Method in TD-SCDMA wireless telecommunication system calibrating GPS standard time
Technical field
The present invention relates to the TD-SCDMA field of wireless communication, relate in particular to method in TD-SCDMA wireless telecommunication system calibrating GPS standard time.
Background technology
GPS is a kind of satellite-based navigation system, and it is designed and be subjected to the control of US military at first by US military, can freely use for anyone.This system is made up of 24 satellites that move on 6 intermediate annular tracks, and satellite rings was around 12 hours around of one week of track operation.Each satellite constantly sends about the position of current time, all satellites and some related data information as almanac (almanac) and ephemeris (ephemeris).Gps receiver uses this information to calculate distance between himself and the satellite.For determining the position, gps receiver must receive the signal from least three satellites.
Primary positioning time (Time to First Fix, TTFF) characterize gps receiver and locate the required time for the first time, TTFF is decided by the receiving sensitivity of receiver to a great extent, and the intensity of the quantity of visible satellite, each satellite-signal, satellite on high distribution and receiver to the visual angle of sky.In a kind of hostile environment, the more weak city high rise building gap of signal or indoor for example needs the time calculating locations of a few minutes under some situation.This is unacceptable for local service (LBS) or urgent call (E911), and these situations need a kind of acquisition time faster.For this reason, people have developed auxiliary type GPS (A-GPS) and have solved TTFF problem under the adverse environment.
The E911 mandatory requirement that the exploitation of A-GPS partly is subjected to FCC (FCC) can provide cellular location to promote to emergency caller.The purpose of A-GPS is or improves TTFF, perhaps makes the location computing become possibility when it can not improve TTFF.
Different notions and solution have been developed in the past several years under this keyword of A-GPS, these different notions can be divided into support type GPS (Aided GPS) and auxiliary type GPS two classes (Assisted GPS).
Support type GPS improves TTFF by send almanac, ephemeris, rough position and time on the mobile network.This support type data can user level (user plane) last in control aspect (control plane) or the mobile network go up transmission.The computing great majority of the position of support type GPS occur on the mobile device.
Auxiliary type GPS makes and adopts quick TTFF calculating location to become possibility.For realizing this point, utilize the extraneous information as time synchronized, more accurate location, Doppler and frequency to be used for determining the position.This extraneous information can obtain by the infrastructure device of using mobile network's control aspect, and the mechanism as AFLT (AFLT) is used to determine the position of mobile device.Here, signal sends from mobile device, is received and measures by several mobile base stations.(based on mobile device) can take place in the calculating of position in mobile device, perhaps take place on mobile network's server (based on network).
Auxiliary type GPS solution based on mobile device receives extra assistant GPS data by the mobile network, but calculates at the enterprising line position of mobile device.LBS or the E911 service that this means must obtain current position from mobile device.
Adopt based on network auxiliary type GPS solution, mobile device sends the GPS secondary server of original gps data in the mobile network.This webserver can utilize and directly come the extra assistant GPS information of automatic network to come calculating location.After calculating, position data is sent to receiver.LBS or E911 service be the location database of access web server directly.
The benefit of A-GPS is to improve TTFF, increase sensitivity and make the availability maximization, exist these advantages to be because receiver no longer must be downloaded and be decoded from the navigation data of gps satellite, receiver can use more time and disposal ability to follow the tracks of gps signal.
The location Calculation of A-GPS can be divided into MS-Based mode and MS-Assisted mode.In the MS-Based mode, calculate and finish by terminal; And in the MS-Assisted mode, location Calculation is finished based on the measurement data that SET provides by network.Two kinds of method for calculating and locating cut both ways: the advantage of MS-Assisted be to terminal require low, but have time delay big, be not suitable for the shortcomings such as location under the situation of running at high speed.Comparatively speaking, the advantage of MS-Based method is that network burden is little and the location time delay is little; Be fit to the continuous location situation in the short time; Under network can not provide auxiliary situation, can use from the GPS of tool function and locate, thereby the reliability height; Need not core network under this mode and do any improvement, cost is lower.In general, the MS-Based mode is more desirable locate mode.
In the positioning calculation process for GPS, if determine to understand the local GPS standard time of GPS receiver, this can accurately measure the accurate time delay of each satellite-signal arrival receiver in the gps system.Under this prerequisite, can improve the receiving sensitivity of GPS receiver effectively and reduce primary positioning time.Yet the GPS standard time that is obtained in present A-GPS is relatively more rough, not accurate enough mostly.
In recent years, along with the increase of user's request, the increasingly mature development for mobile positioning technique that mobile positioning technique receives increasing concern, particularly 3G technology provides support.In the network of 2G or 2.5G, owing to be subjected to the restriction of network transfer speeds, the application of hi-Fix technology (A-GPS) is limited to, and 3G network can provide the high-speed radio download function, and this just provides more wide development space for mobile location service.
The TD-SCDMA wireless communication system is the autonomous 3G standard of formulating of China.The key technology of TD-SCDMA is exactly a synchronization CDMA, and promptly each terminal signaling of up link is synchronous fully at base-station demodulator.Like this, each code channel that uses orthogonal intersection quadrature fully just when despreading, mutual unlikely generation multiple access interference has solved the capacity of cdma system greatly.For realizing synchronization CDMA, must solve synchronous subject matters such as detection, foundation and maintenance, this also is one of key technology of native system.But because the position of each user terminal in cell coverage area can change, even carry out in the process in communication, the user can also move with very high-speed.Because electric wave will cause synchronous variation in the variation in the propagation time from the base station to the user terminal.If consider the influence of multipath transmisstion again, this will be more difficult synchronously, the difficult problem place that Here it is realizes synchronization CDMA.In synchronous CDMA system, synchronous detection is to obtain by asking relevant mode with software.In the wireless base station, we carry out 8 times the sampling of crossing to the signal from user terminal that receives, and promptly in the baseband signal that demodulates, each chip (Chip) equal time are got 8 sample values, ask relevant with the sample value that this obtains then.When relevant peaks does not reach desirable value, search forward or backward again, till obtaining to receive the synchronous starting point of signal.Obtain like this between the synchronous starting point of the synchronous starting point of this received frame and it and expectation apart from SS (its unit be the interval of taking a sample, the i.e. integral multiple of 1/8Chip) at every turn.Because at any time, the base station can only receive the access request of a terminal constantly at SYNC1; And have only a terminal sending this signal constantly at SYNC2, all the other terminals crack at this moment are empty slot (EMPTY), so do not have the interference from other-end in this sub-district, have guaranteed the accuracy of synchronous detection.
The TD-SCDMA system adopts TDD duplex technology and FDMA/TDMA/CDMA multi-access mode, in order to reduce interferences, to improve power system capacity, requires between each base station, synchronous between base station and the terminal.Simultaneous techniques in the TD-SCDMA system mainly is made up of two parts, one be between the base station synchronously; Another is the uplink synchronous technology between travelling carriage.Adopt synchronously GPS or other technology realize between the base station synchronously, promptly all signal of base station comprise that System Frame Number (SFN) is consistent in the synchro system.
Utilize synchro system synchronization among base stations, each base station location accurately all to have the characteristics of high-precision GPS receiver in known and each base station, obtain the GPS standard time and pass to synchronous terminal equipment by the base station, can improve the receiving sensitivity of the A-GPS receiver in the terminal equipment effectively and reduce primary positioning time.Yet owing to have certain distance between user terminal and the base station, the certain propagation delay time of the signal demand of base station just can arrive user terminal, so life period is poor between the frame head of the base station of the frame head of the radio frames that subscriber terminal side obtains and reality.Like this, will there be certain error in the end side GPS standard time of the GPS standard time of base station side with reality, this will influence the accuracy of the GPS standard time of user terminal acquisition, and further influence the receiving sensitivity and the primary positioning time of the A-GPS receiver in the terminal equipment.
Summary of the invention
Technical problem to be solved by this invention provides a kind of method in TD-SCDMA wireless telecommunication system calibrating GPS standard time, can calibrate the propagation delay time of base station signal, to obtain accurate GPS standard time more on user terminal.
The present invention solves the problems of the technologies described above the technical scheme that adopts to provide a kind of method in TD-SCDMA wireless telecommunication system calibrating GPS standard time, may further comprise the steps:
A. portable terminal to be positioned obtains the base station GPS standard time;
B. radio network controller is from base station picked up signal Loop Round Trip Time, and it is poor to obtain to receive launch time from portable terminal, and signal calculated propagation delay time in view of the above;
C. the signalling propagation delay time is given corresponding mobile terminal under the radio network controller;
D. portable terminal is according to the GPS standard time and the signal propagation delay time computing terminal GPS standard time of base station.
In step b, the computational methods of signal propagation delay time are: T
RA=(T
Loop-T
Rx-Tx)/2, wherein T
RABe signal propagation delay time, T
LoopBe signal Loop Round Trip Time, T
Rx-TxPoor for receiving launch time.
In steps d, the computational methods of terminal GPS standard time are: T
GPS_SD_UE=T
GPS_SD_BS-T
RA, T wherein
GPS_SD_UEBe the terminal GPS standard time, be base station GPS standard time, T
RABe the signal propagation delay time.
Above-mentioned signal Loop Round Trip Time is to be calculated in position fixing process and obtained by the base station, and above-mentioned reception difference launch time is to be calculated in position fixing process and obtained by portable terminal.
Above-mentioned steps a further may further comprise the steps: each base station of a1. receives gps satellite signal respectively, obtains the absolute GPS standard time of TD-SCDMA system clock when determining System Frame Number; A2. each base station reports the measured absolute GPS standard time to give radio network controller respectively; A3. radio network controller is stored the absolute GPS standard time that each base station reports; A4. the radio network controller notice needs the absolute GPS standard time of system clock when determining System Frame Number of the sub-district, portable terminal place of location; A5. portable terminal calculates according to current System Frame Number and obtains base station standard gps time.
Wherein, step a1 is included in the following steps of carrying out in the base station: determine current System Frame Number; The information of GPS receiver demodulation gps satellite obtains GPS standard time information; Calculate the synchro system clock in the time difference of determining between System Frame Number and current System Frame Number: △ T
SFN=-T
Frame* (SFN-SFN
SD), T wherein
GPSBe GPS standard time, T
FrameBe the synchro system frame length, SFN is current System Frame Number, SFN
SDBe synchro system clock fixed system frame number really; And the calculating synchro system absolute GPS standard time of clock when determining System Frame Number: T
GPS SD=T
GPS+ △ T
SFN
Wherein, step a5 is included in the following steps that portable terminal is carried out: the absolute GPS standard time of the synchro system clock that the demodulation radio network controller issues when determining System Frame Number; Demodulation base station system signal obtains current System Frame Number; And calculation base station gps system standard time: T '
GPS=T
GPS SD+ T
Frame* (SFN '-SFN
SD), T wherein
FrameBe the synchro system frame length, SFN ' is current System Frame Number, SFN
SDBe synchro system clock fixed system frame number really.
The present invention also provides another kind of method in TD-SCDMA wireless telecommunication system calibrating GPS standard time, may further comprise the steps:
A. portable terminal to be positioned obtains the base station GPS standard time;
B. radio network controller is from base station picked up signal Loop Round Trip Time, and is handed down to this portable terminal;
C. portable terminal is according to measuring reception difference launch time that obtains and this signal Loop Round Trip Time that receives, and calculation base station is to the signal propagation delay time of this portable terminal;
D. portable terminal is according to the GPS standard time and the signal propagation delay time computing terminal GPS standard time of base station.
In step c, the computational methods of signal propagation delay time are: T
RA=(T
Loop-T
Rx-Tx)/2, wherein T
RABe signal propagation delay time, T
LoopBe signal Loop Round Trip Time, T
Rx-TxPoor for receiving launch time.
In steps d, the computational methods of terminal GPS standard time are: T
GPS_SD_UE=T
GPS_SD_BS-T
RA, T wherein
GPS_SD_UEBe the terminal GPS standard time, be base station GPS standard time, T
RABe the signal propagation delay time.
Therefore, the present invention is by base station signal propagation delay time information that transmit to measure and to the correction of base station side GPS standard time of the acquisition of portable terminal, can on portable terminal, obtain accurate GPS standard time more, thereby improve the receiving sensitivity of the A-GPS receiver in the terminal equipment effectively and reduce primary positioning time.
Description of drawings
For above-mentioned purpose of the present invention, feature and advantage can be become apparent, below in conjunction with accompanying drawing the specific embodiment of the present invention is elaborated, wherein:
Fig. 1 is the time relationship schematic diagram that the base station signal propagation delay time is measured.
Fig. 2 is the method flow diagram of the calibration GPS standard time of one embodiment of the invention.
Fig. 3 is the flow chart of steps that terminal obtains the GPS standard time among Fig. 2.
Fig. 4 is the flow chart of steps of carrying out in the base station among Fig. 3.
Fig. 5 is the flow chart of steps of carrying out at portable terminal among Fig. 3.
Fig. 6 is a TD-SCDMA system schematic with GPS positioning function.
Fig. 7 is the structural representation of base station among Fig. 6.
Fig. 8 is the structural representation of portable terminal among Fig. 6.
Fig. 9 is the method flow diagram of the calibration GPS standard time of another embodiment of the present invention.
Embodiment
As shown in Figure 6, include a plurality of base stations 10, portable terminal 30 and radio network controller 20 etc. in the TD-SCDMA wireless telecommunication system, wherein comprise GPS receiver (figure do not show) in each base station 10 to receive gps satellite signal, realize between each base station synchronously.In addition, have the A-GPS receiver in the portable terminal, therefore can be used to carry out the GPS location from the relevant information of wireless network and satellite.
As is known to the person skilled in the art, in position fixing process, signal transmission as shown in Figure 1 will inevitably be arranged between base station and the portable terminal, at first, base station transmit signals is through propagation delay time T
RA, portable terminal receives signal, considers actual transmission time delay (the emission time of reception that is terminal is poor), and terminal is through T
Rx-TxAfter transmit, after this, again through propagation delay time T
RA, the base station receives signal.In said process, the difference between real base station received signal and the base station transmit signals is called signal winding time T
LoopCan get propagation delay time according to time delay relation shown in Figure 1:
T
RA=(T
Loop-T
Rx-Tx)/2.............(1)
After the generation principle of having understood above-mentioned propagation delay time and computational process, the method for the calibration GPS standard time of one embodiment of the invention is described below.Please consult shown in Figure 3ly in conjunction with Fig. 2, the flow process of this method is as follows.
In step 201, portable terminal 30 to be positioned obtains base station GPS standard time T
GPS_SD_BS, process is as follows: see also shown in Figure 3ly, in step 301, each base station 10 receives gps satellite signal respectively, obtains the absolute GPS standard time of TD-SCDMA system clock when determining System Frame Number (is 0 as frame number); Subsequently, in step 302, each base station 10 reports the measured absolute GPS standard time to give radio network controller (RNC) respectively; The absolute GPS standard time (step 303) that radio network controller 20 each base station of storage report; In step 304, the absolute GPS standard time of the system clock of the sub-district, portable terminal 101 place that radio network controller 20 need be located by signaling when determining System Frame Number; At last, execution in step 305, portable terminal calculates the gps time of current standard according to current System Frame Number.
Wherein, see also shown in Figure 4ly, step 301 further is included in the following steps of carrying out in the base station: at first, in step 3011, current system frame number SFN is determined in the base station, simultaneously, execution in step 3012, the information of the GPS receiver demodulation gps satellite in the base station obtains GPS standard time information T
GPSSubsequently, execution in step 3013 is calculated the synchro system clock in the time difference of determining between System Frame Number and the current System Frame Number: △ T
SFN=-T
Frame* (SFN-SFN
SD), T wherein
FrameBe synchro system frame length, SFN
SDBe synchro system clock fixed system frame number (is 0 as frame number) really, that is pairing frame number of absolute GPS standard time; Last execution in step 3014, calculate the absolute GPS standard time of synchro system clock when determining System Frame Number:
T
GPS?SD=T
GPS+△T
SFN=T
GPS-T
frame*(SFN-SFN
SD)..........(3)
Be the promptness that guarantees that the absolute GPS standard time measures, step 301~303rd, execution periodically circulates.
In step 304, radio network controller can issue the absolute GPS standard time by broadcast channel, also can be based on the request of portable terminal, provides the absolute GPS standard time by the portable terminal of dedicated channel to the needs location.
Next see also shown in Figure 5ly, step 305 further is included in the following steps that portable terminal is carried out: at first, in step 3051, the absolute GPS standard time T of the synchro system clock that demodulation radio network controller 20 issues when determining System Frame Number
GPS SDSecondly, execution in step 3052, demodulation base station system signal obtains current system frame number SFN '; Afterwards, execution in step 3053, calculate the Current GPS system standard time:
T’
GPS=T
GPS?SD+T
frame*(SFN’-SFN
SD)..........(4)
T wherein
FrameBe the synchro system frame length, SFN ' is a System Frame Number, SFN
SDBe synchro system clock fixed system frame number really.
T '
GPSReality is base station side GPS standard time T
GPS_SD_BS, because therefore the existence of propagation delay time need proofread and correct in step step 202~204.
In step 202, radio network controller (RNC) 20 be 10 picked up signal Loop Round Trip Time T from the base station
Loop, and from portable terminal 30 acquisition reception difference launch time T
Rx-Tx, and according to formula (1) signal calculated propagation delay time T
RASubsequently, execution in step 203, RNC 20 issues the signal propagation delay time T that calculates gained
RAGive corresponding portable terminal to be positioned 30.At last, in step 204, portable terminal 30 is according to the GPS standard time T of base station
GPS_SD_BSWith signal propagation delay time T
RAThe computing terminal GPS standard time, computing formula is as follows:
T
GPS_SD_UE=T
GPS_SD_BS-T
RA..........(2)
In above-mentioned steps 202, signal loopback time T
LoopAnd reception difference launch time T
Rx-TxCan calculate behind the signal transduction process in experience position fixing process once shown in Figure 1 by base station 10 and portable terminal 30 respectively and get, and report RNC 20 according to the requirement of TD-SCDMA.Step 202 can be carried out in execution in step 201.
Fig. 6~Fig. 8 illustrates the TD-SCDMA wireless communication system of realizing said method.Each TD-SCDMA base station 10 receives gps satellite signal respectively, obtains the absolute GPS standard time of TD-SCDMA system clock when determining System Frame Number, and reports the measured absolute GPS standard time to give RNC 20 respectively; As shown in Figure 7, in each base station 10, GPS receiver 11 obtains GPS standard time information T in order to the information of demodulation gps satellite
GPSClock board 12 is determined current system frame number SFN.Computing unit 13 receives this GPS standard time and current system frame number SFN, calculates the absolute GPS standard time of synchro system clock when determining System Frame Number according to calculating formula (3).
According to the requirement of calculating formula (3), computing unit 13 further comprises first adder 130, second adder 132, multiplier 134.GPS receiver 11 is finished Current Standard gps time T
GPSSurveying work is exported to first adder 130 with measured value.The clock board 12 of base station provides current SFN and frame head time, exports current SFN and gives second adder 132, and second adder 132 is with current SFN and standard SFN (SFN
SD) subtract each other poor, export to multiplier 134.The difference that multiplier 134 will be imported multiply by the frame length (T of TD-SCDMA
Frame) acquisition relative time △ T
SFN, export to first adder 130.First adder 130 is with standard gps time T
GPSDeduct relative time △ T
SFNAbsolute GPS standard time T when obtaining System Frame Number
GPS SD,, provide RNC 20 to use as system's output.
The absolute GPS standard time that radio network controller 20 each base station 10 of storage report, and notice needs the absolute GPS standard time of system clock when determining System Frame Number of the sub-district, portable terminal 30 place of location.Radio network controller 20 can issue the absolute GPS standard time by broadcast channel; Certainly, radio network controller 20 also can be based on the request of portable terminal 30, provides absolute GPS standard time T by the portable terminal 30 of dedicated channel to the needs location
GPS SD
Portable terminal 30 calculates the gps time T ' of current standard according to current System Frame Number
GPSSee also shown in Figure 8, in portable terminal, the absolute GPS standard time T of the synchro system clock that TD-SCDMA receiver 31 demodulation RNC 20 issue when determining System Frame Number
GPS SD, and demodulation base station system signal obtains current system frame number SFN '.Computing unit 32 calculates the Current GPS system standard time according to calculating formula (4).
According to the requirement of calculating formula (4), computing unit 32 further comprises first adder 320, second adder 322 and multiplier 324.TD-SCDMA receiver 31 is finished RNC message demodulation function, and the absolute GPS standard time during with System Frame Number is exported to first adder 320.In addition, TD-SCDMA receiver 31 is finished the SFN demodulation function of its access base station 10, exports current System Frame Number (SFN ') and gives second adder 322.Second adder 322 is with current system frame number SFN ') and modular system frame number (SFN
SD) subtract each other poor, export to multiplier 324.The difference that multiplier 324 will be imported multiply by the frame length (T of TD-SCDMA
Frame) acquisition relative time (△ T
SFN), export to first adder 320.Absolute GPS standard time and the relative time addition of first adder 320 during with the modular system frame number obtains current standard gps time T '
GPS, this time is considered as base station GPS standard time T
GPS_SD_BSThrough the correction of the 3rd adder 326, obtain terminal GPS standard time T again
GPS_SD_UE
End side GPS standard time T after calibrating according to preceding method
GPS_SD_UEBe provided for A-GPS receiver 33, finish positioning function under network-assist information by A-GPS receiver 33.In addition, portable terminal 30 transmits gps signal measurement result or customer location estimated information to the centre of location 40.The centre of location 40 is finished the location estimation and/or the location information management function of the portable terminal that needs the location, and the positional information of the portable terminal 30 that needs the location is provided to position application platform 50 simultaneously.Position application platform 50 is finished the linkage function of positioning service and other external servers etc., and the positional information of the portable terminal 30 that needs the location outwards is provided, and signalings such as Location Request and location end are provided to the centre of location 40.
Fig. 9 is the method flow diagram of the calibration GPS standard time of another embodiment of the present invention.Please consult embodiment illustrated in fig. 9ly in conjunction with Fig. 6, step 201 is identical with step 201 shown in Figure 2, and its details is no longer narrated, and different is, in step 202 ', radio network controller 20 is 10 picked up signal Loop Round Trip Time T from the base station
Loop, and be handed down to portable terminal 30; Subsequently, in step 203 ', portable terminal 30 is according to measuring the reception difference launch time T that obtains
Rx-TxAnd the signal loopback time T that receives
Loop, calculation base station 10 is to the signal propagation delay time T of portable terminal 30
RA, computational methods such as above-mentioned calculating formula (1).At last, in step 204, portable terminal 30 is according to the GPS standard time and the signal propagation delay time computing terminal GPS standard time of base station 10.This step is identical with step 204 shown in Figure 2, therefore also no longer narration.
Therefore, the present invention is by base station signal propagation delay time information that transmit to measure and in the correction of portable terminal, can on portable terminal, obtain accurate GPS standard time more, thereby improve the receiving sensitivity of the A-GPS receiver in the terminal equipment effectively and reduce primary positioning time.
Though the present invention discloses as above with preferred embodiment; right its is not in order to qualification the present invention, any those skilled in the art, without departing from the spirit and scope of the present invention; when can doing a little modification and perfect, so protection scope of the present invention is when with being as the criterion that claims were defined.