The document provides an overview of wireless networks, including: 1. Wireless networks interconnect systems capable of providing mobile service within a geographic region without physical cables. 2. Components include base stations, mobile switching centers, and public telephone networks. Wireless networks offer mobility, lower installation costs, and flexibility over wired networks but have lower speeds and security. 3. Basic components are wireless network interface cards, access points, and hardware like antennas. Wireless modes include ad-hoc peer-to-peer and infrastructure with access points. Security methods are SSIDs, MAC filtering, and encryption.

1. Presented By
Mrs. Vasanthi Muniasamy M.Sc., M.Phil

2. 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)

3. 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

4. Basic Components of Wireless Network

5. 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)

6. 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

8. 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

9. Ad-Hoc versus Infrastructure Mode
Ad-Hoc Mode
(IBSS)
Infrastructure Mode
(BSS)

10. Wireless Network Security
 Three basic wireless network security methods:
 SSID (Service Set Identification)
 MAC Address Filtering
 Encryption

11. 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

12. 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

13. 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. Wireless Environment and
Wireless LANs
14
Wireless Spectrum (2)
30 MHz 30 GHz3 GHz300 MHz
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 Environment and
Wireless LANs
15
Wireless Spectrum (3)
30 MHz 30 GHz3 GHz300 MHz
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. Wireless Environment and
Wireless LANs
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. Wireless Environment and
Wireless LANs
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. Wireless Environment and
Wireless LANs
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. Wireless Environment and
Wireless LANs
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

20. 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

21. Block Diagram of Cellular System

22. 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

23. First Generation Wireless Networks
Mobile
User
Base
Station
MSC

24. 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.

25. 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.

26. Traffic Routing in Wireless Networks
1. Circuit Switching
2. Packet Switching
3. X.25 Protocol

27. 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.

28. 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.

29. 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