Outage analysis of superposition modulation aided network coded cooperation in the presence of network coding noise

We consider a network, where multiple sourcedestination pairs communicate with the aid of a half-duplex relay node (RN), which adopts decode-forward (DF) relaying and superposition-modulation (SPM) for combining the signals transmitted by the source nodes (SNs) and then forwards the composite signal to all the destination nodes (DNs). Each DN extracts the signals transmitted by its own SN from the composite signal by subtracting the signals overheard from the unwanted SNs. We derive tight lower-bounds for the outage probability for transmission over Rayleigh fading channels and invoke diversity combining at the DNs, which is validated by simulation for both the symmetric and the asymmetric network configurations. For the high signal-to-noise ratio regime, we derive both an upperbound as well as a lower-bound for the outage performance and analyse the achievable diversity gain. It is revealed that a diversity order of 2 is achieved, regardless of the number of SN-DN pairs in the network. We also highlight the fact that the outage performance is dominated by the quality of the worst overheated link, because it contributes most substantially to the network coding noise. Finally, we use the lower bound for designing a relay selection scheme for the proposed SPM based network coded cooperative communication (SPM-NC-CC) system.<br/

Optimizing network-coded cooperative communications via joint session grouping and relay node selection

Abstract—Network-coded cooperative communications (NC-CC) is a new paradigm in wireless networks that employs network coding (NC) to improve the performance of CC. The core mechanism to harness the benefits of NC-CC is to appropriately combine sessions into separate groups, and then have each group select the most beneficial relay node for NC-CC. In this paper, we study this joint grouping and relay node selection problem for NC-CC. Due to NP-hardness of problem, we propose a distributed and online algorithm that offers near-optimal solution to this problem. The key idea in our algorithm is to have each neighboring relay node of a new session determine and offer its best local group; and then to have the source node of the new session select the best group among all offers. We show that our distributed algorithm has polynomial complexity. Using extensive numerical results, we show that our distributed algorithm adapts well to online network dynamics. I

Prioritization, security and relay selection in network coded multiple access relay networks

Wireless communication is undoubtedly one of the most significant advancements by the mankind for improving quality of life. Information is transmitted from one point to another via electromagnetic waves. After Shannon\u27s landmark paper ``A Mathematical Theory of Communication\u27\u27 in 1948, significant advancements have occurred in providing reliable point to point wireless communication. With ever growing need for reliable high speed links, Cooperative communication and Network coding have emerged as viable technologies to bridge the gap. In today\u27s wireless network, different users have different demands for reliability based on their respective application. In this context, we propose flexible network coding scheme to adapt to user needs. We develop coding rules which achieve maximal diversity of the system, yet provide differentiated class of service to the users. The proposed scheme can be adjusted to accommodate the dynamic changes in quality of service(QoS) demand of users. Second we consider the issue of security in multiple access relay network. Security has always been a primary concern in wireless networks due to it broadcast nature of transmission. The intermediate relay nodes in a wireless network could be modified by adversary to transmit corrupted information. We propose a novel iterative packet recycling methodology which gives performance improvement over traditional approach of discarding received corrupted packets at the destination. Finally, we consider the problem of choosing relay for transmission. We propose a novel selection scheme which provides balanced relay utilization and reduces relay switching rate compared to the traditional selection algorithms. This cuts down energy wastage at the relay and improves the overall network lifetime

Cross-layer Optimization in Wireless Multihop Networks

In order to meet the increasing demand for higher data rates, next generation wireless networks must incorporate additional functionalities to enhance network throughput. Multihop networks are considered as a promising alternative due to their ability to exploit spatial reuse and to extend coverage. Recently, industry has shown increased interest in multihop networks as they do not require additional infrastructure and have relatively low deployment costs. Many advances in physical and network layer techniques have been proposed in the recent past and they have been studied mostly in single-hop networks. Very few studies, if any, have tried to quantify the gains that these techniques could provide in multihop networks. We investigate the impact of simple network coding, advanced physical layer and cooperative techniques on the maximum achievable throughput of wireless multihop networks of practical size. We consider the following advanced physical layer techniques: successive interference cancellation, superposition coding, dirty-paper coding, and some of their combinations. We achieve this by formulating several cross-layer frameworks when these techniques are jointly optimized with routing and scheduling. We also formulate power allocation subproblems for the cases of continuous power control and superposition coding. We also provide numerous engineering insights by solving these problems to optimality