then transmitted from the corresponding antennas. The antenna-to-stream mapping remains static over time. The spatial rate is min(N, and the overall signaling rate is Immdulation-order min(N,), where rb is the channel coder input bit rate and Immodulation-order denotes the QAM modulation order. The HE scheme can at most achieve N order diversity, since any given information bit is transmitted from only one transmit antenna and received by N receive antennas. While this is a source of sub-optimality of the HE architecture, it does simplify receiver design. The coding gain achieved by HE depends on the coding gain of the temporal code. Furthermore, a maximum array gain of N1 can be realized using the HE scheme. In the VE architecture, the bitstream undergoes temporal encoding, symbol mapping, and interleaving after which it is de-multiplexed into min(Nt,Nr) streams transmitted from the individual antennas. This form of encoding can achieve full N X Nr order diversity, provided that the temporal code is properly designed, since each information bit can be spread across all the transmit antennas. Nevertheless, the VE scheme requires joint decoding of the sub-streams, which increases receiver implementation complexity compared to an HE scheme where the individual data streams can be decoded separately. The spatial rate of VE is min(N, and the overall signaling rate is min(N,. The coding gain achieved by VE will depend on the temporal channel coding characteristic and a maximum array gain of N1 can be achieved. Space-Frequency Block Codes (SFBC) is the frequency-domain version of the Space-Time Block Codes (STBC). This family of codes is designed to achieve diversity gain by transmitting orthogonal streams which yield optimal SNR with a linear receiver. Since in the OFDMA systems, the number of OFDM symbols in a subframe may often be an odd number, while STBC (e.g., Alamouti codes) operates on pairs of adjacent symbols in the time-domain, the application of STBC would not be straightforward. For SFBC transmission, the 