Subject : Wireless Network

Topic : Middleware for Sensor Networks

Difficulty : High

The factors that influence the design of routing protocol in WSN / routing challenges in WSN are

1) Node Deployment: Sensor nodes are tightly deployed in the area of interest depending upon the application which affects the presentation of routing protocol. Nodes can be deployed either physically or randomly. When nodes are manually placed data is routed through predetermined paths. In self managing systems, sensor nodes are scattered randomly creating a topology in an ad hoc mode.

2) Network topology: It must be maintained even with high node density.

3) Data aggregation: It is a combination of data from dissimilar sources .Similar packets from multiple nodes can be aggregated to reduce transmission.

4) Transmission media: Usually, communication takes place through wireless media, which is affected by fading.

5) Node Capability: Depending on the application, a sensor node can have a different role or capabilities like as relaying, sensing and aggregation if all these functions are performed by the same node the energy of that node would be drained more rapidly.

6) Scalability: The deployment of sensor nodes is dependent on the nature of the application. Sensor node consumption varies with respect to the demand of the application, therefore the number of sensor nodes can be hundreds, thousand or still more. To handle network scalability, routing algorithm should have the capability to cope with scalable network.

The design of Sensor network is influence by following factors:

1) Fault Tolerance: If sensor nodes fail, MAC and routing protocols must accommodate formation of new links so that sensor node failure should not affect the overall task of the sensor network.

2 Scalability:The number of sensor nodes deployed in the sensing area may be in the order of hundreds or thousands, or more. Any routing scheme must be able to work with this huge number of sensor nodes. In addition, sensor network routing protocols should be scalable enough to respond to events in the environment.

3) Production Costs: The cost of a single node must be low.

4) Hardware Constraint: All Sub units of sensor node (e.g. sensing, processing, communication, power, location finding system and mobilizer) must consume extremely low power and be contained within an extremely small volume.

5) Sensor network topology: It must be maintained even with very high node density

6) Environment: Nodes should be operating in inaccessible location because of hostile environment.

7) Transmission Media: Generally, Transmission Media is wireless (RF or Infrared), which is affected by fading and high error rate and affect the operation of WSNs.

8) Power consumption: The WSN can only be equipped with a limited power source.The lifetime of a node shows a strong dependency on battery lifetime.