Training sequence based multiuser channel identification for cochannel interference cancellation in GSM

We address the problem of the joint identification of the channel impulse responses of almost-synchronous cochannel users. This problem arises in a cellular system using the time division multiple access (TDMA) scheme where the base stations are assumed to be synchronized and the radius of the cells is limited to a few kilometers. After the partial equalization of the transmit pulse shape filter which compensates for the intersymbol interference (ISI) introduced by the GMSK modulation (used in GSM), the receiver should detect the active training sequences by a synchronization step and then estimates the corresponding channel impulse responses by the standard least squares (LS) method. The spatio-temporal receiver used in our simulations for demodulating the signal of interest modeling the interferers as Gaussian colored noise is the interference cancelling matched filter (ICMF) which we introduced previously.