16-03-2012, 03:28 PM
ALGORITHM FOR COMMUNICATION IN WIRELESS MULTI-HOP & AD HOC NETWORK USING BROADCAST IN OPPORTUNISTIC LARGEARRAYS
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INTRODUCTION & BACKGROUND
Wireless networks are networks formed by collections of wireless nodes.
A wireless network is ad hoc if each node forwards data from other nodes and produces and consumes data of its own.
Wireless ad hoc networks have been the focus of much recent research, and include Mobile Ad-hoc networks (MANETs), Wireless Sensor Networks (WSNs), Wireless Mesh Networks (WMNs), and Vehicular Ad hoc Networks (VANETs).
Conventional flooding broadcast in wireless ad-hoc net-works has many sources of inefficiency. As for any kind of broadcast, each node has to participate in the communication.
COLLABORATIVE DIVERSITY BROADCASTING (CDB)
lower latency due to fewer hops
lower latency due to not needing a random
jitter to avoid collisions.
better connectivity due to longer hops.
fewer lost packets due to fewer collisions and no self- interference
The fig. shows the topology of point to point
multi hop connections.
ALGORITHM PERFORMANCE
BROADCASTING
Algorithm 1 (broadcast):
1) Complete reception of a packet at time t0
2) Verify that the reception was successful
3) If (the the packet is correct) then
4) Decrement the hop limit field
5) If (the hop limit field > 0) then
6) Retransmit the packet at time t0 + ∆t
7) Remain quiet until t0 + (∆t + tmess ) × hl
NETWORK DIAMETER MULTICASTING,GEOCASTING & SYNCHRONISATION
NETWORK DIAMETER Algorithm 2 (hop limit):
1 broadcast a message with initial hop limit hl = 1, asking any nodes that receive the message to reply using wireless-OR
2 if replies were received, increase the hop limit to hl0 =hl + x and request replies from nodes whose hop count is between hl and hl0
3 if replies are received, set hl to the value of hl0 and repeat step 2, otherwise
4 the last value of hl can reach every node in the network
MULTICASTING,GEOCASTING & SYNCHRONISATION
1 Multicasting is simply a matter of the intended destination nodes processing the message, and all other nodes discarding it after relaying it.
2 Geocasting is local broadcast to nodes within a certain distance of the sender.
3 Even if the network is congested, eventually one packet will be broadcast without collision, and from then on the entire network will be synchronized.