Field of the Invention The present invention relates generally to radio or wireless communications and, more particularly, relates to a position determination system for a wireless communication device.

Background of the Invention The advent of wireless personal communications devices has revolutionized the telecommunications industry. Cellular, PCS and other services provide wireless personal communications to businesses and individuals at home, in the office, on the road, and any other locations the wireless network reaches. Wireless telephone subscribers no longer have to use pay telephones along the road, or wait until they return home or to the office to check messages and return important business calls. Instead, wireless subscribers carry out their day to day business from their cars, from the jobsite, while walking along the airport concourse, and just about anywhere their signals are accessible.

Thus, it is no surprise that since the introduction of the cellular telephone service, the number of wireless telephone subscribers has increased steadily. Today, the number of wireless telephone subscribers is staggering and still growing rapidly. In fact, many households have multiple wireless telephones in addition to their conventional land-line services.

With a market of this size, there is fierce competition among hardware manufacturers and service providers. In an attempt to lure customers, most providers offer handsets with desirable features or attributes such as small size, light weight, longer battery life, speed dial, and so forth. Many recent additions to the marketplace include multi-functional handsets that even provide pocket-organizer functions integrated into the wireless handset. Most manufacturers, however, are still scrambling to add new features to their communication devices to snare a portion of this booming market.

One desirable feature is a system and apparatus for determining the position of the wireless device. Location data gathered by the system can be transmitted to a remote server in order to provide useful features and information to the user. One design challenge in implementing such a system is to provide a position-determination device that is easily connectable to the wireless device and has a convenient power source. Another design challenge is providing a convenient message format for sending the location data gathered by the position determination device to the remote server.

Summary of the Invention The present invention is directed toward a position determination system for a wireless communication device. A position determination device is provided that generates location data, and a power adapter powers both the position determination device and the wireless handset. Moreover, the power adapter conveys location data received from the position determination device to the wireless handset. The present invention also provides a novel message syntax for relaying the location data from the wireless handset to a remote server.

In one embodiment of the invention, a wireless position determination system is provided. It includes a power adapter configured to couple to a pre-existing power supply.

The power adapter has a two-level voltage translator for translating a voltage Vinput provided by the power supply into two voltage levels Vl and V2. A wireless communication device is coupled to the power adapter and receives the voltage level V2 from the power adapter. The communication device includes a transceiver for sending and receiving communications across a wireless communication network.

The system also includes a position-determination device for determining the location of the wireless device and generating location data. The position determination device is coupled by a power/data line to the power adapter, receives the voltage level V1 from the power adapter, and transmits the location data to the power adapter. The power adapter, in turn, provides the location data to the communication device.

In one implementation, the position determination device includes a GPS antenna and a GPS receiver, and the pre-existing power supply is a cigarette lighter of an automobile. In a further implementation, the location data is sent to a remote server using a novel DTMF messaging syntax. The DTMF messaging syntax includes a message separation sequence, a field separation character, and at least one pre-defined message field. The pre-defined message fields may include latitude, longitude and caller ID fields.

Another embodiment of the present invention provides a position determination system. The system includes a position-determination device for determining the location of the device and generating location data. The system also includes a computer that receives the location data from the position-determination device. The computer is connected to the position-determination device via a mouse port to provide power to the device, and is also connected to the device via a serial communications port for receiving the location data from the device.

Objects and advantages of the present invention include any of the foregoing, singly or in combination. Further objects and advantages will be apparent to those of ordinary skill in the art, or will be set forth in the following disclosure.

Brief Description of the Drawings The present invention is described with reference to the accompanying drawings.

In the drawings, like reference numbers indicate identical or functionally similar elements, and Figure 1 is a diagram illustrating an example wireless communication device.

Figure 2 is a block diagram of a wireless communication system according to the present invention.

Figure 3 is a flowchart illustrating a method for requesting information across a wireless network according to the present invention.

Figure 4 is a block diagram of a first embodiment of a position determination system according to the present invention.

Figure 5 is a block diagram of a second embodiment of a position determination system according to the present invention.

Figure 6 is a diagram of example formats for location information requests responses.

Figure 7 is a block diagram of a processor-based system according to one embodiment of the invention.

Figure 8 is a diagram of a third embodiment of a position determination system according to the present invention.

Figure 9 is a diagram of a fourth embodiment of a position determination system according to the present invention.

Figure 10 is a block diagram of a fifth embodiment of a position determination system according to the present invention.

Figure 11 is a diagram illustrating use of an inventive DTMF messaging syntax in conjunction with the position determination system according to the present invention.

Detailed Description of Preferred Embodiments 1. Introduction and Overview The present invention provides a location-based information retrieval system for wireless communication devices. Several embodiments of position determination systems are also provided. The location of the device, as determined by the position determination system, can be used to provide additional information or features to a user of the wireless communication device. Examples of the information that may be provided include map information; driving information; location information; location of retailers, goods, services, or other points of interest near the communication device; and any other information that may be useful or valuable to a user of the communication device. The device location is sent to a remote server that accesses and compiles the requested information and sends it back to the user via the communication device.

2. Example Environment Before describing the invention in detail, it is useful to describe an example environment in which the invention can be implemented. One example environment is a handset or communication device operating within a wireless communication network such as, for example, a cellular, GSM, PCS or radio communication network. Wireless communication devices embodying the present invention can be implemented in various configurations and architectures. Typically, a wireless communication device will include

a keypad for control of the device and data entry, and a display for displaying relevant information.

An example wireless communication device 100 is illustrated in Figure 1.

Communication device 100 is presented for illustrative purposes only; implementation of the invention is not dependent on any particular device architecture or communication network.

Device 100 includes a processor 104, a speaker 106, a display 108, a keypad 110, a transceiver 112, a memory 114, a microphone 116, a power source 118 and an antenna 120. Device 100 is typically a mobile device such as a handheld handset or an integrated vehicle phone. It is configured to communicate with other communications devices such as base station 112. Base station 112 is typically within a geographic area known as a "cell"and handles communications for all wireless devices within the cell.

Processor 104 directs the overall operation of device 100. A computer program or set of instructions is typically coded or otherwise implemented on the processor to enable the processor to carry out the device operation. Memory 114 interfaces with processor 104 and may store program code and provide storage space for data useful in executing the program code and carrying out the device functions. Memory 114 may be implemented as ROM, RAM or any other convenient memory format. The features and functionality of the invention described below may be implemented using hardware, software, or a combination thereof, and such software can run on a processor such as processor 104 and be stored in a memory such as memory 114.

Transceiver 112 includes a transmitter that transmits voice and data information via antenna 120 to a recipient communication device such as, for example, base station 112. Transceiver 112 also includes a receiver that receives voice and data information

from another communication device (e. g., base station 112). The received voice and data information is provided to the user or used to facilitate device operation.

User interface features include speaker 106, display 108, keypad 110, and microphone 116. Microphone 116 accepts voice or other audio information from the user and converts this information into electrical signals that can be transmitted by transceiver 112. Likewise, speaker 106 converts electrical signals received by transceiver 112 into audio information that can be heard by a user of device 100. Display 108 displays information such as call information, keypad entry information, signal presence and strength information, battery life information, or any other information useful to the user.

Display 108 preferably takes the form of a liquid crystal display (LCD), which have low power consumption characteristics, but could also be implemented as a light emitting diode (LED) display or any other appropriate visual indicator. Keypad 110 typically includes an alphanumeric keypad and may also include special function keys. In one embodiment, keypad 110 is backlit to permit viewing of the keys in low light or dark conditions. Device 100 may also include a flip panel (not shown) that can be closed to conceal some or all of the keypad.

Power source 118 is provides power to device 100. It can be implemented with rechargeable batteries, such as NiCad or NiMH rechargeable batteries, or with any other suitable power source.

3. A Location-Based Information Retrieval System Figure 2 is a block diagram illustrating a wireless communication system according to the present invention. The communication system provides information to a wireless device user based on the location of the user and his device. It includes a wireless handset 130 and a hands-free 132 incorporating a position determination system 134.

Handset 130 can be implemented in a configuration such as device 100 of Figure 1, or in

any other wireless communication device capable of communicating with remote locations via a wireless communication medium. In the description below,"handset"refers to any communication device capable of communicating with other devices via a wireless medium.

Hands-free unit 132 is optionally provided to allow the user of wireless device 130 to communicate in a hands-free mode. Hands-free unit 132 may include a microphone and speaker to provide wireless device 130 with speakerphone-like capabilities. Such capabilities are particularly desirable where wireless device 130 is utilized in an automobile or other mobile situation. In one implementation, hands-free unit 132 is configured according to conventional industry standards for a"hands-free kit".

As mentioned above, in addition to the conventional standards, hands-free unit 132 is equipped with a first embodiment of a position determination system 134 to determine the location of unit 132 and handset 130. Alternatively, position determination system 134 may be directly incorporated into handset 130. Position determination system 134 determines location in terms of parameters such as latitude, longitude, height, speed of travel, and any other useful location or position parameters. In one embodiment, position determination system 134 is implemented using a GPS (global positioning system) or differential GPS. The design and configuration of GPSs is well known to those of ordinary skill in the art. Alternative position determination systems could also be utilized.

One example of an alternative position determination system is a triangulation system. In such a system, the position of handset 130 is determined by triangulating a signal from handset 130 with the fixed locations of two or more base stations.

Triangulation systems, though useful and relatively inexpensive, have several drawbacks.

Errors due to multipath signal transmission may occur and the systems may be inoperable in areas where only one base station is available.

Wireless device 130 preferably includes both a voice and data interface, particularly where position determination system 134 is incorporated in a hands-free unit 132. The voice interface provides hands-free operation and speakerphone-like capabilities. The data interface allows position information obtained by system 134 to be provided to handset 130 for transmission over wireless network 140. Moreover, where voice recognition or speech synthesis capabilities are provided (discussion below), the data interface provides the data to be synthesized into speech or the data received via voice recognition.

Handset 130 communicates with other entities via wireless network 140. Network 140 is typically comprised of a plurality of base stations that provide relay points for communication. Network 140 may be a cellular, PCS, GSM, or any other wireless communication network. In addition to conventional communication with other wired or wireless communication devices, as shown in Figure 2, network 140 permits communication between handset 130 and data server (s) 136. When a user requests information, handset 130 provides the location of the handset to server 136 across wireless network 140. Server 136 retrieves relevant information from an associated database 138 and conveys the information to handset 130 over wireless network 140. The information may be displayed on the handset display or audibly rendered via speech synthesis or prerecorded scripts. Although the types of information stored in database 138 are virtually limitless, several example applications are provided for illustrative purposes.

In one example application, driving directions to a destination address are provided to a handset user. The user requests driving directions to the destination via keypad entry and/or voice command, and the request is communicated to server 136 over wireless network 140. At the time of the request, the handset location determined by position determination system 134 is also provided to server 136 to provide a starting point for the

directions. Using the handset location and the destination address, server 136 calculates a route and compiles driving directions. The driving directions are transmitted to handset 130 over network 140 and are displayed or audibly rendered to the user. In addition to textual driving directions, a map showing the route may be displayed on the handset display. Options such as the shortest possible route, interstate route, safest route, most scenic route, etc. may be provided. The user's choice of options will dictate the route calculation. The options may be stored, and prompts or scripts generated, locally (in the memory of handset 130). Alternatively, the options, prompts and scripts may be stored at server 136 and provided to the user via network 140.

Another example application locates particular types of businesses or services in the user's location. Restaurants, gas stations, hotels and other businesses or services near the user's location can be identified and provided to the user. Again, the user requests the business or service type vocally or via keypad entry. The request is communicated to server 136 over wireless network 140, along with the user's current location as determined by the position determination system 134. Server 136, based on the handset location and user request, retrieves and returns relevant information to handset 130 over network 140.

Parameter limits or filters may be implemented to refine the request and selections returned. The user may set a location filter, for example, that requires returned selections be within X miles of the user's current location. If the user is seeking a restaurant, the user may request or be prompted to select parameters that refine the search results. These parameters may include cuisine type (e. g., Italian, French, American, etc.), restaurant type (e. g., fast food, casual dining, formal, etc.), price range and so on. For restaurants as well as gas stations, motels and other businesses, the user may identify a preferred national or regional chain.

As noted above, the search may be refined (the query narrowed) on the user's own initiative or based on system prompts. If the user simply requests a nearby restaurant, for example, server 136 may prompt the user with questions about parameters such as those described above. Alternatively, to conserve bandwidth over network 140, prompts can be stored locally and made by handset 130 (or hands-free unit 132) before the request is sent to server 136. In this embodiment, updated scripts and/or prompts may be downloaded from server 136 to handset 130. Preferably, memory-intensive data such as establishment locations, driving directions, etc. are stored in database 138 to minimize the amount of memory required in handset 130. The precise distribution of data storage among these devices will be influenced by factors such as available bandwidth, memory costs and airtime costs.

The user may also specify avoidance of certain areas or parts of town, such as those that have high crime rates, gang or drug activity, or other undesirable attributes.

Crime statistics from law enforcement authorities or other sources can be compiled and stored in database 138. Based on these statistics, certain areas or neighborhoods may be identified as high crime rate areas or otherwise undesirable areas. The user may opt to not receive choices for establishments in, or driving directions through, those areas. This feature can be implemented automatically, as a default selection or through a user prompt.

Alternatively, the system may provide an automatic warning sound or indication to alert the user of entry into a high-crime-rate area. This feature is particularly useful if the user is unfamiliar with a particular area in which he or she is travelling.

A method for requesting information across network 140 is illustrated in Figure 3.

In step 202, a user initiates a request for information. As described above, this request can be made via a keypad entry or by voice command with an appropriate voice recognition system. In step 204, the system determines whether the request requires the handset

location or position. If all information is based on positional information, this step can be eliminated on the assumption that answering any request requires positional information.

Since many requests may be fulfilled based on previously transmitted position information or without any position information at all, however, inclusion of step 204 is preferable to avoid unnecessary transmission of position information over network 140.

If position information is required, the method proceeds from step 204 to step 212, where position determination device 134 acquires the position of handset 130. In one implementation, position determination occurs somewhat constantly while handset 130 (or unit 132) is powered on. If position determination device 134 is situated in hands-free unit 132, unit 132 provides the position data to handset 130 for transmission to server 136 over wireless network 140 (step 214). If position information is not required, the method proceeds from step 204 directly to step 206.

In step 206, handset 130 sends the request to server 136 via wireless network 140.

The request includes any position data acquired in steps 212-214. In step 208, server 136 retrieves the data or information requested from database 138. The data may be retrievable and usable in raw form, or it may need to be processed. This determination is based on the type of request, the information requested, and the manner or format in which the information is stored in database 138. The raw or processed data is communicated to handset 130 over network 140 and, in step 210, is displayed or provided to the user.

As described above, scripts or prompts may be provided to the user to refine the information request. If the scripts or prompts are stored in database 138 (as opposed to local storage in handset 130), they are retrieved by server 136 in step 208 and provided to the user in step 210. The user's answers to the prompts are sent by handset 130 to server 136, which uses the refined information to retrieve additional data or information from database 138, or to further refine the user's query. This potentially repetitive process is

illustrated in Figure 3 by flow line 222 and the repetition of steps 202,206 and 208.

During this repetitive prompting process, depending on time elapsed and distance traveled, updated position information may be provided to server 136. If the refining prompts are stored locally in device 130 or unit 132, refinement occurs before the query is sent and this repetitive process will not usually be necessary.

Once the request has been sufficiently refined, server 136 uses the refined request to retrieve data from database 138. Continuing with the examples described above, server 136 may retrieve locations of restaurants, gas stations, hotels, or other facilities or services near the user. In one implementation, the information is listed or ranked in order of best matches to the user's request and/or preferences. The listing of facilities or services matching the request is provided to handset 130 over network 140 (step 208), and the information is audibly or visually provided to the user (step 210). If the information is provided audibly, audio data can be prerecorded or synthesized by server 136 and transmitted over network 140, or data can be sent across network 140 and speech synthesized locally.

Once the user selects a facility or service from the list of options provided, server 136 can retrieve or compute driving directions to the facility or service based on the user's current position. If sufficient time has elapsed to significantly alter the user's current position, server 136 may request a position update. In one implementation, a speed of travel parameter is provided by handset 130 along with the current position. In this implementation, the determination of whether to update the position information can be based in part on this parameter. Where the user is traveling at a high rate of speed, positional updates will be required often to ensure accurate directions. Additionally, where the user is approaching a freeway exit or other waypoint in the route being computed, server 136 may request a position update to ensure that this waypoint has not

been passed. If it has been passed, an alternative route may be calculated or the user may be directed to backtrack to the passed waypoint.

4. Position Determination System (First and Second Embodiments) As stated above, in one embodiment, position-determination device 134 is located in hands-free unit 132. Figure 4 illustrates in more detail the first embodiment of the position determination system. Hands-free unit 132 includes a GPS receiver 304 that functions as the position determination device and an associated controller 306. Position information is exchanged with wireless handset 130 via data in-out interface 308.

Antenna 310 allows GPS receiver 304 to communicate with the constellation of GPS satellites. As stated above, alternative position determination devices could be implemented if desired. Speaker 312 and microphone 314 provide speakerphone-like capabilities to wireless device 130. Audio processor 316 provides A/D, D/A and echo canceling for voice digitization or synthesis. Preferably, the digitized voice is in the form of PCM (pulse code modulated) data, although other data coding techniques could be utilized.

As described above, voice synthesis and/or recognition capabilities may be provided. In one implementation, voice synthesis and recognition are provided in hands- free unit 132. Alternatively, wireless device 130 or server 136 could provide these capabilities.

Figure 5 shows a second embodiment of a position determination system including a hands-free unit 132 with voice synthesis and recognition. In this implementation, user speech commands are received by microphone 314, digitized by audio processor 316 and processed by voice recognition algorithm 322. The processed speech commands are provided to controller 306 and sent to server 136 as data 309. Similarly, information retrieved by server 136 can be provided to controller 306 and voice synthesizer 324.

Voice synthesizer 324 converts this information to digital voice data, which is processed by audio processor 316 and announced to the user via speaker 312. Additionally, audio information can be provided to audio processor 316 via audio in-out communication path 308. Where server 136 performs speech synthesis or recognition, digital voice data is sent across network 140 and is provided to, or received from, the user via audio in-out connection 308.

Where position determination device 134 is located in hands-free unit 132, wireless device 130 sends a location information request message to hands-free unit 132.

Hands-free unit 132 in response sends a location information response message to the handset 130. The location information response includes parameters indicating position such as time, longitude, latitude, height, speed, and data age.

Figure 6 is a diagram illustrating an example format for the location information request 404 and the location information response 408. Location information request 404 is a one-byte data field. Response 408 includes several fields, including time 410, longitude 412, latitude 414, height 416, speed 418 and data age 420. Time field 410 is six bytes in length, longitude field 412 is nine bytes in length, latitude 414 is eight bytes in length, height field 416 is eight bytes in length, speed field 418 is three bytes in length, and data age 420 is one byte in length. As would be apparent to one of ordinary skill in the art, other message formats and field lengths could be utilized.

In one embodiment, the time is GPS time of day in seconds and is in ASCII format. Longitude, latitude and speed are also in ASCII format, with the longitude data being positive east, the latitude data being positive north and the speed being in miles per hour. The data age reflects the age of the return data and can indicate whether the data is fresh, old, or otherwise not available. Data is listed as fresh if it is less than ten seconds of

age, or old if it is greater than or equal to ten seconds. Of course, alternative formats can be provided and alternative time frames established for determining if data is fresh or old.

A status request and response may be used to query the status of position determination device 134 before requesting location information. This is particularly useful if position determination device is implemented as a GPS receiver. The request message may be one byte in length and simply request the status of the GPS receiver. In this implementation, the response may be a one byte status word indicating whether the device is ready. The response could include additional information such as, for example, the reason the status is ready or not ready, or any other pertinent information.

The various embodiments and features of the invention described above may be implemented with hardware, software or a combination thereof and may be implemented using a computing system having one or more processors. In one embodiment, these elements are implemented using a processor-based system capable of carrying out the functionality described with respect thereto. An example processor-based system 502 is shown in Figure 7. System 502 includes one or more processors, such as processor 504.

Processor 504 is connected to communication bus 506.

System 502 includes main memory 508 and secondary memory 510. Main memory 508 is preferably random access memory (RAM), and secondary memory 510 preferably includes hard disk drive 512 and/or a removable storage drive 514. Removable storage drive 514 is typically a floppy disk drive, a magnetic tape drive, an optical disk drive or the like. Storage drive 514 reads from and writes to removable storage media 518 in a well-known manner. Storage media 518 is typically a floppy disk, magnetic tape, optical disk or the like having stored therein computer software and/or data.

Secondary memory 510 may include additional or alternative means for allowing computer programs or other instructions to be loaded into computer system 502. A

removable storage unit 522 and interface 520, for example, may be provided. Interface 520 and storage unit 522 could take the form of a program cartridge and cartridge interface (such as that found in video game devices), or a removable memory chip (such as an EPROM, or PROM) and associated socket.

Communications interface 524 allows software and data to be transferred between computer system 502 and external devices. Examples of communications interface 524 include a modem, a network interface (such as, for example, an Ethernet card), a communications port, or a PCMCIA slot and card. Software and data is transferred via communications interface 524 as electronic, electromagnetic, optical or other signals capable of being received by communications interface 524. These signals are provided to communications interface via channel 528. Channel 528 carries signals and can be implemented as a wireless medium, wire or cable, fiber optics, or other communications medium. Examples include a phone line, a cellular phone link, an RF link or a network interface.

In this document, the terms"computer program medium"and"computer usable medium"are used to generally refer to media such as removable storage device 518, a disk capable of installation in disk drive 512, and signals on channel 528. These computer program products are means for providing software or program instructions to computer system 502. Computer programs (also called computer control logic) are stored in main memory and/or secondary memory 510. Computer programs can also be received via communications interface 524. Such computer programs, when executed, enable the computer system 502 to perform the features of the present invention as discussed herein.

In particular, the computer programs, when executed, enable the processor 504 to perform the features of the present invention. Accordingly, such computer programs represent controllers of the computer system 502.

In an embodiment where the elements of the invention are implemented using software, the software may be stored in, or transmitted via, a computer program product and loaded into computer system 502 using removable storage drive 514, hard drive 512 or communications interface 524. The control logic (software), when executed by the processor 504, causes processor 504 to perform the functions of the invention as described herein.

In another embodiment, the elements are implemented primarily in hardware using components such as PALs, application specific integrated circuits (ASICs) or other hardware components. Implementation of a hardware state machine to perform the functions described herein will be apparent to persons skilled in the relevant art (s). In yet another embodiment, elements are implemented using a combination of both hardware and software.

5. Position Determination System (Embodiments 3-5) Figure 8 illustrates a third embodiment of a position determination system 600.

Position determination system 600 includes a tracker device 602, which may be marketed by the assignee under the name"Neotracker". Tracker 602 includes a GPS antenna 604 and a GPS receiver module 606. The GPS antenna and receiver determine the geographic location of tracker 602. The design and configuration of GPS antennas and receivers are well known to those of ordinary skill in the art.

Tracker 602 is coupled to vehicle power adapter (VPA) 610 via a power/data line 608. VPA 610 is connected to a power source to provide power to both tracker 602 and an associated wireless handset 612. In one implementation, VPA 610 is configured to plug into an automotive power source, such as a conventional cigarette lighter outlet. In addition to providing power to tracker 602, line 608 transmits the location data provided by GPS antenna 604 and receiver 606 over line 611 to VPA 610. VPA 610, in turn,

conveys the location data to wireless handset 612, which exchanges the information with a server or other remote device as described above. Wireless handset 612 may be configured in a similar fashion to wireless device 100 of Figure 1.

Figure 9 depicts a fourth embodiment 620 of a position determination system.

System 620 includes a tracker 622 including a GPS antenna 624 and receiver 626.

Tracker 622 is configured in like fashion as tracker 602 of Figure 8. Tracker 622 is coupled to a computer 630 via a power/data line 628. Power/data line is connected in a dual configuration to computer 630. A first connection 632 is coupled to the mouse I/O port of computer 630. The mouse port provides enough power to power the GPS components of tracker 622. A second connection 634 is coupled to the serial communications port of computer 630. Data such as location information is exchanged between tracker 602 and computer 630 via connection 634 and the serial communications port.

In one implementation, computer 630 is programmed with or has stored in memory mapping software that uses the location data provided by tracker 622. Commercial software programs that use GPS data are suitable. Hence, the software program will accept the location data provided by tracker 622 via the serial port, and use it to display a route or give driving directions to the user, who has an input a destination he would like to reach.

Considering both Figures 8 and 9, it can be seen that the tracker provided by the present invention can be used both with a wireless device, in order to communication location data to a server, as well as with a personal computer, in order to provide location data for use in a mapping application.

Figure 10 depicts a fifth embodiment 640 of a position determination system.

System 640 is similar to system 600 of Figure 8, but differs in that the tracker and vehicle

power adapter are incorporated in one device 642. Hence, device 642 includes a GPS antenna 644 and GPS receiver 646, which function as described above. Device 642 also includes a two-level voltage translator 648 that accepts a voltage Vjnput from a car power source 650. Power source 650 is typically the automobile cigarette lighter. Translator 650 accepts the voltage input from power source 650 and translates into two levels V1 and V2 for powering, respectively, the GPS components 644,646 and a wireless handset (not shown) connected to phone connector 656.

Voltage V1 is provided to the GPS receiver 646 and antenna 644 along power line 652, and voltage V2 is provided to phone connector 656 along power line 654. GPS receiver 646 also exchanges location data with a wireless handset connected to phone connector 656 via data lines 658 and 659.

Device 642 is advantageous relative to system 600 in that, rather than providing a separate tracker and vehicle power adapter, these components are incorporated into one device that plugs directly into the car power source. The only"free"line will be the line connecting the wireless device to phone connector 656. Device 642 may be a bulkier attachment, however, so system 600 may be preferred when a less bulky attachment is desired.

Figure 11 depicts a system 660 in which GPS/location information gathered by a tracker module 662 is communicated to a remote server 672 using a novel DTMF messaging syntax. DTMF is short for Dual Tone Multi-Frequency, which is a system used by touch-tone telephones. A specific frequency, or tone, is assigned to each key on the telephone keypad so that a detector or microprocessor can easily identify it.

Tracker module 662 is connected to a wireless handset 666 via a communication line 664. Module 662 will include a power adapter and GPS antenna/receiver as described above, and may configured as separate components (Figure 8) or as one component

(Figure 10). The location data is communicated to a remote DTMF detector 670 and server 672 via a wireless communications network or medium 668. Network 668 is analogous to network 140 of Figure 2.

The location/GPS data is communicated over network 668 using a novel DTMF messaging syntax. Before describing this novel syntax, previous methods of CDMA messaging will be described to provide a backdrop. In an implementation where handset 666 is a CDMA mobile end station, several methods are known to convey information from the handset to a geographically remote server (672). The CDMA Standard specifies at least three methods: SMS (Short Message Service) mobile-originated messages, data calls, and DTMF tones over voice calls. Each of these methods is known to those of ordinary skill in the art and will not be described in detail herein.

Each of these three methods has associated advantages and disadvantages. SMS messages are restricted in size and tend to be shorter in nature. Moreover, at the present time, not all active CDMA base stations provide full SMS messaging functionality. When a data call is used, after the call is connected, any amount of information can be passed (back and forth) between the CDMA handset and server.

Use of DTMF tones over voice calls involves using the same DTMF tones that are used to indicate handset key presses. Although DTMF tone usage has the slowest throughput of the three methods described above, it has several important advantages.

First, for companies that support customer assistance centers, the overhead of using DTMF tones for data transmission is minimal. Second, the same voice call to the server is also used to pass information. Separate banks of data lines and modems are not required, and there is no issue with base station compliance, since the base stations are already configured to support handset key pressing. Finally, for analog lines, off-the-shelf DTMF detectors and decoders are readily available for nominal expense.

The novel messaging system of the present invention, by contrast, uses DTMF messaging syntax during data calls to communicate GPS information. The DTMF tones are simply replaced with their ASCII character equivalents. The advantage of using data calls is that the communications path contains a readily accessible return path for status or other reverse information. The server, of course, must be have a data modem of some sort on the dialed line. Both analog lines connected to data modems as well as CDMA handsets in incoming data mode are suitable for this purpose.

Several considerations were taken into account in developing the novel syntax of the present invention. To support the widest range of interoperability, only the most common DTMF tones were used. Only DTMF tones'0'through'9','*' (star), and'#' (pound) were used. DTMF tones'A'through'D', which certain DTMF generators or detectors/decoders may not support, were excluded from the syntax. Moreover, because either the DTMF transmitter or receiver could reset asynchronously, the syntax provides a recovery mechanism to prevent catastrophic (unrecoverable) failure. As will be explained below, a device that starts listening at any point in time will eventually be able to extract/parse messages from the data stream. Because DTMF tones are sent in frequencies measured in Hertz, the syntax minimizes the number of characters transmitted in order to minimize spectrum waste. Finally, though the format is extensible, the covered portions show enough regularity to permit sanity checking of incoming messages.

The table below summarizes an exemplary DTMF messaging sequence in accordance with the present invention Name DTMF Tones Comment Message Separator ##*## Separates distinct messages Latitude Field 123*45678 Fractional rep. of latitude Field Separator Separates fields Longitude Field 123*45678 Fractional rep. of longitude Field Separator (optional) Separates fields Caller ID Field (optional) 8585528400 Area code plus number Message Separator ##*## Separates distinct messages

The DTMF message separation sequence consists of the following five DTMF tone sequence :'##*##' (pound) (pound) (star) (pound) (pound). This sequence precedes and follows any valid DTMF message. A device that beings listening at a random point within a data stream will eventually be able to extract messages from the stream through recognition of the message separation sequence. As indicated above, fields within a given message are separated by the field separation character'#' (pound).

Any number of user definable fields may be added to the DTMF message. When determining the field format, the field separation character (#) should not be used as part of any field. Non-existent fields (not DTMF tones between separation characters) are also not allowed. Non-numeric fields (i. e., fields consisting merely of one or more'*' characters, with no numeric'0'through'9'tones) are also strongly discouraged.

The example above shows three user-defined fields: a latitude field, a longitude field, and a caller ID field. The latitude and longitude fields are completely numeric representations, with the'*"character used as a decimal point. Negative numbers will begin with a'*'tone, while positive numbers will begin with a numeric DTMF tone.

Positive numbers are the default setting. The whole number portion (before the decimal point) is represented by three digits and the fractional portion (after the decimal point) is represented by five digits. Any unused portions should be stuffed with leading or

following zeroes. If the latitude/longitude field does not consist of 3 numeric tones, followed by a'*'tone, followed by five numeric tones, it is considered to be corrupted/erroneous. The caller ID field is optional and provides a caller identifier. The calling phone number, including area code, is one possible format of this field. Other ID fields, such as membership numbers or other identifiers, could also be used.

An example application for a position determination system in combination with the DTMF messaging syntax, where a voice channel is used, is a situation in which a wireless handset user places a call to a service provider, such as a towing service or a rental car company. The location data would be gathered by the GPS components within tracker 662 and provided to handset 666. When the user makes the call to the service provider, the location data would be converted into latitude and longitude and transmitted in accordance with the messaging syntax described above over network 668 to the provider's DTMF decoder 670. Other information, such as caller identification, may also be transmitted. The detector decodes the DTMF tones, and transmits the decoded location/identification data to the provider's server 672. This information may be used by the service to provider to assist in providing services (i. e. dispatch of a tow truck) to the user.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.