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4-G SYSTEMS

HIGH SPEED SATELLITE MOBILE COMMUNICATIONS

PRESENTED BY:

JAYASREE

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INTRODUCTION:

Satellite mobile communication has gained enormous attentions in the

wake of third generation (3G) and fourth-generation (4G) wireless

communications systems and their challenges.

Space way system provides downlink transmission rates of up to 100

Mb/s, and a total capacity of up to 4.4 Gb/s.

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Simplified base band satellite mobile communication model

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Physical channel - characteristics and implications:

Downlink requires more resources than uplink-mainly interms of bandwidth, transmission rate and power.

This is because of the asymmetric nature of the traffics andapplications between the two links.

Uplink will require much smaller capacity and data ratesas users will need to upload relatively small amounts ofdatasuch as browsing requests, e-mail messages, basicuser information (e.g., user ID and account code), etc.

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The problems

High power amplifiers (HPAs)

Multipath propagation and fading

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Multistate statistical models

Significance of the models

Base for these models

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Channel modeling challenges

Integration with other terrestrial networks

High data rate applications

flexibility

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Physical layer technologies and

challenges

Spectral efficiency

Power efficiency

Joint optimization of both

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Different modulation schemes in use

PSK modulation

QAM

OFDM

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CHALLENGES INNEXTGENERATIONSYSTEMCONCERNING

DIFFERENTMODULATIONTECHNOLOGIES

Spectral and power efficiency

Fading

Nonlinear environment

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Total degradation performance for different 16-

QAM

circular constellations in the presence of a

nonlinear amplifier.

Performance of different 16-QAM

circular constellations in the

presence of a nonlinear amplifier, with

and without predistortion.

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coding

It is a systematic approach for the replacement of the original

information symbol sequence by a sequence of code symbols, in such a

way as to permit its reconstruction.

channel coding improves the power efficiency of a transmission

scheme at the expense of spectral efficiency

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Recently Addressed Coding

Techniques

Hamming codes

BCH codes

Reed-solemn codes

Turbo code

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Other features

Diversity combining

Performance criteria

Onboard processing

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FUTURE SATELLITE SYSTEMS: ARCHITECTURES,

QOS

AND RESOURCEMANAGEMENT, AND CROSS-

LAYERDESIGN

In the 4G system, the trend is toward global information networks

offering flexible multimedia information services to users on demand,

anywhere, anytime

Broadband satellite links will also be used as the backbone in the

global network, providing ubiquitous multimedia and high-speed data

applications

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Broadband Satellite Architectures and

Constellations

Broadband satellite architectures may be based on ATM with

sophisticated OBP, OBS, and inter-satellite links (ISLs), while others

employ simple bent-pipe transponder relays

The system design choices depend on factors including coverage, cost,

user service, and traffic demands

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Future Trends

The use of even higher frequencies will be increasingly common in the

future broadband satellite system, as available spectra becomes scarcer

Higher frequencies will then enable further use of smaller terminalsand, potentially, greater mobility

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CONCLUSION

The paper has given an overview of the technologies and challenges of

high-speed satellite mobile communications

Different technological advances in the field of satellite mobile

communications have been presented in the light of future 4G system

requirements

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references

F. Adachi, M. Sawahashi, and H. Suda, Wideband DS-CDMA for next generation

mobile communication systems, IEEE Commun Mag., pp. 5669, Sept. 1998.

C. Comaniciu and H. V. Poor, Jointly optimal power and admission control for delay

sensitive traffic in CDMA networks with LMMSE receivers, IEEE Trans. Signal

Processing, vol. 51, pp. 20312042, Aug. 2003.

http://www.3gtoday.com

http://www.qualcomm.com

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