CN102938669A - Method for suppressing Doppler spread in high-speed mobile environment - Google Patents

Abstract

The invention discloses a method for suppressing Doppler spread in a high-speed mobile environment. The problem of performance deterioration of a receiver in a high-speed mobile environment cannot be solved essentially in the prior art. The method includes constructing base vectors of space of each orthogonal angular domain; projecting received signals in the orthogonal angular domains; performing equivalent Doppler estimation on the orthogonal angular domains; compensating for the equivalent Doppler estimation on the orthogonal angular domains; and estimating channels on the orthogonal angular domains, demodulating signals on signals in the space of each orthogonal angular domain and performing maximum-ratio combining to suppress the Doppler spread. The method has the advantages that the redundancy in transmission of the data on the wireless channels can be reduced, and calculation is lowered as compared with the traditional method for suppressing Doppler spread in a high-speed mobile environment.

Description

The method that suppresses doppler spread under a kind of high-speed mobile environment

Technical field

The present invention relates to receiving system design under many antenna environment, particularly a kind of method that under high-speed mobile environment, suppresses doppler spread.

Background technology

Along with development and the expansion of mobile communication application, at some special occasions (for example high-speed railway), require in the situation of fast moving, can realize the high-speed transfer of data.Can bad student's doppler spread under the high-speed mobile.Have many reflectors in the wireless channel, and the signal that the base station sends reaches receiving terminal through wireless channel, will produce multipath effect.When between the transceiver communication end relative displacement being arranged, because variation has occured in the propagation path in each footpath, therefore at receiving terminal, variation has also occured in the phase place in each footpath, this moment, these phase places directly of synthetic equivalent diameter can be different along with the difference of location of mobile station, just produced thus the variation of amplitude and the phase place of synthetic equivalent diameter, owing to this variation is that variation along with location of mobile station changes, and the variation of location of mobile station is because the motion of travelling carriage causes, therefore the variation of equivalent diameter amplitude and phase place also namely is shown as the time-varying characteristics of channel with regard to showing as along with the time changes and changes.On the other hand, because the motion of travelling carriage, each arrives the footpath and produces Doppler frequency shift, because each arrives the inconsistent of the angle of arrival directly, the motion of travelling carriage is also inconsistent at the Doppler frequency shift that each arrives the footpath generation, therefore at receiving terminal, the signal in these footpaths of the synthetic distinguishable multipath of each time domain is alien frequencies out-phase, has just produced thus doppler spread.And the quick time-varying characteristics of this wireless channel that under high-speed mobile environment, causes, for receiver, can cause larger impact, be mainly reflected in the following aspects: at first, if receiver carries out coherent demodulation, become the difficulty that will cause channel estimation and tracking during channel quick.For addressing this problem, now general by adopting the mode of iterative interference cancellation, perhaps adopt the methods such as Interference Cancellation and windowing to suppress the interference that time varying channel causes.But these methods all are based under the known condition of multipath time varying channel parameter and solve the doppler spread problem, do not consider the complexity of channel estimating.In addition, in the known situation of multipath time varying channel parameter, separate that to be in harmonious proportion the detection algorithm complexity still higher.And consider the complexity of channel statistic, and the impact of doppler spread, so that existing a lot of method can not be from solving the problem that receiver performance worsens under the high-speed mobile environment in essence.

Summary of the invention

The present invention is directed to the deficiencies in the prior art, proposed to suppress under a kind of high-speed mobile environment the method for doppler spread.

Suppress the method for doppler spread under a kind of high-speed mobile environment of the present invention, specifically may further comprise the steps:

Step 1 is utilized the in advance orthogonal angle domain space base vector of structure

, to the multi-antenna signal that receives

Carry out rectangular projection, namely

Wherein

In the formula

Wherein

Be the normalization length after the normalization of reception antenna process carrier wavelength,

Be the normalization interval between the antenna, Be the reception antenna number.

Step 2 is on each orthogonal angle domain space, to the reception signal on k the Corner space after the projection

Carry out respectively Doppler parameter

Estimate, namely

In the formula

Be the length of periodic reference signal,

Be the sampling interval,

Cycle Length for reference signal;

Step 3 is utilized the Doppler parameter that obtains in each Corner space estimation

, the signal on each Corner space is carried out the Doppler parameter compensation, namely

Step 4 on each Corner space, utilizes the signal after Doppler parameter compensates to carry out channel estimating, estimates k the channel parameter on the Corner space

Channel estimating can adopt minimum variance estimate (LSE):

In the formula

,

,

Be the subcarrier number,

The expression diagonal matrix,

The reference symbol sequence that expression sends,

For

In the matrix that consists of of the column vector corresponding with the reference symbol position,

Step 5 utilizes channel estimation results to carry out coherent demodulation, obtains the demodulation symbol on each orthogonal angle domain space and carry out high specific merging, and obtains judgment variables

, namely

。

Utilize the space base vector of structure, will receive signal projection to the orthogonal angle domain space.On each Corner space, the angle of arrival that receives signal is limited in each Corner space scope.In the certain situation of antenna distance, it is relevant with the length of aerial array in each Corner space upper angle expansion to receive signal.The length of aerial array is larger, and it is less in each Corner space upper angle expansion to receive signal.Therefore in same Corner space, the difference of the angle of arrival in each footpath that receives diminishes along with the increase of aerial array length.When the length long enough of aerial array, enough little of the difference of the angle of arrival in each footpath that receives can be similar to and think identical.This moment, for the signal that projects on each Corner space, the signal in these footpaths of the synthetic distinguishable multipath of each time domain was with frequency out-phase at receiving terminal.And the effect that same frequently each signal of out-phase stacks up no longer shows as doppler spread, and shows as Doppler frequency shift.For Doppler frequency shift, can adopt the automatic frequency collimation technique to be estimated and compensate.In the present invention, respectively the equivalent Doppler parameter on each Corner space is estimated and compensated respectively, then the signal after the compensation is carried out maximum ratio and merge to obtain decoding and decision signal.

Beneficial effect of the present invention: (1) reduced to eat dishes without rice or wine redundancy of upper transfer of data, not needing frequency pilot sign is continuous in time, and the time interval between the frequency pilot sign is also large than conventional method, can reduce the redundancy of transfer of data on the wireless channel; (2) when carrying out channel estimating because on each orthogonal angle domain space, after the Doppler parameter compensation, receive channel is similar to and has experienced a quasistatic frequency-selective channel, therefore can adopt the channel estimation method under the common quasi-static channel opens, can adopt the single-order frequency domain to estimate, operand reduces a lot with respect to the conventional method under the high-speed mobile environment.

Embodiment

Suppress the method for doppler spread under the high-speed mobile environment of the present invention, specifically comprise the steps:

Step 1 is utilized the in advance orthogonal angle domain space base vector U of structure _r, the multi-antenna signal Y that receives is carried out rectangular projection, namely

Wherein

$U_r=\left[\begin{array}{cccc}{e}_r\left(0\right)& e_r\left(\frac{1}{L_r}\right)& ...& e_r\left(\frac{n_r-1}{L_r}\right)\end{array}\right]$

In the formula

$e_r\left(\mathrm{\Ω}\right)=\frac{1}{\sqrt{n_r}}\left[\begin{array}{c}1\\ \exp (-j2\mathrm{\π}{\mathrm{\Δ}}_r\mathrm{\Ω})\\ .\\ .\\ .\\ \exp -(-j2\mathrm{\π}(n_r-1){\mathrm{\Δ}}_r\mathrm{\Ω})\end{array}\right]$

L wherein _rBe the normalization length after the normalization of reception antenna process carrier wavelength, Δ _r=L _r/ n _rBe the normalization interval between the antenna, n _rBe the reception antenna number.

Step 2 is on each orthogonal angle domain space, to the reception signal on k the Corner space after the projection

Carry out respectively Doppler parameter

Estimate, namely

In the formula

Be the length of periodic reference signal,

Be the sampling interval,

Cycle Length for reference signal;

Step 3 is utilized the Doppler parameter that obtains in each Corner space estimation , the signal on each Corner space is carried out the Doppler parameter compensation, namely

Step 4 on each Corner space, utilizes the signal after Doppler parameter compensates to carry out channel estimating, estimates k the channel parameter on the Corner space

Channel estimating can adopt minimum variance estimate (LSE):

In the formula

,

,

Be the subcarrier number,

The expression diagonal matrix,

The reference symbol sequence that expression sends,

For

In the matrix that consists of of the column vector corresponding with the reference symbol position,

Step 5 utilizes channel estimation results to carry out coherent demodulation, obtains the demodulation symbol on each orthogonal angle domain space and carry out high specific merging, and obtains judgment variables

, namely

。

Claims (1)

1. suppress the method for doppler spread under the high-speed mobile environment, it is characterized in that the method specifically may further comprise the steps:

Step 1 is utilized the in advance orthogonal angle domain space base vector of structure

, to the multi-antenna signal that receives

Carry out rectangular projection, namely

Wherein

In the formula

Wherein Be the normalization length after the normalization of reception antenna process carrier wavelength,

Be the normalization interval between the antenna,

Be the reception antenna number;

Step 2 is on each orthogonal angle domain space, to the reception signal on k the Corner space after the projection

Carry out respectively Doppler parameter

Estimate, namely

In the formula

Be the length of periodic reference signal, Be the sampling interval,

Cycle Length for reference signal;

Step 3 is utilized the Doppler parameter that obtains in each Corner space estimation , the signal on each Corner space is carried out the Doppler parameter compensation, namely

Step 4 on each Corner space, utilizes the signal after Doppler parameter compensates to carry out channel estimating, estimates k the channel parameter on the Corner space

Channel estimating can adopt minimum variance estimate:

In the formula

,

,

Be the subcarrier number,

The expression diagonal matrix,

The reference symbol sequence that expression sends,

For

In the matrix that consists of of the column vector corresponding with the reference symbol position,

Step 5 utilizes channel estimation results to carry out coherent demodulation, obtains the demodulation symbol on each orthogonal angle domain space and carry out high specific merging, and obtains judgment variables , namely

。