System and method of doppler and local oscillator compensation in a TDMA system

A traffic station comprising:

• a transmitter;
• a receiver;
• a controller communicatively coupled to the transmitter and the receiver, the controller configured to:
• cause said transmitter to transmit, via a first uplink channel, a burst of information from said traffic station to a network device;
• monitor an output of said receiver to identify a reference burst and the burst of information re-transmitted from the network device and received at said traffic station;
• calculate a Doppler offset ratio based on the burst of information received at said traffic station from the network device, a downlink frequency shift based on the reference burst received at said traffic station, and a local oscillator offset ratio based on the Doppler offset ratio and the downlink frequency shift;
• and
• selectively adjust a transmission frequency for a second uplink channel of said transmitter based on the Doppler offset ratio and said local oscillator offset ratio.

A computer-readable medium having computer-executable instructions for performing a method comprising the following steps:

• transmitting, via a first uplink channel, a first burst of information to a network device;
• receiving, via one or more downlink channels, the first burst of information and a reference burst from the network device;
• calculating a combined frequency shift based on the received first burst of information;
• calculating a Doppler offset ratio based on the calculated combined frequency shift;
• calculating a downlink frequency shift based on the received reference burst;
• calculating a local oscillator offset ratio based on the Doppler offset ratio and the calculated downlink frequency shift;
• adjusting a transmission frequency for a second uplink channel based on the Doppler offset ratio and the local oscillator offset ratio;
• after receiving the reference burst and the first burst of information, receiving, via the one or more downlink channels, a second reference burst from the network device;
• calculating an updated downlink frequency shift based on said second reference burst, and an updated Doppler offset ratio based on said updated downlink frequency shift and the local oscillator offset ratio that was previously calculated;
• and
• adjusting the transmission frequency for the second uplink channel based on the updated Doppler offset ratio and the local oscillator offset ratio that was previously calculated;
• wherein said combined frequency shift is a frequency shift due to the velocity of the traffic station relative to the network device, combined with any frequency shift introduced by a timing difference between a timing source used by the network device and a timing source used by the traffic station;
• and
• wherein said combined frequency shift is determined by analyzing demodulated data contained in said burst of information rather than by directly measuring the frequency of carrier wave.

A method for determining an optimal transmission center frequency, comprising the steps of:

• transmitting, via a first uplink channel, a burst of information from a traffic station to a network device;
• receiving at said traffic station, from the network device, a reference burst in a Time Division Multiple Access (TDMA) frame;
• if the received TDMA frame contains the burst of information that was transmitted by the traffic station to the network device, calculating a Doppler offset ratio based on the burst of information received in the TDMA frame, calculating a downlink frequency shift based on the reference burst, calculating a local oscillator offset ratio based on the Doppler offset ratio and the downlink frequency shift, and adjusting a transmission frequency for a second uplink channel based on the Doppler offset ratio and the local oscillator offset ratio;
• and
• if the received TDMA frame does not contain the burst of information that was transmitted by the traffic station to the network device, calculating an updated downlink frequency shift based on the reference burst, calculating an updated Doppler offset ratio based on the updated downlink frequency shift and a previously calculated local oscillator offset ratio, and adjusting the transmission frequency for the second uplink channel based on the updated Doppler offset ratio and the previously calculated local oscillator offset ratio;
• wherein said Doppler offset ratio is determined based on a combined frequency shift due to the velocity of the traffic station relative to the network device, combined with any frequency shift introduced by a timing difference between a timing source used by the network device and a timing source used by the traffic station;
• and
• wherein said combined frequency shift is determined by analyzing demodulated data contained in said burst of information rather than by directly measuring the frequency of a carrier wave.