CHAPTE R 16 Wireless Networking Technologies

1. CECS 474 Computer Network Interoperability CHAPTER16 Wireless NetworkingTechnologies Tracy Bradley Maples, Ph.D. Computer Engineering & Computer Science Cal ifornia State University, Long Beach Notes for Douglas E. Comer, Computer Networks and Internets (5th Edition)

2. 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

3. 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.

4. 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

5. Wireless LAN Standards (WiFi) Standards from the first years of WiFi:

6. Wireless LAN Standards (WiFi) (cont’d) More recent WiFi standards: 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 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

7. 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).

8. 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 InterframeSpace (enough time for the station to sense the medium to see that it is idle) SIFS: Short InterframeSpace (enough time for the transmitting station to switch back to receive mode) Note: More on this will be discussed in the Wireless Supplement notes.

9. 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

10. Wireless MAN Technology and WiMAX (cont’d) WiMAX offers broadband communication that can be used in a variety of ways:

11. 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)

12. 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.

13. 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 pattern • in some cases, cells overlap and in others, gaps exist with no coverage

14. 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

15. 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 • such as a television program or high-speed video • They include multiple connection technologies • such as Wi-Fi and satellite • at any time, the phone automatically chooses the best connection technology available