Introduction
1. What is the problem?
With the growth of technology, the development of micro sensors has come very far and for this reason researchers have been researching on new protocols for efficient communication between these sensors (nodes/sink nodes) which led to a lot of new protocols for the wireless sensor network. As these sensors are low-cost and low powered energy consumption in communication is a big problem. But not all suggested protocols take Energy Efficiency into consideration or even if some protocols do there is still room for improvement.
2. Why is it interesting and important?
The future of technology is envisioned to consist of hundreds and thousands of devices each with thousands of low cost, low power, highly integrated wireless sensor nodes (Micro Sensors) to sense the environment and report back with data in unattended mode. These wireless micro sensors can be used broadly for various environmental sensing applications such as military and civil applications [1] or vehicle tracking to habitat monitoring [2], [3]. In an ad hoc manner data gathered from multiple sensors are sent to station. However these sensor nodes don’t have unlimited energy and bandwidth supply which makes it difficult to deploy large number of sensor nodes as we envisioned. So energy awareness at all layers is necessary. At network layer energy-efficient routing setup can enhance/maximize the total lifetime of the network and also the lifetime of the sensors which is very important.
3. Why is it hard? (E.g., why do naive approaches fail?)
Designing a energy efficient routing protocol for WSN is very challenging due to some characteristics of wireless ad hoc network. As in this field thousands of sensor nodes will play key role in sensing the environment for the sink node is not possible to give different IP address as identification for communication which follows the classical IP-Based protocols for the deployment of huge number of sensor nodes. Again generated data from these sensors has significant amount of redundancy since multiple sensors near each other may generate same data from the environment within a phenomenon. Such redundancy has to be determined and solved by the routing protocols to reduce energy and bandwidth consumption since sensor nodes have limited transmission power and on-board energy [4].
4. Why hasn’t it been solved before?
There have been a lot of research on making the sensor network energy efficient and reliable. Many new protocols have been proposed considering the characteristics of sensor nodes, sink nodes and the required architecture for WSN. Some Data-centric protocols such as: SPIN (Sensor protocols for information via negotiation), Directed Diffusion, Rumor routing, Shah and Rabaey, GBR / RUGGED (Gradient-based routing), COUGAR, ACQUIRE (Active Query forwarding In Sensor Networks) [5] has been suggested over time for solving the issue of energy efficiency of Wireless Sensor Networks. But some of these have issue with guaranteed date delivery or overhead or other problems which should be solved. In this paper we will study Directed Diffusion protocol and it’s related protocols which has been suggested as improvement for WSN protocols and find problems which might help in suggesting improved energy efficient routing protocol for the wireless sensor networks.
Related Work
A. Directed Diffusion Protocol
Directed Diffusion [6] is data-centric routing protocol for wireless sensor networks. This efficient protocol doesn’t contain unnecessary operations of traditional network layer routing in order to save energy and make the communication efficient and faster. For communication an interest which consists of object name, data-rate, field duration and geographical area is created by the sink node and flooded to all neighbors. Neighbor nodes cache the interest and broadcast it and this continues until a node with same data as the flooded interest is found. A gradient field or path-trace is maintained by nodes upon receiving interest from it’s neighbor node so it can be used later to reply back. By tracking these gradients between nodes, paths are established form sink node to source nodes. In case of failure during communication alternative path is selected [6].
B. Energy Aware Routing
Shah and Rabaey [7] proposed new type of protocol architecture which works in the way of Directed diffusion but uses a probability function to choose optimal paths for communication between the nodes meaning the complete network paths are used instead of using single minimum energy path thus increasing the life time overall.
C. Rumor routing
Rumor routing [8] is another variation of Directed Diffusion where the authors suggested events in place of queries to the protocol for stopping unnecessary flooding in case of small amount of data requested by the sink node. Long lived packets called agents are generated by nodes when they detect an event and stores it to local table. Distant nodes get information from the generated local agents of its neighbor. When a query is generated by node for an event then nodes which knows the route only responds thus creating a link without flooding and wasting a lot of energy.
D. Energy Aware Diffusion
Energy aware diffusion [9] follows all the steps of directed diffusion in setup phase [6] but has different system for the operating phase described as Pathcalculation Phase [9] . Instead of selecting the path based on the quality as suggested in Direct Diffusion this protocol selects a path which requires minimum energy to send data from node to sink resulting in less energy consumption.
Many communication protocols of WSNs are surveyed in [10]. But our paper differs from other surveys as It deals with only Directed Diffusion protocol and similar protocols and tries to find vulnerability of them.
References
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2. G.J. Pottie, W.J. Kaiser, “Wireless Integrated Network Sensors” in: Communications of the ACM, vol. 43, no. 5, pp. 551-8, May 2000.
3. J. Warrior, “Smart Sensor Networks of the Future,” Sensors Magazine, March 1997.
4. Q.Gao, D.J.Holding, Y. Peng, K.J.Blow, “Energy Efficiency Design Challenge in Sensor Networks”.
5. M.R Mundada, S. Kiran, S.Khobanna, R. N. Varsha, S.A.George, “A STUDY ON ENERGY EFFICIENT ROUTING PROTOCOLS IN WIRELESS SENSOR NETWORKS,” in: International Journal of Distributed and Parallel Systems (IJDPS) Vol.3, No.3, May 2012.
6. Intanagonwiwat, C., R. Govindan, and D. Estrin, “Directed diffusion: a scalable and robust communication paradigm for sensor networks,” in: Proceedings of the 6th annual international conference on Mobile computing and networking. 2000. ACM.
7. R. Shah, J. Rabaey, “Energy aware routing for low energy ad hoc sensor networks,” in: Proceedings of the IEEE Wireless Communications and Networking Conference, 2002.
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10. B. Krishnamachari, D. Estrin, and S. Wicker, “The impact of data aggregation in wireless sensor networks,” In: Proceedings of the IEEE International Workshop on Distributed Event-Based Systems (DEBS), Vienna, Austria, July 2002. IEEE.