Design and implementation of a preamble-based burst mode CPM modem over Rayleigh fading channels

Abstract

This paper discusses the design and implementation of a burst mode Continuous Phase Modulation (CPM) modem over flat, Rayleigh fading channels in the 220MHz frequency band. Our design focused on bandwidth efficiency while maintaining good synchronization performance and low complexity. The designed preamble is based on the combination of Minimum Shift Keying (MSK) signals and 3RC (Raised Cosine) signals. The use of MSK allows a closed form result for an initial Maximum Likelihood (ML) timing estimate. The 3RC signal, which has a better timing characteristic than MSK, is used to refine the timing and frequency estimates. The payload uses 3RC signals. Pilot symbol assisted modulation (PSAM) is used to assist channel estimation. The designed packet structure meets the Federal Communications Commission (FCC) frequency emission mask for 220MHz frequency band. A CPM modem using the designed packet structure has been implemented on the testbed and the simulation, bench test, and field test results are presented in this paper.