Wireless communication system for adapting to frequency drift

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG.
1 illustrates a wireless communication system of the present invention and referred to by the general reference number 10.
The system 10 includes a remote transceiver 12 to communicate, over a wireless bilateral communication link 13, with a base transceiver 14.
In the preferred embodiment, the bilateral communication link 13 operates in a frequency range of approximately 902 MHz to approximately 928 MHz.
Typically, the system 10 will include multiple remote transceivers as represented by additional remote transceivers 16 and 18.
The system 10 operates in bursts, with each burst having a selected time and a pre-determined carrier frequency.
The pre-determined frequency for the remote transceiver 12, 16 and 18 is a successive entry in a pseudo-random sequence that is unique to that remote transceiver 12, 16 and 18 to give the effect of a frequency hop spread spectrum.
The time length of the burst is less than four hundred milliseconds, thereby meeting the FCC requirements for spread spectrum communication.
The selected time for the remote transceiver 12, 16 and 18 is controlled by the base transceiver 14 to avoid collisions.
In the preferred embodiment, the system 10 uses an FSK modulation having a rate of 2.
4 kilo baud and a frequency deviation of approximately, six KHz.
Alternatively, the system 10 can use phase modulation, such as binary phase shift key (BPSK), constant amplitude BPSK, quadrature phase shift key (QPSK), offset QPSK, constant amplitude QPSK, MSK, eight phase shift key (8PSK), or equivalent, or frequency modulation, such as FM.
The remote transceivers 12, 16 and/or 18 initiate the burst by transmitting a wireless data signal.
The wireless data signal includes a preamble, a frame character, and application data.
Although the carrier frequency is pre-determined, component drift in the remote transceiver 12, 16 and/or 18 due to aging and change in temperature can cause a frequency error of up to 30.
times.
10.
sup.
6 times the approximate RF frequency of the link 13