Requirement of NM in WSN:
WSN is a special type of wireless network
• Possibly with ad hoc structure and
• Probably with limited resources.
Due to these WSN constraints networking protocols, the application model, middleware and sensor node OS (operating systems) should be designed very carefully. So here, Network management for WSNs is required to use those limited resources effectively & efficiently.
Importance of NM in WSN: is for following reasons. (Design Issue)
In order to deploy an Adaptive and Resource-Efficient algorithm in WSNs, the current resource level needs to be gathered through network management. For example the power availability should be known before switching a sensor node from active (or sleep) mode to sleep (or active) mode. Most traditional networks do not have these requirements.
Collaboration and Cooperation between sensor nodes are required to optimize system performance.
Most WSN applications need to know the coverage area so that they ensure that the entire space is being monitored. Topology management can be used in case an uncovered area is detected. Approaches to increasing the coverage area:
a. Increase the node's radio power,
b. Increase the density of deployment of senor nodes, and
c. Move the sensor nodes around to achieve equal distribution.
- Nodes in WSNs are usually arranged in an ad hoc manner. The parameters of this ad hoc network are obtained by the network management system. Network management is an effective tool to provide the platform required for this purpose.
Transport Proctocol Design Issues:
- WSNs should be designed with an eye to energy conservation, congestion control, reliability in data dissemination, security and management.
- Congestion control may involve only the transport layer, but energy conservation may be related to the physical, data link, network, and perhaps all other high layers.
- Generally, transport control protocols' design include two main functions: Congestion Control and Loss Recovery.
The design of transport protocols for WSNs should consider the following factors:
i. Perform congestion control and reliable delivery of data.
ii. Since most data are from the sensor nodes to the sink, congestion might occur around the sink. WSNs need a mechanism for packet loss recovery, such as ACK and selective ACK used in TCP.
iii. It may be more effective to use a hop-by-hop approach for congestion control and loss recovery since it may reduce packet loss and therefore conserve energy.
iv. The hop-by-hop mechanism can also lower the buffer requirement at the intermediate nodes.
v. Transport protocols for wireless sensor networks should simplify the initial connection establishment process or use a connectionless protocol to speed up the connection process, improve throughput and lower transmission delay.
vi. Transport protocols for WSNs should avoid packet loss as much as possible since loss translates to energy waste.
vii. To avoid packet loss, the transport protocol should use an Active Congestion Control (ACC) at the cost of slightly lower link utilization.
viii. The transport control protocols should guarantee fairness for a variety of sensor nodes.
ix. If possible, a transport protocol should be designed with cross-layer optimization in mind.
x. For example, if a routing algorithm informs the transport protocol of route failure, the protocol will be able to deduce that packet loss is not from congestion but from route failure.