presented by mrs. vasanthi muniasamy m.sc.,...

Presented By

Mrs. Vasanthi Muniasamy M.Sc., M.Phil

INTRODUCTION Wireless network is an interconnection of many systems

capable of providing service to mobile users within a particular geographic region (country or continent)

In wireless network, data are carried by electrical wave (e.g., radio wave) from one node to another.

There is no physical cable/wire connecting one computer to another

Components

Base station

Mobile Switching Center (MSC)

PSTN (Public Telecommunication Switching Network)

Wired (Cabled) Network versus Wireless Network

Advantages of Wireless Network over Wired (Cabled) Network

Mobility: Users can roam around the network without being disconnected

Installation speed and cost: Building wireless medium to large network is usually faster and cheaper than building wired (cabled) medium to large network because there is no need to pull cable through walls and ceilings

Reach of network: Wireless network can be extended to places where wire/cable cannot reach

Flexibility/scalability: New computers can be added easily without having to pull cable into the computers

Disadvantages of Wireless Network compared to Wired Network

Speed: In general, wireless network technology is slower than wired network technology

Security: In general, wireless network is less secured than wired network

Basic Components of Wireless Network

Wireless Network Hardware

Wireless NIC (e.g., wireless Ethernet NIC or Bluetooth NIC) must be installed in each computer

Major functions of wireless NIC:

Sender NIC: Take data from Layer 3 (Network Layer)

Encapsulate the data into frame

Load the frame to electrical wave

Transmit the electrical wave

Receiver NIC performs the reverse activities

Wireless NIC comes in various forms (Eg., Expansion board, PCMCIA, USB, built-in)

Wireless Network Hardware

Wireless Access Point (WAP/Access Point/AP/Universal Access Point/UAP)

Central “wiring” device to connect wireless nodes to wireless/wired network

If a network uses WAP, all computers must communicate via the WAP

Wireless Network Mode

Ad-Hoc Mode (Peer-to-Peer Mode) Each wireless node can communicate directly with each of the other nodes in the

network (without Wireless Access Point)

Mesh network topology

IBSS (Independent Basic Service Set): a group of nodes communicating in ad-hoc mode

Infrastructure Mode All wireless node communicate to one another via Wireless Access Point

Star network topology

BSS (Basic Service Set): a group of nodes communicating in infrastructure mode.

An BSS has one wireless access point

EBSS (Extended Basic Service Set): two or more BSS that can communicate to one another

An EBSS contains two or more wireless access points

Ad-Hoc versus Infrastructure Mode

Ad-Hoc Mode (IBSS)

Infrastructure Mode (BSS)

Wireless Network Security

Three basic wireless network security methods:

SSID (Service Set Identification)

MAC Address Filtering

Encryption

Wireless network Speed

Wireless network speed depends on:

The wireless network technology standard

The distance between sender and receiver, or between a node and a Wireless Access Point

Interference from other wireless devices or electronic devices (e.g., wireless phone)

The presence of solid object (especially metal object, electronic appliance) between the sender and receiver, or between a node and a Wireless Access Point

Wireless Network Range

Wireless network range depends on: The wireless network technology standard

Interference from other wireless devices or electronic devices

The presence of solid object (especially metal object, electronic appliance) between the sender and receiver, or between a node and a Wireless Access Point

To increase the wireless network range: Using “signal booster”

Using Wireless Access Point (i.e., instead of using ad-hoc mode, use infrastructure mode)

Using MULTIPLE Wireless Access Points

Wireless Environment and Wireless LANs

13

Wireless Spectrum (1)

30 MHz 30 GHz3 GHz300 MHz

Broadcast TV• VHF: 54 to 88 MHz, 174 to 216 MHz• UHF: 470 to 806 MHz

FM Radio• 88 to 108 MHz

Digital TV• 54 to 88 MHz, 174 to 216 MHz, 470 to 806 MHz


14



3G Broadband Wireless• 746-794 MHz, 1.7-1.85 GHz, 2.5-2.7 GHz

Cellular Phone• 800-900 MHz

Personal Communication Service (PCS)• 1.85-1.99 GHz


15



Wireless LAN (IEEE 802.11b/g)• 2.4 GHz

Local Multipoint Distribution Services (LMDS) • 27.5-31.3 GHz

Bluetooth• 2.45 GHz

Wireless LAN (IEEE 802.11a)• 5 GHz


16

Evolution of Mobile Wireless (1)Advance Mobile Phone Service (AMPS)• FDMA• 824-849 MHz (UL), 869-894 MHz (DL)• U.S. (1983), So. America, Australia, China

European Total Access Communication System (E-TACS)• FDMA• 872-905 MHz (UL), 917-950 MHz (DL)• Deployed throughout Europe


17

Evolution of Mobile Wireless (2)Global System for Mobile communications (GSM)• TDMA• Different frequency bands for cellular and PCS• Developed in 1990, expected >1B subscriber by end of 2003

IS-95• CDMA• 800/1900 MHz – Cellular/PCS• U.S., Europe, Asia


18

Evolution of Mobile Wireless (3)General Packet Radio Services (GPRS)• Introduces packet switched data services for GSM• Transmission rate up to 170 kbps• Some support for QoS

Enhanced Data rates for GSM Evolution (EDGE)• Circuit-switched voice (at up to 43.5 kbps/slot)• Packet-switched data (at up to 59.2 kbps/slot)• Can achieve on the order of 475 kbps on the downlink, by combining multiple slots


19

Evolution of Mobile Wireless (4)Universal Mobile Telecommunication Systems (UMTS)• Wideband DS-CDMA• Bandwidth-on-demand, up to 2 Mbps• Supports handoff from GSM/GPRS

IS2000• CDMA2000: Multicarrier DS-CDMA• Bandwidth on demand (different flavors, up to a few Mbps)• Supports handoff from/to IS-95

Generations in Mobile Wireless Service

First Generation (1G) Mobile voice services

Second Generation (2G) Primarily voice, some low-speed data (circuit switched)

Generation 2½ (2.5G) Higher data rates than 2G

A bridge (for GSM) to 3G

Third Generation (3G) Seamless integration of voice and data

High data rates, full support for packet switched data

Block Diagram of Cellular System

Development of Wireless Networks First Generation Wireless Networks

Second Generation Wireless Networks

Third Generation Wireless Networks

Fixed Network transmission Hierarchy

Traffic Routing in Wireless Networks

Circuit Switching

Packet Switching

X.25 Protocol

First Generation Wireless Networks

Mobile

User

Base

Station

MSC

Second Generation Wireless Networks Employs digital modulation and advanced call

processing capabilities Ex: GSM, TDMA ,CDMA, Cordless Phones.

Dedicated control channel for voice, signal data.

Provides paging and other data services.

High data rate (N/W access.)

Uses MAHO (Mobile Assisted Hand Off) where mobile units performs the following functions: reporting received power.

scanning adjacent base station.

data encoding and encryption.

Third Generation Wireless Networks

Aim: to provide single set of standards that can meet wide range of applications and provide universal access thru out the world.

Distinction between cordless and cellular phones disappear as personal handset provides access to voice, data and video services.

It uses broadband integrated service digital N/W (ISDN) to provide internet for both fixed or mobile users.

Provides reliable transfer of information.

Traffic Routing in Wireless Networks

1. Circuit Switching

2. Packet Switching

3. X.25 Protocol

Circuit Switching

There are three phases in circuit switching:

Establish

Transfer

Disconnect

The telephone message is sent in one go, it is not broken up. The message arrives in the same order that it was originally sent.

Packet Switching

In packet-based networks, the message gets broken into small data packets. These packets are sent out from the computer and they travel around the network seeking out the most efficient route to travel as circuits become available. This does not necessarily mean that they seek out the shortest route.

Each packet may go a different route from the others.

Packet Switching HEADER USER DATA TRAILER

FLAG ADDRESS

FIELD

CONTROL FIELD INFORMATION

FIELD

FRAME CHECK

SEQUENCE FIELD

Packet Data Format

Fields in a Typical packet data

presented by mrs. vasanthi muniasamy m.sc.,...

Documents