MXPA06001157A - Location determination of a local transmitter using a database. - Google Patents

Abstract

A method and apparatus for identifying wireless communication base stations from incomplete signal data reported by a Mobile Station (MS). In one embodiment, a database includes a plurality of key BTS data entries, each key BTS data entry including a unique global identifier that uniquely identifies a BTS in the system, and wherein the BTS database further includes associated data entries corresponding to and associated with each key BTS data entry. BTS signal data is obtained from an MS, the BTS signal data including a unique identifier of a first BTS and at least partial identifying information for at least one BTS other than the first BTS. A match is determined between the first associated data entries and the BTS signal data, and a second BTS is identified responsive to the match.

Description

DETERMINATION OF LOCATION OF A LOCAL TRANSMITTER USING A DATABASE FIELD OF THE INVENTION The method and apparatus described relate to location services for mobile communication devices, and very particularly to a system and method for determining the location of transmitters that transmit signals used to locate a mobile station.

BACKGROUND OF THE INVENTION Location services (abbreviated as LCS, for "Location Services") for wireless communication devices, referred to as Mobile Stations (MS), are an increasingly important business area for wireless communication providers. The location information can be used to provide a variety of location services to MS users. For example, public safety authorities may use location information to locate the precise geographic location of an MS. Alternatively, an MS user may use the location information to locate the nearest ATM, as well as the charge made by that ATM. Another example, location information can help a traveler get step-by-step directions from a desired destination while on the road. Technologies that allow a large number of system users to share a wireless communication system play an important role in meeting the increasing demands of mobile computing, including the demands of location services. Such systems include Code Division Multiple Access (CDMA) and broadband CDMA (WCDMA) technology, for example. As is well known, CDMA and WCDMA communication devices are assigned a pseudo noise code (PN) or sequence. Each device uses its PN code to spread its communication signals through a common scattered-spectrum frequency band. Whenever each communication device uses the correct code, each of said devices can successfully detect and select a desired signal from among the signals simultaneously transmitted within the same frequency band. Two types of positioning systems are commonly known. The first is called a positioning system based on MS. In MS-based positioning systems, the calculations for determining the MS location are made within the MS. The second is called an MS-assisted positioning system. In MS-assisted positioning systems, the network provides assistance data to the MS to allow location measurements and / or to improve measurement performance by the MS. The MS provides the signal measurements to the network. A component of the network then performs a calculation of the location of the MS. A particular method of MS-assisted positioning employs the Global Positioning System (GPS) and is referred to as "assisted GPS" or simply AGPS. According to the AGPS method, the MS acquires measurements from GPS satellites (commonly referred to as "GPS measurements") using assistance data provided by the network. In addition to GPS measurements, the MS acquires terrestrial measurements, such as forward link measurements from a ground reference station, such as the Base Station Transceiver (BTS). The "forward link" refers to the communications transmitted from the MS and received by the BTS. Terrestrial measurements can also be acquired in the reverse link, measured in the BTS. Other measurements include altitude assistance and timing information. In MS-assisted operation, regardless of the origin of said measurement information, all measurements made for the purpose of servicing a location request are typically sent to a position determination entity (PDE) for geolocation calculations. A method that can be used in conjunction with GPS or AGPS systems is commonly referred to as Advanced Advance Link Trilateration (AFLT). This is a geolocation technique that uses the measured arrival time (TAO) of the radio signals transmitted from a plurality of BTS and received by an MS. Other methods that use TOA include Enhanced Observed Time Difference (E-OTD) and Observed Time Difference in Arrival (OTDOA). To execute TOA-based geolocation techniques, the MS "reports" the reception of signals transmitted from the BTS. The MS can provide a PDE with PN measurement data for each BTS signal it receives. The PN measurement data is derived from a sequence of coherent phase data. The data is commonly referred to as "chips." The chip sequence is commonly referred to as a sequence of pilot chips. The signal carrying the pilot chip sequence is commonly referred to as a pilot signal. The methods for the MS to acquire the pilot signals are well known to those skilled in the art of wireless communications. Within a given geographical region, each BTS periodically transmits the same pseudonoise (PN) code pilot signal, but with a different time offset. That is, each BTS transmits the same PN code. However, the start of transmission of the PN code of each BTS is delayed in time by a different compensation known with precision with respect to a common timing reference. Because different BTSs transmit PN codes with different compensations, the PN compensation of a pilot signal can be used to identify the corresponding BTS. Consequently, a PDE can identify the BTS that have transmitted signals received by an MS by reference to a database that relates the identities of the BTS with a PN compensation. It should be noted for brevity purposes, that reference is made to the "signal PN compensation" being transmitted instead of the PN compensation of the beginning of the modulated PN code in the signal. Alternatively, other variations in the PN code may be used to distinguish the signals transmitted by different BTS. The PN compensation can typically be measured in the incoming signals received from a BTS. A database known to those skilled in the art is a Base Station Almanac (BSA), which contains information on the terrestrial wireless network. In particular, the BSA can relate the location of a BTS with the PN compensation of signals transmitted by that BTS. Unfortunately, due to the limited number of available PN compensations, some BTS are assigned to transmit signals with the same PN compensation. However, BTSs that transmit signals with the same PN offsets are usually far enough away from each other that no MS can receive signals from two BTSs to which the same PN compensation has been assigned. However, PN compensation alone may be insufficient to uniquely identify a BTS because an MS may receive signals from a remote BTS having the same PN offset as a closer BTS. In addition to the problems in the unique identification of the BTS from which signals were transmitted, the relatively large number of BTS in a typical system results in a significant amount of time spent searching through a database for identify the particular BTS you are transmitting. A precise determination of the location of the MS requires accurate information regarding the location of each BTS from which the MS receives signals. This, in turn, requires the quick and unique identification of each BTS from which a signal is being received. Therefore, it can be appreciated that there is a prevailing need for improved methods by means of which the transmitters can be identified using the limited data received by an MS. Accordingly, there is a need for a method and apparatus for determining the location of the BTS that can be "heard" by an MS.

SUMMARY OF THE INVENTION A system and method for determining the location of signal transmitters is described, such as Base Station Transceivers (BTS) reported by a Mobile Station (MS). In one embodiment of the disclosed method and apparatus, a database includes a plurality of key BTS data entries. The term "key" is used to indicate that the key BTS data entry is used as a "search key" to assist in the identification of the particular record of interest within the database. Each key BTS data entry corresponds to a unique BTS in the system. The BTS database also includes associated data entries corresponding to, and associated with, each key BTS data entry. This associated data entry is the Neighbor List to store "neighbor" BTS data, including pseudo-random noise (PN) compensations of signals transmitted by BTS that are geographically close to the BTS corresponding to the BTS key entry. Another associated data entry is the Audible List for storing "Audible" BTS data, including the PN compensation of signals transmitted by the BTS and received by an MS, and not transmitted by the BTS in the Neighbor list. Even another associated data entry is referred to as the Remaining List to store the "Remaining" BTS data, including PN offsets transmitted by the BTS that do not belong to the Neighbor List or Audible List, but which may be potentially received by an MS . An additional associated data entry includes a threshold whose use will be more evident below. According to one embodiment of the described method and apparatus, the data is received from an MS. The BTS data includes a unique identifier associated with a "primary service" BTS. In one embodiment of the described method and apparatus, the unique identifier could be the SID / NID / Base ID or in another mode the identifier could be the Switch Number, the Market ID and / or the Base ID. The BTS data also includes pseudo-random noise (PN) data associated with both the primary service BTS and other BTS. These other BTSs will hereafter be referred to as BTS "that do not provide service". However, it will be understood that some of these BTS that do not provide service may, in fact, be BTS secondary service. That is, they can provide a communication link between the MS and a communication network. In addition, the BTS data includes an indication of the power of the signals transmitted by other BTSs and received by the MS. A comparison is sought between the unique identifier received and the key BTS data entries within the database. Once the comparison is made, the location of the primary service BTS identified by the key BTS data entry is known from the primary service BTS data associated with that key BTS data entry. Next, we examine the data associated with the signals that are reported by the MS as received by the MS from the BTS that does not provide service. The examination is performed to determine if the power of the signal reported by the MS for each BTS signal that does not provide service is greater than the threshold associated with the primary service BTS in the database. If so, then the method checks whether the PN compensation of the signals transmitted by the non-serving BTS matches the PN compensation stored in the Neighbor List. The PN compensation of the signals transmitted by the BTS that do not provide service is considered as ambiguous identification data, because the PN compensations can be associated with more than one particular BTS. However, other identification data may also be considered ambiguous. For example, a "System Identification" (SID) number can be assigned to more than one BTS, making the SID ambiguous with respect to identifying the BTS associated with that SID. Therefore, any information that identifies two or more sources is considered ambiguous identification data for the purposes of this description. According to one embodiment of the described method and apparatus, it can be assumed that the PN compensation of a signal having a signal power that is above the threshold will coincide with a PN offset associated with a Neighbor BTS listed in the Neighbor List. In another mode, if: (1) the signal strength is above the threshold; (2) the PN compensation is not in the Neighbor List, and (3) the PN compensation is in one of the other lists, then the input associated with the PN compensation is moved from the list where the compensation is found. PN to the Neighbor List. In this way, the Neighbor List can be built dynamically instead of having to be downloaded from the BTS, or other BTS network database equipment. However, if the signal strength is not greater than the threshold, then we can not assume that the PN compensation will be in the Neighbor List. Accordingly, even if the PN compensation associated with a BTS that does not provide service matches the PN compensation of a BTS listed in the Neighbor List associated with the primary service BTS, a confirmation of that PN compensation is required. That is, an additional step is executed to confirm that the PN compensation indicates that the BTS associated with that PN compensation in the database is the same as the BTS associated with the PN compensation sent by the MS. In one embodiment, this confirmation is made by determining the probability that the BTS associated with the PN compensation in the database transmitted the signal having the associated PN compensation. In an alternative embodiment of the described method and apparatus, the confirmation step may be omitted. However, then there would be an opportunity for the coincidence to be wrong. Any erroneous matches would result in the location being incorrectly determined from at least some of the BTSs from which the MS is receiving signals. If the PN compensation sent by the MS does not match any PN compensation stored in the Neighbor List, then a match is sought between the PN offsets stored in the Audible List entry. In one embodiment of the method and apparatus described, if such a match is found, then the match is confirmed. However, in another modality, the coincidence can be assumed as correct with some risk that this assumption is wrong. If the PN compensation sent by the MS does not match any PN compensation stored in the Audible List entry, then a match is sought between the PN offsets stored in the Remaining List. If a match is found, then according to one embodiment of the described method and apparatus, the match is confirmed through an additional step. Alternatively, the match could be assumed to be correct without further confirmation. In response to the determination that there is a match, all data associated with the PN offset is transferred from the Remaining List to the Audible List.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 is a functional block diagram of a wireless communication system for providing wireless communications including location services.

Figure 2 is a functional block diagram of a wireless communication system for providing wireless communications including location services, showing additional components. Figure 3 is a conceptual illustration of a database, which is shown in the form of a table. Figure 4 is a flow diagram illustrating a method for identifying base station transceivers in accordance with signal data reported by a Mobile Station (MS). Figures 5 and 6 comprise a unit flow diagram illustrating a second method for identifying the base station transceivers in accordance with the signal data reported by an MS. Figure 7 illustrates a system that performs a statistical analysis based on the amount of overlap in the coverage areas between a Primary Service Base Station (BTS) Transceiver and a BTS represented by a particular set of entries to a database . Figure 8 illustrates the coverage area of a Primary service BTS. Figure 9 shows the calculation of the relative phase of signals received from different BTS.

DETAILED DESCRIPTION OF THE INVENTION Figure 1 illustrates a simplified general wireless communication system 100 that can be adapted to provide location services. As shown in Figure 1, a Mobile Station (MS) 102 communicates with the Base Station Transceivers (BTS) 112, 114, 116 and 142 through a plurality of wireless links 122. Although four of those BTS are shown. , it should be understood that MS 102 can communicate with one or more of those BTSs without limits in the number of said BTS. The MS 102 may be a cell phone, a cordless telephone, a personal digital assistant (PDA) with wireless communication capabilities, or any other mobile device for personal communication over a wireless connection. The MS 102 receives pilot signals transmitted by the BTS 112, 114, 116, 142. According to one embodiment of the method and apparatus described, the pilot signals, referred to herein as "pilots" are modulated with a "pseudo-random noise" code. (PN). In another embodiment of the described method and apparatus, the pilots can be any signal that allows the identification of the BTS based on some characteristic of the signal. In a mode where the pilot is modulated with a PN code, the PN code is a chain of digital values. The modulation of the pilots with said PN codes is commonly used to allow the Multiple Division by Code Division communication systems to discriminate between different signals sent on the same frequency. Furthermore, in CDMA cellular telephone systems it is common to modulate the pilot signals transmitted by many, or all, of the BTS in the system with the same PN code. To distinguish the pilot transmitted by a BTS from the pilots transmitted by other BTS, the PN code of each BTS has a time compensation that is unique to the particular BTS that it is transmitting. The compensations are called, each, like a common clock. Therefore, in determining the particular time compensation with respect to the common clock, the MS can determine which BTS transmitted that pilot. However, in most of these systems, the same compensation is assigned to more than one BTS according to an allocation plan. According to the allocation plan, the BTS that have the same assigned compensation should be far enough away from each other so that the signals transmitted by them can not be received by the same MS, for purposes of ordinary communications. Therefore, in theory there should be no ambiguity when attempting to use compensation to determine which particular BTS a pilot has transmitted that an MS received at signal levels powerful enough for communication. Nevertheless, in practice, a potential for ambiguity remains. This is especially true in cases where an MS can detect signals weaker than those used for ordinary communication purposes, and therefore can detect signals that are coming from a location further away than the plan for early communication assignment. In any case, such potential ambiguities have to be considered when attempting to identify the location of a pilot's source for the purpose of using that pilot to locate an MS. The BTS 112, 114 and 116 are coupled to a Base Station Controller / Mobile Switching Center (BSC / MSC) 110. The BSC / MSC is coupled to a Position Determination Entity (PDE) 130. The PDE 130 can be incorporate into other components of a communication system (such as a BSC / MSC, a Communication Service Provider Network 150, or some combination thereof). The PDE 130 can provide location services to multiple devices (such as a plurality of MSs similar to MS 102) communicating through multiple BSC / MSC, and BTS, such as BSC / MSC 140 and BTS 112, 114, 116 and 142. In an alternative mode, the location of the MS 102 can only be determined by processing what occurs within the MS itself. In one embodiment of the described method and apparatus, the information required to locate all the BTSs can be stored in a centralized PDE, instead of the MS 102. However, said data could be stored anywhere where it could be accessed. the same, including in the MS 102. In this example, the BTS 142 is connected to a separate BSC / MSC 140 to illustrate that a typical cellular telephone system will include more than one BSC / MSC. The BSC / MSC 110, 140 provides an interface between the BTS and other network elements, such as the PDE 130 and a communication service provider network 150, such as a Public Switched Telephone Network (PSTN). In addition to the signals received from the BTSs, the MS 102 may also receive signals (such as GPS signals) from one or more sources (such as satellites) 126 and 128 through communication links 123 and 124. Similarly, the BSC / MSC 110 can also receive signals, such as GPS signals, from one or more satellites 126 and 128 through communication links 123 and 124. Although exemplary are two satellites, a satellite or a plurality could be employed. of satellites and / or other sources, or no satellite when providing location services to an MS.

In addition, although the satellites are shown communicating with the BSC / MSC 110, those skilled in the wireless communication art will understand that the satellite data may also be received by other receivers (not shown) such as an Area Reference Network. Wide (WARN). The BSC / MSC 110 and 140 are connected to the network of the communication service provider 150 to receive and transmit data such as audio / video / text communication and programming data, position requests or WARN data. Figure 2 provides additional details regarding the components within the MS 102 and the PDE 130. For simplicity, the GPS satellites that can be used in a positioning system, and their associated communication links, are not shown in Figure 2 The PDE 130 has a memory 234, and a processor 232 that controls the operation of the PDE 130. The term "processor", as used in this description, is intended to encompass any processing device, alone or in combination with other devices ( such as a memory), which has the ability to control the operation of a device where it is included (such as a PDE 130, an MS 102, a BSC / MSC 110, or a portion thereof). For example, a processor, such as processor 232, may include microprocessors, integrated controllers, application-specific integrated circuits (ASICs), digital signal processors (DSPs), state machines, discrete dedicated hardware, and the like. The system, apparatus, and method described in the present invention are not limited by the specific hardware component selected to run the processor 232. The memories 234 and 206 may include read-only memory (ROM) components, random access memories ( RAM), non-volatile RAM components or any other means through which information can be stored and which can be accessed later. The memory 234 stores and provides instructions and data for the processor 232. The components of the PDE 130 are linked together by an internal interconnection system 236, and the components of the MS 102 are linked together by means of an interconnection system. 207. As described in greater detail below, the memory 234 includes a database used to locate the signal source (ie, the BTSs) in accordance with a PN offset provided by the MS 102. As shown in FIG. Figure 2, the MS 102 includes a processor 204, a memory 206, and a transceiver 208. The memory 206 stores and provides instructions and data for the processor 204. The transceiver 208 allows the transmission and / or reception of data, such as audio, video, text and programming data, between MS 102 and a remote location, such as BTS 112, 114, 116 and 142, or GPS satellites (not shown). An antenna 209 is coupled to the transceiver 208. The basic operation of the MS 102 is well known in the art and does not have to be described further. The PDE 130 may have a stored database that maps the PN compensation to the location of an associated BTS. As noted above, CDMA systems commonly use pilot PN offsets as a means to identify BTS. PN offsets are commonly referred to as "PN transmission sequence offsets". In another embodiment, the signals transmitted by different BTS can be distinguished based on the values of the PN code or any other attribute of the modulation of the signals instead of the PN compensation. In one embodiment, the database may be stored in memory 234. However, in another embodiment, the database may be stored in memory 206 within MS 102. For this mode, MS 102 may require information related to the location of the BTS from where a pilot that has a particular PN compensation is located. This information can come from a BSC / MSC, a PDE, or another location. Fig. 3 is a conceptual illustration of a database, shown in the form of a frame 300. Frame 300 contains a number of registers 301, 303, 305. Each register 301, 303, 305 includes a key BTS entry 302 for store key BTS data entries. The data stored in each key BTS data entry 302 refers to a particular "primary service" BTS. The primary service BTS is that BTS with which the MS 102 was registered. The "registration" refers to the network that registers that the MS 102 is communicating with the network through a particular BTS. In the case where the MS 102 is registered with more than one BTS, the primary service BTS should be the BTS from where the MS 102 is receiving the strongest signal, or alternatively, the primary service BTS would be arbitrarily designated from all the BTSs with which the MS 102 is registered. In one embodiment, each key BTS data entry 302 includes at least two sub-fields. The first subfield 307 is referred to herein as the PN data subfield. The PN 307 data sub-field includes PN data, such as PN compensation, used to determine with which BTS 112, 114, 116, 142 MS 102 is registered. The phrase "PN data" can generally be used to refer to the information such as: 1) the compensation of the start of a modulated PN code in a carrier signal transmitted by a BTS, 2) the particular PN code modulated in a carrier signal transmitted by a BTS, or 3) any other information modulated in a signal carrier transmitted by a BTS from which the signals transmitted by different BTS can be distinguished from each other, whether or not that information refers to a pseudo-random noise code. However, for purposes of clarity and simplicity, the method and apparatus presented herein are described using PN compensation as the particular type of PN data. Accordingly, in one embodiment of the described method and apparatus, the data stored in the key BTS data entry 302 includes the PN compensation of the start of the modulated PN code in the signals transmitted by the primary service BTS. For purposes of simplicity and brevity, reference will simply be made to the "PN compensation of the signals" instead of the longer phrase "PN compensation of the start of the PN code modulated in the signals". However, those skilled in the art will understand that the first sentence means the same as the second sentence. In addition, the key BTS data entry 302 includes the location of the primary service BTS. Although the information in the key BTS data entry 302 typically relates to the primary service BTS, the key BTS data entry 302 may include PN compensation of the signals transmitted by a BTS other than the primary service BTS. For example, PN compensation can be associated with a secondary service BTS. The second sub-field 309 is referred to as the Location sub-field of the Service BTS. In the example shown in Figure 3, the Location sub-field of Service BTS 309 provides the location of the primary service BTS. The location can be provided in any particular format and / or form that makes the location information useful at least for the purpose of identifying where a signal transmitted by the BTS originated. The location is provided to use said signals to help determine the location of a receiving MS 102. For the purpose of method and apparatus described, the location of the MS 102 could be determined using any of the following methods: 1) arrival time method, 2) arrival time difference method, 3) arrival angle method , 4) triangulation method, 5) trilateration method or 6) any other method that could benefit from knowing the location of a source of a transmitted signal. further, in some embodiments, the information identifying the primary service BTS could also be included in one or more additional subfields (not shown) in the BTS key data entry 302. In one embodiment, the BTS data entries key can also include other data relevant to the BTS. Associated with each key BTS data entry 302 (ie, contained within the same register 301, 303, or 305 as the key BTS data entry) are associated data entries. According to one embodiment of the described method and apparatus, for each key BTS data entry 302, there is an associated Neighbor List 311. Neighbor List 311 includes two sub-fields. The first sub-field is the sub-field of data PN Vecino 313. The second sub-field is the sub-field of location Neighbor 315. In a modality of the described method and apparatus, there is a one-to-one correspondence between the entries in the Neighbor PN data sub-field 313 and the entries in the location subfield 315. The Neighbor PN 313 data sub-field includes the PN compensation of the signals transmitted by a Neighbor BTS. The corresponding Neighbor sub-field 315 includes the location of that neighboring BTS. For example, Figure 3 shows a database that has n BTS Neighbors. Each Neighbor BTS has a corresponding Neighbor PN 317 data entry and a corresponding Neighbor location entry 319 in database 300. In Figure 3 ellipses are shown between the first data sub-field PN Vecino 317 and the subvoice ship. PN 318 data field to indicate that there are at least 2 additional PN data entries that are not expressly shown. Similarly, the ellipses are shown between the location data entry Neighbor 319 and the location data entry Neighbor 320. A first sub-field entry of Neighbor Location 319 corresponds to, and locates the BTS that transmitted the signal with the PN compensation that resides in the first input of the PN Vecina 317 data sub-field. A sub-field input from neighboring location 320 corresponds to, and locates the BTS that transmitted the signal with the PN compensation that resides in the ship neighbor data sub-field entry PN 318. The associated data entries also include an "Audible List" 322 associated with a particular primary service BTS identified in the key BTS data entry 302 within the same record 301, 303, 305 The Audible List 322 shown in Figure 3 includes two sub-fields with m entries in each sub-field. The first sub-field is the Audible PN data sub-field 321. The Audible PN data sub-field 321 includes a first Audible PN data entry 325 separated by ellipses from an input PN-Audible PN-data sub-field 327. The ellipses indicate the existence of m entries within subfield 321. The second subfield is the subfield of Audible location 323, including a first entry 329 to the subfield of Audible location 323 separated by ellipses of a jsava Audible PN data sub-field entry 331 to indicate the existence of m entries within the Audible Location 323 sub-field. The data in Audible List 322 allows BTS to be located that: 1) have transmitted signals received by an MS 102 that is currently receiving service from the BTS corresponding to the entry of key BTS data 302 within the same registry 301, 303, 305; and 2) are not in Neighbor List 311. Associated data entries also include a "Remaining BTS List" 333. Remaining BTS List 333 identifies a set of BTS that are not identified in either Neighbor List 311 or the List BTS Audible 322. Further, according to one embodiment of the described method and apparatus, to be included in the Remaining BTS List 333, a BTS should be detectable by an MS 102 that is receiving service from the primary service BTS responsible for the transmission of the signal having the PN compensation indicated in the key BTS data entry 302. In a particular embodiment, any BTS in the system is considered as potentially detectable. In another modality still, all the BTS in the system are included in the Remaining List excluding those listed in the Neighbor or Audible Lists.

The Remaining BTS List 333 includes two sub-fields. The first is a PN BTS sub-field Remaining 335. The second is the sub-field of Remaining BTS Location 337. The sub-field PN BTS Remaining 335 includes several sub-field PN Remaining BTS entries as shown in the figure 3 by means of the ellipses between a first sub-field entry PN BTS Remaining 339 and a fine subfield entry PN BTS Remaining 341. Similarly, the Sub-field of Location of the Remaining BTS includes several sub-field entries of the Remaining BTS as shown in Figure 3 by means of the ellipses between a first sub-field entry of Location of the Remaining BTS 343 and a 1st Subfield of Location BTS Remaining 345. Each of the entries in the sub-field of Location of BTS Remaining 337 provides the location of the BTS that is transmitting the PN code indicated in the corresponding entry of the sub-field of PN BTS Remaining 335. Although the modality shown in Figure 3 is shown as storing only the PN compensation and the BTS location in each of the Lists, the Neighbor List 311, the Audible BTS List 322 and the Remaining BTS List 333 may each one, include any combination of PN compensation, PN code and / or data belonging to other attributes, such as, for example, a unique global identifier, geographic coordinates, altitude information, antennas range a, etc., that can be used for position determination purposes. Accordingly, the table 300 may optionally contain additional fields, and may refer to other databases or tables, or may contain all the fields described herein. For example, in one modality, there may be one or more separate databases that contain a Remaining List. In this mode, box 300 could contain a field that references the desired Remaining List in the external database. In this mode, the PDE 130 (Figure 2) or a processor located in another device searches for the corresponding BTS Remaining data in another database or table, instead of storing them in field 333. Other servers, such as those in the BSC / MSC 110 or 140, may maintain separate databases and information retrieved by the PDE 130, as necessary. In still another embodiment, the database represented by the table 300 could be incorporated into the MS 102. In this mode, according to the methods described in more detail below, the MS 102 can identify the BTS based on the compensation PN and report the location of the BTS to the PDE 130, instead of reporting only the PN compensation. Figure 4 is a flow chart illustrating a method for identifying BTS according to the PN compensation reported by an MS. The method can be employed, for example, by the system 100 shown in Fig. 2. It should be noted that, although this example illustrates the method and apparatus described using the PN compensation, other forms of ambiguous transmitter could be used. identify the information. The method is started in step 402, where a database of the BTS is created, such as the database 300. In step 404, the data is obtained from an MS. Typically, the MS will provide the information when it is requested that its position be determined. According to one embodiment of the disclosed method and apparatus, the data includes a unique Global Identifier that identifies the service BTS. The Global Identifier is included in the information modulated in the signals transmitted to the MS by the service BTS. Accordingly, the MS will receive and demodulate the modulated Global Identifier in the signals transmitted by the service base station. In addition, the MS sends a set of PN compensations designated by PNi (i = l, n), where i is an index that indicates a particular case of n PN compensation cases. Each case of PN compensation is associated with a BTS of which the MS receives signals. The value n is the BTS number from which the MS receives signals. The data is provided to a processor. The processor may be incorporated in a PDE or an MS, such as processor 204 or processor 232 of Figure 2. The processor is coupled to the database to receive and store data. The method then proceeds to step 406. In step 406, the processor finds the key BTS data entry 302 in the database 300 having the unique ID that matches the unique ID obtained from the MS. The method then proceeds to step 408. In step 408, a counter is started by setting the index i = 1. The method then proceeds to step 410. In step 410, the power of the signal received by the MS with a PN PNi compensation is compared to a desired threshold level (THRESH ). According to one embodiment of the described method and apparatus, the value used for THRESH may be the minimum signal level that is required to allow an assumption to be made that the transmission source (i.e., the BTS) is sufficiently near the service BTS to be considered as a communications neighbor of the service BTS. A particular parameter that could be useful is TT_ADD. TT_ADD is a typical value for the power threshold of the signal T_ADD. TT_ADD reduces the variations in T_ADD, because T_ADD can vary in different systems or locations. In another embodiment of the described method and apparatus, THRESH may be the particular T_ADD for the system and location where the MS is operating. In this case, the particular level T__ADD to be used for THRESH may be stored in a field associated with the key BTS data entry 302 of Figure 3. Alternatively, THRESH may be stored in a sub-field of the BTS data entry. key 302. If the signal strength for the signal having a PN offset equal to PNi is greater than THRESH, the method proceeds to step 412. In step 412 the corresponding entry PNi is identified in the Neighbor List 311. The value of compensation, PN¿, should be present in the Neighbor List 311, because it can be assumed that any signal, having a power greater than THRESH, has originated within the area associated with the BTS Neighbors. Therefore, there should be no ambiguity regarding the mapping of the PN compensation and a Neighbor BTS. However, if the PN compensation is not identified in the Neighbor List 311, then the PN compensation is searched among the other lists in step 413. If found, then the information associated with PN is moved to the Neighbor List. 311. According to one modality of the described method and apparatus, the information to be moved includes the compensation P and the location of the BTS from which that PN was transmitted. From step 412 the method proceeds to step 428 where the method determines whether the most recent value of PNi is the last value to be considered (ie, wi "= wn"). If the answer is YES, the method advances to step 432, which ends the method. If the answer is NO, the method proceeds to step 430 where the Index "i" is incremented, and then returns to step 410. If the signal strength is equal to, or less than THESH, the method advances from step 410 to step 414. In step 414, a search is made in Neighbor List 311 to determine whether there is a match with the PN compensation. Even if the signal strength is below the threshold level, such a coincidence may occur if the signal from a Neighbor BTS is blocked by a building or other obstacle. If there is a match, the method proceeds to step 416. If not, then the method proceeds to step 418. It should be noted that there is a relatively high chance that PNÍ matches one of entries 317, 318 in the Neighbor List 311, because many of the BTSs from which MS 102 will receive signals will be on Neighbor List 311. However, this assumes that Neighbor List 311 has been fully compiled. In one embodiment of the described method and apparatus, Neighbor List 311 is generated by gathering reports that MSs have received signals from a BTS which are above THRESH.

In step 416, because the signal level was below the threshold level, a coverage and phase test (CPT) is applied to the PN compensation to determine whether PNÍ corresponds to a Neighbor BTS. The CPT is executed because it is possible for two BTS to have identical PN¿ compensation. The CPT confirms whether a signal having a particular PN compensation value found in Neighbor List 311 was actually transmitted by a Neighbor BTS or was transmitted by a BTS that is remote, which would allow that BTS to qualify as a Neighbor BTS. An "YES" in response to this test means and confirms that the PN compensation has been unequivocally identified by the CPT as coming from a Neighbor BTS. If the answer in step 416 is YES, the method proceeds to step 428. If the answer is NO, the method proceeds to step 418. The CPT test is described in more detail below. Therefore, for purposes of clarity, at this point no more information about the CPT is provided. In step 418 the Audible List 322 is subjected to search to determine if there is a match or matches for the compensation. As described in more detail below, the Audible data is initially empty, and these entries are occupied as a result of the operation of the described method. If the answer in step 418 is YES, the method proceeds to step 420. If the answer is NO, the method proceeds to step 422. In step 420, a CPT is applied to the P compensation to confirm a positive match in the step 418. As indicated above, more than one match can be found for the PNI compensation in step 418 above. An "YES" in response to this test means that the PNI compensation has been unequivocally identified by the CPT. If the answer in step 420 is YES, the method proceeds to step 428 for further processing. If the answer is NO, the method proceeds to step 422. In step 422, a search is performed on the remaining BTS data to determine if there is a match or matches for the PNI compensation. If the answer is YES, then the method proceeds to step 424. If the answer is NO (no match was found), the method proceeds to step 427. In step 424, a CPT is applied to the compensation P para to confirm a determination of positive identity for the match or matches identified in step 422. As noted above, more than one match may be found for the compensation P en in the previous step 422. In this case, the result of the CPT test will verify which , if there is one, the coincidences are correct. An "YES" in response to this test means that the PN compensation has been unequivocally identified by the CPT. If the answer in step 424 is YES, the method proceeds to step 426. If the answer is NO, the method proceeds to step 427 where the P compensation is labeled with the error flag. In step 426, the data for the remaining BTSs identified for the current PNI compensation are added to the Audible List 322. The addition to the Audible List 322 facilitates the identification of the BTS for future searches. This addition procedure to the Audible List 322 also improves the efficiency of the search procedure. This is because Remaining List 333 is a much larger data set than Audible List 322. By adding a new BTS to Audible List 322, the new BTS can be identified in the future without the need to search the Remaining List. 333 which is bigger. Therefore, according to one embodiment of the described method and apparatus, the addition to the database reduces the search time. The particular set of BTS that can be heard can change over time. Therefore, according to one modality of the described method and apparatus, BTS that have not been detected and reported recently are removed from the Audible List 322. The removal of the BTS improves the efficiency of the search and / or reduces the memory requirements. The determination can be executed regarding when to remove a BTS, for example, by timestamp entries each time they are detected by an MS that is receiving service from the service BTS identified by the key BTS data entry that resides in the same record with the Audible List 322. The entries may then be deleted if an MS has not detected them for a predetermined period of time. Alternatively, the location of the Audible BTS entries in the list can be modified by placing the most recently detected BTS at the top of the list. In this way, BTS that are not detected recently are sent to the bottom of the list and become suitable for elimination. A combination of these two approaches could also be employed. From step 426 the method proceeds to step 428. In step 427, the processor notifies the operator, by means of an error flag, or some other notification message, that a BTS corresponding to the current PN offset was not uniquely identified by the search procedure. The error flag alerts the operator to take corrective action. In particular, if the PN¿ compensation can not be uniquely identified, it should not be used to perform a location calculation. From step 427 the method proceeds to step 428. As noted above, in step 428 the data index i is tested to determine whether all offsets P han have been evaluated. If the answer is NO, the method advances to step 430, where the index i is incremented. The following compensation P es is identified by searching the database as described above. If the answer is YES, the method advances to step 432 and the procedure ends. Figures 5a and 5b comprise a unified flow diagram illustrating another operation of a system, such as system 100 of Figure 2, to locate the BTS based on data received from the S. The method starts at step 502, where a database is created, such as the database 300. At step 504, the data is obtained from an MS that requires its position to be determined. The data is provided to a processor, which can be incorporated into a PDE or an MS. The data is obtained from an MS that requires that its position be determined and provided to a processor. The procedure can be incorporated into a PDE or an MS. The processor is operatively connected to the database for receiving and storing data, and can be executed in a processor such as processor 204 or processor 232 of FIG. 2.

The data includes a Global Identifier (GI0) for at least one BTS signal received by the MS, and the PNI compensation (i = 1, n) of each received signal provided by the MS for evaluation, where n is the number of BTS signals provided by the MS for evaluation. The method then proceeds to step 506. In step 506, the processor finds the key BTS data entry in the database corresponding to the GI0. The method proceeds to step 508. In step 508, a counter is started by setting an index i = 1, and the method advances to step 510. In step 510, the signal strength of the signal having the compensation PN, P Í, (hereinafter "the signal that the PNÍ has") is compared with a THRESH signal power threshold level. If the signal strength for the signal having PNÍ is greater than THRESH, the method proceeds to step 512. In step 512, the P es is ordered in a "Candidate List", referred to as PNC data, and the method proceeds to step 516. In step 516, the index "i" is tested to determine whether all the PNIs for i equal through n have been ordered. If the answer is YES, the method advances to step 520. If the answer is NO, the method advances to step 518. In step 518 the index i is increased. The method then returns to step 510 and the classification procedure is repeated as described above. If in step 510 the power of the signal is less than or equal to THRESH, the method proceeds to step 514. In step 514, the PN is ordered in an "Unknown List", referred to as PNU, and the method proceeds to step 516. When the classification procedure executed by steps 510, 512, 514, 516 and 518 is complete, the PN¿ entries (i = 1, n) will have been classified into one of the two PNC sets (c = 1, cmax) or PNU (u = 1, ¾x), where cmax + umax = n. In step 520, it is assumed that all data in the PNC data is in Neighbor List 311. That assumption will typically be valid because it can be assumed that, any signal having a signal power exceeding THRESH has originated within of the nearby geographic areas associated with the BTS Neighbors. Therefore, there is no ambiguity regarding the mapping of the PN compensation and the BTS identities for the BTS Neighbors. The method then proceeds to step 524 (FIG. 5 (b)) through a stream connector 522. In step 524 (FIG. 5 (b)), the Index "u" is initialized by setting u = 1. The method advances then to step 526. In step 526 a search is made in Neighbor List 322 to determine if there is a match for the PNU data. Such a coincidence will occur, for example, when the signal from a Neighbor BTS is blocked by a building or other obstacle, causing the signal strength to fall below THRESH. If a match is found in step 526, the method proceeds to step 528. In step 528 a CPT is applied to the PNU data. An "YES" in response to this test means that the PNU has been unequivocally identified by the CPT. Accordingly, if the answer in step 528 is YES, then the procedure proceeds to step 540. In step 540, the u-index is tested to determine whether all PNU compensations have been evaluated. As noted above with reference to steps 510, 512, 514, 516 and 518, the entries in the PN¿ list (i = 1, n) were ordered in the PNC sets (c = 1, cmax) and PNU ( c = 1, Umax) t where cmax + umax = n. If the answer in step 540 is NO, the method proceeds to step 542 where the Index u is incremented, and the next PNU compensation is identified by database search as described above. If the answer in step 540 is YES, the method advances to step 544 and ends the procedure. Returning to step 526, if the response to step 526 is "NO", then the method advances to step 530. Similarly, if the response in step 528 is NO, the method proceeds to step 530. In step 530 it is performs a search on the Audible BTS data to determine if there is a match or matches for the PNU measurement. If the answer in step 530 is YES (the match was found), the method proceeds to step 532. In step 532 a CPT is applied to the PNU data to confirm a positive identity determination for the match or matches identified during step 530. An "YES" for response to this test means that the P compensation has been unequivocally identified by the CPT. If the answer in step 532 is YES, the method proceeds to step 540 for further processing as described below. If the answer is NO, the method proceeds to step 534. Returning to step 530, if the answer is NO (no match was found), the method proceeds to step 534. In step 534, a search is made in the Remaining List 333 to determine if there is a match or matches for the PNU measurement. If a match is found, the method proceeds to step 536. In step 536 a CPT is applied to the PNU compensation to confirm a positive identity determination for the match or matches identified in step 534. The CPT verifies which of the matches It is correct, if any. An "YES" in response to the CPT test means that the PNU has been unequivocally identified by the CPT. If the answer in step 536 is YES, the method advances to step 538. In step 538, the compensation for the remote BTS identified for the current PNU compensation is added to the Audible List 322. The method then proceeds to step 540 for additional processing as described below. Returning to step 534, if the answer is NO, the method advances to step 539. Similarly, if the answer in step 536 is NO, the method proceeds to step 539. In step 539, the processor notifies the operator by means of an error flag that a BTS corresponding to the current PNU compensation was not uniquely identified through the search procedure. The method then proceeds to step 540 and continues as noted above. The steps described above with reference to Figures 4, 5 (a) and 5 (b) can be executed by a processor within a PDE, such as the PDE 130 (Figure 2), using a processor such as the processor 232, which operates in accordance with software instructions stored in a memory such as memory 234. As noted above, in an alternative mode, the database may be located in an MS instead of the PDE. In this alternative embodiment, the method steps described above can be executed through a processor within an MS such as MS 102, using a processor such as processor 204, and a memory such as memory 206. In this mode , the MS reports the identities of the BTS to the PDE instead of reporting the PN compensation, in such a way that the PDE is not required to determine the identities of the BTS. As noted above, the CPT is used to select the correct entry from those stored in the location sub-fields Neighbors 315, Audible location sub-fields 323, or Sub-location fields Remaining 337 from within the location entries stored in the registry associated with the BTS entry key 302. You do not have to know the particular name or other identification information, such as SID / NID / Base ID of the BTS. What matters is that the entries within the database 300 have been correctly selected. This is important because the objective is to properly locate the source of the signals received by the MS. In an embodiment of the described method and apparatus, the relative arrival times of those signals are used, along with the location of the BTS from which the signals were sent, to determine the location of the MS. In an example of the described CPT, if the primary service BTS is located in Sea tle, Washington, then the MS 102 must be close enough to communicate with the primary service BTS. Therefore, MS 102 must be in or near Seattle. further, each BTS from which the MS is receiving signals must be close enough to the MS to allow the MS to receive those signals. Figure 7 illustrates a system 700. The system 700 comprises a CPU 702, a memory 704, a transceiver 712 that includes a transmitter 708 and a receiver 710, a signal analyzer 720, a statistical model 722 and a timer 724. The system 700 performs a statistical analysis based on the amount of overlap in the coverage areas between the primary service BTS and a BTS represented by a particular set of entries to the 300 database. This geographic region analysis helps determine the probability that the particular BTS represented by the set of inputs is the source of the signals received by the MS. Once the probability is determined, the CPT issues a decision concerning whether the MS received signals from that particular BTS. The system 700 can also execute a phase measurement analysis using relative phase measurements. The coverage overlap and the relative phase measurement procedures are described in more detail below. The system 700 is provided with information concerning one or more candidate BTS including, the compensation PN, BAND_CLASS (band class), and the frequency of the signals received by the MS 302. The system 700 can limit the list of candidates to the BTS that are located near the coverage area of the primary service BTS. The coverage area can be refined based on the identification of any other BTS that have previously been identified as BTS that transmitted signals received by MS 102. When the inputs associated with a first BTS have been uniquely identified, that information can be be used to uniquely identify the entries of the database 300 associated with other BTSs of which the MS 102 is receiving signals. As more and more entries are identified, additional information is provided to the 700 system to help identify additional entries, and therefore to locate the remaining BTSs of which MS 102 has received signals. In some cases, the analysis of the geographical region described above may be sufficient to uniquely locate the BTS from which signals associated with a particular PN compensation were transmitted. For example, there may be a single BTS represented by a PN offset that is located within the proximity of the primary service BTS. As previously discussed, the unique location of a BTS from which the MS 102 received signals may provide additional data used to locate additional BTSs from which the MS 102 has received signals. A one-dimensional probabilistic calculation is relatively easy to perform using a Gaussian distribution. The HEPE is based on an assumption that the density of the MS that listen to a BTS is distributed as a two-dimensional Gaussian distribution centered on the center of the BTS coverage area. System 700 can calculate two-dimensional probabilities to accommodate variations in the location of MS 102 in the north-south direction as well as variations in the east-west direction. To accommodate these two-dimensional probabilities, the system 700 calculates a value of "horizontal estimated position error" (HEPE) based on possible errors in two directions. In one example, the HEPE value of a known coverage area is calculated as the square root of the sum of squares of error calculations in each of the two directions. Assuming that MS 102 is located within a sigma (ie, one standard deviation) of the mean in a Gaussian distribution of the location of the MS, the HEPE value can be represented by the following: (1) in where s? 2 indicates an un-sigma error in the location of an MS in the north-south direction and s? 2 indicates an un-sigma error in the location of an MS in the east-west direction. Those skilled in the art will recognize that because the coverage areas are considered as circles, the HEPE value represents the diagonal of a square, where the sides of the square are equal in length to the radius of the circle. Figure 8 illustrates a coverage area 850 of a primary service BTS. Associated with area 850 is a HEPE value which is illustrated in figure 8 as ri. Because it is known that the MS 102 is within the coverage area of the primary service BTS, the coverage area of the primary service BTS may be referred to as a "known area" 850. In addition, the known area 850 may include the intersection of the coverage areas of the primary service BTS and the coverage area of other BTS. Accordingly, the known area 850 may be smaller than the coverage area of the primary service BTS if there is additional information available with respect to another BTS of which it is known that the MS 102 is receiving signals. Figure 8 also illustrates the coverage areas of three BTSs of which MS 102 could have received signals based on the fact that each has an identical PN offset of 25 (ie, 25 x 64 chips). The coverage areas 852 and 856 do not overlap with the area 850. In contrast, there is overlap between the coverage area 850 and a coverage area 854 corresponding to the candidate 2 of PN 25. The value of un-sigma for the candidate 2 of PN 25 is illustrated in Figure 8 by means of the value r2. The values ri and r2 indicate a metric to be used to determine the relative size of the coverage area 850 with respect to the candidate coverage area 854. The distance from the center of the coverage area 850 and the center of the coverage area 854 is illustrated in figure 8 by means of the reference D. The statistical model 722 (see figure 7) of the system 700 calculates a measurement of the separation of the coverage area using the relative size of the coverage areas and the distance D that separates the centers of the coverage areas. This separation can be represented by the following: D Separation? (2) where all the terms have been previously defined. A statistical evaluation of normal distribution can be performed from the end of equation (2) to generate a probabilistic measurement of separation between coverage area 850 and coverage area 854. Sometimes the normal distribution is calculated using the following: ND (x) = - = e 2 2p (3) wherein x is a representative number of the separation amount of a perfect overlap between the coverage area 850 and the coverage area 854. In one embodiment, the value x is chosen to be the Separation value of the equation (2) ). This equation can be simplified as follows: ND (x) = e 2 (4) where all the terms have been previously defined. As an example of the application of the model 722 that was illustrated above, consider that the values rx and? 2 are 2.0 and 1.0, respectively, while the distance D is 1.1. Note that these distances can be measured in convenient units, such as kilometers or miles. The insertion of these values in equation (2) provides a result of 0.49 for the separation. Substituting that value as x in equation (4) provides a result of 0.886. This indicates an 88.6% probability of a perfect overlap between coverage area 850 and coverage area 854. Note that a perfect overlap produces a result of 1.0. In contrast, the value of one-sigma for the coverage area 852, r2, is equal to 1.5 while the distance D between the center of the coverage area 852 and the center of the coverage area 850 is 4.0. The application of these values to equation (2) provides a result of 1.6 for the separation. Substituting that value in equation (4) provides a result of 0.278, which indicates a 27.8% probability of perfect overlap between coverage area 850 and coverage area 852. Therefore, it can be seen that there is a greater probability (ie, a greater tendency) that the signals received by the MS they were transmitted by the BTS in the center of the coverage area 854 then by the BTS either in the center of the coverage area 856 or the coverage area 852. The system 700 can eliminate the BTS based on the analysis only of the geographical region. However, those skilled in the art will recognize that there is a certain, albeit small, probability that the signals received by the MS could have been transmitted by the BTS in the center of the coverage area 852 or the coverage area 856. Therefore, , according to one embodiment of the described method and apparatus, the 700 system will only eliminate one candidate if the probabilities calculated using equation (4) differ by a factor of 10. That is, a candidate will be eliminated based solely on the overlap of the coverage area only if some other candidate is at least 10 times more likely to be the BTS detected. In the example illustrated above, candidate 2 is slightly more than three times as likely to be the BTS detected by MS 102 as candidate 1. Therefore, system 700 will perform an additional analysis to uniquely identify the BTS candidate. In one modality, system 700 will analyze any BTS candidate using equation (4) if the result of equation (2) is less than 8. This first step of analysis guarantees that even candidates with a very low probability of overlapping coverage they will be analyzed using equation (4). If the amount of one-sigma separation in equation (2) is equal to 8, the probability using equation (4) is very small. As a practical matter, the 700 system will eliminate any candidate whose one-sigma overlap has a large value. Typically this can occur in a situation where large distances separate the coverage area of a candidate BTS from the coverage area of the primary service BTS. For example, if coverage area 850 is in Seattle, Washington and another BTS is in San Francisco, California, the distance D that separates the two BTSs is so large that the probability of receiving the San Francisco BTS can be ignored. In addition to an overlap analysis of the coverage area described above, the system 700 uses a relative phase model to further reduce the list of candidate BTSs. The term "relative phase" is used to indicate the difference between the measurement phases between a known BTS and a reference BTS. This "relative phase" (when adjusted for known error margins, including PN compensation) should be approximately equal to the difference between the known BTS distance and MS 102, and a BTS candidate for MS 102. As discussed previously, each BTS transmits an identical PN sequence, but with known time delays or PN offsets. When two candidate BTS have identical PN compensation, the signal will be detected by MS 102 at different times (or phase compensations) based on the distance of the BTS candidate to MS 102. In one example, it is known that MS 102 is within the coverage region of the primary service BTS 112. If two candidate BTSs are also within that coverage region, it may be possible to eliminate one of the candidate BTSs based on the relative phase, which is indicative of the delay of propagation. For example, if a candidate BTS is within a 3.2 kilometer range of the Reference BTS while the other candidate BTS is within a 32.1 kilometer range of the primary service BTS, the relative phase between the two can often be used. to eliminate one of the candidate BTS. In a modality, the statistical model 722 (see figure 7) uses a relative phase model of double difference as shown below: ND ([[dK-dCi) - (pK-pC)] / SC) (5) where dK is the distance from the center of the combined coverage area (ie, the combined coverage area of the candidate BTS and the BTS from primary service to another BTS, whose location has been identified) to an already known BTS, dCi is the distance from the center of the combined coverage area to the candidate BTS iavo, pK is the phase measurement to the known BTS, pC is the measurement from phase to candidate BTS, and SC is the size of the expected double difference phase error based on the combined coverage area. The term "double difference" refers to a statistical calculation based on two difference measurements (that is, the difference in distance minus the difference in phase). The combined coverage area is a probabilistic measurement of the combined coverage areas of the known BTS and the candidate BTS. The details of the measurement of the combined coverage area are provided below. The relative phase model is used to determine if the phase lag measured by MS 102 is consistent with the distances between the known BTS and the candidate BTS. As discussed above, the known BTS can be the primary service BTS or any other measurement BTS that has already been uniquely identified. The example presented above is a technique that can be used to determine these relative phase differences. Those skilled in the art will recognize that other techniques can be employed to determine such phase differences. The present invention is not limited to the specific analysis described above to determine the relative phase differences. The calculation of the relative phase is illustrated in Figure 9 wherein the approximate center of a combined coverage area 960 is indicated by the reference number 964. The distance dK is the distance between the center 964 of the combined coverage area 960 and a known BTS 966. As discussed above, the known BTS 966 may be the primary service BTS or any other uniquely identified BTS. A candidate BTS 968 has a coverage area 962, which in this example is configured as a circle. As shown in Figure 9, the candidate BTS 968 is not located in the center of the candidate coverage area 962. This is due to the fact that a typical BTS is not omnidirectional, but is separated into a number of sectors. The sector could be configured by the 700 system as a pie-shaped sector. However, such a configuration is often inaccurate due to the return dispersion of the antenna, as well as the reflection of buildings, natural terrain, and other objects. Therefore, the candidate coverage area 962 can be configured as a circle. Similarly, the known BTS 966 is typically not located in the center of the known coverage area (which is not shown in Figure 9) for the reasons discussed above. The coverage area of each BTS (or each cell sector) is determined at the time of installation and is known about it. The combined coverage area, which indicates the coverage area of the known BTS 966 and the candidate BTS 968, can be calculated linearly by calculating an overlap area of circular coverage areas. Alternatively, the combined coverage area can be calculated by weighting the coverage areas. The determination of the combined coverage area is described in more detail below. The combined coverage area 960 is determined based on the coverage areas mapped when a BTS is installed and calibrated. The combined coverage area 960 is a probabilistic calculation of the coverage areas of the known BTS 966 and the candidate BTS 968. As discussed above, the two-dimensional position error, referred to as the HEPE value, provides a measurement of the statistical uncertainty in the measurement of the combined coverage area 960. In the 700 system, a distance SC is based on the coverage of the HEPE value and represents an un-sigma uncertainty in the relative phase. The distance between the center 964 of the combined coverage area 960 to the candidate BTS 968 is indicated by di. The phase measurements pk and pc are taken by the MS 102 and provided to the BTS using the telecommunication standard IS-801. As noted above, the system 700 can calculate the expected relative phase difference and compare the expected phase difference with the actual distance measurements. The system 700 can apply the normal distribution equation (4) to calculate the probability that the candidate BTS is consistent with the phase and distance measurements. If multiple candidate BTS (with the same PN) are detected by the system 700, it may be possible to eliminate one or more candidate BTS based on the relative phase difference. That is, the candidate BTS must have a phase difference that is reasonable given the location of the known BTS from the center 964 of the combined coverage area 960 to the distance from the candidate BTS of the center of the combined coverage area. Candidate BTSs that are inconsistent can be eliminated as candidates if they were the source of the signals received by MS 102. The relative phase model also applies to other candidate BTSs. For example, Figure 8 illustrates three candidates who have identical PN 25 compensation. The procedure of the analysis described above applies to each of the candidate BTSs (for example, the BTSs that transmit PN 25 located in the center of the circles 850, 852, 854 in Figure 8) with a calculated probability for each candidate BTS . As noted above, a candidate BTS can be eliminated based only on the overlap model of the coverage area if the overlap of the coverage of another BTS is at least 10 times more likely than the overlap of the coverage area of the BTS that is going to be eliminated. Similarly, a particular candidate BTS can be eliminated based only on the relative phase model if the probability of the phase difference of another BTS is at least 10 times more likely than the probability of the phase difference of the BTS that is going to be eliminated. This procedure guarantees the elimination of a candidate BTS with low probabilities while maintaining a low probability of eliminating the wrong BTS. The probabilities of the overlap model of the coverage area and the relative phase model can be combined to eliminate the candidate BTS. In one example, the probability of the overlap model of the coverage area is multiplied by the probability of the relative phase model. The combination of probabilities serves to further eliminate the BTS with few probabilities from the set of candidates, a candidate BTS can be eliminated based on the combined probability model if the combined probability overlap of another BTS is at least 10 times more likely than the probability of overlapping the coverage area of the BTS that is going to be eliminated. In addition to the analysis described above, system 700 can also use signal strength and cell sector coverage models to uniquely identify candidate BTSs. As discussed above, a typical BTS has multiple transmitters and multiple antenna elements, each of which is intended for operation in a sector. In a typical mode, a BTS can have three sectors, each of which can be considered as a separate BTS. The coverage area of a typical sector may have a coverage area in the form of a cake. The system 700 can calculate scale factors based on the power of the received signal. A measurement of the received signal power is Ec / Io, which is a measurement of the pilot energy accumulated over a chip period of 1 PN (ie, Ec) at the total power spectral density (ie, it) in the received bandwidth. Those skilled in the art will recognize that other power measurements can also be used with the system 700. The system 700 assigns a scale factor based on the power or weakness of the received signal. If the power of the received signal is relatively weak, then the MS 102 can be found within a relatively broad area with respect to the BTS. In this case, the circular coverage area can be expanded by a scale factor to pro a larger circular coverage area. In contrast, the system 700 can re the coverage area if the power of the received signal is strong because the MS is more likely to be close to the BTS. In one embodiment of the described method and apparatus, the system 700 can apply a scale factor of 0.9 for a strong signal (ie, a signal above a threshold) and can apply a scale factor of 1.1 for weak signals ( below the threshold). In a simple calculation, the coverage area of a single known BTS can be identified as a known area for the overlapping model of the coverage area. Similarly, a single known BTS can be used in combination with a single candidate BTS to generate the combined coverage area employed in the relative phase model. However, the system 700 may also allow calculations of the known area or the combined coverage area that may be the result of mixing multiple cell coverage areas. The cells may be combined in a linear fashion or may include weighting. Those skilled in the art will recognize that the computer readable medium, which tangibly incorporates the steps of the method of any of the embodiments described herein, can be used in accordance with the present teachings. Such means may include, without limitation, RAM, ROM, EPROM, EEPROM, floppy disk, hard disk, CD-ROM, etc. The description also includes the steps of the method of any of the above embodiments synthesized as digital logic in an integrated circuit, such as a Programmable Field Gate Array, or Programmable Logic Array, or other integrated circuits that can be manufactured or modified to Incorporate instructions for computer programs. MS 102, in accordance with the present teachings, may include, without limitation: cordless telephone, a personal digital assistant with wireless communication capabilities, a portable computer having wireless communication capabilities, and any other mobile digital device for personal communication to through wireless connection. A number of modalities of the method and apparatus analyzed have been described. However, it will be understood that various modifications to the described method and apparatus can be made. For example, the methods can be executed in software or hardware, or a combination of hardware and software modalities. As another example, it should be understood that the functions described as part of a module can, in general, be executed in an equivalent manner in another module. As another example, the steps or acts shown or described in a particular sequence can generally be executed in a different order. In still another example, the aforementioned method and apparatus are described with reference to the PN compensation example. However, those skilled in the art of communication will understand that the disclosed method and apparatus may use other forms of ambiguous transmitter that identifies information. Accordingly, it will be understood that the invention is not limited by the specific illustrated embodiments of the disclosed method and apparatus, but only by the scope of the appended claims.

Claims (8)

NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following is claimed as a priority: CLAIMS

1. - A method for identifying the location of a signal transmitter received by a mobile station, which includes: a) receiving a signal having ambiguous identification data; b) review a neighboring list for data that matches the ambiguous identification data provided in the received signal; c) determining if the received signal is above a threshold; and d) if it is above a threshold, then determine the location of the transmitter from the location data associated with the matching data in the neighboring list.

2. - The method according to claim 1, characterized in that: a) if the received signal is not above the threshold, then verify that the transmitter associated with the matching data has probably transmitted the received signal; and b) if the transmitter associated with the matching data is likely to have transmitted the received signal, then determine the location of the transmitter from the data in the neighboring list associated with the matching data.

3. - The method according to claim 2, characterized in that: a) if i) no data in the neighbor list matches or ii) no transmitter associated with the matching data is likely to be the transmitter of the received signal, then review an audible list of all transmitters from which signals have previously been received; b) if the ambiguous data received matches the data associated with at least one transmitter in the audible list, then determine among the transmitters in the audible list associated with the data matching the transmitter that is most likely to be the source of the received signal; and c) determine the location associated with the transmitter that is most likely in the audible list from the data in the audible list.

4. - A method to identify the location of a transmitter of signals received by a mobile station, which includes: a) reviewing the neighboring list to determine if the location of the transmitter could be provided by a candidate transmitter in the neighboring list and if so is, then verify that the candidate is a likely candidate; b) if no neighbor transmitter is likely to be the transmitter of the received signal, then verify an audible list of all transmitters from which signals have previously been received; c) if at least one transmitter in the audible list is a candidate to be the source of the received signal, then determine how likely it is that the candidate is the source of the received signal; and d) if the candidate transmitter is a likely candidate, then assume that the transmitter is the source of the received signal and thus determine the location of the transmitter from a database that includes the candidate transmitter.

5. A method for identifying the location of a base station transceiver (BTS), which includes: a) receiving a signal from a primary service BTS in a mobile station (MS); b) receive in the MS an additional signal from a second BTS, the additional received signal has ambiguous data regarding the identity of the second BTS, the ambiguous data are potentially similar to the data transmitted from at least a third BTS but not necessarily received by the MS; c) review a neighboring list that has less than the total of the BTS that may have transmitted the received signal to determine if the ambiguous data matches the data in the neighboring list associated with at least one BTS, the location of at least one BTS can be obtained from the data in the neighboring list; d) if the ambiguous data coincide with the data associated with at least one BTS in the neighboring list, then verify which BTS associated with the matching data is the one that is more likely to have transmitted the received signal; and e) if none of the ambiguous data matches the data associated with any of the BTS in the neighboring list, or none of the BTS associated with the data that matched is likely to have transmitted the received signal, then review an audible list containing all BTSs from which the MS previously received signals in communication with the primary service BTS; f) if the data associated with at least one BTS in the audible list matches the ambiguous data of the received signal, then determine, from those BTS associated with the matching data, the BTS that is most likely to have transmitted the received signal; g) determine the location of the transmitter that is most likely to have transmitted the ambiguous data from the data contained in the audible list.

6. The method according to claim 5, characterized in that the data in the audible list is at the location of the transmitter most likely to have transmitted the ambiguous data.

7. The method according to claim 5, characterized in that the data in the audible list is a link with a memory that stores the location of the transmitter most likely to have transmitted the ambiguous data.

8. A method for identifying the location of a base station transceiver (BTS) that includes: a) receiving a signal from a primary service BTS in a mobile station (MS); b) receiving in the MS an additional signal coming from a second BTS, the additional received signal has first data regarding the identity of the second BTS; c) review a neighboring list that has less than the total of the BTS that could have transmitted the received signal to determine if the first data matches the second data in the neighboring list; d) if the first data matches the second data associated with a BTS in the neighboring list, then determine the location of the BTS in the neighboring list from third party data in the neighboring list; e) if the first data does not match the second data associated with any of the BTS in the neighboring list, then review an audible list that contains all the BTS from which the MS previously received signals in communication with the primary service BTS; f) if the fourth data associated with a BTS in the audible list matches the first data of the received signal, then determine, from the BTS associated with the fourth matching data, the location of the transmitter from the fifth data in the Audible list associated with the matching data quarters. 9.- A method for determining the location of a base station transceiver (BTS) that includes: a) receiving BTS data from a Mobile Station (MS) that includes: i) a unique identifier associated with a service BTS primary; ii) PN data associated with BTS that do not provide service from which the MS received signals; and iii) an indication of the signal strength of the signals received by the MS from the BTS that do not provide service; b) search for a match between the received unique identifier and the key BTS data entries within a database; c) once the match is made, examine the data received from the BTS to determine if the power of a signal reported by the MS for a BTS signal that does not provide service is greater than a threshold associated with the identified primary service BTS by the unique identifier in the database; d) if the signal strength of one of the signals transmitted by a BTS that does not provide service for which the MS received associated PN data is greater than the threshold, then determine the location of the BTS that does not provide service by comparing the PN data associated with the received signal, whose power was below the threshold, with PN data from a neighboring list associated with the matching BTS key data entry; e) if the signal is not greater than the threshold, then determine the probability that a BTS that does not provide service and that is indicated by the PN data in an entry in the neighboring list was the source of the signal received by the MS from a BTS that does not service a signal strength that is below the threshold; and f) if it is determined that it is likely that the BTS that does not provide service and that is indicated by the PN data is the source of the signal received by the MS at a signal strength below the threshold, then determine the location of the BTS that does not provide service from the data in the neighboring list. 10. A method to build a database used to determine the location of a Base Station Transceiver (BTS), which includes: a) receiving BTS data from a Mobile Station (MS) that includes: i) a unique identifier associated with a primary service BTS; ii) PN data associated with signals received by the MS; and iii) an indication of the signal strength of the signals received by the MS from the BTS that do not provide service; b) search for a match between the received unique identifier and the key BTS data entries within a database; c) once the match is made, examine the data received from the BTS to determine if the power of at least one signal received by the MS from a BTS that does not provide service is greater than a threshold associated with the primary service BTS identified by the unique identifier in the database; d) if the power of at least one signal is greater than the threshold, determine whether a neighboring list has been created within the database; and e) if a neighboring list is not created yet, then create a neighboring list in the database and add an entry for the PN data associated with each signal having a signal strength greater than the threshold. 11. A method for determining the location of a base station transceiver (BTS) that includes: a) receiving from a mobile station (MS) data including: i) at least one Global Identifier; ii) at least one pseudo-random noise (PN) compensation of signals received by the MS; iii) the signal strength of at least one of the signals that the received PN compensation has; b) order a PN compensation in a Candidate List if the signal strength received by the MS and having the PN compensation is above a predetermined threshold; and c) determine if each of the PN offsets in the Candidate List is in a neighboring list, the neighboring list includes a location associated with each PN offset, and determine the location associated with each PN offset found in the neighboring list, the location associated is the location of the source of the signal that has that PN compensation. 12. - The method according to claim 11, further comprising: a) ordering a PN offset in an Unknown List if the signal strength having that PN offset is not above a predetermined threshold; b) determine if each of the PN offsets in the Unknown List is in a neighboring list, the neighboring list includes a location associated with each PN offset; c) check whether each PN compensation in the Unknown List has been unambiguously associated with a PN offset in the neighboring list; and d) if at least one PN compensation has been unequivocally associated, then determine the location associated with the unambiguously associated PN compensation that was found in the neighboring list, the associated location is the location of the signal source having that PN compensation . 13. - A position determination entity (PDE), which includes: a) a memory; and b) a central processing unit (CPU) for executing program instructions from the memory for i) receiving ambiguous identification data regarding the source of a signal received by a mobile station (MS); ii) receive data regarding the power of the signal received by the MS; iii) review a neighboring list to find the data that matches the ambiguous identification data; iv) determining if the power of the received signal is above a threshold; and v) if the power of the received signal is above the threshold and a match is found in the neighboring list, then determine the location of the signal transmitter from the location data associated with the matching data in the neighboring list. 14. - The PDE in accordance with the claim 13, characterized in that the CPU also executes instructions to: a) verify that the transmitter associated with the matching data has probabilities of having transmitted the received signal if the received signal is not above the threshold; and b) if the transmitter associated with the matching data has a probability of having transmitted the received signal, then determine the location of the transmitter from the data in the neighbor list associated with the matching data. 15. - The PDE in accordance with the claim 14, characterized in that the CPU also executes instructions to: a) review an audible list of all transmitters from which signals have previously been received if: i) no data in the neighboring list matches; or ii) no transmitter associated with the matching data is likely to be the transmitter of the received signal; b) determining from among the transmitters in the audible list associated with the matching data, the transmitter that is most likely to be the source of the received signal if the ambiguous data received matches the data associated with at least one transmitter in the audible list; and c) determine the location associated with the transmitter that is most likely on the audible list from the data in the audible list. 16. A mobile station (MS) that includes: a) a memory; and b) a central processing unit (CPU) for executing program instructions from the memory to i) receive ambiguous identification data regarding the source of a signal received by the MS; ii) receiving data regarding the strength of the signal received by the MS; iii) review a neighboring list to find the data that matches the ambiguous identification data; iv) determining if the power of the received signal is above a threshold; and v) if the power of the received signal is above the threshold and a match is found in the neighboring list, then determine the location of the signal transmitter from the location data associated with the matching data in the neighboring list. 17.- A position determination entity (PDE), which includes: a) a memory, and b) a central processing unit (CPU) coupled to the memory and with the ability to execute program instructions stored in the memory for: i) review a neighboring list to determine if the location of a transmitter could be provided by a candidate transmitter on the neighboring list and if so, then verify that the candidate is a likely candidate; and ii) reviewing an audible list of all transmitters from which signals have previously been received in the event that no neighboring transmitter is likely to be the transmitter of the received signal; iii) determining how likely it is that that candidate is the source of the received signal if at least one transmitter in the audible list is a candidate to be the source of the received signal; and iv) assume that the candidate transmitter is the source of the received signal and thus determine the location of the candidate transmitter from a database that includes the candidate transmitter if the candidate transmitter is a likely candidate.