CN102118229B - Gsm communication system FACCH steals method and the device of frame detection - Google Patents

Abstract

The invention provides method and device that a kind of gsm communication system FACCH steals frame detection, can solve in prior art and steal the higher problem of frame detection error rate.Gsm communication system FACCH steals the method that frame detects, and comprises the following steps: demodulation burst, obtains the soft bit information that happens suddenly; Summation is weighted according to the burst soft bit information that the corresponding frame identification steathily of FACCH transmission is bit 1 position; The result of weighted sum and the frame judging threshold of stealing preset are compared, judges whether that there is FACCH steals frame.The inventive system comprises demodulation module, computing module, multilevel iudge module in addition.Method of the present invention and device, owing to have employed weighted sum process to soft bit information, effectively improve the resistivity to channel distortions and noise, drastically increases the accuracy that FACCH steals frame detection.

Description

Gsm communication system FACCH steals method and the device of frame detection

Technical field

The present invention relates to mobile communication technology field, particularly in a kind of gsm communication system, FACCH steals method and the device of frame detection.

Background technology

GSM (Global Systems for Mobile Communications, global system for mobile communications) is second generation mobile communication system.FACCH (Fast Associated Control Channel in gsm communication system, Fast Associated Control Channel) use TCH (Traffic Channel when transmitting, Traffic Channel) physical channel transmission, and the data that former TCH steals in frame are destroyed, in order to resolved detection FACCH and TCH, introduce frame identification (Stealing flag) steathily and distinguish channel, need, at receiving terminal, frame is steathily carried out to FACCH and TCH channel for this reason and detect identification.

Steal in frame detection scheme existing, add up to adjudicate whether there is frame steathily by gains such as soft bit informations.Adopt this frame detection method steathily, owing to not considering that detection is easily subject to the impact of channel distortions and noise jamming, when channel circumstance change is very fast or channel circumstance is more severe, frame detection error rate is higher steathily.Therefore, gsm communication system needs the more reliable FACCH of one to steal frame detection method.

Summary of the invention

For solving the problem, the invention provides method and device that a kind of gsm communication system FACCH steals frame detection, the accuracy that FACCH steals frame detection can be improved.

Gsm communication system FACCH steals the method that frame detects, and comprises the following steps:

Demodulation burst, obtains the soft bit information that happens suddenly;

Steal according to FACCH transmission is corresponding the burst soft bit information that frame identification is bit 1 position, adopt following formula to be weighted summation:

In formula, y is for stealing framing bit soft bit information combined value, r _ifor described burst soft bit information, P _ifor available power, N _ifor noise power;

The result of weighted sum and the frame judging threshold of stealing preset are compared, judges whether that there is FACCH steals frame.

The present invention also provides a kind of gsm communication system FACCH to steal the device of frame detection in addition, comprising:

Demodulation module, for demodulation burst, obtains the soft bit information that happens suddenly;

The computing module be connected with described demodulation module, for stealing according to FACCH transmission is corresponding the burst soft bit information that frame identification is bit 1 position, adopts following formula to be weighted summation:

$y=\underset{i=1}{\overset{8}{\mathrm{\Σ}}}{r}_i\·\frac{\sqrt{P_i}}{N_i};$

In formula, y is for stealing framing bit soft bit information combined value, r _ifor described burst soft bit information, P _ifor available power, N _ifor noise power;

The multilevel iudge module be connected with described computing module, for the result of the weighted sum exported in described computing module and the frame judging threshold of stealing preset being compared, judges whether that there is FACCH steals frame.

As can be seen from above scheme, a kind of gsm communication system FACCH of the present invention steals method and the device of frame detection, owing to have employed weighting process to soft bit information, effectively improve the resistivity to channel distortions and noise, drastically increase the accuracy that FACCH steals frame detection.

Accompanying drawing explanation

Fig. 1 is the method flow diagram that gsm communication system FACCH of the present invention steals frame detection;

Fig. 2 is the apparatus structure schematic diagram that gsm communication system FACCH of the present invention steals frame detection;

Fig. 3 is that FACCH/F of the present invention steals frame identification bit information figure;

Fig. 4 is that FACCH/H of the present invention steals frame identification bit information figure.

Embodiment

The invention provides method and device that a kind of gsm communication system FACCH steals frame detection, can solve in prior art and steal the higher problem of frame detection error rate.

As shown in Figure 1, gsm communication system FACCH of the present invention steals the method that frame detects, and comprises the following steps:

Step S1, demodulation burst, obtains the soft bit information that happens suddenly.

Above-mentioned demodulation burst, after can adopting soft output Viterbi algorithm (SOVA) or being with likelihood, the viterbi algorithm (VALPP) of level processor, carries out demodulation to burst.

Step S2, is weighted summation according to the burst soft bit information that the corresponding frame identification steathily of FACCH transmission is bit 1 position.

According to GSM05.02 agreement, extraction FACCH channel may transmit in the transmission burst of corresponding successive frame steals the demodulation Soft Inform ation r that frame identification is bit 1 position _i, i=1 ~ 8, are weighted summation process to the soft bit information after demodulation, can adopt following formula:

$y=\underset{i=1}{\overset{8}{\mathrm{\Σ}}}{r}_i\·\frac{\sqrt{P_i}}{N_i}$

In formula, y is the result of weighted sum, is also called framing bit soft bit information combined value steathily, r _ifor described burst soft bit information, P _ifor available power, N _ifor noise power.

Wherein, by P _iand N _icalculate value is also called currently respectively may steal the weighted value that frame identification is bit 1 position, P _ifor available power, can by the impulse response of channel carry out estimation with known training sequence symbols d (k) to obtain, be calculated as follows:

$u_i^{\′}\left(k\right)=d\left(k\right)\⊗{\hat{h}}_i\left(k\right)$

$P_i=\frac{1}{16}\underset{k=L+1}{\overset{L+16}{\mathrm{\Σ}}}{\left|u^{\′}\left(k\right)\right|}^2$

In formula, L is channel dispersion length, value 3 ~ 6; U ' _i(k) Received signal strength value for estimating.

In addition, noise power N _i, can according to the data u received _i(k) and u ' _ik () is estimated to obtain, be calculated as follows:

$N_i=\frac{1}{16}\underset{k=L+1}{\overset{L+16}{\mathrm{\Σ}}}{|u_i\left(k\right)-u_i^{\′}\left(k\right)|}^2.$

If assuming that noise power is invariable in the successive frame time of FACCH transmission, then wherein ${\mathrm{SNR}}_i=\frac{P_i}{N_i}$ For signal to noise ratio.

Step S3, compares the weighted sum result of trying to achieve in step S2 and the frame judging threshold of stealing preset, judges whether that there is FACCH steals frame.

Following algorithm can be adopted:

$\mathrm{flag}=\left\{\begin{array}{cc}0& y\&GreaterEqual;\mathrm{Th}\\ 1& y<\mathrm{Th}\end{array}\right.$

In formula, Th default steals frame judging threshold, due to stealing of extracting frame identification position is transmitted if it were not for full 0 be exactly complete 1, therefore threshold value can be set to 0, certainly can also arrange according to simulation result; Flag is for stealing frame judgement mark, and 0 representative steals frame, and 1 representative has steathily frame, and the result of even weighted sum is greater than or waits frame judging threshold steathily, then there is not FACCH steals frame; If the result of weighted sum is less than frame judging threshold steathily, then there is FACCH and steal frame.

A kind of gsm communication system FACCH of the present invention steals the method that frame detects, go for FACCH/F (Fast Associated Control Channel/Full Rate, full rate Fast Associated Control Channel) and/or FACCH/H (Fast Associated Control Channel/Half Rate, half rate Fast Associated Control Channel).

Respectively FACCH/F channel of the present invention, FACCH/H channel are further described below in conjunction with accompanying drawing.

FACCH/F of the present invention steals frame identification bit information as shown in Figure 3.In figure 3, shown FACCH/F uses the physical channel transmission situation of TCH/F, the frame identification information hu (B)=1 steathily of front 4 bursts of FACCH/F, the frame identification information hl (B)=1 steathily of rear 4 bursts; The frame mark information hu (B)=0 steathily of front 4 bursts of TCH/F, the frame identification information hl (B)=0 steathily of rear 4 bursts.X, Y represent and steal frame identification information with present channel onrelevant, are determined by the channel interweaved.The frame identification symbol bit information steathily that all continuous 8 bursts may occur is enumerated in Fig. 3.

FACCH/H of the present invention steals frame identification bit information as shown in Figure 4.In the diagram, shown FACCH/H uses the physical channel transmission of TCH/H, the frame identification information hu (B)=1 steathily of front 2 bursts of FACCH/H, frame identification information hu (B)=1, the hl (B)=1 steathily of middle 2 bursts, the frame identification information hl (B)=1 steathily of rear 2 bursts; The frame mark information hu (B)=0 steathily of front 2 bursts of TCH/H, the frame identification information hl (B)=0 steathily of rear 2 bursts.X, Y represent and steal frame identification information with present channel onrelevant, are determined by the channel interweaved.The frame identification symbol bit information steathily that all continuous 6 bursts may occur is enumerated in Fig. 4.

The present invention also provides a kind of gsm communication system FACCH to steal the device of frame detection in addition, comprising:

Demodulation module, for demodulation burst, obtains the soft bit information that happens suddenly;

The computing module be connected with described demodulation module, is weighted summation for the burst soft bit information being bit 1 position according to the corresponding frame identification steathily of FACCH transmission;

The multilevel iudge module be connected with described computing module, for the result of the weighted sum exported in described computing module and the frame judging threshold of stealing preset being compared, judges whether that there is FACCH steals frame.

Preferably, described computing module can adopt following formula to be weighted summation: in formula, y is for stealing framing bit soft bit information combined value, r _ifor described burst soft bit information, P _ifor available power, N _ifor noise power.

Preferably, described demodulation module can adopt the viterbi algorithm demodulation burst of level processor after soft output Viterbi algorithm or band likelihood.

As can be seen from above scheme, a kind of gsm communication system FACCH of the present invention steals method and the device of frame detection, owing to have employed weighted sum process to soft bit information, effectively improve the resistivity to channel distortions and noise, drastically increase the accuracy that FACCH steals frame detection.

Above-described embodiment of the present invention, does not form limiting the scope of the present invention.Any amendment done within the spirit and principles in the present invention, equivalent replacement and improvement etc., all should be included within claims of the present invention.

Claims (6)

1. gsm communication system FACCH steals the method that frame detects, and it is characterized in that, comprises the following steps:

Demodulation burst, obtains the soft bit information that happens suddenly;

Steal according to FACCH transmission is corresponding the burst soft bit information that frame identification is bit 1 position, adopt following formula to be weighted summation:

$y=\underset{i=1}{\overset{8}{\mathrm{\&Sigma;}}}{r}_i\&CenterDot;\frac{\sqrt{P_i}}{N_i};$

In formula, y is for stealing framing bit soft bit information combined value, r _ifor described burst soft bit information, P _ifor available power, N _ifor noise power;

The result of weighted sum and the frame judging threshold of stealing preset are compared, judges whether that there is FACCH steals frame.

2. gsm communication system FACCH according to claim 1 steals the method that frame detects, it is characterized in that, describedly judge whether to exist FACCH and steal frame and be specially: if the result of described weighted sum is more than or equal to and describedly steals frame judging threshold, then there is not FACCH and steal frame; If the result of described weighted sum is less than described frame judging threshold steathily, then there is FACCH and steal frame.

3. gsm communication system FACCH according to claim 1 steals the method that frame detects, and it is characterized in that, the mode of described demodulation burst comprises: the viterbi algorithm demodulation burst of level processor after adopting soft output Viterbi algorithm or being with likelihood.

4. any one gsm communication system FACCH according to claim 1-3 steals the method that frame detects, and it is characterized in that, is applicable to FACCH/F channel and/or FACCH/H channel.

5. gsm communication system FACCH steals the device that frame detects, and it is characterized in that, comprising:

Demodulation module, for demodulation burst, obtains the soft bit information that happens suddenly;

The computing module be connected with described demodulation module, for stealing according to FACCH transmission is corresponding the burst soft bit information that frame identification is bit 1 position, adopts following formula to be weighted summation:

$y=\underset{i=1}{\overset{8}{\mathrm{\&Sigma;}}}{r}_i\&CenterDot;\frac{\sqrt{P_i}}{N_i};$

In formula, y is for stealing framing bit soft bit information combined value, r _ifor described burst soft bit information, P _ifor available power, N _ifor noise power;

The multilevel iudge module be connected with described computing module, for the result of the weighted sum exported in described computing module and the frame judging threshold of stealing preset being compared, judges whether that there is FACCH steals frame.

6. gsm communication system FACCH according to claim 5 steals the device that frame detects, and it is characterized in that, the viterbi algorithm demodulation burst of level processor after described demodulation module adopts soft output Viterbi algorithm or is with likelihood.