TE-IT SEM 6 WIRELESS NETWORK

1. Q1. Why network management design is critical issue in WSN? Give reasons.
Or
What are sensor network management design issues? Elaborate any one with example.
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.

2.  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.

3. Q2. Explain in detail components of sensornode.
Wireless sensor networks used for typical purposes like event monitoring, fault detection,
measuring humidity etc. employ large number of sensor nodes. The sensor nodes are
responsible for sensing and processing to some extent as well.
A sensor node is made up of four basic components:
i. Sensing Unit :
 It is usually composed of two subunits: sensors and Analog-to-Digital convertors
(ADC’s).
 Analog signals produced by sensors based on observed phenomenon are converted to
digital signals by ADC, and then fed into processing unit.
ii. Processing Unit :
 It manages the procedures that make the sensor node collaborate with other nodes to
carry out assigned sensing tasks.
 It is generally associated with a small storage unit.
iii. Transceiver:
 It connects the node to the network.
iv. Power Unit:
 Since wireless sensor networks focus more on power conservation than ‘Quality of
Service (QoS)’, it is one of the most important components of a sensing node.
 Power units may be supported by power scavenging units such as solar cells.
 A sensor node can only be equipped with limited power source. (<0.5 Ah, 1.2 V)
There are some other sub-units that are application dependent:
i. Location finding system:
 It is commonly required because most of the sensor network routing techniques and
sensing tasks require knowledge of location with high accuracy.
ii. Mobilizer:
 It may sometimes be needed to move sensor nodes when it is required to carry out
assigned