Effective Cache based Policies in Wireless Sensor Networks: A Survey <s> Figure 1. Wireless Sensor Network <s> Previous research on transport layer protocols for wireless sensor ::: networks (WSNs) has focused on designing protocols specifically ::: targeted for sensor networks. Most sensor networks applications, ::: however, are only useful when connected to an external network. The ::: deployment of TCP/IP in WSNs would enable direct connection between ::: the WSN and external TCP/IP networks. However, TCP performs badly in ::: wireless environments both in terms of throughput and energy ::: efficiency. To overcome these problems in WSNs we have designed ::: Distributed TCP Caching. This mechanism greatly enhances TCP ::: performance by caching TCP segments on the nodes in the sensor network ::: and locally retransmitting lost segments. Our simulations ::: demonstrate that with these enhancements TCP performs well enough to ::: be useful in wireless sensor networks. <s> BIB001 </s> Effective Cache based Policies in Wireless Sensor Networks: A Survey <s> Figure 1. Wireless Sensor Network <s> Wireless sensor networks hold a very promising future. The nodes of wireless sensor networks (WSN) have a small energy supply and limited bandwidth available. Since radio communication is expensive in terms of energy consumption, the nodes typically spend most of their energy reserve on wireless communication (rather than on CPU processing) for data dissemination and retrieval. Therefore, the role of energy conserving data communication protocols and services in WSN can not be overemphasized. Caching data at locations that minimize packet transmissions in the network reduces the power consumption in the network, and hence extends its lifetime. Finding locations of the nodes for caching data to minimize communication cost corresponds to finding the nodes of a weighted Minimum Steiner tree whose edge weights depend on the edge's Euclidean length and its data traffic rate. We call this tree a Steiner Data Caching Tree (SDCT). We prove that an optimal SDCT is binary, and that at-least two of the three internal angles formed at the Steiner points are equal. We derive expressions that determine the exact location of a Steiner point for a set of three nodes based on their location and their data refresh rate requirements. Based on these (optimality) results, we present a dynamic distributed energy-conserving application-layer service for data caching and asynchronous multicast. We present the results of simulation of our service that verifies its power saving properties. <s> BIB002 </s> Effective Cache based Policies in Wireless Sensor Networks: A Survey <s> Figure 1. Wireless Sensor Network <s> This paper proposes few ways of improving a WSN's energy efficiency that already uses an energy efficient data routing protocol for continuous monitoring application. The proposed improvements are (i) data negotiation, (ii) development of data change expectancy, and (iii) data vanishing. In data negotiation, an active sensor sends its sensed data only when the data changes. In expectancy development, a sensor develops the expectancy of when its sensed data might change. It then adjusts its sensing frequency accordingly to avoid unnecessary sensing. In data vanishing, duplicate sensed data from multiple sensors are discarded while routed to the BS. Together, the proposed improvements can be viewed as an emulated cache where latest sensed data are always known without requiring the sensors to sense and report continuously. Our simulation results also show significant WSN lifetime increase from this emulated caching. <s> BIB003 </s> Effective Cache based Policies in Wireless Sensor Networks: A Survey <s> Figure 1. Wireless Sensor Network <s> In this paper, we propose a caching scheme for wireless sensor networks which exploits cooperation among various sensor nodes in a zone formed around few sensor nodes. Zones are created by using dual radio mode of sensor nodes i.e. high and low power transmission ranges define zone size. In order to realize much larger cumulative cache, a node along with its own storage utilizes storage of sensor nodes in zone formed around it. Zone size is taken such that all nodes in a zone communicate with each other in single-hop using low power radio and hence conserves energy in cumulative cache management. Considering multiple and mobile sinks in sensor field, we develop unique token based cache admission control, cache discovery and least importance based item replacement policy. Proposed caching scheme is applied to two-tier data dissemination (TTDD) approach and newly proposed dual radio based data dissemination (DRDD) approach. Simulation results show significant gains in energy efficiency when cooperative caching is used in both approaches as compared to scenarios when these dissemination schemes do not employ caching. <s> BIB004 </s> Effective Cache based Policies in Wireless Sensor Networks: A Survey <s> Figure 1. Wireless Sensor Network <s> In a wide range of applications, such as detecting environmental hazards, monitoring remote terrain and even monitoring customer behavior, wireless sensor networks (WSNs) are playing an important role. Due to the limited energy in each node, a lot of attention has been paid on improving energy efficiency. In this paper, we first propose an energy-efficient waiting caching (EEWC) algorithm to improve the data-centric (DC) transport control protocol by cutting down traffic flow. Second, we deploy networked predictive controller (NPC) to shorten network delay. Thus, the energy consumption can be reduced accordingly. We also analyze the proposed algorithm. Finally, we conduct extensive simulation experiments to evaluate the performance of the proposed algorithm. <s> BIB005
The well known problem in using these networks is limited battery life. This is due to fact that the size of a sensor node is expected to be small and this forces constraints on its components i.e. battery size, processors, data storing memory, all are needed to be small. So any optimization in these networks should focus on optimizing energy consumption. In WSN a lot of sensed data and routing information has to be sent which often have some time constraints so that the information can be utilized before any mishap occurs. The energy power consumption is much higher in data communication than internal processing. So energy conservation in WSN is needs to be addressed. A number of schemes related to caching have been proposed. First scheme includes cooperative caching BIB004 which utilizes dualradio based antennas and caches data at the nodes nearer to the sink. In second scheme, BIB003 proposes making effective caching by data negotiation between Base Station and the sensors, developing expectancy of data change and data vanishing. Another strategy BIB005 gives a waiting cache which waits for the data of the same cluster until it becomes available within a threshold, aggregating it with the packet from the lower cluster and then sending it to the sink, thus reducing number of packets from the network. The fourth BIB002 scheme considers the whole network to be a Steiner Data Caching Tree which actually is a binary tree and buffers data at some intermediate node (data cache) such that it reduces the network traffic during multicast. In fifth BIB001 implementation of TCP support for the WSNs and schemes to avoid end to end transmission between the nodes by caching TCP segments and by local retransmission of TCP segments has been proposed. Some more discussion about cache utilization has also been discussed. Rest of the paper is organized as follows. Section II describes various techniques to exploit caching. Section III gives the conclusion out of using caching in WSNs presented in this paper.