MXPA99007714A - Wireless communication device and system incorporating location-determining means - Google Patents

Abstract

A device, method and system which enables the location of a wireless communication device to be accurately determined without requiring the device to perform extensive signal processing or calculations. The wireless device frequency converts a location-determining signal from an initial frequency to the frequency of a standard communication channel, and transmits the frequency-converted signal to a base station in a conventional manner. A location-determining receiver associated with the base station receives the location-determining signal and determines the location of the wireless communication device based on the location-determining signal.

Description

WIRELESS COMMUNICATION DEVICE AND SYSTEM THAT INCORPORATES A MEANS TO DETERMINE THE LOCALIZATION FIELD OF THE INVENTION The present invention relates generally to the location of wireless communication devices, particularly when a wireless communication device is located in a clogged area. More particularly, the present invention offers a method, device and system that incorporates GPS into a wireless communication system. BACKGROUND OF THE INVENTION The development and refinement of wireless communication services and devices continue to occur at an extremely fast rate. A problem associated with wireless communication devices concerns the determination of the physical location of a device. It may be highly desirable to locate a wireless communication device for various purposes such as, for example, when it is believed that a subscriber associated with the device is in an emergency situation, or when the device has been misplaced. A solution to this problem should be carefully considered within the limits of cost, size and power consumption of wireless communication systems and devices. The problem is further aggravated when the wireless communication device is located in a clogged area, such as, for example, inside a building. A proposed solution for determining the location of a wireless communication device is the use of a wireless communication device such as, for example, a responder, the device returning a location determination signal to several base stations. The delay in the echo signal is used to determine the distances between the wireless communication device and each of several base stations. The transmitted location can therefore be determined from the locations of the base stations and the determined distances. However, it is difficult to measure the echo signal delay with sufficient precision, particularly when the wireless communication device is located in a clogged area. A second proposed solution is based on the well-known Global Positioning Satellite (GPS) system, and includes the incorporation of a GPS receiver into the wireless communication device. In the GPS system, a device whose location must be monitored (in this case, the wireless communication device, but more typically a ship, plane, truck, etc.) has a GPS receiver. The GPS receiver can determine its location on the surface of the earth, with an accuracy of approximately 150 feet, based on signals transmitted to the receiver by a GPS satellite. In operation, the GPS receiver receives a coded location determination signal in terms of time from a first GPS satellite. The receiver determines the time required by the location determination signal to reach the ground by comparing its time of departure (from the satellite with its arrival time at the receiver). Based on this time differential, and considering a transmission speed of, for example, 186 miles per second, the receiver calculates the distance to the first satellite (for example, 13 thousand miles). Based on information programmed in advance regarding the orbit of the satellite, the receiver can determine where the satellite is in space at the time the signal is sent, and the receiver can use this information to determine that its Location is somewhere on the surface of a sphere that has a radius from the satellite equal to the distance determined (in this example, 13,000 miles). The receiver repeats this process using signals to determine the location of additional GPS satellites, and finally determines based on the points of intersection of the resulting spheres, where are you. Unfortunately, a typical GPS receiver is larger than a typical wireless communication device. Even when the GPS receiver is reduced in size, the incorporation of the GPS receiver in a wireless communication device would have an important impact on the size of the device. In addition, well-known GPS receivers do not have enough performance capabilities to determine a location within a clogged area such as inside a building. Any solution to the problem of determining the location of a wireless communication device that includes significant signal processing operations within the wireless device will drastically affect the device cost, power consumption, and / or performance. Accordingly, it would be highly desirable to be able to accurately determine the location of a wireless communication device, particularly when the device is located in a clogged area such as on the inside of a building, so that it does not significantly impact the cost. , size, performance or power consumption of the wireless communication device. SUMMARY OF THE INVENTION The present invention overcomes the problems described above, and achieves other advantages by providing a wireless communication system, device and method for determining the location of a wireless communication device that does not have a significant impact on the device itself. In accordance with exemplary embodiments, the wireless communication device, which can communicate with a base station in a communication channel, is equipped with a location determination circuit for receiving a location determination signal (e.g., a GPS signal). ), for converting the received signal from a first frequency to a second frequency, and for transmitting the location determination signal with frequency conversion in the communication channel to a location determination receiver. The location determination receiver is preferably a GPS receiver associated with the base station. According to exemplary embodiments of the method of the present invention, a location determination signal (e.g., GPS) is transmitted at a first frequency from a location determination system to the wireless communication device. The location determination signal is then converted from the first frequency to a second frequency by means of the wireless communication device, and the location determination signal with frequency conversion is transmitted at the second frequency to one or more frequency receivers. determination of location tuned to the second frequency. To improve the location of the wireless device to be determined when the device is located in a clogged area, and to ensure that the location determination signal is properly received, the transmission of the location determination signal with frequency conversion may occur in a power level greater than the power level of the communication signals exchanged in an ordinary manner between the wireless device and the control station. Alternatively, or in addition to this feature, the control station associated with a location determination receiver may temporarily suspend the communication links with other wireless communication devices on the second frequency in response to receiving the frequency conversion signal or of a precursor signal transmitted by the wireless device before transmitting the signal with frequency conversion. The present invention allows the location of a wireless communication device to be determined without significantly impacting the size, cost, performance or power consumption of the wireless communication device. BRIEF DESCRIPTION OF THE DRAWINGS The present invention can be more fully understood by reading the following Detailed Description of the Preferred Modalities in combination with the accompanying drawings, wherein: Figure 1 is a block diagram of a wireless communication system in accordance with an embodiment of the present invention; Figure 2 is a block diagram of a transmitter circuit of a wireless communication device in accordance with an embodiment of the present invention; and Figure 3 is a flow diagram showing the steps for determining the location of a wireless communication device in accordance with an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED MODALITIES Figure 1 shows an exemplary wireless communication system in accordance with the present invention. The system includes a plurality of mobile communication terminals such as for example a mobile terminal 10 and a plurality of base stations such as for example the base station 12. The mobile terminal 10 exchanges communication signals with the base station 12 in a conventional manner . For purposes of explanation, the invention will be described considering that the mobile terminal 10 and the base station 12 exchange signals in accordance with the principles of Code Division Multiple Access (CDMA). The CDMA signals have a bandwidth of approximately 1.2 MHz, and the GPS signals have a bandwidth of approximately 1 MHz. However, it will be noted that the invention is not limited to CDMA systems, and the principles of the invention are easily adaptable to other types of communication systems. The system of Figure 1 operates in connection with a location determination system which, in this example, is a GPS system. The GPS system includes GPS satellites 14 and one or more GPS receivers 16. Each GPS receiver 16 is preferably associated with a base station 12, either directly or through an optional interconnection device 18. GPS preferably includes at least 2 complete GPS receivers, one of which receives signals from the mobile terminal 10 through the base station 12, and the other receives GPS signals directly from the satellites 14. It is possible to use only one GPS receiver and multiplex it between the two functions. However, such configuration requires a data processor to make corrections for time offsets between measurements. In operation, when it is desired to determine the location of the mobile terminal 10, as for example, when the subscriber associated with the mobile terminal 10 has sent a voice or data message indicating that the subscriber is experiencing an emergency situation, one or several of the GPS satellites 14 transmits a GPS signal to determine the location at 1575.42 MHz. This signal is received at the mobile terminal 10, which converts the GPS signal into frequency from its original frequency to a second suitable frequency for transmission in the conventional CDMA channel, and transmits the GPS signal with frequency conversion to the base station 12. The frequency conversion circuit of the mobile terminal will be described in more detail below in relation to figure 2. base station 12 relieves the GPS signal with frequency conversion to an associated GPS receiver 16, either directly or through a medium optional interconnection 18. Interconnection means 18 converts the GPS signal with frequency conversion from the CDMA channel frequency to its original frequency, and may simply be an inverse version of the frequency conversion circuit of the mobile terminal 10. If no means of interconnection 18 is used, the GPS receiver 16 can be tuned to receive signals directly on the CDMA channel. The GPS receiver 16 uses the GPS signal received through the base station 12, preferably in combination with GPS signals received from other GPS satellites, to determine the location of the mobile terminal.

It will be noted that if receiver 16 includes two separate GPS receivers, two additional tasks can be achieved. First, one of the two receivers operating in a conventional mode with normal GPS signal levels can perform all the functions necessary to correct the location determination - that is, demodulate the GPS signals to obtain positioning information and timing This allows the second receiver powered from the remote unit 10 to have relatively long integration times. The long integration time would prohibit the second receiver from carrying out data demodulation, but it allows the second receiver to carry out code synchronization under very weak (obstructed) signal conditions, while having access to the rest of the information required to find a position. Second, this arrangement allows the system to perform differential GPS, a method to remove residual errors. In accordance with differential GPS, a predicted GPS location generated by the first receiver is compared to its previously determined location and with precision in order to determine correction factors. The determined correction factors are then applied to the location determination data generated by the second receiver in order to determine the location of the wireless communication device.

Figure 2 is a block diagram of the transmitter portion of an exemplary wireless communication device in accordance with the first invention. The transmitter portion includes a location termination circuit path and a transmitter circuit path. The location determination circuit path includes an antenna 20, a filter 22 connected to the antenna 20 for filtering the location determination signals received by the antenna 20 and a mixer 24 connected in order to receive the filtered output of the filter 22. and an oscillator signal provided by an oscillator 26, and to provide an intermediate frequency output signal (which is approximately the same frequency as the output of source 34, discussed below). The transmitter further includes a second filter 28, connected to an output of the mixer 24 for filtering the intermediate frequency. An amplifier 30 is connected to the filter 28, and amplifies the filtered intermediate frequency. The filtered intermediate frequency is provided as an input to a switch 32. The transmitter circuit path includes a source 32 for supplying a modulated intermediate communication signal that carries voice, data or control information to be transmitted from the wireless communication device to the base station. The modulated intermediate communication signal is substantially on the same frequency as the intermediate frequency signal produced by the mixer 24. The source 34 produces the intermediate communication signal as the second input to the switch 32. The state of the switch 32, which can be controlled either by the subscriber (for example, through the operation of a switch or through the capture of a command in the wireless communication device) or by the system (for example through a control signal sent to the wireless communication device by the base station 12), if the transmitter will transmit a signal generated by the location determination circuit path or the transmitter circuit path. The output of the switch 32 is provided as a first input to a second mixer 36, which mixes the switch output of the switch 32 with a second oscillator signal 38. The mixer 36 produces a desired transmission signal, which in this example is a CDMA communication signal at a frequency in the CDMA communication channel. The transmit signal is then filtered by a filter 40, amplified by an amplifier 42, and transmitted to a control station via a transmitter antenna 44. It will be noted that the transmitter circuit path of Figure 2 is substantially identical to the transmitter path of a conventional wireless communication device.

In operation, the transmitter in an initial state operates to transmit communication signals (e.g., voice, data or control signals) to one or more base stations through the transmitter path. In this initial state, the switch 32 is positioned to receive the output of a source 34 and provides the output of the source 34 to the second mixer 36. If the device is placed in a location determination mode, then a signal of determination of location (for example a GPS signal at 1575.42 MHz) is received by the antenna 20, this location determination signal is received and subjected to frequency conversion by elements 22-30, and the state of the switch 32 is changed from the state initial such that the switch 32 provides the location determination signal at the intermediate frequency to the second mixer 36. In this location determination mode, the second mixer 36 frequency converts the location determination signal processed from the intermediate frequency (the frequency of the intermediate frequency signal produced by the mixer 26, which has a bandwidth of about 1 MHz) at a second frequency suitable for transmission in a communication channel (eg, a CDMA communication channel having a bandwidth of approximately 1.2 MHz). In this location determination mode, the communication link established between the wireless communication device and the base station is temporarily interrupted. In a wireless communication device it is incorporated that incorporates the circuit of Figure 2, considering that an appropriate gain is provided by the amplifier 30, the location determination signal is radiated, substantially without change other than the fact of having a different frequency , to one or several base stations by means of a transmitter. The transmitter may first send a precursor signal to indicate to the base station that a location determination signal is about to arrive. The base station then uses a location determination receiver, such as a GPS receiver 16 to determine the location of the wireless device. The location determination receiver may be tuned to the wireless communication channel frequency instead of the initial frequency of the location determination signal, or it may receive the location determination signal at its initial frequency after a circuit, for example, an interconnection means 18 (FIGURE 1) converts again the location determination signal of the communication channel frequency to its initial frequency. It will be noted that a wireless communication device having the circuit of Figure 2 allows the device to incorporate a location determination means without the need to perform signal processing and detection or location calculations on the device itself. Figure 3 shows a flow chart describing the process for determining the location of a wireless communication device in accordance with the present invention. In step 100, a communication link is established between a wireless communication device and a base station. While said communication link is established, communication signals (eg, voice, data or control signals) are exchanged in a conventional manner between the device and the base station. In step 102, the device determines whether it has received a location determination signal, either a signal coming from for example a switch in the device, or a command coming from the base station through the communication link. If this is not the case, the process returns to step 100, and the conventional communication link is maintained. If a location determination signal has been received by the wireless communication device, the device changes modes in step 104 and switch 32 selects the location determination circuit path instead of the standard transmitter path. As a result of this mode change, the conventional communication link is suspended. In step 106, the location determination signal with frequency conversion is transmitted from the wireless communication device to the base station in step 106. After terminating the transmission of the location determination signal (which allows calculations suitable for determination of location by the location determination receiver), the process returns to step 100, where the conventional communication link is re-established. As is evident from the foregoing, the present invention offers a method, system and device for determining the location of a device in a wireless communication system. The invention is particularly advantageous insofar as the device itself is not required to perform significant signal processing functions. While the foregoing description contains many specific details and features, it will be understood that these specific details and features are not limiting for the present invention but are included only for purposes of illustration. Many modifications to the examples presented above will be readily apparent to persons with certain knowledge in the art that do not depart from the spirit or scope of the present invention as defined in the appended claims and their legal equivalents.

Claims (21)

1. CLAIMS A method for determining the location of a wireless communication device, comprising the steps of: transmitting a location determination signal on a first frequency, from a location determination system to the wireless communication device; converting the location determination signal of the first frequency to a second frequency; transmitting the location determination signal converted at the second frequency to one or more location determination receivers tuned to the second frequency; and determining, in one or more location determination receivers, the location of the wireless communication device.
2. The method of claim 1, further comprising the step of: before the conversion step, switching a transmitter path in the wireless communication device from a first transmitter path, wherein the wireless communication device is capable of transmitting communication signals to one or more control stations on the second frequency, to a second transmitter path, wherein the wireless communication device is capable of converting the location determination signal from the first frequency to the second frequency .
3. The method of claim 1, wherein the location determination system is a global positioning satellite (GPS) system, the location determination signal is a GPS signal, and the location determination receiver is a receiver GPS.
4. 4. The method of claim 2, wherein the location determination receivers are associated with one or more control stations.
5. The method of claim 1, comprising the steps of: filtering the location determination signal; converting the filtered location determination signal in a downward manner; filter the converted signal in a descending manner; and amplifying the converted signal in a downward manner, before the conversion step.
6. The method of claim 1, wherein the first frequency is about 1575.42 MHz, and the second frequency is a mobile radio communication frequency.
7. The method of claim 6, wherein the mobile radio communication frequency is of a CDMA channel frequency.
8. The method of claim 2, wherein the transmission of the communication signals is carried out at a first power level, and the transmission of the location determination signal with frequency conversion is carried out at a second power level. greater than the first power level.
9. The method of claim 4, further comprising the step of: transmitting, prior to transmission of the location determination signal with frequency conversion, a precursor signal to one or more control stations associated with one or more determination receivers of location; and suspending in one or several control stations the communication links with other wireless communication devices in the second frequency.
10. The method of claim 1, wherein there are at least two location determination receivers and the determination step is carried out by: predicting a location of a first location determination receiver; comparing the predicted location with a known location of the first location determination receiver to determine error correction factors; and determining a location of the wireless communication device in a second location determination receiver using the determined error correction factors.
11. A wireless communication device comprising: a wireless communication means for communication with one or more control stations in one or more communication channels; a location determining means for receiving a location determination signal from a location determination transmitter, and communication with one or more location determination receivers associated with one or more control stations in one or more communication channels.
12. The device of claim 11, wherein the location determining means includes means for converting the location determination signal from a first frequency to a second frequency for communication into one or more communication channels.
13. The device of claim 11, wherein the location determination signal is a GPS signal, the location determination receivers are GPS receivers, and the location determination transmitter is a GPS satellite.
14. The device of claim 12, wherein the first frequency is approximately 1575.42 MHz, and one or more communication channels are CDMA communication channels.
15. 15. The device of claim 11, wherein the device transmits a precursor signal prior to communication with the location determination receiver, the precursor signal causes each control station associated with the location determination receivers that receive the precursor signal to suspend communication link with other wireless communication devices in the second frequency.
16. The device of claim 11, wherein the device communicates with the control stations at a first power level and communicates with the location determination receivers at a second power level greater than the first power level.
17. 17. A communication system comprising: one or more control stations associated with one or more wireless communication devices, each wireless communication device is capable of exchanging communication signals with a control station or several control stations in one or several communication channels; and a location determination equipment capable of transmitting a location determination signal to a wireless communication device at a location determination frequency, receiving a version with frequency conversion of the location determination signal from the communication device wireless, and determining the location of the wireless communication device from the version with frequency conversion. The system of claim 17, wherein the location determination equipment includes one or more location determination transmitters for transmitting the location determination signal and one or more location determination receivers associated with one or more control stations to receive the version with frequency conversion of the location determination signal. The system of claim 17, wherein the frequency of location determination is approximately

    1575. 42 MHz. The system of claim 17, wherein the version with frequency conversion has a frequency within one of the communication channels. The system of claim 20, wherein the version with frequency conversion is transmitted at a power level greater than the power level of the communication signals. The system of claim 18, wherein each control station associated with a location determination receiver suspends communication with wireless communication devices communicating on the same channel as the frequency conversion version of the location determination signal, in response to reception by the location determination receiver of the version with frequency conversion of the location determination signal.