Enhanced Multiple-Bit Differential Detection of DOQPSK

In this paper, we consider multiple-bit differential detection (MBDD) of differential offset quadrature phase-shift keying (DOQPSK) with conventional bit-wise differential encoding (DE). We propose two novel MBDD schemes that outperform Simon\´s MBDD and approach the performance of coherent detection (CD) as the observation window size increases. The first scheme uses the full available detection window spanning bit intervals, and is referred to as F-MBDD. A careful bit-error rate (BER) analysis shows that a significant performance improvement can be realized by reducing the detection window size to -bit intervals. The resulting improved MBDD (I of DOQPSK with bit-wise DE achieves a similar performance as Phoel\´s MBDD of DOQPSK with more complex symbol-wise DE. For both F-MBDD and I, tight upper bounds and accurate BER approximations are derived. In addition, since the complexity per bit decision of brute-force decoding of MBDD of DOQPSK grows exponentially with , we develop optimum and suboptimum fast decoding algorithms with complexities per bit decision of orders and , respectively.