Differential Space-Time-Frequency Codes for MB-OFDM UWB with Dual Carrier Modulation

In a multiple-input multiple-output (MIMO) multiband orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) system, coherent detection where the channel state information (CSI) is assumed to be exactly known at the receiver requires the transmission of a large number of symbols for channel estimation, thus reducing the bandwidth efficiency. This paper examines the use of unitary differential space-time frequency codes (DSTFCs) in MB-OFDM UWB, which increases the system bandwidth efficiency due to the fact that no CSI is required for differential detection. The proposed DSTFC MB-OFDM system would be useful when the transmission of multiple channel estimation symbols is impractical or uneconomical. Simulation results show that the application of DSTFCs associated with dual carrier modulation (DCM) can significantly improve the bit error performance of conventional differential MB-OFDM system (without MIMO), and even provide better bit error performance than the DSTFC MB-OFDM system associated with constant envelope modulation schemes.