JP2004533177A - Method and apparatus for synchronizing base stations using mobile GPS stations - Google Patents

Abstract

Various methods and apparatus for synchronizing mobile base stations in a mobile network are provided.
According to one exemplary method of the present invention, a first date and time and a first geographic location of a first mobile portable receiver station (MS) are located with the first MS. Determined from a first satellite positioning system (SPS) receiver. Then, the first date and time and the first location are transmitted to the first base station by the first MS. Then, the first base station determines the date and time of the first base station from the first date and time, the first location, and the known location of the first base station.
[Selection] Figure 4

Description

【Technical field】
[0001]
The present invention relates to a mobile communication system, and more particularly, to a system for determining a location of a mobile mobile communication station (MS).
[Background]
[0002]
Various triangulations based on using timing information transmitted between each of various base stations and a mobile device such as a mobile phone to perform positioning in a mobile network (eg, a mobile phone network) The approach has been made. In an approach called Time Difference of Arrival (TDOA), the reception time of a signal from a mobile is measured at some base stations. These times are then referred to as positioning servers and are sent to the location determination entity that calculates the location of the mobile. In order for this approach to work, the dates and times at the various base stations need to be adjusted to provide the exact location. Also, the location of the base station needs to be accurately known. FIG. 1 is a diagram illustrating an example of a TDOA system. Here, the reception time (TR 1, TR 2, TR 3) of the same signal from the mobile mobile phone 22 is measured by the positioning server 24 at the mobile base stations 12, 14, 16. The positioning server 24 is coupled to receive data from the base station via the mobile switching center 18. The mobile switching center 18 transmits signals (eg, voice communications) to / from landline public switching telephone systems (PSTS) to other phones (eg, land) so that the signals can be carried to and from mobile phones. It is provided to land line telephones and other mobile telephones in the line public switched telephone system (PSTS).
[0003]
In some cases, the positioning server also communicates with the mobile switching center via a mobile link. The positioning server also monitors these transmissions to determine the relative timing of each transmission transmitted from several base stations.
[0004]
Another method, also called EOTD, measures the arrival time of signals transmitted from several base stations in the mobile. If the arrows for TR1, TR2, and TR3 are reversed, FIG. 1 applies to this case. This timing data is then used to calculate the mobile location. If the timing information obtained by the mobile is sent to this server via a link, such calculation is done at the mobile itself or at the positioning server. Again, the base station dates and times must be adjusted and their location must be accurately evaluated. In either approach, the location of the base station is determined by standard survey methods and stored in the base station or in a main server with computer memory.
[0005]
The third method of positioning uses a receiver for GPS or other satellite positioning system (SPS) in the mobile. This method can be completely autonomous. Alternatively, assistance data can be provided using a mobile network, or position calculation can be shared. Examples of such a method are described in Patent Documents 1 to 3. We abbreviate the above method and call it SPS. Any combination of EOTD, TODA, and SPS systems is called a “hybrid” system. It will be clear from the above description that EOTD or TDOA requires time adjustment between various mobile base stations for accurate mobile location calculation. The required accuracy of date and time at the base station depends on the details of the positioning method used. In one method, a round trip time (RTD) was detected for a signal transmitted from a base station to a mobile and then returned. In another similar method, a round trip delay time was detected for a signal transmitted from the mobile to the base station and then returned. By dividing each round trip time by 2, a one-way time delay estimate can be determined. Information that adds a one-way time delay to the location of the base station constrains the location of the mobile relative to the circle on the earth. Then, the result of another measurement with the second base station is the intersection of the two circles. This constrains the location for two points on the earth. Such a third measurement resolves the ambiguity. In round trip timing, even if the mobile moves fast, the measurements made at several base stations will be adjusted to a few seconds at the worst so that the measurements will match those at the same location. is important.
[0006]
In other situations, it is possible to measure round trips only for one base station, which is the primary one communicating with the mobile, but it is not possible to make round trip measurements for each of two or three base stations. Is possible. This is the case for the IS-95 North American CDMA mobile standard. Or it may not be possible to measure the exact round trip timing due to instrument or signal protocol limitations. In this case, if a triangulation measurement operation is performed, only the time difference in the path between the mobile and the base station is used, so it is more important to maintain accurate timing at the base station.
[0007]
Another reason for having the exact timing present at the base station is to give the mobile time to support positioning calculations based on GPS. Such information results in a conversion time for the first fixed and / or improved sensitivity. The required accuracy for these situations can range from a few milliseconds to about 10 milliseconds, depending on the required performance gain. In a hybrid system, this base station timing serves a dual purpose, such as improved TOA or TDOA effects, as well as GPS effects.
[0008]
The prior art is close to network timing applying a special fixed location timing system termed positioning measurement unit (LMU) or timing measurement unit (TMU). These units typically include a GPS receiver that can determine the exact date and time. The location of these units is surveyed as done, for example, with survey equipment based on GPS.
[0009]
In general, the LMU or TMU observes a timing signal such as a framing marker present in a mobile communication signal transmitted from a base station. It then tries to time tag these timing signals using the local time detected via a GPS set or other time determination device. Thereafter, a message is transmitted to the base station (or other infrastructure device). This allows these entities to keep track of elapsed time. Then, based on the command or periodically, a special message is transmitted over the mobile network to the mobile provided by the network displaying the date and time corresponding to the signal framing configuration. This is particularly easy for systems such as GSM where the total framing configuration continues with a period of more than 3 hours. It should be noted that the positioning measurement unit serves other purposes so as to operate as a positioning server. That is, the LMU actually measures the arrival time from the mobile to determine the location of the mobile.
[0010]
One problem with the LMU or TMU approach is that it requires the construction of new special fixed equipment at each base station or other site within the coverage of several base stations. This can lead to significant costs for installation and maintenance.
[Patent Document 1]
U.S. Patent Registration Number 5,841,396
[Patent Document 2]
U.S. Patent Registration Number 5,945,944
[Patent Document 3]
US Patent Registration Number 5,812,087
[Patent Document 4]
US patent application number 09 / 062,232 (filed April 16, 1998)
[Patent Document 5]
U.S. Patent Registration Number 6,002,363
[Patent Document 6]
U.S. Patent Registration Number 5,874,914
DISCLOSURE OF THE INVENTION
[Problems to be solved by the invention]
[0011]
The present invention has been made in view of such circumstances, and an object thereof is to provide various methods and apparatuses for synchronizing mobile base stations in a mobile network.
[Means for Solving the Problems]
[0012]
One exemplary method provides time synchronization between at least two base stations of the mobile communication system, i.e., the first base station and the second base station. In this exemplary method, a first satellite positioning system (SPS) in which a first date and time and a first location of a first mobile mobile station (MS) are located with the first mobile station (MS). Determined from the receiver. Then, the first date and time and the first place are transmitted to the first base station by the first MS. Then, the first base station determines the date and time of the first base station from the first date and time, the first location, and the known location of the first base station. Also, in this exemplary method, the second date and time and the second location of the second MS are determined from a second SPS receiver located with the second MS. Then, the second date and time and the second location are transmitted to the second base station. Then, the second base station determines the date and time of the second base station from the second date and time, the second location, and the known location of the second base station. These mobile stations are used for normal communication operations and do not need to be fixed to buildings or structures, so use for network timing is a real estate to maintain fixed timing equipment Avoid high costs due to Other methods and apparatus for synchronizing base stations in a mobile network have also been described.
【The invention's effect】
[0013]
According to the present invention, mobile base stations in a mobile network can be synchronized.
BEST MODE FOR CARRYING OUT THE INVENTION
[0014]
Various methods and apparatus are described herein for determining the time at a mobile base station or for synchronizing the mobile base station within a mobile network. In the following description, numerous specific details are given to provide a thorough understanding of the present invention. For example, various architectures for base stations and mobile communication stations are provided for illustrative purposes without being construed as a limitation of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate description.
[0015]
One approach described herein utilizes a mobile communication station that includes (or is coupled to) a GPS receiver that determines both date and position. FIG. 2 shows an example of such a mobile communication station. If the received signal is large, this GPS processing is performed in an automatic mode. Alternatively, if the received signal-to-noise ratio is low, this is done with the aid of equipment in the infrastructure (server). A server device (for example, a positioning server shown in FIG. 8 as described later) contributes to date and positioning when performance improvement is required (for example, see Patent Documents 1, 2, and 3).
[0016]
In a network such as GSM, date and time information from a GPS receiver is used to attach a time tag to a framing configuration (eg, GSM) of a received communication signal. For example, the start of a specific GSM frame boundary that occurs every 4.6 milliseconds is used (see FIG. 9). There are 2048 such frames per superframe lasting 3.48 hours. Therefore, if this timing information is sent to a base station (BS) (for example, the mobile base station shown in FIG. 3) via a normal mobile signal, the only main error within the transfer time is the mobile station. (MS) Propagation time from BS (for example, mobile portable communication station in FIG. 2) to BS. Of course, there are other remaining errors such as multi-path delays and transit delays via MS hardware. Evaluation methods for these remaining errors are described later.
[0017]
Various methods are used to evaluate the propagation delay between the MS and the BS. The first and high accuracy approach is that the MS and / or server accurately determines the MS location via the GPS unit and the BS location is known accurately (eg, predetermined via the survey). Applicable to the case. In this case, the propagation time is determined by dividing the range between the MS and the MS by the speed of light (generally at some network entity). The BS then determines the timing of the transmitted frame marker by simply subtracting the calculated propagation time from the frame marker timing given by the MS. This method is further described below in conjunction with FIG. 5, FIG. 6, and FIG.
[0018]
A second and less accurate approach to assess the propagation delay between the MS and BS is enabled by “timing advance” information that is already valid within the MS and BS. This is primarily intended for information regarding traffic regulation within a cell. However, the timing advance metric is processed in a straightforward way to obtain a delay estimate between the MS and the BS. The accuracy provided by such time adjustment parameters is largely determined by the time resolution of the associated communication bit interval. Accordingly, it is possible to obtain a propagation delay estimation value with an accuracy within several milliseconds or several tens of milliseconds. This second approach is not as accurate as the first lag estimate approach described above, but is particularly advantageous in situations where privacy issues are hindering accurate MS location network operations.
[0019]
As described above, in certain applications, the base station need not be synchronized with microsecond precision, but may be synchronized with millisecond or second precision. For these scenarios, it may not be productive to compensate for the delay between the MS and the BS. This is because small delays on the order of microseconds or tens of microseconds are not important for the required timing accuracy. Therefore, the coarse date and time obtained by the MS is simply used as it is for tagging the signal from the BS. This is sent to the BS without the need for strict BS-MS range data. This situation is advantageous. This is because a GPS receiver can tag a coarse time tag at a much lower signal level rather than being able to tag an accurate time tag (eg, incorporated by reference). Patent Document 3 and Co-pending Patent Document 4 incorporated as a reference). Furthermore, once a coarse time tag is attached, its accuracy is maintained over a long period of time due to the high frequency stability of the data transmitted by the base station.
[0020]
FIG. 4 shows an example of a typical method according to an embodiment of the present invention. In operation 151, the mobile portable system determines display of date and time in the mobile portable communication system. In one embodiment, i.e., when a GPS receiver such as GPS receiver 52 is used in a mobile cellular communication system as shown at 50 in FIG. 2, GPS time is derived from GPS satellites at the MS. It is obtained by reading the GPS time when the GPS signal is turned off. Alternatively, the time determination method described in US Pat. In this approach, samples of GPS signals received at the mobile are sent to a positioning server or other server, and this recording is processed to determine the reception time as described in US Pat. Is done. In yet another method, in operation 151 the date and time is calculated using one of the various methods described in US Pat. The method illustrated in FIG. 4 proceeds to operation 153. In operation 153, a propagation delay between the mobile portable communication station and a portable base station such as the portable base station shown in FIG. 3 is determined. It will be appreciated that in some cases of the above-described embodiment, this operation is an option that is determined when the time determined in operation 151 involves more error than propagation delay. Also, as described above, this propagation delay is determined by determining the position of the mobile (by processing the GPS signal) and determining the position of the mobile base station. In action 153, the propagation delay is determined by dividing the distance between these two positions by the speed of light.
[0021]
In act 155, the time at the mobile base station is determined from the mobile date and time (transmitted from the mobile mobile communication system). Further, when the option operation of the operation 153 is used, the determination is made in consideration of the propagation delay determined in the operation 153.
[0022]
Each mobile base station in the network performs this process to synchronize all base stations associated with one time standard, such as GPS time. In this way, improved triangulation, or ranging, is obtained using timing information sent between each of several base stations and the mobile system. Timing information is also used for many other applications. These make handoffs, which are mobile communications from one base station to the next, more efficient. It then reveals the time transmitted over the network for various purposes.
[0023]
5, 6 and 7 are described as further examples of embodiments according to the present invention. This method operates in a mobile portable communication system such as the system 50 shown in FIG. 2 and the mobile base station 101 shown in FIG.
[0024]
A mobile portable communication station 50 shown in FIG. 2 includes a GPS receiver 52 having a GPS antenna 51 and a portable communication transceiver 54 including an antenna 53. Alternatively, the GPS receiver 52 is included in another chassis (not integrated into the chassis that holds the mobile station 50 equipment, such as the mobile communication transceiver 54), and is coupled to the mobile communication transceiver 54. , Close to the transceiver 54. In this case, however, the station 50 does not include a GPS receiver and does not require it as long as the GPS receiver is coupled and located with the station 50. The GPS receiver 52 is conventional and may be a hardware correlation based GPS receiver. Alternatively, it can be a matched filter based GPS receiver. Or it may be a GPS receiver using a buffer for storing digital GPS signals processed by high-speed convolution. Alternatively, the GPS receiver described in Patent Document 5 such that the GPS receiver component is shared with the portable communication transceiver component (see FIG. 7B of Patent Document 5 incorporated herein as a reference). It can be. The portable communication transceiver 54 is a well-known portable standard, including the GSM portable standard, or the PDC communication standard, or the PHS communication standard, or the AMPS analog communication standard, or the North American IS-136 communication standard, or the asynchronous wideband spread spectrum CDMA standard. It can be a modern mobile phone that works with either one. The GPS receiver 52 is coupled to the portable communication transceiver 54 and, in one embodiment, provides the GPS time and location to the portable communication transceiver 54 (which then transmits this information to the base station). Further, as described in Patent Document 1 and Patent Document 2, the mobile communication transceiver 54 provides assistance data such as Doppler information or time information to the GPS receiver. The coupling between the GPS receiver 52 and the portable communication transceiver 54 is for sending and receiving records to and from the portable base station in order to determine time in the GPS receiver as described in US Pat. Used for. This is for matching this record with another record. The situation or embodiment in which the positioning server is used to provide assistance data to the mobile mobile communication station for the purpose of determining position and time in the system 50, or the positioning server is responsible for processing the information. In a situation or embodiment, a positioning server as shown in FIG. 8 and described below is connected to the mobile base station through a communication link to support data processing. The location of the mobile station is usually not fixed and is not determined in advance.
[0025]
FIG. 3 shows an example of a mobile base station used in various embodiments of the present invention. Base station 101 includes a portable transceiver 102. The transceiver 102 has at least one antenna 102a that performs signal communication with a mobile portable communication station. This signal exists in an area where service is provided by the mobile base station 101. For example, the mobile mobile communication station 50 can be one of the mobile stations served by the mobile base station 101, typically based on the range of signals transmitted by the mobile system 50. The portable transceiver 102 is a conventional type transceiver used for transmitting and receiving portable signals such as GSM portable signals or CDMA portable signals. The clock 103 may be a conventional type system clock that maintains the date and time at the mobile base station. The accuracy of this watch can be improved according to the method of the present invention so that it can be synchronized to other watches at other mobile base stations according to the method described herein. In many cases, the watch is very stable, but drifts significantly over a period relative to the initial time setting. The mobile base station 101 also typically includes a network interface for transmitting and receiving data to and from the mobile transceiver 102 to couple the mobile transceiver to a mobile switching center well known in the art. The mobile base station 101 may also include a digital processing system 105 that is either located relatively far from the mobile base station or at the same site as the mobile base station itself. The digital processing system 105 is coupled to the clock 103 for adjusting and resetting the clock time according to the method of the present invention and synchronizing the clock with other clocks of other mobile base stations. . In many cases, this watch is very stable but free to operate, affecting network operation to actually change the time stroke of the watch. Instead, the time corresponding to the clock epoch can be adjusted. This is implied by “resetting”. The digital processing system 105 also receives data or communications from the mobile switching center and is tagged with a time tag sent from the mobile system for the purpose of synchronizing the clock 103 to other clocks in other mobile base stations. A network interface 104 is connected to receive data from the portable transceiver 102, such as a frame marker.
[0026]
The method shown in FIGS. 5 and 6 starts at operation 201 when the mobile base station transmits a mobile signal to the mobile mobile communication station. Optionally, this signal includes a request for synchronization information from the mobile system so that the mobile base station can synchronize itself with other mobile base stations. The mobile base station provides a time tag or marker on the signal being transmitted to the mobile system. This marker may be a marker that is a unique part of the framing configuration of the signal. This is further illustrated in FIG. 7 (a). In FIG. 7A, the base station 1 transmits a signal 301 together with a framing configuration including markers M1, M2, M3, M4, M5, M6, M7, M8, and M9. In operation 203 of FIG. 5, the mobile system receives the mobile signal with the marker. Simultaneously with receiving this portable signal, the mobile station also receives GPS signals from GPS satellites. The GPS signal includes GPS time. This is well known in the art. After that, the mobile station attaches a time tag to the marker of the portable signal received from the base station together with the GPS time. The portable signal represents in GPS time the time when the marker was received at the mobile system. This is indicated by signal 303 in FIG. A signal 303 indicates that the signal from the base 1 received by the mobile 1 is delayed by the propagation delay 307. As shown in FIG. 7A, a time tag 305 is attached to the marker M1. This represents the GPS time corresponding to the time this marker was received at the mobile system. In act 205, the mobile station simultaneously determines its location and the marker time tag in the portable signal. The GPS receiver at the mobile station automatically determines its position (eg, existing hardware correlation based GPS receivers determine their position by reading position estimation data from GPS satellites). Alternatively, the position is determined with the assistance of a server such as the positioning server shown in FIG. 8 connected to the mobile network. In operation 207, the mobile station transmits its location (or pseudo range such that the location server can determine its location) and the GPS time corresponding to the marker, which is time-tagged by the mobile station. Send to the station.
[0027]
In act 209, the mobile base station calculates the date and time by using the mobile location and its predetermined location to determine the propagation delay between the mobile and the base station. This propagation delay is subtracted from the GPS time corresponding to the marker to determine the GPS time at the transmitted marker. This is illustrated in FIG. 7 (b) where the base station 1 receives the time TR1 from the mobile system. This time tag TR1 represents the GPS time corresponding to the marker M1. This propagation delay 307 is subtracted from the GPS time TR1 to obtain a time T1 corresponding to the marker M1. That is, the time T1 is the time tag 309 corresponding to the marker M1 in the base station. Thereafter, the current time at the base station is updated by associating the current frame M9 with the GPS time at the tag 309, and a current time 311 is generated as shown in FIG. 7B. That is, the signal 301 has a known time relationship between the marker M9 and the marker M1, giving the framing configuration of the signal 301. The time difference between these two markers giving a known framing configuration is added to time T1 to generate the current time 311. Therefore, the current time at the mobile base station is updated from the GPS time associated with the marker that has been tagged and transmitted by the mobile. This is illustrated in action 211 in FIG. Then, in operation 213, as an option, the previous time when the clock was synchronized in the mobile base station is stored. This is done to determine when it is appropriate to update the clock in order to synchronize the clock with other clocks at other mobile base stations. In act 215, it is determined when to re-synchronize the mobile base station or the remote entity supporting the mobile base station. For example, a set time of a few minutes automatically causes another synchronization process. In another method, other techniques have been applied to determine when the clock at the base station is again synchronized with other clocks on other mobile base stations.
[0028]
FIG. 8 illustrates an example of a positioning server 350 that may be used with various embodiments of the present invention. For example, as described in Patent Document 1, this server provides assistance data such as Doppler or other satellite assistance data to a GPS receiver in the mobile station 50. Alternatively, this positioning server, not the mobile station 50, performs the final position calculation (after receiving the pseudorange or other data that can determine the pseudorange from the mobile) and the base station calculates the propagation delay. This position determination is forwarded to the base station so that The positioning server typically includes a data processing unit such as a computer system 351, a model or other interface 352, 353, 354, a mass storage device 355 (eg, storing software and data), and an optional GPS receiver 356. Contains. The positioning server 350 is connected to three different networks indicated by networks 360, 362, and 364. The network 360 includes one or more mobile switching centers and / or land based telephone system switches. Alternatively, the modem 353 is directly connected to a cell site such as the mobile base station 101. Multiple mobile base stations are typically adjusted to cover a geographic area by radio coverage, and different base stations connect to at least one mobile switching center (see FIG. 1) as known in the prior art. It will be recognized that Thus, a plurality of examples of the base station 101 are geographically arranged but connected to the mobile switching center. Network 362 is a network of reference GPS receivers that provide different GPS information and also provides GPS position estimation data that is used to calculate the position of the mobile system. This network is coupled to the data processing unit 351 through a modem or other communication interface 354. The network 364 includes other computers or network equipment such as the data processing system 105 shown in FIG. 3 (through optional interconnections not shown in FIG. 3). The network 364 may also include a computer system operated by an emergency operation, such as a public safety response point that answers 911 telephone calls. Examples of various methods of using positioning server 350 are described in many US patents and patent applications, such as US Pat. ing.
[0029]
Each of the above methods determines the effective transmission time in the plane of the BS antenna. The use of multiple MSs tends to reduce errors by going through an averaging process. This assumes that the system bias can be removed.
[0030]
The concern that the MS's ability is sufficient to support timing (eg, early morning time) is improved by placing the MS in various locations and periodically making calls.
[0031]
Typical time errors due to GPS processing in a single MS are on the order of 10-30 nanoseconds. Therefore, other error sources such as multiple paths are dominant.
[0032]
The stability of the BS oscillator affects how often timing measurements need to be made and spread. It is possible to model BS oscillator drift versus time and reduce the update frequency.
[0033]
Several methods for calibrating mobile station receiver errors and effects are described. In one embodiment of the present invention, a mobile (eg, mobile communication station 50 shown in FIG. 2)_mobile= [X_m, Y_m, Z_m] And the time T corresponding to this place_mobileTo decide. This associates the time with the framing marker of the received mobile communication signal by simply measuring the time delay relative to the time of the framing marker from the time of location determination (eg GPS time). Alternatively, this location determination can be made at a time equal to the time of the framing marker. Therefore, without losing generality, T_mobileIs equal to the time of the framing marker observed by the mobile.
[0034]
Mobile is also the base station location P_base= [X_b, Y_b, Z_bIs assumed to be known. At that time, if delay due to multiple paths is not important, the time T_mobileThe range from base station to mobile in
R_Tm= [(X_m-X_b)²+ (Y_m-Y_b)²+ (Z_m-Z_b)²]^1/2
It becomes.
[0035]
If there is no delay in the receiving circuit, the range of the propagation time delay between the base station and the mobile is R_Tm/ C. Where c is the speed of light.
For the sake of clarity, the transmission time of the framing marker at the base station is referred to as the occurrence time of this marker on the surface of the transmission antenna of the base station. Therefore, when there is no multipath delay, or when there is no receiver delay, the transmission time of the frame marker on the antenna surface of the base station is T_base= T_mobile-R_Tm/ C.
[0036]
Now, the GPS receiver is b_GPSHas a delay corresponding to RF and digital signal processing. Similarly, B_commThere is a delay corresponding to the RF and digital signal processing of the communication receiver called. Therefore, as shown in FIG._GPSIs caused by a delay in the GPS receiver 52, b_commIs caused by a delay in the portable communication transceiver 54. Furthermore, the multiple paths introduce additional delay in the propagation from the base station to the communication receiver. This delay is b_multitis called. We believe this dominates certain multipath delays associated with GPS measurements. Thus, instead of providing an unbiased measurement of transmission time at the base station, we_multit+ B_comm-B_GPSProvides a measurement with a bias of (measured time minus true time). In general, especially when the receiver calibration function is performed (discussed below), b_multitDominates other error sources. Therefore, normally, the estimated transmission time of the framing marker is slow.
[0037]
b_comm-B_GPSCan be measured simply by using a base station simulator. The base station simulator transmits a portable signal together with a framing configuration, and is directly connected to a mobile antenna port. Then, the reception time of the frame marker in the mobile is measured. In this process, a mobile GPS receiver is used to attach a time tag (GPS time received by the mobile GPS receiver) to the frame marker. Here, the base station simulator uses a GPS receiver to synchronize the transmission to the GPS time provided by the GPS receiver. Since the transmission delay from the base station to the receiver is zero, this approach does not introduce errors (except for very little measurement noise) b_comm-B_GPSTo decide. This calibration process is fully automatic and can be easily integrated into the receiver within the test process during manufacture. Simple modifications, such as sending simulation signals from a simulator very close to the mobile to the mobile, are possible.
[0038]
Extra multipath delay b_multitIs a major source of error when synchronizing base stations. Depending on the line of sight, this delay has an average of zero bias. If there is a reflected path, or a path consisting of a combination of direct and reflected, on average it will be greater than zero (measured versus true direct path delay). The base station typically receives a number of time estimates associated with each frame marker from each mobile unit as well as from several mobile units within a short period of time. Let these date estimates be D₁, D₂, ... D_KI will call it. The lowest of these estimates usually has an average bias that is significantly lower than the average of any individual measurement or measurement. If the number K of measurement values is large, the measurement values can be rearranged from low to high, and an average of 10% of the low measurement values can be taken, or similar statistics can be taken. This greatly reduces the average bias and can take advantage of some average processing.
[0039]
If the base station has a very stable clock, this clock is used to maintain the time between updates from the remote mobile unit. This watch can be used in a smoothing process to remove bad measurements from mobile by multiple paths. In addition, measurements from mobile are used, for example, to measure the long-term stability of base station clocks with age. As an example, a GSM hyperframe is about 3.48 hours and a superframe is 6.12 seconds. Thus, the hyperframe is about 12528 seconds. A typical GPS time measurement should be accurate to about 100 nanoseconds without differential correction. With this accuracy, the base station oscillator can measure over a long period of time from about 100 nanoseconds / 12528 seconds to 8 x 10^-12It becomes. Even with measurements over a 6.12 second period, the long-term accuracy is approximately 1.6 x 10^-8It becomes. This long-term measurement stability is best achieved by making several date and time measurements using the same mobile receiver. Therefore, fixed or slowly moving mobiles are best suited for this purpose. Continuous measurements of mobile location can provide the necessary information related to mobile receiver activity.
[0040]
If there is significant user activity, it is important that any Doppler related effects do not affect the timing measurements described above. In particular, if the time is measured in an example of a mobile and the date and time corresponding to the mobile signal frame boundary generated in another example is predicted, an error may occur due to the operation of the mobile. This is the case if the mobile is operating fast and / or the difference between these time instances is large. There are many ways to handle this type of problem. For example, if the mobile can determine its speed, this data is supplied to the base station. This base station can compensate for an error caused by Doppler corresponding to a range ratio between the mobile and the base station.
[0041]
Although the method and apparatus of the present invention have been described in the context of GPS satellites, it will be appreciated that the above disclosed techniques are equally applicable to positioning systems that utilize pseudoruites or a combination of satellites and pseudoruites. Pseudolites are land-based transmitters that broadcast PN codes (similar to GPS signals) that are modulated with L-band carrier signals and are generally synchronized in GPS time. Each transmitter is assigned a unique PN code, as identified by the remote receiver. Pseudolites are useful in situations where GPS signals from orbiting satellites are not available, such as tunnels, mines, buildings, and other closed locations. As used herein, the term “satellite” is intended to include pseudolites or equivalents thereof. Also, as used herein, the term GPS signal is intended to include GPS approximate signals from pseudoruites or equivalents of pseudoruites.
[0042]
In the foregoing description, the present invention has been described in connection with an application relating to the US GPS system. However, these methods are equally applicable to similar satellite positioning systems and especially the Russian Glonass system. The Glonass system is fundamentally different from the GPS system in that signals from different satellites are distinguished from each other using slightly different carrier frequencies rather than different pseudo-random codes. As used herein, the term “GPS” includes such another satellite positioning system and includes the Russian Glonass system.
[0043]
The specification set forth herein describes the invention with reference to specific and exemplary embodiments. However, it will be appreciated that various modifications and changes may be made without departing from the broad spirit and scope of the invention as set forth in the claims. The specification and drawings are accordingly to be regarded in an illustrative rather than restrictive sense.
[Brief description of the drawings]
[0044]
FIG. 1 illustrates an example of a prior art mobile network that determines the location of a mobile mobile device.
FIG. 2 is a diagram illustrating an example of a mobile cellular communication station used with the present invention and including a GPS receiver and a cellular communications transceiver.
FIG. 3 shows an example of a mobile base station used in various embodiments of the present invention.
FIG. 4 is a flowchart illustrating an example of a method according to the present invention.
FIG. 5 is a flowchart (first half) showing an example of another method according to the present invention.
FIG. 6 is a flowchart (second half) showing an example of another method according to the present invention.
FIG. 7 shows two signals processed according to an exemplary method of the present invention and a signal at the base station.
FIG. 8 illustrates an example of a positioning server that can be used in an embodiment of the present invention.
FIG. 9 is a diagram showing a framing configuration of a GSM mobile signal.
[Explanation of symbols]
[0045]
DESCRIPTION OF SYMBOLS 1 ... Base station, 12, 14 ... Mobile base station, 18 ... Mobile switching center, 22 ... Mobile mobile phone, 24 ... Server, 50 ... Mobile mobile communication station, 51 ... GPS antenna, 52 ... GPS receiver, 53, 102a ... Antenna, 54, 102 ... Mobile communication transceiver, 101 ... Mobile base station, 104 ... Network interface, 105 ... Digital processing system, 305, 309 ... Time tag, 311 ... Current time, 350 ... Server, 351 ... Data processing unit, 352, 354 ... Other interfaces, 353 ... Modem, 355 ... Mass storage device, 356 ... GPS receiver, 360, 362, 364 ... Network

Claims (34)

A method for achieving time synchronization between at least two base stations including a first base station and a second base station of a mobile communication system,
Determine the date and location of the first mobile mobile station,
Transmitting the date and location of the first mobile mobile station to the first base station through a first mobile communication link;
Determine the date and time of the first base station from the date and location of the first mobile mobile station along with the known location of the first base station;
Determine the date and location of the second mobile cell station,
Transmitting the date and location of the second mobile mobile station to the second base station through a second mobile communication link;
Determine the date and time of the second base station from the date and location of the second mobile mobile station together with the known location of the second base station;
The first mobile mobile station and the second mobile mobile station each use a satellite location system receiver located together to determine the date and location of the first and second mobile mobile stations. How. The method of claim 1, wherein
A method in which the date and time of the first mobile mobile station is measured in relation to a frame synchronization epoch that is present with a mobile communication signal, transmitted from the first base station, and received by the first mobile mobile station. . The method of claim 1, wherein
The method of determining the date and time of the first base station relates to a frame synchronization epoch that is present with a mobile communication signal transmitted from the first base station. The method of claim 1, wherein
The portable communication link uses one of the GSM communication standard, the PDC communication standard, the PHS communication standard, the AMPS analog communication standard, the North American IS-136 communication standard, and the asynchronous wideband spread spectrum CDMA standard. The method of claim 1, wherein
The method in which the first mobile mobile station and the second mobile mobile station are the same station. The method of claim 1, wherein
The method wherein the first mobile mobile station and the second mobile mobile station are different and are separate mobile mobile stations. A system for achieving time synchronization between at least two base stations including a first base station and a second base station of a mobile communication system,
The date and location of the first satellite positioning system receiver is arranged with a first mobile mobile station capable of transmitting to the first base station and determining the date and location of the first mobile mobile station A first satellite positioning system receiver capable of:
It is coupled to the first base station and can determine the date and time of the first base station from the date and location of the first mobile mobile station along with the known location of the first base station A first measuring device,
A date and location of a second satellite positioning system receiver is arranged with a second mobile mobile station capable of transmitting to the second base station and determining the date and location of the second mobile mobile station; A second satellite positioning system receiver capable of:
It is coupled to the second base station and can determine the date and time of the second base station from the date and location of the second mobile mobile station along with the known location of the second base station And a second measuring device. The system of claim 7, wherein
The system in which the first satellite positioning system receiver is integrated in a housing with the first mobile mobile station. The system of claim 8, wherein
The system in which the first satellite positioning system receiver and the first mobile mobile station share at least one common device. The system of claim 7, wherein
A system in which the date and time of the first mobile mobile station is measured in relation to a frame synchronization epoch present in a mobile communication signal transmitted from the first base station to the first mobile mobile station. The system of claim 7, wherein
The system of determining the date and time of the first base station is made in connection with a frame synchronization epoch present in a mobile communication signal transmitted from the first base station. The system of claim 7, wherein
The portable communication link is a system that uses one of the GSM communication standard, the PDC communication standard, the North American IS-136 communication standard, the PHS communication standard, the AMPS analog communication standard, and the asynchronous wideband spread spectrum CDMA standard. The system of claim 7, wherein
The first mobile mobile station and the second mobile mobile station are the same station, and the first satellite positioning system receiver and the second satellite positioning system receiver are the same receiver. system. The system of claim 7, wherein
The first mobile mobile station and the second mobile mobile station are different separate stations, and the first satellite positioning system receiver and the second satellite positioning system receiver are different separate receivers. A system. The method of claim 1, wherein
A further method for determining a mobile mobile station time bias at a mobile mobile station incorporating satellite positioning system receivers located together;
This further method is
Placing the mobile mobile station close to the mobile base station simulator,
Synchronize the mobile base station simulator to an accurate time reference,
Determine the date and time of the mobile mobile station using the satellite positioning system receiver located together;
Determining the mobile mobile station time bias using the date and time;
A method of storing the mobile mobile station time bias in a memory attached to the mobile mobile station. The method of claim 15, wherein
The mobile mobile station is
A circuit substantially identical to the first mobile mobile station and its satellite positioning system receiver;
A method comprising the second mobile mobile station and circuitry substantially identical to the satellite positioning system receiver. A method for establishing time at a first base station in a mobile communication system, executed in a mobile mobile communication station, comprising:
Determining location information to determine the location of the mobile mobile communications station;
Determined with respect to a valid signal at the first base station, determining a time display to display a date and time at the mobile portable communication station;
Transmitting at least one of the location information and the location, transmitting the time indication from the mobile mobile communications station;
Here, the time indication, and at least one of the location information and the location are such that the first base station is synchronized with another base station in the mobile communication system. The method that is used to establish time in. The method of claim 17, wherein
The mobile portable communication station comprises a satellite positioning system receiver for determining the position information including at least a pseudo range for a satellite positioning system satellite;
The signal valid at the first base station is a mobile communication signal transmitted from the first base station to the mobile mobile communication station;
The method wherein the time display corresponds to a marker in the signal. The method of claim 18, wherein
The time display is
A method comprising at least one of sampling a satellite positioning system signal received by the satellite positioning system receiver and a date and time message in the satellite positioning system signal. The method of claim 19, wherein
A positioning server receives the position information, determines the location, and provides the position to the first base station. A method of establishing a time at a first base station of a mobile communication system that is performed remotely for a mobile mobile communication station, comprising:
Receiving from the mobile portable communication station a time indication that is determined in relation to a signal valid for the first base station and representing a date and time at the mobile portable communication station;
A method for determining a time at the first base station from the time indication so that the first base station is synchronized with another base station. The method of claim 21, wherein
The method, wherein the signal is a mobile communication signal transmitted from the first base station to the mobile mobile communication station. 23. The method of claim 22, wherein
Further, receiving the location of the mobile portable communication station, and the time at the first base station is also the location of the mobile portable communication station and a known predetermined location of the first base station The method determined from 24. The method of claim 23, wherein
The mobile mobile communication station is not fixed and the location is not predetermined,
The method wherein the location and the known predetermined location determine a propagation delay between the mobile portable communication station and the first base station. 25. The method of claim 24, wherein
The other base station synchronizes with the first base station by receiving another time indication from at least one of the mobile portable communication station and the other mobile portable communication station;
The other time display and the time display are based on the same time standard. 26. The method of claim 25, wherein the same time standard is GPS time. In a base station apparatus used in a mobile communication system,
A wireless portable transceiver,
A network interface coupled to the wireless portable transceiver;
A watch coupled to the wireless portable transceiver;
The wireless portable transceiver receives a time indication from the remote mobile portable communication station for displaying a time indicating the date and time at the mobile portable communication station;
The time indication is determined in relation to a signal valid for the base station device;
A base station apparatus in which a time for the clock is determined from the time display so that the base station apparatus is synchronized with other base stations. The base station apparatus according to claim 27,
The base station apparatus, wherein the signal is a portable communication signal transmitted from the base station apparatus to the mobile portable communication station. The base station apparatus according to claim 28,
The network interface transmits land-based communication to the mobile mobile communication station through the wireless mobile transceiver;
The wireless portable transceiver receives a location of the mobile portable communication station;
A base station apparatus in which the time for the clock is also determined from the location and a known predetermined location of the first base station. The base station apparatus according to claim 29,
Adding a digital processing system coupled to the watch, the wireless portable transceiver and at least one of the network interfaces;
The digital processing system includes:
A base station apparatus that determines a propagation delay from the location and the known predetermined location, and sets the time or adjusts the clock using the propagation delay and the time display. The base station apparatus according to claim 28,
The other base station is synchronized with the base station device by receiving another time indication from at least one of the mobile portable communication station and the other mobile portable communication station,
The other time display and the time display are base station apparatuses based on the same time standard. In mobile and mobile communication stations
A wireless portable transceiver and a satellite positioning system receiver coupled to the wireless portable transceiver;
The satellite positioning system receiver represents a date and time at the mobile portable communication station and determines a time indication determined in relation to a valid signal for the base station;
The wireless portable transceiver transmits the time indication to the base station;
A mobile portable communication station in which the time indication is used to establish time at the base station so that the base station can synchronize with other base stations capable of wireless communication with the mobile portable communication system. The mobile mobile communication station according to claim 32,
The satellite positioning system receiver determines the location;
The wireless portable transceiver transmits the location to the base station;
The signal is a mobile communication signal transmitted from the base station to the mobile mobile communication station,
The time display is a mobile portable communication station associated with a marker in the signal. 34. A mobile portable communication station according to claim 33.
The mobile display station is a time and date message of a satellite positioning system signal received by the satellite positioning system receiver.

Images