Mobile Communications
Transcrição
Mobile Communications
Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme Organization Lecture Dates • Monday, 16:30 – 18:00, AH5 • Wednesday, 13:30 - 15:00, 5052 Mobile Communications Exercise Dates • Wednesday, 13:30 - 15:00, 5052 Material (Slide Copies and Video Recordings) http://www-i4.informatik.rwth-aachen.de/ content/teaching/lectures/sub/mobil/WS0708/index.html Literature Lehrstuhl für Informatik 4 RWTH Aachen • J. Schiller: Mobile Communications. 2nd Edition, Addison Wesley, 2003 • V. Garg: Wireless Communications and Networking. Morgan Kaufmann, 2007 Contact Dr. Dirk Thißen Dirk Thißen Lehrstuhl für Informatik 4, Room 4105B (Building E1) Phone: 0241 / 80 - 21450 E-Mail: [email protected] Prof. Dr. Otto Spaniol Page 1 Chapter 1: Introduction Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme Why Wireless Networks? • Two aspects of mobility: User mobility: a user communicates „anytime, anywhere, using any access technology“ Device portability: A device can connect to the network anytime and anywhere • Characteristics Mostly radio transmission, new protocols for data transmission are needed • Advantages Spatial flexibility in radio reception range Ad hoc networks without former planning No problems with wiring (e.g. historical buildings, fire protection, esthetics) Robust against disasters like earthquake, fire – and careless users which remove connectors! Example stationary computer notebook in a hotel Wireless LAN in buildings Cellular phone • The demand for mobile communication creates the need for integration of wireless networks into existing fixed networks: In the local range: standardization of IEEE 802.11 (Wireless LAN, WLAN) considering existing wired standards like Ethernet In wide area range: e.g. internetworking of GSM and ISDN In the Internet protocols: Mobile IP as enhancement of „normal“ IP Chapter 1: Introduction Page 2 Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme What is Mobile Communications? • Wireless vs. Mobile Chapter 1: Introduction Page 3 • Disadvantages Generally very low transmission rates for higher numbers of users Often proprietary, more powerful approaches, standards are often restricted Consideration of lots of national regulations, global regulations are evolving slowly Restricted frequency range, interferences of frequencies Chapter 1: Introduction Page 4 Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme Types of Wireless Networks Possible Applications Cellular Networks • Base stations distributed over the area to be covered • Each base station covers a cell • Need of an infrastructure network connecting all base stations • Used for mobile phone networks and data networks like Wireless LAN Mobile Ad-Hoc Networks (MANETs) • Self-configuring network of mobile nodes • Each node serves as client and router • No infrastructure (base stations) necessary, direct connections between any pair of nodes • E.g. Bluetooth Mesh Networks • Enhancement of above concepts: “Ad-hoc network with infrastructure” • Allow a whole mesh of connections between wireless nodes • Increased fault tolerance • E.g. used in WiMAX Chapter 1: Introduction Page 5 Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme Chapter 1: Introduction Page 6 Possible Applications ad ho • Traveling salesmen Direct access to customer files stored in a central location Consistent databases for all agents Mobile office c • Replacement of fixed networks Remote sensors, e.g., weather, earth activities Flexibility for trade shows LANs in historic buildings Personal Travel Assistant, DAB, PDA, Laptop, GSM/UMTS, WLAN, Bluetooth, ... Chapter 1: Introduction • Emergencies Early transmission of patient data to the hospital, current status, first diagnosis Replacement of a fixed infrastructure in case of earthquakes, hurricanes, fire etc. Crisis, war, ... Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme „Typical“ Application: Road Traffic UMTS, WLAN, DAB, GSM, ... • Vehicles Transmission of news, road condition, weather, music, e.g. via DAB (Digital Audio Broadcasting) Personal communication using the Global System for Mobile Communication (GSM) Location tracking via the Global Positioning System (GPS) Local ad-hoc networks with vehicles close-by to prevent accidents, guidance system, redundancy Vehicle data (e.g., from busses, high-speed trains) can be transmitted in advance for maintenance Page 7 • Entertainment, education, ... Outdoor Internet access Intelligent travel guide with up-to-date location dependent information Ad-hoc networks for multi user games Chapter 1: Introduction Page 8 Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme Wireless Networks in Comparison to Wired Networks Location Dependent Services • Higher loss-rates due to interference Emissions of e.g. engines, lightning • Location aware services What services, e.g., printer, fax, phone, server etc. exist in the local environment • Restrictive regulations of radio frequencies Frequencies have to be coordinated, useful frequencies are almost all occupied • Follow-on services Automatic call-forwarding, transmission of the actual workspace to the current location • Low transmission rates Local some Mbit/s, regional currently up to 384 Kbit/s with GPRS/UMTS/… • Information services „Push“: e.g., current special offers in the supermarket „Pull“: e.g., where is the Black Forrest Cherry Cake? • Higher delays, higher jitter Connection setup time with GSM in the second range, several hundred milliseconds for other wireless systems • Support services Caches, intermediate results, state information etc. „follow“ the mobile device through the fixed network • Lower security, simpler active attacking Radio interface accessible for everyone (shared medium), base station can be simulated, thus attracting calls from mobile phones • Privacy Who should gain knowledge about the location? Page 9 Chapter 1: Introduction Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme Laptop • fully functional • standard applications Sensors, embedded controllers • Many people in history used light for communication Heliographs, flags („semaphore“), ... 150 BC smoke signals for communication (Polybius, Greece) 1794: optical telegraph, Claude Chappe • Here electromagnetic waves are of special importance: 1831 Faraday demonstrates electromagnetic induction J. Maxwell (1831-79): theory of electromagnetic fields, wave equations (1864) H. Hertz (1857-94): demonstrates with an experiment the wave character of electrical transmission through space (1888, in Karlsruhe, Germany, at the location of today’s University of Karlsruhe) Palmtops • tiny keyboard • simple versions of standard applications Performance Chapter 1: Introduction Page 10 Early „Wireless Communication“ PDA • simple graphical displays • character recognition • simplified WWW Mobile phones • voice, data • simple graphical displays Chapter 1: Introduction Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme Characteristics of Mobile Devices Pager • receive only • tiny displays • simple text messages • Very different device capabilities New concepts necessary in protocol design, e.g. energy efficiency Page 11 Chapter 1: Introduction Page 12 Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme History of Wireless Communication History of Wireless Communication • 1928 - Many TV broadcast trials (across Atlantic, color TV, TV news) • 1896 - Guglielmo Marconi First demonstration of wireless telegraphy (digital!) Long wave transmission, high transmission power necessary (> 200kw) • 1907 - Commercial transatlantic connections Huge base stations (30 100m high antennas) • 1915 - Wireless voice transmission New York - San Francisco • 1920 - Discovery of short waves by Marconi Reflection at the ionosphere Smaller sender and receiver, possible due to the invention of the vacuum tube (1906, Lee DeForest and Robert von Lieben) • 1926 - Train-phone on the line Hamburg - Berlin Wires parallel to the railroad track Chapter 1: Introduction • 1958 - A-Netz in Germany Analogue, 160MHz, connection setup only from the mobile station, no handover, 80% coverage, 1971 11000 customers • 1972 - B-Netz in Germany Analogue, 160MHz, connection setup from the fixed network too (but location of the mobile station has to be known) available also in Austria, Netherlands and Luxembourg, 1979 13000 customers in Germany • 1979 - NMT at 450MHz (Scandinavian countries) • 1982 - Start of GSM-specification Goal: pan-European digital mobile phone system with roaming • 1983 - Start of the American AMPS (Advanced Mobile Phone System, analog) Page 13 Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme • 1984 - CT-1 standard (Europe) for cordless telephones Chapter 1: Introduction Page 14 Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme History of Wireless Communication History of Wireless Communication • 1986 - C-Netz in Germany Analog voice transmission, 450MHz, hand-over possible, digital signaling, automatic location of mobile device Was in use until 2000, services: FAX, modem, X.25, e-mail, 98% coverage • 1991 - Specification of DECT Digital European Cordless Telephone (today: Digital Enhanced Cordless Telecommunications) 1880-1900MHz, ~100-500m range, 120 duplex channels, 1.2Mbit/s data transmission, voice encryption, authentication, up to several 10000 user/km2, used in more than 50 countries • 1992 - Start of GSM In Germany as D1 and D2, fully digital, 900MHz, 124 channels Automatic location, hand-over, cellular Roaming in Europe - now worldwide in more than 170 countries Services: data with 9.6kbit/s, FAX, voice, ... Chapter 1: Introduction • 1933 - Frequency modulation (E. H. Armstrong) • 1994 - E-Netz in Germany GSM with 1800MHz, smaller cells As E-plus in Germany (1997 98% coverage of the population) • 1996 - HiperLAN (High Performance Radio Local Area Network) ETSI, standardization of type 1: 5.15 - 5.30GHz, 23.5Mbit/s Recommendations for type 2 and 3 (both 5GHz) and 4 (17GHz) as wireless ATM-networks (up to 155Mbit/s) • 1997 - Wireless LAN – IEEE 802.11 IEEE standard, 2.4GHz and infrared, 2Mbit/s Already many (proprietary) products available in the beginning • 1998 - Specification of GSM successors UMTS (Universal Mobile Telecommunication System) as European proposals for IMT-2000 Iridium: 66 satellites (+6 spare), 1.6GHz to the mobile phone Page 15 Chapter 1: Introduction Page 16 Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme Wireless Systems: Overview of the Evolution History of Wireless Communication • 1999 - Standardization of additional wireless LANs IEEE standard 802.11b, 2.4-2.5GHz, 11Mbit/s Bluetooth for piconets, 2.4Ghz, <1Mbit/s Decision about IMT-2000 Several “members” of a “family”: UMTS, cdma2000, DECT, … Start of WAP (Wireless Application Protocol) and i-mode Access to many (Internet) services via the mobile phone • 2000 - GSM with higher data rates HSCSD offers up to 57,6kbit/s First GPRS trials with up to 50 kbit/s (packet oriented!) UMTS auctions/beauty contests Hype followed by disillusionment (approx. 50 B$ payed in Germany for 6 UMTS licenses!) • 2001 - Start of 3G systems Cdma2000 in Korea, UMTS in Europe, Foma (almost UMTS) in Japan • since 2002 – Standardization of high-capacity wireless networks 802.16 as WMAN, IEEE 802.20 (WWAN), IEEE 802.22 (WRAN)Page 17 Chapter1:IEEE Introduction Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme • DECT - Digital Enhanced Cordless Telecommunications (Standard for wireless phones in a local range) wired devices WMAN WLAN 0.1 • GSM - Global System for Mobile Communication (cellular phone system) HIPERLAN 1.0 • UMTS - Universal Mobile Telecommunications System (universal system, comprising several different access systems) UMTS CORDLESS (DECT) 0.01 • WLAN - Wireless Local Area Network (Standard for wireless networking of (portable) computer) CELLULAR (GSM) mobility Office Building stationary Indoor 1982: Inmarsat-A 1984: CT1 1986: NMT 900 • 1991: CDMA 1991: D-AMPS 1993: PDC 1994: DCS 1800 • 3rd generation (3G): integration of voice and data • 4th generation (4G): integration with Internet (When 1: and how?) Chapter Introduction 1987: CT1+ 1988: Inmarsat-C generation: digital 1992: GSM wireless LAN 1980: CT0 1981: NMT 450 1983: AMPS 2nd cordless phones 1989: CT 2 1992: Inmarsat-B Inmarsat-M 1991: DECT 1998: Iridium 2000: GPRS analogue 199x: proprietary 1997: IEEE 802.11 1999: 802.11b, Bluetooth 2000: IEEE 802.11a 2001: IMT-2000/UMTS since 2002: IEEE 802.16/20/22 digital 200?: Fourth Generation (Internet based) Page 18 Network Categories: Personal Area Networks (PAN) transmission rate (MBit/s) 10.0 • 1st generation: analogue satellites Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme Wireless Systems 100.0 cellular phones walk Outdoor drive • HIPERLAN – alternative LAN to WLAN, „wireless ATM enhancement“ Personal Area Networks (very small range) • IEEE 802.15 (WPAN, Bluetooth): Data rates up to 2 MBit/s Range up to ca. 10/15 meters (with higher transmission power, also 100 meters are no problem), forming of small radio cells Ad-hoc Networking: spontaneous (automatically) connection of several devices (maximally 8) to an independent network Used with cellular phones, Personal Digital Assistants (PDAs), ... • WMAN – Wireless MAN (Bridging the last mile between a fixed network and the end user, wireless alternative to DSL) • And furthermore: Satellite systems, Bluetooth in very short range Chapter 1: Introduction Page 19 Chapter 1: Introduction Page 20 Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme Network Categories : Wireless “Local” Area Networks Network Categories: Telecommunication Networks Cordless Systems • DECT (Digital Enhanced Cordless Telecommunications) Standard for cordless telephony Transmission of voice and data in short range (at home) Wireless LANs (small range) • IEEE 802.11 (Wireless LAN, WLAN) “The” standard for supporting mobile computers High data rates: currently up to 54 MBit/s Physical layer and MAC: often called “wireless variant of Ethernet” Base stations (Access Point, AP) connect WLAN with fixed Ethernet, additionally WLAN enables forming ad-hoc networks Transmission medium: radio and infrared • IEEE 802.16 (WirelessMAN/WiMAX), 802.20 (WirelessWAN), 802.22 (Wireless Regional Area Network) 802.11 mainly supports mobility, 802.16 more focuses on connecting buildings Higher data rates (32-134 Mb/s), larger range Cellular Systems (medium range) • GSM (Global System for Mobile Communications) Mainly designed for voice transmission, also used for data transmission (Wide Area Network) Low data rates (9,6 Kb/s) Enhancements for data transmission (EDGE, GPRS, HSCSD) • UMTS (Universal Mobile Telecommunications System) Also: IMT-2000 (International Mobile Telecommunications) Integration of “all” types of data, rates up to 2 Mb/s … and for word-wide coverage: satellites. Page 21 Chapter 1: Introduction Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme Page 22 Chapter 1: Introduction Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme Overlay Networks Mobility is not only Wireless Networks • Invalid IP address in foreign network • Routing problems • TCP connections break down → TCP/IP modifications necessary! integration of heterogeneous fixed and mobile networks with varying transmission characteristics 137.226.12.98 regional Vertical Handover (IEEE 802.21) metropolitan area 137.226.12/24 router home network campus Internet 141.17.63/24 Horizontal Handover foreign network router Chapter 1: Introduction indoor Page 23 Chapter 1: Introduction Page 24 Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme Areas of Research in Mobile Communication Simple Reference Model used here • Wireless communication Transmission quality (bandwidth, error rate, delay) Modulation, coding, interference Media access, regulations ... • Mobility Location dependent services Location transparency Quality of Service support (delay, jitter, security) ... Page 25 Network Network Network Data Link Data Link Data Link Data Link Physical Physical Physical Physical Medium Chapter 1: Introduction Page 26 Structure of the Lecture • Service location • Adaptive application • New applications Chapter 2 • Technical Basics: Layer 1 • Methods for Medium Access: Layer 2 • Congestion and flow control • Quality of Service Network Layer • Addressing, routing • Device location • Handover Data Link Layer • Medium access control • Multiplexing • (Authentication) Physical Layer • Frequencies, modulation • Interferences, attenuation • (Encryption) Chapter 1: Introduction Transport Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme Tasks on Protocol Layers Transport Layer Transport Radio Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme Application Layer Application Network • Portability Power consumption Limited computing power, sizes of display, ... Usability ... Chapter 1: Introduction Application Chapter 3 • Wireless Networks: Bluetooth, WLAN, WirelessMAN, and variants • Mobile Networks: GSM, GPRS, UMTS • Satellites and Broadcast Networks Chapter 4 • Mobility on the network layer: Mobile IP, Routing, Ad-Hoc Networks • Mobility on the transport layer: reliable transmission, flow control, QoS • Mobility support on the application layer Page 27 Chapter 1: Introduction Page 28