Outline • History • Technology overview • Cellular communications • 1G: AMPS; 2G: GSM; 2.5G: GPRS, EDGE; 3G: UMTS • Satellite systems • Wireless LAN • 802.11, Bluetooth • Mobility support • WAP • Wireless applications
History • Local Area Networks (LANS) • LAN is a fast (~Mb/s), geographically limited (~km) digital communications network which is owned and operated by the user organization. • History of LANs • Packet radio networks (Aloha and Slotted Aloha in Hawaii • Ethernet • The first LAN was an early version Ethernet in 1976, ~ 3 Mb/s • Digital-Intel-Xerox “DIX specification in 1979, 10 Mb/.s • Ethernet 2 in 1982
Aloha Net • One of the first functioning wireless networks in the USA, conceived and implemented at the University of Hawaii campus at Manoa. • Its purpose was to link the University mainframe computer to client computers located on outer islands at University campuses. Put in place in the early 1970s, it was dubed the Aloha Net. Key punch cards were fed through a reader, and sent over the commercial phone lines
Aloha System • First random access system (1971). • Allowed 7 campuses on 4 islands to access main computer with terrestrial microwave. • Each station has an FM transmitter/receiver. • No direct communication between stations. • 407.35 MHz for inbound traffic. Employs random access. • 413.475 MHz for outbound traffic. 9600 bps transmission speed.
The Pure ALOHA Protocol: • Each station is coupled to a single broadcast channel. • Station transmits whenever it has a packet to send. • If there isn't a collision, receiver sends an ack over a separate channel. • If there is a collision, no ack is sent and transmitter times out. Time-out interval is at least as long as 2-way propagation time. • Station retransmits after random amount of time.
Slotted ALOHA: • Packets have equal length of L bits. Packet time is TRANSP = L/R seconds, where R is the transmission rate of the channel. • Time is divided into fixed-length slots of length TRANSP. Clocks in stations are synchronized. • A station can begin transmission only at the beginning of a slot. • The efficiency of slotted ALOHA is the fraction of slots containing successful transmissions when there are many stations and each station has many packets to send. • The maximum efficiency of slotted ALOHA is 1/e = .37. This gives • 37% successes • 37% empty slots • 26% collisions • Throughput in bits/sec is R * efficiency.
Invention of Ethernet • “In late 1972, Metcalfe and his Xerox PARC colleagues developed the first experimental Ethernet system to interconnect the Xerox Alto, a personal workstation with a graphical user interface. • The experimental Ethernet was used to link Altos to one another, and to servers and laser printers. • The signal clock for the experimental Ethernet interface was derived from the Alto's system clock, which resulted in a data transmission rate on the experimental Ethernet of 2.94 Mbps.
Invention of Ethernet • Metcalfe's first experimental network was called the Alto Aloha Network. In 1973 Metcalfe changed the name to "Ethernet," to make it clear that the system could support any computer--not just Altos--and to point out that his new network mechanisms had evolved well beyond the Aloha system. • He chose to base the name on the word "ether" as a way of describing an essential feature of the system: the physical medium (i.e., a cable) carries bits to all stations, much the same way that the old "luminiferous ether" was once thought to propagate electromagnetic waves through space. Thus, Ethernet was born.”
Invention of Ethernet • The diagram ... was drawn by Dr. Robert M. Metcalfe in 1976 to present Ethernet ... to the National Computer Conference in June of that year. On the drawing are the original terms for describing Ethernet.
Ethernet Topologies and Protocols • Traditional Ethernet employs a bus topology, meaning that all devices or hosts on the network use the same shared communication line. Each device possesses an Ethernet address, also known as MAC address. Sending devices use Ethernet addresses to specify the intended recipient of messages.
Ethernet Topologies and Protocols • Data sent over the Ethernet exists in the forms of frames. An Ethernet frame contains a header, a data section, and a footer having a combined length of no more than 1518 bytes. The Ethernet header contains the addresses of both the intended recipient and the sender.
Ethernet Topologies and Protocols • Data sent over the Ethernet is automatically broadcast to all devices on the network. By comparing their Ethernet address against the address in the frame header, each Ethernet device tests each frame to determine if it was intended for them and reads or discards the frame as appropriate. Network adapters incorporate this function into their hardware.
Ethernet Topologies and Protocols • There are four major types of media in use today: Thickwire, thin coax, unshielded twisted pair (UTP), and fiber optic.Ethernet media are used in two basic topologies called "bus" and "star". The topology defines how a node (which is any device such as a computer, printer, or hub) is connected to the network.A bus topology consists of nodes connected together by a single long cable. Each node "taps" into the bus and directly communicates with all other nodes on the bus. The major advantage of this topology is the easy expansion, by adding extra "taps", and the lack a hub. The major disadvantage is that any break in the cable will cause all nodes on the cable to loose connection to the network.A star topology links exactly two nodes together on the network. A hub is used to collection point where many of the connections come together. The major advantage is any single break only disables one host. The major disadvantage is the added cost of a hub.
Ethernet Packet Format preamble start frame source adrs dest adrs length data payload padding CRC
Why Wireless? • Human freedom • Portability v. Mobility • Objective: “anything, anytime, anywhere” • Mobility • Size, weight, power • Functionality • Content • Infrastructure required • Cost • Capital, operational
The m-Commerce “Revolution” 1. High mobile phone penetration: 4 per PC worldwide 2. Convergence of the Internet and the mobile phone 3. Transition to 3rd Generation 4. Personalization, location- & context-sensitive applications and services
(in millions) 1800 1600 1400 1200 Rest of World 1000 Asia Pacific North America 800 European Union 600 400 200 0 Year 1995 2000 2005 2010 Wireless Subscribers Worldwide SOURCE: UMTS FORUM
4G CELLULAR 56-100 GHz 3G CELLULAR 1.5-5.2 GHz 1G, 2G CELLULAR 0.4-1.5GHz Electromagnetic Spectrum HARMFUL RADIATION LIGHT RADIO SOUND VHF = VERY HIGH FREQUENCY UHF = ULTRA HIGH FREQUENCY SHF = SUPER HIGH FREQUENCY EHF = EXTRA HIGH FREQUENCY SOURCE: JSC.MIL
Wireless Telephony WIRELESS AIR LINK WIRED PUBLIC SWITCHED TELEPHONE NETWORK SOURCE: IEC.ORG
ACTUAL COVERAGE AREA OF CELL 3 ACTUAL COVERAGE AREA OF CELL 1 Cell Clusters CELL 1 OVERLAPS 6 OTHERS DIFFERENT FREQUENCIES MUST BE USED IN ADJACENT CELLS SEVEN DIFFERENT SETS OF FREQUENCIES REQUIRED SOURCE: IEC.ORG
Space Division Multiple Access (SDMA) MANY CELLS CAN SHARE SAME FREQUENCIES IF SEPARATED IN SPACE PATTERN CAN BE REPLICATED OVER THE ENTIRE EARTH 200 FREQUENCIES IN ONE CELL TOTAL NUMBER OFFREQUENCIES = 1400 WORLDWIDE
Cell Handover AS PHONE MOVES FROM CELL “A” TO CELL “B”: • CELL “A” MUST HAND THE CALL OVER TO “B” • PHONE MUST CHANGE FREQUENCIES • CELL “A” MUST STOP TRANSMITTING Minimum performance contour A x y B z Handover threshold contour SOURCE: R. C. LEVINE, SMU
MACROCELL: $1M FAST-MOVINGSUBSCRIBERS PICOCELLS MICROCELL: $250K SLOW-MOVINGSUBSCRIBERS Cell Sizes GSM: 100m - 50 km 250 km/hr
Multiple Access Code Division Time Division Frequency Division SOURCE: WASHINGTON UNIV.
Cellular Generations • First • Analog, circuit-switched (AMPS) • Second • Digital, circuit-switched (GSM, Palm) 10 Kbps • Advanced second • Digital, circuit switched, Internet-enabled (WAP) 10 Kbps • 2.5 • Digital, packet-switched, TDMA (GPRS, EDGE)40-400 Kbps • Third • Digital, packet-switched, wideband CDMA (UMTS)0.4 – 2 Mbps • Fourth • Data rate 100 Mbps; achieves “telepresence”
CELL TRANSMITTER & RECEIVER INTERFACE TO LANDTELEPHONE NETWORKS HIERARCHY OF CELLS STOLEN, BROKEN CELLPHONE LIST LIST OF ROAMINGVISITORS PHONE ENCRYPTION, AUTHENTICATION LIST OF SUBSCRIBERS IN THIS AREA SIM: IDENTIFIES A SUBSCRIBER GSM Architecture DATA RATE: 9.6 Kbps SOURCE: UWC
GSM Frame Structure SOURCE: DANIEL ROLF
WCDMA 8 PSK GMSK GMSK TECHNOLOGY From GSM to UMTS PACKET SWITCHED HSCSD = High Speed Circuit Switched Data GPRS = General Packet Radio System EDGE = Enhanced Data Rates for GSM Evolution UMTS = UniversalMobile TelecommSystem kbit/s 2000 UMTS BUILT ON TOP OF GSM 384 EDGE 170 VoIP GPRS 64 HSCSD 43.2 1999 2000 2001 2002 2003 CIRCUIT SWITCHED SOURCE: HPY
UMTS • Universal Mobile Telecommunications System • Data at 2 megabits (> T1) but only indoors • Outdoors same as EDGE (384 Kbps) • Arthur Andersen says no wireless app needs more than 300 Kbps. WRONG! • Based on WCDMA (wideband CDMA) • Huge spectrum license costs • UK 40B€; German 50B€ • GSM to EDGE costs 7% of GSM investment • GSM to UMTS costs 200-300% of GSM investment SOURCE: WAPLAND
UMTS • ITU open standard: IMT-2000 • Includes satellites • Different countries use different air interfaces • UMTS Subscriber Identity Module (USIM) • operating system software for any UMTS device • graphic files, electronic signature data, personal files, fingerprints and biometric data. SOURCE: WAPLAND
General Packet Radio Service (GPRS) • General Packet Radio Service (GPRS) is a new service designed for digital cellular networks (GSM-Global System for Mobile Communications, DCS, PCS). • It utilises a packet radio principle and can be used for carrying end user’s packet data protocol (such as IP and X.25) information from/to a GPRS terminals to/from other GPRS terminals and/or external packet data networks. • GPRS is standardised in ETSI (European Telecommunications Standards Institute).
General Packet Radio Service (GPRS) • GPRS uses a packet-mode technique to transfer high-speed and low-speed data and signalling in an efficient manner over GSM radio networks. GPRS optimises the use of network resources and radio resources. Strict separation between the radio subsystem and network subsystem is maintained, allowing the network subsystem to be reused with other radio access technologies. GPRS does not mandate changes to an installed MSC base.
General Packet Radio Service (GPRS) • GPRS is designed to support from intermittent and bursty data transfers through to occasional transmission of large volumes of data. Four different quality of service levels are supported. GPRS is designed for fast reservation to begin transmission of packets, typically 0,5 to 1 second. Charging will typically be based on the amount of data transferred.
General Packet Radio Service (GPRS) • GPRS introduces the following two new major network elements: • SGSN—Sends data to and receives data from mobile stations, and maintains information about thelocation of a mobile station (MS). The SGSN communicates between the MS and the GGSN. SGSN • GGSN—A wireless gateway that allows mobile cell phone users to access the public data network • (PDN) or specified private IP networks. The GGSN function is implemented on the Cisco Systems’ router.
General Packet Radio Service (GPRS) • User sessions are connected from a mobile station to a Base Transceiver Station (BTS), to a Base Station Controller (BSC). The combined functions of the BTS and BSC are referred to as the Base Station Subsystem (BSS). From there, the SGSN provides access to the GGSN, which serves as the gateway to the data network.
GEO MEO LEO Satellite Systems GEO (22,300 mi., equatorial) high bandwidth, power, latency MEO high bandwidth, power, latency LEO (400 mi.) low power, latency more satellites small footprint V-SAT (Very Small Aperture) private WAN SOURCE: WASHINGTON UNIV.
GPS Satellite Constellation • Global Positioning System • Operated by USAF • 25 satellites • 6 orbital planes at a height of 20,200 km • Positioned so a minimum of 5 satellites are visible at all times • Receiver measures distance to satellite SOURCE: NAVSTAR
Automatic Vehicle Location (AVL) • Benefits of AVL • Fast dispatch • Customer service • Safety, security • Digital messaging • Dynamic route optimization • Driver complicance • Sample AVL Users • Chicago 911 • Inkombank, Moscow • Taxi companies SOURCE: TRIMBLE NAVIGATION
GPS and Auto Insurance • Need to rate drivers accurately • age, residence and driving record not enough • driving after midnight is 10 TIMES as risky as at 8:00 a.m. • commuting is the safest kind of driving • parking in high-crime neighborhoods increases payout • Progressive Insurance (Mayfield, Ohio) • “Autograph” policy: car is outfitted with GPS, cellular modem, microprocessor + 256KB memory • When ignition is turned on, car records location every six minutes • Once a month, uploaded to Progressive by cellphone
GPS and Auto Insurance • Customer is billed retrospectively every month • 25-50% savings in premiums • Increases Progressive’s share but also gives them the right share (safe drivers)
Location-Aware Applications • Vehicle tracking • Firemen in buildings, vital signs, oxygen remaining • Asset tracking • Baggage • Shoppers assistance • Robots • Corporate visitors
Automatic Identificationand Data Capture (AIDC) • Problem: how to obtain data from physical objects • Examples: product ID, price, serial number • Bar code two-dimensional • Magnetic stripe card • Smart card • Radio Frequency Identification (RFID) • Real-Time Locating Systems (RTLS) TAG RFID CIRCUIT WAND READER
AIDC Applications • Highway toll collection • Freight containers • Animal identification • Theft detection • Inventory, asset management • Traffic control • Gas station billing SOURCE: TSS