Cooperative Symbol-Based Signaling for Networks with Multiple Relays

Wireless channels suffer from severe inherent impairments and hence reliable and high data rate wireless transmission is particularly challenging to achieve. Fortunately, using multiple antennae improves performance in wireless transmission by providing space diversity, spatial multiplexing, and power gains. However, in wireless ad-hoc networks multiple antennae may not be acceptable due to limitations in size, cost, and hardware complexity. As a result, cooperative relaying strategies have attracted considerable attention because of their abilities to take advantage of multi-antenna by using multiple single-antenna relays. This study is to explore cooperative signaling for different relay networks, such as multi-hop relay networks formed by multiple single-antenna relays and multi-stage relay networks formed by multiple relaying stages with each stage holding several single-antenna relays. The main contribution of this study is the development of a new relaying scheme for networks using symbol-level modulation, such as binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK). We also analyze effects of this newly developed scheme when it is used with space-time coding in a multi-stage relay network. Simulation results demonstrate that the new scheme outperforms previously proposed schemes: amplify-and-forward (AF) scheme and decode-and-forward (DF) scheme

Multi-Antenna Assisted Virtual Full-Duplex Relaying with Reliability-Aware Iterative Decoding

In this paper, a multi-antenna assisted virtual full-duplex (FD) relaying with reliability-aware iterative decoding at destination node is proposed to improve system spectral efficiency and reliability. This scheme enables two half-duplex relay nodes, mimicked as FD relaying, to alternatively serve as transmitter and receiver to relay their decoded data signals regardless the decoding errors, meanwhile, cancel the inter-relay interference with QR-decomposition. Then, by deploying the reliability-aware iterative detection/decoding process, destination node can efficiently mitigate inter-frame interference and error propagation effect at the same time. Simulation results show that, without extra cost of time delay and signalling overhead, our proposed scheme outperforms the conventional selective decode-and-forward (S-DF) relaying schemes, such as cyclic redundancy check based S-DF relaying and threshold based S-DF relaying, by up to 8 dB in terms of bit-error-rate.Comment: 6 pages, 4 figures, conference paper has been submitte

Maximum Euclidean distance network coded modulation for asymmetric decode-and-forward two-way relaying

Network coding (NC) compresses two traffic flows with the aid of low-complexity algebraic operations, hence holds the potential of significantly improving both the efficiency of wireless two-way relaying, where each receiver is collocated with a transmitter and hence has prior knowledge of the message intended for the distant receiver. In this contribution, network coded modulation (NCM) is proposed for jointly performing NC and modulation. As in classic coded modulation, the Euclidean distance between the symbols is maximised, hence the symbol error probability is minimised. Specifically, the authors first propose set-partitioning-based NCM as an universal concept which can be combined with arbitrary constellations. Then the authors conceive practical phase-shift keying/quadrature amplitude modulation (PSK/QAM) NCM schemes, referred to as network coded PSK/QAM, based on modulo addition of the normalised phase/amplitude. To achieve a spatial diversity gain at a low complexity, a NC oriented maximum ratio combining scheme is proposed for combining the network coded signal and the original signal of the source. An adaptive NCM is also proposed to maximise the throughput while guaranteeing a target bit error probability (BEP). Both theoretical performance analysis and simulations demonstrate that the proposed NCM can achieve at least 3 dB signal-to-noise ratio gain and two times diversity gain

Spectrally Efficient Cooperative Relay Networks using Signal Space Diversity

Cooperative relaying has received widespread attention in recent years from both academic and industrial communities. It offers significant benefits in enabling connectivity as well as in increasing coverage, power saving, spatial diversity and channel capacity. However, one of the main limitations of the conventional cooperative relaying system is the repetition of the received data by the relays, which reduces the spectral efficiency and the data rate. In this thesis, signal space diversity (SSD) based technique is proposed to incorporate into the conventional relaying system to enhance spectral efficiency, data rate and system performance. Firstly, SSD is introduced into a two-way cooperative relaying system with three-phase two-way decode-and-forward (DF) protocol. In this system, four symbols are exchanged in three time slots, thereby doubling the spectral efficiency and the data rate compared to the conventional three-phase two-way DF relaying system that uses six time slots to exchange the same four symbols. Next, SSD is employed in a dual-hop relaying system using DF protocol without a direct link between the source and the destination. In this system, two symbols are transmitted in three time slots as compared to four time slots to transmit the same two symbols in the conventional dual-hop DF relaying system. These proposed systems are designed to exploit the inherent diversity in the modulation signal-space by rotating and expanding the ordinary constellation. The improvement in spectral efficiency is achieved without adding extra complexity, bandwidth or transmit power. A comprehensive analysis of these proposed systems is carried out over Rayleigh fading channels, and closed-form expressions for various performance metrics, including error probability, outage probability and channel capacity, are derived and illustrated. An asymptotic approximation for the error probability is obtained and is used to illustrate the impact of system parameters and diversity gain on the system performance. The optimization of relay location and power allocation in these systems is also examined. Extensive Monte Carlo simulations are performed to ascertain the accuracy of the analytical results presented in the thesis. Indeed, it is observed that the use of SSD in cooperative relaying can play a major role in the system design and performance improvement