Coded Bit-Interleaved and Antenna-Switched Modulation with Iterative Decoding

In this paper, a novel method to achieve transmitter diversity and improved coding gain in a bit-interleaved coded modulation (BICM) system is proposed. Information bits are first channel-coded and punctured to match the desired data rate. The survived bits after puncturing are then interleaved and mapped to QAM modulation symbols. Bit level interleaving achieves maximum temporal (with time domain interleaving) or frequency (with frequency domain interleaving) diversity provided by channel coding with given constrained length and code rate. The QAM symbols are finally up-converted into RF and transmitted over one of multiple antennas. Unlike the conventional methods where punctured bits (often referred to as stolen bits) are discarded, we use stolen bits for antenna selection, where information of the stolen bits are embedded in the antenna selection itself. This arrangement can be viewed as a serially concatenated code, with stolen bit controlled antenna selection being the inner code and error correcting channel code being the outer code. A standard iterative (turbo) receiver is then adapted for demodulation, which consists of a soft-in-soft-out (SISO) demapper and a SISO decoder. The SISO demapper and SISO decoder exchange extrinsic information during each iteration as a standard turbo decoder does. Reliability of stolen bits and transmitted bits improves after each iteration, and the decoding process converges after several iterations. The performance of the proposed scheme is evaluated using a "genie aided" upper bound and it is found that the diversity order equals the Hamming distance of a less-punctured code. When compared to a bit-interleaved space-time code (BI-STC), the proposed scheme performs approximately 2 to 2.5 dB better at a 1% frame error rate.