Constant envelope space-time modems

This paper shows that under certain scenarios continuous phase modulation (CPM) is an attractive option for space-time modem implementations. CPM is attractive in the sense that nonlinear power amplifiers can be used to reduce the cost of individual transmitters. However, receiver complexity and bandwidth inefficiency have reduced the utility of CPM in single transmit antenna scenarios. We would show that in a multiple transmit antenna scenario CPM modulation can reduce the cost of individual transmitters and while still achieving the multiple antenna throughput advantage. A constrained outage capacity analysis is completed and the results show that if outage probability is the design constraint then using CPM results in little loss in terms of the achievable rate and performance. CPM, like linear modulations, can achieve a tradeoff between rate and performance, and this paper examines some of the signaling options available for CPM in multiple antenna modems.