Wireless Technologies Chapter 9

Learning Objectives Explain current wireless networking technologies Discuss history of wireless networks and their advantages Describe radio wave technologies Explain 802.11 radio wave networking continued…

Learning Objectives Describe 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 technologies 802.11 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 install Reduce network installation costs Provide access anywhere (mobile computing) Simplify networks for novices; enable easier small and home office networking Enhance data access

Wireless Network Support Organizations Wireless LAN Association (WLANA) WINLAB

Radio Wave Technologies Transmit signal in one or multiple directions, depending on type of antenna Use line-of-sight and spread spectrum communications Used for short distance communications Main types IEEE 802.11 standard Alternative 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 communications Also called IEEE Standard for Wireless LAN Medium Access (MAC) and Physical Layer (PHY) Specifications Encompasses either fixed or mobile wireless data communications Involves two kinds of communications Asynchronous communications Those governed by time restrictions continued…

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 Components Wireless NIC (WNIC) Access points Antennas Directional 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 Errors Automatic repeat-request (ARQ) 802.11 error handling technique Helps reduce communication errors created by sources of interference, such as adverse weather

Transmission Speed Standards Uses orthogonal frequency-division multiplexing (OFDM) 802.11b Uses direct sequence spread spectrum modulation (DSSS) 802.11g Emerging as extension of 802.11b standard

Characteristics of 802.11a and 802.11b

Security Techniques Open system authentication Shared key authentication Employs Wired Equivalent Privacy (WEP)

Using Authentication to Disconnect Prevents two communicating stations from being inadvertently disconnected by another non-authenticated station

802.11 Network Topologies Independent 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) topology One or more access points provide a larger service area

IBBS Wireless Topology

Multiple-Cell Wireless LANs ESS wireless topology that employs two or more access points Cell Broadcast 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)

Bluetooth Uses the 2.4 GHz band that is defined through Bluetooth Special Interest Group Uses time division duplexing (TDD)

HiperLAN Uses 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 SWAP Uses the 2.4 GHz band Targeted for home use

Infrared Technologies Used for short distance communications Diffused infrared Transmits 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 Technologies Used for longer distance communications Two forms Terrestrial 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 Will be positioned around Earth for a global area network Does not have same transmission delays as geosynchronous satellites Disadvantages Not 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 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 Subject to interference from other light sources Does not go through walls Not as many device choices Expensive to install and maintain Subject to interference from rain, snow, fog, EMI, atmospheric conditions Not available until 2005

Chapter Summary Brief history and advantages of wireless networking Currently used forms of wireless networking Radio wave technologies IEEE 802.11 wireless networking standard Alternative radio wave technologies Diffused infrared technologies for relatively secure wireless communications Land-based and satellite microwave technologies for networking, including LEO satellites