In this paper, we have proposed two new Routing, spectrum and core allocation (RSCA) schemes for offline survivable space division multiplexing elastic optical network (SDM-EON) supporting multi-class (mc) traffic in temporal domain. Multipath based protection scheme is applied to ensure survivability against single link failure, thus allowing traffic for each connection to be split amongst those paths. Advanced reservation (AR), being a part of multi-class traffic can withstand some delay from its time of arrival. Two schemes are designed based on the service of AR connections: all the split traffic in the multiple paths for a connection at the source node are set to start (i) at the same time strictly (mc-RSCA-S) and (ii) in a relaxed way by allowing different permissible times (mc-RSCA-R). Mixed integer linear programming (MILP) models are formulated for both the schemes. RSCA problem being an NP-hard one, those MILPs are not tractable and two heuristics with polynomial time complexity are developed. Two heuristics are based on a greedy approach and a simulated annealing (SA) based approach. Simulation studies of MILPs and the respective heuristics confirm that near optimal solutions are obtained by the proposed heuristics in identical experimental setup. It is observed that with an increase in the number of cores as well as in the percentage of AR connections in the incoming request set, spectrum utilization in the network and fragmentation of cores get reduced more by SA based approach compared to greedy approach.

We study the performance of a cognitive small cell network, catering multicast services to multiple groups of secondary users, using a pre-assigned set of orthogonal channels of primary users present in the corresponding macrocell. We consider the hybrid mode of cognitive radio operation for efficient spectrum access, where cooperative spectrum sensing is performed by the collocated secondary users of each group to ensure better protection to primary users' communication. Considering delay-sensitive application for each multicast group and availability of a rate adaptive application layer and a power adaptive link layer, we aim to maximize the energy efficiency of the small cell base station using a cross-layer approach. More precisely, a joint optimization problem involving sensing time, rate and power allocation is formulated to maximize the energy efficiency of the small cell network under the probabilistic interference constraint of each primary user and heterogeneous quality of service constraints of each SU multicast group. The problem is found to be generally non-convex and an iterative algorithm is proposed to find either an optimal or a near-optimal solution. Simulation results are presented to analyze the performance of our proposed scheme in terms of energy efficiency concerning some key system parameters. The results confirm that our solution is much more energy-efficient than the conventional approach with only transmit power adaptation.

Spectrum sensing (SS) is often considered to be one of the highly challenging issues in cognitive radio networks (CRNs), which is being extensively investigated to solve the growing problem RF spectrum scarcity in the next-generation wireless networks. Recently, spectrum prediction assisted cooperative spectrum sensing (CSS) is emerging as an effective way of SS, enabling efficient utilization of two critical resources of SS: time and energy. In this paper, we evaluate the reliability of hidden Markov model (HMM)-based CSS in CRNs, in the presence of random malfunctioning of secondary user (SU) nodes participating in the process. In view of the poor performance of the CSS, especially at low signal-to-noise ratio (SNR) values, we propose a new scheme to detect the possible presence of faulty nodes in the CSS system with high accuracy and quarantine them to maintain the reliability of the spectrum prediction process. The proposed scheme suggests a novel integration of the forward algorithm of HMM with fuzzy-C means clustering technique to design a robust spectrum prediction assisted CSS in CRNs. Simulation results confirm that our scheme delivers a significantly improved receiver operating characteristics compared to a prominent scheme even in the presence of high percentage of failure of SU nodes.

This study outlines a non‐orthogonal multiple access (NOMA) scheme for cooperative multicasting in a cognitive radio network. The network consists of a common base station (BS), which serves a primary user multicast group (PU‐MG) and a secondary user MG (SU‐MG). The SU‐MG is located in between the BS and the PU‐MG. Their proposed spectrum sharing protocol comprises of three transmission phases. The first phase is utilised by the BS for multicasting both PUs' and SUs' signals, using NOMA transmission. In the second phase, to overcome fading impairments, the BS exploits spatial diversity among SUs, by seeking their cooperation to relay PUs' message signal. The BS, as an incentive, leases a time slot in the third phase, exclusively for supporting multicast to SU‐MG over PUs' licenced spectrum. Analytical expressions for outage probabilities of both PU‐MG and SU‐MG are derived and validated using simulations. Furthermore, outage performance of PUs and ergodic capacity of SUs are compared with a prominent recent scheme.

In Delay-Tolerant Networks (DTNs), nodes forward data opportunistically upon contact because of irregular connectivity and low network-denseness. In this type of networks, energy plays an important role in successful data delivery and enhancement of network lifetime. To address the problem of selecting appropriate relay nodes for data forwarding, recently researchers are using concepts of social networks in the design of DTN routing schemes. This is because of its ability to make forwarding decisions based on the knowledge of long-term and more stable social characteristics of the nodes. In this paper, we propose an energy-aware relay selection scheme to support multiple multicast sessions based on an existing social-based single-data multicast scheme. The proposed scheme selects relays for delivering data to the destinations based on the centrality, one of the important social network characteristics, as well as on the residual energy of the DTN nodes. Our proposed scheme is shown to have polynomial-time complexity. We claim that our scheme supports higher number of multicast sessions thereby maintaining longer lifetime of the network while achieving required data delivery ratio compared to a prominent single-data multicast scheme. Our claim is validated through quantitative performance analysis.

We consider the problem of energy efficient broadcasting in wireless ad hoc network where nodes have limited energy resources. We investigate the scope of using directional antennas for energy efficient broadcast routing in stationary networks and consider the case where wireless nodes can dynamically adjust their transmission power for each broadcast session. Minimum spanning tree (MST) has an interesting property that the longest edge in the tree is the shortest among all the spanning trees. We construct a broadcast tree using minimum spanning tree and show that use of directional antennas, with fixed orientation and fixed beamwidth, for broadcasting data over this broadcast tree strikes a balance in the energy consumption rate among nodes in the network and hence improves overall lifetime of the network.