CHAPTE R 16 Wireless Networking Technologies
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Transcript of CHAPTE R 16 Wireless Networking Technologies
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CHAPTER 16Wireless Networking
Technologies
CECS 474 Computer Network Interoperability
Notes for Douglas E. Comer, Computer Networks and Internets (5th Edition)
Tracy Bradley Maples, Ph.D.Computer Engineering & Computer ScienceCal ifornia State University, Long Beach
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Wireless Network Taxonomy
• Wireless communication includes a wide range of network types and sizes.
• Government regulations that make specific ranges of the electromagnetic spectrum available for communication
• A license is required to operate transmission equipment in some parts of the spectrum and other parts of the spectrum are unlicensed
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Personal Area Networks (PANs) • A PAN technology provides communication over a short distance.
• It is intended for use with devices that are owned and operated by a single user. • IEEE has assigned the number 802.15 to PAN standards.
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Bluetooth The IEEE 802.15.1a Standard evolved after vendors created Bluetooth technology as a short-distance wireless connection technology.
The characteristics of the Bluetooth technology are:• Wireless replacement for cables (e.g., headphones or mouse)• Uses 2.4 GHz frequency band• Short distance (up to 5 meters, with variations up to 10 or 50 meters)• Device is either master or slave • Master grants permission to slave• Data rate is up to 721 Kbps
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Wireless LAN Standards (WiFi)
Standards from the first years of WiFi:
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Wireless LAN Standards (WiFi) (cont’d)
More recent WiFi standards:
802.11ac – Preliminary versions now showing up in new WiFi Routers.-- WLANs on the 5 GHz frequency bands-- Final standard approval expected in early 2014-- Expected total multi-station throughput of 1 Gbps; single link throughput 500 Mbps-- Extends 802.11n capabilities with: wider RF band & up to 8 MIMO spatial streams
802.11n – Standardized in 2009.
-- Extends 802.11b and .11g -- Uses the 2.4 GHz and 5 GHz frequency bands-- Expected total multi-station throughput of 600 Mbps -- Uses MIMO (Multiple Input Multiple Output) by having multiple antennae at both sender and receiver-- Up to 4 more MIMO spatial streams
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Wireless Local Area Network (WLAN) Architecture
Note: The set of computers within range of a given access point is known as a Basic Service Set (BSS).
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Contention and Contention-Free Access RTS: Request to Send (frame sent to request communication and reserve channel)
CTS: Clear to Send (frame sent confirming reserved channel)
ACK: Acknowledgement
DIFS: Distributed Interframe Space (enough time for the station to sense the medium to see that it is idle)
SIFS: Short Interframe Space (enough time for the transmitting station to switch back to receive mode)
Note: More on this will be discussed in the Wireless Supplement notes.
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Wireless MAN Technology and WiMAX Standardized by IEEE under the category IEEE 802.16.
Two main versions of WiMAX are being developed that differ in their overall approach:
Fixed WiMAX
• refers to systems built using IEEE 802.16-2004 (informally called 802.16d)• does not provide for handoff among access points• provides connections between a service provider and a fixed location
Mobile WiMAX
• Standard 802.16e-2005 (informally called 802.16e)• handoffs among Aps• used for mobile hosts
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Wireless MAN Technology and WiMAX (cont’d) WiMAX offers broadband communication that can be used in a variety of ways:
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Wireless MAN Technology and WiMAX (cont’d)
The key features of WiMAX can be summarized as follows:• Uses licensed spectrum (i.e., offered by carriers)• Each cell can cover a radius of 3 to 10 Km• Uses scalable orthogonal FDM• Guarantees quality of services (for voice or video)• Can transport 70 Mbps in each direction at short distances• Provides 10 Mbps over a long distance (10 Km)
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Cellular Communication Systems
• When moving between two cells belonging to the same MSC the switching center handles the change.
• When a user passes from one geographic region to another, MSCs are involved in the handoff.
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Cellular Communication Systems (cont’d) (a) Perfect cellular coverage occurs if each cell is a hexagon:
• because the cells can be arranged in a honeycomb• in practice, cellular coverage is imperfect
(b) Most cell towers use omnidirectional antennas:• transmit in a circular pattern• obstructions and electrical interference can attenuate a signal or cause an
irregular patterno in some cases, cells overlap and in others, gaps exist with no coverage
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Generations of Cellular Technologies Telecommunications industry divides cellular technologies into four generations: 1G, 2G, 3G, and 4G (with intermediate versions labeled 2.5G and 3.5G) Simplified Descriptions:
1G• Began in the late 1970s, and extended through the 1980s• Originally called cellular mobile radio telephones• used analog signals to carry voice
2G and 2.5G
• Began in the early 1990s and continues to be used• One standard: GSM (General System for Communications)• The main distinction between 1G and 2G arises because 2G uses digital
signals to carry voice• The label 2.5G is used for systems that extend a 2G system to include some
3G features
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Generations of Cellular Technologies (cont’d)
3G and 3.5G• Began in the 2000s• Focuses on the addition of higher-speed data services• A 3G system offers download rates of 400 Kbps to 2 Mbps, and is intended to
support applications such as web browsing and photo sharing• Includes EDGE (Enhanced Data Rates for GSM Evolution) (amongst other
approaches)• 3G allows a single telephone to roam across the world
4G and 4G LTE (Long Term Evolution)
• Began around 2008• Incompatible with 2G and 3G networks and must be implemented separatedly.• Based on GSM/EDGE• Focuses on support for real-time multimedia
o such as a television program or high-speed video• They include multiple connection technologies
o such as Wi-Fi and satelliteo at any time, the phone automatically chooses the best connection
technology available