Keywords

continuous phase modulation, noncoherent detection

Abstract

This work was supported under a grant from the Air Force ARTM program (Contracts F04700-02-P-0080 and F04700-02-P-0081). It is well understood that the performance of noncoherent receivers with multi-symbol observation intervals approaches that of coherent receivers as the observation interval grows arbitrarily large. However, since complexity also grows exponentially with observation length, there are practical limits to this approach. In this paper we present a noncoherent receiver for continuous phase modulation (CPM) whose structure is a hybrid between existing coherent and noncoherent receiver architectures. The presentation is given in the most general M-ary multi-h terms, with some emphasis on the special and popular case of single-h CPM. The receiver has a multi-symbol observation parameter similar to that of existing noncoherent receivers. However, it uses a recursive metric similar to that of the optimal coherent receiver, which allows it to use much smaller values of the multi-symbol observation parameter thus reducing the required complexity. We analyze the performance of this receiver over the noncoherent additive white Gaussian noise (AWGN) channel and derive a union bound on the bit error probability. We confirm the usefulness of the bound with computer simulations. We also give thorough examples using quaternary raised cosine (RC) single- and multi-h CPM schemes. With these examples we show that previous noncoherent CPM techniques extend to the general multi-h case. The simulations also show that the proposed receiver outperforms these other noncoherent techniques, at a fraction of the complexity.