Equalization of TDMA links using in-service impulse response measurement

This paper describes a method of measuring the frequency response of a digital radio link given the received (modulated) message signal, suitable for the incremental commissioning and in-service monitoring of links in a QPSK/TDMA system. The method applied least squares estimation techniques to samples of the I and Q baseband components in order to derive a linear equivalent model for the channel. Results obtained by computer simulation of an INTELSAT V channel demonstrate that the method can provide a better basis for linear equalization of a non-linear channel than the frequency response measurements provided by conventional techniques. A mathematical formulation and an implementation overview are also given.