Monitoring and equalization of in-service QPSK/TDMA links by means of burst-mode channel impulse response measurement

This paper presents a novel method for passive baseband-to-baseband channel frequency response measurement, suitable for the incremental commissioning and in-service monitoring of links in a QPSK/TDMA system. The method applies least squares estimation techniques to samples of the I and Q baseband components of received traffic bursts in order to derive a linear equivalent model for the satellite channel. Results obtained by computer simulation of an Intelsat V channel demonstrate that the method can provide a better basis for equalizing a nonlinear channel than the frequency response measurements provided by conventional techniques. A mathematical formulation and an implementation overview are also given.