Resource-Efficient Digital Communications: Research and Testbed Development in Support of Future Force Warrior and Joint Tactical Radio Systems

Abstract : This report describes the design and simulation of a bandwidth-efficient waveform suitable for the SLICE radio developed by ITT Aerospace/Communications; this waveform uses quadrature amplitude modulation (QAM) and low-complexity turbo codes developed at Notre Dame. The result is compared with another using continuous phase modulation (CPM). It is shown that the amplifier backoff required for QAM puts it at a disadvantage to CPM at spectral efficiencies where both are feasible - below 2.0 bits/sec/Hz. However, signal processing techniques (e.g. pre-distortion filtering) for QAM can reduce that disadvantage; moreover, at higher spectral efficiencies, QAM may be the only feasible solution. Other topics include low-density parity check (LDPC) convolutional codes, new techniques to reduce the peak to average power ratio (PAPR) for QPSK signals, and analysis of systems employing adaptive modulation and orthogonal frequency division multiplexing (OFDM).