BER-Minimized Space-Time-Frequency Codes for MIMO Highly Frequency-Selective Block-Fading Channels

In this paper, we present bit error rate (BER)- minimized space-time-frequency (STF) block codes for multi- input multi-output (MIMO) highly frequency-selective block- fading channels. We consider the IEEE 802.15.3 a ultra-wide band (UWB) channel models (CM) 1-4. Based on a new STF block codes design criterion with the objective of minimizing BER, we develop an efficient searching algorithm for the design of the optimal STF block codes which maximize the coding gain. For 128 subcarriers with two subcarriers jointly encoding with 2-4 transmitting antennas, we find that the optimal STF block codes for all the IEEE 802.15.3 a UWB channel models CM 1-4 can be found. Furthermore, the designed STF block codes outperform the recently published high-rate full-diversity STF codes [1] by 1 dB. Last, the proposed STF codes can be decoded by maximum likelihood decoding approach, which is simpler than the sphere decoding principle used in [1]. Index Terms-Bit error rate (BER), block-fading channels, IEEE 802.15.3 a channel model, multi-input multi- output (MIMO), space-time-frequency (STF) block codes, ultra- wideband (UWB).