In delay-tolerant wireless sensor networks, messages for sensor data are delivered using opportunistic contacts between intermittently connected nodes. Since there is no stable end-to-end routing path like the Internet and mobile nodes operate on battery, an energy-efficient routing protocol is needed. In this article, we consider the probabilistic routing protocol using history of encounters and transitivity protocol as the base protocol. Then, we propose an energy-aware routing protocol in intermittently connected delay-tolerant wireless sensor networks, where messages are forwarded based on the node's remaining battery, delivery predictability, and type of nodes. The performance of the proposed protocol is compared with that of probabilistic routing protocol using history of encounters and transitivity and probabilistic routing protocol using history of encounters and transitivity with periodic sleep in detail, from the aspects of delivery ratio, overhead ratio, delivery latency, and ratio of alive nodes. Simulation results show that the proposed protocol has better delivery probability, overhead ratio, and ratio of alive nodes, in most of the considered parameter settings, in spite of a small increase in delivery latency.
Abstract:Reducing energy consumption of mobile communication networks has gained significant attentions since it takes a major part of the total energy consumption of information and communication technology (ICT). In this paper, we consider 5G networks with heterogeneous macro cells and small cells, where data and control planes are separated. We consider two types of data traffic, i.e., low rate data traffic and high rate data traffic. In basic separation architecture, a macro cell base station (MBS) manages control signals, while a small cell base station (SBS) manages both low rate data traffic and high rate data traffic. In the considered modified separation architecture, an MBS manages control signals and low rate data traffic, while an SBS manages high rate data traffic. Then, an efficient energy saving scheme for base stations (BSs) is proposed, where the state of a BS is determined depending on the number of user equipments (UEs) that request high rate data traffic and the number of UEs that exist under the overlapping areas commonly covered by the considered BS and the neighbor BSs. We formulate an optimization problem for the proposed energy saving scheme and obtain the solution using particle swarm optimization (PSO). Numerical results show that the proposed energy saving scheme in the modified separated network architecture has better energy efficiency compared to the conventional energy saving schemes in both basic and modified separated network architectures. Also, the proposed energy saving scheme has lower aggregate delay.
Hybrid protocols combining a mobile ad hoc network (MANET) and a delay tolerant network (DTN) have recently been proposed. In these works, a whole network is fragmented, and MANET is generally used for intra-fragment communication, while DTN is used for inter-fragment communication. In this paper, an improved hybrid routing protocol was proposed, wherein virtual source nodes are selected based on the delivery predictability to the destination node if routing path to the destination node is not successfully established using MANET protocol. Then, messages are delivered to the destination node from the original source node and selected virtual source nodes. Performance evaluation results show that the proposed protocol with appropriate selection of delivery predictability threshold values has a better delivery ratio than conventional protocol, at the expense of overhead ratio in the considered parameter setting.
Delay tolerant networks (DTN) is a good candidate for delivering information-centric networking (ICN) messages in fragmented networks due to disaster. In order to efficiently deliver ICN messages in DTN, the characteristics of multiple requester nodes for the same content and multiple provider nodes for the same request should be used efficiently. In this paper, we propose an efficient DTN routing protocol for ICN. In the proposed protocol, requester information for request packet, which is called an Interest in ICN, is shared by exchanging status table with requested Data ID, requester ID, and satisfaction flag, where satisfaction flag is defined to show the delivery status of Data, so that unnecessary forwarding of Data is avoided. Data is forwarded to a more probable node by comparing average delivery predictability to a set of requesters. Performance of the proposed protocol was evaluated using simulation from the aspect of Data delivery probability and Data overhead, for varying buffer sizes, number of relay nodes, and time-to-live (TTL) of Data. The results show that the proposed protocol has better Data delivery probability, compared to content distribution and retrieval framework in disaster networks for public protection (CIDOR) and opportunistic forwarding (OF) protocols, although there is a tradeoff from the aspect of Data overhead for varying buffer sizes and number of relay nodes.
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