modulation of a described LDPC coding module and a FQPSK module _ADescribed transmitting terminal unit also comprises secondary signal source and the 2nd LDPC coding module and the 2nd FQPSK module that link to each other successively with described secondary signal source, and described secondary signal source is used for emission raw information x _BAnd become the z that transmits above the high frequency carrier through being modulated to after the modulation of described the 2nd LDPC coding module and the 2nd FQPSK module _BDescribed transmitting terminal unit also comprises trunk module, and described trunk module is used for receiving z _AAnd z _BMixed signal indication is: Y _R(t)=[z _A(t)+n (t)]+[z _B(t)+n'(t)], Y _R(t) the hybrid waveform signal that receives of expression.

8. physical-layer network coding according to claim 7 system is characterized in that described trunk module comprises:

Detection module: be used for adopting the Waveform Matching technology for detection to go out the hybrid waveform Y of stack _R(t);

Sort module: described sort module links to each other with described detection module, and described sort module is used for according to the grid output of Waveform Matching all being formed Y _R(t) waveform signal is divided into two big classifications, and respectively these two classifications is mapped to network code subsymbol x _r∈ { 0,1};

The 3rd FQPSK module: for the signal x that will newly form _rBe modulated into constant envelope signal y again _r

9. physical-layer network coding according to claim 8 system, it is characterized in that, this physical-layer network coding system also comprises receiving terminal unit, described receiving terminal unit comprises the MAP algoritic module, unites and separate mapping demodulation module and LDPC decoder, described MAP algoritic module output links to each other with the described solution mapping demodulation module input of uniting, and described MAP algoritic module demodulates the new network signal x that forms of relaying by the MAP algorithm _r, the described solution mapping demodulation module output of uniting links to each other with described LDPC decoder input, and described LDPC decoder carries out the hard bit reversal decoding of LDPC.

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