WO2001026252A1

WO2001026252A1 - Mobile unit location apparatus and method for a cdma wireless system

Info

Publication number: WO2001026252A1
Application number: PCT/US2000/024260
Authority: WO
Inventors: Alan P. Rottinghaus; Jeff L. Pfeil
Original assignee: Motorola Inc.
Priority date: 1999-09-30
Filing date: 2000-09-01
Publication date: 2001-04-12

Abstract

A mobile unit location method and apparatus for radiotelephone transceiver generates a mobile location CDMA carrier buffer control signal (120) and a programmable location engine control signal (122). The method and apparatus selectively stores, in response to the mobile location CDMA carrier buffer control signal (120), CDMA carrier data for use in determining mobile location data. A programmable single site location engine (108) provides mobile location data (118) based on the programmable location engine control signal (122) and based on the stored selected CDMA carrier data.

Description

MOBILE UNIT LOCATION APPARATUS AND METHOD FOR A CDMA WIRELESS

SYSTEM

Cross Reference to Related Co-pending Applications

This application is a related application to a co-pending application entitled "Method and Apparatus for Locating a Remote Unit Within a Communication System" having inventors Pfeil et al., attorney docket number CE08027R, filed on even date, owned by instant assignee and hereby incorporated in its entirety by reference.

This application is a related application to a co-pending application entitled "Method and Apparatus for Determining Remote Unit Location Using Phased Array Antenna Elements, having inventors Pfeil et al.. attorney docket number CE03698R, filed on even date, owned by instant assignee and hereby incorporated in its entirety by reference.

Field Of The Invention

The invention relates generally to mobile unit location methods and apparatus and more particularly to mobile unit location apparatus and methods for multi-carrier CDMA communication systems.

Background Of The Invention

Many wireless communication systems, such as cellular TDMA radiotelephone systems employ some type of mobile unit location apparatus and techniques. Multilateration mobile unit location techniques are well known which employ a plurality of base station receivers to triangulate or otherwise determine the location of a mobile unit based on a plurality of different sites. Other wireless communications systems, such as those employing code division multiple access (CDMA) channelization may use a plurality of CDMA carriers (e.g., codes) over a plurality of different frequencies. A problem can arise with mobile location techniques of CDMA type systems since mobile units typically control their output power as a function of their proximity to a transmitting antenna. For example, as a mobile unit gets closer to a base site antenna, it may lower its output power to allow other mobile units to use the same CDMA carrier. This can provide less interference for other mobile units using the same CDMA carrier. However, as the mobile unit decreases power, the path loss can increase and multilateration location can become more difficult since other antennas at other sites may not be able to detect the mobile carrier of the low output power. Accordingly, there is a desire for single site mobile unit location techniques.

Such a single site mobile location system or a multi-site location system may not exist on many cellular base stations. Consequently, the addition of location finding equipment may be required as add ons to cellular base stations. However, a problem can arise since the addition of single site mobile unit location systems can require additional hardware and/or antennas such as additional CDMA receivers, local oscillators and other front end receiving equipment. This is partly due to the need to provide a mobile unit location apparatus that is compatible with different manufacturers of cellular base stations. However, the duplication of equipment can greatly increase the cost of the overall system.

Consequently, there exists a need to reduce the amount of hardware associated with providing mobile unit location capability for a CDMA wireless system. -

Brief Description Of The Drawings

FIG. 1 is block diagram illustrating one example of a mobile unit location apparatus in accordance with one embodiment of the invention.

FIG. 2 is flow chart illustrating one example of the operation of the apparatus shown in FIG. 1.

FIG. 3 is a block diagram of another embodiment of a mobile unit location apparatus in accordance with the invention.

Detailed Description Of The Preferred Embodiment

Briefly, a mobile unit location method and apparatus for a radiotelephone transceiver generates a mobile location CDMA carrier buffer control signal and a programmable location engine control signal. The method and apparatus selectively stores, in response to the mobile location CDMA carrier buffer control signal, CDMA carrier data for use in determining mobile unit location data. A programmable single site location engine provides mobile location data based on the programmable location engine control signal and based on the stored selected CDMA carrier data.

In one embodiment, a shared location resource controller outputs the mobile location CDMA carrier buffer control signal and the programmable location engine control signal. A mobile location CDMA carrier buffer, such as a plurality of buffers dedicated to each CDMA carrier, stores the CDMA carrier data for use in determining mobile unit location data, in response to the mobile location CDMA carrier buffer control signal. The programmable mobile location engine provides mobile location data in response to the programmable location engine control signal and makes a plurality of passes, on a per mobile unit basis, of baseband data stored in the mobile location CDMA buffer for a given CDMA carrier. The mobile unit location apparatus shares resources with, for example, a CDMA carrier radio telephone transceiver. The shared resources may include, for example, antenna elements such as phased array or sectorized antennas, and analog front end processing circuits, such as analog digital converters, digital down converters and base band data buffers. If desired, a separate programmable single site location engine may be used for each CDMA carrier.

FIG. 1 illustrates a mobile unit location apparatus 100 that may be included, for example, as part of a radiotelephone transceiver that receives CDMA encoded information through antenna elements 102a and 102b. The antenna elements 102a and 102b may be phased array antennas or non-phased array antennas. One type of non-phased array antenna may be of the type described in U.S. Patent No. 5,786,791. The mobile unit location apparatus 100 may be included, for example, in a base site transceiver station (BTS), or any other suitable transceiver. The mobile unit location apparatus 100 includes a shared location resource controller 104, a mobile location CDMA carrier buffer 106, a programmable mobile location engine 108, a programmable CDMA carrier selector 110 and a receive analog front end stage 112. For purposes of illustration, and not limitation, the invention will be described with reference to a cellular radiotelephone network. However, it will be recognized that the disclosed apparatus and methods may be employed in any suitable wireless system desiring mobile unit location capabilities. Accordingly, the mobile unit location apparatus 100 may be in communication with a location server, such as a location services node 114 that contains a location server database 116 that may store mobile location data 118 provided by the mobile unit location apparatus 100. The location server database 116 may be accessible, for example, by other system operations that may wish to use the mobile location information.

The shared location resource controller 104 is operative to output a mobile location CDMA carrier buffer control signal 120, a programmable location engine control signal 122 and a CDMA carrier select control signal 124. The mobile location CDMA carrier buffer 106 may be a single buffer, or a plurality of buffers wherein each of the plurality of buffers is dedicated to a single CDMA carrier. The mobile location CDMA carrier buffer 106 is responsive to the mobile location CDMA carrier buffer control signal 120 to facilitate selective flushing and storage of CDMA carrier data as required by the programmable mobile location engine 108. The programmable mobile location engine 108 in this example, is a single site programmable mobile location engine. The mobile location CDMA carrier buffer 106 stores CDMA carrier data 126 for use in determining mobile location data 118.

The shared location resource controller 104 may operate, for example, on a simple round robin service location request, or other suitable technique. Data buffering and the time allocated to processing each carrier may be approximately equal. However, it will be recognized that different implementations go out for variable allocation of processing resources and prioritization of mobile location requests. Variable allocation of processing could be a function, for example, of loading on a given carrier. Prioritization may be assigned on a per mobile basis depending upon the type of information being transmitted, (e.g., video, voice, data, priority of data, or other information).

The programmable mobile location engine 108 is operative to provide mobile location data 118 in response to the programmable location engine control signal 122. The programmable mobile location engine 108 generates the mobile location data 118 based on the stored selected CDMA carrier data 126 that is stored in the mobile location CDMA carrier buffer 106.

The programmable CDMA carrier selector 110 may include an analog to digital converter 130 operative to convert multicarrier CDMA information 132 obtained by the analog front end stage 112. The programmable CDMA carrier selector 110 may be implemented, for example, as a programmable down converter that can be shared with, or as part of, the programmable down converter for a base site transceiver station to programmably convert, or split, CDMA carriers as known in the art. The programmable CDMA carrier selector 110 outputs digital baseband data as the selected CDMA carrier data 126.

The analog front end stage 112 includes conventional amplifiers, filters, and down converters, as known in the art, and provides intermediate frequency output. The analog front end stage may be a shared resource with a CDMA base station transceiver.

The shared location resource controller 104 may be, for example, any suitably programmed processing device or devices that may be shared within a base site transceiver station or other suitable apparatus. The shared location resource controller 104 controls the sharing of the resources among the mobile unit location apparatus and the traffic channel transceiving functions. The shared location resource controller 104 controls the sharing of resources at a single location. For example, it may control usage among antenna elements such as phased array antennas or sectorized antennas, receive analog front end stages, receive analog to digital converters, buffers and location engines.

In addition, the shared location resource controller 104 also buffers (e.g., queues) mobile unit location requests received from the location services node 114 and aggregates the mobile unit location requests. For example, the shared location resource controller 104 organizes the mobile unit location requests so that all mobile units with a given carrier in a given sector (where the radiotelephone system is a sectorized system) are grouped together and prioritized. The shared location resource controller 104 also chooses a next carrier and sector to be analyzed for mobile unit location once one location operation has been completed for a given sector. The shared location resource controller 104 also initializes the programmable single site location engine (or engines) 108 and controls the flushing and resetting of the mobile location CDMA carrier buffer 106 (or buffers). The mobile location CDMA carrier buffer 106 stores baseband data on a per carrier basis that has been down converted from a given carrier. As such, each buffer contains stored information, on a per carrier basis, for all users of the carrier. The shared location resource controller 104 also programs the programmable CDMA carrier selector 110 to generate the CDMA carrier select control signal 124 to program digital down conversion to the appropriate carrier.

The mobile location CDMA carrier buffer 106 may be any suitable buffer or buffers that store, for example, CDMA carrier information such as digital base band data on a per carrier basis per phase array antenna over a period of time.

The programmable single site location engine 108 uses angle of arrival and time of arrival algorithms to distinguish among received signals, for example, where there is a phased antenna array as the antenna elements 102a and 102b. The angle and time of arrival algorithms may also use, for example, prompt ray algorithms to detect the earliest arriving ray as a basis for selecting the appropriate signal to be used for angle arrival and time of arrival purposes. This information may be used to determine, for example, angle and distance data serving as the mobile location data for any given mobile. This information location may be converted to any suitable form, such as longitude and latitude information or any other suitable information to indicate a mobile unit's location. The mobile unit location apparatus 100 may also be, for example, used as part of a single site mobile unit location apparatus so that signals from other antenna sites are not used in the determination of the mobile unit's location. As such, the programmable mobile location engine 108 may be a single site programmable location engine.

The analog front end stage 112 includes an analog down converter that is shared for the mobile unit location apparatus 100 and for a networked radiotelephone transceiver 140 (e.g., traffic channel transceiver circuitry). The programmable CDMA carrier selector 110 is operatively coupled to the programmable mobile location engine 108 through the mobile location CDMA carrier buffer. The networked radiotelephone transceiver 140 receives CDMA carrier data 126 for conventional traffic channel processing as known in the art. The mobile location CDMA carrier buffer 106 stores a snapshot of the this data, with buffer control and refresh rates determined by the processing speed of the location engine. The shared location resource controller 104 also provides network radio telephone transceiver control signal 144 to effectively multiplex the CDMA carrier data 126 at the appropriate times. The programmable single site location engine 108 generates the mobile location data 118 through baseband data analysis. For example, prompt-ray time arrival detection, phased array angle of arrival detection, amplitude difference angle of arrival detection or other suitable location technique may be used. One type of technique may be found in co- pending U.S Patent Application entitled "Method and Apparatus for Locating a Remote Unit Within a Communication System'^' having inventors Pfeil et al., attorney docket number CE08027R, filed on even date, owned by instant assignee and hereby incorporated in its entirety by reference. Such a location technique may include the extraction of channel estimates (e.g., bias, delays, amplitudes, frequency offsets, phase, or other suitable parameters) and transforms them into location data such as time of arrival data, angle of arrival data or other suitable location data. These estimates are typically transformed to a mobile unit location at the LSN, but can be transformed by any suitable processor at any suitable location. For example, where multi-site measurements are required, the transformations may be made at the basesite transceiver station (BTS) if suitable communication paths are provided.

FIG. 2 illustrates a method of operation of the mobile unit location apparatus 100 shown in FIG. 1. As shown in block 200, the method includes receiving mobile unit location requests, for example, from the location services node. The location requests are stored, for example, in the location server database 116. The shared location resource controller 104 may read the data to obtain the mobile unit location request. The mobile unit location request may include, for example, mobile identification (MID) data, electronic serial number (ESN) and any other suitable data. As shown in block 202, the method includes determining which base site transceiver station or stations are handling a given mobile based on the mobile ID, which CDMA carrier a particular mobile is using in which sector within a cell, and a base site transceiver station being used to communicate with a given mobile. This may be done, for example, by the location server as part of the location services node 1 14. This may be done, for example, by the location server querying a base site controller, MSC, or other suitable entity and receiving suitable responses with respect to such queries.

As shown in block 204, the method includes forwarding the requisite data to the appropriate base site transceiving station. This may be done by the location server or other suitable entity. As shown in block 206, the process includes receiving and aggregating the location requests forwarded, for example, by the location server. This may be done, for example, by the shared location resource controller 104 which reads the stored request data 150 (FIG. 1) from the location server database 116. The shared location resource controller 104 aggregates the mobile unit location request, for example, by collecting all location requests received from the LSN, sorting them on a per carrier basis, and then further sorting them based on prioritization codes provided by the LSN. The shared location resource controller 104 then initiates location determination using an order based on the sorting operations.

As shown in block 208, the process includes selecting a CDMA carrier associated with a given sector for a particular mobile unit for a given set of aggregate location requests. This is shown, for example, in block 210. In block 212, the method includes, for a CDMA carrier in a particular sector, generating and sending the mobile identification data for those mobiles that are to be located. This may be incorporated as part of the programmable location engine control signal 122 which may also include time stamp data indicating which sections of a mobile location CDMA carrier buffer to look at based on matching the time stamps. The location engine operates on time stamp information that is additionally contained within the mobile location CDMA carrier buffer. The mobile location CDMA carrier buffers receive samples from the analog down conversion processes. Each digital sample represents a sample of the signal at a given point in time. A clock reference within the mobile location CDMA carrier buffer stores the timestamp indicating when a given sample was sampled or stored in the buffer. The shared resource location controller synchronizes the signal reconstruction algorithms of the location engine with the actual received signal contained in the baseband data stored in the mobile location CDMA carrier buffers. These timestamps are also used to determine an appropriate timestamp representing the point in time at which the location estimation occurred.

As shown in block 214, the process includes generating the mobile location CDMA carrier buffer control signal 120 to indicate that a mobile location CDMA carrier buffer should be flushed. Where a plurality of mobile location

CDMA carrier are used, such as where one mobile location CDMA carrier buffer is used for each CDMA carrier so that per mobile location can be more readily performed, the mobile location CDMA carrier buffer control signal 120 may be communicated over any suitable bus in any suitable form. Once a given mobile location CDMA carrier buffer is suitably flushed, as shown in block 216, the method includes selecting the suitable CDMA carrier based on the mobile identification data. This may be performed, for example, by using the CDMA carrier select control signal 124 to control a programmable down converter to output a particular CDMA carrier to obtain baseband data stored in the mobile location CDMA carrier buffer. As shown in block 218, the selected CDMA carrier data is stored in the mobile location CDMA carrier buffer. As shown in block 220, the process includes sending a buffer ready signal to the programmable mobile location engine to inform the programmable mobile location engine that the mobile location CDMA carrier buffer is ready for reading. The storage of the mobile location CDMA carrier data may be controlled by suitably controlling the mobile location CDMA carrier buffer to start data acquisition and then freezing -l ithe contents of the mobile location CDMA carrier buffer for use by the programmable mobile location engine. As shown in block 222, the process includes generating the mobile location data 118 on a per mobile basis by performing multiple location estimation passes on the buffered baseband data. The stored baseband data for a given carrier contains CDMA signals from each of the mobile channels present on a given CDMA carrier. Thus location algorithms can be performed by using this same stored data (using either parallel location engines, or serially by repetitively supplying the baseband data contained in the mobile location CDMA carrier buffer to one location engine using one mobile/channel at a time. It will be recognized that any suitable combination may also be used.

As shown in block 224, the method includes communicating the mobile location data 118 to the shared location resource controller. The mobile location data may be provided in a batch format or as a mobile unit has been located. As shown in block 226, the process includes sending the location data to the location services node or other entity that wishes to use the mobile location data. This is shown in block 226. The process then continues to evaluate other mobile location requests for other sectors as desired.

FIG. 3 illustrates an alternative embodiment of a mobile unit location apparatus 300 that employs a multi-element phased array antenna 302 and an analog front end stage 304 that in addition to the functions described with reference to FIG. 1 , also includes a programmable common local oscillator. In addition to the operations described with reference to FIGs. 1 and 2, the mobile unit location apparatus 300 uses a shared location resource controller 306 that also generates a local oscillator frequency control signal 308 to control the programmable common local oscillator to select any one of a plurality of CDMA carriers received over the phased array antenna 302. In addition, the mobile location CDMA carrier buffer 106 is shown as being a plurality of mobile location CDMA buffers 310a-310n, wherein each of the plurality of mobile location CDMA carrier buffers 310a-310n is controlled by the mobile location CDMA carrier buffer control signal 120 to receive CDMA carrier data 126 on a per mobile unit basis (e.g., per CDMA carrier basis). Accordingly, the mobile location CDMA carrier buffer control signal 120 may be suitably communicated over a bus. As previously noted, the programmable mobile location engine 108 may also have a separate location engine coupled to each of the plurality of mobile location CDMA carrier buffers 310a-3 lOn. The shared location resource controller outputs the mobile location CDMA carrier buffer control signal for each of the plurality of mobile location CDMA carrier buffers 310-310a. Each of the programmable mobile location engines makes a plurality of passes, on a per mobile basis, of the baseband data stored in a respective mobile location CDMA buffer.

As shown, the plurality of antenna elements, namely the multi-element phased array antenna 302, receives incoming CDMA encoded information. The programmable CDMA carrier selector is operatively coupled to the multi-element phased array antenna 302 and is operatively responsive to the CDMA carrier select control signal 124 to output selected CDMA carrier data 126 to the appropriate mobile location CDMA carrier buffer 310a-310n, such as based on, for example, mobile identification data obtained from a mobile unit location request.

The analog front end stage 304 includes a programmable local oscillator that is operatively coupled to the multi-element phased array antenna 302 and is responsive to the local oscillator frequency control signal 308 to facilitate selective conversion of received incoming CDMA encoded information. The operation of the system of FIG. 3 is substantially identical to that previously described in FIG. 2. However, with the multi-element phased array antenna 302, a programmable common local oscillator is used in the analog front end to selectively output CDMA carrier data used for mobile unit location. The analog front end is also coupled to a networked radiotelephone transceiver stage (not shown) that may use other antenna elements to receive CDMA traffic channel information. It will be recognized that the programmable common local oscillator may not be required if a non-phased array configuration is used, such as a sectorized antenna configuration.

Accordingly, the disclosed apparatus and methods provide for shared resource usage and single site mobile unit location operation. As per carrier CDMA channel data is received, the assigned and coordinated location engines perform location determinations in a multipass fashion. Each pass through a given CDMA carrier buffer provides location analysis for a unique CDMA channel location request. The shared resource controller serves as a type of data routing device to route received CDMA carrier data to one of a plurality of mobile location CDMA carrier buffers and corresponding location engines. The per carrier data buffers (i.e, the mobile location CDMA carrier buffers) are selectively connected to receive the digitized data streams by the shared resource controller. Where a programmable common local oscillator is used, the shared resource controller also programs the local oscillator to coordinate data buffering and queuing as needed by location engines. Each location engine may use a searcher and demodulator with temporal and spatial processing engines. As a result, the disclosed apparatus and methods reduce the amount of front end hardware required to locate all traffic channel mobile units in a multi-carrier CDMA system.

The disclosed apparatus may be employed using any suitable programmed processing devices, analog circuitry, digital logic, state machines, software, firmware or any suitable combination thereof as desired. It should be understood that the implementation of other variations and modifications of the invention in its various aspects will be apparent to those of ordinary skill in the art, and that the invention is not limited by the specific embodiments described. For example, the mobile location engine can also be used to provide input to a multi-site fused measurement which is calculated at the location services node. It is therefore contemplated to cover by the present invention, any and all modifications, variations, or equivalents that fall within the spirit and scope of the basic underlying principles disclosed and claimed herein.

Claims

1. A mobile unit location apparatus for a radiotelephone transceiver that receives CDMA encoded information comprising: a shared location resource controller operative to output at least, a mobile location CDMA carrier buffer control signal and a programmable location engine control signal, a mobile location CDMA carrier buffer, operatively responsive to the mobile location CDMA carrier buffer control signal and operatively coupled to store CDMA carrier data for use in determining mobile location data; and a programmable mobile location engine, operative to provide mobile location data in response to the programmable location engine control signal and based on stored CDMA carrier data.

2. The mobile unit location apparatus of claim 1 wherein the mobile location CDMA carrier buffer includes a plurality of mobile location CDMA carrier buffers wherein each of the plurality of mobile location CDMA carrier buffers is controlled to receive CDMA carrier data on a per mobile unit basis.

3. The mobile unit location apparatus of claim 1 wherein the programmable mobile location engine is a single site programmable location engine.

4. The mobile unit location apparatus of claim 1 wherein the programmable mobile location engine makes a plurality of passes, on a per mobile unit basis, through baseband data stored in the mobile location CDMA carrier buffer.

5. The mobile unit location apparatus of claim 2 wherein the shared location resource controller outputs a mobile location CDMA carrier buffer control signal for each of the plurality of mobile location CDMA carrier buffers.

6. A mobile unit location method for a radiotelephone transceiver that receives CDMA encoded information comprising the steps of:

(a) generating a mobile location CDMA carrier buffer control signal and a programmable location engine control signal,

(b) selectively storing, in response to the mobile location CDMA carrier buffer control signal, CDMA carrier data for use in determining mobile unit location data; and

(c) providing mobile location data based on the programmable location engine control signal and the stored CDMA carrier data.

7. The mobile unit location method of claim 6 wherein step (c) includes providing single site mobile location data based on the programmable location engine control signal.

8. The mobile unit location method of claim 6 wherein generating the mobile location CDMA carrier buffer control signal includes selectively controlling a plurality of mobile location CDMA carrier buffers wherein each of the plurality of mobile location CDMA carrier buffers is controlled to receive CDMA carrier data on a per mobile unit basis.

9. The mobile unit location method of claim 6 wherein the step of providing mobile location data includes providing single site based mobile location data based on CDMA encoded information received over a phased array antenna.

10. The mobile unit location method of claim 6 including the step of making a plurality of passes, on a per mobile unit basis, through baseband data stored in at least one of the plurality of mobile location CDMA carrier buffers.