1. May 21, 2003Wu and Dai, ICDCS 20031 A Generic Distributed Broadcast Scheme in Ad Hoc Wireless Networks Jie Wu and Fei Dai Dept. of Comp. Sci. & Eng. Florida Atlantic University

2. May 21, 2003Wu and Dai, ICDCS 20032 Outline Broadcast Problem & Protocols A Generic Coverage Condition Existing Protocols as Special Cases Simulation Results Conclusions

3. May 21, 2003Wu and Dai, ICDCS 20033 Broadcast Problem & Protocols Promiscuous receive mode Coverage & efficiency Flooding: each node forwards the message once s u v w (a) s u v w (b) s u v w (c)

4. May 21, 2003Wu and Dai, ICDCS 20034 Motivation & Objectives Objective: determine a small set of forward nodes to ensure coverage in a localized way Existing works: different assumptions and models A generic framework to capture a large body of protocols One proof for the correctness of all protocols Address various assumptions/techniques Combine techniques to achieve higher efficiency

5. May 21, 2003Wu and Dai, ICDCS 20035 Classification Probabilistic vs. Deterministic* Deterministic algorithms: forward nodes (including the source) form a CDS CDS: connected dominating set Dominating set: every node in the network has at least one neighbor (dominator) in the DS Non-localized vs. Localized* Self-pruning* vs. Neighbor-designating*

6. May 21, 2003Wu and Dai, ICDCS 20036 Preliminaries: View Unit disk graph: ad hoc network G= (V, E) View: a snapshot of network topology and broadcast state View(t) = (G, Pr(V, t)) Priority: (forwarding status, id) Pr(v, t) = (S(v,t), id(v)), v є V

7. May 21, 2003Wu and Dai, ICDCS 20037 Preliminaries: Forwarding status Forwarding status: time-sensitive visited node (level: 2) vs. unvisited node (level: 1) (past view) Local view: View’, partial view within vicinity visible node vs. invisible node (level: 0) G’ is a subgraph of G and Pr’(V) < Pr(V) time past viewcurrent view broadcast period

8. May 21, 2003Wu and Dai, ICDCS 20038 Pr(v) > Pr(u) based on lexicographical order: visited (2) > unvisited (1) > invisible (0) Global view: {(2, s), (1, u), (2, v), (1, w)} Local 1-hop view of w: {(0, s), (1, u), (2, v), (1, w)} Preliminaries: Priority order s u v w local view of w

9. May 21, 2003Wu and Dai, ICDCS 20039 A Generic Coverage Condition Node v has a non-forwarding status if For any two neighbors u and w, a replacement path consisting of nodes with higher priorities than that of v exists u v w … replacement path

10. May 21, 2003Wu and Dai, ICDCS 200310 A Generic Coverage Condition Proof: Theorem 1 (Wu&Dai, Infocom’03): Forward node set V’ derived based on the coverage condition forms a CDS Each pair of nodes u and v are connected via forward nodes

11. May 21, 2003Wu and Dai, ICDCS 200311 A Generic Coverage Condition Proof :  Forward status f i (v i ) i is computed from G(v i ) and Pr i (V)  Assume f super (v i ) is computed from a global view  G super = (V(v 1 )  V(v 2 )...  V(v n ), E(v 1 )  E(v 2 )...  E(v n ))  Pr super (v i ) = max{Pr 1 (v i ), Pr 2 (v i ),..., Pr n (v i )}  We have f i (v i )  f super (v i ) and {v i |f super (v i )=1} is a CDS  Therefore, {v i |f i (v i )=1} is a CDS Theorem 2: Theorem 1 still holds when different nodes have different local views

12. May 21, 2003Wu and Dai, ICDCS 200312 Timing Issues Static: decision before the broadcast process Dynamic: decision during the broadcast process First-receipt First-receipt-with-backoff s>u>v>x>w vu sw (b) x source vu sw (a) x

13. May 21, 2003Wu and Dai, ICDCS 200313 Selection Issues Self-pruning: v’s status determined by itself Neighbor-designating: v’s status determined by its neighbors Hybrid: The status of v is determined by v and its neighbors

14. May 21, 2003Wu and Dai, ICDCS 200314 Space Issues Network topology information (long lived) Periodic “hello” message K-hop neighborhood information (k=2 or 3) Broadcast state information (short lived) Snooped: snoop the activities of its neighbors Piggybacked: attach h most-recently visited node information (including designated forward neighbors)

15. May 21, 2003Wu and Dai, ICDCS 200315 Priority Issues Pr(v): (forward status, id) 0-hop priority: id(v) 1-hop priority: deg(v) 2-hop priority: ncr(v) ncr (neighborhood connectivity ratio): the ratio of pairs of neighbors that are not directly connected to pairs of any neighbors.

16. May 21, 2003Wu and Dai, ICDCS 200316 A Generic Broadcast Scheme Dynamic approach: dependent on the location of the source and the process of the broadcast process Generic distributed broadcast protocol 1)Periodically v exchanges “hello” messages with neighbors to update local network topology G k (v). 2)v updates priority information Pr based on snooped/piggybacked messages. 3)v applies the coverage condition to determine its status. 4)If v is a non-forward node then stop. 5)v designates some neighbors as forward nodes if needed and updates its priority information Pr. 6)v forwards the packet together with Pr.

17. May 21, 2003Wu and Dai, ICDCS 200317 Existing Protocols as Special Cases Special cases Skipping some steps A strong coverage condition (step 3) Designated forward node selections (step 5) Strong coverage condition v is non-forwarding if it has a coverage set The coverage set belongs to a connected component of nodes with higher priorities than that of v Complexity: O(D 2 ) compared with O(D 3 ), where D is density

18. May 21, 2003Wu and Dai, ICDCS 200318 Static Algorithms (steps 1 and 3) Marking process with Rules 1 &2 (Wu&Li, 1999) with Rule k (Dai&Wu,2003) Span (Chen et al, 2001) 1 23 4 5 6 78 7 23 4 5 6 1 2 3 4 (a)(b) (c)

19. May 21, 2003Wu and Dai, ICDCS 200319 Dynamic and Self-Pruning (steps 1, 2, 3, and 6) SBA (Peng&Lu,2000) LENWB (Sucec&Marsic,2000) 1 2 3 4

20. May 21, 2003Wu and Dai, ICDCS 200320 Dynamic and Neighbor Designating (steps 1,2,4,5,and 6) Multipoint relay (MPR) (Qayyum et al, 2002) Dominant pruning (Lim&Kim, 2001) Total/partial dominant pruning (Lou&Wu, 2003) uv N(v) N 2 (u)

21. May 21, 2003Wu and Dai, ICDCS 200321 Dynamic and Hybrid (new) Designate one neighbor before applying the coverage condition uv N(v) N 2 (u)

22. May 21, 2003Wu and Dai, ICDCS 200322 Simulation Parameters n: node#, 20-100 d: average node degree r: transmission range, adjusted to keep a fixed d (6 or 18) as n varies k: neighborhood radius, e.g., k=2 represents 2- hop information Performance measure : forward node Confidence interval (90%):  1%

23. May 21, 2003Wu and Dai, ICDCS 200323 A Sample Broadcasting n=100, d=6, r=16, k=2

24. May 21, 2003Wu and Dai, ICDCS 200324 Timing Options Performance from worst to best Static First receipt First receipt with backoff delay

25. May 21, 2003Wu and Dai, ICDCS 200325 Selection Options One hybrid algorithm (MaxDeg) outperforms both self-pruning (SP) and neighbor-designating (ND) algorithms.

26. May 21, 2003Wu and Dai, ICDCS 200326 Space Options Larger k has higher performance Using more than 3-hop information cannot improve the performance significantly

27. May 21, 2003Wu and Dai, ICDCS 200327 Priority Options Performance from worst to best id degree ncr

28. May 21, 2003Wu and Dai, ICDCS 200328 Simulated Special Cases CategorySelf- pruning Neighbor- designating StaticRule k, SpanMPR First-receiptLENWBDP,PDP First-receipt- with-backoff SBA Three new algorithms (all labeled as Generic) are derived from the coverage condition, one for each category.

29. May 21, 2003Wu and Dai, ICDCS 200329 Static Algorithms Performance from worst to best MPR Span Rule k Generic

30. May 21, 2003Wu and Dai, ICDCS 200330 First-receipt Algorithms Performance from worst to best Dominant Pruning (DP) Partial Dominant Pruning (PDP) LENWB Generic

31. May 21, 2003Wu and Dai, ICDCS 200331 First-receipt-with-backoff Algorithms Performance from worst to best SBA Generic

32. May 21, 2003Wu and Dai, ICDCS 200332 Conclusions A generic broadcast scheme in ad hoc wireless network Future work Rule of unvisited but designated nodes In-depth simulation using ns-2