ABSTRACT One of the basic challenges that the sixth‐generation (6G) telecommunication is facing is the possibility of wide coverage to users in diverse geographical environments. Due to environmental events and unforeseen events such as problems with ground base stations, sometimes the services of these ground stations are disrupted, and as a result, to serve users and cover them, a drone base station (DBS) must be used. But the cost of creating the infrastructure for DBS is very high, and it should be possible to provide the maximum coverage for users with the least number of DBS. Therefore, the location of DBS is very important. Also, in order to provide services to users with the best quality, DBSs should be placed optimally in such a way that power consumption is minimized. In this research, we have presented a scheme based on the grasshopper optimization algorithm (GOA) for the optimal location of DBSs in IoT networks. Specifically, we conducted a performance analysis of one distinct scenario. Employing various intelligence strategies, the proposed method has been very successful in the optimal location of DBSs compared to other methods, and it has performed better in terms of power consumption.

In this paper, we study energy-efficient resource allocation in the downlink of buffer-aided wireless relay networks. We aim at maximizing the system average energy efficiency while maintaining the queue stability at both the base station (BS) and relays. We formulate the resource allocation design as a novel stochastic network optimization problem and based on the well-known Lyapunov drift-plus-penalty policy and the system constraints, we transform it to an instantaneous non-convex optimization problem to be solved in each time slot. We analyze the instantaneous utility function and propose a novel algorithm to find its optimum point. Based on that, we present an effective distributed strategy to get the globally optimal solution for channel and power allocation. Furthermore, we show that the proposed algorithm can be used as a building block for energy-efficient resource allocation in conventional relay networks, where the relays do not have buffering capability, but the BS queues need to be stabilized. Using extensive simulations, we show that the proposed algorithm is able to provide higher energy efficiency compared with the existing algorithms, while keeping the system queues stable.

Abstract Widespread utilization of mobile ad hoc networks, which communicate via broadcast wireless channels without any sort of infrastructure, raises security concerns. Introduction of identity‐based cryptography shed some light to security problems of mobile ad hoc networks. Key management (KM) plays significant role in network security. Although many proposals are suggested for identity‐based KM, they usually assume a trusted set of nodes during network initialization, which is not the case in many real‐world applications. In this paper, a novel identity‐based KM method is proposed, which utilizes Pedersen's verifiable secret sharing method. By distributing shared secret and key generation role among network nodes, the proposed method provides high levels of availability and scalability, while eliminating single point of failure. The proposed method provides a mechanism to check the validity of secret shares, which are generated by network nodes. To illustrate the effectiveness and capabilities of the proposed methods, they are simulated and compared with the performance of the existing methods. Copyright © 2016 John Wiley & Sons, Ltd.

Abstract Medium access standards rely on complete cooperation of network nodes to provide fair access to common medium. But a selfish user can manipulate its network adapter to gain more access to valuable network resources. Existence of a selfish node in a network can severely degrade performance of well‐behaved nodes. As a result, these well‐behaved nodes experience drastic throughput drop and large amount of delay. In this paper, a modification to IEEE 802.11 MAC layer is proposed, which reduces the cheating possibility of the selfish node. In the proposed method, next transmitter is selected by current receiver and announced to neighbor nodes. This selection is based on channel usage ratio of neighbor nodes. The specified transmitter starts its transmission immediately after current transmission regardless of its backoff value. Main advantages of the proposed method over existing ones are its capability to mitigate various selfish misbehaviors, robustness against adaptive selfish strategies (a selfish node with ability to change its strategy to deceive security system), and high resiliency against aggressive selfish node (a node with high intention to do selfish behavior). Also, in absence of any selfish node, proposed method does not disturb normal operation of the network. If the proposed method is employed, performance of the network (in terms of throughput of well‐behaved nodes and fairness) is approximately not affected in presence of selfish node. This improvement in performance metrics is illustrated by simulating various strategies for selfish node and comparing the results with similar approaches. Copyright © 2014 John Wiley & Sons, Ltd.