CN1194562C - Apparatus and method for estimating burst signal signal-to-noise ratio in GSM base station - Google Patents

Abstract

The present invention discloses a device and a method thereof for estimating the signal-to-noise ratios of burst signals of a base station of a global mobile communication system. The device comprises a receiver, a demodulator and a decoder, wherein the receiver receives signals from a wireless port, and the signals form figurative baseband burst signals after frequency conversion and filtration; after the signals are output to the demodulator, judgment data is generated, and then, the signals are output to the decoder. The device is characterized in that the device also comprises a signal-to-noise ratio estimating module; the input end of the signal-to-noise ratio estimating module inputs the baseband burst signals, and the output end of the signal-to-noise ratio estimating module output signal-to-noise ratio signals; the baseband burst signals and the signal-to-noise ratio signals are combined and input to the demodulator and the decoder; the demodulator simultaneously receives the baseband burst signals and the signal-to-noise ratio signals, and the judgment data is generated after the baseband burst signals and the signal-to-noise ratio signals are demodulated; the judgment data and the signal-to-noise ratio signals are transmitted to the decoder together to obtain decoding results. The method uses the receiver of the base station to receives the burst signals and known training sequences, and the ratios of the signal energy of the burst signals to the noise energy of the burst signals are calculated through a novel method, namely the signal-to-noise ratios. The present invention has the advantages of simple and effective method, little operation amount and accurate calculation.

Description

Apparatus and method for estimating burst signal signal-to-noise ratio in GSM base station

technical field

The invention relates to a device and method for estimating the signal-to-noise ratio of a burst signal in a base station in a global mobile communication (GSM) system.

technical background

The GSM system is a widely used mobile communication system and is a typical time division multiple access system. In this system, the signal transmitted in the air is divided into a period of time and a period of time according to equal time units. In the GSM system, a segment of signal divided into the smallest time unit is called a burst. The burst signal also becomes the smallest unit for the base station or mobile phone to demodulate and decode the air signal.

There are five types of bursts. The most common normal burst is 577 microseconds long, which is divided into 156.25 bit time domains, labeled 0-156. Its structure is shown in the following table: bit number Domain head content 0-2 3 tail bit 3-41 39 information bit 42 -105 64 training sequence 106 -144 39 information bit 145 -147 3 tail bit 148 -156 8,25 view bits

Among them, the training bits are known to the base station, and the information bits are the targets that the base station tries to demodulate.

Wireless channels are very complex. Because the radio wave transmission environment changes with the position of the vehicle and the movement of the vehicle relative to the base station, time-varying fading occurs, and the multipath delay makes the intersymbol interference in the GSM system very serious; moreover, the interference of various electromagnetic waves in the air and Electromagnetic noise, as well as physical noise generated in the base station receiver, all make it very difficult and important for the base station to demodulate and decode burst signals.

Among the burst signal demodulation techniques adopted by general base stations, conventional equalized demodulation techniques are adopted. As shown in FIG. 1 , FIG. 1 is a schematic structural diagram of the modulation and decoding of a conventional base station, including: a receiver 11 , a demodulator 12 and a decoder 13 . The receiver receives the signal from the wireless port, and after frequency conversion and filtering, a digital baseband burst signal is formed. The signal is output to the demodulator to generate judgment data, and then sent to the decoder to output the decoding result. The advantage of this technology is that it can directly demodulate the effective signal in the burst signal through the equalization technology. However, this demodulation technology does not evaluate the quality of the current burst signal, and does not use this information to perform possible performance enhancement on burst signal demodulation. Although the bit error rate of a speech frame can be calculated through the decoding step, since a speech frame contains 8 burst signals, the quality of a single burst signal cannot be evaluated.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings that the existing base station demodulation technology does not evaluate the quality of the current burst signal, and does not use this information to perform possible performance enhancement on the demodulation of the burst signal, and proposes a method using The signal-to-noise ratio of each burst signal can evaluate the quality of each burst signal, and the demodulation and decoding can use the signal-to-noise ratio of the burst signal to improve the algorithm, which can further improve the demodulation of the received signal by the base station A device and method for estimating the signal-to-noise ratio of a burst signal in a global system for mobile communication base station with decoding capability.

In order to achieve the above object, the technical solution adopted by the present invention is: the device for estimating the SNR of the burst signal at the base station of the global mobile communication system, including: a receiver, a demodulator and a decoder, and the receiver receives the signal from the wireless port. The signal, after frequency conversion and filtering, forms a digital baseband burst signal, which is output to the demodulator to generate decision data, and then output to the decoder; it is characterized in that it also includes a signal-to-noise ratio estimation module, Its input terminal inputs the baseband burst signal, and its output terminal outputs the signal-to-noise ratio signal, which is input to the demodulator and decoder respectively. The demodulator simultaneously receives the baseband burst signal and the signal-to-noise ratio signal and generates decision data after demodulation. , the decision data is sent to the decoder together with the signal-to-noise ratio signal to obtain the decoding result.

The above-mentioned device for estimating the SNR of a burst signal at a base station of the Global System for Mobile Communications, wherein the SNR estimation module includes a first correlator module, a second correlator module, a first mean squarer module, a The second mean squarer module, a subtractor module, and a divider module; the baseband burst signal output by the receiver is sent to the first correlator module and the subtractor module at the same time, and the training sequence is also sent to the first correlation output to the second correlator module after correlation calculation by the first correlator module, and the training sequence is also sent to the second correlator module; the effective signal part is divided into two outputs after the correlation calculation by the second correlator module , one output to the first mean squarer module, and the other to the subtractor; the baseband burst signal and the effective signal part are subtracted by the subtracter module to obtain the noise part and output to the second mean squarer module; the first mean squarer module The signal energy output by the squarer module and the noise energy output by the second mean squarer module are divided in the divider module to obtain the signal-to-noise ratio.

The above-mentioned method for estimating the SNR of a burst signal by the base station of the Global System for Mobile Communications estimates the SNR of the burst signal, wherein, each burst signal is evaluated separately for signal quality, and each burst signal and the burst signal The effective signal part and the noise part in the burst signal are separated by the direct relationship of the known training sequence of the signal, so as to calculate the signal-to-noise ratio of the burst signal.

The method for estimating the burst signal-to-noise ratio of the above-mentioned GSM base station is characterized in that the method further includes the following steps:

A, the burst signal and the known training sequence are carried out correlation calculation in the first correlator module of channel parameter estimation module, obtain the channel parameter of the wireless channel that this burst signal passes through in the air;

b. Perform a second correlation calculation in the second correlator module with the training sequence and the channel parameters calculated in the previous step to obtain an effective signal part in the burst signal;

c. Calculate the average energy of the signal part through the mean squarer;

d. At the same time, the burst signal and the effective signal part are subtracted by the subtractor module to obtain the noise part in the burst signal;

e, calculate the average energy of the noise part by the second mean squarer module;

f. The average energy of the signal part and the average energy of the noise part are divided by the divider module to obtain the signal-to-noise ratio of the burst signal.

Since the present invention adopts the above calculation measures, the burst signal received by the receiver of the base station and the known training sequence are used to calculate the signal energy and noise energy of the burst signal through a signal-to-noise ratio channel estimation module Therefore, the calculation amount is small and the calculation is accurate.

Description of drawings

The specific characteristic performance of the present invention is further described by the following examples and accompanying drawings.

FIG. 1 is a schematic diagram of a demodulation technology structure of a conventional base station.

FIG. 2 is a schematic structural diagram of a device for estimating the SNR of a burst signal at a GSM base station according to the present invention.

FIG. 3 is a schematic structural diagram of the signal-to-noise ratio estimation module in FIG. 2 .

Fig. 4 is a flow chart of the SNR estimation method of the present invention.

Detailed ways

The invention uses the direct relationship between the burst signal and the known training sequence to separate the effective signal part and the noise part in the burst signal, so as to calculate the signal-to-noise ratio of the burst signal.

See Figure 2. The device for estimating the signal-to-noise ratio of the burst signal at the base station of the global mobile communication system of the present invention includes: a receiver 21, a demodulator 22 and a decoder 23, and also includes a signal-to-noise ratio estimation module 24; After receiving the signal at the port, after frequency conversion and filtering, a digital form of the baseband burst signal is formed. The signal is represented by a series of digital symbols, and each digital symbol is a complex number, which includes two parts, the real part and the imaginary part. . The training sequence is composed of 26 fixed +1 and -1, and the training sequence is known to the base station, as mentioned above. The baseband burst signal is sent to the input terminal of the SNR estimation module and the demodulator module respectively, and the SNR estimation module outputs the SNR signal and inputs it to the demodulator and decoder respectively, and the demodulator simultaneously receives the baseband The burst signal and the signal-to-noise ratio signal are demodulated to generate decision data, which are sent to the decoder together with the signal-to-noise ratio signal to obtain the decoding result.

See Figure 3. The SNR estimation module of the present invention includes a first correlator module 242, a second correlator module 243, a first mean squarer module 244, a second mean squarer module 245, and a subtractor module 246 , and a divider module 247; the baseband burst signal output by the receiver 21 is delivered to the first correlator module 242 and the subtractor module 246 simultaneously, and the training sequence is also delivered to the first correlator module 242 simultaneously; The correlator module 242 is output to the second correlator module 243 after the correlation calculation, and the training sequence is also sent to the second correlator module 243 simultaneously; Output to the first mean squarer module 244, another way to the subtractor 246; After the subtracter module 246 subtracts the baseband burst signal and the effective signal part, the noise part is output to the second mean squarer module 245; by the second mean squarer module 245; The signal energy output by the first mean squarer module 244 and the noise energy output by the second mean squarer module 245 are divided in the divider 247 module to obtain the signal-to-noise ratio.

The method for estimating the signal-to-noise ratio of the burst signal by the base station of the global mobile communication system of the present invention, through the direct relationship between the burst signal and the known training sequence, separates the effective signal part and the noise part in the burst signal, thereby calculating the burst signal The signal-to-noise ratio of the signal.

See also Fig. 4, the inventive method comprises the following steps:

A, the burst signal and the known training sequence are carried out correlation calculation in the first correlator module of channel parameter estimation module, obtain the channel parameter of the wireless channel that this burst signal passes through in the air;

b. Perform a second correlation calculation in the second correlator module with the training sequence and the channel parameters calculated in the previous step to obtain an effective signal part in the burst signal;

c. Calculating the average energy of the effective signal part through the mean squarer, which is the average energy of the effective signal part;

d. At the same time, the burst signal and the effective signal part are subtracted by the subtractor module to obtain the noise part in the burst signal;

E, calculate the average energy of the noise part by the second mean squarer module, this energy is the average energy of the noise part;

f. The average energy of the signal part and the average energy of the noise part are divided by the divider module to obtain the signal-to-noise ratio of the burst signal.

The invention can estimate the signal-to-noise ratio of the uplink burst signal by the GSM base station, can also be used for estimating the signal-to-noise ratio of the downlink burst signal by the mobile phone, and can be used in other types of wireless systems.

Claims (4)

1, the device of base station in GPS system estimating burst Signal-to-Noise, comprise: receiver, demodulator and decoder, receiver receives signal from wireless mouth, after frequency conversion and filtering, formed the base band burst of digital form, this signal generates the judgement data after outputing to demodulator, outputs to decoder again; It is characterized in that, also comprise a signal-to-noise ratio (SNR) estimation module, its input input base band burst, its output output signal-to-noise ratio signal also is input to demodulator and decoder respectively, demodulator receives the base band burst simultaneously and signal-noise ratio signal generates the judgement data after demodulation, these judgement data are delivered to decoder with signal-noise ratio signal, obtain decode results.

2, the device of base station in GPS system estimating burst Signal-to-Noise according to claim 1, it is characterized in that described signal-to-noise ratio (SNR) estimation module comprises one first correlator block, one second correlator block, one first all square device module, one second all square device module, a subtracter block and a divider module; Base band burst by receiver output is delivered to first correlator block and subtracter block simultaneously, and training sequence is also delivered to first correlator block simultaneously; Output to second correlator block after the first correlator block correlation computations, training sequence is also delivered to second correlator block simultaneously; Obtain useful signal and partly divide two-way output after second correlator block is carried out correlation computations, the one tunnel outputs to the first all square device module, and another road is to subtracter; After subtracter block is partly subtracted each other base band burst and useful signal, obtain noise section and output to the second all square device module; Noise energy by all square device module output of the signal energy and second of the first all square device module output is divided by in divider module, obtains signal to noise ratio.

3, a kind of base station in GPS system estimating burst Signal-to-Noise device according to claim 1 carries out the method for burst signal-to-noise ratio (SNR) estimation, it is characterized in that, each burst is carried out the assessment of independent signal quality, directly concern by each burst and the known training sequence of this burst, isolate effective signal section and noise section in this burst, thereby calculate the signal to noise ratio of this burst.

4, the method for base station in GPS system estimating burst Signal-to-Noise according to claim 3 is characterized in that, this method further may further comprise the steps:

A, burst and known training sequence are carried out correlation computations in first correlator block of channel parameter estimation module, obtain this burst aloft the channel parameter of wireless channel of process;

B, with training sequence with go up the channel parameter that the step calculates and in second correlator block, carry out correlation computations second time, obtain effective signal section in this burst;

C, calculate the average energy of this signal section by equal square devices;

D, simultaneously by subtracter block with burst and effectively signal section subtract each other, obtain the noise section in the burst;

E, by the average energy of second all square device module calculating noise part;

F, by divider module the average energy of signal section and the average energy of noise section are divided by again, obtain the signal to noise ratio of this burst.