Multi-hop Wireless Network: Channel Assignment

1. Multi-hop Wireless Network: Channel Assignment Towards Unified Framework By Raghuram Pidaparthi

2. About… • Introduction • Unified Framework • Graphical Representation • Simulation • Results • Conclusion

3. Introduction • Mobile Ad Hoc Networks • Formed by wireless hosts which may be mobile • Without (necessarily) using a pre-existing infrastructure • Routes between nodes may potentially contain multiple hops

4. May need to traverse multiple links to reach a destination

5. Why Ad Hoc Networks ? • Ease of deployment • Speed of deployment • Decreased dependence on infrastructure

6. Many Applications • Personal area networking • cell phone, laptop, ear phone, wrist watch • Military environments • soldiers, tanks, planes • Civilian environments • taxi cab network • meeting rooms • sports stadiums • boats, small aircraft • Emergency operations • search-and-rescue • policing and fire fighting

7. Multihop Wireless Network • Packet radio networks (PRNs) - DARPA’s PRNet • SURAN • GloMo • AdHoc Networks

8. NP-complete • TDMA Broadcast Scheduling • Link scheduling • FDMA Frequency Assignment • CDMA code assignment

9. Can be modelled by Restricted Graphs? • Trees • Planar graphs • Disc graphs • Planar Point graphs

10. Channel Assignment • Channel assignments to network nodes or to inter-nodal links in a (multihop) wireless network • (T/F/C) DMA <=> U x DMA • Time • Frequency • Code

11. Channel Assignment • Traditional graph coloring problem as a convenient equivalent for channel assignment • Graphs are directed • Based on - Element to be Covered {Vertex or Edge} - Forbidden element separation, {0, 1} - Direction of the constraint (transmitter or receiver) {rr,rt,tr,tt}

12. Assignment Problems • 7 Edge Based Problems • 4 Node Based Problems • 128 possible link assignment and • 16 possible node assignment problems can be captured by this framework

13. Algorithm for Coloring a graph=> Channel Assignment • Input - Topology Graph - set of constraints characterizing the problem

14. Eleven Atomic Constraints

15. Constraint Set

16. Cellular network Frequency Assignment • Adjacent Cells need to be assigned different frequencies. • Vertices represent Cells • Edges represent Cell Adjacency • Two adjacent vertices must receive different Colors => P ID # 1

17. TOCA/ ROCA CDMA Code Assignment • Transmitter Oriented Code Assignment: Node transmits on the code and receiving code agile. • Receiver Oriented Code Assignment: Node receives on this code and transmitting code agile. • In both cases for collision free Tx if a node can hear both A and B then A & B use different codes. PID # 2

18. (T/F)DMA Broaadcast Schedule/Assignment • When a node’s Tx is intended for all its neighbors. • X – time slot/ freq q • Then every Out-neighbor Y of X should not be assigned q since it’ll have to tune to receive on q • Every In-neighbor Z of Y should also not be assigned q to avoid collision at Y.

19. Simulation • Vertex Coloring only • Input: Adjacency Matrix • Input: Constraints

20. Results

21. Conclusion and Future Work • Channel Assignment Problem is researched a lot but not as a unified framework. • Edge Coloring needs to be implemented to consider the other possible Channel Assignment constraints.