Variable rate coding for forward and reverse link

摘要

A technique for encoding a signal used in a digital communication system in which individual traffic channel data rates may be adapted to specific channel conditions. In particular, a forward error correction coding rate is adapted for individual channels while at the same time maintaining a fixed block size independent of the FEC coding rate. This allows the system data rate to adapt to the channel conditions experienced by a specific user. Thus, users experiencing good communication conditions with low multipath distortion may be allocated higher capacity, whereas users with significant multipath distortion may make use of lower rate (higher levels of coding) error codes to maintain high quality. Messages are sent from a transmitter to a receiver to inform the receiver of the coding rate implemented at any given point in time. These parameters may be adjusted independent of transmitted power level through the expedient of ensuring that size of a transmitted frame remains constant, while permitting the ability to change FEC coding rates and FEC block sizes.

主权项

1. A subscriber unit comprising:
a forward error correction (FEC) encoder configured to encode a plurality of frames, each of the plurality of frames including a variable number of data bits, to include an error correction code such that a resulting number of output symbols remains fixed; a modulator configured to modulate the output symbols; wherein the error correction code is selected based on a channel condition associated with the subscriber unit; wherein the FEC encoder is configured to produce a fixed number of output FEC symbols in each given transmitted frame; wherein the plurality of frames vary in pre-encoded bit size depending upon the error correction code selected at any given time by the FEC encoder and wherein the fixed number of output FEC symbols is produced by the FEC encoder for any error correction code selected, FEC coding rate, power level, symbol modulation type, or any combination thereof; and wherein different FEC coding rates, symbol rates, and FEC codes are assignable to each of a plurality of user channels depending on channel conditions without changing an effective transmitted power level.