An Overview of the Trans Miss On Capacity of Wireless Networks

8/7/2019 An Overview of the Trans Miss On Capacity of Wireless Networks

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VISVESVARAYA TECHNOLOGICAL

UNIVERSITY

An Overview of the Transmisson Capacity ofWireless Networks

A Seminar Presentation

On

Submitted by:

Lohith.C

1RN07IS030

Under Guidance

of

Hema.K.L


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ABSTRACT

Decentralized wireless network analysis known as

transmission capacity.

General end-to-end capacity results for multi-

terminal or adhoc networks.

The relationship between the optimal spatialdensity and success probability of transmissions in

the network.


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ABSTRACT

The basic model and analytical tools .

Random channels (fading/shadowing) as wellas exact results for the special cases of

Rayleigh and Nakagami fading.

Understanding scheduling, power control, andthe deployment of multiple antennas in a

decentralized network.


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Index Terms

Transmission capacity

Wireless Networks

Ad hoc network

Stochastic geometry


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CONTENTS1

.INTRODUCTION

2. SYSTEM MODEL

2.1. Mathematical Model and Assumptions

2.2. Mathematical Background2.3. Relationship to Transport Capacity

3. BASELINE MODEL: PATH LOSS ONLY

3.1. Exact Results3.2. Lower outage bound: dominant nodes


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CONTENTS

4. TRANSMISSION CAPACITY OF FADING CHANNELS

4.1. General fading

4.2. Rayleigh fading

4.3. Nakagami fading

4.4. Threshold scheduling

4.5. Power control

5. MULTIPLE ANTENNAS

5.1. Diversity

5.2. Spatial Interference Cancellation

5.3. Spatial Multiplexing

6. CURRENT LIMITATION AND FUTURE DIRECTIONS

7. ACKNOWLEDGMENTS


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INTRODUCTION

THIS paper presents the recently developed framework for the

outage probability and transmission capacity in a one hop

wireless ad hoc network.

From the expressions and approach given in this paper the exactdependence between system performance and the possible

design choices and network parameters are laid bare.


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Goals of this framework

The first goal of this paper is to summarize thenew analytical tools that have been developed

over numerous papers by the authors and others.

The second goal is to show how this frameworkcan be used to give crisp insights into wireless

network design problems.

The third goal of the paper is to stimulate new

efforts to further the tools presented here.


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SYSTEM MODEL

Mathematical Model Consider an ad hoc wireless network consisting

of a large (infinite) number of nodes spread overa large (infinite) area.

The network is uncoordinated, meaningtransmitters do not coordinate with each other inmaking transmission decisions. That is, nodesemploy Aloha as the medium access control

(MAC) protocol .


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The PPP assumption for node locations is valid

when the uncoordinated transmitting nodes areindependently and uniformly distributed over the

network arena.

If intelligent transmission scheduling is

performed, the resulting transmitter locations will

most certainly not form a PPP, so this papers

analytical framework is primarily applicable to

uncoordinated transmitters.


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Assumptions

Each transmitter is assumed to have anassigned receiver at a fixed distance r away.

The set of receivers is disjoint with the set of

transmitters. Because the network is infinitelylarge and spatially homogeneous.

We place the reference receiver at the origin(o),and the reference transmitter is located r

meters away.


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Note that the locations of the other receivers are notimportant because the reference receiversperformance only depends upon the positions of thetransmitters.

Each transmitter is usually assumed to employ unittransmission power .

The channel strength is assumed to be solelydetermined by pathloss and fading, i.e., the receivedpower at distance d is is the pathloss exponent and His the fading coefficient


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The outage probability(OP), denoted by q, is the probability that

the signal to interference ratio (SIR) at the reference receiver is

below a specified threshold required for successful reception


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Where

is defined as the aggregate interference power seen at the

reference receiver at the origin, normalized by the signal power

Our primary performance metric is the transmission capacity(TC) which takes a target OP as a parameter


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Notations used in PAPER


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Relationship to transport capacity


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MULTIPLE ANTENNAS The amplitude and phase of fading channels vary quite rapidly

over space.

This allows multiple suitably-spaced antennas to be deployed at

both the transmitter and receiver to generate Tx-Rx

antenna pairs, where and are the number of transmit andreceive antennas.

Multiple antennas are central to all emerging high-data rate

broadband wireless standards

They also provide ability to perform interfernce cancellation.


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Current Limitations

and

Future Directions

They are for a snapshot, or singlehop, of thenetwork.

A network with higher single-hop TC should be ableto achieve higher end-to-end capacity than anetwork with smaller TC.

In addition, noise should not be neglected since aprinciple function of multihop is to increase the SNRfor each hop.


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(continued)

They rely on a homogeneous Poisson distribution ofnodes for tractability, which accurately models only

uncoordinated transmissions (e.g., Aloha).

A well known alternative is to schedule simultaneoustransmissions with the objective of controlling

interference levels

The transmission capacity framework clearly leans

towards simplicity and tractability.


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ACKNOWLEDGEMENTS

The technical contributions of

G. de Veciana

A. Hasan A. Hunter

X. Yang

K. Huang


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Thank You

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An Overview of the Trans Miss On Capacity of Wireless Networks