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Broadband Wireless

Broadband Wireless. The “wave” of the future . Presentation Outline. Introduction Brief background and definition of the 802.16 protocol. Differences between 802.11 and 802.16 and Why do we need another wireless protocol. In depth analysis The 802.16 protocol stack Data Link Layer

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Broadband Wireless

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Presentation Transcript

  1. Broadband Wireless The “wave” of the future.

  2. Presentation Outline • Introduction • Brief background and definition of the 802.16 protocol. • Differences between 802.11 and 802.16 and • Why do we need another wireless protocol. • In depth analysis • The 802.16 protocol stack • Data Link Layer • Security, • MAC • MAC Frame Format • Service Specific convergence sublayers • Physical Layer • Specifications • Typical Transmission/Reception setup • Bandwidth Allocation • TDD break down • General Comparisons • Reliability • Error Detection/Correction • Availability • Some Numbers • Some Advantages • What lies Ahead? • Conclusion • Q & A session • References

  3. Introduction

  4. Background • Broadband wireless is known to the networking world as protocol 802.16 or WirelessMAN (Metropolitan Area Network). This protocol was developed by IEEE to answer the need for the standardization of broadband wireless. It was developed after protocol 802.11 which is also a broadband wireless protocol. • Note – It is a common misconception that protocols 802.11 and 802.16 are the same.

  5. Differences between 802.11 and 802.16 • The 802.11 protocol was designed for relatively short distances of only about 300 feet in doors and 1,200 feet out of doors. It also was not designed to serve a large number of users. WirelessMAN, on the other hand, was designed from the "ground up" specifically to tackle the tough requirements of making wireless broadband work over longer distances and through more difficult environments, such as heavily wooded areas(4). • 802.16 uses full duplex in its communication, which 802.11 avoids to keep the cost of radios low. • 802.11 deals with mobility, where 802.16 provides service to buildings.

  6. Why do we need another wireless protocol? • 802.16 and 802.11 solve different problems. • Running fiber, coax, or even category 5 twisted pair to millions of homes and businesses is prohibitively expensive. • The capacity of a physical medium has a given maximum and is not very flexible • Buildings have more than one computer in them, a complication that the 802.11 protocol does not handle. • A protocol to service a high volume of consumers is needed. • The wireless MAN world is far more demanding than the mobile phone world

  7. In-Depth Analysis of 802.16

  8. The 802.16 protocol stack

  9. Protocol Stack Description • The 802.16 protocol stack is generally similar to that of other 802 networks but with more sublayers. • The data link layer consists of three sublayers: Security, MAC, and Service specific convergence. • The physical layer consists of a transmission convergence sublayer, and a physical medium sublayer which uses three modulation schemes.

  10. Data Link Layer Security, MAC, and Service Specific convergence sublayers

  11. Security Sublayer • The security layer deals with privacy, encryption, decryption, and key management. • This layer is especially important because of the wireless nature of the 802.16 protocol. Since the protocol provides open communication over a city, standards and security have are essential and mandatory.

  12. MAC Sublayer • Where main protocols are located. • Base station controls the system, manages up and downstream activity. • Completely connection orientated, unlike the other 802 protocols. • This orientation was chosen to provide quality of service guarantees for telephony and multimedia application(6).

  13. MAC Frame Format • EC – tells whether or not the data is encrypted • Type – tells type of frame, whether packing/fragmenting was used • CI – indicates presence or absence of the final checksum • EK – tells which encryption key is used, if any • Length – complete length of the frame, including header • Conn. ID – tells which connection this frame belongs to • HeaderCRC – checksum over the header only

  14. Service Specific Convergence Sublayer • The SSCS take the place of the logical link sublayer in the other 802 protocols(6). Used to communicate with network layer. • Hides different technologies from the data link layer.

  15. Physical Layer General specifications and information

  16. Physical Layer Specs. • Uses a wide spectrum and therefore must operate in the 10-to-66 GHz range. • Transmits using millimeter waves which travel in straight lines, similar to light. • Signal attenuation, due to distance from the base station, is handled by the three different modulation schemes. • QAM – 64 with 6 bits/baud is used for subscribers at short distances • QAM – 16 with 4 bits/baud is used for subscribers at medium distances • QPSK with 2 bits/baud is used for distant subscribers(6).

  17. Typical transmission/reception setups

  18. More info… • Antennas, unlike those used for cell phones or wireless LAN devices, are typically about 12 inches in diameter, are often located on rooftops, and are pointed in a precise direction. • Antenna towers typically have multiple antennas which point to different sectors. Each sector has its own users and is fairly independent of the adjacent ones(6).

  19. How does 802.16 handle bandwidth allocation? This protocol uses two schemes: • FDD (Frequency Division Duplexing) • TDD (Time Division Duplexing)

  20. Time Division Duplexing • Each frame contains time slots for both down stream and upstream traffic, and also a guard time which is used by the stations to switch direction. • All traffic is controlled and mapped by the base station.

  21. General Comparisons Reliability, Availability, Cost effectiveness, and general comparisons.

  22. How reliable is Broadband Wireless? • BBW transmission is via free space, and is subject to attenuation and distortion by various matter such as vegetation, buildings, precipitation and vehicles, which move and change unpredictably. • BBW is not reliant on a physical medium therefore reducing errors due to capacity limitations, cost, efficiency, and conveniency.

  23. A note on error detection and correction Due the high probability of error during transmission, error detection and correction is done in the higher levels using checksums, and also using Hamming codes in the physical layer. Nearly all other networks rely simply on checksums for error detection/correction.

  24. Availability Issues… • “Fewer than 10 percent of buildings have fiber running to them (1).” • “Of the 21-22 million U.S. broadband households, approximately 200,000 of them are using broadband wireless services. That estimate includes subscribers to services based on licensed and unlicensed broadband wireless technologies(2).” • Since BBW is fairly new to the technology scene, it has not yet become as readily available as typical cable or DSL setups. • BBW providers are much less abundant than cable or DSL providers due to the age and current cost of BBW systems.

  25. $ome numbers…. • “According to (1),What broadband wireless is is much less expensive than fiber. Running fiber to metropolitan buildings can cost up to $250,000 per mile. Pointing an antenna from the top of a building to other rooftops costs one-tenth that—or less.” • “prices for conventional point-to-point microwave radios dropped from $25,000 per pair to less than $15,000 per pair over the last three years (1),.“ • BBW will generate“$5 billion in service revenue in the U.S. by 2003(1).” • Despite the decreasing cost of deployment, BBW systems are still considered more expensive than typical cable or DSL setups.

  26. Some advantages… • Broadband Wireless Accesscan extend fiber optic networks and provide more capacity than cable networks or digital subscriber lines (DSL)(5). • BWA networks can be created in just weeks by deploying a small number of base stations on buildings or poles to create high-capacity wireless access systems(5).

  27. What lies ahead?

  28. What lies ahead? • “According to Ray Nettleton of Forums Communications Inc. (Denver), an LMDS (local multipoint distribution service) provider, within five years wireless broadband will be available anywhere in the world through a combination of terrestrial and satellite links(1).” • 802.16 potentially has the ability and functionality to be used for mobile devices.

  29. Conclusion

  30. To wrap it up…. • Broadband wireless has become the best way to meet escalating business demand for rapid Internet connection and integrated data, voice and video services(5). • Everyday new developments are being made toward a wireless world. Broadband Wireless will soon become an essential, economic, powerful, and efficient tool in the wireless world. • Since the field of Broadband Wireless has already become a vast sea of information, and only a fraction of which was covered in our presentation, we have provided a list of helpful references for any of you who might be interested in further researching Broadband Wireless,

  31. You’ve got questions, we’ve got answers (hopefully).

  32. References • http://www.url1.com/broadband/art_broadband_4.html • http://www.shorecliffcommunications.com/magazine/news.asp?news=2625 • http://grouper.ieee.org/groups/802/16/pub/backgrounder.html • http://www.cawnet.org/pipermail/rfmon/2003-January/002698.html • http://wirelessman.org/pub/backgrounder.html • Tanenbaum, Andrew S. Computer Networks 4th edition, Prentice Hall PTR, New Jersery. 2003.

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