A novel 4 x 1 scheme of transmitting two real orthogonal space-time block codes (O-STBC) on the I- and Q-channels with pulse-shaped offset QAM has recently been proposed. In order to achieve good spectral confinement, a pulse shape that introduces a small amount of controlled interference between I/Q- channels is used for the offset QAM signal. In this paper, two-real- symbol joint decoding is investigated for the scheme. This joint decoding can outperform the single-real symbol decoding proposed previously and the best-performing quasi-orthogonal space-time block code (QO-STBC) by more than 1 dB at bit error probability of 10-5when the interference introduced by the pulse shape is relatively large.

A new 4times1 scheme of transmitting two real orthogonal space-time block codes (O-STBC) on the I- and Q-channels with pulse-shaped offset QAM is proposed. This scheme achieves full rate and employs simple real-symbol-wise decoding. Two families of pulse shapes for the offset QAM signal are considered: i) pulse shapes with zero cross-channel interference (CCI) between I/Q-channels and ii) pulse shapes with controlled CCI. In the zero CCI case, the real-symbol-wise decoding is optimum and the bit error probability (BEP) performance is better than that of conventional full-rate, full-diversity quasi-orthogonal space-time block codes (QO-STBC), as well as rate-1/2 and rate-3/4 complex O-STBCs. To achieve good spectral confinement while maintaining decoding simplicity, we investigate pulse shapes that introduce a small amount of controlled CCI at the sampling instants so that some performance gains can be traded off. We derive a BEP upperbound for the case of nonzero CCI and formulate the design criteria on how to construct the two real O-STBCs on the I/Q channels in order to minimize the performance degradation caused by the controlled CCI. The optimum real O-STBCs are then identified and their BEP performance is compared with that of the benchmark schemes.

In this paper, we show, in both theory and simulation, that by transmitting two real orthogonal space-time block codes (O-STBC) on the I- and Q-channels with pulse-shaped offset QAM, we are able to achieve full rate transmit diversity for a 4 times 1 system with very simple "half-symbol" detection, i.e., the real I- and Q-symbols can be separately decoded. For this scheme, two families of pulse shapes of the offset QAM signal are considered: i) pulse shapes with zero inter-symbol interference (ISI) and ii) pulse shapes with controlled ISI between the I- and Q-channels. In the zero ISI case, the half-symbol decoding is optimum in the maximum likelihood sense and the system is able to achieve full transmit diversity. The associated bit error probability (BEP) performance is better than that of conventional full-rate, full-diversity quasi-orthogonal space-time block codes (QO-STBC), as well as rate-1/2 and rate-3/4 complex O-STBCs. To achieve good spectral confinement while maintaining decoding simplicity, we investigate pulse shape design techniques so that some performance gains can be traded off by introducing a controlled small amount of ISI at the sampling instants. We also extend the analysis to a 4 times 4 multiple-input multiple-output (MIMO) system, and derive the design criteria on how to construct the two real O-STBCs in order to minimize the performance degradation caused by the controlled ISI

A closed-form formula for symbol-error rate (SER) of an orthogonal frequency-division multiplexing (OFDM) system with M-ary differential phase-shift keying (MDPSK) in frequency domain over Rayleigh fading channels is obtained. It is found that, by MDPSK in frequency domain, identical SERs can be achieved on all subcarriers. However, both time and frequency dispersion in the channel will introduce error floors. A comparison between OFDM-MDPSK in frequency domain and that in time domain reveals that the former system offers superior SER performance in a fast fading environment, while the latter performs better if the channel is mainly frequency selective. Moreover, the former system has lower implementation complexity.