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A Distributed Architecture for Multimedia in Dynamic Wireless

Networks

By UCLA C.R. Lin and M. GerlaIEEE GLOBECOM'95.

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Outline

IntroductionDefinitionsThe Multicluster Architecture and its PropertiesAdaptive Routing for Real-Time TrafficConclusionDiscussion

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Introduction

To support multimedia services (voice, data, video, and image) Real-time traffic (voice, video) delay-sensitiveBursty traffic (data, image) error-sensitive

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Definition Definition 1:

(System Topology) Is a graph G=(V,E)

V is the set of nodes E is the set of edges

One transceiver (half-duplex) in each node

Definition 2: (Distance of Two Nodes) Distance d (x ,y )

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Definition(cont.)

Definition 3: (Cluster) Ci V is a set of nodes Ci: A cluster

V = and Ci ∩ Cj = , if i ≠ j

x , y Ci , d (x ,y )≤ 2

Definition 4: (Center and Radius of a Cluster) How to choose center(xo) in Ci

d (x,y), x,y Ci d (x0,y) is called the radius of a cluster

i

iC

maxy

maxminyx

3

2

1

113

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Definition(cont.)

Definition 5: (Degree of Topology)

Is the number of clusters in a topology ( )

Definition 6: Repeater Bridge u=(x,y) The Order of a Repeater

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Definition(cont.)

Definition 7: (Bridge Partially in a Cluster) 1 1 1

)()()( CCC www

:)(Cw

:)(Cw

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The Multicluster Architecture and its Properties (cont.)

Centralized Clustering Algorithm:0. i = 01. x = min(V )2. Ci = {x } ∪ Γ1(x )

V = V – Ci

E = E – ω(Ci )

3. If V ≠ then i = i + 1 and goto 1; else stopΓ1(x ) be the set of one-hop neighbors of x

C0

x

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The Multicluster Architecture and its Properties (cont.)

Robust Cluster structure Because can Re-cluster approach

d (1,4)=d (0,4)= 3>2 Find a highest degree node and its

neighbors to stay in the original cluster to as a center, and remove the other nodes

The other nodes should either join another cluster or form a new cluster

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Adaptive Routing for Real-Time Traffic

Objective Real-time traffic can to transmit over the

dynamic network, and the routing protocol is keep communication

The routing optimality is of secondary importance

Choose a hierarchical routing protocol

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The Two-level Hierarchical Routing Protocol

Route construction and Route maintenance The construction phase establishes an initial

set of routes The maintenance phase maintains loop-free

routing in the face of arbitrary topological changes

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The Two-level Hierarchical Routing Protocol(cont.)

Construction Phase Assume every node has no global

connectivity information, but keeps some information of its locality Locality information

destination

Cluster 0 Cluster 1

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Construction Phase

IFDB (internal forward database) Every node has to maintain for each

repeater in its cluster a list of nodes to which the repeater has one or more routes

EFDB (external forward database) every repeater has to maintain for each

adjacent cluster a list of nodes to which the cluster has routes

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Construction Phase(cont.)

IFDB of node 1 may be ((4, {8, 15}) (3, {8, 16})), destination is node 15EFDB of node 6 may be ((C2, {1, 18}) (C3, {1, 4}) (C5, {17})) destination is node 4

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Input repeater Output repeater

repeater

destinationoutput repeater

destination

input repeater

IFDBEFDB

Case 1

Case 2

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Construction Phase(cont.)

If IFDB and EFDB do not include the destination

Discovery packet

Update IFDB

Update IFDB

Update IFDB

Reply packet

destination

source

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Construction Phase(cont.)

The cluster-level topology be described to a graph A vertex represents a cluster and a link

between two vertices Routes are built depending on the order of

the reply packet transmission the cluster-level topology would be an

acyclic directed graph (ADG)

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Maintenance Phase

Destination nodeThe ID is DID

x deletes DID fromEFDB (Cj , {DID, . . . })

x y

z

z deletes DID fromIFDB(x , {DID, . . . })

Ci Cj

Update packet

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Maintenance Phase(cont.)

Ex:

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Re-clustering and how to establish a new route

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Simulationrange : N nodes randomly in 100x100 area Fig.3 Transmission range

connectivity

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Fig.4 transmission rangecluster number

(the degree of a topology)

(the average number of nodes in a cluster)

Simulation

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Simulation

Fig.6 The order of most repeaters is either 2 or 3

Fig.7 That more than 50% of nodes are repeatersover the interval(30, 80)

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Simulation

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Simulation

Direction: U(0, 2π), distance: U(0, 3)

Fig.10 The average number of nodes which switch clusters per 100ms is relatively small

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Conclusion

Provide a distributed multicluster architecture for transporting real-time traffic in a multihop dynamic radio networksA hierarchical routing protocol over the architecture is stable and loop-free in the face of topological change

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Discussion

Re-cluster problem

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The Multicluster Architecture and its Properties

ClusterheadMay become bottleneck

Fully distributed algorithm

The system topology G(V , E ) is divided into small partitions (clusters ) with independent control

Advantage:Permits us to

avoid vulnerable

centers and hot spots of packet traffic flow.

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A hierarchical routing protocol’s main reasons

Attempts to reduce traffic by hiding information about the content of a clusterHierarchical structure can scale to large populationsThe multicluster infrastructure is quite stable in the mobile environment(Fig.10) and multiple links connect two adjacent clusters(Fig.8)

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