wireless overview

Wireless - OverviewECE, NIT Durgapur A. Chandra

Wireless Communication – An overview Wireless Communication – An overview

Aniruddha ChandraECE Department, NIT Durgapur

[email protected]


Outline

Wireless Communication – General overview

Challenges in Wireless Communication

Future trends and Research areas





Why Wireless?

Evolution of Standards

Network & Technologies

World Statistics

India Statistics


Why Wireless?

•Mobility – Phone for people not for places.

•Easy Installation – Rapid deployment, reconfigurable.

•Cost Savings – No cable, easy maintenance.

•Digital Companion – Voice, message, internet, multimedia.


GSM Evolution Path

GSM Evolution Path

GPRSGPRS

54 kbps

EDGEEDGE

384 kbps

CDMA Evolution Path

CDMA Evolution Path

2 Mbps

CDMA 2000 (EV-DV, EV-DO)

2 Mbps

W-CDMA UMTS

64 kbps

IS-95B

14.4 kbps

IS-95A

9.6 kbps

IS-95

9.6 kbps

GSM, PDC,

IS-136

3G2.5G2G

Evolution of Standards

• Telegraph 1837

• Telephone 1876

• Radio Comm 1894

• AM comm radio 1920

• FM comm radio 1936

• Mobile Telephone 1940

• Cellular mobile 1974

• Digital Cellular 1991

• Satellite mobile 1998

• 3G cellular 2002

• 4G (expected) 2010


Network & Technologies

2G,2.5G,3G


World Statistics

*March ’06 statistics ( Source www.cdg.org and www.gsmworld.com)

•20 billion GSM Subscribers

•3 billion CDMA Subscribers.


India Statistics

Company No of Subscribers(In million)

% MarketShare

Bharti 19.57 28.30%

BSNL 17.16 24.80%

Hutch 15.36 22.20%

IDEA 7.37 10.65%

Aircel 2.61 3.77%

Reliance 1.90 2.75%

Spice 1.93 2.79%

MTNL 1.94 2.81%

BPL 1.34 1.93%

Total 69.19 100%

GSM subscriber in March’06 (*Source COAI)


India Statistics

Company No of Subscribers(In million)

% MarketShare

Reliance 15.407 75.72%

Tata 4.851 23.84%

HFCL 0.062 0.30%

Shyam 0.027 0.13%

Total 20.348 100%

CDMA subscriber in March’06 (*Source COAI)


India Statistics

•3.6 million jobs generated directly or indirectly

•145billion per annum generated by Mobile industry for the Govt.

•The mobile services industry generates an annual GDP contribution of Rs. 313 billion

•1% increase in teledensity →3% increase in rate of growth of GDP


India Statistics

•Poised to cross 200 million subscribers by 2007

•Catching up fast with China (282 million – Feb’06)

“It is dangerous to put limits on wireless”

- Marconi (1932).



Wireless Channel

Standardization

Network Planning

Other Issues




Wireless Channel

Multipath

t0+τ1

t0

t0+τ2

Time Variance

•Limited Power (Size, Weight, Battery Constraints)

•Limited BW (Spectrum allocation)

•Deep Fading (mainly due to Multipath)

•Time Variance of the Channel

•Path Loss (up to 10 dB/km)


Standardization

•Backward Compatibility

•Interoperability

•Integration of Voice & Data Network

•Frequency Allocation

•Tariff Planning


Network Planning

•Terrain Survey – Shadow zone, Antenna height & size.

•Radio Interference – CCI, ACI, ISI, FDD.

•Power Control – Cost, Interference, Security, Safety, BW.

•Frequency Reuse

•Handoff


Other Issues

•Network Security

•Health Risks

•Social & Economic IssuesTemperature variation inside head due to cell phone use

Change of input characteristics of handset antenna due to hand





UWB

OFDM

MIMO

Future???


UWB - Introduction

•Ultra Wide Band – message sent through narrow pulses that are widely

separated in time.

t/τ

Amp

-1 10

1

-1

Gaussian Monocycle

2

t6exp

tAtv

10k 100k 1M 10M 100M 1G 10G

10-6

10-5

10-4

10-3

10-2

10-1

100

101

102

Power (Watt/ MHz)

BW (Hz)

2G

3G, WLAN

UWB

•Bandwidth(>1GHz) – bandwidth

at -10dB points of spectrum exceeds 25% of

center frequency.

•Impulse Radio – UWB technology

using Gaussian monocycle.

Pulse width(τ) ~ 0.2 to 1.5 nano sec.


UWB - Advantages

•Data Transmission – Pulse

Position Modulation,

0 ~ pulse transmitted early (-TC).

1 ~ pulse transmitted late (+TC).

Reference ‘0’ ‘0’‘1’ ‘1’

TP TP-Tc +Tc

•Data Rate – from 1Mbps (TP=1000 ns) to

40Mbps (TP=25 ns).

•Baseband Processing – no up/down conversion, simple design for transmitter and receiver.

•Mitigating Multipath – echo cancellation during no transmission period.


UWB - Applications

UWB is most suitable for•High data rate

•Short range low power (Indoor)

•High clutter (severe multipath) applications.

UWB HDTV and digital media server by Haier Corp. and Freescale Semiconductor


OFDM - Introduction

•Multi-carrier modulation -Available bandwidth is divided into several narrow bands and one carrier is used in each narrow band.

Serial data stream is divided in N parallel data streams and each is transmitted on a separate band.

1 2 3 N-1 N

fW

W/N f

•Orthogonal Carriers - The sub-carrier frequencies occupies the zero crossing spectra of other sub-carriers.


OFDM - Technology

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Map

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on

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Ser

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IFF

TIF

FT

Cyc

lic

Pre

fix

Cyc

lic

Pre

fix

Convolutional/ Reed Solomon

BPSK/ QPSK/ 16 QAM/ 64 QAM

•Fast serial data stream is transformed into slow parallel data streams - Longer symbol durations.

•Symbols are transmitted on different subcarriers – IFFT/FFT pair.

•Guard time/ Cyclic Prefix is inserted between consecutive OFDM symbols

D/A converterLNA/HPAAntenna

Pilot Insertion Zero Padding


OFDM - Advantages

•Combating ISI - Cyclic prefixing removes ISI from previous symbol.

CP

CP

ISI

• Efficient spectrum utilization - Available bandwidth is divided into several narrow bands and the data is transmitted in parallel on these narrow bands.

•Robustness to fading - A frequency selective channel appears as flat in the narrow bandwidth of sub-carrier.

•Right in track - Development in Digital Signal Processing simplifies the generation of OFDM signals.


OFDM - Challenges

•Much more sensitive to synchronization errors than single-carrier systems - Synchronization of symbol duration and carrier frequency is highly essential to maintain orthogonality among the sub-carriers

•High peak to average power ratio - OFDM signals have high Peak to Average Power Ratio (PAPR) which leads to Out Of Band (OOB) distortion. Also it requires amplifiers with very high linear characteristics to avoid OOB distortion.

•Wastage of bandwidth in cyclic prefix.


OFDM - Applications

•Used for wideband communication over mobile FM channels.

•Asynchronous Digital Subscriber Line (ADSL), High speed DSL, Very high speed DSL use OFDM for transmission of high rate data.

•Digital Audio Broadcasting (DAB) and Digital Video Broadcasting (DVB).

•IEEE 802.11a and IEEE 802.11g wireless Local Area Network (WLAN) uses OFDM for supporting high bit rate.

•European Telecommunications Standard Institute’s proposed HIPERLAN2 includes OFDM.

•IEEE 802.16 Wireless MAN technology also proposes to use OFDM.

•Some authors have also advocated use of OFDM in mobile Ad Hoc networks.


MIMO

Evolution of Smart Antenna Technologies

•Diversity

•Beamforming

•Space Division Multiple Access (SDMA)

•Multiple Input Multiple Output (MIMO)

Transmitter Receiver

MIMO

SISO

SIMO

MISO


MIMO

•Why MIMO?

To increase capacity one have to increase signal power exponentially.

•With MIMO Capacity increases N fold compared to SISO systems

N

S1logBC

rt N,NminN

Receivers of No.N

rsTransmitte of No.N

r

t

•MIMO vs. DiversityIn Diversity system same message is sent over multiple channels to improve reliability.

In MIMO systems different messages are sent to increase capacity.


MIMO - Technology

Transmitter Receiver

h11

h22

h12

h21

x1

x2

x1h11+x2h12

x1h21+x2h22

H-1H-1

x1

x2

A 2x2 MIMO System

•The basic Input-Output Relationship is Y=H.X or,

•Receiver has to find X using the relation X=H-1.Y

•Considering Noise Y=H.X+N

2

1

2221

1211

2

1

x

x

hh

hh

y

y

2

1

2

1

2221

1211

2

1

n

n

x

x

hh

hh

y

y

For 2x2 MIMO system

For 2x2 MIMO system


MIMO - Applications

World's first laptop with MIMO WLAN technology - Samsung NT-X20 with Airgo's True MIMO chip set (802.11a/b/g)

•802.11n for WLAN

•802.16 for WMAN

•802.20 for MBWA

•Optical communication (Multi-mode Fiber)

•High density rewritable optical storage

•3G/4G Cellular

Mobile Broadband Wireless Access

MIMO-HSDPA for 3.5G (10Mbps)


Future???

•MIMO-OFDM

•Turbo Codes

•New/ Hybrid Technologies?

•Cognitive Radio – Radio with Brain?

Cognitive radios will have the ability of devices to determine their location, sense spectrum use by neighboring devices, change frequency, adjust output power, and even alter transmission parameters and characteristics.

Date post:	08-May-2015
Category:	Technology
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