On distributed space-time coding techniques for cooperative wireless networks and their sensitivity to frequency offsets

The application of distributed space-time coding schemes in a simulcast network is considered and a key challenge is addressed which arises in the downlink: since the local oscillators employed at the individual transmitting nodes may independently differ from the nominal carrier frequency, frequency offsets will occur between the individual transmission signals. The influence of these frequency offsets on the performance of a specific distributed space-time coding scheme is investigated and both simulative and analytical results are presented. Appropriate receiver-sided counter measures are considered and possibilities are discussed to estimate the occurring frequency offsets at the receiver.