CN1987515A - Method and systme for realizing GPS positioning under weak signal environment - Google Patents
Method and systme for realizing GPS positioning under weak signal environment Download PDFInfo
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- CN1987515A CN1987515A CNA2005101319852A CN200510131985A CN1987515A CN 1987515 A CN1987515 A CN 1987515A CN A2005101319852 A CNA2005101319852 A CN A2005101319852A CN 200510131985 A CN200510131985 A CN 200510131985A CN 1987515 A CN1987515 A CN 1987515A
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Abstract
The method includes steps: forecasting navigation data in GPS signal; converting the received GPS signal to intermediate frequency (IF) signal; executing continuous correlation calculation for IF signal and forecasted navigation data, local carrier generated by GPS receiver and local pseudo-random noise code (PRNC) in order to obtain phase shift of PRNC; from navigation data based on forecasting and together with phase shift based on PRNC to calculate position of GPS receiver; using forecasted navigation data to remove navigation data in IF signal so as to eliminate SNR loss brought by sign flip of navigation bit. Thus, continuous integration for long time is implemented for IF signal to raise SNR.
Description
Technical field
The present invention relates to the method and system of GPS location, particularly relate to the method and system that is implemented in GPS location under the feeble signal environment such as indoor.
Background technology
GPS (GPS) has obtained widespread use in the civil and military field, as is used to the demand relevant with the location with other of locating, navigate.In fact, the basis of GPS widespread use is the GPS receiver, and it receives the gps signal that is sent by gps satellite.
Gps signal is by the spread-spectrum signal of gps satellite in L1 or the transmission of L2 frequency.Current civilian GPS receiver uses L1 frequency (1575.42MHZ) usually.The several signals that send on the L1 carrier wave are: thick catch code (C/A sign indicating number), P sign indicating number and navigation data.The detailed data of satellite orbit is included in the navigation data.The C/A sign indicating number is mainly used in the location purposes in the commercial receiver.The C/A sign indicating number is used to judge pseudorange (pseudorange is the distance that is subjected to various GPS error effects).The C/A sign indicating number is a kind of Pseudo-Random Noise Code (a PRN sign indicating number), and the radiofrequency signal behind C/A sign indicating number coding becomes spread-spectrum signal.Each satellite all has a unique C/A sign indicating number, and this C/A sign indicating number that circulates repeatedly.The C/A sign indicating number is one 0 and 1 (scale-of-two) sequence.Each 0 or 1 is considered to one " chip ".The C/A sign indicating number has 1023 chips long, and sends with the speed of per second 1.023 million chips, and promptly the one-period of C/A sign indicating number continues 1 millisecond.Those of ordinary skill in the art can think that " chip " is the unit of data length or time span.Each chip also can think to have two states :+1 and-1.Navigation data also is one 0 and 1 (scale-of-two) sequence, and sends with the speed of per second 50 bits.
For realizing the location, the GPS receiver need be caught from least four Satellite GPS signals, demodulates the navigation data of four gps signals.Pass through different dissemination channels from different Satellite GPS signals.Usually, the GPS receiver is handled the gps signal from several channels simultaneously.Each gps signal all has one to have the C/A sign indicating number of different zero-times and different Doppler shift amounts.Therefore, for searching for certain satellite-signal, the GPS receiver carries out two dimension search usually, on each possible frequency the different C/A sign indicating number of each zero-time is searched for." different zero-time " herein can be understood as the result of C/A code phase time-delay.In the GPS receiver, adopt the starting point of catching method search C/A sign indicating number and the Doppler shift of the frequency of carrier wave, particularly signal.For whether the signal of search in certain characteristic frequency point and specific C/A sign indicating number time-delay place exists, the GPS receiver is tuned to this frequency, and gps signal and local C/A sign indicating number carry out related operation, and the amount of delay of C/A sign indicating number is relevant with the time of gps signal arrival receiver.If do not search signal, then continue search and have the C/A sign indicating number that the next one may be delayed time.Usually, each possible time-delay of C/A sign indicating number obtains by mobile C/A sign indicating number 1/2 chip.Because the C/A sign indicating number comprises 1023 chips, need detect 2046 possible time-delays so search for a fixed frequency.After all possible time-delay has detected, continue the next possible frequency of search.Since do not know Doppler shift accurately, therefore need be at thousands of the possible enterprising line search of frequency, and the progress of acquisition procedure is very slow.
Fig. 1 has illustrated the structured flowchart of GPS receiver 100 of prior art.Usually, the GPS receiver comprises two parts: RF front-end module 110 and baseband signal processing unit 120.The gps signal that gps satellite transmits is received by antenna 112, and by RF tuner 114 and frequency synthesizer 116, the signal that receives is converted to the signal with desired output frequency from gps signal.Then, analog/digital converter (ADC) 118 with predetermined sampling frequency will change signal digitalized.Be considered to intermediate-freuqncy signal through conversion and digitized signal.This intermediate-freuqncy signal then is sent to the baseband signal processing unit 120 that comprises several signal processing stages.Intermediate-freuqncy signal is sent to trapping module 122, and Doppler shift search and C/A sign indicating number phase shift search are carried out in trapping module 122.At acquisition phase, the related operation that is undertaken by intermediate-freuqncy signal and C/A sign indicating number is finished the integration to intermediate-freuqncy signal.Tracking module 124 uses carrier tracking loop and code tracking loop to follow the tracks of gps signal, thereby obtains the navigation data that comprises in the gps signal.Then, navigation data computing module 126 and position computation module 128 utilize navigation data to calculate the position of receiver.
As mentioned above, need capture the position that gps signal that four satellites send just can calculate the GPS receiver usually.Under outdoor and environment that the open degree of sky is preferable, be not difficult to accomplish this point.But under the environment of indoor or other signal shieldings, because gps signal is very faint, the receiver under traditional unit (stand-alone) pattern can not capture four Satellite GPS signals indoor, can't realize the location.In order to realize locating under the indoor environment, the sensitivity of GPS receiver must reach-155dBm, even surpasses-160dBm, so just need do long continuous integration to gps signal, as 1 second time.The related operation that the local C/A sign indicating number that the continuous integration of gps signal produces by gps signal and receiver carries out is finished.Yet, because the navigation data in the gps signal bit symbol upset just may occur for per 20 milliseconds, the snr loss who brings for fear of bit symbol upset, the continuous integration time can not be oversize, generally can only get in 10 milliseconds, thereby can not satisfy receiver in the required sensitivity of indoor positioning.In addition, because search is based on the two-dimensional search of Doppler shift and C/A sign indicating number, gps signal is done long continuous integration, corresponding frequency resolution (being frequency step) is low, so in the Doppler shift scope (be generally+/-when 5Khz) searching for, search speed is very slow, thereby influences the time of receiver location.
Summary of the invention
The object of the present invention is to provide the method for utilizing gps signal that the GPS receiver is positioned under a kind of feeble signal environment, it can realize the long-time continuous integration of gps signal, to improve signal to noise ratio (S/N ratio).
Another object of the present invention is to provide the system that utilizes the gps signal location under a kind of feeble signal environment, it can realize the long-time continuous integration of gps signal, to improve signal to noise ratio (S/N ratio).
For achieving the above object, the invention provides a kind of method of under the feeble signal environment, utilizing gps signal to position of being suitable for to the GPS receiver.Gps signal comprises carrier wave, Pseudo-Random Noise Code and navigation data, and wherein Pseudo-Random Noise Code and navigation data are modulated on the carrier wave.The GPS receiver produces local carrier and local Pseudo-Random Noise Code.This method may further comprise the steps: the navigation data in the gps signal is predicted; Receive described gps signal; The gps signal that receives is converted to intermediate-freuqncy signal; Navigation data, local carrier and the local Pseudo-Random Noise Code of intermediate-freuqncy signal and prediction are carried out the serial correlation computing; Obtain the phase shift of Pseudo-Random Noise Code; With based on the navigation data of prediction and the phase shift of Pseudo-Random Noise Code, calculate the position of GPS receiver.
As the improvement of such scheme, further comprising the steps of in described prediction steps: the Doppler shift of prediction carrier wave and the rate of change of Doppler shift; And, adjust the frequency of local carrier in the serial correlation calculating process based on the Doppler shift of prediction and the rate of change of Doppler shift.
The present invention also provides a kind of method of handling gps signal in the GPS receiver.Gps signal comprises carrier wave, Pseudo-Random Noise Code and navigation data, and wherein Pseudo-Random Noise Code and navigation data are modulated on the carrier wave.The GPS receiver produces local carrier and local Pseudo-Random Noise Code.This method may further comprise the steps: the navigation data that produces prediction; Gps signal is converted to intermediate-freuqncy signal; With navigation data, local carrier and the computing of local Pseudo-Random Noise Code execution serial correlation with intermediate-freuqncy signal and prediction.
The present invention also provides the method for a kind of GPS of processing receiver location.The GPS receiver receives gps signal, and gps signal comprises carrier wave, Pseudo-Random Noise Code and navigation data, and wherein Pseudo-Random Noise Code and navigation data are modulated on the carrier wave.This method may further comprise the steps: 1) catch gps signal; 2) judge the Satellite GPS signal that whether successfully captures predetermined quantity; 3) if judge acquisition success, the position that then begins the trace daemon of gps signal and calculate the GPS receiver; 4), begin to search for and oneself whether preserve effective historical supplementary if judge and to catch failure; 5),, predict the navigation data that it will receive from satellite according to this effective historical supplementary if there is effective historical supplementary; 6), catch the Satellite GPS signal of predetermined quantity based on the navigation data of described prediction; 7) follow the tracks of gps signal that captures and the position of calculating the GPS receiver; 8) if there is no effective historical supplementary provides supplementary to the assistant base station application; 9) supplementary that provides based on described assistant base station is caught the Satellite GPS signal of predetermined quantity; And 10) follow the tracks of gps signal that captures and the position of calculating the GPS receiver.
The present invention also provides a kind of system that realizes GPS location under the feeble signal environment.This system comprises assistant base station and GPS receiver.Assistant base station comprises prediction module, its dope receiver will be in a certain particular moment the navigation data from the gps signal that satellite receives.The GPS receiver comprises radio-frequency front-end and baseband signal processing unit.Baseband signal processing unit comprises trapping module and position computation module.Radio-frequency front-end received from described Satellite GPS signal and is converted into intermediate-freuqncy signal in described a certain particular moment.Trapping module is carried out the serial correlation computing with the navigation data of intermediate-freuqncy signal and assistant base station prediction, local carrier and the local Pseudo-Random Noise Code that the GPS receiver produces, obtain the phase shift of Pseudo-Random Noise Code, position computation module is calculated the position of GPS receiver based on the navigation data of prediction and the phase shift of Pseudo-Random Noise Code.
Compared with prior art, the present invention utilizes the navigation data of prediction to make multiplication mutually with intermediate-freuqncy signal, removes the navigation data in the intermediate-freuqncy signal, just can eliminate the snr loss that the upset of navigation bit symbol brings, thereby realize the long continuous integration of intermediate-freuqncy signal, signal to noise ratio (S/N ratio) is improved.The Doppler shift of prediction is used for regulating the frequency of the local carrier that receiver produces, thereby need not search in the Doppler shift scope, accelerates the process of catching.The rate of change of the Doppler shift of prediction can make Doppler shift pass in time and adjust, thereby improves the degree of accuracy of serial correlation computing, improves signal to noise ratio (S/N ratio).
Description of drawings
Other characteristic of the present invention and advantage will be in following detailed descriptions and are more obvious in conjunction with illustrated explanation, and wherein same numbers is represented similar elements, and wherein:
Fig. 1 is the structured flowchart of existing GPS receiver.
Fig. 2 is the schematic diagram of GPS positioning system of the present invention.
Fig. 3 is the GPS receiver in the GPS positioning system shown in Figure 2 and the detailed block diagram of AGPS assistant base station.
Fig. 4 is the structured flowchart of trapping module of the GPS receiver of one embodiment of the invention.
Fig. 5 is the structured flowchart of tracking module of the GPS receiver of one embodiment of the invention.
Fig. 6 is the process flow diagram of the GPS receiver position fixing process of one embodiment of the invention.
Embodiment
Fig. 2 is the structural drawing of GPS positioning system 200 of the present invention.This positioning system 200 comprises plurality of GPS satellites 202, GPS receiver 204, AGPS assistant base station 206 and wireless base station 208.Satellite 202 emission gps signals are given GPS receiver 204 and AGPS assistant base station 206.In the present embodiment, GPS receiver 204 and AGPS assistant base station 206 receive the gps signal of four satellites, 202 emissions.AGPS assistant base station 206 is according to the gps signal that had before received, and the supplementary that prediction is relevant is as the rate of change of navigation data, Doppler shift and Doppler shift in following a period of time etc.Supplementary sends to GPS receiver 204 via wireless base station 208.GPS receiver 204 is in the location that can realize under the help of supplementary under indoor or other signal shielding environment.Localization process about GPS receiver 204 will be described in detail hereinafter.
Fig. 3 is the detailed block diagram of GPS receiver 204 and AGPS assistant base station 206 among Fig. 2.GPS receiver 204 and AGPS assistant base station 206 receive the gps signal of same gps satellite 202 in the synchronization emission.Gps signal comprises carrier wave, Pseudo-Random Noise Code and navigation data, and wherein Pseudo-Random Noise Code (C/A sign indicating number) and navigation data are modulated on the carrier wave.GPS receiver 204 comprises two parts: radio-frequency front-end 210 and baseband signal processing unit 220.Radio-frequency front-end 210 is consistent with the structure of the radio-frequency front-end 110 that Fig. 1 discloses, and for simplicity's sake, repeats no more here.The gps signal that radio-frequency front-end 210 reception gps satellites 202 transmit also is converted into intermediate frequency (IF) signal.This intermediate-freuqncy signal then is sent to the baseband signal processing unit 220 that comprises several signal processing stages.Baseband signal processing unit 220 comprises trapping module 222, tracking module 224, post-processing module 226, position computation module 228, clock synchronization unit 230 and real-time clock (RTC) 232, and the 26S Proteasome Structure and Function of these modules will be described hereinafter one by one.
AGPS assistant base station 206 comprises prediction module 242 and real-time clock (RTC) 244.Prediction module 242 relevant temporal informations are indicated by real-time clock 244.AGPS assistant base station 206 receives the gps signal that gps satellite 202 transmits.The GPS navigation data that a frame is complete in the gps signal comprise 1500 Bit datas, be made of 5 subframes, and most of bit of each subframe have that to change frequency little, predictability and cycle repeatability.Therefore, the prediction module 242 of AGPS assistant base station 206 can be according to the navigation data from a certain satellite that had before received, and doping same satellite will be at a certain moment T in future
0Navigation data in the gps signal of emission, and dope GPS receiver 204 and receive that same satellite is at T
0The moment T of the gps signal of emission
1The T time of reception of prediction
1Obtain by following formula: T
1=T
0+ Δ t
0, Δ t wherein
0It is the mistiming of gps signal, by the relative distance decision of satellite and GPS receiver 204 from satellite transmits to GPS receiver 204.Because the distance between AGPS assistant base station 206 and the GPS receiver 204 is less than the distance between GPS receiver 204 and the satellite, therefore, Δ t
0Be approximately equal to the mistiming of gps signal from satellite transmits to AGPS assistant base station 206.Prediction module 242 dopes because the Doppler shift of the gps signal that relatively moving between satellite and the GPS receiver 204 causes and the rate of change of Doppler shift also according to the navigation data from satellite that had before received.AGPS assistant base station 206 is given the trapping module 222 of receiver 204 rate of change of the navigation data, Doppler shift and the Doppler shift that predict.In preferred embodiment, the rate of change of the navigation data of prediction, Doppler shift and Doppler shift is received T at GPS receiver 204
0Send to GPS receiver 204 before the gps signal of emission constantly, and be stored in the supplementary storer 302 (shown in Figure 4) of trapping module 222, remedy the mistiming that Network Transmission is brought with this.
At trapping module 222, the navigation data of prediction is made multiplication mutually with intermediate-freuqncy signal, remove the navigation data in the intermediate-freuqncy signal, just can eliminate the snr loss that the upset of navigation bit symbol brings, thereby realize the long continuous integration of intermediate-freuqncy signal, to improve signal to noise ratio (S/N ratio).The continuous integration of intermediate-freuqncy signal is finished by the navigation data of intermediate-freuqncy signal and prediction, the local carrier of GPS receiver 204 generations and the serial correlation computing that local C/A sign indicating number carries out in trapping module 222.The Doppler shift value that AGPS assistant base station 206 dopes GPS receiver 204 when receiving gps signal is regulated the frequency of the local carrier that receiver 204 produces with this, thereby need do not searched in the Doppler shift scope, accelerates the process of catching.Because Doppler shift changes in time, when the continuous integration time is longer, as more than the second level, the variation of Doppler shift just becomes a problem that can not be ignored, AGPS assistant base station 206 offers the rate of change of Doppler shift of the prediction of GPS receiver 204, can make Doppler shift pass in time and adjust, thereby improve the degree of accuracy of serial correlation computing (continuous integration), improve signal to noise ratio (S/N ratio).
When not having visible satellite, be that GPS receiver 204 is can not come out the navigation data demodulation of any satellite-signal the time, clock synchronization handle to adopt following scheme: assistant base station 206 provides supplementary to GPS receiver 204, and supplementary comprises that the GPS receiver 204 of prediction will receive the moment of this gps signal, the Doppler shift of gps signal and the rate of change of Doppler shift from the navigation data the gps signal that satellite 202 receives, GPS receiver 204; All channel configurations of GPS receiver 204 are become to catch the gps signal of same satellite 202 emissions; The navigation data that utilizes prediction is in the local reception time of each channel IT gps signal with the acquisition gps signal; Based on the local reception time of gps signal and the time of reception of prediction, proofread and correct the real-time clock 232 of GPS receiver 204.In one embodiment of the invention, catching gps signal can obtain in the following manner with the local reception time that obtains gps signal: 1) gps signal is converted to intermediate-freuqncy signal; 2) produce local carrier and local Pseudo-Random Noise Code; 3) with the starting point of the navigation data alignment intermediate-freuqncy signal of prediction; 4) navigation data of described intermediate-freuqncy signal and prediction, local carrier and local Pseudo-Random Noise Code are carried out the serial correlation computing of schedule time length, for example, this schedule time length is 1s; 5) phase place of the local Pseudo-Random Noise Code of skew; 6) repeating step 4) and 5), up to from the related operation result, searching a peak value; 7) if do not search peak value, with the navigation data of prediction with respect to the starting point of intermediate-freuqncy signal skew a period of time, as 1 millisecond; 8) repeating step 4) to 7); 9) with the navigation data of prediction with respect to 20 milliseconds of the starting point of intermediate-freuqncy signal skews, repeating step 4) and 5), until searching a peak value; With 10) skew of the phase shift of Pseudo-Random Noise Code when searching peak value and the navigation data of prediction, obtain local reception time of gps signal.In this acquisition procedure, utilize the Doppler shift in the supplementary and the rate of change of Doppler shift that local carrier frequency is adjusted in time.
Fig. 4 is the structured flowchart of the trapping module 222 of one embodiment of the invention.Trapping module 222 comprises: from integrator 300-0 (claim not only correlator 0) to integrator 300-2045 2046 parallel integrators (but also claiming parallel correlator), the supplementary storer 302 of (claim not only correlator 2045) serial number, produce local C/A sign indicating number PRN sign indicating number generator 304, produce the local oscillator 306 and the search module 308 of local carrier.As previously mentioned, the supplementary of storage comprises that the receiver 204 of prediction will be at the rate of change of navigation data, the Doppler shift of this particular moment and the Doppler shift of a certain particular moment from the gps signal that satellite receives in the supplementary storer 302.The Doppler shift of prediction and the rate of change of Doppler shift are regulated the frequency of the local carrier of local oscillator 306 generations.As previously mentioned, radio-frequency front-end 210 will be converted to intermediate-freuqncy signal from the gps signal that satellite receives in described particular moment.Each integrator 300 is carried out the serial correlation computing with navigation data, local carrier and the local C/A sign indicating number of intermediate-freuqncy signal and prediction, realization is to the intermediate-freuqncy signal continuous integration of length at the fixed time, as the integral time in 1 second, obtain the cross correlation value of intermediate-freuqncy signal and local C/A sign indicating number.Intermediate-freuqncy signal is carried out the continuous integration in 1 second, can obtain-sensitivity of 160dBm.At integrator 300-0, the continuous integration computing comprises the navigation data that intermediate-freuqncy signal be multiply by prediction, removes the navigation data in the intermediate-freuqncy signal; Intermediate-freuqncy signal, local carrier and local C/A sign indicating number behind the removal navigation data are carried out continuous integration.The continuous integration operation result, promptly the cross correlation value of intermediate-freuqncy signal and local C/A sign indicating number then is sent to search module 308.Search module 308 judges whether the continuous integration operation result exceeds a predetermined threshold, judges whether to capture gps signal and finds specific Doppler shift and the phase shift of C/A sign indicating number.In the present embodiment, for finding the starting point of C/A sign indicating number,, the C/A sign indicating number is offset 1/2 chip for the search of each C/A sign indicating number.At integrator 300-1, carry out similar related operation, the different C/A sign indicating numbers of just delivering to integrator 300-1 are offset 1/2 chip.Offset module 310 is used for the C/A sign indicating number is offset 1/2 chip.As previously mentioned, a C/A sign indicating number cycle comprises 1023 chips.Therefore, for certain frequency, the C/A code phase search of finishing the whole cycle needs 2046 continuous integration computings.Will be appreciated that the present invention is intended to finish the continuous integration to the intermediate frequency Chief Signal Boatswain time by removing the navigation data in the intermediate-freuqncy signal, realize the location of GPS receiver under feeble signal environment such as indoor.In to C/A code searching process, each skew to the C/A sign indicating number is not limited to 1/2 chip in the present embodiment, also can adopt side-play amounts such as 1/4 chip, 1 chip.Like this, the number of integrator also changes thereupon.
If search module 308 confirms to capture gps signal, for example the frequency error of carrier wave is in 1Hz, the C/A code phase error is 1/2 chip, tracking module 224 enters tracking mode, make local C/A sign indicating number and local carrier follow the tracks of the C/A sign indicating number in the gps signal and the variation of carrier wave, thereby obtain phase shift of accurate C/A sign indicating number and Doppler shift.Be the structured flowchart of the tracking module 224 of one embodiment of the invention as shown in Figure 5.Tracking module 224 follows the tracks of the result that catches of trapping module 222 outputs of gps signal (intermediate-freuqncy signal) as initial C/A sign indicating number phase shift and Doppler shift.Usually, tracking module 224 comprises carrier tracking loop and C/A code tracking loop, respectively carrier wave in the gps signal and C/A sign indicating number is carried out real-time follow-up.The C/A code tracking loop comprises integration module 402, phase detector 404, wave filter 406, PRN yardage word control generator (NCO) 408, PRN sign indicating number generator 410 and controller 412.According to the C/A sign indicating number phase shift of trapping module 222 outputs, controller 412 control PRN sign indicating number NCO 408 make PRN sign indicating number generator 410 produce a local C/A sign indicating number, and the intermediate-freuqncy signal of this this locality C/A sign indicating number and input is carried out integration in integration module 402.The output of integration module 402 is through the processing of phase detector 404 and wave filter 406, adjust PRN sign indicating number NCO 408 and regulate the local C/A sign indicating number that PRN sign indicating number generator 410 produces, make the phase place of local C/A sign indicating number and the C/A code phase in the gps signal keep homophase to produce a control signal.The present invention does not need to start carrier tracking loop, but utilizes the rate of change of Doppler shift to follow the tracks of carrier wave, obtains accurate Doppler shift value.The Doppler shift of gps signal can obtain according to following formula: f
N+1=f
n+ k * t; F wherein
nBe Doppler shift sometime, f
N+1Be and f
nInterval time t this Doppler shift constantly, k is the effective rate of change of Doppler shift in time interval t of assistant base station 206 predictions.In the starting stage of following the tracks of, utilize the rate of change of the Doppler shift of the Doppler shift of trapping module 222 outputs and the prediction that assistant base station 206 provides to follow the tracks of carrier wave.After through one short period, then the rate of change of the Doppler shift of assistant base station 206 predictions and Doppler shift is offered controller 412 and follow the tracks of carrier wave by software arrangements interface 416, wherein this time is depended on the speed of software arrangements.Carrier wave numerically-controlled oscillator (NCO) 412 be based on the rate of change of Doppler shift and Doppler shift, produce with gps signal in the local signal of carrier synchronization.After the tracking of finishing gps signal, obtain phase shift of accurate C/A sign indicating number and Doppler shift.
Refer again to Fig. 3, the post-processing module 226 of GPS receiver 204 receives the navigation data of prediction and the phase shift of C/A sign indicating number and the Doppler shift of tracking module 224 outputs.The navigation data of 226 pairs of predictions of post-processing module is finished after the frame synchronization, and the navigation data of decoding prediction extracts co-ordinates of satellite.In another embodiment of the present invention, the navigation data of 206 pairs of predictions of assistant base station is decoded and is obtained co-ordinates of satellite, directly sends to position computation module 228.In addition, because co-ordinates of satellite is the function of current time, therefore, in yet another embodiment of the present invention, the value of current time accurately that provides according to the RTC232 or 244 of receiver 204 or assistant base station 206 and the satellite ephemeris of receiver 204 or assistant base station 206 storages also can obtain the coordinate of satellite at current time.
According to positioning equation
Position computation module 228 can calculate the position of GPS receiver 204.In the above-mentioned equation, x
i, y
i, z
iThe coordinate of representing i satellite; X, y, z represent the position coordinates of the GPS receiver 204 that needs obtain; C is the light velocity; Δ t represents the clock correction of the local clock and the satellite clock of GPS receiver 204; n
bRepresent the time delay of one of them Satellite GPS signal to GPS receiver 204; τ
CdiRepresent the phase shift of the C/A sign indicating number of corresponding i satellite-signal; Δ T
iRepresent i Satellite GPS signal to GPS receiver 204 with respect to n
bMistiming.If with the Δ t+n in the above-mentioned equation
bRegard a unknown number X as, as long as know the position coordinates and the τ of four satellites
CdiWith Δ T
i, just can calculate the position of receiver.As mentioned above, the navigation data in the gps signal of certain satellites transmits of prediction is decoded just can obtain the position coordinates of this satellite.After capturing the gps signal of certain satellites transmits, just can obtain the C/A sign indicating number phase shift τ of this satellite-signal
CdiReceive the timestamp (Time Stamp) of corresponding gps signal according to the RTC 232 of receiver 204, can obtain the mistiming Δ T that different satellite-signals arrive GPS receivers 204
i
In another embodiment of the present invention, if the real-time clock 232 of GPS receiver 204 has been calibrated, be that GPS receiver 204 had carried out one-time positioning, and preceding once start has been received from the complete data of a frame of AGPS assistant base station 206, start next time can not provide supplementary to 206 applications of AGPS assistant base station, utilize the effective historical supplementary of oneself preserving, the supplementarys such as navigation data in the gps signal that receiver 204 own predictions will receive.Here " effective historical supplementary " is meant that the complete data of a frame that GPS receiver 204 is received from AGPS assistant base station 206 all were effective in 2 hours.Therefore, to adopt the AGPS auxiliary mode still be receiver realizes the location of GPS receiver 204 under feeble signal environment such as indoor from auxiliary mode, need confirm whether preserve effective historical supplementary in the GPS receiver 204 when start.If there is effective historical supplementary, receiver 204 oneself is predicted supplementary.If there is no effective historical supplementary provides supplementary to 206 applications of AGPS assistant base station.
Fig. 6 is the process flow diagram of GPS receiver 204 position fixing processs of one embodiment of the invention.GPS receiver 204 supports unit (Stand-alone) patterns, from the location of auxiliary mode and AGPS auxiliary mode.In step 500, begin to start GPS receiver 204.Receiver 204 enters traditional single cpu mode in step 502 and catches the Satellite GPS signal.In step 504, judge whether that success captures at least four Satellite GPS signals.If the judgement acquisition success enters tracking mode in step 506, start code tracking loop and carrier tracking loop gps signal is followed the tracks of, obtain phase shift of accurate C/A sign indicating number and Doppler shift.In step 508, whether the loop of monitoring code tracking loop and carrier tracking loop losing lock.If judge not losing lock of loop, make bit synchronous in step 510 and handle, realize demodulation to navigation data in the gps signal.In step 512, whether need to confirm satellite ephemeris.If confirming needs satellite ephemeris, obtain satellite ephemeris in step 514 decoded navigation data.In step 516, according to the co-ordinates of satellite in the satellite ephemeris with catch the C/A sign indicating number phase shift that obtains, calculate the position of GPS receiver 204.Capture at least four Satellite GPS signals if step 504 is judged to fail under single cpu mode, then whether receiver 204 oneself preserves effective historical supplementary in step 518 search.If there is effective historical supplementary, GPS receiver 204 starts from auxiliary mode in step 520, utilize this effective historical supplementary, predict that it will be from the rate of change of the navigation data the gps signal that satellite receives, Doppler shift and Doppler shift.In step 522, utilize the supplementarys such as navigation data of prediction to catch the Satellite GPS signal.In step 524, judge whether that success captures at least four Satellite GPS signals.If the judgement acquisition success enters tracking mode in step 526, start code tracking loop gps signal is followed the tracks of, obtain the phase shift of accurate C/A sign indicating number; Need not to start carrier tracking loop, utilize the rate of change of Doppler shift to follow the tracks of carrier wave.In step 528, whether the loop of monitoring code tracking loop losing lock.If judge not losing lock of loop, carry out aforesaid step 512,514 and 516.If GPS receiver 204 does not search in step 518 and oneself preserves effective historical supplementary, then start the AGPS auxiliary mode in step 530.The rate of change of navigation data, Doppler shift and Doppler shift that supplementary, supplementary comprise prediction is provided to assistant base station 206 application in step 532.Utilize supplementary, catch the Satellite GPS signal in step 522.Then carry out aforesaid step 526,528,512 and 516.Each above-mentioned step can be carried out a series of machine readable instructions by the arithmetic section of for example computing equipment and realize.
Here term of Cai Yonging and form of presentation just are used for describing, and should not be limited to these terms and statement.Use these terms and statement and do not mean that the equivalent features of getting rid of any signal and description (or wherein part), will be appreciated that the various modifications that may exist also should be included in the claim scope.Other modifications, variation and replacement also may exist.Accordingly, claim should be considered as covering all these equivalents.
Claims (26)
1. one kind is suitable for the method for utilizing gps signal to position to the GPS receiver under the feeble signal environment, gps signal comprises carrier wave, Pseudo-Random Noise Code and navigation data, described Pseudo-Random Noise Code and navigation data are modulated on the carrier wave, the GPS receiver produces local carrier and local Pseudo-Random Noise Code, it is characterized in that, said method comprising the steps of:
Navigation data in the gps signal is predicted;
Receive described gps signal;
The gps signal that receives is converted to intermediate-freuqncy signal;
Navigation data, local carrier and the local Pseudo-Random Noise Code of intermediate-freuqncy signal and prediction are carried out the serial correlation computing;
Obtain the phase shift of Pseudo-Random Noise Code; With
Based on the navigation data of prediction and the phase shift of Pseudo-Random Noise Code, calculate the position of GPS receiver.
2. method according to claim 1 is characterized in that, and is further comprising the steps of in described prediction steps:
The Doppler shift of prediction carrier wave and the rate of change of Doppler shift; With
Based on the Doppler shift of prediction and the rate of change of Doppler shift, adjust the frequency of local carrier in the serial correlation calculating process.
3. the method for stating according to claim 2 is characterized in that, after described execution serial correlation calculation step, utilizes the Doppler shift of prediction and the rate of change of Doppler shift to follow the tracks of carrier wave.
4. method according to claim 1 is characterized in that, described gps signal is the gps signal that the GPS receiver will receive from gps satellite in a certain particular moment.
5. method according to claim 4 is characterized in that, also comprises based on described a certain particular moment, determines to start the moment of described serial correlation computing.
6. method according to claim 4 is characterized in that, also comprises described GPS receiver and gps satellite are done the clock synchronization processing, and this synchronous processing may further comprise the steps:
Prediction GPS receiver will be from the moment that the navigation data the gps signal that satellite receives and GPS receiver are received this gps signal;
All channel configurations of GPS receiver are become to catch the gps signal of described satellites transmits;
The navigation data that utilizes prediction is in the local reception time of each channel IT gps signal with the acquisition gps signal; With
Based on the local reception time of gps signal and the time of reception of prediction, proofread and correct the real-time clock of GPS receiver.
7. method according to claim 6 is characterized in that, the described gps signal of catching comprises with the step of local reception time of obtaining gps signal:
1) gps signal is converted to intermediate-freuqncy signal;
2) produce local carrier and local Pseudo-Random Noise Code;
3) with the starting point of the navigation data alignment intermediate-freuqncy signal of prediction;
4) navigation data, local carrier and the local Pseudo-Random Noise Code of intermediate-freuqncy signal and prediction are carried out the serial correlation computing;
5) phase place of the local Pseudo-Random Noise Code of skew;
6) repeating step 4) and 5), up to from the related operation result, searching a peak value;
7) if do not search peak value, with the navigation data of prediction with respect to the starting point of intermediate-freuqncy signal skew a period of time;
8) repeating step 4) to 7), until searching a peak value; With
9) skew of the navigation data of the phase shift of the Pseudo-Random Noise Code when searching peak value and prediction obtains local reception time of gps signal.
8. method according to claim 1 is characterized in that the navigation data of described prediction was stored in the GPS receiver before the GPS receiver receives gps signal.
9. handle the method that the GPS receiver is located for one kind, the GPS receiver receives gps signal, and gps signal comprises carrier wave, Pseudo-Random Noise Code and navigation data, and described Pseudo-Random Noise Code and navigation data are modulated on the carrier wave, it is characterized in that, said method comprising the steps of:
1) catches gps signal;
2) judge the Satellite GPS signal that whether successfully captures predetermined quantity;
3) if judge acquisition success, the position that then begins the trace daemon of gps signal and calculate the GPS receiver;
4) if judge and to catch failure, whether the GPS receiver begins to search for oneself preserves effective historical supplementary;
5),, predict the navigation data that it will receive from satellite according to this effective historical supplementary if there is effective historical supplementary;
6), catch the Satellite GPS signal of predetermined quantity based on the navigation data of described prediction;
7) follow the tracks of gps signal that captures and the position of calculating the GPS receiver;
8) if there is no effective historical supplementary provides supplementary to the assistant base station application;
9) supplementary that provides based on described assistant base station is caught the Satellite GPS signal of predetermined quantity; With
10) follow the tracks of gps signal that captures and the position of calculating the GPS receiver.
10. method according to claim 9 is characterized in that, the trace daemon in the step 3) comprises startup pseudo noise code tracking loop and carrier tracking loop.
11. method according to claim 9 is characterized in that, further comprises the Doppler shift of predicting carrier wave and the rate of change of Doppler shift in the step 5).
12. method according to claim 11 is characterized in that, the tracking in the step 7) comprises startup pseudo noise code tracking loop, and the Doppler shift of described prediction and the rate of change of Doppler shift are followed the tracks of carrier wave.
13. method according to claim 9 is characterized in that, catches gps signal in the step 6) and may further comprise the steps:
Reception is from the Satellite GPS signal and be converted into intermediate-freuqncy signal;
Produce local carrier and local Pseudo-Random Noise Code; With
Navigation data, local carrier and the local Pseudo-Random Noise Code of described intermediate-freuqncy signal and described prediction are carried out the serial correlation computing.
14. method according to claim 9 is characterized in that, the supplementary in the step 8) comprises navigation data and the Doppler shift of carrier wave and the rate of change of Doppler shift that the GPS receiver of assistant base station prediction will receive.
15. method according to claim 14 is characterized in that, catches the Satellite GPS signal in the step 9) and may further comprise the steps:
Reception is from the Satellite GPS signal and be converted into intermediate-freuqncy signal;
Produce local carrier and local Pseudo-Random Noise Code; With
Navigation data, local carrier and the local Pseudo-Random Noise Code of described intermediate-freuqncy signal and described prediction are carried out the serial correlation computing.
16. method according to claim 15 is characterized in that, the trace daemon in the step 10) comprises startup pseudo noise code tracking loop, and the Doppler shift of the carrier wave of described prediction and the rate of change of Doppler shift are followed the tracks of carrier wave.
17. method according to claim 9 is characterized in that, comprises in the step 9) described GPS receiver and described assistant base station are done the clock synchronization processing.
18. method according to claim 17 is characterized in that, described clock synchronization is handled and be may further comprise the steps:
1) assistant base station and GPS receiver receive the same frame navigation data of satellites transmits, write down the local reception time separately respectively;
2) assistant base station sends to the GPS receiver with its navigation data that receives and corresponding local reception time;
3) assistant base station is revised the real-time clock of oneself according to its navigation data that receives and corresponding local reception time; With
4) the GPS receiver compares the local zone time of assistant base station reception navigation data and oneself receives the local zone time of navigation data, proofreaies and correct the real-time clock of oneself.
19. method according to claim 18, it is characterized in that, described step 3) comprises according to the pseudorange between assistant base station and the satellite, obtain the transmission time difference of satellite to assistant base station, the satellites transmits time that comprises based on this transmission time difference and navigation data, obtain a time of reception, revise the real-time clock of assistant base station based on the local reception time of this time of reception and assistant base station.
20. method according to claim 19, it is characterized in that, described step 4) comprises that the GPS receiver is according to the satellites transmits time that comprises in described transmission time difference and the navigation data that oneself receives, obtain a time of reception, based on the local reception time of this time of reception and GPS receiver, proofread and correct the real-time clock of oneself.
21. method of in the GPS receiver, handling gps signal, gps signal comprises carrier wave, Pseudo-Random Noise Code and navigation data, described Pseudo-Random Noise Code and navigation data are modulated on the carrier wave, the GPS receiver produces local carrier and local Pseudo-Random Noise Code, it is characterized in that, said method comprising the steps of:
Produce the navigation data of prediction;
Gps signal is converted to intermediate-freuqncy signal; With
Navigation data, local carrier and the local Pseudo-Random Noise Code of intermediate-freuqncy signal and prediction are carried out the serial correlation computing.
22. method according to claim 21 is characterized in that, and is further comprising the steps of:
Produce the Doppler shift of prediction and the rate of change of Doppler shift; With
Based on the Doppler shift of prediction and the rate of change of Doppler shift, adjust the frequency of local carrier in the serial correlation calculating process.
23. method according to claim 22 is characterized in that, after carrying out the serial correlation computing, the Doppler shift of described prediction and the rate of change of Doppler shift are followed the tracks of carrier wave.
24. a system that realizes GPS location under the feeble signal environment is characterized in that described system comprises:
Assistant base station, this assistant base station comprises prediction module, its dope receiver will be in a certain particular moment the navigation data from the gps signal that satellite receives; With
The GPS receiver, it comprises radio-frequency front-end and baseband signal processing unit, baseband signal processing unit comprises trapping module and position computation module, radio-frequency front-end received from described Satellite GPS signal and is converted into intermediate-freuqncy signal in described a certain particular moment, trapping module is with the navigation data of intermediate-freuqncy signal and assistant base station prediction, local carrier that the GPS receiver produces and local Pseudo-Random Noise Code are carried out the serial correlation computing, obtain the phase shift of Pseudo-Random Noise Code, position computation module is calculated the position of GPS receiver based on the navigation data of prediction and the phase shift of Pseudo-Random Noise Code.
25. system according to claim 24 is characterized in that, described baseband signal processing unit comprises makes the clock synchronization unit that clock synchronization is handled with GPS receiver and satellite.
26. system according to claim 25 is characterized in that, described baseband signal processing unit comprises the real-time clock of indicating the described initial moment of serial correlation computing.
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