Pre-processed space-time trellis codes

Tarokh et al. (1998) introduced the concept of space-time trellis coding as a means to combat fading by introducing redundancy, both in space and time. If the wireless channels are static or fade very slowly, the channel state information can be sent back to the transmitter using a low bit rate feedback path. In such a situation, it may be possible to mitigate the effects of signal cancellation due to simultaneous transmission, by using some sort of pre-processing technique at the transmitter (which incorporates the channel knowledge). However, we assume that no such feedback channel exists. Therefore, we address the issue of feedforward only pre-processing schemes at the transmitter. For fading channels, the error-rate performance depends on the effective code length, which is the length of the shortest error event path. The performance also depends on the minimum product distance which is computed from the maximum likelihood path and the other error paths with non-zero distance from it.