Wireless Technologies

Chapter 9

Learning ObjectivesExplain current wireless networking technologies

Discuss history of wireless networks and their advantages

Describe radio wave technologies

Explain 802.11 radio wave networking

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Learning ObjectivesDescribe alternative radio wave technologies: Bluetooth, HiperLAN, and HomeRF Shared Wireless Access Protocol

Discuss infrared wireless technologies

Describe microwave technologies

Explain low Earth orbiting (LEO) satellite wireless networking

Current Wireless Networking Technologies

Radio wave technologies802.11 wireless standard

Alternative approaches

Infrared technologies

Microwave technologies

Low Earth orbiting (LEO) satellite wireless networking

Short History of Wireless Networks

Informal beginning in early experimentation with packet radio performed by amateur radio operators

Advantages of Wireless Networks

Enable communications in areas where wired networks are difficult to installReduce network installation costsProvide access anywhere (mobile computing)Simplify networks for novices; enable easier small and home office networkingEnhance data access

Wireless Network Support Organizations

Wireless LAN Association (WLANA)

WINLAB

Radio Wave TechnologiesTransmit signal in one or multiple directions, depending on type of antennaUse line-of-sight and spread spectrum communicationsUsed for short distance communicationsMain types

IEEE 802.11 standardAlternative technologies

Radio Wave Technologies

Radio Wave Technologies: Advantages

Inexpensive alternative where communications cabling cannot be installed easily

Option for portable communications

Usually no licensing requirements

Radio Wave Technologies: Disadvantages

May not be feasible for high-speed networking requirements

Subject to interference from the military, radio, cell phones, and other sources

Subject to interference from natural obstacles

IEEE 802.11 Radio Wave Networking

Not reliant on proprietary communicationsAlso called IEEE Standard for Wireless LAN Medium Access (MAC) and Physical Layer (PHY) SpecificationsEncompasses either fixed or mobile wireless data communicationsInvolves two kinds of communications

Asynchronous communications Those governed by time restrictions

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IEEE 802.11 Radio Wave Networking

Includes support for network management services (eg, SNMP protocol) and network authentication

Focuses on use of OSI Data Link and Physical layers

Recognizes indoor and outdoor wireless communications

How IEEE 802.11 Wireless Networks Function

Components

Access methods

Handling data errors

Transmission speeds

Security techniques

Using authentication to disconnect

802.11-based topologies

Using multiple-cell wireless LANs

Wireless ComponentsWireless NIC (WNIC)

Access points

AntennasDirectional antenna

Omnidirectional antenna

Directional Antenna

Omnidirectional Antenna

Wireless Networking Access Methods

Priority-based access

Carrier-sense multiple access with collision avoidance (CSMA/CA)

Handling Data ErrorsAutomatic repeat-request (ARQ)

802.11 error handling technique

Helps reduce communication errors created by sources of interference, such as adverse weather

Transmission Speed Standards

802.11aUses orthogonal frequency-division multiplexing (OFDM)

802.11bUses direct sequence spread spectrum modulation (DSSS)

802.11gEmerging as extension of 802.11b standard

Characteristics of 802.11a and 802.11b

Security TechniquesOpen system authentication

Shared key authenticationEmploys Wired Equivalent Privacy (WEP)

Using Authentication to Disconnect

Prevents two communicating stations from being inadvertently disconnected by another non-authenticated station

802.11 Network TopologiesIndependent basic service set (IBSS) topology

Two or more wireless stations that can be in communication

Does not use an access point

Ad hoc peer-to-peer communication between WNICs on individual computers

Extended service set (ESS) topologyOne or more access points provide a larger service area

IBBS Wireless Topology

Multiple-Cell Wireless LANsESS wireless topology that employs two or more access points

CellBroadcast area around a single access point

Inter-Access Point Protocol (IAPP)Roaming protocol that enables a mobile station to move from one cell to another without losing connection

Alternative Radio Wave Technologies

Bluetooth

HiperLAN

HomeRF Shared Wireless Access Protocol (SWAP)

BluetoothUses the 2.4 GHz band that is defined through Bluetooth Special Interest Group

Uses time division duplexing (TDD)

HiperLANUses the 5 GHz band

Compatible with Ethernet and ATM communications

Popular in Europe

Supports Data Encryption Standard (DES) and QoS

Operates in direct or centralized mode

HomeRF SWAPUses the 2.4 GHz band

Targeted for home use

Infrared TechnologiesUsed for short distance communications

Diffused infraredTransmits by reflecting infrared light from the ceiling

Used by 802.11R standard

Uses pulse position modulation (PPM)

Diffused Infrared Wireless Communications

Infrared Technologies: Advantages

Signal is difficult to secretly interpret

Infrared Technologies: Disadvantages

May not be feasible when high-speed communications are needed

Subject to interference from other light sources

Does not go through walls

Does not offer as many device choices as other forms of wireless networking

Microwave TechnologiesUsed for longer distance communications

Two formsTerrestrial microwave

Satellite microwave

Terrestrial Microwave

Satellite Microwave

Microwave Technologies: Advantages

Inexpensive alternative where communications cabling cannot be installed easily, particularly over long distances

Terrestrial microwave may be less expensive in the long run than leasing telecommunications lines

Microwave Technologies: Disadvantages

May not be feasible when high-speed communications are needed

Expensive to install and maintain

Subject to interference from rain, snow, fog, EMI, and atmospheric conditions

LEO Satellite Wireless Networking

Network of communications satellites that orbit above Earth between 435 and 1000 miles

Global LEO Network

LEO Satellite: Advantages and Disadvantages

AdvantagesWill be positioned around Earth for a global area network

Does not have same transmission delays as geosynchronous satellites

DisadvantagesNot available until 2005

Summary of Advantages of Wireless Communications

Radio Wave Infrared Microwave LEO Satellite Inexpensive

alternative where cabling is not easy to install

Option for portable communications

Usually no licensing requirements

Signal is difficult to interpret secretly

Inexpensive alternative where cabling is not easy to install

Terrestrial microwave costs less than leasing telecommunica-tions lines

Will be positioned around Earth for a global area network

Does not have same transmission delays as geosynchronous satellites

Summary of Disadvantages of Wireless Communications

Radio Wave Infrared Microwave LEO Satellite

May not be feasible for high-speed networks

Subject to interference from military, radio, and cell phones

Subject to interference from natural obstacles

May not be feasible for high-speed networks

Subject to interference from other light sources

Does not go through walls

Not as many device choices

May not be feasible for high-speed networks

Expensive to install and maintain

Subject to interference from rain, snow, fog, EMI, atmospheric conditions

Not available until 2005

Chapter SummaryBrief history and advantages of wireless networkingCurrently used forms of wireless networking

Radio wave technologiesIEEE 802.11 wireless networking standardAlternative radio wave technologies

Diffused infrared technologies for relatively secure wireless communicationsLand-based and satellite microwave technologies for networking, including LEO satellites