Design Principles for Distributed Channel Assignment in Wireless Ad Hoc Networks

1. Design Principles for Distributed Channel Assignment in Wireless Ad Hoc Networks Michele X. Gong, Scott F. Midkiff and Shiwen Mao The Bradley Department of Electrical and Computer Engineering, Virginia Polytechnic Institute and State University IEEE ICC 2005

2. Outline • Introduction • Performance metrics • Design principles • CA-AODV (Channel Assignment AODV) • ECA-AODV (Enhanced CA-AODV) • Analysis of the algorithm • Simulations results • Conclusions

3. Introduction • Channel assignment remains a challenging problem • Existing protocols tend to be complex and usually not suitable for practical implementation

4. Problem formulation • Parameter k • A user-defined neighborhood size • Interference range • k will have an optimal range • Neighbor set • l (v,w) is the distance from v to w

5. Performance metrics (1) • Minimize the average number of nodes sharing the same channel within a node’s k-hop • nk(v) is the number of nodes in Nk(v) that share the same channel

6. Performance metrics (2) • Minimize the summation of interference source • Vt: set of active transmitters • Vr: set of active receivers • : the received power at node vr,i • : 0/1, indicate if nodes are using the same channel

7. Design principles (1) • The use of cross layer design approach • Channel assignment is combined with ad hoc routing • Piggybacking channel information in routing control messages can greatly reduce the complexity of channel assignment

8. Design principles (2) • Channels should be assigned only to active nodes • Most existing schemes assign channel to all nodes • Existing schemes require more wireless channels than necessary

9. Design principles (3) • Distinct channel should assigned in a way the avoids collisions and interference • To resolve one-hop and two-hop interference

10. CA-AODV • Channel assignment in Route discovery phase • Channel info. about a node’s k-hop neighbors on the same route is carried by the broadcast RREQ • Nodes receive RREQ update its next-hop table and indices of used channels • Selects a channel from the available channel list

11. ECA-AODV • Based on CA-ADOV • Add a ChannelTaken message • broadcast in the route discovery phase • Used by a node on an established route detects a new route in the k-hop neighborhood • Use k as the TTL field of the ChannelTaken message

12. ECA-AODV • To allow sufficient time for ChannelTaken messages to propagate to all nodes within k-hops range • Destination or node that has a valid route to the destination should wait for a period of time • Channel assignment is done in the route reply phase

13. Example of ECA-AODV

14. Analysis of the algorithm • Proposition 1: the channels required has an upper bound of n*(k+1) • n: the number of active routes • k: routes lie within k-hop range of any node in the network • Can be proven by induction

15. Analysis of the algorithm • Proposition 2: each along the route is assigned a distinct channel among its k-hop neighbors

16. Algorithm Comparisons

17. Simulation setup • 25 random scenarios • 64 wireless nodes distributed over 800*800 m area • 2-ray ground path lost model • Radio range is 180 m • Static topology

18. Average number of conflicting nodes (C=12)

19. Accumulated interference levels at each receiver (C=12)

20. Impact of neighborhood size on performance (C=18)

21. Conclusions • This paper presented 3 design principles for efficient distributed channel assignment • ECA-AODV exhibits lower communication, computation, and storage complexity than existing channel assignment schemes

22. Thank you!!