[attachment=11656]
EFFICIENT MULTICAST ALGORITHMS FOR MULTI-RADIO WIRELESS AD HOC NETWORKS
INTRODUCTION
WIRELESS AD HOC NETWORKS
Wireless ad hoc networks consist of mobile nodes connecting over a shared wireless channel. A wireless ad hoc network is a decentralized wireless network. The network is ad hoc because it does not rely on a preexisting infrastructure.
MULTICAST
Multicast provide efficient data distribution among a group of nodes. In wireless ad hoc networks, multicast algorithms are designed to be energy efficient and to achieve optimal route discovery among mobile nodes and also need to optimize the throughput. Multicast is the term used to describe communications where a piece of information is sent from one or more points to set of other points.
Efficient multicast protocols in wireless mesh networks cannot be achieved by adopting or slightly modifying the multicast protocols for other types of multihop wireless networks. This novel approach aim to design a multicast protocol for mesh networks that has the following characteristics
1. It improves the system throughput by allowing
simultaneous close-by transmissions with multi-
channels and multi-interfaces.
2. It assigns all the available channels to the
interfaces instead of just the nonoverlapping
channels
HISTORICAL REVIEW
In order to construct the multicast trees, energy efficient multicast algorithms need to be designed to achieve optimal route discovery among a group of nodes and also it is necessary to solve the multicast problems for wireless ad hoc networks. Researchers proposed the multicast algorithms which are used in the existing scenarios to build the energy efficient multicast structure. Some of the existing multicast algorithms are,
1. Genetic Algorithm (GA)
2. Shortest Path Trees (SPTs) Algorithm
3. Simulated Annealing (SA) Algorithm
4. Minimum Cost Trees (MCTs) Algorithm
5. Tabu Search (TS) Algorithm
6. Multichannel Minimum Number of
Transmissions (MCMNT) Algorithm.
Problems Focused in Existing Multicast Algorithms
 Utilization of partially overlapping channels was not considered, which ultimately reduces the interference and improves the throughput.
 More packet losses to other flows
 Utilization of Multiple channels has not been considered for wireless ad hoc networks.
 Reduction in throughput.
 Higher end-to-end delay.
 Failure recovery mechanism has not been performed to bypass the failed node and restore the connectivity.
 Extensively the existing multicast algorithms have been used to solve the QOS multicast problems but it has not been addressed to solve other multicast problems in wireless ad hoc networks.
PROPOSED WORK
 The proposed algorithms are Level Channel Assignment (LCA) algorithm and Multichannel Multicast Algorithm (MCM).
 These algorithms construct the efficient multicast trees by minimizing the number of relay nodes and hop count distance between the source and destination.
 The algorithms use dedicated channel assignment strategies to improve the network capacity by reducing the interference.
 Network with additional interfaces help to increase the bandwidth, and multiple gateways can further shorten the total hop count distance between source and destination.
LCA ALGORITHM
Algorithmic Steps
1. Initially, the source and all the receivers are included in the
multicast tree.
2. Then for each multireceiver v, if one of its parents is a tree node, then connect it with that tree node and stop the process.
3. If none of its parents is a tree node, then randomly choose one of its parent nodes fv. The selected parent node act as a relay node on the tree
4. Find out the relay node for fv recursively.
5. Repeat the above process until the entire multireceivers are included in the multicast tree.
6. Next. the tree nodes decide their channel assignment with their
level information.
MCM ALGORITHM
Algorithmic Steps
1. Initially, the network topology includes the source and all the multireceivers to construct the multicast tree. Then the network topology is realized by using Breadth first search (BFS), which is similar with LCA algorithm
2. use an approximation algorithm to select the relay nodes in the network topology which are needed to construct the multicast tree. An approximation algorithm includes the following steps.
 some parents are considered as a relay nodes if one of their children has the minimum number of parents
 Among the relay candidates, select the node that has maximal number of children.
3. It intends to minimize the number of relay nodes at the upper level, which can cover all the multireceivers and relay nodes at the lower level. The multichannel multicast tree construction algorithm is otherwise called as “slim” multicast tree construction algorithm because it constructs the “slim” multicast tree.
SIMULATION
Network simulator used to evaluate the performance of Multichannel multicast algorithm (MCM) by comparing it with Level channel assignment (LCA) algorithm and a single channel multicast algorithm through the following metrics.
1. Throughput
2. Delay
3. Packet Delivery Ratio
4. Energy Consumption
5. Network Life Time
6. Network Capacity
Network simulator used to simulate a flat area of 900m by 900m with varying number of randomly positioned wireless router nodes.
Transmission range - 250m.
Carrier sense range - 550m.
Use base rate - 1Mbps
Evaluate the performance of MCM algorithm by comparing it with the LCA algorithm in different scenarios by varying the session rate. The different scenarios such as
1. Impact of Network Size
2. Impact of Number of Channels

3. Impact of Transmission Rate
4. Delay Comparison
5. Partially overlapping channel assigment
test
6. Multiple gateways versus single
geteway
CONCLUSION
• The proposed algorithms such as Level Channel Assignment (LCA) algorithm and Multichannel Multicast (MCM) algorithm used to improve the system throughput and network capacity for multichannel and multi-interface wireless ad hoc networks.
• These algorithms construct the energy efficient multicast tree by minimizing the number of relay nodes and hop count distance between the source and destination. The dedicated channel assignment helps to improve the throughput and also further reduces the interference as well.
• The proposed algorithms significantly improve the network performance by maximizing the network life time and finding a multicast tree with minimizing the energy consumption.
.