End To End Delay Analysis Of Wireless Sensor Network Computer Science Essay
The end-to-end delay is one of the most critical and fundamental issues for wireless sensor networks which are used in industrial environment. Sensor networks deployed in industrial environment have very strict time constraints (end-to-end delay). However, the end-to-end delay is difficult to bind for event- driven sensor networks, where nodes generate and propagate data only when an event of interest occurs, and hereby producing unpredictable traffic load.
This paper analyses the end to end delay and energy consumption in event driven wireless sensor network by considering different routing protocol i.e. AODV and DSDV, under IEEE 802.11 as MAC layer protocol. The simulation results shows that end to end delays by using DSDV are lesser than AODV and it also shows slightly lower energy consumption than AODV in different traffic conditions.
Keywords: End-to-end delay, energy consumption, wireless sensor network, AODV (Ad-hoc On- demand Distance Vector), DSDV (Destination Sequence Distance Vector)
From last few years, wireless sensor networks have attracted more and more related researchers for its advantages. These networks will consist of large numbers of distributed nodes that organize themselves into a multi-hop wireless network. Each node has one or more sensors, embedded processors and low-power radios, and is normally battery operated. Typically, these nodes coordinate to perform a common task. WSN is useful in many applications like industrial control, habitat monitoring, ubiquitous healthcare etc.
This paper concentrates on industrial application of WSN. In industrial application quality of service of WSN is very important. The factor consider for maintaining good quality of service in this application are end-to-end delay, energy consumption, throughput, packet delivery ratio etc.
This application has very strict timing requirements, if there is delay of fraction of second which leads to big hazard. It also has stringent energy requirement, if battery of any node will fail it leads failure of network. Here, the paper concentrates on this to measure issues end-to-end delay and energy consumption.  The delays and energy consumption will introduce in all layers of WSN. The paper considers the delays and energy consumption happen at medium access control (MAC) layer and routing layer. The MAC protocol used is IEEE 802.11 which is widely used in low cost protocol for industrial application of WSN. Two routing protocol consider are AODV and DSDV, which are widely used protocol in ad-hoc wireless network.
The scope of this paper is to analyse the end-to-end delay and energy consumption of single sink environment of industrial application by considering IEEE 802.11 as MAC protocol and AODV and DSDV as routing protocol under different traffic load conditions by using NS-2 (Network Simulator-2) .
The remainder of the paper is organized as follows: Section 2 gives short overview of IEEE 802.11, AODV and DSDV protocol. Section 3 describes the network model and simulation environment. Section 4 shows the simulation result and analysis of it.
II. Mac and Routing Protocol
This section gives the overview of MAC and routing layer protocol used in the experimentation. The MAC layer protocol used in IEEE 802.11 and two routing protocol are used, AODV and DSDV for analysing the effect of different routing protocol on end-to-end delay and energy consumption under different traffic load conditions.
A. IEEE 802.11
IEEE 802.11 is a well known contention based medium access control (MAC) protocol which uses carrier sensing and randomized back- offs to avoid collisions of the data packets. The Power Save Mode (PSM) of the IEEE 802.11 protocol reduces the idle listening by periodically entering into the sleep state. This PSM mode is used for the single – hop network where the time synchronization is simple and may The not be suitable for multi-hop networks because of the problems in clock synchronization, neighbour discovery and network partitioning.
In the DSDV  routing protocol routing messages are exchanged between neighbouring mobile nodes (i. e. mobile nodes that are within range of one another). Routing updates may be triggered or routine. Updates are triggered in case routing information from one of the neighbours forces a change in the routing table. A packet for which the route to its destination is not known is cached while routing queries are sent out.
DSDV was one of the early algorithms available. It is quite suitable for creating ad hoc networks with small number of nodes. Since no formal specification of this algorithm is present there is no commercial implementation of this algorithm.
AODV  is a combination of both DSR (Dynamic Source Routing) and DSDV protocols. It has the basic route-discovery and route-maintenance of DSR and uses the hop-by-hop routing, sequence numbers and beacons of DSDV. The node that wants to know a route to a given destination generates a ROUTE REQUEST. The route request is forwarded by intermediate nodes that also create a reverse route for itself from the destination. When the request reaches a node with route to destination it generates a ROUTE REPLY containing the number of hops requires reaching destination. All nodes that participate in forwarding this reply to the source node create a forward route to destination.
The Ad hoc On-Demand Distance Vector (AODV) routing protocol is intended for use by mobile nodes in an ad hoc network. It offers quick adaptation to dynamic link conditions, low processing and memory overhead, low network utilization, and determines unicast routes to destinations within the ad hoc network. It uses destination sequence numbers to ensure loop freedom at all times (even in the face of anomalous delivery of routing control messages), avoiding problems (such as "counting to infinity") associated with classical distance vector protocols.
III. Network Model and Simulation
The environment or network model consider for
simulation purpose is as shown in figure 1. Here, the paper considers the industrial wireless sensor environment which consists of multiple source nodes and single sink node. The model is design for multi-hop and one hop situation.
In figure 1, node0 is sink node and node1 to node36 are source nodes. Every source is generating 100 packets each of size 100 bytes. Therefore total no of send event from all sources are 3600.
Figure 1: Network Model
The simulation is done by using NS-2.34. The radio power values used to compute energy consumption in idle, transmitting, receiving, and sleeping state are in accordance with the RFM TR3000 radio transceiver on Mica Motes .
Simulation parameter and node configuration parameter sets are given in Table 1 and Table 2 respectively.
Table 1: Simulation Parameters
2500m * 1000m
Table 2: Node Configuration Parameters
Radio Propagation Model
Network interface type
AODV and DSDV
Interface Queue Type
Buffer size of IFq
IV Simulation Results and Analysis
Figure 2: Measurement of End-to-end Delay
Figure 3: Comparison of End-to-end Delay
The above figure 2 and 3 shows the measurement and comparison of End-to-End delays. The graph shows that the end-to-end delays in 802.11 with DSDV are lesser than 802.11 with AODV. The graph shows that when interval is small AODV outperforms the DSDV. In graph, for interval one and two the end-to-end delays in case of AODV are better than DSDV but as the interval increase DSDV out performs the AODV. The reason for this kind of behaviour is, DSDV exchanges routing messages with the neighbouring nodes to decide the route and then it will start actual data transfer but in AODV the routing is hop by hop routing. Therefore when interval is small DSDV require time to transfer routing messages to neighbouring nodes and then data transmission. [3, 4]
Figure 4: Measurement of Total Energy
Figure 5: Comparison of Total Energy
The above figure 4 and 5 shows the measurement and comparison of total energy consumption. The graph shows that the total energy consumption in 802.11 with DSDV are slightly lesser than 802.11 with AODV. The energy consumption in both cases increasing linearly. In AODV hello packets are flooded regularly throughout the network. This leads to higher power consumption in AODV than DSDV. [3,4]
Figure 6: Measurement of Per-node Energy
Figure 7: Comparison of Per-node Energy
The above figure 6 and 7 shows the per-node energy consumption in High traffic. Here, too the energy consumption of AODV is higher than DSDV at every node. The reason for this every node will flood routing packets in network and leads to more energy consumption.
Simulation results in the explained network model of industrial environment shows that IEEE 802.11 with DSDV is better option as compared to the IEEE 802.11 with AODV. The end-to-end delays in case of DSDV are lesser than AODV in above mentioned scenario when there is moderate traffic in the network and it also show lesser energy consumption as compared to AODV. From results paper conclude that IEEE 802.11 with DSDV is useful in industrial environment where end-to-end delays and energy consumption should moderate.
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