Systems and methods for doppler shift compensation in ofdma communications
AssigneeADC Telecommunications, Inc.
InventorHarold A. Roberts
Life of this patent
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Abstract
Systems and methods for determining the relative velocity of a subscriber station with respect to a basestation are provided. In one embodiment, the method comprises sending a query message from a basestation to a subscriber station, the query message requesting a current modulation frequency used by the subscriber station to modulate transmissions; receiving a response to the query message, the response including the current modulation frequency; determining an offset between the current modulation frequency and a target carrier frequency value; and calculating a velocity of the subscriber station based on the offset.
Claims7
A method for determining the relative velocity of a subscriber station with respect to a basestation, the method comprising:
- sending a query message from a basestation to a subscriber station, the query message requesting a current modulation frequency used by the subscriber station to modulate transmissions;
- receiving a response to the query message, the response including the current modulation frequency;
- determining an offset between the current modulation frequency and a target carrier frequency value;
- and
- calculating a velocity of the subscriber station based on the offset.
A method for determining the relative velocity of a subscriber station with respect to a basestation, the method comprising:
- sending a query message from a basestation to a subscriber station, the query message requesting a value of a carrier frequency adjustment applied by the subscriber station to an uplink carrier with respect to a downlink carrier;
- receiving a response to the query message, the response including the value of the carrier frequency adjustment;
- calculating a velocity of the subscriber station based on the value of the carrier frequency adjustment.
A method for determining the relative velocity of a subscriber station with respect to a basestation, the method comprising:
- determining a frequency error of an upstream OFDM signal received from the subscriber station;
- transmitting a frequency adjustment instruction to the subscriber station based on the frequency error;
- maintaining a running sum of frequency adjustments transmitted to the subscriber station;
- determining an offset between a current carrier frequency and a target carrier frequency value based on the running sum;
- and
- calculating a velocity of the subscriber station based on the offset.
Dependencies are inferred from the claim text.