Predictive relay-selection cooperative diversity in land mobile satellite systems

Cooperative diversity protocols promise a new dimension of diversity that provides better communication by engaging nearby relays in forming a ‘virtual’ array of antennas for combined signal transmission. The current incremental cooperative diversity algorithms incrementally select best relay(s) to cooperate based on the channel quality reported by the relays. However, the algorithms do not take into consideration the fact that the chosen best relay(s) at estimation may not always be best at the time of communication. This is due to the time delay between the relay selection and its transmission of signal (problem of outdated Channel Quality Information). To solve this problem, the concept of channel prediction is introduced and employed whereby each relay determines a predicted value of its Channel Quality Information (CQI) based on its past measurements. The paper therefore develops a novel predictive relay-selection (PRS) cooperative diversity model which seeks to improve Land Mobile Satellite (LMS) communication through prediction protocols. In the model, the chosen best relay is the one with the best predicted CQI value instead of the traditional outdated one. Performance analysis of outage probability and average bit error probability for the newly developed PRS cooperation shows that the PRS cooperation is better than direct and outdated CQI relay communication.http://onlinelibrary.wiley.com/doi/10.1002/sat.11182017-03-31hb2016Electrical, Electronic and Computer Engineerin

Performance analysis of spatially-distributed cooperative networks

PhD ThesisApplications of cooperative communications have attracted considerable attention in academia and industry in the past decade for their potential to exploit network densi cation in meeting the growing demand for data services. However, analytical methods capable of explicitly capturing the impact of the spatial domain on system performance are still rare. The aim of this thesis is to study cooperation between spatially-distributed nodes with the purpose to enhance relevant analytical methods. New approaches to performance analysis of node cooperation and several useful relations are developed in this work in the following three areas. First part of this thesis investigates broadcasting as an important method for TV and network signalling distribution. Cooperative broadcasting (CB) has been generally studied under the assumptions of asymptotically dense or large networks, which rarely hold in practice. In this work, a method to analyse the latency of CB in nite networks is developed using stochastic geometry. New useful relations and inter-node distance distributions are derived, highlighting interesting network characteristics. Second part of this thesis studies relay selection (RS), recognised as a way to reduce overheads arising from cooperative communications. In this thesis, a method for analysing RS is developed based on point processes theory. Presented approach is simpler and more intuitive compared to known methods. This has allowed obtaining exact expressions for outage probability of relay-assisted communication. Additionally, analysis of the sources' contention for relays has revealed that relays can be treated as a scarce resource. Finally, proposed methods are further extended to account for imperfect channel state information (CSI). Practical RS in presence of CSI imperfections remains an active research area, however the aspect of cooperating nodes' spatial distribution remains unexplored. This thesis introduces a novel approach to account for variable levels of CSI accuracy and for the spatial distribution cooperating relays

Performance analysis of cooperative diversity in land mobile satellite systems.

Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2013.Land Mobile Satellite Systems (LMSS) generally differ from other terrestrial wireless systems. The LMSS exhibit unique characteristics with regard to the physical layer, interference scenarios, channel impairements, propagation delay, link characteristics, service coverage, user and satellite mobility etc. Terrestrial wireless systems have employed the spatial diversity or MIMO (Multiple Input Multiple Output) technique in addressing the problem of providing uninterrupted service delivery to all mobile users especially in places where non-Line-of-Sight (NLoS) condition is prevalent (e.g. urban and suburban environments). For the LMSS, cooperative diversity has been proposed as a valuable alternative to the spatial diversity technique since it does not require the deployment of additional antennas in order to mitigate the fading effects. The basis of cooperative diversity is to have a group of mobile terminals sharing their antennas in order to generate a “virtual” multiple antenna, thus obtaining the same effects as the conventional MIMO system. However, the available cooperative diversity schemes as employed are based on outdated channel quality information (CQI) which is impracticable for LMSS due to its peculiar characteristics and its particularly long propagation delay. The key objective of this work is therefore to develop a cooperative diversity technology model which is most appropriate for LMSS and also adequately mitigates the outdated CQI challenge. To achieve the objective, the feasibility of cooperative diversity for LMSS was first analyzed by employing an appropriate LMSS channel model. Then, a novel Predictive Relay Selection (PRS) cooperative diversity scheme for LMSS was developed which adequately captured the LMSS architecture. The PRS cooperative scheme developed employed prediction algorithms, namely linear prediction and pattern-matching prediction algorithms in determining the future CQI of the available relay terminals before choosing the most appropriate relay for cooperation. The performance of the PRS cooperative diversity scheme in terms of average output SNR, outage probability, average channel capacity and bit error probability were simulated, then numerically analyzed. The results of the PRS cooperative diversity model for LMSS developed not only showed the gains resulting from introducing cooperative techniques in satellite communications but also showed improvement over other cooperative techniques that based their relay selection cooperation on channels with outdated quality information (CQI). Finally, a comparison between the results obtained from the various predictive models considered was carried out and the best prediction model was recommended for the PRS cooperation