Networking Issues in
Souhaiel Ben Tekaya
fields(forest, military, surveillance, transportatio
• Emerging field in different
• Role: collect data then transfer it to central
• Focus on fundamental issues:
• Limited energy supply,
• limited computing power,
• limited bandwidth of the wireless links connecting data.
• Differs from classic networks on :
• Routing challenges:
• Data aggregation,
• Coverage/ scalability,
• Data reporting methods (protocols).
Critical task since we need to consider some factors:
• Node heterogeneity,
• Node failure tolerance,
• Quality of service,
• Design issues:
Prevent connectivity degradation by employing energy
Networking issues (protocols)
• Use position of routers & packet destination to make forwarding
• Sensitive to rate of change of the network and number of routers
in the network.
• 2 algorithms:
• Greedy perimeter stateless Routing (GSPR):
• Greedy forwarding: decision made locally (node) based on closest
node to destination.
• Perimeter forwarding: when previous not applicable. Chooses one of
the surrounding nodes based on the right hand rule.
• Consider energy factor and avoid flooding packets.
1. packet outside region:
• Geographical and Energy Aware Routing (GEAR)
routing with energy aware metrics (calculate the less
energy consuming way to destination)
2. Packet within region:
restricted flooding algorithm
Power conservation while
maintaining multi-hop routing
consumer in a sensor.
• the transceiver is considered the largest energy
• Powering off the sensor will be the best way.
But, areas in the sensor network will be isolated
and inaccessible by queries.
• Most proposed solution: Duty-cycling.
Duty-cycling exploit node redundancy in sensor network, by putting
in a sleep state all unnecessary sensors for connectivity.
Sleep and wake-up: independent from the network topology and
low duty cycle combined with MAC protocols: integrated in the
duty-cycle control through topology management: Exploiting the
dense aspect of sensor networks.
a. Sleep and wake-up
independent from the network topology and MAC protocol.
• On-demand: wakeup only when another node wants to talk with it
using two different radios.
• Scheduled rendezvous: closed node are wakeup at exactly the
• Asynchronous schemes: nodes wakeup independently while always
guaranty an overlapped active period
b. low duty cycle combined with
• TDMA-based: channel access is done on a slot-by-slot
basic, Bluetooth and LEACH are two examples.
• Contention-based: similar to sleep/wakeup scheme, integrating the
sleep/wakeup algorithm to the MAC protocol.
• Hybrid protocols: combines both TDMA and contention protocols.
c. duty-cycle control through
• Exploiting the dense aspect of sensor networks.
• Most common protocols:
GAF: divide the network to fixed square grids.
SPAN: sleep state or to join the backbone upon the connectivity
information given by the routing protocol.
ASCENT: packet loss and connectivity information.