1. Initialization Protocols for IEEE 802.11 Based Ad Hoc Networks C. – S. Hsu and J. P. Sheu International Conference on Parallel and Distributed Systems (ICPADS), Dec. 2002 Speaker: Chien-Wen Chang

2. Outline Introduction Preliminaries Leader Election and Initialization Protocols Simulation Results Conclusion Discussion

3. Introduction The leader can serve as a coordinator a relay point a reporter The initialization protocol can assign each host a unique id two contention-based protocols

4. Preliminaries(1) The Nakano-Olariu Protocols Type 1: with the collision detection capability do the Initialization Protocol Type 2: without the collision detection capability do the Leader Election Protocol elect a leader to serve as a detector

5. Preliminaries(2) The Leader Election Protocol by contention probability: ½, ¼, …… do until a host is declared as a leader

6. Preliminaries(3) The Initialization Protocol Type 1: with the collision detection and the number of host in advance Type 2: without the later knowledge Type 1: get their ids by contention n-m+1 as its id probability: 1/m, m is the number of hosts without ids

7. Preliminaries(4) Type 2: by contention partition tree {a, b, c, d} {a, d} {b, c} {d}{a}{b, c} {b} {c} Ø

8. Leader Election and Initialization Protocols Two efficient protocols protocol 1 the number of hosts is known in advance protocol 2 without the knowledge of the number of hosts For single-hop MANET

9. Protocol 1 (1) The Leader Election Protocol elect a leader to serve as coordinator help to initialize a MANET follows a DCF procedure to contend as a leader CW is set according to the number of hosts will not contend again until election round is over

10. Protocol 1 (2) The Leader Election Protocol (cont.) flow chart of one election round Ha: the host first broadcast its MAC address successfully

11. Protocol 1 (3) other hosts Ha Sets backoff timer no leader and backoff timer has expired broadcasts its MAC addr. receives the ack ? waits for ack waits SIFS and announces itself as the new leader the Leader Election Protocol is completed YES NO Set backoff timer backoff timer has expired and receive the Ha ’ s MAC addr. return ack (broadcast the Ha ’ s MAC addr.) no collision ? YES NO wait for the Ha ’ s announce contend to re-broadcast its MAC addr. at the next election round contend to re-broadcast the ack at the next election round if all hosts failed to return ack

12. Protocol 1 (4) Example 8 hosts: A, B, C, D, E, F, G, H CW: 8 ST (backoff time slot) the backoff timers of hosts B, C: 0 ST F: 2 ST A, E: 3 ST D, H: 4 ST G : 6 ST

13. Protocol 1 (5) DIFSDIFS BCBC DIFSDIFS F DIFSDIFS AEAE DIFSDIFS DHDH DIFSDIFS G SIFSSIFS F (co mp let e) backoff time slot1 2 3 4 5 6 (broadcasts F ’ s MAC addr. successfully) contend to serve as leadercontend to broadcast the ack F announces itself as the leader G sends ack successfully

14. Protocol 1 (6) The Initialization Protocol with the help of leader CW is set as described above follows DCF to send a request id message to leader be repeatedly executed until all hosts have got ids exception r 1 : the number of hosts without ids before executing the protocol r 2 : the number of hosts without ids after executing the protocol

15. Protocol 1 (7) Example 4 hosts: A, B, C, D Host A is the leader with id=1 CW: 2 ST (backoff time slot); 1 ST in the second round the backoff timers of hosts B: 2 ST; 1 ST in the second round C: 0 ST D: 2 ST; 0 ST in the second round

16. Protocol 1 (8) DIFSDIFS C SIFSSIFS Id (=2) DIFSDIFS BDBD DIFSDIFS D SIFSSIFS Id (=3) DIFSDIFS B SIFSSIFS Id (=4) backoff time slot 1 2 1 |--First round --|-- Second round --| Host A broadcasts C ’ s id(2) mess. successfully) send the request id mess. successfully B, D reset their backoff timer collision of two request id mess. send the request id mess. successfully

17. Protocol 2 (1) follow the same protocol described in Protocol 1 The Leader Election Protocol exception First, the CW value is predetermined the rule of setting the CW value be doubled until 256

18. Protocol 2 (2) The Initialization Protocol exception First, the CW value is also predetermined After a round, the CW value is set according to the estimated number of hosts without ids

19. Simulation Results(1) develop a simulator using C transmission rate: 2M bits/sec DIFS: 50  s SIFS: 10  s ST: 20  s the number of hosts: 20~100

20. Simulation Results(2) proposed protocols K: with the knowledge of the number of hosts U: without it

21. Simulation Results(3)

22. Simulation Results(4)

23. Simulation Results(5)

24. Conclusion proposed two Leader Election Protocols and Initialization Protocols The first Protocols for IEEE 802.11- based single-hop MANETs more efficient than Nakano-Olariu Protocols can be easily implemented in IEEE 802.11-based WaveLAN cards

25. Discussion Simulation results In single-hop with multiple channels Tone for leader ’ s ack for omitting The Leader Election Protocols In multihop MANETs