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

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

May 21, 2003Wu and Dai, ICDCS 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)

May 21, 2003Wu and Dai, ICDCS 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

May 21, 2003Wu and Dai, ICDCS 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*

May 21, 2003Wu and Dai, ICDCS 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

May 21, 2003Wu and Dai, ICDCS 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

May 21, 2003Wu and Dai, ICDCS 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

May 21, 2003Wu and Dai, ICDCS 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

May 21, 2003Wu and Dai, ICDCS 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

May 21, 2003Wu and Dai, ICDCS 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

May 21, 2003Wu and Dai, ICDCS 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

May 21, 2003Wu and Dai, ICDCS 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

May 21, 2003Wu and Dai, ICDCS 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)

May 21, 2003Wu and Dai, ICDCS 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.

May 21, 2003Wu and Dai, ICDCS 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.

May 21, 2003Wu and Dai, ICDCS 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

May 21, 2003Wu and Dai, ICDCS 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) (a)(b) (c)

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

May 21, 2003Wu and Dai, ICDCS 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)

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

May 21, 2003Wu and Dai, ICDCS Simulation Parameters n: node#, 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%

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

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

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

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

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

May 21, 2003Wu and Dai, ICDCS 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.

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

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

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

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