Systems and methods for sharing reference frequency signals...

Details Systems and methods for sharing reference frequency signals... Systems and methods for sharing reference frequency signals...

2000-02-03

2002-07-23

Maung, Nay (Department: 2681)

Telecommunications

Receiver or analog modulated signal frequency converter

Local control of receiver operation

C455S259000, C455S552100, C455S314000

Reexamination Certificate

active

06424826

ABSTRACT:

FIELD OF THE INVENTION
The present invention generally relates to wireless communications, and more particularly, to the receivers for wireless mobile terminals of wireless communication systems.
BACKGROUND OF THE INVENTION
Wireless communication systems are commonly employed to provide voice and data communications to a plurality of subscribers within a prescribed geographic area For example, analog cellular radiotelephone systems, such as those designated AMPS, ETACS, NMT-450, and NMT-900, have been deployed successfully throughout the world. Recently, digital cellular radiotelephone systems such as those designated IS-54B (and its successor IS-136) in North America and GSM in Europe have been introduced and are currently being deployed. These systems, and others, are described, for example, in the book entitled
Cellular Radio Systems
, by Balston, et al., published by Artech House, Norwood, Mass. (1993). In addition to the above systems, an evolving system referred to as personal communication services (PCS) is being implemented. Examples of current PCS systems include those designated IS-95, PCS-1900, and PACS in North America, DCS-1800 and DECT in Europe, and PHS in Japan. These PCS systems operate around the 2 gigahertz (GHz) band of the radio spectrum, and are typically being used for voice and high bit-rate data communications.
FIG. 1
illustrates a conventional terrestrial wireless communication system
20
that may implement any one of the aforementioned wireless communications standards. The wireless system may include one or more wireless mobile terminals
22
that communicate with a plurality of cells
24
served by base stations
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 comprise hundreds of cells, and may include more than one MTSO
28
and may serve thousands of wireless mobile terminals
22
.
The cells
24
generally serve as nodes in the communication system
20
, from which links are established between wireless mobile terminals
22
and a MTSO
28
, by way of the base stations
26
servicing the cells
24
. Each cell
24
will have allocated to it one or more dedicated control channels and one or more traffic channels. The control channel is a dedicated channel used for transmitting cell identification and paging information. The traffic channels carry the voice and data information. Through the communication system
20
, a duplex radio communication link
30
may be effected 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
. The function of the base station
26
is commonly to handle the radio communications between the cell
24
and the wireless mobile terminal
22
. In this capacity, the base station
26
functions chiefly as a relay station for data and voice signals.
FIG. 2
illustrates a conventional celestial wireless communication system
120
. The celestial wireless communication system
120
may be employed to perform similar functions to those performed by the conventional terrestrial wireless communication system
20
of FIG.
1
. In particular, the celestial wireless communication system
120
typically includes one or more satellites
126
that serve as relays or transponders between one or more earth stations
127
and satellite wireless mobile terminals
122
. The satellite
126
communicates with the satellite wireless mobile terminals
122
and earth stations
127
via duplex communication links
130
. Each earth station
127
may in turn be connected to a PSTN
132
, allowing communications between the wireless mobile terminals
122
, and communications between the wireless mobile terminals
122
and conventional terrestrial wireless mobile terminals
22
(
FIG. 1
) or landline telephones
32
(FIG.
1
).
The celestial wireless communication system
120
may utilize a single antenna beam covering the entire area served by the system, or as shown in
FIG. 2
, the celestial wireless communication system
120
may be designed such that it produces multiple, minimally-overlapping beams
134
, each serving a distinct geographical coverage area
136
within the system's service region. A satellite
126
and coverage area
136
serve a function similar to that of a base station
26
and cell
24
, respectively, of the terrestrial wireless communication system
20
.
Thus, the celestial wireless communication system
120
may be employed to perform similar functions to those performed by conventional terrestrial wireless communication systems. In particular, a celestial radiotelephone communication system
120
has particular application in areas where the population is sparsely distributed over a large geographic area or where rugged topography tends to make conventional landline telephone or terrestrial wireless infrastructure technically or economically impractical.
As the wireless communication industry continues to advance, other technologies will most likely be integrated within these communication systems in order to provide value-added services. One such technology being considered is a global positioning system (GPS). Therefore, it would be desirable to have a wireless mobile terminal with a GPS receiver integrated therein.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a wireless mobile terminal having a global positioning system (GPS) receiver integrated therein and which is inexpensive to manufacture and efficient in operation.
This and other objects of the present invention are provided by a wireless mobile terminal of a wireless communication system that includes a GPS receiver integrated therein for generating position data that can be transmitted by the wireless mobile terminal. It will be understood that the terms “global positioning system” or “GPS” are used to identify any spaced-based system that measures positions on earth, including the GLONASS satellite navigation system in Europe. In the wireless mobile terminal, a wireless transceiver and a the GPS receiver share a frequency reference signal. There are several advantages to this configuration, including the reduction of duplicate components of the wireless transceiver and GPS receiver, lower power consumption because fewer parts are utilized, and enhanced performance of the GPS receiver because of the precision of the frequency reference signal.
In particular, according to the present invention, the wireless mobile terminal of a wireless communication system comprises a wireless transceiver and a GPS receiver, wherein the wireless transceiver and the GPS receiver share a frequency reference signal. The frequency reference signal is utilized by the wireless transceiver in signal demodulation and processing. Likewise, the frequency reference signal is utilized by the GPS receiver in signal demodulation and processing.
In accordance with an aspect of the present invention, the frequency reference signal shared by the wireless transceiver and the GPS receiver is a reference oscillator signal generated, for instance, by a temperature compensated reference crystal oscillator. The reference oscillator signal may be multiplied or divided by a first integer to produce a first GPS local oscillator used in signal conversion to a first intermediate frequency in the GPS receiver. Further, a second conversion stage can be incorporated in the GPS receiver by multiplying or dividing the reference oscillator signal by a second integer (which can include 1) to produce a second GPS local oscillator used in signal conversion to a second intermediate frequency in the GPS receiver. The reference oscillator signal can be further utilized at the GPS receiver by dividing or multiplying the reference oscillator signal by a third integer (which can include 1) to produce a frequency used in signal processing, for instance, as an analog-to-digital sampling signal. The wireless transceiver, on the other hand, may include a

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