1. ADHOC MAC : a new, flexible and reliable MAC architecture for ad- hoc networks F. Borgonovo, A. Capone, M. Cesana, L. Fratta Dipartimento Elettronica e Informazione Politecnico di Milano IEEE Wireless Communications and Networking Conference (WCNC) 2003 Speaker : Wey-Yu Ruo

2. Outline Introduction ADHOC-MAC protocol Simulation Conclusion

3. Introduction Motivation and Objective Avoid some problem like hidden terminal and exposed terminal problem in distributed network, and provide more reliable environment for data transmission Solution ADHOC-MAC protocol

4. ADHOC-MAC Terminology Virtual frame a time slot structure for each station to declare a slot as its usage Frame Information packet beside payload transmitted by terminals to report its knowing of status of slots usage Sliding Virtual Frame Virtual frames which has different offsets in time slots Time axis Empty Busy b avail b c a b a a ba b a c

5. ADHOC-MAC (cont.) ADHOC-MAC protocol Principles Use time-slot structure Every terminal that want to transmit in a certain time slot. It should contend for it with other terminals that want to use it. Use virtual frames (VF) to contend for a certain time slot, and also mention others terminal the status of time-slot. Other terminals receive frame information (FI) in VF reserve the time-slot in their own VF that is claimed BUSY in other ’ s VF Four states of slot : AVAILABLE, BUSY, FREE, and RESERVED

6. ADHOC-MAC (cont.) RR-ALOHA protocol Rule 1 The slots are labeled as RESERVED if coded as BUSY in at least one one received FIs; else it is labeled as AVAILABLE Rule 2 The transmission is successful if the slot is coded as BUSY for station j in all received FIs; otherwise, the transmission fails

7. ADHOC-MAC (cont.) Reserving additional bandwidth Rule 3 A terminal set the PTP flag in the FI if the received packets is a broadcast packets or it’s destined to terminal itself Rule 4 Let S be the ID of the accessing node and D the ID of its intended destination. Then RESERVED slot can be accessed if The PTP flag signaled in all the received FIS is off and The FI received from D signals the slots as FREE Rule 5 The transmission is successful if the slot is coded as BUSY in the FI of the destination terminal; Otherwise, the transmission fails

8. ADHOC-MAC (cont.) Multi-hop broadcast service Rule 6 Terminal i decides to relay the packet if and for all j the following condition is not satisfied :

9. 1 2 3 4 6 7 8 5 2 4 6 3 3 1 5 A C B 2 Instance

10. 2 45 6 5 1 2 4 7 6 3 5 1 7 A B C 3

11. 2 45 6 1 2 4 5 1 1 7 A B C 3

12. 2 45 6 2 4 6 3 5 1 2 1 7 A B C 3

13. 2 45 6 7 6 3 5 1 2 4 1 7 A B C 3

14. 2 45 6 7 6 5 4 7 1 7 A B C 3

15. 2 45 6 5 1 2 4 7 6 3 5 1 7 A B C 3

16. 2 45 6 1 7 A B C 3

17. 2 45 6 1 7 A B C 3

18. 2 45 6 1 7 A B C 3

20. Solution of exposed terminal (1/4) A B C (BUSY,OFF)

21. Solution of exposed terminal (2/4) A B C (BUSY,ON) Hidden terminal

22. Solution of exposed terminal (3/4) A B C (BUSY,OFF)

23. Solution of exposed terminal (4/4) A B C (BUSY,OFF) Exposed terminal

24. Simulation Environment M (maximum number of terminals) = 100 N (number of slots in the frame) = 200 Frame field in virtual frame BUSY status (1 bit) Source temporary id identifying station capturing a slot successfully : (8 bits) Priority field (2 bits) PTP service flag (1 bit)

25. Simulation Method Possibility for a contending terminals gains access k : contending terminals p : the probability that new terminal that is willing to set up a channel will attempt transmission in next AVALABLE slot

27. Conclusion ADHOC-MAC has proposed a solution to solve the some problems like hidden terminal problem and exposed terminal problem in distributed network environment. More reliable environment for data transmission.