CN109347516B - A kind of dynamic self-adapting multipath lookup method - Google Patents
A kind of dynamic self-adapting multipath lookup method Download PDFInfo
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- CN109347516B CN109347516B CN201811539625.XA CN201811539625A CN109347516B CN 109347516 B CN109347516 B CN 109347516B CN 201811539625 A CN201811539625 A CN 201811539625A CN 109347516 B CN109347516 B CN 109347516B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/7097—Interference-related aspects
- H04B1/711—Interference-related aspects the interference being multi-path interference
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
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Abstract
The invention discloses a kind of dynamic self-adapting multipath lookup methods, belong to wireless communication technology field, and it is not high so as to cause search accuracy to solve the problems, such as that existing multipath searching method will receive the influence of the time variation of channel.The present invention carries out multipath estimation and lookup using dynamic self-adapting thresholding in each diameter signal, using the method for solid-state thresholding in compared with the prior art, the finally obtained bit error rate is substantially reduced, it is more stable to search obtained multipath, to effectively reduce influence of the time variation to Multipath searching of channel.
Description
Technical field
The invention belongs to wireless communication technology fields, and in particular to a kind of design of dynamic self-adapting multipath lookup method.
Background technique
In a wireless communication system, due to the influence of City Building, topography and geomorphology etc., biography of the electromagnetic wave in wireless channel
Refraction, reflection, scattering etc. can be generated in defeated, so that same transmitting signal reaches receiving end from different paths, possessed not
Same time delay and phase occurs rising and falling and decline so that receiving signal.Since the phase of multipath signal is different, they may
It is overlapped mutually, it is also possible to offset each other, to can have an impact to the correct output of demodulator, the bit error rate be caused to increase.Therefore,
The Rake receiver of multipath diversity reception is generallyd use in wireless communications.
Rake receiver is to be put forward by Price and Green in 1958, is CDMA (Code Division
Multiple Access, CDMA) system key technology.Due in cdma system the bandwidth of chip width and spread spectrum at
Inverse ratio, therefore, when the time delay of multipath signal is more than a chip, in receiving end, we can demodulate them respectively, so
The signal after demodulation is merged and made decisions again afterwards.
Rake receiver excludes the interference in other paths by being separated to multipath signal, and then realizes multipath point
Collection, and by identifying, collecting multipath signal, the function of Lai Shixian multipath diversity reception.Rake receiver is mainly searched including multipath
The modules such as rope, channel estimation and multi-path combing, by each diameter carry out delay compensation, phase compensation, then to export into
Row superposition reduces the effect of the bit error rate to reach enhancing output.Since Rake receiver will operate each diameter,
Therefore most important about the correctly lookup of multipath, it is more to carry out that Multipath searching module relies primarily on the correlation properties of pseudo noise code
Diameter is searched.
For Rake receiver, each diameter is individually handled before carrying out maximum-ratio combing, therefore multipath is searched
Rope module is extremely important part in Rake receiver.When Multipath searching module must accurately be found corresponding to different diameters
Prolong, and to update search result with the time to reduce the bit error rate of system to guarantee the correctness of each diameter.
Time delay estimation is completed by correlator, usually that correlator is defeated in current existing delay time estimation method
The relevant L time delay of corresponding L maximum amplitude value is distributed to corresponding L of Rake receiver directly as time delay and " is hugged out
Rake " (i.e. compensation judging module), in this way may mistake using the multipath of a pure noise as signal distribute to Rake reception
Machine is corresponding " rake ".This mistake not only wastes system resource, also reduces the system performance of receiver.
In order to correct above-mentioned mistake, related personnel proposes through setting thresholding the probability for reducing erroneous path, passes through
Estimate the variances sigma of noise2, k σ is set by threshold value2.Since the noise of correlator output obeys Relay distribution, so inspection
The probability for measuring erroneous path is related to σ and k value.Therefore, correctly searching multipath is substantially exactly that a reasonable door is arranged
Limit value.
However existing multipath searching method is to the variances sigma of noise2After being estimated, it will usually which a fixed door is set
Limit value, correlator output is greater than time delay corresponding to the signal of the thresholding, and to distribute to Rake receiver corresponding " rake ".But
It is that, due to the influence of noise, the signal greater than the fixed threshold may be the superposition bad student due to noise.Therefore this multipath
Searching method will receive the influence of the time variation of channel, and search accuracy is not high.
Summary of the invention
The purpose of the present invention is to solve existing multipath searching method will receive the influence of the time variation of channel to
Cause to search for the not high problem of accuracy, propose a kind of dynamic self-adapting multipath lookup method, by carrying out dynamic to thresholding
Setting, to reduce influence of the time variation to Multipath searching of channel.
The technical solution of the present invention is as follows: a kind of dynamic self-adapting multipath lookup method, comprising the following steps:
S1, transmission end signal is handled in the channel of spread spectrum communication system, obtains receiving end signal.
S2, receiving end signal is inputted in the correlator of spread spectrum communication system receiving end, and most by correlator output amplitude
A big diameter signal is as reference signal.
S3, the threshold value that the diameter is set according to the fading coefficients ratio between each diameter signal and reference signal.
S4, the multipath signal that correlator output amplitude value is greater than threshold value is filtered out in spread spectrum communication system receiving end, and
The deviation of the position and correlator theoretical peak position that are occurred according to each diameter signal amplitude value determines its corresponding time delay, completes
Multipath is searched.
Further, step S1 include it is following step by step:
S11, white Gaussian noise is superimposed respectively to each diameter signal for sending end signal in the channel of spread spectrum communication system.
S12, different time delay processings is carried out to the signal of each diameter superposition white Gaussian noise.
S13, the phase offset different to the Signal averaging after each diameter time delay processing.
S14, by each diameter superposition phase offset after signal multiplied by different fading coefficients, obtain receiving end signal.
Further, in step S3 the threshold value of each diameter calculation formula are as follows:
Pl=(αl-βl)P0
P in formulalIndicate the threshold value of the l articles diameter, αlIndicate the fading coefficients ratio between the l articles diameter signal and reference signal
Value, i.e.,klFor the fading coefficients of the l articles diameter signal, k0For the fading coefficients of benchmark signal, βlFor white Gaussian noise shadow
Ring coefficient, and βl∈ [0.2,0.4], P0Indicate the amplitude of reference signal.
The beneficial effects of the present invention are: the present invention carries out multipath estimation using dynamic self-adapting thresholding in each diameter signal
And search, the middle method using solid-state thresholding, the finally obtained bit error rate are substantially reduced compared with the prior art, and lookup obtains
Multipath it is more stable, effectively reduce influence of the time variation to Multipath searching of channel.
Detailed description of the invention
Fig. 1 show a kind of dynamic self-adapting multipath lookup method flow chart provided in an embodiment of the present invention.
Fig. 2 show spread spectrum communication system structural block diagram provided in an embodiment of the present invention.
Fig. 3 show fixed threshold multipath lookup result schematic diagram provided in an embodiment of the present invention.
Fig. 4 show dynamic self-adapting threshold multi-path lookup result schematic diagram provided in an embodiment of the present invention.
Specific embodiment
Carry out detailed description of the present invention illustrative embodiments with reference to the drawings.It should be appreciated that shown in attached drawing and
The embodiment of description is only exemplary, it is intended that is illustrated the principle and spirit of the invention, and is not limited model of the invention
It encloses.
The embodiment of the invention provides a kind of dynamic self-adapting multipath lookup methods, as shown in Figure 1, including the following steps S1
~S4:
S1, transmission end signal is handled in the channel of spread spectrum communication system, obtains receiving end signal.
In the embodiment of the present invention, spread spectrum communication system as shown in Fig. 2, mainly include transmitting terminal, channel and receiving end,
Wherein each frame signal includes 5104 data and 16 pilot tones, using 10 times of cyclic spreading code.Purport of the embodiment of the present invention
The specific method of dynamic self-adapting multipath lookup, remaining signal of spread spectrum communication system are carried out in channel and receiving end in explanation
Treatment process (such as the signal modulation of transmitting terminal and the signal of receiving end demodulate) belongs to the common knowledge of this field, herein not
It repeats again.
In existing Rake receiver, it is only necessary to estimate the time delay of the stronger L diameter of energy.And traditional
In Multipath searching module, range value maximum L are found out after carrying out correlation to the signal that receiving end receives, by its corresponding time delay
It is considered as the time delay that Multipath searching needs to find out.But due to the presence of interchannel noise, range value may be due to interchannel noise greatly
Correlation caused by.After a fixed threshold is set, due to the time variation of channel, Multipath Time Delay Estimation mistake will also result in.
Therefore a kind of adaptive multipath lookup method is proposed in embodiments of the present invention.
Step S1 includes following S11~S14 step by step:
S11, white Gaussian noise is superimposed respectively to each diameter signal for sending end signal in the channel of spread spectrum communication system.
S12, different time delay processings is carried out to the signal of each diameter superposition white Gaussian noise.
S13, the phase offset different to the Signal averaging after each diameter time delay processing.
S14, by each diameter superposition phase offset after signal multiplied by different fading coefficients, obtain receiving end signal.
Finally obtained receiving end signal y [n] indicates are as follows:
Wherein n indicates different moments, and x [n] indicates to send end signal, and N indicates the sum of multipath in channel, klIndicate l
The fading coefficients of diameter, τlIndicate the time delay of the l articles diameter, θlIndicate the phase offset of the l articles diameter, Nl[n] indicates that the l articles diameter is folded
The white Gaussian noise added.
S2, receiving end signal is inputted in the correlator of spread spectrum communication system receiving end, and most by correlator output amplitude
A big diameter signal is as reference signal.
Receiving end signal may be expressed as: after correlator
Wherein Ry[τ] indicates that correlator output signal, τ are correlator output amplitude, N0For correlator chip sum, x*[n]
Pilot frequency sequence signal after indicating spread spectrum, as τ=τlWhen, correlator has maximum output, it may be assumed that
According to formula (2) and formula (3) it is found that the output amplitude and fading coefficients k of each diameter signallCorrelation, therefore this
In inventive embodiments, the maximum diameter signal of correlator output amplitude is chosen as reference signal, and passes through each diameter decline system
Number klFading coefficients k corresponding with reference signal0Between relativeness as the diameter decision threshold.
S3, the threshold value that the diameter is set according to the fading coefficients ratio between each diameter signal and reference signal.
The specific formula for calculation of the threshold value of each diameter are as follows:
Pl=(αl-βl)P0 (4)
P in formulalIndicate the threshold value of the l articles diameter, αlIndicate the fading coefficients ratio between the l articles diameter signal and reference signal
Value, i.e.,klFor the fading coefficients of the l articles diameter signal, k0For the fading coefficients of benchmark signal, βlFor white Gaussian noise shadow
Ring coefficient, and βl∈ [0.2,0.4], in the embodiment of the present invention, due to consideration that height of each diameter range value also by each diameter
The influence of this white noise, therefore joined white Gaussian noise influence factor beta in threshold value calculation formulal, P0Indicate reference signal
Amplitude.
For example, if the fading coefficients k of reference signal0=0.9, the fading coefficients k of the first diameter signal1=0.75, then declining is
Number ratioCarry it into the threshold value P of the settable first diameter signal of formula (4)1=0.6P0。
S4, the multipath signal that correlator output amplitude value is greater than threshold value is filtered out in spread spectrum communication system receiving end, and
The deviation of the position and correlator theoretical peak position that are occurred according to each diameter signal amplitude value determines its corresponding time delay, then will
It is corresponding " rake " that the time delay of each diameter distributes to Rake receiver, and multipath lookup can be completed.
In the embodiment of the present invention, carried out using the correlator of 50 chips it is related, therefore theoretically without when be delayed peak value
The position of appearance should be 50.In this way, subtracting 50 by the position of correlator output amplitude value, obtain is exactly corresponding each diameter
Time delay.
Effect of the present invention is described further with specific experiment example below.
A fixed threshold value is selected first by the way of the prior art, in simulink module Local
Threshold value is set in Maxima, it is hereby achieved that the multidiameter delay estimated, as shown in Figure 3.Estimate respectively from top to bottom in Fig. 3
Be time delay be 0,5,8 diameter.Due to using fixed door limit value, the sometimes output of correlator is more than that thresholding may be due to making an uproar
Caused by sound, so time delay estimation mistake can be generated or be estimated as the time delay of other diameters.Third diameter in Fig. 3, in ideal feelings
Time delay should be 8 always under condition, but make that the case where being estimated as 24 can be generated due to interchannel noise etc., that is, be estimated as another
The case where one diameter, such case occur 8 times within the 1s time of emulation.
And when using a kind of dynamic self-adapting multipath lookup method proposed by the invention, lookup result as shown in figure 4,
By being compared with Fig. 3, it can be found that the third diameter estimated using fixed door limit value does not use dynamic self-adapting threshold value
The stabilization estimated.Also, it is also different using the finally obtained bit error rate of the two, in the case where running in 5s, using solid
The bit error rate for determining threshold value is 1.961e-06, and use the bit error rate of dynamic self-adapting thresholding for 3.922e-07.Therefore, of the invention
Using the method for solid-state thresholding in compared with the prior art, the finally obtained bit error rate is substantially reduced, the multipath searched
It is more stable, effectively reduce influence of the time variation to Multipath searching of channel.
Those of ordinary skill in the art will understand that the embodiments described herein, which is to help reader, understands this hair
Bright principle, it should be understood that protection scope of the present invention is not limited to such specific embodiments and embodiments.This field
Those of ordinary skill disclosed the technical disclosures can make according to the present invention and various not depart from the other each of essence of the invention
The specific variations and combinations of kind, these variations and combinations are still within the scope of the present invention.
Claims (2)
1. a kind of dynamic self-adapting multipath lookup method, which comprises the following steps:
S1, transmission end signal is handled in the channel of spread spectrum communication system, obtains receiving end signal；
S2, receiving end signal is inputted in the correlator of spread spectrum communication system receiving end, and correlator output amplitude is maximum
One diameter signal is as reference signal；
S3, the threshold value that the diameter is set according to the fading coefficients ratio between each diameter signal and reference signal；
S4, spread spectrum communication system receiving end filter out correlator output amplitude value be greater than threshold value multipath signal, and according to
The deviation of position and correlator theoretical peak position that each diameter signal amplitude value occurs determines its corresponding time delay, completes multipath
It searches；
The calculation formula of the threshold value of each diameter in the step S3 are as follows:
Pl=(αl-βl)P0
P in formulalIndicate the threshold value of the l articles diameter, αlIndicate the fading coefficients ratio between the l articles diameter signal and reference signal, i.e.,klFor the fading coefficients of the l articles diameter signal, k0For the fading coefficients of benchmark signal, βlSystem is influenced for white Gaussian noise
Number, and βl∈ [0.2,0.4], P0Indicate the amplitude of reference signal.
2. dynamic self-adapting multipath lookup method according to claim 1, which is characterized in that the step S1 includes following
Step by step:
S11, white Gaussian noise is superimposed respectively to each diameter signal for sending end signal in the channel of spread spectrum communication system；
S12, different time delay processings is carried out to the signal of each diameter superposition white Gaussian noise；
S13, the phase offset different to the Signal averaging after each diameter time delay processing；
S14, by each diameter superposition phase offset after signal multiplied by different fading coefficients, obtain receiving end signal.
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| TW567682B (en) * | 2002-03-01 | 2003-12-21 | Benq Corp | System and method to adjust searcher threshold parameter of RAKE receiver |
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