HK1034827A - Combined gps and wide bandwidth radiotelephone terminals and methods - Google Patents

Description

Combined GPS and broadband radiotelephone terminal and method

Technical Field

The present invention relates generally to wireless communication systems and methods, and more particularly to receivers for wireless mobile terminals.

Background

Wireless communication systems are commonly used to provide voice and data communications to a plurality of users within a defined geographic area. For example, analog cellular radiotelephone systems, known as AMPS, ETACS, NMT-450, and NMT-900, have been successfully established worldwide. Recently, digital cellular radiotelephone systems such as IS-54B in North America (and its later generation IS-136) and GSM in Europe have been introduced and are being established. These and other systems are described in the cellular radio system of Balston et al, 1993 by Artech Press, Norwood, Mash. In addition to the above systems, a system called Personal Communication Service (PCS) is being developed. Examples of current PCS systems are IS-95, PCS-1900 and PACS in North America, DECT in Europe, and PHS in Japan. These PCS systems operate at 2 gigahertz (GHz) and are typically used for voice and high bit rate data communications.

Fig. 1 illustrates a conventional terrestrial wireless communication system 20 that may employ any of the wireless communication standards described above. The wireless system may have one or more wireless mobile terminals 22 in communication with a plurality of cells 24 of a base station 26 and a Mobile Telephone Switching Office (MTSO) 28. Although only three cells 24 are shown in fig. 1, a typical cellular radiotelephone network may include hundreds of cells, and may include more than one MTSO 28, serving thousands of wireless mobile terminals 22.

The cells 24 are typically nodes in the communication system 20 from which connections are established between wireless mobile terminals 22 and MTSOs 28 through the base stations 26 serving these cells 24. Each cell 24 is assigned one or more dedicated control channels and one or more traffic channels. This control channel is a dedicated channel for transmitting cell identification information and paging information. Traffic channels carry voice and data information. A duplex radio communication link 30 may be established throughout the communication system 20 between two wireless mobile terminals 22, or between a wireless mobile terminal 22 and a landline telephone user 32 via a Public Switched Telephone Network (PSTN) 34. In general, the base stations 26 are used to handle radio communications between the cells 24 and the wireless mobile terminals 22. In this regard, the base station 26 functions as a relay station for data and voice signals.

Fig. 2 illustrates a generic sky (celestial) wireless communication system 120. This one-antenna wireless communication system 120 may be used to perform the functions performed by the ordinary terrestrial wireless communication system 20 of fig. 1. In particular, the sky wireless communication system 120 generally includes one or more satellites 126 that act as relays or repeaters between one or more earth stations 127 and the satellite wireless mobile terminals 122. The satellite 126 communicates with the satellite radioterminals 122 and the earth station 127 via a duplex communications link 130. Each earth station 127 may be coupled to a PSTN 132 to support communication between wireless mobile terminals 122, and between wireless mobile terminals 122 and either conventional terrestrial wireless mobile terminals 22 (fig. 1) or landline telephones 32 (fig. 1).

The skyward wireless communication system 120 may cover the entire area of the system with one antenna beam or, as shown in fig. 2, the skyward wireless communication system 120 may generate multiple slightly overlapping beams 134, each serving a geographic coverage area 136 within the system's service area. The satellite 126 and the footprint 136 function as the base station 26 and the cell 24, respectively, of the terrestrial wireless communication system 20.

The sky wireless communication system 120 is thus used to perform the functions of a conventional terrestrial wireless communication system. In particular, the sky radiotelephone communications system 120 may have particular application in wide geographic areas where human smoke is scarce, or where rugged terrain makes ordinary land-line telephone or terrestrial wireless infrastructure technically or economically impractical.

As the wireless communication industry continues to evolve, it is likely that additional technologies will be incorporated into these communication systems to provide value-added services. One such technology is the Global Positioning System (GPS). Therefore, there is a need for integrating a GPS receiver in a wireless mobile terminal. It is clear that "global positioning system" or "GPS" is used to denote a spatial system for measuring positions on the earth, including the european GLONASS satellite navigation system.

Fig. 3 shows a GPS system. As is well known to those skilled in the art, GSP is a space-based triangulation system that uses satellites 302 and computer 308 to measure position anywhere on the earth. The GPS system was originally established by the united states department of defense as a defense navigation system. Compared with other land-based systems, GPS coverage is not limited, and can provide 24-hour uninterrupted service without being limited by weather conditions, and is also very accurate. GPS technology is provided with the highest accuracy for military use, and less accurate for civilian use.

In operation, a group of 24 satellites 302 orbiting the earth continuously transmit GPS radio frequency signals 304 at a predetermined chip frequency (chip frequency). The GPS receiver 306, such as a handheld radio receiver having a GPS processor, receives the radio signals from the nearest satellites and measures the time taken by those radio signals from the GPS satellites to the GPS receiver. Multiplying the time of flight by the speed of light, the GPS receiver can calculate the range of each satellite in line of sight. The GPS processor can use the triangulation algorithm to calculate the position of the GPS receiver using additional information given by the satellite radio signal, including satellite orbit and velocity information and its clock information.

Brief description of the invention

It is therefore an object of the present invention to provide a wireless mobile terminal that integrates a Global Positioning System (GPS) receiver.

It is another object of the present invention to provide a wireless mobile terminal integrated with a GPS receiver that is inexpensive to manufacture and operates efficiently.

To achieve these objects and others, the present invention employs a combination GPS and broadband radiotelephone wireless mobile terminal that shares many components. In particular, the GPS receiver of the present invention shares the IF band with some sky or terrestrial radiotelephone standards. Further, some sky or terrestrial radiotelephone standards share common signal processing tasks that process the signal to find the long code length therein. Thus, the only major difference is the received frequency.

The wireless mobile terminal of the present invention includes a GPS Radio Frequency (RF) receiver and a wideband radiotelephone RF receiver having a bandwidth at least equal to one-half the GPS signal chip frequency. The wireless mobile terminal also has a common Intermediate Frequency (IF) section for both the GPS RF receiver and the wide band radiotelephone RF receiver. The demodulator is connected to a common IF section. Thus, the same circuitry can be used except for the GPS RF front end and the wide band radiotelephone RF front end, which operate at different frequencies. But to reduce manufacturing costs, the two terminals can be made as a single dual-band front end. This can improve efficiency.

In a preferred embodiment of the invention, the wide band radiotelephone RF receiver is a Code Division Multiple Access (CDMA) RF receiver including a Universal Mobile Terminal System (UMTS), also known as wideband CDMA, or Time Division Multiple Access (TDMA) RF receiver. The frequency bandwidth of CDMA and TDMA RF receivers is approximately 1MHz, which is comparable to the GPS bandwidth. Thus, many of the components may be identical except for the received RF band. For CDMA, the demodulator is preferably a CDMA spread spectrum despreader. For TDMA, the demodulator is preferably a TDMA demodulator.

In fact, due to the close bandwidth, a combined GPS/CDMA receiver can be made, wherein the bandwidth of the CDMA receiver is the same as that of the GPS receiver. In this case, the IF and the detuning can be effectively combined.

It is also possible to combine the GPS RF receiver with a part of the TDMA/CDMA RF receiver. For example, a dual band antenna may be used, wherein a GPS RF receiver having a GPS RF filter is coupled to the dual band antenna, and wherein a wideband radiotelephone RF receiver includes a spread spectrum RF filter coupled to the dual band antenna. The wideband RF amplifier and filter can then be shared in the RF section.

In other embodiments of the invention, the GPS and CDMA/TDMA IF sections may be different or they may share components such as a local oscillator. In other embodiments, a common demodulator, such as a despreader, may be used, but all other components are not.

The method for receiving wireless communication signals by the mobile terminal comprises the following steps: receiving a GPS RF signal at a predetermined chip frequency in a first RF channel and receiving a wideband radiotelephone RF signal in a second RF channel, wherein the wideband radiotelephone RF signal has a bandwidth at least equal to one-half the chip frequency of the GPS RF signal. The GPS RF signals and the wide band radiotelephone RF signals are then demodulated in a common demodulator. The demodulator may have a common mixer. Thus, a wireless mobile terminal and a wireless communication receiving method with high efficiency and low cost can be obtained.

Brief Description of Drawings

Fig. 1 illustrates a conventional terrestrial (cellular) wireless communication system.

Fig. 2 illustrates a conventional sky (satellite) wireless communication system.

Fig. 3 illustrates a Global Positioning System (GPS).

Fig. 4 to 9 are block diagrams illustrating a wireless mobile terminal and a wireless communication receiving method in the present invention.

Fig. 10 illustrates the coherence loss caused by filtering in a GPS receiver.

Description of The Preferred Embodiment

The present invention will now be described in detail with reference to the accompanying drawings, in which preferred embodiments of the invention will be given. This invention may, however, be embodied in many other forms and should not be construed as limited to the embodiments set forth herein; rather, these examples are given solely for the purpose of more fully describing the invention, and are intended to fully convey the substance of the invention to those skilled in the art. Like numbers refer to like elements.

The idea behind the invention derives from the fact that the GPS receiver function and some radio telephones use the same IF and that part of it performs the same task of processing the signal to find the long code length. Therefore, the components of the GPS receiver and the broadband radiotelephone receiver can be effectively combined to constitute the wireless mobile terminal and the receiving method, thereby improving the efficiency and reducing the working cost.

The details of GPS systems and wideband radiotelephone systems such as CDMA and TDMA systems are well known to those skilled in the art and need not be described in detail herein. Also, subsystems comprising these systems are well known to those skilled in the art and need not be described in detail. Therefore, this detailed description will introduce, at the level of the block diagram, various embodiments that can effectively combine a GPS receiver and a broadband radiotelephone receiver.

Referring now to fig. 4, a wireless mobile terminal and a wireless communication receiving method of the present invention are illustrated. As shown in FIG. 4, the wireless mobile terminal and method of the present invention includes a GPS RF receiver 410 and a wide bandwidth radiotelephone RF receiver 420 having a bandwidth at least equal to one-half the GPS RF signal chip frequency. The shared IF section 430 is connected to the GPS RF receiver 410 and the wideband radiotelephone RF receiver 420. A demodulator such as despreader 450 is connected to the shared IF section.

The wideband radiotelephone RF receiver 420 is preferably a CDMA or TDMA RF receiver. The GPS RF receiver 410 and the wide band radiotelephone RF receiver 420 also preferably have similar bandwidths in the different RF frequency bands. The GPS RF receiver 410 and the wide band radiotelephone RF receiver 420 preferably have the same bandwidth in different RF bands.

More specifically, there are many cellular telephone standards that have an IF bandwidth of about 30kHz, such as the AMPS or digital AMPS standards, or 270kHz, such as the GSM standards. These narrow bands are not sufficient to receive 1MHz GPS signals. However, there are indeed some cellular telephone standards that employ an IF band of at least 1 MHz. These include the IS-95 CDMA standard, which has a bandwidth of 1.2 MHz, including the Digital European Cordless Telephone (DECT) TDMA standard, which has a bandwidth of approximately 1MHz, and the japanese CDMA standard, which has a bandwidth of up to 5 MHz. Satellite communication systems, such as GLOBALSTAR, are also being designed and developed with similar bandwidth and CDMA signal processing. Thus, the present invention can employ shared GPS and wideband radiotelephone signal IF processing and shared despreading processes, including demodulation/coherence/baseband processing. Different RF frequencies with similar bandwidths can be supported.

In particular, it is known that the coherence loss due to filtering in a GPS receiver is a function of the bandwidth to frequency ratio. This coherent loss increases rapidly when the bandwidth is less than 50% of the chip frequency. See fig. 10, which is the textbook "global positioning system: theory and application, first volume "page 350, fig. 12, this text is incorporated herein by reference. For example, if the chip rate is 1.023 MHz and a loss within 3dB is acceptable, then the single sideband (half the bandwidth) of the receiver may be 0.25 x 1.023 MHz, i.e., about 255 kHz. The total bandwidth is then about 511kHz, i.e. about half the chip rate. As shown in fig. 10, the coherence loss increases rapidly over a narrower bandwidth.

Figure 5 shows another general embodiment of the present invention. In this embodiment, there is a single GPS RF receiver 510 and wideband radiotelephone RF receiver 520, and a single GPS IF section 530 and wideband radiotelephone IF section 540. There is also a common demodulator, such as despreader 550. This embodiment may be required when a different IF section is to be employed.

Referring now to fig. 6, a more detailed embodiment of a combined GPS/broadband radiotelephone terminal and method is shown. As shown in FIG. 6, the GPS RF section includes a GPS antenna 612, an RF filter 614, an RF amplifier 616, and an RF filter 618. The wideband radiotelephone RF section includes a cellular antenna 611, an RF filter 613, an RF amplifier 615, and an RF filter 617. There is also a separate GPS mixer 630 and wideband radiotelephone mixer 640, each of which employs respective local oscillators 632 and 642. A switch 644 is used to switch between the GPS and the broadband radiotelephone system. There is a common IF filter 646 and a common demodulator, such as despreader 650 (demodulator/correlator/baseband processor). Similarly, there is a common microprocessor 652 and memory 654.

It will be apparent to those skilled in the art that the terminal and method shown in fig. 6 can be constructed by adding a GPS antenna 612, an RF filter 614, an RF amplifier 616, an RF filter 618, a mixer 630, a local oscillator 632, and a switch 644 to a conventional CDMA cellular telephone terminal, with this combined unit operating in GPS/CDMA dual mode according to the digital signal processing scheme in the switch 644 and the coherent/baseband processor 650 and microprocessor 652. The adaptation software may be required to search for different codes and slightly different chip rates (code rates) and then use this information correctly for each task.

To receive the GPS signals, code phase shifts (codebases) may be found for each satellite in view, and the time and ephemeris data may be obtained by demodulating the data. Within the microprocessor 652, these data are combined to determine location. In cellular telephone applications, the polarity of the code is further processed in the CODEC to obtain the data for the voice signal. It is apparent that fig. 6 does not show the transmission path in the CDMA cellular phone terminal for clarity.

It is apparent that in the terminal and method shown in fig. 6, the code phase shift for each satellite in view can be obtained from an internal almanac or from information provided over a cellular telephone link. This information may be stored in memory 654 and then switched from GPS mode to CDMA cellular telephone mode. This code phase shift information may be sent over a cellular telephone link to a server where the location is determined using other information obtained from a central point.

Referring now to FIG. 7, another embodiment of the present invention is shown. The components in fig. 7 correspond to those in fig. 6, except that a common oscillator 732 is used for the GPS mixer 630 and the wideband radiotelephone mixer 640. In application No. 08/925566 entitled "system and method for sharing reference frequency signals in a wireless transceiver and a global positioning system receiver within a wireless mobile terminal," assigned to the assignee of the present invention and co-workers inventor Horton and Camp, JY., which is hereby incorporated by reference herein, it is described how to share a local oscillator in a dual mode GPS/radiotelephone terminal. In the embodiment shown in fig. 7, the circuitry controlling oscillator 732 may be adjusted to provide an appropriate frequency signal to support reception of GPS signals or wideband radiotelephone signals.

Fig. 8 shows another embodiment in which a mixer 830 and a local oscillator 832 are common. Thus, switch 844 is used to couple the two RF signals to mixer 830. Referring to fig. 7, the oscillator may be readjusted to provide an appropriate frequency signal.

The GPS/DECT and GPS/WCS terminals and methods may employ a similar architecture. In DECT, without the coherence function, digital hardware and firmware/software programs may be required to complete the coherence process within the digital source.

Referring now to fig. 9, a terminal and method for sharing part of an RF system is presented. As shown in fig. 9, a dual-band GPS and cellular antenna 910 may accept GPS and broadband radiotelephone signals. A pair of switches 911 and 912 are used to select the appropriate GPS RF filter 914 or cellular filter 913. Although the filters are shown as separate filters, they may be implemented as a shared filter with variable or switching elements. There is a wideband RF amplifier 915 and a mixer 830. There is also an oscillator 832, an IF filter 646, a despreader 650, a microprocessor 652 and a memory 654, as previously described. It is clear that separate GPS and cellular antennas may be employed rather than dual band GPS and cellular antennas and a common broadband amplifier.

In the drawings and specification, there have been disclosed typical preferred embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.

Claims (30)

1. A wireless mobile terminal for use in a wireless communication system, comprising:

a Global Positioning System (GPS) Radio Frequency (RF) receiver that receives GPS signals at a predetermined chip frequency;

a wideband radiotelephone RF receiver having a bandwidth at least equal to one-half of the predetermined chipping frequency;

a shared Intermediate Frequency (IF) section coupled to the GPS RF receiver and the wide band radiotelephone RF receiver; and

a demodulator is coupled to the shared IF section.

2. The wireless mobile terminal of claim 1 wherein the wide band radiotelephone RF receiver is a Code Division Multiple Access (CDMA) RF receiver and wherein the demodulator is a CDMA despreader.

3. A wireless mobile terminal according to claim 1, wherein the wide band radiotelephone RF receiver is a Time Division Multiple Access (TDMA) RF receiver and wherein the demodulator is a TDMA demodulator.

4. The wireless mobile terminal of claim 1 wherein the GPS RF receiver and the wide band radiotelephone RF receiver have similar bandwidths in different RF frequency bands.

5. The wireless mobile terminal of claim 1 wherein the GPS RF receiver and the wide band radiotelephone RF receiver have the same bandwidth in different RF frequency bands.

6. The wireless mobile terminal of claim 1 wherein the GPS RF receiver comprises a GPS antenna and wherein the wideband radiotelephone RF receiver comprises a wideband radiotelephone antenna.

7. The wireless mobile terminal of claim 1, further comprising a dual band antenna, wherein the GPS RF receiver includes a GPS RF filter coupled to the dual band antenna, and wherein the wideband radiotelephone RF receiver includes a spread spectrum RF filter coupled to the dual band antenna.

8. The wireless mobile terminal of claim 7, further comprising a wideband RF amplifier coupled to the GPS RF filter and the wideband radiotelephone RF filter.

9. A method of receiving a wireless communication signal in a mobile terminal, comprising the steps of:

receiving a Global Positioning System (GPS) Radio Frequency (RF) signal at a predetermined chip frequency on a first RF channel;

receiving a wideband radiotelephone RF signal on a second RF channel, wherein the wideband radiotelephone RF signal has a bandwidth at least equal to one-half the predetermined chipping frequency; and

the GPS RF signals and the wideband radiotelephone RF signals are demodulated with a shared demodulator.

10. The method of claim 9, wherein the wideband radiotelephone RF signal is a Code Division Multiple Access (CDMA) RF signal, and wherein the step of demodulating comprises the step of despreading the gps RF signal and the wideband radiotelephone RF signal in a shared despreader.

11. The method of claim 9, wherein the wideband radiotelephone RF signal is a Time Division Multiple Access (TDMA) RF signal.

12. The method of claim 9, wherein the GPS RF signal and the wide band radiotelephone RF signal have similar bandwidths in different RF frequency bands.

13. The method of claim 9, wherein the GPS RF signal and the wide band radiotelephone RF signal have the same bandwidth in different RF frequency bands.

14. The method of claim 9, wherein the step of demodulating includes the step of mixing the gps RF signal and the wideband radiotelephone RF signal with a shared mixer.

15. A wireless mobile terminal for use in a wireless communication system, comprising:

a Global Positioning System (GPS) Radio Frequency (RF) receiver receiving a GPS signal at a predetermined chip frequency;

a wideband radiotelephone RF receiver having a bandwidth at least equal to one-half of the predetermined chipping frequency;

a GPS Intermediate Frequency (IF) section coupled to the GPS RF receiver;

a wideband radiotelephone IF section coupled to a wideband radiotelephone RF receiver; and

a shared demodulator is connected to the GPS IF section and the broadband radiotelephone IF section.

16. The wireless mobile terminal of claim 15, wherein the wide band radiotelephone RF receiver is a Code Division Multiple Access (CDMA) RF receiver and wherein the shared demodulator is a shared spread spectrum despreader.

17. The wireless mobile terminal of claim 15 wherein the wide band radiotelephone RF receiver is a Time Division Multiple Access (TDMA) RF receiver.

18. The wireless mobile terminal of claim 15 wherein the GPS RF receiver and the wide band radiotelephone RF receiver have similar bandwidths in different RF frequency bands.

19. The wireless mobile terminal of claim 15 wherein the GPS RF receiver and the wide band radiotelephone RF receiver have the same bandwidth in different RF bands.

20. The wireless mobile terminal of claim 15, wherein the GPS RF receiver comprises a GPS antenna and wherein the wideband radiotelephone RF receiver comprises a wideband radiotelephone antenna.

21. The wireless mobile terminal of claim 15, wherein the GPS IF section and the wide band radiotelephone IF section include a shared local oscillator.

22. A method of receiving wireless communication signals in a mobile terminal, comprising the steps of:

receiving a Global Positioning System (GPS) Radio Frequency (RF) signal at a predetermined chip frequency on a first RF channel;

receiving a wideband radiotelephone signal at a second RF channel, wherein the wideband radiotelephone signal has a frequency band at least equal to one-half of the predetermined chipping frequency;

mixing the GPS RF signal and the wideband radiotelephone signal with GPS and wideband radiotelephone mixers, respectively; and

the mixed GPS RF signal and the mixed wideband radiotelephone signal are demodulated with a shared demodulator.

23. The method of claim 22, wherein the wideband radiotelephone RF signal is a Code Division Multiple Access (CDMA) RF signal and wherein the demodulating step comprises the step of despreading the mixed GPS RRF signal and the mixed wideband radiotelephone signal with a shared despreader.

24. The method of claim 22, wherein the wideband radiotelephone RF signal is a Time Division Multiple Access (TDMA) RF signal.

25. The method of claim 22, wherein the GPS RF signal and the wide band radiotelephone RF signal have similar bandwidths in different RF frequency bands.

26. The method of claim 22, wherein the GPS RF signal and the wide band radiotelephone RF signal have the same bandwidth in different RF frequency bands.

27. A wireless mobile terminal for use in a wireless communication system, comprising:

a Global Positioning System (GPS) receiver receiving a GPS signal at a predetermined chip frequency; and

a wideband radiotelephone receiver having a bandwidth at least equal to one-half of the predetermined chipping frequency;

wherein the GPS receiver and the broadband radiotelephone receiver share a demodulator.

28. The wireless mobile terminal of claim 27, wherein the GPS receiver and the wide band radiotelephone receiver further share a mixer.

29. The wireless mobile terminal of claim 27, wherein the wide band radiotelephone receiver is a Code Division Multiple Access (CDMA) receiver and wherein the demodulator is a spread spectrum demodulator.

30. The wireless mobile terminal of claim 27, wherein the GPS receiver and the wide band radiotelephone receiver have the same bandwidth in different radio frequency bands.