A kind of method of accessing randomly front detection dynamic threshold
Technical field
The present invention relates to a kind of method of mobile communication, in particular, the method that a kind of WCDMA system random access channel preamble detects.
Background technology
In the WCDMA system, travelling carriage communicates in order to want access network, sends a period of time preface information usually earlier, after the base station receives this preface information and confirms, travelling carriage can be launched the access message of a period of time, has wherein comprised the important parameter information that communication is set up.The base station could successfully set up for the communication link of this travelling carriage special use after receiving these message.Usually, this process is called as random access procedure.
Inserting at random is a very important part in the WCDMA system, is subscriber equipment is set up dedicated channel when sub-district registration and the calling of registration back prerequisite and basis, and therefore the performance that inserts at random is very important.
Random access guiding detection method comparatively commonly used at present mainly is, detect leading by setting a changeless thresholding, every energy will go on record greater than the multipath of this thresholding, if a certain signature has the energy of a multipath at least greater than this thresholding, think that then this signature is effective, otherwise invalid.
This method implements fairly simple, but but is very difficult to the definite of thresholding in fact: if thresholding is too high, detected multipath will be considerably less, and have influence on the demodulation performance that inserts message; If thresholding is too low, then can cause false alarm probability too high, thereby take limited demodulation resource, under the serious situation even can cause blocking, make real effectively signature not have available demodulation resource on the contrary.
And existing dynamic threshold method also is to pre-determine a threshold value, readjust this threshold value through behind the message demodulation again by the misjudgment rate, though this method has certain improvement to front fixed threshold method, but it is long partially to adjust its adjustment cycle of thresholding again behind the process message demodulation, does not really accomplish definite detection of preamble thresholding of dynamic real-time.
Therefore, prior art has yet to be improved and developed.
Summary of the invention
The method that the purpose of this invention is to provide a kind of accessing randomly front detection dynamic threshold, overcome thresholding selection difficulty in the fixed threshold method that exists in the prior art, false-alarm is too much, demodulating unit blocks, shortcomings such as existing dynamic threshold method thresholding adjustment cycle is long, in the hope of propose a kind of can be dynamic, real-time, and realize determining easily the method for leading thresholding, can guarantee leading in the effectively detection of signature, there is abundant multipath to be used to insert message demodulation, can prevent that again false alarm rate is too high, prevent that the dynamic threshold of access at random of choking phenomenon appearance from determining method.
For achieving the above object, technical scheme of the present invention comprises:
A kind of method of accessing randomly front detection dynamic threshold, it may further comprise the steps:
A: to input signal carry out descrambling, separate frequency deviation, separate signature, relevant non-coherent integration process, the signature power time delay that obtains certain access slot detection of preamble task distributes;
B: determine this detection of preamble task average noise horizontal estimated value;
C: utilize the estimated value of the noise average level that step B obtains and the signal to noise ratio of upper-layer configured, the coherent integration length dynamic real-time is the thresholding of an order detection of preamble task really;
D: utilize described steps A, B, C to determine the thresholding of all detection of preamble tasks in this access slot successively, therefrom get the thresholding of maximum threshold value as the detection of preamble of this access slot.
Described method wherein, is provided with thresholding factor T
RNC, coherence length CA, described steps A comprises: the antenna data to input carries out descrambling, multiply each other relevant with scrambler; Compensate of frequency deviation carries out the CM operation with the frequency shift (FS) factor; Coherent integration is carried out coherent integration according to given length; Signatures match is separated signature with fast hadamard transform; Non-coherent integration is carried out noncoherent accumulation according to given length and is handled; The power time delay that obtains 16 signatures of certain detection of preamble task of certain access slot distributes.
Described method, wherein, the described signature power time delay distribution results that obtains, the result makes an uproar at the bottom of 15 results that comprise that the leading search of 16 signatures in each comfortable search window scope can the discharge amplitude maximum and 1.
Described method, wherein, described step B also comprises: utilize formula Amp=(Amp
0+ Amp
1+ ...+Amp
M-1)/M calculates and reports noise amplitude Amp
0, Anp
1..., Amp
M-1Average obtain the estimated value Amp of the average noise amplitude of this detection of preamble task.
Described method, wherein, described step C also comprises: utilize the estimated value Amp of the average noise amplitude that obtains and the signal to noise ratio T of upper-layer configured
RNC, coherent integration length CA dynamic real-time is determined the thresholding of single detection of preamble task.
Described method, wherein, described step C also comprises:
C1: utilize formula a=5-(T
RNC>>4)-(T
RNC/ 48) obtain multiplication factor;
C2: utilize formula
Calculate the detection of dynamic thresholding.
Described method, wherein, described step C2 also comprises: gawPdRncThTab[T
RNC] be by formula
The table that calculates, table look-at when calculating.
Described method, wherein, described step C1 also comprises: according to signal to noise ratio parameter T
RNCCarried out the amplification of different multiples, determined multiplication factor so that do reduction.
The method of a kind of accessing randomly front detection dynamic threshold proposed by the invention, compared with prior art, its advantage is: by noise level is estimated, definite detection of preamble thresholding that can be dynamic, real-time, and thresholding is set simple, and single thresholding just can be finished the current leading processing of catching; Simultaneously, when the energy of certain access slot signature was big, the inventive method can correspondingly obtain a bigger amplitude thresholding, thereby reaches the phenomenon of avoiding producing a large amount of false-alarms; By the test of real system, most of false-alarm can be effectively abandoned in being provided with rationally effectively of this thresholding of the present invention, false alarm probability is controlled in the scope of agreement permission, has guaranteed detection probability simultaneously.
Description of drawings
Fig. 1 is definite method flow diagram of WCDMA of the present invention system accessing randomly front detection dynamic threshold.
Embodiment
Below in conjunction with accompanying drawing, will prove absolutely the specific embodiment of the present invention, so that technical scheme of the present invention and beneficial effect thereof are more readily understood.
Definite method of a kind of WCDMA of the present invention system accessing randomly front detection dynamic threshold, it may further comprise the steps:
The first step: to input signal carry out descrambling, separate frequency deviation, separate signature, relevant non-coherent integration process, the signature power time delay that obtains certain access slot detection of preamble task distributes.
Second step: determine this detection of preamble task average noise horizontal estimated value.
The 3rd step: utilize second to go on foot the estimated value of the noise average level that obtains and the signal to noise ratio of upper-layer configured, the coherent integration length dynamic real-time is the thresholding of an order detection of preamble task really.
The 4th step: utilized for the first, the second, the 3rd step determined the thresholding of all detection of preamble tasks in this access slot successively, therefrom get the thresholding of maximum threshold value as the detection of preamble of this access slot.When definite detection of preamble thresholding, the noise when it is generally acknowledged the different frequency deviation of same access slot is identical, so the max threshold of only choosing all tasks is as last result.
In this preferred embodiment of the present invention, as shown in Figure 1, suppose thresholding factor T
RNC=36, coherence length CA=1024, specific operation process of the present invention is as follows:
Step 101: the antenna data to input carries out descrambling (multiply each other relevant with scrambler), compensate of frequency deviation (carrying out the CM operation) with the frequency shift (FS) factor, coherent integration (carrying out coherent integration) according to given length, signatures match (separating signature) with fast hadamard transform, non-coherent integration (carrying out noncoherent accumulation according to given length) is handled, and the power time delay that obtains 16 signatures of certain detection of preamble task of certain access slot distributes.
In this preferred embodiment, result's (end is hot-tempered to be the summation of this signature other all energy discharge amplitudes except that 15 ceiling capacity amplitudes) makes an uproar at the bottom of 15 results that the signature power time delay distribution results that obtains comprises that the leading search of 16 signatures in each comfortable search window scope can the discharge amplitude maximum and 1, it is not real signal energy, therefore when definite noise level and thresholding, what obtain also is noise average amplitude and output amplitude thresholding.The hot-tempered amplitude results in the end that suppose 16 signatures that a leading search mission obtains through above-mentioned processing be respectively 10,10,12,11,11,9,10,11,9,10,12,11,10,8,10,11}.
Step 102: utilize formula Amp=(Amp0+Amp
1+ ...+Amp
M-1)/M calculates and reports noise amplitude Amp
0, Amp
1..., Amp
M-1Average obtain the estimated value Amp of the average noise amplitude of this detection of preamble task.
Amp=10 in this example.According to formula I
0=(Amp*Amp*c)/(N
AntNCA*CA), can know as coherent integration length CA, non-coherent integration length N CA and antenna number N
AntIn the time of certain, noise level I
0Square Amp with noise amplitude
2Between corresponding relation immobilize.As long as therefore obtain noise amplitude Amp, just equal to obtain noise level.
Step 103: utilize the estimated value Amp of the average noise amplitude that step 102 obtains and the signal to noise ratio T of upper-layer configured
RNC, coherent integration length CA dynamic real-time is determined the thresholding of single detection of preamble task.And can be divided into following step:
Step 103.1: utilize formula a=5-(T
RNC>>4)-(T
RNC/ 48) obtain multiplication factor.A=3 in this example.In step 103.2, because there are a large amount of square root calculations, in order not influence precision of calculation results, according to signal to noise ratio parameter T
RNCCarried out the amplification of different multiples, needed here to determine that multiplication factor is so that do reduction at last.
Step 103.2: utilize formula
Calculate the detection of dynamic thresholding.GawPdRncThTab[T wherein
RNC] be by formula
The table that calculates, table look-at when calculating, thus improve computational efficiency.Table look-up in this example and obtain gawPdRncThTab[36]=258, so T
d=40.
Step 104: if T
d>T, then T=T
dWherein T is used for writing down the maximum threshold of all detection of preamble tasks in the same access slot.
The inventive method is by estimating noise level, definite detection of preamble thresholding that can be dynamic, real-time, and thresholding sets simply, and single thresholding just can be finished the current leading processing of catching; Simultaneously, when the energy of certain access slot signature was big, the inventive method can correspondingly obtain a bigger amplitude thresholding, thereby reaches the phenomenon of avoiding producing a large amount of false-alarms; By the test of real system, most of false-alarm can be effectively abandoned in being provided with rationally effectively of this thresholding of the present invention, false alarm probability is controlled in the scope of agreement permission, has guaranteed detection probability simultaneously.
Should be understood that above-mentioned description at specific embodiment is comparatively detailed, can not therefore be interpreted as the restriction to scope of patent protection of the present invention, scope of patent protection of the present invention should be as the criterion with claims.