CN100518011C - Adaptive diversity merging method of base band receiver for double antenna system - Google Patents

Abstract

The method includes steps: (1) calculating both signal level values received by the twin antenna, the energy of channel parameter estimate value and noise square-root difference estimate value; (2) comparing both signal level values with the preset threshold; if both signal values are greater than preset, then turning to step 3; if only one signal value is great than preset, it decodes and equilibrates the one greater; if both values are less than preset, steps finish; (3) comparing whether the energy sum of both channel parameter estimate values is in set range; if yes, then turning to step 4; otherwise, it demodulates and equilibrates only the greater one; (4) if both signal noise square-root difference estimate values are less than the threshold, then carrying out merger of equal gain for the two signals, demodulating and equilibrating both signal; otherwise, max-ratio combines, demodulates and equilibrates them. This method is simple and efficient.

Description

The adaptive diversity merging method of band receiver of base in the dual-antenna system

Technical field

The present invention relates to diversity combining method in the mobile radio system, relate in particular to the adaptive diversity merging method of band receiver of base in a kind of dual-antenna system.

Background technology

In mobile communication process, the characteristic of channel of wireless channel is very abominable, mainly shows as multipath fading and Doppler decline.This will cause the wireless signal incoming level to drop near the thermal noise level, and phase place also produces change at random in time, thereby cause communication quality to descend.At this problem, generally can adopt diversity receiving technology to alleviate the influence of decline, obtain diversity gain, improve receiving sensitivity.The method of diversity has a variety of, mainly contains space diversity, frequency diversity, polarization diversity, angle diversity, time diversity and component diversity etc.Realize simple and diversity gain advantages of higher because space diversity reception has, in mobile communication system, adopt space diversity reception to communicate usually.

Space diversity reception utilizes how secondary reception antenna to realize.Adopt the common antenna emission at transmitting terminal, and adopt multiple antenna to receive at receiving terminal.The receiving terminal multiple antenna between separately apart from d 〉=λ/2 (λ is an operation wavelength), fading characteristic with assurance reception antenna output signal is separate, that is to say, when the output signal of a certain secondary reception antenna is very low, the low phenomenon of amplitude then not necessarily also appears in the output of these other reception antennas of moment, through corresponding therefrom big, the best a few roads of signal to noise ratio of select-out signal amplitude of circuit that merge, obtain a total reception antenna output signal.So just can reduce the influence of channel fading, thereby improve transmission performance.

In general, in mobile communication system, signal receiver carries out analog down with radiofrequency signal, the output intermediate-freuqncy signal.Then this intermediate-freuqncy signal is carried out the A/D conversion, changes it into digital signal, again by Digital Down Converter Module (Digital Down Conversion) with digitized intermediate-freuqncy signal down-conversion, output baseband digital I handle to baseband processor.If the employing diversity technique then needs diversity signal with many antennas to be sent to baseband processor and handles.Baseband processor merges the technology that the multiple signals that receive adopt diversity to merge to signal, obtains maximum signal to noise ratio income.The selective merging of merging method commonly used at present, switching merging, high specific merging, equal gain combining etc.

The patent No. is in the foreign patent that is entitled as " Selective Diversity Combining " of WO98/53560, has proposed the method and apparatus that a kind of controllable realization diversity merges.This device at first obtains the interference strength of received signal according to interference analyzer, judge then whether this interference strength surpasses a predetermined threshold value, if surpassed this threshold value, then adopt the method for disturbing inhibition to merge IRC (Interference Rejection Combining) to carry out diversity and merge, otherwise the method that adopts high specific to merge is carried out the diversity merging.This invention needs an interference analyzer to determine the correlation and the interference of two paths of signals, has increased the expense of software like this.In addition,, adopt the method not only can not bring diversity gain, also can worsen the performance of band receiver of base when one road signal wherein is pure noise signal.

Application number is to be to be entitled as on July 9th, 1999 to have proposed a kind of method of controlling the weight of multipath reception unit by the FER (Floating Error Rate) that monitors the reception data in " diversity merging receiver " Chinese patent 99109577.4 applyings date.By the incoming level value of every road signal as weight, when FER (Floating Error Rate) greater than the regulation thresholding the time, the diversity pretreatment unit is determined the receiving element of makeing mistakes, make the weight of wrong receiving element equal 0, keep communication quality in the time of can making one or more receiving element received signal qualities of diversity merging receiver relatively poor like this.In this technical scheme, Weight Determination is not that the signal to noise ratio according to multiple signals obtains, but determines weight by the incoming level value.Can not guarantee that like this high specific diversity merges obtainable maximum gain.The another one shortcoming of this technical scheme is to need an error rate detector to calculate FER (Floating Error Rate), has increased overhead.

Application number is to be to be entitled as the method and apparatus that " method and the device of realizing digital selection diversity " proposed a kind of digital selection diversity December 31 calendar year 2001 01131668.3 applying date.This device deals with intensity indication detected value of the two-way received signal of reading in, selects the big signal of one tunnel intensity indication as temporary transient signal source, and the received signal data of temporary transient signal source are carried out quality testing, selects aerial signal according to the result who detects.The method can be in real time selected the good signal of one road received signal quality and is used for subsequent treatment the demodulated received signal respectively from multichannel, makes system not be vulnerable to the influence of isolated noise pulse and produces mistake and switch.The shortcoming of this method is only to have adopted the method for selecting one road signal, does not merge the gain that is brought and use the multiple signals diversity.

As seen, above-mentioned diversity receiving technology scheme is also immature, more or less all has problem.The signal that adopts above-mentioned diversity receiving technology to obtain not is best received signal.

Summary of the invention

At the existing problem and shortage of diversity combining method in the above-mentioned existing mobile radio system, the purpose of this invention is to provide the adaptive diversity merging method that a kind of compatibility is good, realize band receiver of base in the dual-antenna system simple, that stability is higher.

The present invention is achieved in that the adaptive diversity merging method of band receiver of base in a kind of dual-antenna system, may further comprise the steps:

(1) calculate respectively each signal that described double antenna receives level value, channel parameter estimation value energy and and the Noise Variance Estimation value;

(2) judge the size of each received signal level value and setting threshold respectively, if two received signal level values all greater than setting threshold, then enter step (3); If one of them is greater than setting threshold, then only keep this greater than one road signal of setting threshold as useful signal, carry out the demodulation equilibrium treatment; If two received signal level values are all less than setting threshold, then two paths of signals is invalid signals, and step finishes;

(3) relatively the energy of the channel parameter estimation value of two paths of signals and the merchant whether in setting number range, if, then enter step (4), otherwise keep energy with big channel parameter estimation value and road signal as useful signal, only this useful signal is carried out the demodulation equilibrium treatment;

(4) whether the Noise Variance Estimation value of judging two paths of signals is all less than setting threshold, if then this two paths of signals is carried out equal gain combining, and the signal that these gains are merged carries out the demodulation equilibrium treatment; Otherwise this two paths of signals is carried out high specific to be merged, the energy of the channel parameter estimation value of each road signal and and the ratio of Noise Variance Estimation value as the weight of this road signal in the high specific merge algorithm, and the signal that this high specific is merged carries out the demodulation equilibrium treatment.

The present invention is based on the energy of two-way received signal level value RSSI (Receive Signal Strength Indicator), Noise Variance Estimation value and channel parameter estimation value and select the merging mode of double antenna received signal adaptively.Best to guarantee that received signal quality arrives.The present invention is under the prerequisite that satisfies the mobile communication system protocol specification, can prevent since in the two-way received signal a certain road noise excessive or since in the double antenna No. one antenna damage influence the quality of whole received signal, the present invention has guaranteed the performance and the stability of baseband system simultaneously.Compatibility of the present invention is good, realization is simple.

Description of drawings

Fig. 1 is the base station receiver structural representation of mobile communication dual-antenna system;

Fig. 2 is a signaling process schematic diagram of the present invention;

Fig. 3 is a conventional burst form schematic diagram in the EDGE communication system;

Fig. 4 is the double antenna 8PSK equalizing demodulation implementation structure schematic diagram of EDGE system.

Embodiment

The present invention is described in further detail below in conjunction with accompanying drawing.

As shown in Figure 1, mobile communication system comprises emission system and receiving system, and receiving system realizes that by dual-antenna system signal receives, and the two-way antenna is sent to band receiver of base with the signal that receives.Band receiver of base is at first by the baseband signal (I of demodulation module to receiving, Q) carrying out diversity merges and demodulation, result after the demodulation is sent to the decoding that the channel decoding module is carried out channel through after the deinterleaving, and then by this signal of decoder decode and obtain the information that the source end sends.

When dual-antenna system receive two paths of signals (I, Q) afterwards, band receiver of base is handled according to the following steps:

1, calculates the energy and and the estimated value of two paths of signals noise variance of level value RSSI, the two-way channel parameter estimation value of two-way received signal respectively.

The present invention can at first calculate the level value RSSI of two-way received signal.The method of calculating RSSI has a lot, more common method be according to the energy of training sequence or pilot frequency sequence part signal with, determine final RSSI according to the method for tabling look-up.

For the energy of two-way channel parameter estimation value and, at first to calculate the channel parameter estimation value of two paths of signals.For the two-way received signal, signal model can be expressed as:

$y_i\left(k\right)=\underset{j=0}{\overset{L-1}{\mathrm{\Σ}}}{f}_i\left(k\right)\·x(k-j)+n_i\left(k\right)$

Y wherein _i(k) be the two-way received signal.I desirable 0 and 1,, represent first via signal with 0, and 1 represents the second road signal here.The signal that x (k) sends for the source end.Comprising training sequence or pilot frequency sequence and Useful Information bit.f _i(k) be synthetic channel parameter, n (k) is a noise.L is the disperse length of channel.

The estimation of channel parameter generally can be adopted maximum Likelihood or the relevant method of sliding.Slip is relevant estimates that the formula of channel parameter is:

$h_i\left(j\right)=\frac{1}{N_h}\underset{k=0}{\overset{N_h-1}{\mathrm{\Σ}}}{y}_i\left(k\right)\·a(k+j)$

H wherein _i(j) be the estimated value of channel parameter, the scope of j is [0, L-1], and a (k) is training sequence or pilot frequency sequence, and N _hFor estimating the channel parameter Len req, be generally less than the length of training sequence or pilot frequency sequence.The energy of two-way channel parameter estimation value and being respectively:

$\mathrm{Energy}\_H0=\underset{j=0}{\overset{L-1}{\mathrm{\Σ}}}{\left|h_0\left(j\right)\right|}^2$

$\mathrm{Energy}\_H1=\underset{j=0}{\overset{L-1}{\mathrm{\Σ}}}{\left|h_1\left(j\right)\right|}^2$

For the noise variance of two paths of signals, can utilize training sequence or pilot frequency sequence to estimate.Concrete grammar is as follows: for i road diversity reception signal, the estimated value of training sequence or pilot frequency sequence and channel parameter is done convolution, corresponding training sequence or pilot frequency sequence partly done mean square deviation in its output result and the actual reception signal, is the noise variance of received signal.If the value of noise variance is smaller, the signal to noise ratio that then reflects this road signal is than higher.The computing formula of the noise variance of signal is:

${\mathrm{\σ}}_i^2=\frac{1}{N_{\mathrm{\σ}}}\underset{k=0}{\overset{N_{\mathrm{\σ}}-1}{\mathrm{\Σ}}}{|y_i\left(k\right)-\underset{j=0}{\overset{L-1}{\mathrm{\Σ}}}{h}_i\left(j\right)\·a(k-j)|}^2$

N wherein _σBe the calculating noise variance Len req, be generally less than the length of training sequence or pilot frequency sequence.

2, coming that according to 3 end values that calculate in the step 1 two paths of signals is carried out self adaptation merges.As shown in Figure 2, set received signal minimum threshold RSSI_Threshold, the RSSI_Threshold value is relevant with real system, in general, can get-120dBm about (121dBm to-119dBm between).At first judge the level value RSSI of two-way received signal and the size of RSSI_Threshold.If the level value that one road signal is arranged, is then given up this road signal less than RSSI_Threshold, carry out selectivity and merge, be about to that road signal greater than RSSI_Threshold as useful signal, carry out the demodulation equilibrium treatment.If the level value RSSI of two paths of signals is less than RSSI_Threshold, then two paths of signals is invalid signals, does not carry out demodulation, and flow process finishes.If the RSSI value of two paths of signals then enters step 3 all greater than RSSI_Threshold.

3, judge the energy of two-way channel parameter estimation value and whether having big difference.Set the energy of two-way channel parameter estimation value and allow maximum multiple difference M (M＞1), in general, the span of M can be between 8～10.If the energy of two-way channel parameter estimation value and the merchant not in mathematical set [1/M, M], then give up the energy of channel parameter estimation value and that little road signal, carry out selectivity and merge.Only adopt the energy of channel parameter estimation value and big signal to carry out the demodulation equilibrium treatment, processing can prevent owing to the excessive received signal total quality that causes of road noise in the two-way received signal is not high like this.If the energy of two-way channel parameter estimation value and the merchant in mathematical set [1/M, M], then enter step 4.

4, set the max-thresholds Noise_Threshold of the Noise Variance Estimation value that guarantees Signal-to-Noise, Noise_Threshold is relevant with real system, generally can get about 1～10.Whether judge the two paths of signals noise variance all less than Noise_Threshold, if then two paths of signals is carried out equal gain combining; Merge otherwise carry out high specific, the energy of the channel parameter estimation value of each road signal and and the ratio of Noise Variance Estimation value as the weight of this road signal in the high specific merge algorithm.Here, equal gain combining is with the adjustment of two paths of signals process same-phase, directly carries out addition then; And high specific to merge be through the same-phase adjustment, with addition again after separately the weight quadrature with two paths of signals.Theoretically, high specific merges the diversity gain that can obtain the best.The equal gain combining computation complexity is low.

As shown in Figure 3, EDGE (Enhanced Data rates for GSM Evolution, the GSM evolution scheme of enhancing data rate) system can provide higher data communication rates.The EDGE system has introduced many level digitals modulation system---the 8PSK modulation.Because the 8PSK modulation is a kind of linear modulation, 3 successive bits are mapped to a symbol of I/Q coordinate, thereby higher bit rate and spectrum efficiency can be provided.Under different channel situation, 9 kinds of different modulation coding modes can be provided---MCS (Modulation and Coding Scheme), wherein MCS1～4 uses remains GMSK modulation mode in the gsm system, is 8PSK modulation mode and use MCS5～9.For conventional burst NB (Normal Burst), its information is divided into two groups of each 58 symbols, and wherein 57 is data, and another one represents that for stealing flag of frame these data are user data or signaling.Between this two segment data, insert 26 training sequence, be used for estimating channel parameter and Timing Advance.The tail bit of 3 " 0 " is added on the both sides of message segment.The NB data time of 8.25 arranged at last, do not send out signal any, as the protection section of adjacent time-slots.NB can be with GMSK or 8PSK modulation signal.

As shown in Figure 4, for the EDGE system, the structure that the present invention realizes is as figure.For every road signal, structure includes signal flip module, channel estimation module, matched filtering module and self adaptation and merges the control variables generation module, and the total self adaptation of two paths of signals merges module and equalizing demodulation module.Digital I, Q signal for the first via and the second tunnel obtains through over-sampling at first will pass through the signal flip module.For the 8PSK signal, adopt e ^{-j3 π k/8}Overturn.Signal after the upset is sent into channel estimation module, according to signal relevant acquisition of sliding after known training sequence and the upset.The channel parameter that estimates is as the input of matched filtering module, carries out matched filtering with signal after the upset.

Self adaptation merges the control variables generation module and mainly calculates above-mentioned 3 end values, the level value RSSI of promptly every road signal, the energy of channel parameter estimation value and and Noise Variance Estimation value.These 3 end values are imported as the control variables that self adaptation merges module, and the output of matched filtering module merges the signal input of module as self adaptation.When the self adaptation in the two paths of signals merges after control variables generates, adopt the above-mentioned method of the present invention to control the mode that the output signal to two-way matched filtering module merges.If selectivity merges, so directly with the output of the matched filtering module in selecteed that road signal input as equalizing demodulation.If equal gain combining, so to the output addition of two-way matched filtering module, then divided by 2, as the input of equalizing demodulation.If high specific merges, so weighting is done in the output of two-way matched filtering module and is merged, weight be each path channels estimates of parameters energy and with the ratio of Noise Variance Estimation value.The output signal that at last self adaptation is merged module is input to the equalizing demodulation module and does the demodulation equilibrium, output useful information bit.

Above-mentioned only is description to preferred embodiment of the present invention, so that those of ordinary skills can use or utilize the present invention.The present invention also can have other various embodiments; under the situation that does not deviate from spirit of the present invention and essence thereof; those skilled in the art work as can make various corresponding changes and distortion according to the present invention, but these corresponding changes and distortion all should belong to the protection range of the appended claim of the present invention.

Claims (5)

1, the adaptive diversity merging method of band receiver of base in a kind of dual-antenna system is characterized in that this method may further comprise the steps:

(1) calculate respectively each road signal that described double antenna receives level value, channel parameter estimation value energy and and the Noise Variance Estimation value;

(2) judge the size of each road received signal level value and setting threshold respectively, if two-way received signal level value all greater than setting threshold, then enters step (3); If one of them is greater than setting threshold, then only keep this greater than one road signal of setting threshold as useful signal, carry out the demodulation equilibrium treatment; If two-way received signal level value is all less than setting threshold, then two paths of signals is invalid signals, and step finishes;

(3) relatively the energy of the channel parameter estimation value of two paths of signals and the merchant whether in setting number range, if, then enter step (4), otherwise keep energy with big channel parameter estimation value and road signal as useful signal, only this useful signal is carried out the demodulation equilibrium treatment;

(4) whether the Noise Variance Estimation value of judging two paths of signals is all less than setting threshold, if then this two paths of signals is carried out equal gain combining, and the signal that these gains are merged carries out the demodulation equilibrium treatment; Otherwise this two paths of signals is carried out high specific to be merged, the energy of the channel parameter estimation value of each road signal and and the ratio of Noise Variance Estimation value as the weight of this road signal in the high specific merge algorithm, and the signal that this high specific is merged carries out the demodulation equilibrium treatment.

2, the adaptive diversity merging method of band receiver of base in the dual-antenna system according to claim 1, it is characterized in that, setting number range in the described step (3) is specially, if the energy of the two channel parameter estimation values of setting and the merchant be M to the maximum, then setting number range is mathematical set [1/M, M].

3, the adaptive diversity merging method of band receiver of base in the dual-antenna system according to claim 1 is characterized in that, described equal gain combining is with the adjustment of two paths of signals process same-phase, directly carries out addition then; It is through the same-phase adjustment, with addition again after separately the weight quadrature with two paths of signals that described high specific merges.

4, the adaptive diversity merging method of band receiver of base in the dual-antenna system according to claim 1 is characterized in that, the setting threshold of described received signal level value can be according to concrete default, at-121dBm between-the 119dBm; The setting threshold of described Noise Variance Estimation value equally can be according to concrete default, and span is mathematical set [1,10].

5, the adaptive diversity merging method of band receiver of base in the dual-antenna system according to claim 2 is characterized in that, described M span is mathematical set [8,10].

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