Mohammed W. Baidas

Many-to-many space-time network coding for amplify-and-forward cooperative networks: node selection and performance analysis

In this paper, the multinode amplify-and-forward cooperative communications for a network of N nodes is studied via the novel concept of many-to-many space-time network coding (M2M-STNC). Communication under the M2M-STNC scheme is performed over two phases: (1) the broadcasting phase and (2) the cooperation phase. In the former phase, each node broadcasts its data symbol to all the other nodes in the network in its allocated time slot, while in the latter phase, simultaneous transmissions from N-1 nodes to a destination node take place in their time slot. In addition, the M2M-STNC scheme with optimal node selection (i.e., M2M-STNC-ONS) is proposed. In this scheme, the optimal relay node is selected based on the maximum harmonic mean value of the source, intermediate, and destination nodes’ scaled instantaneous channel gains. Theoretical symbol-error-rate analysis for M-ary phase shift keying (M-PSK) modulation is derived for both the M2M-STNC and M2M-STNC-ONS schemes. Also, the effect of timing synchronization errors and imperfect channel state information on the SER performance and achievable rates is analytically studied. It is shown that the proposed M2M-STNC-ONS scheme outperforms the M2M-STNC scheme and is less sensitive to timing offsets and channel estimation errors. It is envisioned that the M2M-STNC-ONS scheme will serve as a potential many-to-many cooperative communication scheme with applications spanning sensor and mobile ad hoc networks.

On the Impact of Efficient Power Allocation in Pilot Based Channel Estimation Techniques for Multicarrier Systems

The use of pilot signals for the purpose of channel estimation in multicarrier systems does not only consume bandwidth but also signal power that could otherwise be invested in the information symbols to be transmitted. The aim of this paper is to investigate the issue of optimal transmitter power distribution between the pilot and information signals and evaluate its impact on the performance of multicarrier systems. It will be shown that the optimal power distribution is primarily influenced by the ratio of number of pilots to the total number of subcarriers used. An optimal pilot power allocation as a function of this ratio will be proposed for both MPSK and MQAM systems taking into account channel estimation errors

A Distributed Political Coalition Formation Framework for Multi-Relay Selection in Cooperative Wireless Networks

In this paper, the problem of multi-relay selection in one-to-many cooperative wireless networks is studied via a political coalition formation game approach. Specifically, each relay node is endowed with some coalitional strength, and the selected coalition consists of a subset of the available relays in the network that is powerful enough to win against any other potential coalition. In addition, the formed “ruling” coalition must be self-enforcing (and hence stable) such that none of its members would split and become the new ruling coalition. A distributed ruling coalition formation algorithm is proposed that selects such stable set of relays with a marginal compromise on network sum-rate performance. Moreover, our proposed algorithm offers a network sum-rate performance/stability tradeoff through formation of political parties of relays, which also reduces complexity and communication overheads. The proposed algorithm is compared with centralized multi-relay selection, as well as other multi-relay selection algorithms from the literature, and is shown to provide comparable network sum rate with the added advantage of network stability.

Network-Coded Bi-Directional Relaying for Amplify-and-Forward Cooperative Networks: A Comparative Study

In this paper, a comparative study of network-coded bi-directional amplify-and-forward (BD-AF) relaying is presented. In bi-directional relay networks, communication is performed over two phases: the broadcasting phase, and the cooperation phase. In the broadcasting phase, both source nodes broadcast their signals simultaneously to the N relay nodes, while in the cooperation phase, transmission is based on one of two modes: (1) time-division (TD), or (2) multiple-access (MA). In the TD-BD-AF scheme, each relay node is allocated a time-slot to transmit its processed signal, while in the MA-BD-AF scheme, all the N relay nodes simultaneously transmit network-coded signals to both source nodes, in a single time-slot. Moreover, a suboptimal relay selection (i.e. SRS-BD-AF) that approximately maximizes the sum-of-rates is proposed. Optimal and suboptimal sum-of-rates maximizing power allocations are studied under the TD-BD-AF and MA-BD-AF schemes, respectively, where it is shown that the MA-BD-AF scheme reduces to the SRS-BD-AF scheme. Symbol error rate performance analysis is provided, where it is shown that both the TD-BD-AF and SRS-BD-AF schemes achieve full diversity. Imperfect timing synchronization is analyzed and it is demonstrated that the SRS-BD-AF outperforms the other schemes in terms of the achievable rate. Simulation results are provided to complement the theoretical analysis.

A matching-theoretic approach to energy-efficient partner selection in wireless networks

In this paper, the problem of stable energy-efficient partner selection in cooperative wireless networks is studied. Each node aims to be paired with another node so as to minimize the total energy consumption required to meet a target end-to-end SNR requirement and thus maintain quality-of-service (QoS). Specifically, each node ranks every other node in the network according to their energy saving achievable through cooperation. Two polynomial-time algorithms based on the stable roommates matching problem are proposed through which nodes are paired according to their preference lists. The first algorithm, denoted Irvings stable matching (ISM), may not always have a stable solution. Thus, the second algorithm, denoted maximum stable matching (MSM), is proposed to find the maximum number of stable pairs. Simulation results validate the efficiency of the proposed algorithms in comparison with other matching algorithms, yielding a tradeoff between stability and total energy consumption.

On the impact of power allocation on coalition formation in cooperative wireless networks

In this paper, the impact of cooperative power allocation on distributed altruistic coalition formation in cooperative relay networks is studied. Particularly, equal power allocation (EPA), maxmin rate (MMR) and sum-of-rates maximizing (SRM) power allocation criteria are considered. A distributed merge-and-split algorithm is proposed to allow network nodes to form coalitions and improve their total achievable rate. The proposed algorithm is compared with that of centralized power control and coalition formation, and is shown to yield a good tradeoff between network sum-rate and computational complexity. Finally, numerical results illustrate that the SRM power allocation criterion promotes altruistic coalition formation and results in the largest coalitions among the different power allocation criteria.

Power allocation, relay selection and energy cooperation strategies in energy harvesting cooperative wireless networks

In this paper, optimal power allocation and relay selection strategies in energy harvesting cooperative wireless networks are studied. In particular, signal-to-noise ratio SNR-maximizing based power allocation and relay selection without and with energy cooperation-via wireless energy transfer-are considered. Moreover, total relay power minimization subject to target end-to-end SNR is investigated. The different optimal strategies are formulated as optimization problems, which are non-convex. Thus, intelligent transformations are applied to transform non-convex problems into convex ones, and polynomial-time solution procedures are proposed. Simulation results illustrate that power allocation strategies achieve higher end-to-end SNR than relay selection ones. Finally, energy cooperation is shown to be effective in improving end-to-end SNR, while total relay power minimization balances end-to-end SNR, transmit power consumption, and harvested energy. Copyright

Energy‐efficient partner selection in cooperative wireless networks: a matching‐theoretic approach

Summary In this paper, the problem of stable energy-efficient partner selection in cooperative wireless networks is studied. Each node aims to be paired with another node so as to minimize the total energy consumption required to meet a target end-to-end signal-to-noise ratio requirement and thus maintain quality of service. Specifically, each node ranks every other node in the network according to their energy saving achievable through cooperation. Two polynomial time complexity algorithms based on the stable roommates matching problem are proposed through which nodes are paired according to their preference lists. The first algorithm, denoted Irvings stable matching, may not always have a stable solution. Therefore, the second algorithm—which is a modified version of Irvings algorithm and denoted maximum stable matching—is proposed to find the maximum number of stable disjoint pairs. Simulation results are provided to validate the efficiency of the proposed algorithms in comparison with centralized energy-efficient partner selection as well as other matching algorithms, yielding a trade-off between stability and total energy consumption, but comparable symbol error rate performance and network sum rate. Copyright

Game-theoretic modeling and analysis of relay selection in cooperative wireless networks

In this paper, distributed single relay selection in cooperative wireless networks is modeled as a Chinese restaurant game CRG. Specifically, the CRG is used to model strategic relay selection decisions of source nodes, taking into account negative network externality due to the potential sharing of relay nodes among source nodes. Two cases are studied as follows: i perfect relay transmit power RTP knowledge and ii imperfect RTP knowledge. Under the first case, a distributed relay selection algorithm is proposed and shown to converge to a Nash equilibrium grouping. Under the second case, a reinforcement learning algorithm is proposed and combined with the distributed relay selection algorithm to allow network nodes to select rate-maximizing relays. Simulation results verify the efficiency of the proposed distributed relay selection algorithm when compared with other relay selection schemes and demonstrate that it yields a network sum-rate that is comparable with that of centralized relay selection. Copyright

Network sum-rate maximizing and max-min rate power allocation over time-varying multi-user multi-relay amplify-and-forward networks

In this paper, power allocation over time-varying multi-user multi-relay amplify-and-forward networks is studied. Specifically, stochastic network sum-rate and max-min rate power allocation problems are formulated. However, solving such stochastic problems relies on perfect global instantaneous channel state information (CSI), and thus entails complex computations and excessive communication overheads. To circumvent these issues, second-order statistics of the CSI (i.e. partial CSI) are utilized to transform the stochastic formulations into deterministic optimization problems in terms of ergodic capacity while satisfying quality-of-service constraints via target outage probability. The obtained optimal deterministic problems are non-convex and thus are computationally prohibitive. However, at high enough signal-to-noise ratio, such problems can be transformed into asymptotically convex ones, and thus solved efficiently. Simulation results illustrate that the proposed approximate deterministic power allocation reformulations coincide with their optimal exact deterministic and dynamic counterparts.