Lecture 6

WiMAX

Introduction

•WiMAX (Worldwide Interoperability for Microwave

Access) is a technology standard for long-range wireless

networking for both mobile and fixed connections.

•WiMAX would operate similar to Wi-Fi but at a higher

speeds, over greater distances, and for a greater number of

users.

WiMAX advantages• WiMAX technology offers:

1- High speed of broadband service of 70 Mbps

2 – Broad coverage - like cell phones with

coverage radius of 50 Km

WiMAX Parts

• WiMAX system consists of two parts:

1) WiMAX Tower; it is similar to cell phone tower with large coverage area (~8.000 square km).

2) WiMAX Receiver ; it could be a small box or PCMCIA card.

WiMAX Modes

• WiMAX has two modes:

1) Non line-of-sight; where a small antenna on a

computer connects to the WiMAX tower. It uses a

lower frequency rang 2 GHz – 11GHz. (802.16a)

2) Line-of-sight; where a fixed dish antenna

points straight at the WiMAX tower. It uses higher

frequency 10 GHz up to 66 GHz.

802.16 Standard Specifications

• Range - 50-km radius from base station

• Speed - 70 Mbps

• Line-of-sight is not needed between user and base station

• Frequency bands - 2 to 11 GHz and 10 to 66 GHz (licensed

and unlicensed bands)

• Are metropolitan in scale

• Use point-to-multipoint architecture with stationary rooftop or

tower-mounted antennas

WiMax Applications

• Digital audio/video multicast

• Digital telephony

• ATM

• Internet protocol

• Bridged LAN

• Back-haul

• Frame relay

• City Wide Camera Network

WiMAX Application Example:

Citywide Wireless Video

Surveillance

• Designing a Citywide Wireless Surveillance System – “the

right way” – is a highly complex task, underestimated by

many.

• When high motion is encountered, at 30 Frames Per Second

(FPS) and 4CIF resolution, a single video stream requires as

much as 4 Mbps (using MPEG-4 encoding).

Cont.

• In most citywide surveillance systems, wireless technology

enables a municipality to build out the system at an affordable

cost point. However, if the wireless part of the network is not

properly designed, the customer will be disappointed with the

performance of the network.

Example 1

• Assume in the Network below we have the following number

of cameras in each site.

• If the Camera bandwidth requirement is 4 Mbps, then calculate

the bandwidth required for Link 1 and Link 2 and then pickup

the right solution for each link.

• TX power of 30 dBm and Antenna Gain of 18 dBi

• Link 1 is 10 Km

• Link 2 is 12 Km

• Please calculate Link budget for both Links

• Frequency is 5 GHz

Example 1

Network Diagram

Site # Cameras

S1 1

S2 2

S3 1

S4 1

S5 2

Solution

• First we need to calculate the data rate required in each link

• Link 1 = S1 + S2 +S4 = 4 Cameras

• So Link 1 data rate = 4 Mbps x 4 = 16 Mbps

• Link 2 = S3 + S5 = 3 Cameras

• So Link 2 data rate = 4 Mbps x 3 =12 Mbps

• From the table pick the right receive sensitivity and then

calculate the link budget.

• Receive Sensitivity for Link 1 is -91.67 dBm

• Link 1 FSL = 32.44 + 20 * log(d) + 20 log(f)

• = 32.44 + 20 * log (10) + 20 * log (5000) = 126.42 dB

• Receive Sensitivity for Link 1 is -94.43 dBm

• Link 2 FSL = 32.44 + 20 * log(d) + 20 log(f)

• = 32.44 20 * log (12) + 20 * log (5000) = dB 128

Link1 – Link Budget Diagram

•18

Link 1: Link budget Calculation

30 dBm (TX Power AP)

0 dB (Cable Losses AP) + 18 dBi (Antenna Gain AP)

-126.42 dB (free space loss @5 km)

+ 18 dBi (Antenna Gain Client) 0 dB (Cable Losses Client)

-60.42 dBm (expected received signal level)

- -91.68 dBm (sensitivity of Client)

31.26 dB (link margin)

Link2 – Link Budget Diagram

•18

Link 2: Link budget Calculation

30 dBm (TX Power AP)

0 dB (Cable Losses AP) + 18 dBi (Antenna Gain AP)

-128 dB (free space loss @5 km)

+ 18 dBi (Antenna Gain Client) 0 dB (Cable Losses Client)

-62 dBm (expected received signal level)

- -94.43 dBm (sensitivity of Client)

32.43 dB (link margin)