Differential detection of quadrature frequency phase modulated signals

This paper proposes a pilot-symbol-assisted (PSA) signaling format that ena bles the differential detection of the differentially phase-encoded quadrat ure frequency/phase modulated (NDQFPM) signal using N orthogonal frequencie s. The PSA-NDQFPM signal is transmitted on a frame-by-frame structure. The channel considered is an additive white Gaussian noise channel where the ch annel phase varies so slowly that it is assumed constant over one frame dur ation, Each frame consists of J NQFPM pilot symbols and I data blocks, each containing L NDQFPM symbols, with the first symbol differentially phase en coded with respect to pilot symbols, Based on the maximum likelihood sequen ce estimation principle, the maximum-likelihood differential-detection (ML- DD) algorithm is developed to detect the PSA-NDQFPM signal on a block-by-bl ock basis, Tight upper and asymptotic bounds are derived and verified by si mulation to evaluate the bit error performance of the ML-DD algorithm, Both bandwidth and power efficiencies of PSA-NDQFPM with ML-DD are compared to NQFPM with coherent detection, constant-envelope NQFPM with coherent detect ion, constant-envelope NDQFPM (also known as NFSK/4DPSK) with ML-DD, and co nventional 2DQFPM (also known as DQ(2)PSK) with ML-DD, It is analytically s hown that PSA-NDQFPM with ML DD has lower power efficiency than NQFPM with coherent detection and NFSK/4DPSK with ML-DD, but still can provide noticea bly higher power efficiency than DQ(2)PSK with ML-DD when a medium frame le ngth is used, Due to the use of pilot symbols, PSA-NDQFPM with a medium fra me length has marginally lower bandwidth efficiency than its coherent count erpart NQFPM, but still yields significantly higher bandwidth efficiency th an constant-envelope NQFPM and NFSK/4DPSK.