MIMO-OFDM systems aim to improve transmission quality and/or throughput but require significant signal processing capability and flexibility at reasonable cost. This paper proposes a reconfigurable architecture and associated algorithm optimizations for these types of systems based on the IEEE 802.11n and IEEE 802.16e standards. In particular, we describe the implementation of two key computations onto this architecture, namely Fast Fourier Transform (FFT) and Space-Time Block Decoding (STBD). The design is post-layout using a UMC 0.18 micron technology at a clock rate of 100 MHz. Performance comparisons with other optimization methods and hardware implementations are given.

Switch-and-stay combining (SSC) is a simple diversity technique where a single radio frequency (RF) chain is connected to one of several antenna branches and stays there if the channel quality is satisfied or otherwise switches to a new branch. Compared with Selection Combining (SC), SSC requires less overhead in channel estimation and antenna selection feedback. In this paper, we analyze the performance of SSC in a time-correlated flat fading channel and with causal channel state information. We derive the general expressions for the distribution of the output signal-to-noise ratio (SNR), outage rate and average bit error rate (ABER) and then the analytical results are compared with the simulation results under the Jakes Rayleigh fading channel. Our results show that (1) For slowly varying channels, L branch SSC can achieve the full diversity order and the same outage rate as SC; (2) Increasing the number of antenna branches can improve the performance of SSC, however, the gain from adding antennas diminishes quickly as the channel variation speed increases. Moreover, to avoid the complexity in optimizing the fixed threshold, we also propose a simple adaptive SSC scheme which has almost the same ABER as the SSC with optimized fixed threshold.