Joint impulse response shortening

Abstract

In discrete multitone (DMT) transceivers an intelligent guard time sequence, called a cyclic prefix, is inserted between symbols to ensure that samples from one symbol do not interfere with the samples of another symbol. The length of the cyclic prefix is determined by the length of the impulse response of the effective physical channel. Using a long cyclic prefix reduces the throughput of the transceiver. To avoid using a long cyclic prefix, a short time-domain FIR filter is used to shorten the effective channel's impulse response. In full duplex transceivers echo cancellation may be required. The complexity of the echo canceller is directly related to the length of the echo path. This paper explores a joint shortening approach for determining the coefficients for this time-domain filter to jointly shorten both the channel and echo path impulse responses.