1. Netlab Data Networks Lab. Wireless MAC Data Networks Lab. 윤정균 jyun@netlab.snu.ac.kr

2. Netlab Data Networks Lab. 2002-04-232 Outline  Protocols with NCR (Neighborhood-aware Contention Resolution)  NAMA, LAMA, PAMA  IEEE 802.11 MAC Overview  CSMA/CA  IEEE 802.11 for QoS support  Distributed Scheduling  Rate-Adaptive MAC Protocol  RBAR(Receiver-Based Autorate)

3. Netlab Data Networks Lab. Protocols with NCR NAMA, LAMA, and PAMA

4. Netlab Data Networks Lab. 2002-04-234 Contents  Neighborhood-aware Contention Resolution(NCR) Algorithm  Channel Access Protocols  Node Activation Multiple Access (NAMA)  Link Activation Multiple Access (LAMA)  Pairwise-link Activation Multiple Access (PAMA)  Results

5. Netlab Data Networks Lab. 2002-04-235 Neighborhood-aware Contention Resolution  Assumption  Every entity knows the set of its contenders.  Each contention context (time slot) is identifiable  NCR Algorithm (in contention context t) 1. (1) Rand( ) is pseudo-random number 2. Exit unless (2) 3. may access the common channel during

6. Netlab Data Networks Lab. 2002-04-236 Channel Access Protocols  Undirected Graph  Each node is assigned a unique ID number  Remind the Assumption  Nodes already know their neighborhood  Example of Collision Types

7. Netlab Data Networks Lab. 2002-04-237 ① Node Activation Protocol - NAMA  Based on  NCR  Node activation  Distributed time division multiplexing  Time Division in NAMA

8. Netlab Data Networks Lab. 2002-04-238 NAMA Frame Format for Membership  Signal Frame Format in Membership Section  Data Frame Format in Regular Section

9. Netlab Data Networks Lab. 2002-04-239 NAMA Algorithm  NAMA:

10. Netlab Data Networks Lab. 2002-04-2310 ② Link Active Protocol - LAMA  Based on  NCR  Time-slotted code division access using DSSS  Link activation (receiver-oriented code assignment)  Code assignment  Orthogonal code pool  A receiver is assigned a pseudo-noise code by the hashing operation

11. Netlab Data Networks Lab. 2002-04-2311 LAMA Algorithm  The contender set   LAMA:

12. Netlab Data Networks Lab. 2002-04-2312 LAMA Example

13. Netlab Data Networks Lab. 2002-04-2313 ③ Pairwise Link Activation Protocol - PAMA  Based on  NCR  Time-slotted code division access using DSSS  Link activation (transmitter-receiver pair- oriented code assignment)  Contending entities are LINKs, not nodes 

14. Netlab Data Networks Lab. 2002-04-2314 PAMA Algorithm  PAMA:

15. Netlab Data Networks Lab. 2002-04-2315 Results  Fully Connected - Delay

16. Netlab Data Networks Lab. 2002-04-2316 Results  Fully Connected - Throughput

17. Netlab Data Networks Lab. 2002-04-2317 Results  Multihop - Delay

18. Netlab Data Networks Lab. 2002-04-2318 Results  Multihop - Throughput

19. Netlab Data Networks Lab. IEEE 802.11 MAC CSMA/CA & QoS support

20. Netlab Data Networks Lab. 2002-04-2320 CSMA/CA Example SourceDest NAV set Data

21. Netlab Data Networks Lab. 2002-04-2321 Basic Access Method : CSMA/CA

22. Netlab Data Networks Lab. 2002-04-2322 IEEE 802.11 QoS support (IEEE 802.11e 에서 표준화 작업 중 )  Using Backoff time   Replace by.  Using DIFS 

23. Netlab Data Networks Lab. Distributed Scheduling Distributed Priority Scheduling

24. Netlab Data Networks Lab. 2002-04-2324 Contents  Introduction  Distributed Priority Scheduling  Proposed Algorithm  Multi-Hop Coordination  Results

25. Netlab Data Networks Lab. 2002-04-2325 Introduction  Distributed Priority Scheduling  Using piggybacked priority tag  Each node’s scheduling table will be incomplete → define probability q  Multi-Hop Coordination  Better satisfy end-to-end QoS target across multiple nodes

26. Netlab Data Networks Lab. 2002-04-2326 Distributed Priority Scheduling  Two Scheduler  Earliest Deadline First (EDF) → t+d  Virtual Clock (VC) → max(t, p k-1 ) + L/r  802.11 Differentiation  backoff timer distribution  the defer time (DIFS)

27. Netlab Data Networks Lab. 2002-04-2327 Algorithm  Priority Broadcast

28. Netlab Data Networks Lab. 2002-04-2328 Modified Backoff Policies   Effect of q (available information)

29. Netlab Data Networks Lab. 2002-04-2329 Multi-Hop Coordination  Definition   Index Assignment Scheme  Deadline Targets  Time To Live (TTL)  Fixed Per-Node Allocation  Uniform Delay Budget (UDB)  Rate Targets 

30. Netlab Data Networks Lab. 2002-04-2330 Simulation Results  Topology  Delay performance

31. Netlab Data Networks Lab. Rate Adaptive MAC RBAR(Receiver-Based Autorate)

32. Netlab Data Networks Lab. 2002-04-2332 Contents  Introduction  Previous Works  The Lucent ARF Protocol  The RBAR Protocol  Incorporation of RBAR into 802.11  Results

33. Netlab Data Networks Lab. 2002-04-2333 Introduction  Need for Rate Adaptation

34. Netlab Data Networks Lab. 2002-04-2334 The Lucent ARF Protocol  Two consecutive ACKs are not received by sender, then drops the rate  Timer expires or 10 consecutive ACKs are received, then raises the rate

35. Netlab Data Networks Lab. 2002-04-2335 The Receiver-Based Autorate Protocol  Receiver selects the appropriate rate for the data packet during the RTS/CTS packet exchange (more accurate selection)

36. Netlab Data Networks Lab. 2002-04-2336 Overview of the RBAR Protocol  S sends a RTS to R with rate r1 and packet-size n.  A hears the RTS and tentatively calculates the reservation duration.  R selects r2 using channel estimation and sends a CTS.  B hears the CTS and calculates the reservation using r2 and n  S puts r2 in the data packet header and transmits at the rate r2.  A hears the data packet and recalculates the reservation. A S R B r1, n r2, n ACK

37. Netlab Data Networks Lab. 2002-04-2337 RBAR Example SourceDest NAV: Data NAV: 10NAV: 7

38. Netlab Data Networks Lab. 2002-04-2338 Incorporation of RBAR into 802.11

39. Netlab Data Networks Lab. 2002-04-2339 Simulation Results

40. Netlab Data Networks Lab. 2002-04-2340 Multi-Hop Performance

41. Netlab Data Networks Lab. 2002-04-2341 Summary  Protocols With NCR  New Approach → Using 2-hop neighbor inform.  No need to contend or schedule broadcast  Distributed Priority Scheduling  Priority-Based Medium Access  Multi-Hop Priority Access  Rate-Adaptive MAC  A modified version of 802.11  Improve network throughput

42. Netlab Data Networks Lab. 2002-04-2342 References  [Protocols with NCR] Lichun Bao and J.J. Garcia-Luna- Aceves, “A New Approach to Channel Access Scheduling for Ad Hoc Networks,” Mobicom 2001.  [IEEE 802.11] Brian P. Crow, Indra Widjaja, Jeong Geun Kim, and Prescott T. Sakai, “IEEE 802.11 wireless local area networks,” IEEE Communication magazine, September 1997.  [802.11 QoS support] Imad Aad and Claude Castelluccia, “Differentiation mechanisms for IEEE 802.11,” Infocom 2001.

43. Netlab Data Networks Lab. 2002-04-2343 References  [Distributed Scheduling] V. Kanodia, C. Li, A. Sabharwal, B. Sadeghi, and E. Knightly, “Distributed Multi-Hop Scheduling and Medium Access with Delay and Throughput Constraints,” Mobicom 2001.  [Rate-Adaptive MAC] Gavin Holland, Nitin Vaidya, and Paramvir Bahl, “A Rate-Adaptive MAC Protocol for Multi- Hop Wireless Networks,” Mobicom 2001.