CN102098114B - Method and device for measuring signal-to-noise ratio of system - Google Patents

Abstract

The invention discloses a method for measuring a signal-to-noise ratio of a channel. The method comprises the following steps of: extracting a Ranging subcarrier sequence which is received from a specified Ranging area from an orthogonal frequency division multiplexing (OFDM) signal received by a transmitting end; performing a correlation operation on the Ranging subcarrier sequence and a pseudo random code sequence generated locally to obtain a corresponding correlation sequence, and computing a power value of each sampling point in the correlation sequence; computing the received signal total power and the effective signal total power aiming at the Ranging subcarrier sequence according to the power value of each sampling point; computing to obtain a noise signal total power according to the obtained received signal total power and the effective signal total power; and obtaining the signal-to-noise ratio of the system according to the effective signal total power and the noise signal total power. Thus, computing resources of the system can be effectively saved, the execution efficiency of the system is improved and the performance of the system is also improved. The invention also discloses a device used for measuring the signal-to-noise ratio of the system.

Description

A kind of method of measuring system signal to noise ratio and device

Technical field

The present invention relates to the communications field, particularly a kind of method of measuring system signal to noise ratio and device.

Background technology

At present, OFDM (Orthogonal Frequency Division Multiplexing, OFDM) technology is strong because of its ability of anti-multipath, and the characteristics such as spectrum utilization efficiency height have been widely used in and have made in the middle of rear 3 generation communication systems.In the wireless communication system based on the OFDM technology, a very crucial technology is adaptive modulation and coding (Adaptive Modulation and Coding) technology, adopt the adaptive modulation and coding technology can be according to channel condition information selecting modulation mode and coded system adaptively, thereby can improve to greatest extent throughput of system, guarantee target frame error rate.And to adopt the adaptive modulation and coding technology, just need to be measured the signal to noise ratio of system.

In the middle of traditional technical scheme, the method usually adopted while carrying out snr measurement is: use the linear channel algorithm for estimating to estimate channel response, after then carrying out channel compensation, then carry out snr measurement according to compensation result.The required operand of this mode is very big, thereby has expended to a certain extent too much system resource, has reduced running efficiency of system, and then affects the entire system performance.

Summary of the invention

The embodiment of the present invention provides a kind of method and device of measuring system signal to noise ratio, in order to when the measuring system signal to noise ratio, saves system resource, improves running efficiency of system.

The concrete technical scheme that the embodiment of the present invention provides is as follows:

A kind of method of measuring the channel signal to noise ratio comprises:

Extract the Ranging subcarrier sequence from specifying access code Ranging zone to receive the orthogonal frequency division multiplex OFDM signal received from transmitting terminal;

Described Ranging subcarrier sequence and the local pseudo-random code sequence generated are carried out to related operation, obtain corresponding correlated series, and calculate the performance number of each sampled point in described correlated series;

Calculate the reception total power signal for described Ranging subcarrier sequence according to the performance number of each sampled point, and filter out the peak value sampling point from each performance number, and calculate the useful signal gross power according to each peak value sampling point;

Calculate the noise signal gross power according to the reception total power signal and the useful signal gross power that obtain, and obtain system signal noise ratio according to this useful signal gross power and noise signal gross power.

A kind of device for the measuring system signal to noise ratio comprises:

Signal processing module, extract the Ranging subcarrier sequence from specifying access code Ranging zone to receive for the orthogonal frequency division multiplex OFDM signal received from transmitting terminal;

Power computation module, for described Ranging subcarrier sequence and the local pseudo-random code sequence generated are carried out to related operation, obtain corresponding correlated series, and calculate the performance number of each sampled point in described correlated series; Calculate the reception total power signal for described Ranging subcarrier sequence according to the performance number of each sampled point, and filter out the peak value sampling point from each performance number, and calculate the useful signal gross power according to each peak value sampling point;

The snr computation module, calculate the noise signal gross power for reception total power signal and useful signal gross power according to obtaining, and obtain system signal noise ratio according to this useful signal gross power and noise signal gross power.

The embodiment of the present invention is used the particularity of pseudo-random code sequence according to each channel in the wireless communication system based on the OFDM technology, performance number by correlated series that Ranging subcarrier sequence and pseudo-random code sequence are carried out obtaining after related operation is analyzed, to obtain required system signal noise ratio.This method, compared to traditional signal-to-noise ratio measuring method based on channel estimating, compensation result, more can effectively be saved the system calculation resources, thereby improves the system execution efficiency, has also promoted systematic function.

The accompanying drawing explanation

Fig. 1 is the communication system architectural framework figure based on the OFDM technology in the embodiment of the present invention;

Fig. 2 is measurement mechanism functional structure chart in the embodiment of the present invention;

Fig. 3 be in the embodiment of the present invention measurement mechanism based on OFDM commercial measurement signal to noise ratio flow chart.

Embodiment

In the wireless communication system based on the OFDM technology, while carrying out the system signal noise ratio measurement, in order effectively to save system resource, in the embodiment of the present invention, extract the Ranging subcarrier sequence from specifying access code (Ranging) zone to receive the ofdm signal received from transmitting terminal; Again described Ranging subcarrier sequence and the local pseudo-random code sequence generated are carried out to related operation, obtain corresponding correlated series, and calculate the performance number of each sampled point in described correlated series; Then, calculate the reception total power signal for described Ranging subcarrier sequence according to the performance number of each sampled point, and filter out the peak value sampling point from each performance number, and calculate the useful signal gross power according to each peak value sampling point; Finally, according to the reception total power signal and the useful signal gross power that obtain, calculate the noise signal gross power, and obtain system signal noise ratio according to this useful signal gross power and noise signal gross power.

Below in conjunction with accompanying drawing, the preferred embodiment of the present invention is elaborated.

Consult shown in Fig. 1, in the embodiment of the present invention, in the wireless communication system based on the OFDM technology, comprise somely for measuring the measurement mechanism of signal to noise ratio, in practical application, measurement mechanism can have multiple example, as, base station, base station controller, back-stage management server etc.In the present embodiment, wireless communication system based on the OFDM technology adopts the 802.16e standard, intrasystem each transmitting terminal (as, client) use the pseudo-random code sequence that length is 144, use the pseudo-random code sequence that comprises 144 modulation symbols (positive and negative 1), on data-mapping to 144 subcarrier (also referred to as the Ranging zone) that needs are sent, convert and will send data and be converted to time-domain signal by IFFT again, and obtain final base band time domain signal by sewing before and after adding, and it is mail to network side.So, the measurement mechanism of network side just can be measured system signal noise ratio according to the above-mentioned time-domain signal received.

Consult shown in Fig. 2, in the embodiment of the present invention, above-mentioned measurement mechanism comprises signal processing module 10, access code detection module 11 (also referred to as Ranging detection module 11) and snr value computing module 12, wherein,

Signal processing module 19, for the reception signal of acquisition is gone to prefix process, carry out again fast Fourier (FFT) conversion and obtain frequency domain data in a signal length, and therefrom extract client by specifying the Ranging zone to send the subcarrier sequence of coming up;

As shown in Figure 2, interior prefix unit, FFT unit and the Ranging subcarrier extraction unit of specifically comprising of signal processing module 10, wherein,

Go to the prefix unit, for the data to receiving, gone prefix process, generate time domain data;

The FFT unit, convert frequency domain data X (k) to for the time domain data x (t) by after processing;

Ranging subcarrier extraction unit, for the subcarrier from all, the ranging subcarrier sequence that will receive from the ranging zone extracts according to the transmitting site of known transmitter, and other positions fill out 0;

Power computation module 11, carry out related operation for the Ranging subcarrier sequence by extracting and the local pseudo-random code sequence generated, and obtains corresponding correlated series, and calculate the performance number of each sampled point in described correlated series; Calculate the reception total power signal for described Ranging subcarrier sequence according to the performance number of each sampled point, and filter out the peak value sampling point from each performance number, and calculate the useful signal gross power according to each peak value sampling point; Be specially: power computation module 11 searches out peak value, obtains peak power and peak from the Ranging subcarrier sequence extracted, and the gross power (being called received signal power) that obtains above-mentioned Ranging subcarrier sequence according to peak power, and useful signal gross power and noise signal gross power; On the other hand, power computation module 11, also for above-mentioned Ranging subcarrier sequence is carried out to Rang subcarrier sequence, carry out the detection of Ranging code, if detect the Ranging code, in Output rusults, comprise Ranging code, Ranging code type, peak power, peak, average power.

As shown in Figure 2, described power computation module 11 specifically comprises following unit:

The local code generation unit, for generation of local pseudo-random code sequence C (k), the Ranging code that to comprise length that some clients may be used in C (k) be 144;

The first multiplier, for local pseudo random sequence C (k) is carried out to related operation with the Ranging subcarrier sequence received, for example, conjugate multiplication;

The IFFT unit, change into time domain data for the frequency domain data by the first multiplier output, obtains time domain data rr (x);

The mould squaring cell, ask the side's of touching computing for realizing time domain data rr (x), the real part of rr (x) data and imaginary part asked respectively and square sued for peace again, thereby obtain the performance number of each sampled point;

The maximum value search unit, for maximum (being peak value) and the peaked position of searching for each sampled point;

Accumulator, for obtaining the gross power of Ranging subcarrier sequence, also referred to as receiving total power signal;

Peak value sample points search unit, the part that surpasses average power for finding out performance number reaches the sampled point of setting threshold, its power is also referred to as the peak value sampling point, and these peak value sampling points are exactly the power of multipath signal, more just can calculate the useful signal gross power according to these peak value sampling points;

Cumulative unit, for calculating the useful signal gross power;

Subtract each other unit, tried to achieve reception total power signal is deducted to the useful signal gross power, thereby obtain the noise signal gross power;

In addition, as shown in Figure 2, also comprise the second multiplier and comparator in power computation module 11,

The second multiplier, be multiplied by threshold operation for realizing average, obtains average power threshold doubly;

Comparator, the average power threshold of exporting for maximum that the maximum value search unit is tried to achieve and the second multiplier doubly compares, if the maximum power ratio average power threshold is doubly large, now think and a Ranging code detected, the maximum value position obtained in conjunction with the maximum value search unit, just can obtain the time adjusted value of Ranging code;

In the present embodiment, the second multiplier and comparator only just can be used when detecting the Ranging code.

Snr computation unit 12, calculate the noise signal gross power for reception total power signal and useful signal gross power according to obtaining, and obtain system signal noise ratio (SNR) according to this useful signal gross power and noise signal gross power, as shown in Figure 2, comprise and be averaging unit and divider, wherein

Be averaging unit, for receiving total power signal and the useful signal gross power is averaging respectively computing, divider is for obtaining the SNR value by the useful signal average power divided by the noise signal average power.

Based on the said system framework, in the embodiment of the present invention, the summary step that measurement mechanism is measured the signal to noise ratio of channel in system is as follows:

Steps A: adopt the spectrum correlation method to carry out the access code detection for channel, utilize the access code peak power detected, estimate the gross power that receives signal.

In Channel Detection, usually use the mode of the matched filtering based on the spectrum correlation method to detect, in order to reduce the operand of matched filtering, in the present invention, the operation of measurement mechanism detection access code peak power is transformed into frequency domain by the related operation by matched filter, and multiplies each other to realize with local reference sequences; Accordingly, steps A can be further subdivided into following step:

Steps A 1: the ofdm signal received is gone to carry out the FFT computing after prefix, thereby time-domain signal is transformed into to frequency-region signal Rx (k).

Steps A 2: extract the related operation that Ranging subcarrier sequence and the local pseudo-random code sequence generated carry out sequence from Rx (k), obtain new sequence Rr (k).

Steps A 3: sequence Rr (k) is carried out to inverse fast Fourier transform (IFFT) computing, obtain sequence rr (N).

Steps A 4: average the calculating of power and peak power for sequence rr (N), obtain and receive total power signal, average power, peak power and peak.

Step B: the peak power that steps A is calculated, with average power, compare, to reach the peak power of setting threshold as the peak value sampling point over average power, try to achieve the useful signal gross power by cumulative peak value sampling point computing again, then deduct the useful signal gross power and estimate the noise signal gross power by receiving total power signal.

Step C: respectively useful signal gross power and noise signal gross power are averaged, obtain useful signal average power and noise signal average power, then both are carried out to the signal to noise ratio that division arithmetic tries to achieve channel.

To achieve these goals, below take a concrete implementing procedure describes as example.Consult shown in Fig. 3, in the embodiment of the present invention, measurement mechanism is from channel receives the ofdm signal that end side sends, and the detailed process of system signal noise ratio being measured according to this ofdm signal is as follows:

Step 300: after the ofdm signal received is gone to prefix process, then carry out the FFT conversion, obtain frequency-region signal Rx (k).Specifically can be expressed as formula 1:

$\mathrm{Rx}\left(k\right)=X\left(k\right)\·\underset{p=0}{\overset{P}{\mathrm{\Σ}}}{H}_p\left(k\right)\·e^{j\frac{2\mathrm{\π\Δ}{n}_p\·k}{N}}+N\left(k\right)$ Formula 1

Wherein:

X (k): the frequency domain transmitted signal of some code vectors on k carrier wave, k is natural number;

Δ n _p: the timing offset of p multipath, p is natural number;

Hp (k): the frequency response of k channel, k is natural number;

N (k): noise signal sequence;

N is total number of sub-carriers;

P: multipath number.

Same under each meaning of parameters, repeat no more.

Step 310: extract the Ranging subcarrier sequence received from the Ranging zone from Rx (k), and this Ranging subcarrier sequence and the local pseudo-random code sequence C (k) generated are carried out to related operation (as conjugate multiplication), obtain one group of correlated series Rr (k).Specifically can be expressed as formula 2

$\mathrm{Rr}\left(k\right)=X\left(k\right)\·C\left(k\right)\underset{p=0}{\overset{P}{\mathrm{\Σ}}}{H}_p\left(k\right)\·e^{j\frac{2\mathrm{\π\Δ}{n}_p\·k}{N}}+N\left(k\right)$ Formula 2

Wherein, C (k) is the local pseudo-random code sequence generated, and is modulated to positive and negative 1.

Step 320: the correlated series Rr (k) obtained is carried out to the IFFT computing, obtain time-domain signal, be called sequence rr (m).Specifically can be expressed as formula 3:

$\mathrm{rr}\left(n\right)=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}(X\left(k\right)\·C\left(k\right)\underset{p=0}{\overset{P}{\mathrm{\Σ}}}{H}_p\left(k\right)\·e^{j\frac{2\mathrm{\π\Δ}{n}_p\·k}{N}}+N\left(k\right))\·e^{j\frac{-2\mathrm{\πnk}}{N}}$ Formula 3

Step 330: rr (n) is carried out to the peak value detection, calculate the performance number of each sampled point in Ranging subcarrier sequence.Specifically can be expressed as formula 4:

By to rr (m), asking mould side to calculate the performance number of each sampled point, be specially:

$P_{\mathrm{rr}}\left(n\right)={|\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}(X\left(k\right)\·C\left(k\right)\underset{p=0}{\overset{P}{\mathrm{\Σ}}}{H}_p\left(k\right)\·e^{j\frac{2\mathrm{\π\Δ}{n}_p\·k}{N}})\·e^{j\frac{-2\mathrm{\πnk}}{N}}+\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}N\left(k\right)\·e^{j\frac{-2\mathrm{\πnk}}{N}}|}^2$ Formula 4

Step 340: determine peak power and the peak of each sampled point, and the peak power of each sampled point and setting threshold are compared, will be greater than the peak value sampling point of the peak power of setting threshold as Prr (n).

Can be analyzed and be drawn by formula 4, in the time of X (k) and local pseudo random sequence code C (k) coupling, sequence Prr (n) is at n=Δ n _pPosition there will be a very large peak value; And at X (k) and local pseudo random sequence code C (k) unmatched the time because the their cross correlation of pseudo random sequence C (k), now Prr (n) relatively with not there will be larger peak value.According to this characteristic, can detect in Prr (n) sequence whether have the peak power that is greater than setting threshold, wherein, described setting threshold is relevant to Prr (n) sequence length, can confirm by emulation; If there is the peak power that is greater than setting threshold, just think and an access sequence detected, wherein, each peak value is exactly a multipath of an access sequence.

Step 350: selected peak value sampling point is added up, to obtain the useful signal gross power.

Can infer from formula 4, be greater than the point of setting threshold for peak power in the middle of Prr (n) sequence, its energy and, the useful signal gross power can specifically be expressed as formula 5:

$\mathrm{Ps}\≈\underset{p=0}{\overset{P}{\mathrm{\Σ}}}{\left|P_{\mathrm{rr}}\left(\mathrm{\Δ}{n}_p\right)\right|}^2\≈\underset{p=0}{\overset{P}{\mathrm{\Σ}}}{\left|\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{H}_p\left(k\right)\right|}^2$ Formula 5

Formula 5 is exactly multipath signal, i.e. the expression formula of useful signal gross power.Prr (n) is at n=Δ n _pPosition there will be a very large peak value, and the position energy of peak value is just in time the energy of useful signal.

Step 360: calculate and receive total power signal, the i.e. gross power of Ranging subcarrier sequence.Step 360 also can be carried out before step 340, first calculated and received total power signal, then calculate the useful signal gross power.

Because local pseudo-random code sequence C (k) modulation symbol of measurement mechanism is positive and negative 1, therefore with Ranging subcarrier sequence, to carry out the power of the correlated series that obtains after related operation constant, equals the power of Ranging subcarrier sequence; And the IFFT conversion that frequency-region signal transfers time-domain signal to can not changed to the performance number of signal, and therefore, the gross power of Prr (n) and receive total power signal and equate, thus the gross power of Ranging subcarrier sequence can specifically be expressed as formula 6:

$P_a=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}{P}_{\mathrm{rr}}\left(n\right)$ Formula 6

Step 370: according to the reception total power signal and the useful signal gross power that obtain, calculate the gross power of noise signal.

In the present embodiment, the noise signal gross power can specifically be expressed as formula 7:

P _N=P _a-P _sFormula 7

Step 380: according to noise signal gross power and useful signal gross power, calculate signal to noise ratio snr.

In the present embodiment, signal to noise ratio can specifically be expressed as formula 8:

SNR=Ps/Pn formula 8

Before carrying out above-mentioned steps 340-380/simultaneously/afterwards, can be according to the result of calculation of Prr (n), further obtain the average power of each sampled point, again by the wherein maximum peak power comparison of the sum of products of average power and threshold value, if the power product is less than peak power value, determine and the Ranging code detected, carry user data in the Ranging subcarrier sequence that illustrative system receives, now, need to be reported calculating the system signal noise ratio obtained in step 380, so that follow-up management; If the power product is not less than peak power value, determine and the Ranging code do not detected, now, do not need to calculate in step 380 system signal noise ratio obtained and reported and detect unsuccessfully.

In sum, in the embodiment of the present invention, the performance number analysis by the Ranging subcarrier sequence to the reception of Ranging zone, can obtain system signal noise ratio.Compared to traditional signal-to-noise ratio measuring method based on channel estimating, compensation result, the method that the present embodiment provides more can effectively be saved the system calculation resources, thereby improves the system execution efficiency, has also promoted systematic function.

Obviously, those skilled in the art can carry out various changes and modification and not break away from the spirit and scope of the present invention the embodiment in the present invention.Like this, if within these in the embodiment of the present invention are revised and modification belongs to the scope of the claims in the present invention and equivalent technologies thereof, the embodiment in the present invention also is intended to comprise these changes and modification interior.

Claims (10)

1. a method of measuring the channel signal to noise ratio, is characterized in that, comprising:

Extract the Ranging subcarrier sequence from specifying access code Ranging zone to receive the orthogonal frequency division multiplex OFDM signal received from transmitting terminal;

Described Ranging subcarrier sequence and the local pseudo-random code sequence generated are carried out to related operation, obtain corresponding correlated series, and calculate the performance number of each sampled point in described correlated series;

Calculate the reception total power signal for described Ranging subcarrier sequence according to the performance number of each sampled point, and filter out the peak value sampling point from each performance number, and calculate the useful signal gross power according to each peak value sampling point;

Calculate the noise signal gross power according to the reception total power signal and the useful signal gross power that obtain, and obtain system signal noise ratio according to this useful signal gross power and noise signal gross power.

2. the method for claim 1, is characterized in that, adopts formula $\mathrm{Rr}\left(k\right)=X\left(k\right)\·C\left(k\right)\underset{p=0}{\overset{P}{\mathrm{\Σ}}}{H}_p\left(k\right)\·e^{j\frac{2\mathrm{\π\Δ}{n}_p\·k}{N}}+N\left(k\right)$ Carry out described related operation; Wherein, Rr (k) is for carrying out the correlated series obtained after related operation, and X (k) is the frequency domain transmitted signal of some code vectors on k carrier wave, and k is natural number, Δ n _pBe the timing offset of p multipath, p is natural number, Hp (k): be the frequency response of k channel, N (k) is the noise signal sequence, and P is the multipath number, and N is total number of sub-carriers.

3. method as claimed in claim 2, is characterized in that, described according to formula $P_{\mathrm{rr}}\left(n\right)={|\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}(X\left(k\right)\·C\left(k\right)\underset{p=0}{\overset{P}{\mathrm{\Σ}}}{H}_p\left(k\right)\·e^{j\frac{2\mathrm{\π\Δ}{n}_p\·k}{N}})\·e^{j\frac{-2\mathrm{\πnk}}{N}}+\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}N\left(k\right)\·e^{j\frac{-2\mathrm{\πnk}}{N}}|}^2$ Calculate the performance number of each sampled point.

4. method as claimed in claim 3, is characterized in that, adopts formula $P_a=\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}{P}_{\mathrm{rr}}\left(n\right)$ Calculate described reception total power signal.

5. method as claimed in claim 3, is characterized in that, adopts $P_S\≈\underset{p=0}{\overset{P}{\mathrm{\Σ}}}{\left|P_{\mathrm{rr}}\left({\mathrm{\Δn}}_p\right)\right|}^2\≈\underset{p=0}{\overset{P}{\mathrm{\Σ}}}{\left|\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{H}_p\left(k\right)\right|}^2$ Calculate described useful signal gross power.

6. as the described method of claim 1-5 any one, it is characterized in that, after the performance number of each sampled point, further comprise in calculating described correlated series:

Obtain the average power of each sampled point, then the peak power of the sum of products appointment of average power and threshold value is compared, obtain comparative result.

7. method as claimed in claim 6, it is characterized in that, after obtaining system signal noise ratio, while according to described comparative result, knowing that the product of average power and threshold value is less than the peak power of appointment, determine and the Ranging code detected, and described system signal noise ratio is reported.

8. the device for the measuring system signal to noise ratio, is characterized in that, comprising:

Signal processing module, extract the Ranging subcarrier sequence from specifying access code Ranging zone to receive for the orthogonal frequency division multiplex OFDM signal received from transmitting terminal;

Power computation module, for described Ranging subcarrier sequence and the local pseudo-random code sequence generated are carried out to related operation, obtain corresponding correlated series, and calculate the performance number of each sampled point in described correlated series; Calculate the reception total power signal for described Ranging subcarrier sequence according to the performance number of each sampled point, and filter out the peak value sampling point from each performance number, and calculate the useful signal gross power according to each peak value sampling point;

The snr computation module, calculate the noise signal gross power for reception total power signal and useful signal gross power according to obtaining, and obtain system signal noise ratio according to this useful signal gross power and noise signal gross power.

9. device as claimed in claim 8, it is characterized in that, after the performance number of described power computation module each sampled point in calculating described correlated series, obtain the average power of each sampled point, again the peak power of the sum of products appointment of average power and threshold value is compared, obtain comparative result.

10. device as claimed in claim 9, it is characterized in that, after described snr computation module obtains system signal noise ratio, when the comparative result obtained according to described power computation module knows that the product of average power and threshold value is less than the peak power of appointment, determine and the Ranging code detected, and described system signal noise ratio is reported.

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