CN1778135A - Method and apparatus for performing position determination in a wireless communication network with repeaters. - Google Patents

Abstract

The present invention provides a method and apparatus to perform position determination in a wireless (e.g., cellular) communication network with repeaters. A signal received by a terminal is initially identified as being from a repeater. A position and a position uncertainty for the identified repeater are obtained (e.g., from a repeater database) and provided as the position estimate and position uncertainty for the terminal if (1) a more accurate position estimate for the terminal cannot be obtained, (2) the terminal is deemed to be in an indoor environment, or (3) the terminal is located sufficiently close to the identified repeater. If information for additional delays associated with the identified repeater is available, then the position estimate for the terminal may be derived based on a ''compensated'' time measurement for the identified repeater (i.e., with the additional delays removed) and time measurements for at least two other transmitters received by the terminal.

Description

Method and device for position determination in a wireless communication network with repeaters

Cross References to Related Applications

This application claims priority to US Provisional Application No. 60/452,182, filed March 3, 2003.

technical field

The present invention relates generally to location determination, and more particularly to a method and apparatus for location determination in a repeater wireless communication network, such as a cellular network.

Background technique

A common technique used to determine the location of a terminal is to determine the amount of time required for signals transmitted from transmitters at known locations to reach the terminal. The propagation time of the signal is typically converted to a "pseudorange", which is an estimate of the distance between the terminal and the transmitter. Using a process commonly referred to as "trilateration," the terminal's location can be estimated based on the pseudoranges to the transmitter and the location of the transmitter.

One system that provides signals from multiple transmitters (satellites) at known locations is known as the Global Positioning System (GPS). An accurate three-dimensional position estimate (or "fix") can be obtained for a terminal based on signals received by the terminal from a sufficient number of GPS satellites (typically four). However, in some operating environments (eg indoors) the required number of GPS satellites may not be available to obtain this fix. Another system that provides signals from multiple transmitters (base stations) at locations known to be bounded by the earth is a wireless (eg, cellular) communication network. A two-dimensional (2-D) position estimate can be obtained for a terminal based on signals received by the terminal from a sufficient number of base stations (typically three or more).

Many cellular networks employ repeaters to provide coverage for a given area within the network or to extend the network coverage. For example, a repeater can be used to cover geographic areas not covered by base stations due to fading conditions (ie, "holes" in the network). Repeaters can also be used to cover rural areas (such as along highways) outside the base station's coverage area. Repeaters receive, condition and forward signals on both forward and reverse links. The forward link refers to the communication link from the base stations to the terminals, and the reverse link refers to the communication link from the terminals to the base stations.

Determining the location of a terminal in a network employing repeaters presents various challenges. On the forward link, each repeater transmits a repeater's signal to the terminal within its coverage area with high power and additional delay. Due to the high power of the repeater signal coupled with the isolation typically associated with the repeater's coverage area, a terminal located within the coverage area of a repeater is often unable to receive signals from the base station. Furthermore, in many situations where repeaters are used (eg inside buildings, tunnels, subways, etc.), the signals from the GPS satellites do not have sufficient power levels and cannot be received by the terminal either. In this way, only a limited number of signals (possibly only one from the repeater) can be used to determine the terminal's location.

Furthermore, the additional delay introduced by the repeater can distort the measurements made by the terminal on the signal received from the repeater. Therefore, measurements of signals received by repeaters are often discarded and not used for position determination. In some cases, only very few measurements can be used to compute a position estimate for the terminal. If the signal from the repeater is discarded, the accuracy of the position estimate based on the remaining signal will be very poor.

There is therefore a need in the art for a method and apparatus for providing a position estimate of a terminal in a wireless communication network employing repeaters (or other transmission sources with similar characteristics) and equipment.

Contents of the invention

A method and apparatus for location determination in a repeater wireless communication network (eg, a cellular network) is provided herein. As described below, the method and apparatus utilizes a repeater database containing various types of information about repeaters in the network. A position estimate for a terminal may be obtained based on (1) measurements made by the terminal of signals received by the terminal, (2) information in the repeater database, and (3) other information available.

According to one embodiment of the disclosed method and apparatus, for location determination in the network with repeaters, it is first identified that a signal received by the terminal originates from a repeater. The position of the identified repeater is obtained (eg, from a repeater database) and, if not available, a more precise estimate of the position of the terminal is provided as the terminal's position estimate. It is also possible to obtain (again, from the repeater database) the position uncertainty for the identified repeater and provide an estimate of the uncertainty for the terminal position. For a variety of reasons, for example, (1) lack of additional delay information associated with repeaters and/or (2) lack of a sufficient number of measurements for a terminal to perform trilateration, it may not be possible to obtain the More precise location estimates.

It can also be determined whether the terminal is in an indoor or an outdoor environment. It may further be determined whether the terminal is located sufficiently close to the identified repeater. This can be done by comparing the received signal strength of the identified repeater to a threshold. If the terminal is considered to be (1) in an indoor environment or (2) located close enough to the identified repeater (ie, the received signal strength exceeds a threshold) the location of the identified repeater is provided as the terminal's position estimate.

If additional delay information related to an identified repeater is available, the time measurements reported by the terminal for that repeater may be processed to remove the additional delay. A more accurate position estimate of the terminal can thus be derived based on "compensated" time measurements (ie, with additional delay removed) of the identified repeater and time measurements received by the terminal from at least two further transmitters.

Various aspects and embodiments of the invention are described in more detail below.

Description of drawings

From the following detailed description given in conjunction with the accompanying drawings, the features, nature and advantages of the present invention will become more apparent. In all the accompanying drawings, the same reference numerals represent the same, similar or corresponding features or functions, and wherein:

Figure 1 shows a wireless communication network with repeaters;

Figure 2 shows a procedure for deriving a terminal position estimate based on signals received by the terminal from base stations and/or repeaters in the network;

Figure 3 shows a process for obtaining a position estimate of a terminal that has received a signal from at least one repeater; and

Figure 4 shows a block diagram of base stations, repeaters, terminals and position determination entities (PDEs) in the network.

Detailed ways

The word "exemplary" is used herein to mean "serving as an example, instance, or illustration". Any implementation or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations or designs.

FIG. 1 shows a diagram of a wireless communication network 100 with repeaters. Network 100 may be a cellular network supporting one or more CDMA standards (eg, IS-95, IS-2000, W-CDMA, etc.) and/or supporting one or more TDMA standards (eg, GSM). All these standards are well known in the art. Network 100 may include multiple base stations 104 . However, for simplicity, only three base stations 104a, 104b, and 104c are shown in FIG. 1 . Each base station 104 serves a particular coverage area 102 and provides communications for terminals 106 located within its coverage area. A base station or its coverage area, or both, is often referred to as a "cell", depending on the context in which the term is used.

Repeaters 114 may be deployed in network 100 to provide coverage to areas not otherwise covered by base stations 104 . For example, the repeater 114 may be deployed in an area where the reception of signals from the base station 104 is poor, such as the area 112a in FIG. 1 . Poor reception may be due to fading conditions or some other phenomenon. Repeaters 114 are also typically deployed within buildings to improve coverage indoors. The repeater 114 can also be used to extend the coverage of the network 100, such as the areas 112b and 112c in FIG. 1 . Repeaters are generally more cost-effective than base stations and can be more advantageously deployed where additional coverage is required but no additional capacity is required. Depending on the deployment of the network, any number of base stations in the network can be relayed.

Multiple terminals 106 may be distributed throughout the network. For simplicity, only one terminal 106 is shown in FIG. 1 . Each terminal can communicate with one or more base stations at any time on the forward and reverse links. A terminal may communicate with multiple base stations simultaneously if the network supports "soft handover" and if the terminal is actually in soft handover.

Multiple base stations 104 are typically connected to and controlled by a base station controller (BSC) 120 . BSC 120 coordinates communications for base stations under its control. A Position Determination Entity (PDE) 130 may be connected to the BSC 120 and used for position determination. As described in further detail below, PDE 130 may receive measurements from terminal 106 and may determine the location of the terminal based on the received measurements.

For a CDMA network, each base station is assigned a pseudorandom noise (PN) sequence with a specific offset or start time. The base station uses this PN sequence to spread its data prior to transmission on the forward link. Each base station also transmits a pilot, which is a simple all ones (or all zeros) sequence spread with the PN sequence assigned to that base station. The signal transmitted by each base station thus includes spread spectrum data and pilot.

For position determination, pseudoranges to a given base station can be estimated based on signals received by a terminal from the base stations. The time of arrival of the signal at the terminal can be determined based on the phase of the PN sequence used by the base station for spreading. Since this PN phase information is typically obtained by processing pilots, the measurements obtained by the terminals are often referred to as "pilot phase" measurements (PPM). Pilot phase measurements are used to estimate the amount of time a signal takes to propagate from the base station to the terminal. This propagation time can be converted to a pseudorange, which includes the "true" or actual distance between the terminal and the base station plus measurement error.

In the following description, the term "time measurement" is used to denote (1) a measurement obtained based on a signal received from a transmitter (eg, a base station) and (2) a measurement that can be used to calculate a pseudorange to the transmitter. The time measurement can be a pilot phase measurement, a time of arrival (TOA) measurement, a round trip delay (RTD) measurement or a time difference of arrival (TDOA) measurement. All these different types of measurements are known in the art and will not be described here.

As mentioned above, repeaters can be used to provide coverage to areas not covered by base stations, such as within buildings. Each repeater 114 is connected to a "donor" base station 104 by a wireless or wired link (eg, a coaxial or fiber optic cable), either directly or through another repeater. On the forward link, a repeater receives a "donor" signal from the "donor" base station, conditions the "donor" signal to obtain a "relay donor signal" and directs it via a "serving" antenna to the Terminals within the area transmit the relay donor signal. On the reverse link, the repeater receives an "uplink" signal from the serving antenna, conditions the "uplink" signal to obtain a "relay uplink" signal and sends the relay uplink signal to the donor base station. The uplink signal includes a reverse link signal transmitted by the terminal to the repeater. A repeater typically includes a hardware unit for signal conditioning the donor and uplink signals and a serving antenna for transmitting the relay donor signal to the terminal and receiving the reverse link signal from the terminal. The serving antenna and hardware unit may be located at different locations or co-located at the same location. In any case, the location of the serving antenna is typically used as the location of the repeater.

Each repeater is associated with an additional delay consisting of (1) the transmission delay between the donor base station and the repeater and (2) due to the circuitry within the repeater receiving, conditioning and forwarding The internal delay caused by the signal from the donor base station. For example, surface acoustic wave (SAW) filters, amplifiers, and other components within a repeater introduce time delays to the repeating donor signal transmitted by the repeater. In some cases, this additional delay may be comparable to, or may be greater than, the transmission delay from the donor base station to the terminal. Thus, time measurements of signals received by a terminal from a repeater cannot be reliably used to determine the terminal's position if the additional delay of the repeater is not taken into account.

A method and apparatus for location determination in a repeater wireless communication network, such as a cellular network, are provided. As described below, the method and apparatus utilize a repeater database that includes various types of information for repeaters in the network. A position estimate for a terminal is obtained based on (1) measurements made by the terminal, (2) information in the repeater database, and (3) other information that may be available.

Figure 2 shows a flowchart of an embodiment of a process 200 for deriving a position estimate of a terminal based on signals received by the terminal from base stations and/or repeaters in a cellular network.

Initially, measurements of one or more signals received by the terminal from one or more transmitters in the network are obtained (step 212). Each received signal comes from a different transmitter, which can be a base station or a repeater. One or more measurements may be obtained for each received signal. Each measurement may be a time measurement (eg, a pilot phase measurement), a signal strength measurement, or some other type of measurement. For example, one time measurement and one signal strength measurement may be obtained for each received signal.

For each received signal, it is determined whether the received signal is from a repeater or a base station (step 214). Step 214 is referred to as the repeater identification process, and may be accomplished based on (1) one or more measurements obtained for each received signal and (2) information in the repeater database. As part of the repeater identification process, if a signal is received from a repeater, it can also be determined whether it is an indoor repeater or an outdoor repeater. An indoor repeater is a repeater deployed inside a building, while an outdoor repeater is a repeater deployed outside a building. If the transmitter of a given received signal cannot be identified, the signal can be discarded from being used for position determination. The repeater identification process will be described in detail below.

It is then determined whether a sufficient number (eg, three or more) of measurements for the base station are available (step 218). If the answer is yes, then an estimate of the terminal's location is derived based solely on measurements at the base station (step 220). For step 220, measurements on repeaters are discarded. Techniques for obtaining an estimate of the terminal's location based on measurements of base stations in a cellular network are known as Advanced Forward Link Trilateration (A-FLT), Observed Time Difference of Arrival (OTDOA), Enhanced Observed Time Difference (E- OTD) and Uplink Time of Arrival (U-TOA). These techniques are described in US Patent Application No. XXX, filed XXX, entitled "XXX," which has been assigned to the assignee of the present application and is incorporated herein by reference. In general, location determination can be achieved by well-known means, such as those described in the publicly available 3GPP25.305, TIA/EIA/IS-801 and TIA/EIA/IS-817 standard documents.

If the answer to step 218 is no, then it can be determined whether a signal is from a repeater (step 228). If the answer is yes, then a location estimate for the terminal may be derived based on measurements of the identified repeaters and possibly base stations (step 230). Step 230 will be described in further detail below.

If the answer to step 228 is no, then a sufficient number of measurements for the base station and no measurements for the relay were obtained from the terminal. In this case, cell identification or enhanced cell identification techniques may be used to estimate the location of the terminal based on the measurements received from the base stations. Cell identification techniques provide the identity of a cell within which the terminal is believed to be located, based on available measurements. Enhanced cell identification techniques provide the identity of the sector within which the terminal is believed to be located. Therefore, the accuracy of cell identification and enhanced cell identification techniques depends on the size of the cell and sector, respectively, in which the terminal is considered to be located. Figure 3 shows a flowchart of an embodiment of a process 230x for obtaining a position estimate of a terminal that has received a signal from at least one repeater in the cellular network. Each of the at least one repeater is identified by the repeater identification process in step 214 in FIG. 2 . Process 230x may be used for step 230 in FIG. 2 .

Initially, it is determined whether the repeater database contains "coarse" or "full" information for the at least one identified repeater (step 312). A description of what constitutes rough and complete information is provided below. In summary, the repeater database is considered to contain coarse information for a given repeater if (1) the repeater's position and position uncertainty are available and (2) the repeater The relevant delay information is not available. An identified repeater is selected first if the repeater database contains rough information for the at least one identified repeater. If only one repeater is identified, then the selected repeater is simply the single identified repeater. If multiple repeaters are identified, one of the identified repeaters (eg, the repeater with the strongest signal reception strength) is selected. The location of the selected repeater is then provided as the terminal's location estimate (step 314). Then the process ends.

If the answer to step 312 is no, then it is determined whether the terminal is in an indoor or outdoor environment (step 322). This determination may be made based on signals received from the repeater and/or other available information. For example, a terminal is considered to be indoors if a signal is received from at least one indoor repeater. The repeater identification process in step 214 in FIG. 2 may indicate whether an identified repeater is an indoor repeater or an outdoor repeater. The determination of the indoor/outdoor environment of the terminal will be further described in detail below.

If the terminal is considered to be indoors, then the location of the selected repeater is provided as the terminal's location estimate (step 324). In an indoor environment, the position of the repeater is typically sufficient as an estimate of the terminal's position. Furthermore, in an indoor environment, a more accurate estimate of the terminal's location may not be available because the required number of signals from base stations and/or GPS satellites for trilateration may not be available.

If the terminal is not in an indoor environment, then it is determined whether the received signal strength or power from any of the identified repeaters exceeds a specified signal strength threshold (step 332). If the answer is yes, then the terminal is considered to be located close enough to this repeater. In this case, the location of the identified repeater with strong received signal strength is provided as the terminal's location estimate (step 334). Selection of this signal strength threshold may be based on a variety of factors, as described in further detail below.

For steps 314, 324 and 334, the uncertainty of the terminal location estimate may be set equal to the location uncertainty of an identified repeater whose location has been used as the terminal's location estimate. For example, for a repeater covering a large building and connected to a donor base station via a leaky cable, a large location uncertainty may be associated with the repeater. In this case, a considerable uncertainty can be used for the terminal position estimate, which has been set as the repeater's position.

If the answer to step 332 is no, then this indicates that (1) the terminal is not in an indoor environment, (2) has not received a sufficiently strong signal from any of the identified repeaters and (3) the repeater The repeater database includes delay information for at least one identified repeater. In this case, the terminal's position estimate may be based on (1) time measurements of signals received from the base station and (2) "compensated" time measurements of signals received from the repeater (block 340). Time measurements of signals received from a repeater (i.e., reported by the terminal) include (1) the transmission delay from the donor base station to the repeater, (2) the repeater's internal delay and (3) Propagation delay from the repeater to the terminal. A compensated time measurement for the repeater may be obtained by processing the time measurement for the repeater to remove additional delays associated with the repeater (step 342). The backoff time measurement for a given repeater i can be expressed as:

${\tilde{p}}_i=p_i-{\mathrm{\τ}}_{\mathrm{int},i}-{\mathrm{\τ}}_{\mathrm{br},i}$ Equation (1)

where: p _i is the time measurement for repeater i reported by the terminal;

τ _{int, i} is the internal delay of repeater i;

τ _br,i is the transmission delay from the donor base station to relay i; and

为中继器i的补偿时间测量。

is the compensation time measurement for repeater i.

The additional delay for repeater i is the combination of the internal delay τ _int,i and the transmission delay τ _br,i . For each repeater whose additional delay is known (ie available in the repeater database), its backoff time measurement can be obtained.

Backoff time measurements for a repeater can be used to derive pseudoranges to that repeater. Accordingly, time measurements for a base station can be used to derive pseudoranges to that base station. The terminal location estimate can then be derived based on (1) the pseudoranges to the base station and the location of the base station and (2) the pseudoranges to the relay and the location of the relay (step 344). Step 344 can be implemented by using the A-FLT method. Then the process ends.

Figures 2 and 3 represent specific embodiments for location determination in a cellular network with repeaters. Various modifications to the disclosed embodiments may be made and are within the scope of the invention. For example, the steps of the process shown in Figure 3 may be rearranged. As an example, block 340 may be moved between steps 312 and 322 . In this case, trilateration may be used to obtain a position estimate for the terminal, if available (ie if time measurements and back-off time measurements for a sufficient number of base stations and repeaters respectively are available). Typically, using trilateration to obtain the terminal position estimate requires pseudoranges to three or more transmitters, where each transmitter may be a base station or a repeater. If the pseudoranges of a sufficient number of transmitters are not available, then the position of an identified repeater can be used as the terminal's position estimate. As another example, steps 322 and 324 and/or steps 332 and 334 may be eliminated.

Some of the steps in Figures 2 and 3 will be described in further detail below.

repeater identification

Various methods can be used to determine whether a signal received by a terminal is from a base station or a repeater. These methods include a legacy network method, a modulation method and an identifier PN method.

For traditional network methods, the transmitter of each signal received by the terminal is identified, one signal at a time, based on measurements taken of the signal and information available on base stations and repeaters in the network. The method is iterative, with each iteration identifying a transmitter that receives the signal. Two implementations of this traditional network approach - an overlay approach and a relative phase approach - are described below.

The coverage overlap method identifies the transmitter of each received signal based on an identified coverage area (described below) for the terminal and the coverage areas of a series of candidate transmitters for the identified signal. First, the signal from a reference base station or repeater is identified from all received signals. This can be done, for example, based on the PN offset/sequence of the received signal, the time of arrival of the received signal, the power level of the received signal, some other measure, or a combination thereof. For each iteration, one of the remaining received signals is selected for identification. For the first iteration, the identified coverage area is set as the coverage area of the reference base station or repeater. For each subsequent iteration, the identified coverage area is formed as a composite of the coverage areas of all base stations and repeaters identified in previous iterations. The PN sequence of the signal identified in the current iteration is then determined. Next a list of base stations and repeaters assigned this same PN sequence is obtained. The coverage area of each base station and repeater in the list is then determined. The coverage area of a repeater may be obtained based on the repeater's position uncertainty or maximum antenna range stored in the repeater database, and the repeater position. Each base station and repeater on the list is then evaluated. The base station or repeater having a coverage area that most overlaps with the identified coverage area is then selected as the transmitter of the signal being identified in the current iteration.

The relative phase method identifies the transmitter for each received signal based on the terminal's identified coverage area and time measurements of a series of candidate transmitters. Similar to the overlay overlapping method, in each iteration one of the received signals is selected for identification. For each iteration, as described above, the identified coverage area is obtained, the PN sequence of the signal identified in the current iteration is determined, and the list of base stations and repeaters assigned this PN sequence is obtained.

A time delta measure (Δp _i ) and a distance delta (Δd _i ) are then calculated for each candidate base station and repeater in the list. The time increment measure for a given candidate transmitter i is the difference between the time measure of the identified signal (p _i ) and the time measure of a selected transmitter (p _s ) (i.e. Δp _i =p _i − _ps ). The selected transmitter can be any of the base stations and repeaters identified in previous iterations. The distance increment for a candidate transmitter i is the difference between (1) the distance (d _i ) from the candidate transmitter i to the center of the identified coverage area and (2) the distance from the selected transmitter to the center of the identified coverage area distance (d _s ) (ie Δd _i =d _i -d _s ). The distance d _i is determined based on the position of the candidate transmitter i that can be obtained from the repeater database. Evaluate every base station and repeater on the list. The base station or repeater whose delta time measurement is closest to the delta distance (ie the smallest (Δp _i -Δd _i )) is then selected as the transmitter of the signal identified in the current iteration. Time measurements can be converted to distance by multiplying by the light velocity constant C, as is known in the art.

If delay information is available for a given candidate repeater, then the additional delay for this repeater is subtracted from the time measure reported by the terminal to obtain the time measure _pi for that repeater. Conversely, if such delay information is not available for the candidate repeater, the additional delay for the repeater may be estimated based on the round trip delay (RTD) measured at the terminal's candidate base station. This RTD measurement is approximately twice the sum of: (1) the distance from the donor base station to the repeater (d _br ) and (2) the distance from the repeater to the terminal (d _rt ) (i.e. RTD/2≈d _br +d _rt ). For distance d _rt , it is estimated that the terminal is located at the center of the identified coverage area. The distance _dbr is then subtracted from the time measurement reported by the terminal to obtain the time measurement _pi of the repeater.

For the modulation method, the relay uplink signal sent by the relay to the donor base station on the reverse link is modified by the relay to include an identifying signature. The signature may be in the form of an identifiable change in amplitude, frequency and/or delay of the uplink signal received at the repeater's serving antenna. For the delay modulation method, the relay uplink signal sent by the relay to the donor base station may include the uplink signal and one or more delayed versions of the uplink signal. Each delayed version can be generated by delaying the upstream signal by a specific amount of time. The terminal's signature can be obtained in various ways. For example, the signature may be obtained based on (1) a specific set of delays for the delayed versions of the uplink signal, (2) a specific frequency for switching between different delayed versions of the uplink signal, or ( 3) A specific pattern or code sequence for switching between delayed versions of the uplink signal.

For frequency modulation methods, this signature can be obtained by slightly perturbing the carrier frequency of the relay signal in some specific way. For amplitude modulation methods, this signature can be obtained by perturbing the amplitude of the relay signal.

The relay uplink signal from the relay may be received and processed by the donor base station to detect the signature included in the relay uplink signal by the relay. The signature can be evaluated to determine the identity of the particular repeater that transmitted the relay uplink signal. All reverse link signals included in this repeater uplink signal are associated with the identified repeater.

For the identifier PN method, a repeater generates an identifier signal by spreading a pilot with the PN sequence assigned to the repeater. This PN sequence may be one of several PN sequences reserved especially for repeater identification. The identifier signal may be summed with a donor signal received on the forward link from the donor base station. The identifier signal is set at a low enough power level (eg -15dBc) that it does not cause too much interference to the donor signal. Additionally, the identifier signal can be delayed appropriately to allow the terminal to detect that the identifier signal is from a particular repeater. A relay donor signal including a donor signal and an identifier signal is transmitted by the relay to the terminal.

The relay donor signal from the repeater is received and processed by a terminal to detect the identifier signal. The detected identifier signal is then evaluated to determine the identity of the particular repeater that transmitted the relay donor signal.

repeater database

The completeness and accuracy of the repeater database has a huge impact on the accuracy of the terminal's position estimation in a cellular network with repeaters. A complete and accurate repeater database is preferred. However, it may be difficult or impossible to organize such a database. Depending on the type of information available for repeaters in the network, the repeater database can be classified as "coarse" or "full".

A rough repeater database could contain all or some of the parameters listed in Table 1.

Table 1 parameter describe Repeater ID A unique ID assigned to the repeater. Corresponding PN PN offset/sequence assigned to the repeater's donor base station. Position and Position Uncertainty The position of the repeater and the uncertainty of this position. The repeater's location can be provided by latitude, longitude and altitude coordinates. indoor/outdoor indicator Indicates whether the repeater is an indoor or outdoor repeater.

The repeater ID can be any code used to identify the repeater. For example, the repeater ID may correspond to the signature in the relay uplink signal sent by the repeater to the donor base station (for the modulation method), the PN sequence used to generate the identifier signal (for the identifier PN method), etc. wait.

For a coarse repeater database, repeater locations can be coarse and can further be related to a large location uncertainty. Thus, the coarse repeater database can be used for applications that only require a coarse terminal location estimate.

A complete repeater database can contain all or some of the parameters listed in Table 2.

Table 2 parameter describe Repeater ID A unique ID assigned to the repeater. Corresponding PN PN offset/sequence assigned to the repeater's donor base station. Position and Position Uncertainty The position of the repeater and the uncertainty of its position. A more precise version of the same parameters in the coarse repeater database. Maximum Antenna Range (MAR) The range within which a terminal is likely to receive a signal from a repeater, measured from the repeater's serving antenna. indoor/outdoor indicator Indicates whether the repeater is an indoor or outdoor repeater.

The repeater parameters in Table 2 are similar to the base station parameters in the Base Station Almanac (BSA). As mentioned above, MAR can be used to identify repeaters in a conventional network approach. For the full repeater database, repeater locations are more precise and have less location uncertainty than for the coarse repeater database. In steps 324 and 334 in FIG. 3, a more accurate position and a smaller position uncertainty of the repeater may be provided as a terminal position estimate.

For repeater identification and location determination methods that are affected by repeater additional delays, the complete repeater database may also contain the parameters listed in Table 3.

table 3 parameter describe Repeater internal delay The delay caused by the repeater due to the internal circuitry in the repeater. base station to repeater delay Due to the delay in the transmission of the donor signal from the donor base station to the relay. This transmission may be over the air, via coaxial or fiber optic cable, or by some other means.

The delay inside the repeater and the delay from the base station to the repeater constitute the additional delay of the repeater. This delay information may be used in step 342 in Figure 3 to obtain a compensated time measurement for the repeater by removing the additional delay from the time measurement reported by the terminal.

The complete repeater database may also contain the parameters listed in Table 4 for repeater identification and location determination methods that are affected by the signal strength or power emitted by the repeater.

Table 4 parameter describe Repeater Service Antenna Information The repeater serves various types of information about the antenna, such as gain, orientation, horizontal beamwidth (antenna opening), vertical beamwidth, downtilt, etc. Path loss from donor base station to repeater Path loss from donor base station to repeater. For a repeater communicating with the donor base station via a wireless link, it can also be derived based on the information of the donor antenna used to transmit signals to the donor base station. Donor signal power Donor signal power at the antenna of the donor base station.

The parameters listed in Table 4 can be used to determine the power of the relay donor signal transmitted by the relay to the terminal.

Different repeater identification methods may rely on different information (such as delay or power information) to identify repeaters. In addition, different location determination methods may also rely on different information to obtain the location estimate of the terminal.

The repeater database can be such that (1) only coarse information is available for each repeater in the network or (2) complete information is available for each repeater. The repeater database can also be "hybrid" so that coarse information is available for some repeaters and full information for others. For a mixed repeater database, a coarse/full field may be provided for each repeater to indicate whether coarse or full information is available for that repeater. The terminal's location estimate may be derived based on coarse or complete information received by the terminal and available at each relay.

The repeater database can be stored as a separate database or as part of the base station almanac. A base station almanac typically includes various types of information about base stations in the network.

Indoor/Outdoor Repeater Determination

For the location determination process shown in FIG. 3 , it is distinguished whether the terminal is in an indoor environment or an outdoor environment. This is because in Figure 3 a different process is used to derive the terminal location estimate depending on whether it is considered to be indoors or outdoors.

The environment of the terminal can be determined in various ways. In one embodiment, an indoor/outdoor field is included for each repeater in the repeater database. This field is used to indicate whether the repeater is an indoor repeater or an outdoor repeater. For each repeater in the database, this field can be filled with indoor/outdoor information for that repeater if such information is known, otherwise the field can be left blank. This indoor/outdoor information for a given repeater can be obtained at the time of repeater deployment or at the time of inspection of repeaters in the network. A terminal is considered to be indoors if it receives a signal from an indoor repeater. Otherwise, it can be considered that the terminal is located outdoors.

In another embodiment, the determination of whether the terminal is indoors or outdoors is made based on the number of signals received by the terminal. For example, since signals from GPS satellites are typically not received indoors, or are received at very low power levels, a terminal is considered to be indoors if no or very little signal is received from GPS satellites. If (1) the received signal strength of the GPS satellite is low and/or (2) the viewing angle of the GPS satellite is low, the terminal is also considered to be indoors. Similarly, the terminal may be considered to be indoors based on the number of signals received from the base station and/or the received signal strength of the base station.

Signal Strength Threshold

For the location determination process shown in FIG. 3, if the terminal is outdoors but close enough to a repeater, the repeater's location can be used as the terminal's location estimate (steps 332 and 334). The determination of whether the terminal is sufficiently close to the repeater may be made by comparing the repeater received signal strength with a signal strength threshold. This threshold can be set in various ways.

In one embodiment, the threshold for a given repeater is set at the signal strength expected to be received by a terminal within a particular range from the repeater. For example, the threshold may be set based on the requirements set forth in the enhanced 911 (E-911) report and rules adopted by the Federal Communications Commission (FCC). The FCC order requires that, for cell phone-based technologies, the terminal's location accuracy be within 50 meters for 67% of calls and within 150 meters for 95% of calls. The threshold may thus be set at the signal strength expected to be received by a terminal at 50 or 150 meters from the repeater, depending on the expected uncertainty in the reported terminal position estimate. The threshold could also be set at the worst case (ie weakest) power predicted at 50 or 150 meters from the repeater. The signal strength threshold is typically chosen to be higher than the addition threshold conventionally used to add a new base station to a candidate set of terminals. The candidate set includes all base stations whose signals are received by the terminal with sufficient strength and which can be selected to transmit data to the terminal. Some exemplary values that may be used for the signal strength threshold are -6dB, -10dB, and -13dB. Other values may be used for this threshold and are within the scope of the invention.

The same threshold is used for all repeaters in the network. Alternatively, different thresholds may be used for different repeaters. In this case, the threshold for each repeater may be set based on the power level of the relay donor signal at the repeater serving antenna. This output power level may be determined based on serving antenna and path loss information stored in the repeater database (eg, as shown in Table 4). For each repeater, a threshold field may also be included in the repeater database. This field can be used to store the signal strength threshold of the repeater.

network entity

4 shows a block diagram of an embodiment of base station 104x, repeater 114x, terminal 106x, and PDE 130 in network 100. Base station 104x is an exemplary base station in the network, repeater 114x is an exemplary repeater, and terminal 106x is an exemplary terminal. Terminal 106x may be a cellular telephone, cell phone, computer with wireless modem or some other unit. Base station 104x is operatively connected to PDE 130 via BSC 120, which is not shown in FIG. 4 for simplicity.

On the forward link, base station 104x transmits pilot, data, and signaling to the terminals within its coverage area. These various types of data are processed (eg, encoded, modulated, filtered, amplified and frequency upconverted) by a modulator/transmitter (Mod/TMTR) 420 to provide a forward link signal. Forward link signals are sent through duplexer 422 , processed by splitter unit 424 and transmitted via antenna 426 to terminals within the coverage area of base station 104x.

Repeater 114x receives forward link signals from splitter unit 424 in donor base station 104x. In the repeater 114x, the forward link signal is sent through the duplexer 430, conditioned by the conditioning unit 432, sent through the duplexer 434 and transmitted to terminals within the coverage area of the repeater 114x via the antenna 436. Antenna 436 is the repeater's serving antenna.

Terminal 106x receives forward link signals at antenna 452 from zero or more base stations (eg, base station 104x) and zero or more repeaters (eg, repeater 114x). Such a receiver input signal from antenna 542 may include multiple forward link signals received from multiple transmitters, each of which may be a base station or a repeater. The receiver input signal is routed through a duplexer 454 and processed by a receiver/demodulator (RCVR/Demod) 456 to provide various types of information that can be used for repeater/base station identification and location determination. In particular, the RCVR/Demod 456 can provide time measurements and signal strength measurements for each forward link signal detected in the receiver input signal. The RCVR/Demod 456 can be implemented as a rake receiver that can concurrently process multiple signal instances (or multipath components) from multiple base stations and repeaters. A rake receiver includes multiple demodulation processors (or fingers), each of which can be assigned to process and track a specific multipath component.

On the reverse link, terminal 106x may transmit data, pilot, and/or signaling to a reference base station (eg, base station 104x). For example, terminal 106x may send back time and signal strength measurements made on forward link signals received by the terminal. The various types of data are processed by modulator/transmitter (Mod/TMTR) 464 to provide a reverse link signal, which is then sent through duplexer 454 and from antenna 452 .

Repeater 114x may receive the reverse link signal at antenna 436 from terminal 106x. The receiver input signal from antenna 436 is sent through duplexer 436, conditioned by conditioning unit 438, sent through duplexer 430 and sent to donor base station 104x.

Base station 104x may also receive reverse link signals at antenna 426 from terminal 106x. The receiver input signal from antenna 426 is passed through splitter unit 424 , routed through duplexer 422 and provided to receiver/demodulator (RCVR/Demod) 428 . RCVR/Demod 428 then processes the receiver input signal in a complementary manner to provide various types of information, which in turn may be provided to processor 410. For example, RCVR/Demod 428 may recover the time and signal strength measurements sent by terminal 106x. RCVR/Demod 428 may also provide time and signal strength measurements made on reverse link signals received from terminal 106x.

For the embodiment shown in FIG. 4 , communication (Comm) port 414 within base station 104x is operatively connected (e.g., via BSC 120) to communication port 476 within PDE 130. Communication ports 414 and 476 allow base station 104x to exchange information with PDE 130 regarding repeater/base station identification and location determination. Some of this information may be measurements received from terminal 106x.

As noted above, repeater and base station identification and determination of terminal location may be performed by terminal 106x, base station 104x, PDE 130, or some other network entity in general. Entities performing repeater/base station identification and/or location determination provide relevant information. Such information may include, for example, a series of forward link signals received by terminal 106x, timing and signal strength measurements of those forward link signals, related information from a repeater database, and the like.

The process of repeater and base station identification and obtaining a position estimate for the terminal 106x on forward link signals received by terminal 106x may be performed by processor 460 in terminal 106x, processor 410 in base station 104x, or in PDE 130 The processor 470 is implemented. Storage units 462, 412, and 472 may be used to store various types of information for repeater/base station and location determination. This information may include, for example, a list of forward link signals received by terminal 106x, timing and signal strength measurements of those signals, pertinent information from repeater databases and base station almanacs, and the like. Memory units 412, 462, and 472 may also store program codes and data for processors 410, 460, and 470, respectively. The repeater database in the PDE 130 can be used to store the information of the repeaters in the network, such as the parameter information listed in the above Tables 1-4. The base station almanac may be stored in database 474 or memory 472 .

The methods and devices described herein can be implemented in various ways such as hardware, software or a combination thereof. For hardware implementations, the methods and apparatus may be implemented on one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs) designed to perform the functions described herein. (PLD), Field Programmable Gate Array (FPGA), processor, controller, microcontroller, microprocessor, other electronic unit, or a combination thereof.

For software implementation, the methods described herein can be implemented with modules (eg, procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in a memory unit (eg, memory unit 412, 462 or 472 in FIG. 4) and executed by a processor (eg, processor 410, 460 or 470). The memory unit can be implemented within the processor or external to the processor, in which case it can be communicatively coupled to the processor by means as is known in the art.

The above description of the disclosed embodiments is provided to enable any person of ordinary skill in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments without departing from the spirit and scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (25)

1. A method for determining position in a wireless communication network with repeaters, comprising: identifying a signal received by a wireless terminal as coming from a repeater; obtaining a location of the repeater; and If a more accurate position estimate for the terminal is not available, the repeater's position is provided as a position estimate for the terminal. 2. The method of claim 1, further comprising: If a more accurate position estimate of the terminal is not available, providing a position uncertainty of the repeater as an uncertainty of the terminal's position estimate. 3. The method of claim 1, wherein a more precise position estimate of the terminal cannot be obtained due to lack of additional delay information associated with the relay. 4. The method of claim 1, wherein a more accurate position estimate of the terminal cannot be obtained due to lack of a required number of measurements to trilaterate the terminal. 5. The method of claim 1, further comprising: determining whether the terminal is in an indoor or an outdoor environment; and If the terminal is considered to be in an indoor environment, the location of the repeater is provided as an estimate of the terminal's location. 6. The method according to claim 5, wherein if the repeater is an indoor repeater, the terminal is considered to be in an indoor environment. 7. The method of claim 5, wherein the determining is based on the number of signals received by the terminal from satellites and base stations. 8. The method of claim 1, further comprising: comparing the received signal strength of the repeater to a threshold; and If the received signal strength exceeds the threshold, the location of the repeater is provided as a location estimate for the terminal. 9. The method of claim 8, wherein the threshold is set based on an expected repeater signal reception strength at a particular range from the repeater. 10. The method of claim 1, wherein additional latency information associated with the repeater is available, the method further comprising: processing time measurements for the repeater to remove additional delays associated with the repeater; and A more accurate position estimate of the terminal is obtained based on the time measurements of the repeater from which additional time delays have been removed and the time measurements of at least two further transmitters received by the terminal. 11. The method of claim 1, wherein the identifying is based on a pseudorandom number (PN) sequence for signals received from the repeater. 12. The method of claim 1, wherein the identifying is based on modulation characteristics of signals received from the repeater. 13. The method of claim 1, wherein the identification is based on time measurements obtained at the terminal of signals received from the repeater. 14. The method of claim 1, wherein the identifying is based on signal strength measurements obtained at the terminal of signals received from the repeater. 15. The method of claim 1, wherein said wireless communication network is a CDMA network. 16. An apparatus in a wireless communication network with repeaters, comprising: means for identifying a signal received by a wireless terminal as coming from a repeater; means for obtaining a position of said repeater; and means for providing the position of said repeater as the terminal's position estimate if a more accurate position estimate for the terminal is not available. 17. The apparatus of claim 16, further comprising: means for determining whether said terminal is in an indoor or an outdoor environment; and means for providing the position of said repeater as an estimate of the terminal's position if the terminal is considered to be in an indoor environment. 18. The apparatus of claim 16, further comprising: means for comparing the received signal strength of the repeater with a threshold; and means for providing the location of the repeater as an estimate of the terminal's location if the received signal strength exceeds the threshold. 19. The apparatus of claim 16, further comprising: means for processing time measurements of said repeater to remove additional delays associated with the repeater; and Means for obtaining a more accurate position estimate of the terminal based on the time measurements of the repeater from which additional time delays have been removed and the time measurements of at least two further transmitters received by the terminal. 20. A program embodied on a tangible storage medium, the program including executable instructions to: identifying a signal received by a wireless terminal as coming from a repeater; obtaining a location of the repeater; and If a more precise position estimate for the terminal is not available, the position of the repeater is provided as a position estimate for the terminal. 21. An apparatus in a wireless communication network with repeaters, comprising: a storage unit capable of storing a database of information on the repeaters in the network; and a processor capable of identifying that a signal received by a wireless terminal is from a repeater, obtaining from said database a position of said repeater, and providing said terminal if a more accurate estimate of the position of the terminal is not available. The position of the repeater is used as the position estimate of the terminal. 22. The apparatus of claim 21, wherein the database includes a location and a location uncertainty for each of at least one repeater in the network. 23. The apparatus of claim 22, wherein the processor is further operable to obtain a position uncertainty of the repeater and, if a more accurate position estimate for the terminal is not available, provide the position uncertainty as the The uncertainty of the terminal's position estimate. 24. A method for position determination in a CDMA communication network with repeaters, comprising: identifying the transmitter of each of the at least one signal received by a wireless terminal as a repeater or a base station; and If a signal is from an identified repeater, and if a more accurate estimate of the terminal's location is not available or if the terminal is believed to be in an indoor environment, providing the location of the identified repeater as the location of the terminal estimate. 25. The method of claim 24, further comprising: If the received signal strength of the identified repeater exceeds a threshold, the location of the identified repeater is provided as the terminal's position estimate.

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