Fast detection algorithm based on sphere decoding for Overlapped Hybrid Division Multiplexing system

The overlapped time-frequency two dimensional multiplexing system (OvHDM, Overlapped Hybrid Division Multiplexing) can significantly improve the spectrum efficiency of communication system. The system can be described as a vector convolutional encoding constraint model and the optimum detection algorithm is maximum likelihood sequence detection (MLSD), but the algorithm causes large detection delay due to high complexity. In this paper, a mathematic model similar to MIMO system is derived for OvHDM system and sphere decoding algorithm is applied to fast detect the received signal. Simulation results show that the algorithm based on sphere decoding obtains the same performance of the optimum detection but the computational complexity is significantly reduced. The performance of OvHDM system is better than that of QAM modulation with the same spectrum efficiency at a high signal to noise ratio. This shows that improving the transmission rate with overlapped signals can achieve greater gains than using high-order QAM modulation with the same spectrum efficiency.