Transceiver design for millimetre-wave communications: a space-time-frequency multi-functional processing approach

In this thesis, we investigate a suite of transceiver designs for transmission over millimetre wave (mmWave) channels. Furthermore, we conceive the philosophy of Layered Multi-Group (LMG) arrangements relying on the concept of Multi-Functional Multiple- Input Multi-Output (MF-MIMO) systems. More specifically, we propose an amalgam of various MIMO techniques, namely diversity, multiplexing and beamforming techniques as well as Multi-User MIMO (MU-MIMO), user grouping and antenna layering methods, which are capable of simultaneously gleaning various MIMO advantages for the sake of overcoming the unfavourable propagation characteristics of mmWave signals. The mm- Wave channel suffers both from high path loss and sparse scattering, which results in reduced receiver diversity.To mitigate these problems, we propose the LMG Steered Space-Time Shift Keying (LMG-SSTSK) system. More specifically, the LMG-SSTSK system is capable of achieving an enhanced multiplexing gain and an improved diversity gain by relying on STSK, and a beamforming gain with the aid of analogue beamforming. Additionally, LMG-SSTSK is capable of supporting multi-user communication using MU Transmit Precoding (MUTPC) as well as an increased number of served users with the aid of sophisticated antenna layering and user grouping. We opt for STSK as the main transmission scheme, since it is an MF-MIMO, which is capable striking a design trade-off between the achievable throughput and the attainable diversity gain. Additionally, the system employs Orthogonal Frequency-Division Multiplexing (OFDM) for transmitting over the mmWave wideband channel, which imposes frequency selective fading due to its high bandwidth, where time dispersion is imposed by the delay of the sparse multipath components. The above-mentioned antenna grouping and user grouping concepts were introduced into the LMG-SSTSK system in order to overcome the restrictions imposed by the mmWave channel in MU scenarios, where due to the high path loss and the beamforming employed, the system cannot simultaneously support angularly dispersed users. Hence, the users are partitioned into groups and the proposed MF-MIMO communicates with all users by conceiving antenna layering.On the other hand, in order to enhance the LMG-SSTSK’s achievable throughput, we propose the novel Multi-Set Space-Time Shift Keying (MS-STSK) scheme. The MSSTSK system constitutes an improved version of STSK and has the potential of outperforming other MIMO arrangements by appropriately choosing the MS-STSK’s parameters. In MS-STSK, a single dispersion matrix is activated using a classical PSK/QAM symbol and transmitted by activating a single Antenna Combination (AC), where an AC is defined as a unique set of multiple antenna elements out of those available at the transmitter. The achievable throughput of MS-STSK depends on the AC allocation technique employed. Hence, the Distinct Antenna Allocation (DAC) technique and the Shared Antenna Allocation (SAC) technique are conceived. The DAC technique requires a distinct set of antenna elements in each antenna combination, while the antenna elements are shared among the available ACs with the aid of SAC, hence MS-STSK associated with DAC achieves an enhanced performance at the cost of a reduced throughput compared to its SAC counterpart, which strikes a design trade-off between them. Furthermore, in order to transmit over the mmWave channel, we intrinsically amalgamate both OFDM and analogue beamforming with MS-STSK using our OFDM-aided MS-STSK system, leading to our OFDM-MS-STSK system. We further exploit the frequency dimension for enhancing the achievable throughput of the OFMD-aided MS-STSK system by introducing the Multi-Space-Frequency STSK (MSF-STSK) system. Accordingly, we introduce our MU Steered MS-STSK (MU-SMS-STSK) system by employing MU-TPC in OFDMMS- STSK for simultaneously supporting multiple users. Finally, to mitigate the angular selectivity of the beamforming-aided mmWave channel, we reintroduce the LMG structure in the LMG-SMS-STSK arrangement. Additionally, in order to achieve near-capacity performance using the classical MSSTSK scheme, we conceive a serially-concatenated channel coding assisted MS-STSK scheme. More specifically, we devise a soft-decision-aided MS-STSK decoder associated with an iterative two-stage serially-concatenated inner detector and outer decoder, which is designed by relying on EXtrinsic Information Transfer (EXIT) charts. Finally, in order to transmit over the mmWave channel, our soft-decision-aided scheme is combined with wideband techniques, such as OFDM and Single-Carrier Frequency Division Equalisation (SC-FDE), as well as beamforming, where due to the DFT and IDFT mismatch introduced by OFDM, we opt for SC-FDE to retain the advantage of MS-STSK having to rely on a reduced number of RF-chains