Since nodes in a sensor network have limited energy, prolonging the network lifetime and improving scalability become important. In this paper, we propose a distributed weight-based energy-efficient hierarchical clustering protocol (DWEHC). Each node first locates its neighbors (in its enclosure region), then calculates its weight which is based on its residual energy and distance to its neighbors. The largest weight node in a neighborhood may become a clusterhead. Neighboring nodes will then join the clusterhead hierarchy. The clustering process terminates in O(1) iterations, and does not depend on network topology or size. Simulations show that DWEHC clusters have good performance characteristics.

Mobile computing has the potential for managing information globally. Data management issues in mobile computing have received some attention in recent times, and the design of adaptive broadcast protocols has been posed as an important problem. Such protocols are employed by database servers to decide on the content of broadcasts dynamically, in response to client mobility and demand patterns. In this paper we design such protocols and also propose efficient retrieval strategies that may be employed by clients to download information from broadcasts. The goal is to design cooperative strategies between server and client to provide access to information in such a way as to minimize energy expenditure by clients. We evaluate the performance of our protocols both analytically and through simulation.

Mobile computing has the potential f o r managing information globally. Data management issues in mobile computing have received some attention in recent times, and the design of adaptive broadcast protocols has been posed as an important problem. Such protocols are employed by database servers to decide on the content of broadcasts dynamically, in response to client mobility and demand patterns. In this paper we design such protocols and a1 s o propose e@ci en t retrieval st rat egies that m.ay be employed b y clients to download information from broadcasts. The goal is to design cooperative strategies between server and client to provide access to information in such a way as to mini,mize energy expenditure b y clients. W e evaluate the performance of our protocols analytically.

Through direct communication, device-to-device (D2D) technology can increase the overall throughput, enhance the coverage, and reduce the power consumption of cellular communications. Security will be of paramount importance in 5G, because 5G devices will directly affect our safety, such as by steering self-driving vehicles and controlling health care applications. 5G will be supporting millions of existing devices without adequate built-in security, as well as new devices whose extreme computing power will make them attractive targets for hackers. This paper presents a survey of the literature on security problems relating to D2D communications in mobile 5G networks. Issues include eavesdropping, jamming, primary user emulation attack, and injecting attack. Because multipath routing emerges as a strategy that can help combat many security problems, particularly eavesdropping, the paper contains an extensive discussion of the security implications of multipath routing. Finally, the paper describes results of a simulation that tests three path selection techniques inspired by the literature. The simulation reveals that routing information through interference disjoint paths most effectively inhibits eavesdropping.

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