Lecture 16 Medium Access Control Sublayer Broadband Wireless 802.16 CS 453 Computer Networks Lecture 16 Medium Access Control Sublayer Broadband Wireless 802.16

802.16 Broadband Wireless While 802.11 fills a niche for wireless networking in very limited area… These seems to be an equally compelling need to have a wireless networking technology on a somewhat larger scale rangewise Getting that “final mile” A wireless local loop

802.16 Broadband Wireless IEEE 802.16 was commissioned address this issue… And Local Multipoint Distribution Service was invented to do this In principal a much more cost effective way to provide broadband services that running cable or fiber to local houses and buildings

802.16 Broadband Wireless 802.16 started in July, 1999 Standard approved in April, 2002 Officially “Air Interface for Fixed Broadband Wireless Access Systems” Often called – Wireless local loop WMAN – wireless Metropolitan Area Network WiMax

802.16 Broadband Wireless 802.16 heavily influence by other 802 efforts and by OSI Reference model So, why not just make 802.16 a bigger, stronger 802.11? It fills a difference niche. It has different objectives

802.16 Broadband Wireless Both were designed to provide high bandwidth wireless network access 802.11 was designed to deal with mobility Multiple end-point stations Moving within cells and In and out of cells

802.16 Broadband Wireless 802.16 is intended for connecting buildings… …houses --- fixed location points … no mobility (yet) 802.11 range in 10s of meters 802.16 range in miles

802.16 Broadband Wireless 802.16 transmitting over city, etc. 802.11 is omni-directional 802.16 is uni-directional – can be pointed 802.16 operates in th 10-66 Ghz band (much higher than 802.11) Millimeter wavelengths – Tend to be absorbed by water So error handling is more important 802.16 transmitting over city, etc. Means securing and privacy very important

802.16 Broadband Wireless 802.16 protocol stack Follows OSI model Lower layer have several sublayers Physical layer has several “modules” depending distance/modulation

802.16 Broadband Wireless … continued 802.16 Physical Layer Because of millimeter band signal strength falls off rapidly with distance… Difference modulation techniques are used at different distances to achieve different data rates … continued

802.16 Broadband Wireless Modulation and data rates Short distance = QAM-64 – 6 bits/baud Medium distance = QAM-16 – 4 bits/baud Long distance = QPSK – 2 bits/baud At 125 MHz of bandwidth QAM-64 = 150 Mbps QAM-16 = 100 Mbps QPSK = 50 Mbps

802.16 Broadband Wireless 802.16 allocations bandwidth Frequency Division Multiplexing (FDM) Time Division Multiplexing (TDM) Frames contain subframes (time slots) Base station decide how many subframes are for Downstream data and how many are for upstream data Base station can adjusts proportion of downstream/upstream subframes depending on data flow A station can request a bandwidth allocation

802.16 Broadband Wireless 802.16 Uses RSA Public Key encryptions Only encrypts payload …rest of frame in clear

802.16 Broadband Wireless 802.16 – Four classes of services Constant bit rate service Automatic allocation of subframes Voice and similar applications Real-time variable bit rate service Compressed video Needs to transmit but irregular flow OK Non-real-time variable rate service Heavy transmission, but not real time Data file transfers Best-effort service As available bandwidth

802.16 Broadband Wireless Frame Structure O = data frame 1= bandwidth frame EC = payload encrypted CI = type(pack/fragmenting EK = Ids encryptions keys Length = Len of frame Connection Identifier = which connnection Header CRC = CRC of header only From: Tanenbaum (2003) pg. 309

Bluetooth More Information: http://www.bluetooth.com/bluetooth/ http://en.wikipedia.org/wiki/Bluetooth

Bluetooth Developed out of an interest by a cell phone manufacturer for a way for cell phone to connect to other devices sans cables SIG created from Erricson, IBM, Intel, Nokia, and Toshiba… … to develop standards Bluetooth SIG standards in 1999 IEEE jumped in later …became 802.15

Bluetooth Ever wonder where the name came from? Harold Gormson (Harold I of Denmark), a Viking king

Bluetooth 802.11 intended to serve buildings Range ~ hundred meters Bluetooth intended to serve a room Much more of a personal area network Short run cable replacement (at least originally) Range: 10 meter (that was the idea anyway)

Bluetooth Bluetooth architecture Small radio cell – piconet Piconet about 10 meters Multiple piconets can be bridged Cell has one master node… … and up to seven slave nodes Can have up to 255 parked nodes Master does all parking (valet?)

Bluetooth Bluetooth architecture Master does all control Slave only does what Master says This allow very cheap slave electronics (plan was for under $5 per chip All communications must be master/slave, slave/master… Never slave/slave Bandwidth allocation via TDM

Bluetooth Bluetooth architecture 3 classes of radios used in Bluetooth Class 3 radios – have a range of up to 1 meter or 3 feet Class 2 radios – most commonly found in mobile devices – have a range of 10 meters or 30 feet Class 1 radios – used primarily in industrial use cases – have a range of 100 meters or 300 feet From: http://www.bluetooth.com/bluetooth/

Bluetooth Bluetooth architecture Uses 2.4 Ghz ISM band Uses FHSS 1600 Hops/second Dwell time 625 microseconds 79 channels 1 Mhz each FSK modulation Uses same band/same channels as 802.11, garage door remotes, cordless phones, etc.

Bluetooth Bluetooth application profiles From: Tanenbaum, 2003, pg. 312

Bluetooth Bluetooth links ACL – Asynchronous Connection Less Packet switching irregular data Slave can only have one ACL link with master Synchronous Connection Oriented Real-time data Like voice, etc. Slave can have up to 3 SCO links to master

Bluetooth Bluetooth SCO payload always 240 bits ACL payload 80, 160, 240 Master uses even slots Slave uses odd slots

Bluetooth Bluetooth frames Ack = piggybacking Ack on frame Seq = number frames (one bit?) Header repeated 3 times Addr = address of one of eight active devices Type = ACL, SCO, Polling, null Flow = slave wants pause