HK1086706A - Event-triggered data collection - Google Patents

Description

Event-triggered data collection

RELATED APPLICATIONS

This application claims priority from U.S. provisional application No.60/444246 filed on 30/1/2003 and U.S. provisional application No.60/463910 filed on 17/4/2003.

Technical Field

The present invention relates to the field of wireless communications, and more particularly to collecting data useful for network applications.

Background

Current means for collecting data useful for network applications are labor intensive, especially requiring the use of specialized equipment and operators. For example, in FIG. 1, a special drive test procedure involving a vehicle 118 equipped with a dedicated receiving and monitoring device is enabled to collect data. In the particular example shown, the purpose of collecting data is to optimize the placement of the repeater 110 and to expand the coverage area provided by the combination of the (donor) base station 108 and the repeater 110. The network technician drives the vehicle 118 along the path 120, measuring the strength of the pilot signal emitted by the base station 108 and relayed by the repeater 110 at measurement locations 128a, 128b, 128c, and 128d along the path 120. The location of the measurement site is either known a priori or obtained by a dedicated GPS location determining device within the vehicle 118. This measurement is then used to optimize the placement of the repeater 110.

This method of data collection is problematic because the route 120 traveled by the network technician is typically specific and therefore cannot be guaranteed to approximate the usage pattern of the subscriber stations in the area.

Another problem is that the equipment and operators used to perform the driving test are often dedicated, which increases the cost of data collection.

A third problem is that the data collected by this process is only collected from discrete measurement site samples, so it is often not accurate enough for use in network applications, and therefore only provides a rough approximation of the coverage area of the network or network components. For example, in fig. 1, the pilot signal strength measurements taken at discrete measurement locations 128a, 128b, 128c, and 128d provide only an approximation of the extended coverage area corresponding to the base station 108/repeater 110 combination. And, this data represents only a single instantaneous instance of the system running.

Disclosure of Invention

A method for obtaining data useful for one or more network applications is described. The method is triggered by the occurrence of an event. The method includes obtaining a position estimate for a subscriber station. A record is then formed that associates the position estimate with either or both of the identifier of the triggering event and the data measured or obtained in response to the triggering event. The record is then stored or transmitted. In one embodiment, the method is performed in whole or in part by each of one or more subscriber stations. In another embodiment, the method is performed in whole or in part by each of one or more other network entities, such as base stations or position determination entities. In a third embodiment, the method is performed by each of a combination of one or more subscriber stations and one or more other network entities. In one arrangement, after a triggering event occurs, a position fix of the subscriber station is initiated, and a record is formed based on a position estimate derived from the position fix. Alternatively, the record is formed from previously obtained estimates of the position of the subscriber station if it is deemed to be still accurate. In one implementation, the record is stored locally. Alternatively, the record may be transmitted to a remote location. In one example implementation, the record is transmitted to a remote location and stored in a database that maintains records formed from similar data associated with other subscriber stations serviced by the network. The data in the database may then be used for network planning, optimization, validation, or operational purposes.

A memory embodying the above method is described, as well as a system operating in accordance with the above method. Other systems, methods, features and advantages of the invention will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims.

Drawings

The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the drawings, like reference numerals designate corresponding parts throughout the different views.

FIG. 1 is a schematic diagram depicting one example of a driving test process for collecting data useful for network planning or optimization;

FIG. 2 is a flow diagram of an embodiment of a method in accordance with the present invention for obtaining data in response to the occurrence of an event;

FIG. 3 shows an example of the format of a database record formed from data obtained according to the method of FIG. 2;

FIG. 4 illustrates an example of a hybrid position determination system overlaid on a wireless communication system;

FIG. 5A illustrates one example of a handover failure scenario;

FIG. 5B illustrates an example of a map for identifying handover failure areas;

FIG. 5C is a flow chart of an embodiment of a method performed during network operation when a subscriber station enters or is located in a handover failure zone;

FIG. 6 is a graph depicting the effect of reducing one or more handoff-related thresholds available to a subscriber station when the subscriber station enters a handoff failure zone;

FIG. 7 illustrates an example of a scenario in which the method of FIG. 2 is performed when a selected subscriber station enters, leaves, or crosses a coverage gap;

FIG. 8 illustrates an example of a map for identifying coverage gaps;

FIG. 9A illustrates an example of a scenario in which the method of FIG. 2 is performed in response to a user event;

fig. 9B illustrates a format of a pilot signal strength measurement message (PSMM) in an IS-95 compatible system;

FIG. 9C illustrates an example of a gradient map used to describe the coverage area of one base station in a wireless communication system;

FIG. 10 is a block diagram of an embodiment of a system for performing the method of FIG. 2;

fig. 11 is a block diagram of a subscriber station in a wireless communication system implementing or integrating the system of fig. 2.

Detailed Description

Some terms, such as "about," "substantially," "approximately," and "approximately," are used herein to provide some redundancy in mathematical accuracy to tolerances acceptable in the industry. Thus, any deviation, upward or downward, of a modified value in the range of 1% to 2% or less using the terms "about", "substantially", "approximately" or "near" should be considered to fall clearly within the specified range.

The term "software" as used herein includes source code, assembly language code, binary code, firmware, macro-instructions, etc., or any combination of two or more of the foregoing.

The term "memory" refers to any processor-readable medium, including, but not limited to: RAM, ROM, EPROM, PROM, EEPROM, disk, floppy disk, hard disk, CD-ROM, DVD, etc., or any combination of two or more of the foregoing, on which a series of software instructions executable by the processor may be stored.

The term "processor" or "CPU" refers to any device capable of executing a series of instructions, including, but not limited to: general or special purpose microprocessors, finite state machines, controllers, computers, Digital Signal Processors (DSPs), etc.

The term "logic" refers to an implementation in hardware, software, or any combination of software and hardware.

The term "base station" (BTS) includes omni base stations, sectored base stations, and individual sectors within a sectored base station.

The term "GPS satellite" includes air vehicles (SVs).

The words "wireless communication system," "system," or "network" refer to any system that provides communication services to subscriber stations over a diffused medium, including, but not limited to: cellular, non-cellular, fixed radio, AMPS, PCS, CDMA, TDMA, GSM, IS-95 compatible, CDMA-2000, and WCDMA compatible systems. These terms also include, but are not limited to: a wireless communication system incorporating, integrating, or covered by a position determination system.

The term "position determination system" includes position determination systems that are overlaid on, integrated within, or incorporated with wireless systems.

The term "record" refers to any association of two or more data items. In one application, the term "record" is any association of two or more data items that are processed as a unit.

FIG. 2 illustrates a flow diagram of an embodiment of a method of obtaining data useful to one or more network applications. In this embodiment, the method is triggered by the occurrence of an event 200. In one implementation, the method is performed in whole or in part by each of one or more subscriber stations. In another implementation, the method is performed in whole or in part by each of one or more other entities within the wireless communication system, such as a base station or a position determination entity. In a third implementation, the method is performed in whole or in part by each of a combination of one or more subscriber stations and one or more other network entities. The method includes step 202 for obtaining a position estimate for a subscriber station. In one implementation, the steps include: in response to the event, a position fix for the subscriber station is initiated, and a position estimate for the subscriber station is obtained. In another implementation, the steps include: if the previous position fix was valid or was obtained close enough to the time of occurrence of the triggering event 200 so that the position estimate is still considered accurate, the position estimate for the subscriber station resulting from the previous position fix is obtained. The positioning, if performed, may be initiated by the subscriber station or may be initiated by another network entity using a time measurement provided to it by the subscriber station. Some methods that may be used to perform position location of a subscriber station are discussed next. The position fix yields a position estimate for the subscriber station.

The method also includes an optional step 204 of performing or obtaining one or more data measurements in response to the occurrence of an event. In one embodiment, one or more data measurements are performed or obtained by the subscriber station. In another embodiment, one or more data measurements are performed or obtained by another entity in the wireless communication system, such as a base station or a position determination entity. While this step occurs after step 202 in fig. 2, it should be understood that this step may occur in parallel with step 202.

The method also includes a step 206 of forming a record by associating the position estimate obtained in step 202 with either or both of the identifier of the triggering event 200 and the one or more data measurements resulting from optional step 204.

Step 208 follows step 206. In step 208, the record is stored or transmitted. In one embodiment, the record is formed and stored locally at the subscriber station. In another embodiment, the record is formed at the subscriber station and then transmitted to a remote location. In one implementation, the record is formed at the subscriber station and then transmitted to another network entity where the record is stored in a database for maintaining records that include similar data associated with other subscriber stations. In another implementation, the record is formed in a network entity and then stored in a database.

The format of an example of such a record is shown in fig. 3. In this particular example, the record includes: a field 300, which is an identifier of the triggering event; an optional field 302, which is one or more data measurements captured or collected in response to a triggering event; field 304, is a position estimate for the subscriber station obtained in response to the occurrence of the triggering event.

The method of fig. 2 may be performed by or for each of a plurality of network entities operating within a wireless communication and/or position determination system. In one implementation, the method is performed by or for each of all or substantially all of the subscriber stations operating in the system. In another implementation, the method is performed for authorized or selected subscriber stations associated with subscribers that have been given special consideration in the form of rebates, discounts, etc. to use their subscriber stations during data collection. Records of all of these subscriber stations may be collected and stored in a central database. Because each record associates an estimate of the subscriber station's position at approximately the time of the trigger event with either or both of the event identifier and one or more data measurements obtained in response to the trigger event, the data derived from these records is well suited for network planning, optimization, validation, or operational applications. This method is less expensive than the conventional method for collecting data involving a driving test or the like because it is performed by existing equipment in the network without using dedicated equipment. The method is also more accurate because the collected data is not specific, but reflects the actual usage pattern of subscriber stations in the area, and is not limited to discrete sample points.

In one embodiment, the method of FIG. 2 is triggered by a network event. In this embodiment, there may be a variety of network events, including those initially observed by the subscriber station, and those initially observed by another entity in the network. Examples of possible triggering network events include: a real or near call interruption state; a subscriber station entering a coverage area of a particular network or network entity; a subscriber station leaving the coverage area of a particular network or network entity; periodic timeout of a timer when a subscriber station is outside a coverage area of a network or network entity; true or near handoff state the handoff is a hard handoff or a soft handoff; traversal of a subscriber station between coverage areas of two networks or network entities; traversal of a subscriber station between coverage areas of a donor base station and a relay; detecting an unexpected pilot signal or base station at the subscriber station; alternatively, pilot signals or base stations not present in the subscriber station's neighbor or candidate list are detected at the subscriber station. Other examples are possible, so any of the above should not be construed as limiting.

In another embodiment, the method of fig. 2 is triggered by a user event such as initiating a position fix, or by an event such as a 911 call that would normally result in a position fix being initiated, or by the initiation of a location-related service search in a Web-enabled subscriber station, such as searching for restaurants or other facilities within a certain range of the subscriber station's current location. Other examples of user events are possible, so these specific examples should not be considered limiting.

In a third embodiment, the event is simply the expiration of a timer or other timing element, e.g., the timer counting up or down to a target value or level, or the like.

In one embodiment, the position of a subscriber station operating in a wireless communication system is determined by a position determination system overlaid on the wireless communication system. As shown, a subscriber station 412 receives signals transmitted by a plurality of reference sources 402, 404, 406, and 408 that are visible to a receiver in the subscriber station. As shown, these reference sources may be base stations (BTSs), GPS satellites, or a combination of BTSs and GPS satellites.

Each reference source transmits a signal modulated with an identification code that uniquely identifies the reference source. In one implementation, the identification code is a PN code that may vary in length and periodicity depending on the reference source involved. For IS-95 compatible CDMA systems, the PN code IS a sequence of 32768 chips that repeats every 26.67 milliseconds. In current GPS systems, the PN code is a sequence of 1023 chips that repeats every millisecond.

Subscriber station 412 is equipped with a correlator configured to obtain a time measurement for each signal. In one example, the time measurement is a measurement of time of arrival. Alternatively, a processor within the subscriber station may be used in place of the correlator that obtains the time measurement, and the time measurement may be derived from a correlation function provided to it by the correlator. These correlation functions correlate the composite signal received at the subscriber station with the selected PN code. If a system time reference is available, the subscriber station 412 uses this information to adjust the time measurements so that they coincide with the system time. Alternatively, this task may be performed by a Position Determination Entity (PDE)400 in communication with subscriber station 412.

Subscriber station 412 transmits the time measurements to PDE 400. Upon receiving this information, PDE400 obtains the (known) locations of the reference sources 402, 404, 406, and 408 from one or more almanacs stored in memory 402. It then determines the location of the subscriber station 412 using the time measurements and reference source locations. In one implementation, the position of subscriber station 412 is obtained using known triangulation or trilateration. After determining the position of subscriber station 412, the position of subscriber station 412 may be communicated to subscriber station 412 or other network entity via PDE 400.

Alternatively, subscriber station 412 may determine its own position based on time measurements and the position of reference sources 402, 404, 406, and 408 provided to it by PDE400 or other data sources.

In one implementation, the position estimate obtained in step 202 is obtained in response to initiating an Advanced Forward Link Trilateration (AFLT) position fix, i.e., the position estimate is determined from time measurements derived from forward link transmissions initiated from base stations. In a second implementation, the position estimate is obtained in response to a GPS fix, i.e., the position estimate is determined from transmissions initiated by GPS satellites. In a third implementation, a position estimate is obtained in response to a GPS-assisted position fix. The GPS assisted positioning is performed in two steps. In a first step, the approximate position of the subscriber station is estimated using forward link transmissions from the base station. In a second step, the position estimate of the first step is fine-tuned to a higher level of accuracy based on GPS satellite transmissions.

In one embodiment, the method according to the invention is performed in two stages. The first phase is the data collection phase. The second phase is the network application phase. In a first phase, data is collected by or for each of a plurality of subscriber stations using the method of figure 2 and stored in a central database. In a second phase, one or more network applications are supported using the data.

In one embodiment of the two-phase process, the method of fig. 2 is performed in whole or in part by or for each of one or more authorized subscriber stations in the network during the first data collection phase. In the second network application phase, network operation is supported using data derived from the data collected in the data collection phase. In this embodiment, the triggering events for the data collection phase are: a call dropped condition after which communication service is quickly regained through base stations that are or have not been present in the active list available to the subscriber station at the time of the call drop. As IS known, an active list IS a list of base stations that are visible to the subscriber station and transmit user information for handover in an IS-95 compliant system.

The trigger event represents a situation in which: handoff to a pilot is prevented from occurring because the pilot signal of the target base station is initially too weak to be placed in the subscriber station's candidate list, but it then suddenly becomes so strong that the pilot signal blocks communication with the current base station before the existing base station can join the target base station into the subscriber station's active set. This situation can often occur if the transition of the pilot signal of the target base station occurs faster than the rate at which the subscriber station searches for the pilot signal that is visible to it.

Fig. 5A shows an example of the occurrence of this situation. One user station is contained in a vehicle 500 that turns a corner 512 of a building 510 just along a path 506. Just before the vehicle 500 turns the corner 512, the subscriber station is talking over the base station 504. At this point, the base station 502 is not in the subscriber station's active list because the base station 502 is not visible to the subscriber station at this time. After the vehicle 500 turns the corner 512, the call is dropped because the base station 504 is suddenly no longer visible to the subscriber station. Although base station 502 is now visible to the subscriber station, no handoff to the base station occurs because base station 502 is not on the active list when the call is dropped. The subscriber station then reacquires communication services through the base station 502.

When the triggering event occurs, the subscriber station initiates or has initiated a position fix. If a sufficient number of base stations are not visible to the subscriber station to enable an AFLT-based position fix of sufficient accuracy, then a GPS or GPS-assisted position fix is initiated. The resulting position estimate is then combined with an identifier indicating the failed handoff state and one or more identifiers (e.g., PN codes) identifying the two or any members of the current set just prior to the failed handoff/dropped call state or the two or any members of the current set just after the failed handoff/dropped call state to form a record. In one implementation, an identifier of the target base station 502 is also included, and the communication service is reacquired by the target base station 502. The record is then stored in a central database in which similar records from other subscriber stations in the system are stored. A map, such as the map shown in fig. 5B, is then formed using the database, wherein failed handoff areas 516a, 516B, 516c and 516d are identified within the coverage area 514 of the network. The database may also be used to form association data that associates each of these handover failure regions with either or both members of the active set immediately prior to the handover failure/call drop state and/or members of the active set immediately after the handover failure/call drop state. In one implementation, the association data also associates each failed handover area with a target base station, i.e., a base station through which communication services are reacquired after a handover failure in the data collection phase.

In the second phase of the method, the map and its associated data are typically made available to the subscriber station to support network operations. In one embodiment, each of these subscriber stations performs the method shown in FIG. 5C. In step 518 of the method, a subscriber station performs or has performed a position fix in response to one or more triggering events, including a subscriber event such as a 911 call or a location-related service request. In query step 520 it compares the resulting position estimate with the position of the area on the map where the switch failed, or has already been compared. If the subscriber station is located at or near one of the failed handoff areas identified on the map, step 522 is performed. In step 522, the target base station associated with the handover failure region is forced into the candidate list of the subscriber station and/or the handover sensitivity of the system is increased. This enables the network to initiate a handoff to that base station, thereby avoiding a dropped call situation.

Alternatively, the method of fig. 5C may be performed by another entity within the network, such as a base station serving the subscriber station when the subscriber station enters a handover failure zone, or a PDE. In this embodiment, the network entity forces the target base station to be listed in the subscriber station's active list when the subscriber station encounters a handover failure region. In this way, the network entity effectively forces initiation of a handover to the target base station.

In a second embodiment of the two-phase method, in the first data collection phase, as in the previous embodiment, a handover failure area is identified. However, in the second network application phase, when a subscriber station is detected to enter or operate within the failed handoff region, rather than forcing a base station into the candidate or active list of the subscriber station, one or more thresholds used by the subscriber station (or the base station serving the subscriber station) to support handoff are modified in a manner that hopefully enables or has initiated a handoff condition in a timely manner to avoid a dropped call condition.

In one embodiment, when a subscriber station enters a handover failure region, the T _ ADD threshold available to the subscriber station is lowered. It IS known that in IS-95 compliant systems, the T ADD threshold IS an absolute threshold used to determine whether to ADD a base station in the subscriber station's neighbor list to the subscriber station's candidate list. In this implementation, when a subscriber station enters a handover failure region, the T _ ADD threshold available to the subscriber station is lowered. Then, assuming that the target base station associated with the failed handoff region already exists in the subscriber station's neighbor list, the pilot signal associated with the target base station enters the subscriber station's candidate list more quickly by lowering the T _ ADD threshold sufficiently, thereby enabling the network to initiate a handoff to that base station more quickly and hopefully before call drop situations occur in succession.

Alternatively, in addition to lowering the T _ ADD threshold, the target base station may also be forced into the subscriber station's neighbor list when the subscriber station enters a handover failure region. In this way, the network can initiate a handoff to that base station even if that base station is not in the subscriber station's neighbor list.

In another variation, in addition to lowering the T _ ADD threshold and/or forcing the target base station into the subscriber station's neighbor list, active list, or candidate list, the T _ COMP threshold available to the subscriber station may also be lowered when the subscriber station roams into a failed handoff region. As IS known, in IS-95 compliant systems, the tcomp threshold IS a relative threshold that determines when to move a base station from the subscriber station's neighbor list to the candidate list. By lowering the tcomp threshold, the target base station moves more quickly into the candidate list available to the subscriber station, thereby enabling the network to initiate a handoff to that base station more quickly and hopefully before a call drop condition occurs in succession.

In yet another variation, in addition to lowering the T _ ADD and/or T _ COMP thresholds and/or forcing the target base station into the subscriber station's neighbor list or candidate list, the network may also force only the target base station into the subscriber station's active list when the subscriber station enters a handover failure region. As IS known, in IS-95 systems, the active list IS the list of base stations through which the subscriber station communicates simultaneously. The presence of multiple base stations in the active list indicates that the subscriber station is in a soft handoff state. The network initiates a soft handoff condition with the target base station by forcing the target base station into the subscriber station's active list.

In a third variation, the search time for searching pilot signals in the subscriber station's neighbor and/or candidate list is shortened in order to detect earlier whether one or more of these pilot signals should be reclassified. In one implementation, the search time is shortened by changing a filter time constant that controls the time required to search for pilot signals in the subscriber station's neighbor and candidate lists. By shortening the search time, pilot signals that have exceeded the available T _ ADD and T _ COMP thresholds are enabled to be moved more quickly into the subscriber station's candidate list. In this way, the network can also initiate a soft handoff condition more quickly when the subscriber station enters a handoff failure zone. In one example, the search time is shortened from a maximum of 40ms to a maximum of 10 ms.

The operation of one example of this implementation is further explained with reference to fig. 6. Suppose that a subscriber station has pilot signal P when it roams into a failed handoff region₀The base station(s) in communication. Thus, the pilot signal P₀In the active list of the subscriber station. When the subscriber station roams into a failed handoff region, it begins to detect the target pilot signal P₁. After entering the failed handoff region, the subscriber station lowers its available T _ ADD and T _ COMP thresholds, from T _ ADD to T _ ADD ', and from T _ COMP to T _ COMP', respectively.

At time t₀Pilot signal P₁Exceeds T ADD'. The subscriber station then transmits a pilot signal P₀The associated serving base station transmits a pilot signal strength measurement message (PSMM) reporting the pilot P₁And instructs the serving base station to transmit a pilot signal P₁Is added to the candidate list for the subscriber station. Time t₁Is to make the pilot signal P in the case where the T _ ADD threshold remains valid₁Candidate list for joining subscriber stationTime (2) of (d).

At time t₂Pilot signal P₁Is stronger than the pilot signal P₀The amount of intensity of (a) is T _ COMP' × 0.5 dB. In this specific example, it is assumed that the subscriber station moves the target base station from the neighbor list into the candidate list when the strength of the pilot signal of the target base station exceeds the strength of the pilot signal of the serving base station by an amount of T _ COMP' × 0.5 dB. Accordingly, at time t₂The subscriber station sends another PSMM to the serving base station, reporting the pilot signal P₁And instructs the serving base station to add the target base station to the candidate list of subscriber stations. After receiving the second PSMM, the network is assumed to move the target base station into the active list, thereby initiating a soft handoff state with the target base station.

At time t₃Pilot signal P₀Is no longer visible to the subscriber station and is removed from the subscriber station's active (and candidate) list. However, any call made when the subscriber station enters the failed handoff region is not interrupted because the soft handoff to the target base station is at time t₂Previously initiated. Time t₄Is the time when a soft handover to the target base station has been initiated assuming that the threshold T _ COMP remains valid. Since this time is at time t₃Thereafter, therefore, if T _ COMP remains active, a call drop situation will occur. Thus, by lowering the tcomp threshold to tcomp', it can be seen that the pilot signal P is transduced₁The soft handoff is initiated more quickly to avoid a call drop situation.

In a third embodiment of the two-phase method, data is collected and stored at a central location by or for one or more authorized subscriber stations during a first data collection phase. In a second network application phase, the data is used to support one or more network planning or optimization applications.

The data collection phase of this embodiment may be described with reference to fig. 7. Fig. 7 shows a cellular radio communication system comprising cells 700a, 700b, 700c and 700 d. Base stations 702a, 702b, 702c, and 702d each serve a respective cell. The coverage areas of these cells are identified by reference numerals 704a, 704b, 704c and 704d, respectively. The gaps or holes in the joint coverage areas of these base stations are identified by reference numeral 700 e. It is assumed that a position determination system is superimposed on the wireless communication system. The position determining system may be an AFLT, GPS or GPS assisted system.

Authorized subscriber stations operating within the wireless communication system are configured to perform or have performed, in whole or in part, the method of fig. 2 to collect data to support network planning or optimization applications. In fig. 7, it is assumed that one such subscriber station is disposed within vehicle 706. Another such subscriber station is identified by reference numeral 710.

In one implementation of this embodiment, the triggering events for enabling the method of FIG. 2 are: when an authorized subscriber station roams into a gap 700e in the system coverage area. In other implementations, the triggering event is: when an authorized subscriber station leaves the coverage gap. In a third implementation, the triggering event is: as the subscriber station moves within the coverage gap. In a fourth implementation, the triggering event is: any combination of one or more of the above. In one example, roaming of a subscriber station into a coverage gap is detected when there is a dropped or near dropped call condition, or when no pilots are visible to the subscriber station, or both. Likewise, a subscriber station is detected to leave a coverage gap when it regains communication service.

In the example shown in fig. 7, when one of the authorized subscriber stations roams into the coverage gap 700e, it initiates or has initiated a position fix, or if the time to perform a previous position fix is close enough to the potential event that the position estimate is still considered accurate, a position estimate is or has been obtained from the previous position fix. Thus, when vehicle 706 enters coverage gap 700e, at location 708a, a user station in vehicle 706 initiates or has initiated a position fix, or obtains or has obtained a position estimate. Likewise, when the subscriber station 710 roams into the coverage gap 700e, the subscriber station 710 initiates or has initiated a position fix, or obtains or has obtained a position estimate, at location 712 a.

In one embodiment, when performing a position fix, a GPS position fix is first attempted. If not, then attempt GPS assisted location. In this embodiment, AFLT based positioning is attempted as a last resort. In another embodiment, it is checked whether a sufficient number of base stations are visible to the subscriber station to enable AFLT based positioning. If a subscriber station does not have a sufficient number of base stations visible to the subscriber station to achieve an AFLT based position fix when it enters a coverage gap, then the position fix in this embodiment is performed by GPS satellite transmissions, assuming that a GPS or GPS assisted position determination system is available. Other embodiments may be utilized and, therefore, the above should not be taken to be limiting.

Alternatively, or in addition, when a subscriber station leaves a coverage gap, the subscriber station initiates or has initiated a position fix, or obtains or has obtained a position estimate, after reacquiring communication service. If a position fix is initiated, the position fix may be performed using AFLT transmissions, GPS transmissions, or a combination of both. Thus, in fig. 7, when a subscriber station in vehicle 706 leaves the coverage gap 700e, the subscriber station may initiate or have initiated a position fix, or obtain or have obtained a position estimate, at location 708 b. Likewise, when a subscriber station leaves the coverage gap, the subscriber station may initiate or have initiated a position fix, or obtain or have obtained a position estimate, at location 712 b.

The subscriber station may also initiate or have initiated periodic position fixes (via timers, etc.) as it moves through the coverage gap. These position fixes are likely to be achieved by GPS or GPS assisted transmissions because AFLT transmissions are conceptually not readily available to the subscriber station when the subscriber station is in a coverage gap. Thus, in fig. 7, as a subscriber station in vehicle 706 moves within the coverage gap, the subscriber station may initiate or have initiated a position fix at location 708 c. The position fix may be initiated after expiration of a timer that is initiated when the subscriber station enters a coverage gap. The timer may be periodically restarted until the subscriber station regains communication service. Thus, as the subscriber station moves through the coverage gap, it may or may not have initiated a periodic position fix.

For each position estimate obtained, the subscriber station forms or has formed a record associating an identifier of the triggering event, whether entering, leaving, or moving within the coverage gap, with the position estimate for the subscriber station. The record is stored or transmitted to and stored in a database containing similar records associated with authorized subscriber stations. After a period of time, the data in the database may be used to support one or more network planning or optimization applications.

In one such application, a map such as that shown in FIG. 8 is derived from data in a database. The map shows a coverage area 800 of a wireless communication system and coverage gaps 802a, 802b, 802c within the coverage area. The map may be used to support one or more network planning or optimization applications in which the location of existing base stations and/or repeaters are optimized and/or base stations and/or repeaters are added to the system to eliminate or reduce coverage gaps.

In a fourth embodiment of the two-phase method, in the first phase, data collection is performed for or by one or more authorized subscriber stations operating in a wireless communication system covered by a position determination system. After the data is collected, it is stored in a central storage unit. In the second phase, the data is used to support one or more network planning, optimization or verification applications.

The first data collection phase is described with reference to fig. 9A. The figure shows a cellular wireless communication system comprising cells 900a and 900b served by base stations 904a and 904b, respectively. The coverage areas of these cells are denoted by reference numerals 906a and 906b, respectively. It is assumed that the position determination system is overlaid on top of the wireless communication system.

One or more authorized users operating within the system are configured to perform or have performed the method of fig. 2, in whole or in part, wherein the triggering event is the initiation of a position fix, or any user event that typically causes a position fix initiation by a user station. Examples are 911 calls or requests for location-related facilities or services in a Web-enabled subscriber station, e.g. a restaurant located within a certain distance of the subscriber station.

In the example shown in fig. 9A, assume that a user in a vehicle 920 traveling along route 908 initiates or has initiated a position fix or obtained or has obtained a position estimate at locations 910a, 910b, 910 c. After obtaining the position estimate, the subscriber station measures or has measured the strength and/or phase of one or more pilot signals visible to the subscriber station, and makes or has made one or more records that relate the one or more measurements to the position estimate for the subscriber station.

In one implementation, the subscriber station makes or has made an improved PSMM that correlates a conventional PSMM containing strength measurements of one or more pilot signals visible to the subscriber station with a position estimate for the subscriber station. Fig. 9B shows a conventional PSMM in which portion 909 repeats for each of the one or more pilot signals that are reported to be visible to the subscriber station. The meaning of the fields in fig. 9B are well known and need not be described in further detail in this disclosure. This message is augmented in this implementation with a field for the position estimate of the subscriber station.

One or more records are stored or transmitted and stored in a database containing similar records associated with other subscriber stations. After a period of time, when a sufficient number of records have been in the database, the second phase of the process is initiated. In a second phase, one or more gradient maps are derived from the database. Each of these gradient maps represents the gradient of the coverage area of one base station in the network.

Fig. 9C shows an example of a gradient map such as may be derived from data stored in a database. As shown, the map includes a plurality of ordered concentric contours 912a, 912b, 912c, each contour associated with a particular pilot signal strength, and the order of the contours is: the pilot signal strength decreases gradually from the inner contour to the outer contour. Thus, in the example of fig. 9C, contour 912a represents a strong pilot signal strength, contour 912b represents a medium pilot signal strength, and contour 912C represents a weak pilot signal strength at the outer boundary of the base station coverage area. After these gradient maps are derived, they may be used to support one or more network planning, optimization, or verification applications. In one example, they are used to validate RF propagation models that were previously used to plan or optimize the system.

In a fourth embodiment of the two-phase method, in the first data collection phase, the triggering events for data collection are: in idle mode, when an authorized subscriber station loses service. Such out-of-service may occur, for example, when a subscriber station encounters a new pilot signal and the pilot is so strong that the subscriber station cannot decode the paging channel of the current pilot signal or any of its neighbors. When such a triggering event occurs, the position of the subscriber station is determined and associated with the identifier of the event and/or the identifier of the new pilot signal and/or the measured value of the strength of the new pilot signal. This data collection may be performed by or for each of a plurality of authorized subscriber stations. In a second network application phase, a map of those areas of the network where these pilot signals are encountered is generated. In addition, these pilot signals are studied to determine whether they are only weak signal areas or areas where improved pilot signal/neighbor list management is needed.

FIG. 10 illustrates one embodiment of a system for a user to obtain data useful for one or more network applications. As shown, the system includes a processor 1000 and a memory 1002.

The memory 1002 actually implements a series of software instructions for performing the method of fig. 2, or any of the embodiments, implementations, variations, and examples thereof previously described or suggested.

The processor is configured to: the software instructions actually implemented by the memory 1002 are accessed and executed. By executing these instructions, the processor 1000 performs the method of fig. 2.

The system of fig. 10 may be implemented by, or integrated into, one or more authorized subscriber stations or other network entities operating within the position determination system of fig. 4. The records formed by these entities are sent to PDE400 and then stored in database 402. After a period of time, data derived from the data stored in the database may be used to support one or more of the described network planning, optimization, validation or operational applications. In the case where the derived data is used to support network operations applications such as supporting handover, the derived data needs to be provided to all subscriber stations operating in the system.

Fig. 11 illustrates an embodiment of a subscriber station that implements or integrates the system of fig. 10. Other examples may be used and therefore fig. 11 should not be considered limiting.

The radio transceiver 1106 is configured to: baseband information, such as voice or data, is modulated on an RF carrier, and the modulated RF carrier is demodulated to obtain the baseband information.

The antenna 1110 is configured to: the modulated RF carrier is transmitted over a wireless communication link and received over a wireless communication link.

Baseband processor 1108 is configured to: baseband information is provided from CPU 1102 to transceiver 1106 for transmission over a wireless communication link. In turn, CPU 1102 obtains baseband information from an input device within user interface 1116. Baseband processor 1108 is further configured to: baseband information is provided to CPU 1102 from transceiver 1106. CPU 1102, in turn, provides baseband information to output devices within user interface 1116.

The user interface 1116 includes a plurality of devices for inputting or outputting user information such as voice or data. These devices, which are typically included in the user interface, include a keypad, a display screen, a microphone, and a speaker.

The GPS receiver 1112 is configured to: receives and demodulates a composite signal formed from the pilot signals of the GPS satellites visible to the subscriber station and provides the demodulated information to correlator 1118. The composite signal is received through antenna 1114.

The radio transceiver 1106 is configured to: receives and demodulates a composite signal formed from the pilot signals transmitted by the base stations visible to the subscriber station and provides the demodulated information to correlator 1118. The composite signal is received by antenna 1110.

In this particular example, the GPS receiver 1112 and the radio transceiver 1106 share the same filter chain, but it should be understood that an example is possible in which a separate filter chain is provided for each.

For GPS or GPS-assisted positioning, correlator 1118 is configured to: the GPS correlation function is derived from the information provided to it by the GPS receiver 1112. For AFLT or GPS assisted positioning, correlator 1118 is configured to: the base station correlation function is derived from the information provided to it by the radio transceiver 1106.

Correlator 1118 is also configured to: a measure of time of arrival and/or time difference of arrival is derived from the peak of the correlation function it derives. Alternatively, CPU 1102 may derive this information from the correlation function provided to it by correlator 1108.

The subscriber station may use this information to obtain wireless communication services and/or determine its position, or its position may be determined by the PDE or other entity in the position determination system by AFLT-based, GPS-based, or GPS-assisted means.

The channel decoder 1120 is configured to: the channel symbols provided to it by baseband processor 1108 are decoded into elementary source bits. In one example, the channel symbols are convolutionally encoded symbols and the channel decoder is a viterbi decoder. In a second example, the channel symbols are serial or parallel concatenations of convolutional codes, and the channel decoder 1120 is a turbo decoder.

The memory 1104 is configured to: software instructions for implementing the method of fig. 2 or any of the embodiments, implementations, examples, or variations thereof previously described or suggested are stored.

CPU 1102 is configured to: these software instructions are accessed and executed to gather data useful for network planning, optimization, validation, or operation applications.

While various embodiments, implementations and examples have been described above, it will be apparent to those of ordinary skill in the art that many more embodiments, implementations and examples are possible that are within the scope of this invention. Accordingly, the invention is not limited except as by the appended claims.

Claims (58)

1. A method for obtaining data useful for one or more network applications, the method comprising performing the steps of:

obtaining a position estimate for the subscriber station in response to a triggering event;

forming a record associating the position estimate of the subscriber station with either or both of an event identifier and data measured or obtained in response to the event; and

storing or transmitting the record.

2. The method of claim 1, wherein the subscriber station operates within a wireless communication system.

3. The method of claim 1, wherein the event is observed by the subscriber station.

4. The method of claim 2, wherein the event is observed by an entity in the system other than the subscriber station.

5. The method of claim 2, wherein the event is a network event.

6. The method of claim 2, wherein the network event is a real or near call interruption state.

7. The method of claim 2, wherein the network event is the subscriber station entering a coverage area of the system or system entity.

8. The method of claim 2, wherein the network event is the subscriber station leaving a coverage area of the system or system entity.

9. The method of claim 2, wherein the network event is: expiration of a timer when the subscriber station is outside a coverage area of a system or system entity.

10. The method of claim 2, wherein the network event is a handover failure state.

11. The method of claim 2, wherein the network event is a handover or near handover state.

12. The method of claim 11, wherein the handoff state is a hard handoff or a soft handoff state.

13. The method of claim 11, wherein the near handover state is a hard handover or a soft handover state.

14. The method of claim 2, wherein the network event is a change in band status.

15. The method of claim 2, wherein the network event is a traversal of the subscriber station between coverage areas of two wireless communication systems or system entities.

16. The method of claim 2, wherein the network event is a traversal of the subscriber station between coverage areas of a donor base station and a relay.

17. The method of claim 2, wherein the network event is detection of an unexpected pilot signal or an unexpectedly strong pilot signal at the subscriber station.

18. The method of claim 2, wherein the network event is detection of an unexpected base station at the subscriber station.

19. The method of claim 2, wherein the network event is detection of a pilot signal at the subscriber station that is not present in the subscriber station's neighbor list.

20. The method of claim 1, wherein the event is a timer timeout.

21. The method of claim 1, wherein the event is a user event.

22. The method of claim 21, wherein the event is initiation of a 911 call.

23. The method of claim 21, wherein the event is a request for a location-related service in a Web-enabled subscriber station.

24. The method of claim 1, wherein the record correlates the position estimate with one or more measurements of pilot signal strength or phase.

25. The method of claim 24, wherein at least one of the pilot signals is associated with a traffic channel existing between the subscriber station and a base station.

26. The method of claim 25, wherein the traffic channel is a forward traffic channel.

27. The method of claim 25, wherein the communication channel is a reverse traffic channel.

28. The method of claim 1, wherein the position estimate is determined by the subscriber station.

29. The method of claim 2, wherein the position estimate is determined by an entity in the system other than the subscriber station.

30. The method of claim 29, wherein the other entity is a location determination entity.

31. The method of claim 1 wherein said record is stored locally at said subscriber station.

32. The method of claim 2, wherein the record is transmitted and stored at a remote location in the system.

33. The method of claim 32 wherein said records are stored in a database that maintains similar records obtained from other subscriber stations serviced by said system.

34. A memory for storing a series of software instructions implementing the method of claim 1.

35. A system comprising a processor and the memory of claim 34, wherein the processor is configured to: accessing and executing the software instructions stored in the memory.

36. The system of claim 35, implemented by or integrated in a subscriber station.

37. A wireless communication system for obtaining data useful for one or more network applications, the wireless communication system comprising:

one or more network entities, each network entity configured to: (1) obtaining or having obtained a position estimate for a subscriber station in response to a trigger event, (2) forming or having formed a record associating the position estimate for the subscriber station with either or both of an identifier of the trigger event and data measured or obtained in response to the trigger event, and (3) storing or having stored the record in a database.

38. The system of claim 37, wherein the one or more triggering events include a handover failure status.

39. The system of claim 38, further comprising a memory for holding data representing a map of handover failure areas derived from the database and association data for each area associating the area with one or more base stations.

40. The system of claim 39, comprising one or more subscriber stations configured to: accessing data derived from the database and, after detecting roaming into a handover failure zone, using the data, forcing or having forced one or more base stations associated with the handover failure zone into one or more lists available to the subscriber station to support handover.

41. The system of claim 39, further comprising one or more user base stations configured to: accessing data derived from the database and using the data to adjust or have adjusted one or more thresholds available to the subscriber station to support handover after roaming into a handover failure zone is detected.

42. The system of claim 39, further comprising one or more user base stations configured to: accessing data derived from the database and using the data to adjust or have adjusted one or more search times available to the subscriber station to support handover after roaming into a handover failure zone is detected.

43. The system of claim 37, wherein the one or more triggering events comprise: the subscriber station roams into, out of, or within a coverage gap.

44. The system of claim 43, further comprising a memory for holding data derived from the database, the data including a map covering a gap.

45. The system of claim 43, further comprising a memory for holding data derived from the database, the data representing one or more gradient maps.

46. A method for obtaining data useful for one or more network applications, the method comprising the following steps performed by or for each of a plurality of subscriber stations operating within a wireless communication system:

obtaining a position estimate for the subscriber station in response to one or more triggering events;

forming a record associating the position estimate of the subscriber station with either or both of the identifier of the trigger event and the data measured or obtained in response to the trigger event; and

the record is stored or already stored in a database.

47. The method of claim 46, wherein the one or more triggering events include a handover failure state.

48. The method of claim 47, further comprising deriving data from the database, the data comprising a map of handover failure areas and association data associating each area with one or more base stations.

49. The method of claim 48, further comprising: after a subscriber station roams into a handover failure region, forcing or having forced a base station associated with the handover failure region into one or more lists available to the subscriber station to support handover.

50. The method of claim 48, further comprising: the one or more thresholds available to the subscriber station are adjusted or have been adjusted to support the handoff after the subscriber station roams into a handoff failure zone.

51. The method of claim 48, further comprising: after a subscriber station roams into a handover failure region, one or more search times available to the subscriber station are adjusted or have been adjusted to support handover.

52. The method of claim 46, wherein the one or more triggering events include: roaming into, out of, or within coverage gaps.

53. The method of claim 52, further comprising deriving data from the database, the data representing a map covering a gap.

54. The method of claim 52, further comprising deriving data from the database, the data representing one or more gradient maps.

55. The method of claim 53, further comprising using the data for a network planning or optimization application.

56. The method of claim 54, further comprising: the data is used for network planning or optimization applications, or for validating RF propagation models.

57. A method for obtaining data useful for one or more network applications, the method comprising performing the steps of:

a record forming step for forming a record associating, for each of a plurality of subscriber stations, a position estimate of the subscriber station obtained in response to the trigger event with either or both of an identifier of the trigger event and data measured or obtained in response to the event;

a storing step for storing the record in a database; and

an execution step of executing one or more network planning, optimization, validation or operational applications using data derived from the database.

58. The method of claim 33, wherein the database relates to base station almanac information.