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
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
7.
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
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 Spectrum (1)
Broadcast TV
• VHF: 54 to 88 MHz, 174 to 216 MHz
• UHF: 470 to 806 MHz
30 MHz
300 MHz
3 GHz
FM Radio
• 88 to 108 MHz
Digital TV
• 54 to 88 MHz, 174 to 216 MHz, 470 to 806 MHz
Wireless Environment and
Wireless LANs
13
30 GHz
14. Wireless Spectrum (2)
3G Broadband Wireless
• 746-794 MHz, 1.7-1.85 GHz, 2.5-2.7
GHz
30 MHz
300 MHz
3 GHz
30 GHz
Cellular Phone
• 800-900 MHz
Personal Communication Service (PCS)
• 1.85-1.99 GHz
Wireless Environment and
Wireless LANs
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15. Wireless Spectrum (3)
Wireless LAN (IEEE
802.11b/g)
• 2.4 GHz
30 MHz
300 MHz
Bluetooth
• 2.45 GHz
Wireless Environment and
Wireless LANs
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Wireless LAN
(IEEE 802.11a)
• 5 GHz
3 GHz
30 GHz
Local Multipoint Distribution
Services (LMDS)
• 27.5-31.3 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
Wireless Environment and
Wireless LANs
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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
Wireless Environment and
Wireless LANs
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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
Wireless Environment and
Wireless LANs
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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
Wireless Environment and
Wireless LANs
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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
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.
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.
