1. Smartening the Environment using Wireless Sensor Networks in a Developing Country Presented By: Al-Sakib Khan Pathan A Neighbour Discovery Approach for Cognitive Radio Network Using Tower of Hanoi (ToH) Sequence Based Channel Rendezvous Md. Rafiqul Islam 1, M.A.E. Shakib 1, Md. Azizur Rahaman 1, Md. Obaidur Rahman 1, and Al-Sakib Khan Pathan 2 1 Department of Computer Science and Engineering, Dhaka University of Engineering & Technology, Gazipur, Bangladesh 2 Department of Computer Science, International Islamic University Malaysia, Kuala Lumpur, Malaysia

2. Outline of This Presentation Introduction Problem Statement and Related Works ToH based Channel Hopping and Rendezvous Performance Evaluation Conclusions and Future Works 2 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

3. Introduction Cognitive Radio Network (CRN) is a relatively new research area to improve spectral efficiency of wireless communication. Nowadays, the concept of commercial CRN (i.e., existence of primary and secondary users in licensed bands) is gaining popularity in wireless communication research. 3 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

4. Introduction (Ctnd.) In CRN, two types of users namely Primary User (PU), the owner of licensed band; and Secondary User (SU) (shown in Figure 1), of the unlicensed ISM band coexist. At the absence of PUs in licensed bands, opportunistic medium access by SUs in licensed channels renders better bandwidth provisioning. 4 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

5. Primary & Secondary Networks 5 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

6. Overview and Objective In CRN, SUs search the channels dynamically and use the obtainable channels to enhance throughput and connectivity. If two neighbour SUs want to communicate, both should operate on at least one available common channel during a particular interval of time. Hence, both SUs can discover each other, exchange control information and negotiate for further data communication using MAC protocols like IEEE 802.11. 6 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

7. Overview and Objective (Ctnd.) Since the SUs operate independently on different channels based on availability (i.e., during the absence of PUs), channel rendezvous seems to be the most challenging issue in CRN. 7 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

8. SU Channels 8 Secondary users (SUs) may operate on various channels freely, at any given time. This figure shows that nodes a and b, p and q, x and y; the pairs of SUs opportunistically make channel rendezvous on channel 1, channel 2, and channel 4, respectively, where no primary user exists. Note that channel 3 is occupied by the PU; hence, SUs do not have any activity on that channel. ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

9. Message Broadcasting 9 In this procedure, to find neighbours in CRN, an SU broadcasts a control message (i.e., informing its presence) first on one channel and nodes those get that message repeatedly broadcast the same information over multiple channels. Effectiveness and Performance are questioned Procedure of message broadcasting using channel hopping. ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

10. Common Control Channel (CCC) 10 In CCC approach, one common channel is selected from the available channel list and used as rendezvous channel. ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

11. Pseudo Random Hopping 11 The channel hopping sequence as presented here, each SU generates a pseudo random sequence and switches/hops from one channel to another by following that predefined hopping sequence. Pseudo random hopping sequence for SU x and y; where channel rendezvous occurs on a channel (Ch-2) after ten iterations. ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

12. Tower of Hanoi (ToH) In Tower of Hanoi (ToH) (sometimes referred to as the Tower of Brahma or the End of the World Puzzle), different sized disks are initially placed in a first tower (initial) and all the disks are needed to be shifted to a third tower (target), taking help of a second tower (intermediate). At each of the tower and during disk movements, a large disk should be placed under a smaller disk. 12 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

13. Tower of Hanoi (ToH) 13 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

14. Our Proposal We assume the disks of the ToH as the available channels to the SUs of a CRN. The number of disks equals to the number of available channels, denoted by n. Larger numbered channel is considered to be the larger disk and a smaller numbered channel is considered to be the smaller disk, and so on. Therefore, the disks’ movement sequence that we get using ToH method will actually provide a channel hopping sequence for the SUs. 14 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

15. Our Proposal (Ctnd.) Let, n disks (channels) need to be moved from first tower (initial) to third tower (target) with the help of second tower. Start Condition for Generating Sequence: –Transfer all the n disks from first tower to third tower. –Move only one disk at a time and store the disk ID (identity) in a sequence. –A large disk may not rest on top of a smaller one. 15 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

16. Our Proposal (Ctnd.) End Condition for Generating Sequence: –Add and store the sequence of disk movement whenever one disk needs to be moved from one tower to another tower. –The largest disk can only go to an empty tower. –Similarly, transfer all the n disks from first tower to third tower. –All transfer sequence will complete within (2 n -1) steps. –Finally, derive the sequence when the largest disk is in the bottom and smallest disk is on the top of third tower. 16 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

17. Our Proposal (Ctnd.) Let us assume that n = 3, so the ToH hopping sequence will form a cycle having a length of seven (i.e., using (2 n -1)). Based on the example given, if a particular SU has three available channels namely, 1, 2, and 3; then, ToH provides the channel hopping sequence as 1-2- 1-3-1-2-1 having a cycle length of seven. ToH based sequence. 17 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

18. Channels and Length of Cycle 18 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

19. Flaw of Pseudo Random Seq. Suppose, a secondary user x has four available channels (1, 2, 3, and 4) and y has two available channels (2 and 5). So, channel 2 is common between x and y. If x and y maintain the pseudo random sequence of the figure, even after twelve iterations, no possibility of channel rendezvous between SUs x and y occurs. 19 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

20. ToH based Sequence Let us consider the similar scenario and generate the proposed ToH sequence as in this figure. The SU x has four available channels (1, 2, 3 and 4) and the ToH sequence is 1-2-1-3-1-2-1-4-1-2-1-3-1-2-1 with a cycle length of fifteen. In contrast, y has two channels (2 and 5) with a ToH sequence of 2-5-2 having a cycle length of three. Since, the cycle replicates again and again, in ToH based method, channel rendezvous between x and y occurs within six iterations. 20 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

21. Flaw of Basic ToH Seq. Problem in the proposed ToH based hopping sequence for x and y; where channel rendezvous does not occur on channel (Ch-4). 21 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

22. Channel Sequence Shifting Channel Sequence Shifting. In the adaptive module, if any node is not able to make channel rendezvous for several iterations, it would presume that the generated ToH sequence is not allowing it to make channel rendezvous with other nodes. Therefore, considering the original ToH sequence as an origin, it will make a 1-bit left-shift in its channel sequence. However, even after 1-bit left-shift, if channel rendezvous does not occur, then the node will make 1-bit right-shift in its channel sequence from the origin. 22 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

23. Performance Analysis 23 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

24. Performance Analysis (Ctnd.) Comparison of number of iterations required for channel rendezvous, (a.) No. of Channels for Receiver = 2 24 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

25. Performance Analysis (Ctnd.) 25 Comparison of number of iterations required for channel rendezvous, (b.) No. of Channels for Receiver = 3 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

26. Performance Analysis (Ctnd.) 26 Comparison of number of iterations required for channel rendezvous, (c.) No. of Channels for Receiver = 4 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

27. Performance Analysis (Ctnd.) Comparison of success rates of channel rendezvous. 27 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

28. Final Words and Future Works The proposed approach is a novel one that uses Tower of Hanoi (ToH) principle to derive the channel hopping sequence for the SUs. It provides less number of iterations for channel rendezvous with a higher success rate than that of the existing pseudo random based approach, which could be the apparent best alternative. In future, we aim to extend the work toward a complete medium access solution for Cognitive Radio Network. 28 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

29. THANK YOU 29 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.

30. Questions and Answers Any query should be directed to sakib.pathan@gmail.com, sakib@iium.edu.my ??? For More Information: http://staff.iium.edu.my/sakib/ 30 ICT4M 2014, Nov. 17-19 2014, Kuching, Malaysia.