The large spectrum available in the millimeter- Wave (mmWave) band has emerged as a promising solution for meeting the huge capacity requirements of the 5th generation (5G) wireless networks. However, to fully harness the potential of mmWave communications, obstacles such as severe path loss, channel sparsity and hardware complexity should be overcome. In this paper, we introduce a generalized reconfigurable antenna multiple-input multiple-output (MIMO) architecture that takes advantage of lens-based reconfigurable antennas. The considered antennas can support multiple radiation patterns simultaneously by using a single RF chain. The degrees of freedom provided by the reconfigurable antennas are used to, first, combat channel sparsity in MIMO mmWave systems. Further, to suppress high path loss and shadowing at mmWave frequencies, we use a rate- one space-time block code. Our analysis and simulations show that the proposed reconfigurable MIMO architecture achieves full-diversity gain by using linear receivers and without requiring channel state information at the transmitter. Moreover, simulations show that the proposed architecture outperforms traditional MIMO transmission schemes in mmWave channel settings.

In this paper, we investigate a trellis-coded space shift keying modulation scheme, called trellis-coded space-time shift keying (TC-STSK), which combines trellis-coded modulation with space shift keying. By analyzing the rank criterion using a graph theoretic approach, we maximize the number of unique differences between pairwise codewords as the code design goal. We discuss the code design principles for achieving diversity, and propose a design algorithm that is mostly suitable for rate-1/n codes, where n is the number of the code output bits. We then propose a diversity adaptation mechanism by selecting only the codewords with desired diversity, and use it to design higher rate codes that achieve full diversity. We also provide the code designs and a modified soft Viterbi decoder for such schemes. Simulation results show that the proposed scheme can achieve diversity orders expected from the theoretical analysis, and that increasing the number of shift registers and transmit antennas improves the performance of the TC-STSK scheme. The results also show that TC-STSK outperforms a space-time trellis code with the same bit rate and the number of shift registers.