Wireless Networking Technologies - Nottinghampszgtr/G64INC/L11WirelessTech2PerPage.pdf · 1 Part 3 – Packet Switching and Network Technologies Wireless Networking Technologies Gail

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Part 3 – Packet Switching and

Network Technologies

Wireless Networking

Technologies

Gail Hopkins



Introduction

Here we will be discussing wireless

communication technologies for a range of

distances

Wireless has multiple technologies Many have similar characteristics

Wide range of networks and distances

Partly due to Government regulations that make

specific ranges of the EM spectrum available for

communication

This lecture will cover some of these

technologies

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Taxonomy of Wireless

Networking Technologies

Wireless Networks

Local Area Networks (LANs)

Metropolitan Area Networks

(PANs)

Wide Area Networks (WANs)

Personal Area Networks (PANs)

From Comer, 2009



Personal Area Networks (PANs)

Type Purpose

Bluetooth Communication over a short distance

between a small peripheral devices such

as a headset or a mouse and a system

such as a mobile phone or a computer

InfraRed Line-of-sight communication between a

small device, often a hand-held

controller, and a nearby system such as

a computer or entertainment centre

ISM wireless Communication using frequencies set

aside for Industrial Scientific and

Medical devices, an environment where

EM interference may be present

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ISM Wireless Bands Used by

LANs and PANs

From Comer, 2009



Wireless LAN Technologies and

Wi-Fi IEEE Standard Frequency Band Data Rate

Original 802.11 2.4 GHz 1 or 2 Mbps

Original 802.11 InfraRed 1 or 2 Mbps

802.11a 5.725 GHz 6 to 54 Mbps

802.11b 2.4 GHz 5.5 and 11 Mbps

802.11g 2.4 GHz 22 and 54 Mbps

Different standards may use:

Different modulation techniques (e.g. PSK)

Different multiplexing techniques

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Spread Spectrum Techniques

Spread spectrum transmission uses multiple frequencies to send data Sender spreads data across multiple frequencies

Receiver combines information from these frequencies to rebuild the original data

Different techniques use different ways of doing this

Two alternative reasons for using spread spectrum: Increase overall performance

Make transmission more immune to noise



Other Wireless LAN Standards

Many standards created by IEEE! For different types of communication

Each standard specifies: Frequency range

Modulation technique

Multiplexing technique

Data rate

Different standards have different advantages, e.g.: 802.11i – enhanced security

802.11n – data rate > 100Mbps to handle video applications

802.11r – improved reliability to roam among access points without losing connectivity

Latest standards – 802.11ac, 802.11ad!!!!

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Wireless LANs

Three key parts to a wireless LAN:

Access points

Aka base stations

Switch or router

Used to connect access points

Set of wireless hosts

Aka wireless nodes or wireless stations



Wireless LANs (2) 802.11 standard (WiFi), works in 2 modes:

Infrastructure

Wireless host only communicates with an access point

Access point relays all packets

Ad hoc

Wireless hosts communicate among themselves without a base station

Infrastructure with base station Ad hoc networking

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Achieving Mobility with a

Wireless LAN

Wireless Access

Point

Switch or router

Basic Service

Set (BSS) 1

BSS 2



Overlap and Association

Multiple access points are used to cover a large area

The network consists of multiple cells

If a pair of access points are too far apart

Dead zone

If too close together

Overlap

If a client is within range of multiple access points it has

to associate with a single access point

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Overlap and Association (2)

If a client is within range of multiple access points it has to associate with a single access point

The 802.11 frame format therefore also carries the MAC address of the access point

From Comer, 2009



Coordination Among Access

Points

Early more complex access points

coordinated among themselves to handoff

as a wireless device moved from one access

point’s region to another

E.g. Some used a measure of signal strength

Alternatively, lower cost access points

operate independently

Rely on wireless devices to change their

association from one access point to another

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PAN Technologies Example -

Bluetooth Short distance wireless connection technology

Replacement for cables, for linking devices within a small area

Up to 5 metres (variations extend range to 10 or 50m)

Operates at 2.45 GHz

Spread spectrum frequency hopping

1600 hops per second across chosen frequencies

Voice 64 Kbps, data up to 721 Kbps



Bluetooth Architecture

Basic unit – piconet

Master node, up to 7 active slaves, up to 255 parked nodes (low-power state)

Centralised TDM system

All communication is between master and slave

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Wireless WAN Technologies

Example – Cellular Communication

Systems Originally designed for providing voice

services to mobile phone customers

Now used heavily for data too

System consists of cells, each containing a

transmitter (Base Station Controller (BSC))

Cells placed side-by-side to cover large areas

Group of cells connected to a Mobile Switching

Centre (MSC)



Achieving Mobility with Cellular

Telephony

Mobile Switching

Centre (MSC)

Cell

Base station

Gateway MSC

GSM 850-1900 MHz

3G (UMTS) – 2.1 GHz

Base Station

Controller (BSC)

BSC

PSTN

Mobile Switching

Centre (MSC)

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Cellular Communications

Adjacent cells use different frequencies to

prevent interference

When a user moves between cells that

connect to the same MSC, the MSC handles

the change-over (handoff)

When a user moves between different

geographic regions, two MSCs handle the

change-over



Cellular Communications (2)

In theory, the cells are hexagonal-shaped

In practice they aren’t!

Also, obstructions and electrical interference

can attenuate a signal or cause an irregular

pattern

In built up areas, more cells are used which are

more tightly packed together

In rural areas, cells cover a larger area

Lower density of subscribers

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Generations of Cellular

Technologies

Four generations:

1G, 2G, 3G, 4G

With intermediate versions; 2.5G, 3.5G



Generation Date Purpose

1G Late 1970s through 1980s Used analogue signals to carry

voice

2G and 2.5G Early 1990s, still used today Uses digital signals to carry voice.

2.5G extends 2G to include some

3G features

3G and 3.5G 2000s Addition of higher speed data

services. Download rates of

400Kbps to 2Mbps. Intended to

support web browsing, photo

sharing, etc.

4G 2008 onwards Support for real-time multimedia,

e.g. TV programs/high-speed video

download. Includes multiple

connection technologies, e.g. Wi-Fi

and satellite. Phone chooses best

connection technology at any time.

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Summary

An introduction to wireless communication

technologies

Personal Area Networks

Wireless LANs and Wi-Fi

Examples: Bluetooth and Cellular phone

network

Reading:

Chapter 16 , Computer Networks and Internets,

Comer, 5th Edition, 2009

Documents

Wireless Networking Technologies - Nottinghampszgtr/G64INC/L11WirelessTech2PerPage.pdf · 1 Part 3 – Packet Switching and Network Technologies Wireless Networking Technologies Gail