16 basics of wimax

8/6/2019 16 Basics of Wimax

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www.gcl.in Gemini Communication Company Confidential Ver 1.0

Gemini Communication Ltd.Gemini Communication Ltd.

Innovation & LeadershipInnovation & Leadership

Basics of RF TechnologyRef. 1040001100


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WIMAX BASICS


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Data as on June,06 3

Ver 01www.gcl.in Gemini Communication Company Confidential Ver 1.0

Introduction

Broadband Wireless concept

Evolution of WiMAX


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Data as on June,06 4Ver 01


What is AccessSystem designed to transfer signals from their point

of generation (the user), to the first node of the

(transport) network is known as Access System

Operator / ISP

Network

Access System

useruser

Access System

user

AccessSyste

m

user


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Broad band Wireless Access Point to Multi

point Features

Base station serving many customers

Distribute costs over large number of users

Typically data rates in excess of 256 kbps per Customer

Line of Sight Technology


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Prevailing Wireless Access Technologies

Local Multipoint Distribution Services (LMDS)

Multi-channel Multipoint Distribution Services (MMDS)

W-CDMA

TD-CDMA

Wi-Fi


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What is WiMAX

Worldwide Interoperability for Microwave Access (WiMAX)is the common name associated to the IEEE 802.16a/d/e

standards that originally covered the Wireless Local Looptechnologies with radio spectrum from 10 to 66 GHz.

The technology on which we are working is IEEE 802.16-2004/d

Why WiMAX

Standard based (IEEE 802.16 Series of Standards)

Lower CostEnsures compatibility and interoperabilityBetter Performance & Coverage

IEEE 802 16 Broadband Access System


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Traffic is generated as Service Flows (SF)

Service Flow is a flow of packets to which specific QoS level is guaranteed

Service Flows and their associated QoS parameters are defined before the operation

of the network, but can also be modified, added or deleted during operation.

Packets are identified as belonging to a specific Service Flow based on Connection

Identifier CID

CID is used by Subscriber Stations (SS) to request uplink bandwidth grants from

Base Station (BS)

WAN

(Internet /Intranet)

userLAN

user

user

user

userLAN

user

BaseStation

(BS)

SubscriberStation

(SS)

IEEE 802.16 Broadband Access SystemConcept


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Why Broadband Wireless Access ?

Copper Wire (DSL)

Optical Fiber Cable

Wireless Access System.Satellite Communication System

Ways of providing Broadband Access?

Lower Capital Expenditure

Lower Operational Expenditure Faster Deployment Time Scalable & Easy Relocation


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Evolution of Standards

IEEE 802.16 (2001) Air Interface for Fixed Broadband Wireless Access System MAC

and PHY Specifications for 10 66 GHZ (LoS)

One PHY: Single Carrier

Connection-oriented, TDM/TDMA MAC, QoS, Privacy IEEE 802.16a (January 2003) Amendment to 802.16, MAC Modifications and Additional PHY

Specifications for 2 11 GHz (NLoS)

Three PHYs: OFDM, OFDMA, Single Carrier Additional MAC functions: OFDM and OFDMA PHY support,

Mesh topology support, ARQ

IEEE 802.16d (July 2004)

Combines both IEEE 802.16 and 802.16a Some modifications to the MAC and PHY

IEEE 802.16e (November 2005) Amendment to 802.16-2004

MAC Modifications for limited mobility


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WiMAX Technology

Description


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Modulation

Modulation is the process by which a carrier wave isable to carry the message or digital signal (series ofones and zeroes).

There are three basic methods to this:-

Amplitude,

Frequency

Phase shift keying


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Binary Phase Shift Keying (BPSK)

BPSK is the simplest form of PSK.

It uses two phases which are separated by 180and socan also be termed 2-PSK.

It does not particularly matter exactly where theconstellation points are positioned

It is, only able to modulate at 1bit/symbol and so isunsuitable for high data-rate applications.


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Quadrature Phase-shift Keying (QPSK)

Sometimes known as quaternary or quadriphase PSK or 4-PSK, QPSK uses four points on the constellation diagram,equispaced around a circle.

With four phases, QPSK can encode two bits per symbol-twice the rate of BPSK.

This is used either to double the data rate compared to a

BPSK system while maintaining the bandwidth of the signalor to maintain the data-rate of BPSK but halve thebandwidth needed.

BPSK is used on both carriers and they can be

independently demodulated.


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16-QAM,64-QAM

The number before QAM (for example 16QAM) refers directly tothe number of decision points in the constellation. Meaning,256QAM has 192 more decision points than 64QAM. The

number before QAM is also always a power of two. (EG.

2^6=64QAM) The more Decision points, the more throughput per channel.

The more Decision points, the more susceptible the channel is to

noise (as the decision boundaries get smaller to accommodate

more decision points, it becomes harder to distinguish whichboundary the point was intended to lie in).

More Decision points=More Bandwidth=Higher susceptibility to

noise or poor signal (the same applies inversely as well).

Deliver the same number of customers incrementally faster

speeds.-or-

Deliver a larger number of customers the same speeds as

before.


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Adaptive Modulation


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Line Of Sight & Near Line of Sight

For LoS First Fresnel Zone should be clear of any

obstructions (at least 60% area)

This requires both BS and SS to be placed outdoor

In case of any obstruction in the transmission path then

30% clearance of FFZ may be taken and is known as Near

LOS


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Non-Line Of Sight (NLOS)

Signal reaches the receiver through reflections, scattering,and diffractions.

These signals have different delay spreads, attenuation,

polarizations, and stability relative to the direct path.NLOS technology also make CPE installation easy & less

expenses

The technology also reduces the need for pre installationsite surveys.


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FDM & OFDM

FDM OFDM

+=


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Orthogonal Frequency Division Multiplexing

OFDM: a form of MultiCarrier Modulation & Multiplexing technique.

Different symbols are transmitted over different SUBCARRIERS. Spectra overlap, but signals are orthogonal.

The basic idea is that each bit occupies a frequency-time

window which ensures little or no distortion of the waveform

Signals are orthogonal if they are mutually independent of each other.


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OFDM technology

28 Guard carriers on left 27 on right 8 pilots 1 DC and 192data sub carrier


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OFDM operation OFDM is a multicarrier block transmission system

Conversion of a high-data rate stream into several low-rate streams

Parallel streams are modulated onto orthogonal carriers Data symbols modulated on these carriers can be recovered without mutual

interference

Overlap of the modulated carriers in the frequency domain - different from FDM

Block of N symbols are grouped and sent parallely

No interference among the data symbols sent in a block


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Link Budget Calculations

Receiver

Antenna

Antenna

Cable

Transmitter

Cable

Power output

Cable Loss

Gain

Path Loss

Gain

Cable Loss

Sensitivity


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Q & A


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Thank YouContact : [email protected]

16 basics of wimax

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