A Generic Distributed Broadcast Scheme in Ad Hoc Wireless Networks

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

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

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

4. 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 Wu and Dai, ICDCS 2003

5. 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* Wu and Dai, ICDCS 2003

6. 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 Wu and Dai, ICDCS 2003

7. 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) broadcast period time past view current view Wu and Dai, ICDCS 2003

8. Preliminaries: Priority order • 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)} u local view of w w s v Wu and Dai, ICDCS 2003

9. 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 replacement path u w … v Wu and Dai, ICDCS 2003

10. 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 Wu and Dai, ICDCS 2003

11. A Generic Coverage Condition Theorem 2: Theorem 1 still holds when different nodes have different local views Proof: • Forward status fi(vi)i is computed from G(vi) and Pri(V) • Assume fsuper (vi) is computed from a global view • Gsuper = (V(v1)  V(v2) ...  V(vn), E(v1)  E(v2) ...  E(vn)) • Prsuper (vi) = max{Pr1(vi), Pr2(vi), ..., Prn(vi)} • We have fi(vi)fsuper (vi) and {vi|fsuper (vi)=1} is a CDS • Therefore, {vi|fi(vi)=1} is a CDS Wu and Dai, ICDCS 2003

12. 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 v u x v u x source w s w s (a) (b) Wu and Dai, ICDCS 2003

13. 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 Wu and Dai, ICDCS 2003

14. 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) Wu and Dai, ICDCS 2003

15. 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. Wu and Dai, ICDCS 2003

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

17. 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(D2)compared with O(D3), where D is density Wu and Dai, ICDCS 2003

18. 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) 7 1 1 5 5 2 6 6 4 2 3 2 3 4 3 4 7 8 (a) (b) (c) Wu and Dai, ICDCS 2003

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

20. 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) N2(u) N(v) u v Wu and Dai, ICDCS 2003

21. Dynamic and Hybrid (new) • Designate one neighbor before applying the coverage condition N2(u) N(v) u v Wu and Dai, ICDCS 2003

22. 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% Wu and Dai, ICDCS 2003

23. A Sample Broadcastingn=100, d=6, r=16, k=2 Wu and Dai, ICDCS 2003

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

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

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

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

28. Simulated Special Cases Three new algorithms (all labeled as Generic) are derived from the coverage condition, one for each category. Wu and Dai, ICDCS 2003

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

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

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

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