May 21, 2003 Wu and Dai, ICDCS 2003 1

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, 2003 Wu and Dai, ICDCS 2003 2

Outline Broadcast Problem & Protocols A Generic Coverage Condition Existing Protocols as Special Cases Simulation Results Conclusions

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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)

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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

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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*

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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

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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)

timepast view current view

broadcast period

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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

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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

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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

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A Generic Coverage Condition

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

Theorem 2: Theorem 1 still holds when different nodes have different local views

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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

sw

(b)

xsource

v u

sw

(a)

x

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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

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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)

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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.

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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 Gk(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.

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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

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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

2 34

5 6

7 8

7

2 3

4

5 61 2

34

(a) (b) (c)

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Dynamic and Self-Pruning (steps 1, 2, 3, and 6)

SBA (Peng&Lu,2000) LENWB (Sucec&Marsic,2000)

1

2

3

4

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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)

u v

N(v)

N2(u)

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Dynamic and Hybrid (new)

Designate one neighbor before applying the coverage condition

u v

N(v)

N2(u)

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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%

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A Sample Broadcastingn=100, d=6, r=16, k=2

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Timing Options

Performance from worst to best Static First receipt First receipt with backoff delay

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Selection Options

One hybrid algorithm (MaxDeg) outperforms both self-pruning (SP) and neighbor-designating (ND) algorithms.

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Space Options

Larger k has higher performance Using more than 3-hop information cannot

improve the performance significantly

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Priority Options

Performance from worst to best id degree ncr

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Simulated Special CasesCategory Self-

pruningNeighbor-designating

Static Rule k, Span

MPR

First-receipt

LENWB DP,PDP

First-receipt-with-backoff

SBAThree new algorithms (all labeled as Generic) are derived from the coverage condition, one for each category.

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Static Algorithms

Performance from worst to best MPR Span Rule k Generic

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First-receipt Algorithms

Performance from worst to best Dominant Pruning (DP) Partial Dominant Pruning (PDP) LENWB Generic

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First-receipt-with-backoff Algorithms

Performance from worst to best SBA Generic

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Conclusions A generic broadcast scheme in ad hoc

wireless network Future work

Rule of unvisited but designated nodes In-depth simulation using ns-2