QUALITY OF SERVICE METRICS FOR DATA TRANSMISSION IN MESH TOPOLOGIES

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1 QUALITY OF SERVICE METRICS FOR DATA TRANSMISSION IN MESH TOPOLOGIES SWATHI NANDURI * ZAHOOR-UL-HUQ * Master of Technology, Associate Professor, G. Pulla Reddy Engineering College, G. Pulla Reddy Engineering College, Kurnool, Andhra Pradesh, Kurnool, Andhra Pradesh, India, India, ABSTRACT Mesh topologies are important for large-scale highly engineered systems. The Quality of Service (QoS) in such systems is known to decrease as the number of nodes and messages increases. We present a scalable approach for dissemination that exploits all the shortest paths between a pair of nodes and improves the QoS. Despite the presence of multiple shortest paths in a system, we show that these paths cannot be exploited by spreading the messages over the paths in a simple round-robin manner; nodes along one of these paths will always handle more messages than the nodes along the other paths. We characterize the set of shortest paths between a pair of nodes in regular mesh topologies and derive rules, using this characterization, to effectively spread the messages over all the available paths. These rules ensure that all the nodes that are at the same distance from the source handle roughly the same number of messages. By using multipath propagation and demonstrating the transmission results in case of propagation irregularities and link failures the QoS improved with this approach. Keywords: Mesh Topology, Dissemination, Contour, Contour Guided Dissemination I. INTRODUCTION The use of novel devices for communication in highly engineered and network embedded systems are presenting new challenges for monitoring and diagnosing them. These systems contain large number of nodes which will interact in peer-peer manner to achieve the application objectives [1]. To increase the number of simultaneous interactions between these nodes the transmission range of each node is restricted so that it can only communicate with its immediate set of neighbors. This arrangement is called Mesh Topology [2]. Multihop communications are necessary in such systems to send messages from any source to any destination. For example, intermediate nodes must forward messages to a monitoring station from nodes that cannot communicate directly with the ISSN: Page 1

2 monitoring station. Routing protocols are used extensively in wired and wireless networks to support multihop communication [6]. Such protocols construct and maintain routing tables at each node by relying on system wide unique node identifiers. When the number of nodes is very large, such as in sensor networks, it is not feasible to use such identifiers. Several techniques, called dissemination methods, were developed at the network layer to regulate the flow of messages between nonadjacent nodes without relying on unique node identifiers or constructing routing tables using these identifiers[3][4][5].in this paper we consider all the nodes arranged in a mesh topology and try to effectively utilize all the shortest paths present between the nodes and thus ensure that this effective utilization improves QOS. Because each node communicates directly with its immediate set of neighbors, there are multiple shortest paths between many pairs of nodes in a mesh topology. The number of such paths is limited by the relative locations of the nodes. For example, the number of shortest paths between certain pairs of nodes is one, despite the mesh topology. We define a Contour as the union of all the shortest paths between a pair of nodes and present some results to precisely characterize the structure of contours. Using this structure, we show that when messages are spread in a round-robin manner, nodes along one path in the contour will always handle more messages than the nodes along other paths in the contour. Consequently, the benefits of the multiple paths cannot be fully realized. We then present a strategy for spreading messages to neighboring nodes that effectively exploits the available shortest paths and show that our rules for spreading the messages result in a balanced loading of all the available shortest paths. We refer to this approach as Contour Guided Dissemination (CGD). II. RELATED WORK Routing protocols used in traditional wired and wireless networks are based on shortest path algorithms such as the Bellman-Ford algorithm [6] and Dijkstra s algorithm [7].Similar protocols have been reported for ad hoc, wireless, and mobile networks The QoS achieved in these systems has also been studied. The dissemination method we describe in this paper is somewhat similar to a gradient dissemination scheme with the cost metric being the deviation from evenness of load distribution on all available shortest paths. In the current methods, the motivating factors for considering multipath routing include fault tolerance, higher aggregate bandwidth, and load balancing. The QoS aspects of multipath routing have also been addressed. The split multipath routing protocol maintains maximally edge-disjoint paths. All such method essentially focus on the discovery and maintenance of multiple paths that are useful under various constraints on the node distribution. In contrast, we assume regular mesh topologies and then precisely characterize the set of all shortest paths between any pair of nodes. We then use this geometric structure to propose rules for dissemination that result in all available shortest paths being utilized effectively so that QoS improves. III. OTHER DATA DISSEMINATING ALGORITHSMS In this section we describe other data disseminating methods and compare its performance with CGD. ISSN: Page 2

3 A. Classical Flooding In this approach a node wishes to disseminate a piece of data across the network by sending the data across all its neighbors. Whenever a node receives a data it makes copies of the data and sends that data across all its neighbors except to the node from which it received the data. The amount of time that all the nodes receives the data and makes copies of it and forwards that to all its neighbors is called a Round. The disadvantage with this approach is it will cause the nodes to handle many messages. B. Gossiping Gossiping is an alternative to classical flooding that uses randomization to conserve energy. Instead of forwarding data to all neighbors gossiping node only forwards data on to one randomly selected neighbors. If gossiping node receives data from a given neighbor it can forward data back to that neighbor provided if it randomly selects that neighbor. This approach requires less communication traffic but average end-end delivery rate is poor. C. Reverse-path forwarding It is a general approach that is used in several dissemination protocols. In this approach, a sink node (such as a Monitoring Station) generates a query that indicates an interest in data items from one or more nodes. Such a query is forwarded along one or more paths from the sink to all the nodes. The nodes forward data along these paths; since the data propagates in a direction that is reverse of the query direction, this method is referred to as reverse-path forwarding. The major flaw with this approach is if the underlying dynamic routing mechanism changes the routing tables used by the nodes during the course of broadcast, then that packet may not be delivered to the node even if the path to it exists. D. Cost field approach This is another choice for routing. Every node maintains a scalar that represents the cost of sending data back to the sink and the data is propagating along the cost gradients. Protocols based in cost-field require less memory space compared to reverse-path forwarding since there is no need to maintain a routing table. Routing decisions are based in the cost at each node. Since nodes are resource constrained in both communication and computation capabilities, cost field based approach is a good choice. E. Virtual Hierarchy approach As shown in the fig.. nodes form local clusters and a cluster head will be elected from the cluster. Nodes in the cluster may rotate their roles as the cluster head in order to achieve the energy consumption balance in the cluster. Since the radio transmission strength is adjustable, the cluster head node can be set to a more powerful transmission range to reach the monitoring station. ISSN: Page 3

4 In this analysis, we present a dissemination method that will ensure that all the nodes that are equidistant from the source node, of a contour handle approximately same number of messages. While in a uniform spreading this load balancing is not achieved.the shapes of the contours varies depending upon the node parameters. F. Geographical forwarding By utilizing the GPS or the location on a grid, the network uses location information to achieve a more efficient routing in the network. Geographic adaptive fidelity sets up a virtual grid depending on the GPS providing location and saves energy in the network by propagating messages in different nodes in the same region. The disadvantage with this approach is that GPS receivers are too expensive in terms of energy consumption,size or cost. Structure of a Contour in E 8 Concrete Challenges with the above Methods: Message loss rate is more Path link failures are more Difficult to re-transmit the messages IV. Contour Guided Dissemination V. SYSTEM EVALUATION ISSN: Page 4

5 In this section, we investigate the impact on the performance of Contour Guided Dissemination system resulting from the adopted strategy to deploy it in the network.. We consider the following schemes to implement our CGD: Here in order to realize the benefits of all the shortest paths we consider that every node receives a packet from its upstream neighbor and forwards it to its downstream neighbor. To utilize this practically we consider that every node will have the address of its sender and receiver. As the message propagate through the network, every intermediate node could easily compute (using, e.g., the distance criterion) which of its immediate neighbors are on a shortest path to the destination. For our analysis purpose we have used Java technology to show the results of our CGD approach by exploiting all the available shortest paths and observed the efficiency in the transmission of messages even incase of link failures. The number of messages handled by each node, average end-end latency, jitter, message loss rate were the primary QOS metrics considered. It was observed after practical analysis that CGD has comparatively low message loss rate and less jitter and delay were experienced. We used the above mentioned metrics as a basis to compare the performance of CGD with the unipath routing which is based on distance vector routing algorithm and shortest path tree that will be precomputed using structure of all shortest paths. In the following graphs we have taken probability of link failures on X-axis and various QoS parameters like Message loss rate Jitter and average delayon Y-axis and obtained the following results: Message Loss Rate VI. IMPLEMENTATION ISSN: Page 5

6 Average Delay with general topologies. In such networks, some nodes must spread the messages, while other nodes must utilize one of the available paths without spreading the messages further. Identifying the structure of contours, for networks with general topologies are interesting problems and the method presented here provides a systematic framework in which to carry out future investigation. IX. REFERENCES Jitter VII. FUTURE SCOPE Contour Guided Dissemination for propagating messages in networked embedded systems that exploits the location of each node and the multiple paths available between a source and a sink. The union of all of the shortest paths between a source and a sink was defined to be a contour. Focus will be laid in developing such Dissemination protocols to achieve efficient data transmissions. VIII. CONCLUSION [1] Hill, M. Horton, R. Kling, and L. Krishnamurthy, The Platforms Enabling Wireless Sensor Networks, Comm. ACM, vol. 47, no. 6, pp , June [2].F. Akyldiz, X. Wang, and W. Wang, Wireless Mesh Networks: A Survey, Computer Networks, vol. 47, pp , [3] J. Gao and L. Zhang, Load-Balanced Short-Path Routing in Wireless Networks, IEEE Trans. Parallel and Distributed Systems, vol. 17, no. 4, pp , Apr [4] C. Intanagonwiwat, R. Govindan, D. Estrin, J. Heidemann, and F. Silva, Directed Diffusion for Wireless Sensor Networking, IEEE/ACM Trans. Networking, vol. 11, no. 1, pp. 2-16, [5] J. Kulik, W. Heinzelman, and H. Balakrishnan, Negotiation- Based Protocols for Disseminating Information in Wireless Sensor Networks, Wireless Networks, vol. 8, pp , [6] R.E. Bellman, Dynamic Programming. Princeton Univ. Press, [7] G. Coulouris,J. Dollimore, and,t. Kindberg, Distributed Systems Concepts and Design, fourth ed. Addison-Wesley 2005 Although the results were based on a regular topology, these results suggest new methods for dissemination in networks ISSN: Page 6

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