Adaptive Clustering For

8/2/2019 Adaptive Clustering For

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Adaptive Clustering

for Wireless Mobile Networks


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Abstract

This paper describes a self-organizing, multihop, mobile radionetwork which relies on a code-division access scheme formultimedia support.

This network architecture has three main advantages:

It provides spatial reuse of the bandwidth.

Bandwidth can be shared or reserved in each cluster.

The cluster algorithm is robust in the face of topological changes causedby node motion, node failure, and node insertion/removal.

Simulation shows that this architecture provides an efficient, stableinfrastructure for the integration of different types of traffic in adynamic radio network.


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Contents

Introduction

The Multicluster Architecture

Transport Protocols QoS Routing

System Performance

Conclusions


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Introduction(1/2)

Packet radio network (PRNET), developed in the 1970s to address

the battlefield and disaster recovery communication requirements[16], [17].

Fig. 1. Conventional cellular networks (single hop).


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Introduction(2/2)

We develop an architecture and networking algorithms which supporta rapidly deployable radio communications infrastructure.

The network provides guaranteed quality of service (QoS) to real-time multimedia traffic among mobile users without requiring a fixedinfrastructure (e.g., no base station).

Fig. 2. A multihop situation occurs when base station B fails.


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The Multicluster Architecture(1/9)

The Clustering Algorithm

Cluster Maintenance in The Presence of Mobility

Code Assignment Network Initialization


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The Multicluster Architecture(2/9)The Clustering Algorithm

We make the following operational assumptions underlying theconstruction of the algorithm in a radio network.

These assumptions are common to most radio data link protocols [3],[4], [6], [7].

Every node has a unique ID and knows the IDs of its one-hop neighbors.

A message sent by a node is received correctly within a finite time by allof its one-hop neighbors.

Network topology does not change during the algorithm execution.


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Fig. 3. Distributed clustering algorithm.

Fig. 4. System topology.

Fig. 5. Clustering


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We begin studying the impact of transmission range on connectivity.

Fig. 6. Connectivity property. Fig. 7. Average order of repeaters.


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The existence of at least one path between a pair of nodes isrequired.

The number of repeaters will affect the number of paths.

Fig. 8. Number of repeaters.


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The Multicluster Architecture(6/9)Cluster Maintenance in The Presence of Mobility

In the dynamic radio network Nodes can change location

Nodes can be removed

Nodes can be added.

The cluster maintenance scheme was designed to minimize thenumber of node transitions from one cluster to another.

Fig. 9. Reclustering.


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The Multicluster Architecture(7/9)Cluster Maintenance in The Presence of Mobility

Fig. 10. Stability of the multicluster architecture.


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The Multicluster Architecture(8/9)Code Assignment

Each node has a transceiver which can either transmit or receive atany given time.

In the spread-spectrum code-division system, the receiver should beset to the same code as the designated transmitter.

There are three options for using the dedicated code within a cluster. Receiver-based code assignment Transmitter-based code assignment To assign a common codes to all transmitterreceiver pairs within a

cluster.

Based on transmitter-based code assignment, when a node is not intransmitting mode, it randomly selects and listens to one of the codesused by its neighbors.


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The Multicluster Architecture(9/9)Network Initialization

This basic communication facility allows nodes to organizethemselves in clusters following the algorithm just described.

Once a cluster is formed, the cluster leader communicates with theneighbors (using the control code) to select the codes.

Only when the code assignment is completed (i.e., each cluster hasbeen assigned its code) can user data be accepted by the nodes andtransmitted in the network.


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Transport Protocols(1/4)

The aim of our design is to support integrated traffic (i.e., datagramand real time) efficiently.

Channel Access Scheme Acknowledgment for Datagram

Mobility


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Within each cluster, the MAC layer is implemented using a TDMAscheme.

Time is divided into slots which are grouped into frames.

Channel Access Scheme

Fig. 11. Channel access frame within a cluster.


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Transport Protocols(3/4)Acknowledgment for Datagram

Fig. 12. Implicit acknowledgment scheme.


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Node changes its own cluster ID, using the free slot to transmitpackets in the new code.

Mobility

the nodes in a clusterwill recompute the newTDMA frame format.

In the same way, if anode is removed from a

cluster, the frame isreduced.

Fig. 14. Average number of links between an adjacent cluster pair.


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QoS Routing (1/4)

Multimedia applications such as digital audio and video have muchmore stringent QoS requirements than traditional datagramapplications.

For a network to deliver QoS guarantees, it must reserve and controlresources.

Bandwidth in The Cluster Infrastructure

QoS Routing Scheme


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QoS Routing (2/4)

The key resource for multimedia QoS support is bandwidth.

A node can at most transmit one packet per frame, the bandwidth ofa node is given by

Bandwidth in The Cluster Infrastructure

timeframe

timecyclebandwith

Fig. 15. Node bandwidth.


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QoS Routing (3/4)Bandwidth in The Cluster Infrastructure

Fig. 16. Bandwidth of node C in cluster C1.


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QoS Routing (4/4)

The goal of the bandwidth routing algorithm is to find the shortestpath.

QoS Routing Scheme

Fig. 17. Standby routing.

Fig. 18. The primary route fails and thestandby route becomes the primary route.Another standby route is constructed.


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System Performance(1/6)

The default CYCLEtime is 100 ms.

The offered traffic consists of two components:

Real-time sessions

Datagrams

Weighted end-to-end Throughput

Real-time and Datagram Traffic Mix

Standby Routing

Scheme Comparison Synopsis


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System Performance(2/6)

The link throughput is defined as the sum of the throughputs on thelinks which are simultaneously active in the network.

We measure the end-to-end throughput accounting for possiblenetwork disconnection:

Weighted end-to-end Throughput

DC

i i

i

iL

LTf

1

throughput

iL

iLTif

DC total number of disconnected components;

fraction of node pairs in component 2/1/2/1 NNnniii

total link throughput of component i ;

average path length in component i ;


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System Performance(3/6)Weighted end-to-end Throughput

Fig. 19. End-to-end throughput.


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System Performance(4/6)Real-time and Datagram Traffic Mix

TABLE ISYSTEM TOPOLOGY (N = 20)

Fig. 20. Throughput of mix traffic.


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System Performance(5/6)Standby Routing

TABLE IIPERFORMANCE OF STANDBY ROUTING (MAXIMUM SPEED = 2 FT/S)

TABLE IIITHE PERFORMANCE OF STANDBY ROUTING (MAXIMUM SPEED = 8 FT/S)


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System Performance(6/6)Scheme Comparison Synopsis

TABLE IVOVERALL PERFORMANCE COMPARISON (2 FT/S)

TABLE VOVERALL PERFORMANCE COMPARISON (8 FT/S)


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Conclusions

In order to reduce control overhead and to overcome the limitation ofthe number of orthogonal codes, we use only one code within eachcluster.

Packet transmissions by data sources and real-time sources areinterwoven, with top priority given to real-time sources.

The performance of the proposed cluster scheme is similar to that ofcluster TDMA [7], with less implementation complexity.


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