Initial synchronisation of wideband and UWB direct sequence systems: single- and multiple-antenna aided solutions

This survey guides the reader through the open literature on the principle of initial synchronisation in single-antenna-assisted single- and multi-carrier Code Division Multiple Access (CDMA) as well as Direct Sequence-Ultra WideBand (DS-UWB) systems, with special emphasis on the DownLink (DL). There is a paucity of up-to-date surveys and review articles on initial synchronization solutions for MIMO-aided and cooperative systems - even though there is a plethora of papers on both MIMOs and on cooperative systems, which assume perfect synchronization. Hence this paper aims to ?ll the related gap in the literature

Synchronisation Issues in Non-coherent MIMO Systems

In this article, we identify some of the key problems that may be encountered when designing Non-Coherent (NC) Multiple-Input Multiple-Output (MIMO) DownLink (DL) synchronisation schemes for communicating over multi-path fading channels. Our main objectives are to illustrate the information theoretic features and to provide design guidelines for the initial synchronisation of NC MIMO systems. We conclude by outlining the relationships between the beneficial and detrimental design factors

Multi-set space-time shift keying and space-frequency space-time shift keying for millimeter-wave communications

In this paper, we introduce a novel OFDM-aided multifunctional multiple-input multiple-output scheme based on multi-set space-time shift keying (MS-STSK), where the information transmitted over each subcarrier is divided into two parts: STSK codeword and the implicit antenna combination (AC) index. In MS-STSK, a unique combination of antennas can be activated at each subcarrier to convey extra information over the AC index while additionally transmitting the STSK codeword. Furthermore, inspired by the MS-STSK concept, this scheme is extended also to the frequency domain in the novel context of our multi-space-frequency STSK (MSF-STSK), where the total number of subcarriers is partitioned into blocks to implicitly carry the block's frequency index. The proposed MSF-STSK scheme benefits from the huge bandwidths available at mmWaves for partitioning the total number of OFDM subcarriers into blocks to convey more information over the frequency domain. Both proposed systems use STSK codewords as the basic transmission block, and they can achieve higher data throughput and better BER performance than STSK. Moreover, given that the system is meant to operate at mmWaves, antenna arrays relying on several antenna elements are employed at both the transmitter and receiver for analogue beamforming with the aid of phase shifters and power amplifiers to overcome the effect of high path loss

Layered multi-group steered space-time shift-keying for millimeter-wave communications

We propose a novel multi-user Multiple-Input Multiple-Output (MIMO) technique termed as the Layered Multi-Group Steered Space-Time Shift Keying (LMG-SSTSK) for the downlink of millimeter wave (mmWave) communications, which combines the concepts of Multi-User MIMO (MU-MIMO), Space-Time Shift Keying (STSK), beamforming and Orthogonal Frequency-Division Multiplexing (OFDM) to simultaneously convey information to multiple users. The LMG-SSTSK tackles the propagation challenges of the high-attenuation mmWave frequencies by sub-dividing the users into multiple groups. The proposed system allows more users to be served simultaneously in the downlink over the same time-and frequency-resources than a system dispensing with the proposed grouping technique

Multi-set space-time shift-keying with reduced detection complexity

In this treatise, we propose a novel Multi-Set Space-Time Shift Keying (MS-STSK) technique, where the source bits are conveyed over two components, namely by activating one out of MQ dispersion matrices of Space-Time Shift Keying (STSK) and M Antenna Combination (AC) of the Nt available antennas, in a similar fashion to Spatial Modulation (SM) but activating multiple antennas rather than a single antenna. This system requires a smaller number of RF chains than Antenna Elements (AEs) to achieve an improved throughput. We opt for STSK as the main building block of our proposed MS-STSK as a benefit of its design flexibility, where STSK is capable of providing the system with both diversity and multiplexing gains. The proposed MS-STSK system achieves both higher data rates and a lower Bit Error Rate (BER) than the conventional STSK scheme, which is attained at the cost of increased number of antenna elements and a high-speed antenna switch. Furthermore, as the symbol rate of the MS-STSK system increases, its performance compared to the STSK scheme is significantly improved, because of the enhanced diversity introduced by the additional antenna elements. Furthermore, we propose a reduced complexity detector for QAM/PSK constellations, which - despite its reduced complexity - is capable of achieving the same performance as the optimal Maximum Likelihood (ML) detector

Multi-user steered multi-set space-time shift-keying for millimeter-wave communications

The recently proposed concept of multiset space-time shift keying (MS-STSK) is intrinsically amalgamated with the multiple-input multiple-output (MIMO) philosophy for the sake of enhancing the attainable system throughput. Explicitly, we propose a multiuser steered MS-STSK (MU-SMS-STSK) scheme for the downlink of millimeter-wave (mmWave) communications, which is combined with analogue beamforming (BF) that relies on phase shifters and power amplifiers to overcome the high attenuation of mmWaves. Hence, our MU-SMS-STSK system combines the concepts of MU-MIMO, MS-STSK, BF, and orthogonal frequency-division multiplexing for communicating with multiple users relying on the same time and frequency resources