A significant problem in the tracking of multiple user channels is described for a receiver that implements joint demodulation. It is observed that channel switching, where a channel tracker mixes the channels of multiple co-channel signals, degrades the performance of the receiver for medium to high speed mobiles. When a channel switch occurs, the channels of the users are tracked well, but channels are assigned to the wrong users. Consequently, from that point on all the detected symbols for a user of interest are incorrect, since they belong to another user. The tolerance of various channel tracking algorithms to this channel switching problem is discussed. The performance of the joint channel trackers is evaluated along with joint demodulation of co-channel signals for IS-136 mobiles.
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