CN101472330A - Transmission synchronization method based on time difference orientation - Google Patents

Abstract

The invention provides a method of synchronous transmission based on time difference location. The method comprises the following steps: a terminal sends a location calculation request to a serving base station (BS); the serving BS transmits a transmission location request to a service movable location centre SMLC; SMLC sends wireless pre-synchronization response to the BS and other corresponding auxiliary BSs, wherein, the response comprises an instruction of estimating synchronous mismatch parameters of each BS; SMLC calculates and obtains the mismatch parameters between related BS and GPS according to the estimation of synchronous mismatch parameters finished by each BS, and transmits mismatch difference values to the serving BS; the serving BS delivers the difference values to the terminal through an opening; SMLC sends indications to the serving BS and the auxiliary BS, and notifies the serving BS and the auxiliary BS of time slot location or signal form of scanning signals; and the serving BS and the auxiliary BS send the scanning signals to the terminal; and the terminal calculates the difference value and the location of the computer terminal according to the difference value.

Description

Transmission synchronization method based on the time difference location

Technical field

The present invention relates to mobile communication, particularly be used for the transmission synchronization method of time division multiplexing (TDD) system of OFDM (OFDM) based on the time difference location.

Background technology

In recent years, along with developing rapidly of cellular mobile communication technology, the cellular radio location technology more and more is subject to people's attention.

This mainly drives owing to the Compulsory Feature of government and the demand in market itself.FCC has issued that in October, 1996 wireless E-911 calls out the emergency service function, and its core is the longitude and latitude positional information that all mobile communications networks of requirement must provide emergency call user stage by stage.

1996 FCC (FCC) announced E-911 (Emergencycall ' 911 ') location requirement, wherein require before October 1 calendar year 2001, various wireless cellular networks must provide the positioning service of precision in 125m to the travelling carriage that sends the E-911 urgent call, and the probability that satisfies this positioning accuracy should be not less than 67%; And after calendar year 2001, provide higher positioning accuracy and three dimensional local information.Europe and Japan have also done corresponding requirement, show that it will be the basic function of cellular network indispensability from now on that the E-911 positioning service is provided.

At the concrete enforcement of E911 location requirement, the main major company in various countries all begins to formulate separately location embodiment with regard to GSM, IS-95CDMA and 3-G (Generation Three mobile communication system).Particularly 3GPP and 3GPP2 are upward more specific to the requirement of location, and this also is affirming cellular radio location market potential.On the other hand, mobile communication subscriber is urgent day by day to the demand of mobile location service.The cellular network wireless location technology can be obtained information such as its geographical position under travelling carriage is in the situation of idle condition or talking state, utilize the locating information of travelling carriage, operator can provide various value-added services for the user, as location circumstances information inquiry, emergency relief, intelligent transportation, ad distribution or the like, can also move simultaneously, the auxiliary data of maintenance and management as mobile communications network.

Fig. 1 has demonstrated the example of a wireless location system architecture.A positioning service provider is user-provided location information and location-aware services.When the user filed an application to require the positional information of relevant certain portable terminal (MS), positioning service provider is contact location control centre at first, the position coordinates of inquiry MS.The user may be the business user who wishes to follow the tracks of a certain mobile device, or attempts to reply the public safety answering point PSAP (Public SafetyAnswering Point) of an E-911 phone.The position that required information is calculated MS is collected at the Position Control center then, and this information may be the parameters such as TOA such as received signal intensity, BS ID, signal.According to the information in MS past, a series of base stations (BS) can be used to paging MS, and directly or indirectly obtains positional parameter.In case collect these information, the Position Control center just can be determined the position of MS with a certain accuracy, and gives the location service provider this feedback information.The service provider can utilize the position of this information for user's visualization display MS then.

In sum, technical field of the present invention contains the mobile communications network that all provide wireless position and positioning service (Location Based Services).

The selection of navigation system

Location to travelling carriage in the wireless location system is the geometric position of coming the estimating target travelling carriage by the characteristic parameter that detects transmitting signal between travelling carriage and a plurality of fixed positions transceiver.Difference according to position that positions estimation and locator data purposes can be divided into the targeting scheme to travelling carriage two classes: based on the targeting scheme and the based on network targeting scheme of travelling carriage, with it to following two class navigation systems should be arranged:

(1) this type systematic of navigation system based on travelling carriage is also referred to as the travelling carriage self aligning system, also is called the forward link navigation system in cellular network.Its position fixing process is to determine geometry site between itself and each transmitter by travelling carriage according to transmit certain characteristic information relevant with location of mobile station of carrying of a plurality of known location transmitters of receiving, according to relevant algorithm himself position is positioned estimation again, grasp the positional information of himself by user of mobile station.Famous global positioning system (Global Position System) promptly belongs to this type systematic.

(2) this type systematic of based on network navigation system also is called the reverse link navigation system in cellular network.Its position fixing process is the signal that is detected the travelling carriage emission by a plurality of fixed positions receiver simultaneously, certain characteristic information relevant with location of mobile station that carries from each received signal is delivered to an information processing centre handle, calculate the estimated position of travelling carriage.Automatic Vehicle Location (AVL) system promptly belongs to this type systematic.From the essential characteristic of above-mentioned each navigation system as can be seen, in cellular network, adopt based on the forward link targeting scheme of travelling carriage and must suitably revise existing travelling carriage, as integrated GPS receiver or can receive a plurality of base station signals simultaneously and carry out self-align processing unit, also must locating information be sent back cellular network with suitable mode.Based on network reverse link targeting scheme only needs cellular network device is done suitably to expand, revise; do not need existing travelling carriage is changed; can make full use of the huge resource of existing various cellular systems; the existing investment of protection user; realize relatively easily, thereby be the first-selection of E-911 location requirement.

And utilize mobile cellular network that the method for mobile position estimation is mainly contained four classes, (1) is based on the location technology of radio wave field strength; (2) arrive the location technology of incidence angle (AOA) based on electric wave; (3) based on the electric wave time of advent (TOA) or the location technology of the time of advent poor (TDOA); (4) mixed location method.

1. field intensity location technology

The radio wave field strength location technology is according to the signal strength signal intensity of travelling carriage reception and the distance relation of being inversely proportional to of mobile to base station, field intensity value by measuring received signal and known channel decline model and the field intensity value that transmits can estimate the distance between the transceiver, can be estimated the position of travelling carriage at least by a plurality of distance measure (three).The key of this technology is how to set up a radio propagation model that can reflect accurately in the service spread scope, and this is difficult to realize in actual applications.In addition, since factors such as sector characteristic, the antenna of cell base station might tilt, the continuous adjustment of wireless system and geographical environment, vehicle all can exert an influence to positioning accuracy.Because the complexity of radio wave propagation has determined the limitation of this technology on positioning accuracy in the mobile communication environment, but because this technology is relatively simple, be not still to be used under the very high situation required precision.In order to improve its performance, people begin one's study and utilize the ray tracing method in the radio wave propagation to stroll step raising locating accuracy.

2. electric wave arrives incidence angle location technology (AOA)

Signal angle of arrival location AOA method is to estimate mobile subscriber's position by two or more base stations by the angle of arrival of measuring received signal, as shown in Figure 2.The AOA localization method can onlyly be determined a two-dimensional localization point.

MS sends out, and BS1 receives, and measurement can get a BS to the MS line; BS2 receives, and measures another straight line, and two straight lines intersect the generation orientation angle.BS1 and BS2 coordinate position are known, are reference direction with positive north, are+0～+ 360 degree clockwise, are counterclockwise-0～-360 to spend, and can obtain thus with MS, BS1 and BS2 is definite triangle relation of 3.

Adopt the method can obtain higher accuracy, but in the more environment of barrier, because there is multipath effect in wireless transmission, then error increase in the less area of barrier.

In addition, the AOA technology will be based upon on the basis of SA smart antenna and could realize, so in the AOA method, need to use smart antenna, the antenna of BTS need be changed and just can adopt AOA to carry out target localization in the gsm system at present.

Based on radio wave propagation time/the time difference localization method

The time of advent/location technology of time of advent difference is based on the most widely used technology of wireless location system of cellular network.The time of advent, location technology arrived time of base station by measuring the signal that sends from target MS with straight line, can obtain distance between travelling carriage and the base station according to the skyborne propagation velocity of electromagnetic wave.It is the center of circle that travelling carriage promptly is positioned at the base station, and travelling carriage is on the circle of radius to the radio wave propagation distance of base station.Carry out above-mentioned measurement by a plurality of base stations and calculate, the two-dimensional position coordinate of travelling carriage can go out the intersection point of three circles and determine.Ask during arrival that the base station that location technology requires received signal knows that travelling carriage sends the time of signal, and require the base station that point-device clock is arranged.In order to overcome this shortcoming, people have proposed the location technology of the difference time of advent, it is to realize mobile position estimation by detecting the time difference that mobile station signal arrives two base stations, rather than the absolute time that arrives determines the position of travelling carriage, and this just greatly reduces the time synchronized requirement.Clearly, to be positioned with two base stations be on the hyperbola of focus to travelling carriage one.So, find the solution the two-dimensional position coordinate that hyp intersection point can obtain travelling carriage by setting up two above Hyperbolic Equations.

More than the base station of only requiring of two kinds of time-based location technologies can from the radiofrequency signal that receives, extract the time delay estimated value accurately, and need not prior network device is transformed the hi-Fix that just can realize travelling carriage on a large scale, therefore become the research emphasis of cellular network wireless location technology.In general, for based on network location, be referred to as the E-OTD method, and, be referred to as the T-DOA method for location based on terminal.

4. hybrid locating method

This method is to utilize dissimilar signal characteristic measured values in system simultaneously, positions estimation as TDA, AOA.TOA and the AOA data of utilizing serving BS to record in cellular network just can be determined the position of travelling carriage.The prerequisite of utilizing above-mentioned basic fixed position technology accurately to locate is that electric wave can sighting distance (LOS) be propagated between transceiver.In cellular network, owing to be subjected to the influence of non line of sight (NLOS) propagation, multipath effect and various noise jamming, positioning accuracy often is subjected to very big influence.In the above-mentioned positioning mode, the field intensity positioning mode is the simplest, but positioning accuracy is relatively poor; Though the AOA positioning mode has certain precision, receiving equipment is complicated; TOA positioning mode precision is higher, but time synchronized is had higher requirements; The TDOA positioning mode can be eliminated the dependence to time reference, can reduce cost and still guarantees certain positioning accuracy; Mixed location method can satisfy certain positioning accuracy, but adopts this method bigger to the change of the network equipment in existing cellular system.So be subjected to the reverse link positioning mode that is based on TDA or TDOA of extensive concern and further investigation at present.

(E-OTD) locate mode is from Measuring Time poor (OTD) development, and OTD refers to measure the time quantum of gained, and E-OTD refers to the mode measured for the OTD that strengthens.Mobile phone need not additional any hardware just can obtain measurement result.For Synchronization Network, the relative time of advent of the several BTS signals of mobile phone for measuring; For non-synchronous network, signal also needs to be received by the location measurement unit of a location aware (LMU) simultaneously.Determined the signal transmission time of BS, then can determine the geometric distance between BS and the SS, and then calculated, finally determined the position of mobile phone according to this distance to SS.

In general, the performing step of OTD is as follows:

1) terminal (SS) receives that each base station sends signal, obtains the TOA parameter, and then, LMU obtains the RTD parameter;

2) terminal is sent to network with TOA and RTD parameter.

3) OTD measure to need with synchronously, the pulse of standard and simulation.As shown in Figure 4.System requirements, serving BS and plural assistant base station send framing signal at synchronization T.Because terminal is different probably apart from these base stations, therefore can predict

(1) moment of terminal reception serving BS broadcasts framing signal is: T+T ₁

(2) terminal receives and assists the moment of BS1 framing signal to be: T+T ₂

(3) terminal receives and assists the moment of BS2 framing signal to be: T+T ₃

Like this, system or terminal just can be carried out the triangle location according to these times and time difference.The frame that sends as BS is not when synchronous, and network need be measured the RTD between the BS.In order to carry out accurate triangulation, OTD measures and RTD measurement when BS (asynchronous) all needs 3 BS.After obtaining the OTD parameter, terminal location both can calculate in network, also can calculate (requiring mobile phone to possess various necessary informations) in terminal.The former is called the terminal supplementary mode, and the latter is called terminal from master mode.

Yet in the asynchronous system based on TDD, this time relationship is with destroyed, as shown in Figure 5.

Therefore, in this case, system can't accurately calculate relative time delay between each base station.

In sum, the subject matter in the existing system just is that this kind location algorithm can't use in asynchronous system.Present main settling mode is to increase location measurement unit (Location Measurement Unit) by each sub-district in network to come be correlated with synchronous in advance between the base station of nonsynchronous network.As shown in Figure 6.

Yet the placement of LMU mainly contains following subject matter:

1. the net structure cost is higher;

2. because the selection of LMU position, cause channel fading, multipath that synchronous in advance result is caused negative effect on the performance.

Summary of the invention

The purpose of this invention is to provide in a kind of new nonsynchronous network for using between the base station that E-OTD adopts synchronization mechanism in advance.

For achieving the above object, a kind of transmission synchronization method based on the time difference location comprises step:

A) terminal sends to serving BS BS with the compute location request;

B) serving BS BS will transmit Location Request and be transmitted to Serving Mobile Location Center SMLC;

C) SMLC sends wireless presynchronization response to serving BS BS and corresponding other assistant base station BS, and wherein, described response comprises that each BS of indication carries out the estimation of synchronisation mismatch parameter;

D) estimation of the synchronisation mismatch parameter finished according to each BS of SMLC calculates the mismatch parameter between relevant base station and the GPS, and above-mentioned mismatch difference is transferred to serving BS BS;

E) serving BS BS passes to terminal with the mismatch difference from eating dishes without rice or wine;

F) SMLC sends indication to serving BS and assistant base station, informs that service inspection station BS and assistant base station BS send the time slot position or the signal form of sweep signal;

G) serving BS BS and assistant base station BS send sweep signal to terminal;

H) difference and according to the position of time difference computing terminal between terminal is calculated.Through after the processing of this algorithm, serving BS and the precision of the relative delay between assistant base station that system is calculated are improved, thereby have promoted the estimated accuracy based on the E-OTD location estimation.

Description of drawings

Fig. 1 is the wireless location system architecture;

Fig. 2 is the schematic diagram of AOA localization method;

Fig. 3 is the fundamental diagram of T-DOA and E-OTD;

Fig. 4 is based on the emission synchronization principles of E-OTD location;

Fig. 5 is the result of method shown in Figure 4 in asynchronous system;

Fig. 6 is the E-OTD using method in the nonsynchronous network;

Fig. 7 is based on the E-OTD method flow diagram of terminal;

Fig. 8 is based on the E-OTD position fixing process of terminal pattern;

Fig. 9 is based on the E-OTD position fixing process of network schemer.

Embodiment

The present invention has provided in a kind of new nonsynchronous network to using between the base station that E-OTD adopts synchronization mechanism in advance.As shown in Figure 7, main settlement steps to deal can be divided into:

1. compute location request: terminal proposes the wireless location request, and this request sends to SMLC (Serving Mobile Location Center) by terminal.This request at first sends to the BS of service from terminal;

2. transmission Location Request: BS is transmitted to SMLC with this request;

3. the response of wireless presynchronization: SMLC responds this request, and sends response to serving BS broadcasts and other auxiliary BS accordingly.Mainly comprise each BS of indication in this response and carry out the estimation of synchronisation mismatch parameter.For each BS, its real and unified time difference is

Δt＝Mod(T-T _GPS，Frame_Length)

Wherein, T is the moment of some radio frames starting points of this base station, T _GPSBe corresponding GPS unified time, so Δ t is the actual time of synchronisation mismatch.And function Mod representative is got surplus.And the parameter Estimation τ of synchronisation mismatch can be described as in system

$\mathrm{\τ}=\mathrm{Int}(\mathrm{\Δt},\mathrm{PS}),\mathrm{PS}=\frac{4}{\mathrm{Fs}}$

Wherein, Fs is the sample rate of system.Then τ is last synchronisation mismatch parameter.

4. synchronisation mismatch parameter Estimation and transmission: SMLC calculates relevant according to the calculating of process 3

Mismatch parameter between base station and the GPS, τ ₁, τ ₂And τ ₃Then, calculate BS1, the mismatch difference between BS2 and the BS3 is

$\left\{\begin{array}{c}{\mathrm{\σ}}_1={\mathrm{\τ}}_1-{\mathrm{\τ}}_2\\ {\mathrm{\σ}}_2={\mathrm{\τ}}_1-{\mathrm{\τ}}_3\end{array}\right.$

5. above-mentioned adaptive difference is transferred to serving BS broadcasts, if location estimation is estimated in end.

6. continue the mismatch difference is passed to terminal from eating dishes without rice or wine, if location estimation is estimated in end.

7. with the identical wireless location process of other conventional methods based on E-OTD.

Now provide two embodiment of the present invention, shown in Fig. 8 and 9.

At Fig. 8 is location estimation method based on terminal pattern, and its process can be described as 1. compute location requests: terminal proposes the wireless location request, and this request sends to SMLC (Serving Mobile Location Center) by terminal.This request at first sends to the BS of service from terminal:

2. transmission Location Request: BS is transmitted to SMLC with this request;

3. the response of wireless presynchronization: SMLC responds this request, and sends response to serving BS broadcasts and other auxiliary BS accordingly.Mainly comprise each BS of indication in this response and carry out the estimation of synchronisation mismatch parameter.For each BS, its real and unified time difference is

Δt＝Mod(T-T _GPS，Frame_Length)

Wherein, T is the moment of some radio frames starting points of this base station, T _GPSBe corresponding GPS unified time, so Δ t is the actual time of synchronisation mismatch.And function Mod representative is got surplus.And the parameter Estimation τ of synchronisation mismatch can be described as in system

$\mathrm{\τ}=\mathrm{Int}(\mathrm{\Δt},\mathrm{PS}),\mathrm{PS}=\frac{4}{\mathrm{Fs}}$

Wherein, Fs is the sample rate of system.Then τ is last synchronisation mismatch parameter.

4. synchronisation mismatch parameter Estimation and transmission: SMLC calculates the mismatch parameter between relevant base station and the GPS, τ according to the calculating of process 3 ₁, τ ₂And τ ₃Then, calculate BS1, the mismatch difference between BS2 and the BS3 is

$\left\{\begin{array}{c}{\mathrm{\σ}}_1={\mathrm{\τ}}_1-{\mathrm{\τ}}_2\\ {\mathrm{\σ}}_2={\mathrm{\τ}}_1-{\mathrm{\τ}}_3\end{array}\right.$

5. above-mentioned mismatch difference is transferred to serving BS broadcasts.Above-mentioned mismatch difference has two, describes with the symbol-byte that has of two 8bit respectively.

6. continue the mismatch difference is passed to terminal from eating dishes without rice or wine.Above-mentioned mismatch difference has two, describes with the symbol-byte that has of two 8bit respectively.

7.SMLC send an indication to 3 relevant base stations, a serving BS and two assistant base stations send the time slot position of sweep signal, perhaps signal form to inform three BS.

8. three BS send sweep signal to terminal

9. in end, terminal is done the real time difference and is estimated.The delay inequality that at first can get the sweep signal between the BS is Δ T _BSi-BS2With Δ T _BS1-BS3Thereby in terminal and then calculate

$\left\{\begin{array}{c}\stackrel{\&OverBar;}{\mathrm{\&Delta;}}{T}_{\mathrm{BS}1-\mathrm{<figure-callout\; id="2"\; label="BS"\; filenames="A200710307830E00141.png"\; state="\{\{state\}\}">BS</figure-callout>}2}=\mathrm{\&Delta;}{T}_{\mathrm{BS}1-\mathrm{BS}2}-{\mathrm{\&sigma;}}_1\\ \stackrel{\&OverBar;}{\mathrm{\&Delta;}}{T}_{\mathrm{BS}1-\mathrm{BS}23}=\mathrm{\&Delta;}{T}_{\mathrm{BS}1-\mathrm{BS}3}-{\mathrm{\&sigma;}}_2\end{array}\right.$

10. last, can calculate its position by these time difference terminals.

At Fig. 9 is the location estimation method of pattern Network Based, and its process can be described as

1. compute location request: terminal proposes the wireless location request, and this request sends to SMLC (Serving Mobile Location Center) by terminal.This request at first sends to the BS of service from terminal;

2. transmission Location Request: BS is transmitted to SMLC with this request;

3. the response of wireless presynchronization: SMLC responds this request, and sends response to serving BS broadcasts and other auxiliary BS accordingly.Mainly comprise each BS of indication in this response and carry out the estimation of synchronisation mismatch parameter.For each BS, its real and unified time difference is

Δt＝Mod(T-T _GPS，Frame_Length)

Wherein, T is the moment of some radio frames starting points of this base station, T _GPSBe corresponding GPS unified time, so Δ t is the actual time of synchronisation mismatch.And function Mod representative is got surplus.And the parameter Estimation τ of synchronisation mismatch can be described as in system

$\mathrm{\&tau;}=\mathrm{Int}(\mathrm{\&Delta;t},\mathrm{PS}),\mathrm{PS}=\frac{4}{\mathrm{Fs}}$

Wherein, Fs is the sample rate of system.Then τ is last synchronisation mismatch parameter.

4. synchronisation mismatch parameter Estimation and transmission: SMLC calculates the mismatch parameter between relevant base station and the GPS, τ according to the calculating of process 3 ₁, τ ₂And τ ₃Then, calculate BS1, the mismatch difference between BS2 and the BS3 is

$\left\{\begin{array}{c}{\mathrm{\&sigma;}}_1={\mathrm{\&tau;}}_1-{\mathrm{\&tau;}}_2\\ {\mathrm{\&sigma;}}_2={\mathrm{\&tau;}}_1-{\mathrm{\&tau;}}_3\end{array}\right.$

5. above-mentioned adaptive difference is transferred to serving BS broadcasts.Above-mentioned mismatch difference has two, describes with the symbol-byte that has of two 8bit respectively.

6. continue the mismatch difference is passed to terminal from eating dishes without rice or wine.Above-mentioned mismatch difference has two, describes with the symbol-byte that has of two 8bit respectively.There is not this step among Fig. 9?

7.SMLC send an indication to 3 relevant base stations, a serving BS and two assistant base stations send the time slot position of sweep signal, perhaps signal form to inform three BS.

8. three BS send sweep signal to terminal

9. in end, terminal can scan, and sends a scan report to serving BS.Comprise several parameters in this scan report, Relative Delay.This parameter is that terminal pins is measured the down link signal delay of adjacent area down link signal with respect to serving BS broadcasts to particular B S, for required the switching with the neighbor cell of grand diversity different Relative Delay is arranged all.Its numerical value for the sampling duration be the signed integer of unit.

10. serving BS will be chosen among the parameters R elative Delay in this scan report and locate two relevant Relative Delay parameters and send to SMLC.

11. at base station end place, terminal is done the real time difference and is estimated.The delay inequality that at first can get the sweep signal between the BS is Δ T _BS1-BS2With Δ T _BS1-BS3Thereby in terminal and then calculate

$\left\{\begin{array}{c}\stackrel{\&OverBar;}{\mathrm{\&Delta;}}{T}_{\mathrm{BS}1-\mathrm{<figure-callout\; id="2"\; label="BS"\; filenames="A200710307830E00141.png"\; state="\{\{state\}\}">BS</figure-callout>}2}=\mathrm{\&Delta;}{T}_{\mathrm{BS}1-\mathrm{BS}2}-{\mathrm{\&sigma;}}_1\\ \stackrel{\&OverBar;}{\mathrm{\&Delta;}}{T}_{\mathrm{BS}1-\mathrm{BS}23}=\mathrm{\&Delta;}{T}_{\mathrm{BS}1-\mathrm{BS}3}-{\mathrm{\&sigma;}}_2\end{array}\right.$

12. last, can calculate its position by these time difference terminals.

Claims (10)

1. transmission synchronization method based on time difference location comprises step:

A) terminal sends to serving BS BS with the compute location request;

B) serving BS BS will transmit Location Request and be transmitted to Serving Mobile Location Center SMLC;

C) SMLC sends wireless presynchronization response to serving BS BS and corresponding other assistant base station BS, and wherein, described response comprises that each BS of indication carries out the estimation of synchronisation mismatch parameter;

D) estimation of the synchronisation mismatch parameter finished according to each BS of SMLC calculates the mismatch parameter between relevant base station and the GPS, and above-mentioned mismatch difference is transferred to serving BS BS;

E) serving BS BS passes to terminal with the mismatch difference from eating dishes without rice or wine;

F) SMLC sends indication to serving BS and assistant base station, informs that service inspection station BS and assistant base station BS send the time slot position or the signal form of sweep signal;

G) serving BS BS and assistant base station BS send sweep signal to terminal;

H) difference and according to the position of time difference computing terminal between terminal is calculated.

2. method according to claim 1 is characterized in that described mismatch value is two.

3. method according to claim 1 is characterized in that described assistant base station is two.

4. method according to claim 1 is characterized in that carrying out according to following formula the estimation of synchronisation mismatch parameter:

Δt＝Mod(T-T _GPS，Frame_Length)

Wherein, T is the moment of some radio frames starting points of this base station, T _GPSBe corresponding GPS unified time, so Δ t is the actual time of synchronisation mismatch, and function Mod representative is got surplus.

5. method according to claim 1 is characterized in that being calculated as follows the time difference:

$\left\{\begin{array}{c}\stackrel{\&OverBar;}{\mathrm{\&Delta;}}{T}_{\mathrm{BS}1-\mathrm{BS}2}=\mathrm{\&Delta;}{T}_{\mathrm{BS}1-\mathrm{BS}2}-{\mathrm{\&sigma;}}_1\\ \stackrel{\&OverBar;}{\mathrm{\&Delta;}}{T}_{\mathrm{BS}1-\mathrm{BS}23}=\mathrm{\&Delta;}{T}_{\mathrm{BS}1-\mathrm{BS}3}-{\mathrm{\&sigma;}}_2\end{array}\right..$

6. transmission synchronization method based on time difference location comprises step:

A) terminal sends to serving BS BS with the compute location request;

B) serving BS BS will transmit Location Request and be transmitted to Serving Mobile Location Center SMLC;

C) SMLC sends wireless presynchronization response to serving BS BS and corresponding other assistant base station BS, and wherein, described response comprises that each BS of indication carries out the estimation of synchronisation mismatch parameter;

D) estimation of the synchronisation mismatch parameter finished according to each BS of SMLC calculates the mismatch parameter between relevant base station and the GPS, and above-mentioned mismatch difference is transferred to serving BS BS;

E) SMLC sends indication to serving BS and assistant base station, informs that service inspection station BS and assistant base station BS send the time slot position or the signal form of sweep signal;

F) serving BS BS and assistant base station BS send sweep signal to terminal;

G) terminal sends scan report to serving BS BS, comprises several parameters R elative Delay in the described scan report;

H) serving BS will be chosen among the parameters R elative Delay in the described scan report and locate two relevant Relative Delay parameters and send to SMLC;

I) difference and according to the position of time difference computing terminal between terminal is calculated.

7. method according to claim 6 is characterized in that described mismatch value is two.

8. method according to claim 6 is characterized in that described assistant base station is two.

9. method according to claim 6 is characterized in that carrying out according to following formula the estimation of synchronisation mismatch parameter:

Δt＝Mod(T-T _GPS，Frame_Length)

Wherein, T is the moment of some radio frames starting points of this base station, T _GPSBe corresponding GPS unified time, so Δ t is the actual time of synchronisation mismatch, and function Mod representative is got surplus.

10. method according to claim 1 is characterized in that being calculated as follows the time difference:

$\left\{\begin{array}{c}\stackrel{\&OverBar;}{\mathrm{\&Delta;}}{T}_{\mathrm{BS}1-\mathrm{BS}2}=\mathrm{\&Delta;}{T}_{\mathrm{BS}1-\mathrm{BS}2}-{\mathrm{\&sigma;}}_1\\ \stackrel{\&OverBar;}{\mathrm{\&Delta;}}{T}_{\mathrm{BS}1-\mathrm{BS}23}=\mathrm{\&Delta;}{T}_{\mathrm{BS}1-\mathrm{BS}3}-{\mathrm{\&sigma;}}_2\end{array}\right..$

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