Pulse rotation modulations for spread spectrum communication systems

Spread spectrum communication systems excel in their ability to provide enhanced security and channel sharing, yet they do so at the expense of data throughput provided to each individual user. This paper introduces an alternative modulation mechanism, pulse rotation modulation (PRM), for increasing the data throughput in wideband direct sequence or chaotic sequence code-based spread spectrum systems. The result employs a temporal rotation of the spread pulse within its own symbol duration, leading to higher data throughputs that can be throttled up/down as the channel and multiple access conditions permit. Challenges with signal synchronization, code orthogonality, and carrier-induced phase rotations/phase noise are discussed. A predictive model of receiver performance is validated with simulated AWGN-channel results; both are based on extrapolations from a measured hardware prototype that has implemented a small scale example of the PRM technique.