7 Introduction-Wireles Lan

8/2/2019 7 Introduction-Wireles Lan

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IITKharagpur

Prof. R. V. Raja Kumar Dept. of E & ECE

What is a wireless LAN?

A wireless LAN is a data transmission system

designed to provide location-independent

network access between computing devices by

using radio waves rather than a cable

infrastructure.

Usually implemented as the final link between

existing wired network and group of client

computers.

Wireless LAN = LAN without wires. Anytime,

anywhere


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Infrastructure Network

Point-to-multipoint

Ad hoc network

Ethernet bridge

Point-to-point

Application of Wireless LAN


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Wireless LAN Standards

IEEE 802.11Established by IEEE in June 1997

Specifies 2.4GHz frequency of 1 Mbps and 2 Mbps.

Two more specifications came up in Late 1999.

IEEE 802.11b Uses CCK and provides data ratesup-to 11 Mbps

IEEE 802.11a& g Uses OFDM and provides data

rates up-to 54 Mbps

HiperLAN

It is primarily used in Europe countries. It operates in

5GHz radio band. There are 2 specifications

namely

HiperLAN/1 and HiperLAN/2


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Features of IEEE 802.11a and b

Direct sequence spread spectrum Operates in the 2.4GHz band 14 Channels spaced 5 MHz apart The United States support the first 11

channels Data rates 11, 5.5, 2 and 1 Mbps

IEEE802.11b standard

IEEE802.11a standard

Orthogonal Frequency Division

Multiplexing Operates in the 5GHz band Data rates 54, 48, 36, 24, 18, 12, and 6

Mbps 6, 12, and 24 are Mandatory


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Specifications same as 802.11a:

Frequency of operation = 2.4 GHz like 802.11b.

Hence signal attenuation is low, unlike in the 5GHz band. Orthogonal Frequency Division Multiplexing Operates in the 5GHz band Data rates 54, 48, 36, 24, 18, 12, and 6 Mbps

6, 12, and 24 are Mandatory Systems are under development

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IEEE 802.11 g


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Wireless Metropolitan

Area Networks (MANs)

BS

Company

HomeApartment

Office

PDA Up to 35 miles


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WMAN ApplicationsIIT

Kharagpur

1. Broadband connectivity to fixed, portable and

nomadic users.

2. Traditional voice communication.

3. Video distribution.

4. Video conferencing.

5. Streaming media services.

6. Last mile local connection to internet.


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MMDS Point to Multipoint (2.5 2.7 GHz)

LMDS Point to Multipoint (28 & 31 GHz)

Point-to-multipoint with sector antennas Point-to-point with directional antennas

Throughput to 60 Mbps shared per sector (5.8 GHz)

Multiple manufacturers (non-standards based today)

TDM

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LMDS and MMDS


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Other FeaturesIIT

Kharagpur

Broad bandwidth

Up to 134 Mbit/s in a 28 MHz channel (in 10-66 GHz air interface)

Point-to-multipoint topology, with mesh extensions

Supports multiple services simultaneously with full QoS

Efficiently transport IPv4, IPv6, ATM, Ethernet, etc.

Bandwidth on demand (frame by frame) MAC designed for efficient use of spectrum (TDM and TDMA)

Supports multiple frequency allocations from 2-66 GHz

ODFM and OFDMA for non-line-of-sight applications

TDD and FDD

Link adaptation: Adaptive modulation and coding

Subscriber by subscriber, burst by burst, uplink and downlink

Extensions to mobility are coming next.

Coexistance with 4G?


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WMAN StandardsIIT

Kharagpur Standard 802.16 802.16a/d 802.16e 802.20

Status 2001 2004 2005 2005-06

Target App. WMAN WMAN WMAN WWAN

Range Average CellRadius 1-3 mi

Average CellRadius 4-6 mi

Average CellRadius 1-3 mi

Channel

Conditions

LOS NLOS NLOS NLOS

Spectrum 10-66 GHzLicensed

2-11 GHz 2-6 GHz


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The last mile access solution Alternative to DSL, cable modem, leased lines,

fiber and other broadband network access

technologies

Ability to transfer data, voice, and video atspeeds of up to 70 Mbps

The 802.16e will support subscriber stations

moving at pedestrian and vehicular speeds

(speeds of 120 to 150 Kmph) Has potential to be deployed far faster, less

expensively, and more flexibly than similar

wireline installations

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IEEE 802.16


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Multiaccess and ModulationIIT

Kharagpur

OFDM (WirelessMAN-OFDM Air Interface) 256-point FFT with TDMA (TDD/FDD)

OFDMA (WirelessMAN-OFDMA Air Interface) 2048-point FFT with OFDMA (TDD/FDD) Single-Carrier (WirelessMAN-SCa Air

Interface) TDMA (TDD/FDD) BPSK, QPSK, 4-QAM, 16-QAM, 64-QAM, 256-

QAM

Most vendors will use Frequency-DomainEqualization


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Metropolitan area network (MAN) protocol Real-time data transmission at DSL/Cable

speeds (1Mbps or more) based on cell range Cell ranges of up to 15 kilometers or more Mobile users even when they are traveling at

speeds up to 250 Kmph (802.20 is an option for

deployment in high-speed trains) The 802.16e will support subscriber stations

moving at pedestrian and vehicular speeds(speeds of 120 to 150 Kmph).

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IEEE 802.20


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WiMax Forum

IIT

Kharagpur

NEOTEC

An industry-led, non-profit corporation formed to

promote and certify compatibility and interoperability of

broadband wireless products.wide acceptance of the IEEE 802.16 and ETSI HiperMAN

wireless MAN standards.


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IITKharagpur

Prof. R. V. Raja Kumar, Amit Kumar Dept. of E & ECE

Bluetooth

It is a wireless personal area network

for connecting closely spaced

devices in a range of 10m.

Cost effective Standardized by IEEE 802.15 Conceived by Ericsson in 1985. Works in 2.4 GHz unlicensed band Connects PDAs, headset, mobile

phones, USB, PCs printers etc. 1 Mbps, FHSS (2.402+k) MHz (k=0,1,2,,78); 1600 hops/Sec. GFSK modulation


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Ultra Wideband Systems

Unmodulated baseband signals are used

for a short range communication at very

low powers. The interference caused is

negligible.

Typical bandwidth 2-10 GHz.


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UWB Signals

Typically UWB signals are modulated pulse trains Very short pulse duration (


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Large Bandwidth of UWB

UWB is a form of extremely wide spread spectrum where RFenergy is spread over GHz of spectrum

Wider than any narrowband system by orders of mag. UWB power seen by a narrowband system is a fraction of

the total

UWB signals can be designed to look like imperceptiblerandom noise to conventional radios

Narrowband (32 KHz)

Wideband (5 MHz)

UWB ( a few GHz)

Part 15 limit

Frequency, f

PSD


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0.96 1.61

1.99

3.1 10.6

GPS

Band

Power Spectral Density Limits


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RF Tags

Passive and active RF tagsApplication in Ware houses

Very low power Very low range (eg.: 10m)

Very low cost (eg.: 10 cents)

Detection, identification and location of tagged

items (eg.: boxes)


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Owner Motorola

Satellites 66, 11/orbit

Orbits 900km, 6 polar orbits

Type Big LEO

MAC method FDMA\TDMARound trip

delay10 ms approx.

Start ofService

1998

Services Voice, Data (2.4 Kbps), FAX,

GPS

Mobile Sat. Comm. (Irridium)


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Each satellite is like a BS for

40min-120 min. Relay Station switching Comm. distance ~ 200km Attenuation almost 40000

times less as compared toGeo Stationary path

Low power requirements=>

smaller (& cheaper) handsets Cost compensated in the

deployment of manysatellites and on handover

technology6 X 11 LEO polar orbit

Satellites for global coverage

Low Earth Orbit Satellites


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Technology


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Handsets

Nokia 9110

3COM

Palm VII

Nokia

3G visionPCMCIAWLAN Card

The newEricsson R380

phone, which

features wireless

data functions


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Transceiver of a Wireless System

Source

coder

Channel

CoderInter-

leaver

Amp.

& Tx.

filter

Freq.synthesizer

Source

decoder

Channel

Decoder

Modu-

latorADC Mixer

Rx.

filter &

LNAMixer

Amp &

DAC

Deinte-

rleaver

Equal.,

demod.

AGC &

Synch.

Protocolprocessor &

Controller

DSP /

contro-ller

Digital

ASICs

Analog /

mixed SP


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IITKharagpur

Prof. R. V. Raja Kumar, Amit Kumar Dept. of E & ECE

RF

Front

end

Base-

Band

Proce-ssor

Protocol,

LogicalCh. Proc.

&

Control

HS

ADCDAC

Aud.

codec

Implementation

RF ASICs: LNA, Mixer, Freq.

Syth., Power amplifier

Data conversion: ADC, DAC

Digital ASICs: Basebandprocessors,

DSPs: Baseband proc.,

source coding,

proc.s /controllers:Protocol processing, System

controlling

System on a

Chip


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VLSI Technology

Roadmap

Characteristic 1999 2001 2004 2008

Process technology (nm) 180 130 90 60

Logic transistors (millions) 23.8 47.6 135 539

Across-chip clk. Speed(MHz)

1200 1600 2000 2655

Die-area (sq. mm) 340 340 390 468

Wiring levels 6 7 8 9


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System on a Chip

(SoC)

Evolution of ASICs into SoCs The use of pre-designed IP blocks Technology for future systems

RF CMOStechnology

low cost High performance and low power chips for

portable applications

Ex.: PDA

100 mW(2mW st. by)

300 MOPs to

2500 MOPs

SoCRF

Base-

band

Network

Proc.Memory


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Libraries of different standards like, Radio frequency bands, Intermediate frequency (IF) bandwidth, Modulation schemes,

Coding schemes, Access methods, Cryptographic standards, Network protocols like MAC,

Frequency hopping to find secure channels.

Provides features that are useful for intelligence

gathering and other tasks defense comm.

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SDR Subsystem

Library


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New energy-efficient algorithms, Reconfigurable architectures based on ASICs

(application-specific integrated circuits),

Digital signal processing for SDRs, Use of FPGAs (field-programmable gate arrays)

for SDR silicon.

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Research Issues in

Software Defined Radio


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Capacity Enhancement and

Enabling Techniques

Multiuser detection (MUD)

Antenna array

Transmit diversity

Transmission power control (TPC)

Turbo Codes

Software radio (SWR)

High Performance DSPs

High energy rechargeable batteries


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MAC Enhancements Physical layer issues (eg.: equalization) Smart antennas Multiple-input-multiple-output systems Space-time coding Dynamic packet assignment Multiaccess methods (eg.: MC-DS-CDMA) Software radio

High performance DSPs and ASICs

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Some Research Areas


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Thank You

7 Introduction-Wireles Lan

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