CN102857468A - SC-FDE (single carrier with frequency-domain equalization) system based on MAP (maximum a posterior) equalization and construction method of pilot frequency structure therein - Google Patents

Abstract

An SC-FDE system based on MAP equalization and a method for constructing a pilot structure in the system relate to an SC-FDE system and a method for constructing a pilot structure in the system. It solves the problem that the peak-to-average ratio of the transmitted signal of the OFDM system is high and is sensitive to frequency offset and phase noise. The mapping signal input end of the mapping unit is connected to the signal output end of the signal generating device, and the modulation signal output end of the modulator is connected to the signal input end of the channel; the signal output end of the channel is connected to the signal input end of the Fourier transform module; The transformed signal output end of the leaf transform module is connected with the transformed signal input end of the channel estimation and equalization unit; the signal output end of the channel estimation and equalization unit is connected with the signal input end of the inverse Fourier transform module; the demodulated signal of the demodulator The output end is connected to the demodulation signal input end of the decoder; the decoding signal output end of the decoder is connected to the decoding signal input end of the judging unit. It is used to eliminate multipath effects in single carrier systems.

Description

Construction method based on pilot configuration in the SC-FDE system of MAP equilibrium and this system

Technical field

The present invention relates to pilot configuration construction method in SC-FDE system and this system.

Background technology

The pilot configuration of communication system also can be described as frame structure, i.e. the formation scheme of data in the transmission.Such as Fig. 1, general pilot configuration comprises three parts, CP (Cyclic Prefixed), pilot tone and data.CP is Cyclic Prefix, and its effect is that normally the final stage with frame data copies to whole frame foremost for the opposing multidiameter delay.The length of CP will be determined according to channel conditions, usually is greater than maximum multidiameter delay long, and the data of guarantee CP back are not affected by intersymbol interference like this.The purposes of pilot portion mainly is for the channel estimating of receiving terminal and equilibrium.The balance module of receiving terminal is proved the to a great extent performance of elevator system by theory and practice, particularly under the multidiameter fading channel environment.Data division is exactly the content that really will transmit, and CP and pilot tone all are to play the auxiliary transmission effect.But because CP and pilot tone all belong to invalid data, in order to improve the efficiency of transmission of system, therefore CP and pilot tone are merged, pilot tone will substitute the effect of CP this moment, and this scheme maturation is applied to a lot of occasions.Pilot configuration is from being divided in shape two kinds of serial type frame structure and block frame structures.

The channel estimating of system receiving terminal and equalization methods are most important on the impact of single-carrier system performance, and channel estimating is divided into blind estimation and non-blind estimation substantially.Blind estimation does not rely on pilot transmission, can save system resource, improves efficiency of transmission.But it is higher that blind estimation exists complexity, the shortcoming that precision is limited.Channel estimating and equalization algorithm be the solving multipath effect problem to a great extent, and different pilot configurations also is a key factor that affects frequency domain equalization system performance and communication efficiency simultaneously.General pilot configuration design need to depend on specific channel estimation methods or equalization methods, because under different estimations and the equalization algorithm, choosing of the variation of pilot configuration and pilot frequency sequence can produce different effects.

Traditional single-carrier system adopts time domain equalization to eliminate multipath effect, but that this generally is considered to complexity is higher.Orthogonal frequency division multiplex OFDM: the appearance of Orthogonal Frequency Division Multiplexing system has solved the high problem of complexity of equalization, but it is high that ofdm system exists the peak-to-average force ratio that transmits, to frequency deviation and phase noise than more sensitive shortcoming.

Summary of the invention

The present invention is high for solving the ofdm system peak-to-average force ratio that transmits, to frequency deviation and phase noise sensitive issue relatively, and the construction method based on pilot configuration in the SC-FDE system of MAP equilibrium and this system of proposition.

Based on the SC-FDE system of MAP equilibrium, the SC-FDE system is comprised of transmitting terminal module, channel mechanism and receiving terminal module; Described transmitting terminal module is made of map unit, decoder and modulator; Described channel mechanism is made of channel; Described receiving terminal module is comprised of Fourier transform module, channel estimating and equilibrium degree unit, inversefouriertransform module, demodulator, decoder and judging unit; The mapping signal input of described map unit links to each other with the signal output part of signal generation apparatus, the mapping signal output of described map unit links to each other with the mapping signal input of decoder, and the decoded signal output of described decoder links to each other with the decoded signal input of modulator; The modulation signal output of described modulator links to each other with the signal input part of channel; The signal output part of channel links to each other with the signal input part of Fourier transform module; The figure signal output of described Fourier transform module links to each other with the figure signal input of channel estimating and balanced unit; The signal output part of described channel estimating and balanced unit links to each other with the signal input part of inversefouriertransform module; The figure signal output of described inversefouriertransform module links to each other in the figure signal input of demodulator: the restituted signal output of described demodulator links to each other with the restituted signal input of decoder; The decoded signal output of described decoder links to each other with the decoded signal input of judging unit; The decision signal output of described judging unit links to each other with the receiver port of external signal receiving system.

Adopt the pilot configuration construction method of above-mentioned SC-FDE system based on the MAP equilibrium; Described construction method is finished by following steps:

Step 1: determine multi-path fading channel, fading channel model is seen formula 1 in the described SC-FDE system;

Formula 1

Parameter N is path number in the formula 1, and parameters ai and parameter τ i represent respectively amplitude damping factor and the propagation delay of i paths, parameter

It is the phase place between straight line path and the transmission path;

Parameter Tm represents that maximum multipath time delay is long;

Be maximum multipath time delay length be each the footpath time delay maximum multiply by transmission rate; Simultaneously determine frame length T according to multipath channel models; The length of described frame length T will guarantee that channel status does not change in frame data transmission duration;

Step 2: prolong T when utilizing the definite maximum of step 1 the more directly _mWith frame length T, determine the pilot length T in the frame data of pilot configuration in conjunction with the MAP balanced way _pWith the valid data length T _dThe relation of signal to noise ratio and effective frame length is seen formula 2 under the MAP balanced way;

${\mathrm{SNR}}_{\mathrm{MAP},\mathrm{eff}}=\frac{T-T_p}{\mathrm{<figure-callout\; id="2"\; label="T\; d\; min"\; filenames="HDA00002148561800012.png"\; state="\{\{state\}\}">T</figure-callout>}}\frac{d_{\min }^{}}{}\frac{{}_2^{}}{4{\mathrm{\&sigma;}}^2}{(1+\frac{L}{T_p-L+1})}^{-1}$ Formula 2

Parameter T in the formula 2 _pFor pilot tone is long, parameter

Be the channel minimum range, parameter L is the channel memory span, parameter σ ²Be the ambient noise performance number; The length of described pilot length Tp is less than the length of frame length T; The Nash Equilibrium equation of using in the theory of games is seen formula 3:

$J_i({T_p}^{*},T_d^{*})\&GreaterEqual;J_i(T_{p_i},T_{d_i}),\&ForAll;i=\mathrm{1,2},\&CenterDot;\&CenterDot;\&CenterDot;,N.$ Formula 3

By the Nash Equilibrium equation is derived, the desirable pilot tone length and the data length that obtain are respectively:

T _p=T/4+T _m/ 2 and T _d=T/4-T _m/ 2;

Step 3: according to the pilot length T that determines in the step 2 _p, be T according to the formula generation pilot length of Zadoff-Chu sequence of complex numbers x (n) _pPilot tone;

Step 4: channel estimating and equilibrium degree unit 9 receive the data that comprise pilot tone, and after the pilot tone in these data and valid data are extracted, carry out channel estimating according to the LS channel estimation method, and defeated channel function after estimating

Described

It is an impulse function;

Step 5: obtain impulse Response Function after the LS channel estimating by step 4

This impulse Response Function is delivered to the MAP equalizer utilizes the relational expression of MAP equalizer to carry out equilibrium treatment;

Step 6: the data communication device that obtains after the MAP equalizer processes with step 5 is crossed the decoding of decoding of decoder in the SC-FDE system and decoder, obtains final valid data.

SC-FDE system based on the MAP equilibrium of the present invention has that the peak-to-average force ratio of transmitting is low, and insensitive to frequency deviation and phase noise, complexity is lower, and precision is higher, the advantage that efficiency of transmission is higher.

Description of drawings

Fig. 1 is existing pilot configuration schematic diagram;

Fig. 2 is the modular structure schematic diagram of the described SC-FDE system based on the MAP equilibrium of the application.

Embodiment

Embodiment one: in conjunction with Fig. 2 present embodiment is described, the described SC-FDE system based on the MAP equilibrium of present embodiment, the SC-FDE system is comprised of transmitting terminal module 1, channel mechanism 2 and receiving terminal module 3; Described transmitting terminal module 1 is made of map unit 4, decoder 5 and modulator 6; Described channel mechanism 2 is made of channel 7; Described receiving terminal module 3 is comprised of Fourier transform module 8, channel estimating and equilibrium degree unit 9, inversefouriertransform module 10, demodulator 11, decoder 12 and judging unit 14; The mapping signal input of described map unit 4 links to each other with the signal output part of signal generation apparatus, the mapping signal output of described map unit 4 links to each other with the mapping signal input of decoder 5, and the decoded signal output of described decoder 5 links to each other with the decoded signal input of modulator 6; The modulation signal output of described modulator 6 links to each other with the signal input part of channel 7; The signal output part of channel 7 links to each other with the signal input part of Fourier transform module 8; The figure signal output of described Fourier transform module 8 links to each other with the figure signal input of channel estimating and balanced unit 9; The signal output part of described channel estimating and balanced unit 9 links to each other with the signal input part of inversefouriertransform module 10; The figure signal output of described inversefouriertransform module 10 links to each other in the figure signal input of demodulator 11: the restituted signal output of described demodulator 11 links to each other with the restituted signal input of decoder 12; The decoded signal output of described decoder 12 links to each other with the decoded signal input of judging unit 13; The decision signal output of described judging unit 13 links to each other with the receiver port of external signal receiving system.

In transmitting terminal module 1, at first with the signal data Sn map decoding that receives, after ovennodulation, pass through fading channel.The signal of process channel had noise Wn and adds before arriving receiving terminal.After receiving terminal receives data, carry out first Fourier transform (FFT), then carry out channel estimating and equilibrium, purpose is in order to resist the factors such as multipath interference in the transmission.Balanced is exactly inversefouriertransform (IFFT) later, and last demodulating and decoding is being adjudicated the data Rn that can obtain wanting.The SC-FDE system is single carrier with frequency-domain equalization system, and the MAP equilibrium is that maximum a posterior is balanced.

Embodiment two: in conjunction with Fig. 2 present embodiment is described, present embodiment is for adopting the pilot configuration construction method of the described SC-FDE system based on the MAP equilibrium of embodiment one; Described construction method is finished by following steps:

Step 1: determine multi-path fading channel, fading channel model is seen formula 1 in the described SC-FDE system;

Formula 1

Parameter N is path number in the formula 1, parameter a _iWith parameter τ _iThe amplitude damping factor and the propagation delay that represent respectively the i paths, parameter

It is the phase place between straight line path and the transmission path;

Parameter Tm represents that maximum multipath time delay is long;

Be maximum multipath time delay length be each the footpath time delay maximum multiply by transmission rate; Simultaneously determine frame length T according to multipath channel models; The length of described frame length T will guarantee that channel status does not change in frame data transmission duration;

Step 2: prolong T when utilizing the definite maximum of step 1 the more directly _mWith frame length T, determine the pilot length T in the frame data of pilot configuration in conjunction with the MAP balanced way _pWith the valid data length T _dThe relation of signal to noise ratio and effective frame length is seen formula 2 under the MAP balanced way;

${\mathrm{SNR}}_{\mathrm{MAP},\mathrm{eff}}=\frac{T-T_p}{\mathrm{<figure-callout\; id="2"\; label="T\; d\; min"\; filenames="HDA00002148561800012.png"\; state="\{\{state\}\}">T</figure-callout>}}\frac{d_{\min }^{}}{}\frac{{}_2^{}}{4{\mathrm{\&sigma;}}^2}{(1+\frac{L}{T_p-L+1})}^{-1}$ Formula 2

Parameter T in the formula 2 _pFor pilot tone is long, parameter

Be the channel minimum range, parameter L is the channel memory span, parameter σ ²Be the ambient noise performance number; The length of described pilot length Tp is less than the length of frame length T; The Nash Equilibrium equation of using in the theory of games is seen formula 3:

$J_i({T_p}^{*},T_d^{*})\&GreaterEqual;J_i(T_{p_i},T_{d_i}),\&ForAll;i=\mathrm{1,2},\&CenterDot;\&CenterDot;\&CenterDot;,N.$ Formula 3

By the Nash Equilibrium equation is derived, the desirable pilot tone length and the data length that obtain are respectively:

T _p=T/4+T _m/ 2 and T _d=T/4-T _m/ 2;

Step 3: according to the pilot length T that determines in the step 2 _p, be T according to the formula generation pilot length of Zadoff-Chu sequence of complex numbers x (n) _pPilot tone;

Step 4: channel estimating and equilibrium degree unit 9 receive the data that comprise pilot tone, and after the pilot tone in these data and valid data are extracted, carry out channel estimating according to the LS channel estimation method, and defeated channel function after estimating

Described

It is an impulse function;

Step 5: obtain impulse Response Function after the LS channel estimating by step 4

This impulse Response Function is delivered to the MAP equalizer utilizes the relational expression of MAP equalizer to carry out equilibrium treatment;

Step 6: the data communication device that obtains after the MAP equalizer processes with step 5 is crossed the decoding of decoding of decoder in the SC-FDE system and decoder, obtains final valid data.

Embodiment three: present embodiment and embodiment two differences are the pilot configuration construction method of described SC-FDE system based on the MAP equilibrium, and the formula of the Zadoff-Chu sequence of complex numbers x (n) in the step 3 is:

Formula 4

Wherein, n=1,2 ..., T _p, j is imaginary symbols.Other parameter and step are identical with embodiment two.

Embodiment four: present embodiment and embodiment two differences are the pilot configuration construction method of described SC-FDE system based on the MAP equilibrium, and the formula of the LS channel estimation method in the step 4 is:

${\hat{H}}_{\mathrm{LS}}=X^{-1}\stackrel{\&OverBar;}{Y}={\left[(X_k/Y_k)\right]}^T,(k=\mathrm{0,1},...,N-1)$ Formula 5

Wherein, parameter

Be the impulse function of channel estimating output, parameter X is that known pilot data is carried out the estimated value that obtains after the interpolation, and parameter Y is the data that obtain through Fourier transforms in receiving terminal module 3.Other parameter and step are identical with embodiment two.

Embodiment five: present embodiment and embodiment two differences are the pilot configuration construction method of described SC-FDE system based on the MAP equilibrium, and the relational expression of the MAP equalizer in the step 5 is

$\underset{\&OverBar;}{\overset{^}{S}}\arg \underset{\underset{\&OverBar;}{u}}{\min }\left(\right||\underset{\&OverBar;}{x}-\mathrm{\&tau;}\left(\underset{\&OverBar;}{h}\right)\underset{\&OverBar;}{u}||:\underset{\&OverBar;}{u}\&Element;A^{T+L-1})$ Formula 6

Parameter in the formula 6

Be the estimated value of symbol transposition to be asked, parameter argmin is the variable u value that makes the target function minimum, parameter xThe input signal of equalizer, parameter hBe the channel impulse function, parameter τ is the Toeplitz matrix, and parameter A is the data acquisition system of corresponding modulating mode, uses BPSK modulation A={+1 ,-1}.Other parameter and step are identical with embodiment two.

Claims (5)

1. based on the SC-FDE system of MAP equilibrium, it is characterized in that what the SC-FDE system was comprised of transmitting terminal module (1), channel mechanism (2) and receiving terminal module (3); Described transmitting terminal module (1) is made of map unit (4), decoder (5) and modulator (6); Described channel mechanism (2) is made of channel (7); Described receiving terminal module (3) is comprised of Fourier transform module (8), channel estimating and equilibrium degree unit (9), inversefouriertransform module (10), demodulator (11), decoder (12) and judging unit (14); The mapping signal input of described map unit (4) links to each other with the signal output part of signal generation apparatus, the mapping signal output of described map unit (4) links to each other with the mapping signal input of decoder (5), and the decoded signal output of described decoder (5) links to each other with the decoded signal input of modulator (6); The modulation signal output of described modulator (6) links to each other with the signal input part of channel (7); The signal output part of channel (7) links to each other with the signal input part of Fourier transform module (8); The figure signal output of described Fourier transform module (8) links to each other with the figure signal input of channel estimating with balanced unit (9); The signal output part of described channel estimating and balanced unit (9) links to each other with the signal input part of inversefouriertransform module (10); The figure signal output of described inversefouriertransform module (10) links to each other in the figure signal input of demodulator (11): the restituted signal output of described demodulator (11) links to each other with the restituted signal input of decoder (12); The decoded signal output of described decoder (12) links to each other with the decoded signal input of judging unit (13); The decision signal output of described judging unit (13) links to each other with the receiver port of external signal receiving system.

2. adopt the pilot configuration construction method of the SC-FDE system based on the MAP equilibrium claimed in claim 1; It is characterized in that described construction method finished by following steps:

Step 1: determine multi-path fading channel, fading channel model is seen formula 1 in the described SC-FDE system;

Formula 1

Parameter N is path number in the formula 1, parameter a _iWith parameter τ _iThe amplitude damping factor and the propagation delay that represent respectively the i paths, parameter It is the phase place between straight line path and the transmission path;

Parameter T _mThe expression maximum multipath time delay is long;

Be maximum multipath time delay length be each the footpath time delay maximum multiply by transmission rate; Simultaneously determine frame length T according to multipath channel models; The length of described frame length T will guarantee that channel status does not change in frame data transmission duration;

Step 2: prolong T when utilizing the definite maximum of step 1 the more directly _mWith frame length T, determine the pilot length T in the frame data of pilot configuration in conjunction with the MAP balanced way _pWith the valid data length T _dThe relation of signal to noise ratio and effective frame length is seen formula 2 under the MAP balanced way;

${\mathrm{SNR}}_{\mathrm{MAP},\mathrm{eff}}=\frac{T-T_p}{T}\frac{d_{\min }^2}{4{\mathrm{\&sigma;}}^2}{(1+\frac{L}{T_p-L+1})}^{-1}$ Formula 2

Parameter T in the formula 2 _pFor pilot tone is long, parameter

Be the channel minimum range, parameter L is the channel memory span, parameter σ ²Be the ambient noise performance number; The length of described pilot length Tp is less than the length of frame length T; The Nash Equilibrium equation of using in the theory of games is seen formula 3:

$J_i({T_p}^{*},T_d^{*})\&GreaterEqual;J_i(T_{p_i},T_{d_i}),\&ForAll;i=\mathrm{1,2},\&CenterDot;\&CenterDot;\&CenterDot;,N.$ Formula 3

By the Nash Equilibrium equation is derived, the desirable pilot tone length and the data length that obtain are respectively:

T _p=T/4+T _m/ 2 and T _d=T/4-T _m/ 2;

Step 3: according to the pilot length T that determines in the step 2 _p, be T according to the formula generation pilot length of Zadoff-Chu sequence of complex numbers x (n) _pPilot tone;

Step 4: channel estimating and equilibrium degree unit (9) receive the data that comprise pilot tone, and after the pilot tone in these data and valid data are extracted, carry out channel estimating according to the LS channel estimation method, and defeated channel function after estimating

Described

It is an impulse function;

Step 5: obtain impulse Response Function after the LS channel estimating by step 4 This impulse Response Function is delivered to the MAP equalizer utilizes the relational expression of MAP equalizer to carry out equilibrium treatment;

Step 6: the data communication device that obtains after the MAP equalizer processes with step 5 is crossed the decoding of decoding of decoder in the SC-FDE system and decoder, obtains final valid data.

3. the pilot configuration construction method of the SC-FDE system based on the MAP equilibrium according to claim 2 is characterized in that the formula of the Zadoff-Chu sequence of complex numbers x (n) in the step 3 is:

Formula 4

Wherein, n=1,2 ..., T _p, j is imaginary symbols.

4. the pilot configuration construction method of the SC-FDE system based on the MAP equilibrium according to claim 2 is characterized in that the formula of the LS channel estimation method in the step 4 is:

${\hat{H}}_{\mathrm{LS}}=X^{-1}\stackrel{\&OverBar;}{Y}={\left[(X_k/Y_k)\right]}^T,(k=\mathrm{0,1},...,N-1)$ Formula 5

Wherein, parameter Be the impulse function of channel estimating output, parameter X is that known pilot data is carried out the estimated value that obtains after the interpolation, and parameter Y is the data that obtain through Fourier transform in receiving terminal module (3).

5. the pilot configuration construction method of the SC-FDE system based on the MAP equilibrium according to claim 2 is characterized in that the relational expression of the MAP equalizer in the step 5 is

$\underset{\&OverBar;}{\overset{^}{S}}\arg \underset{\underset{\&OverBar;}{u}}{\min }\left(\right||\underset{\&OverBar;}{x}-\mathrm{\&tau;}\left(\underset{\&OverBar;}{h}\right)\underset{\&OverBar;}{u}||:\underset{\&OverBar;}{u}\&Element;A^{T+L-1})$ Formula 6

Parameter in the formula 6

Be the estimated value of symbol transposition to be asked, parameter argmin is the variable u value that makes the target function minimum, parameter xThe input signal of equalizer, parameter hBe the channel impulse function, parameter τ is the Toeplitz matrix, and parameter A is the data acquisition system of corresponding modulating mode, uses BPSK modulation A={+1 ,-1}.

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