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Many emerging applications that depend on secure group communications demand the privacy of participants and access control at the multicast server. The multicast and broadcast services in IEEE 802.16 are efficient and power saving mechanisms, which no doubt also provide subscribers with strong and powerful security protection from the theft of service by encrypting broadcast connections between subscriber station (SS), relay station (RS), non-transparent relay station (NRS) and Multihop relay base station (MR-BS). However, the existing multicast and broadcast rekeying algorithm (MBRA) not only facing forward secrecy, backward secrecy and scalability problems for IEEE 802.16e but also for multihop relay based networks both in centralized as well as distributed zone. Although many researches try to give solutions for the above problems, all of them focus mainly on IEEE 802.16e networks and none of paper is published on distributed relay-based Wimax networks. This paper illustrates the main security problem of MBRA in general which is scalability, backward and forward secrecy and proposes a new Secure and efficient distributed Relaybased Rekeying Algorithm (SEDRRA) scheme for nontransparent Multihop IEEE 802.16 networks. The proposed scheme uses non-transparent decode and forward relays. Both analysis and performance evaluation show that our scheme can significantly reduce the complexity and solve all of the above problems in an efficient way.

In mobile communication, routing data through intermediate mobile node is a challenging task due to high mobility of nodes which causes rapid change in network topology and frequent disconnection between pair of nodes. To address these issues, Mobile Relay Station (MRS) is introduced into the network based on IEEE 802.16j standard. The MRS features are similar to the Fixed Relay Station (FRS), however the MRS has capability to move as Mobile Station (MS). In intermittent connection, by adapting the features of Delay Tolerant Network (DTN), the MRS can store and carry the data until it find the destination to forward the data. Assuming that MS is aware of its' own movement as well as its closest neighbor nodes. In this paper, Dynamic Routing Algorithm (DyRA) has been proposed to select next hop node towards the destination. The forwarding decision is based on a computed metric which is a combination of Packet Reception Rate (PRR), Link Expiration Time (LET) information and Number of Slots (NoS) available at the candidate MRS nodes. Also, the proposed Relay-based Vehicular Network (RVN) in WiMAX using cross layer design (CLD) is designed to select the optimal next hop node and set new route when current routing path is no longer available. The preliminary results for system throughput performance and average end-to-end delay are analyzed. The results show that by deploying relay-based in vehicular network can enhance system throughput in terms of packet loss ratio (PLR), packet delivery ratio (PDR), and average end-to-end (ETE) delay. NCTUns simulation environment has been used to study the mobile node performance.

No abstract

Heterogeneous networks with dense deployment of small cells can employ cognitive features to efficiently utilize the available spectrumresources. Spectrumsensing is the key enabler for cognitive radio to detect the unoccupied channels for data transmission. In order to deal with shadowing and multipath fading in sensing channels, cooperative spectrum sensing is designed to increase the accuracy of the sensed signal. In this paper, an optimized local decision rule is implemented for the case that the received data from primary users are possibly correlated due to the sensing channel impairments. Since the prior information is unavailable in the real systems, Neyman-Pearson criterion is used as the cost function. Then, a discrete iterative algorithm based on Gauss-Seidel process is applied to optimize the local cognitive user decision rules under a fixed fusion rule. This method with low complexity can minimize the cost using the golden section search method in a finite number of iterations. ROC curves are depicted using the achieved probability of detection and false alarm by numerical examples to illustrate the efficiency of the proposed algorithm. Simulation results also confirm the superiority of the proposed method compared to the conventional topologies and decision rules.