self-organizing media access mechanism of a wireless sensor network ahm quamruzzaman

SELF-ORGANIZING MEDIA ACCESS MECHANISM OF A WIRELESS SENSOR

NETWORK

AHM QUAMRUZZAMAN

Sensor Networks

Composed of large number of sensor nodes. Nodes are able to communicate in short

distance Limited energy Limited storage, processing power Multi-hop topology

Application

Useful to extract and monitor data Randomly deployed for military surveillance Widespread environmental sampling Health monitoring

Important Issue

Power conservation and management are most important factors

Quality of service and bandwidth efficiency are secondary issue

An improved low-power scalable self-organization protocol will be desirable

Sensor Network Challenges

Major drawback- limited energy Topology changes very frequently Hardware design challenge Scalability Prone to failure Broadcast communication Cost

Sensor Network vs. other Wireless Network

A cellular network – composed of stationary and mobile nodes.– The network has infrastructure– The base station has unlimited power– The base station covers a wide range– Main objective- quality of service with high

bandwidth


Mobile ad hoc Network (MANET)– Peer-to-peer network– Consists of 10 to 100 nodes– Main objective- quality of service– Energy resource is secondary important


Bluetooth technology– Enables wireless link among electronic devices– One master and can support up to seven devices

within its network to form a piconet– All nodes are synchronized to master– Low power and low data rate– TDMA protocol


Sensor network is different from all of these networks– Main objective- power management– It may have a much larger of nodes– Transmission power and radio range are much

less than Bluetooth and MANET– Mobility rates are much slower than MANET

Media Access Control (MAC)

Self-organization capability– Ability of the system to function properly without

human assistance– It enable nodes to coordinate among themselves

to achieve a large sensing task with little energy usage


Transmission Media:– Optical Media – Infrared – Radio

Channel access is done by two different methods:– Contention based protocol– TDMA based protocol


Nodes power saving technique– Letting the nodes sleep whenever possible– Nodes go into the idle mode when it has nothing

to do– Idle node consumes the same energy as the

active node– Proper choice of protocols will be able to turn off

and on the radio when necessary


Scalability of nodes Error control

– Forward Error Correction (FEC)– Automatic Repeat Request (ARQ)

Traditional MAC Protocols

CSMA Scheme MACA and MACAW CSMA with collision detection and Slotted

ALOHA IEEE 802.11 Bluetooth based protocol

Current Survey of MAC Protocol for Wireless Sensor Network

Sohrabi and Pottie proposed S (Stationary)-MAC– TDMA based protocol– Power conservation achieved by using random

wakeup schedule and by turning off the radio during idle times.

– Limitation: low bandwidth utilization


Adaptive transmission control (ARC) proposed by Woo and Culler– In ARC mechanism, node periodically attempts to

inject the packet. – If the packet is not injected successfully, it signals

that the road is jammed.– So the node can reduce the transmission rate.


DE-MAC, distributed energy-aware protocol– treats the critical nodes differently – Criticality depends on the relative energy levels

within the neighboring nodes.– Protocol performs a local election process to

select the weaker nodes and make them sleep.– Low energy nodes sleep more than high energy

nodes and increases energy saving.


Sensor MAC protocol proposed by Heidemann and Estrin– Nodes go into periodic sleep. – During the sleep, nodes turn off the radio– Also sets the nodes sleep during the transmission

of other nodes– To prevent collision and overhearing, it uses

802.11 contention based mechanism (RTS/CTS)

Comparative Performance

MAC Protocol

Media Access Mode

Power Saving technique

Limitations

Stationary MAC

TDMA Random wake up schedule during connection phase and by turning off the radio during idle time

Low bandwidth utilization

ARC (Adaptive Transmission Control Scheme)

Contention Based

By constant listening and random delay

Emphasize on fair bandwidth allocation to all nodes rather than saving on energy nodes

MAC Protocol

Media Access Mode

Power Saving Technique

Limitations

DE-MAC TDMA By selecting critical nodes and let the critical nodes to sleep more than neighbor nodes

Protocol does not treat all nodes equally

Sensor MAC

Contention based.

Nodes go into periodic sleep by turning off the radio

Latency increases

Conclusion

Many important research questions remain regarding prolong lifetime of nodes

Current error detection control scheme are not enough

Future research must satisfy fault tolerance, scalability, cost, hardware, topology change and power consumption.

THANK YOU

self-organizing media access mechanism of a wireless sensor network ahm quamruzzaman

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