Mobile Communications I Chapter 1: Introduction and History

Transcription

1 Mobile Communications I Chapter 1: Introduction and History

2 Mobile communication Two aspects of mobility: user mobility: users communicate (wireless) anytime, anywhere, with anyone device mobility (portability): devices can be connected anytime, anywhere to a network User Device Eample No No Stationary Computer No Yes Notebook at fixed network e.g. in a hotel Yes No Terminals in a historic building Yes Yes Mobile Device (I-Pad, Smartphone) The demand for mobile communication creates the need for integration of wireless networks into existing fixed networks: local area networks: standardization of IEEE , IEEE Internet: Mobile IP extension of the Internet and transport-protocol IP and TCP wide area networks: e.g., internetworking of GSM, UMTS, HSPA and ISDN Chapter 1 Page 54

3 Vehicles (car-2-x) Applications I transmission of news, road condition, weather, music via DAB More and more also car-2-car in safety critical situations personal communication using GSM, UMTS position via GPS local ad-hoc network with vehicles close-by to prevent accidents, guidance system, redundancy (IEEE802.11p) vehicle data (e.g., from busses, high-speed trains) can be transmitted in advance for maintenance (HSDPA, HSUPA) Emergencies early transmission of patient data to the hospital, current status, first diagnosis (TETRA) LTE will be the radio-standard for these applications in future replacement of a fixed infrastructure in case of earthquakes, hurricanes, fire etc.(ieee802.11s, Cognitive Networks) crisis, war,... Chapter 1 Page 55

4 Typical application: road traffic Chapter 1 Page 56

5 Applications II Travelling salesmen (LTE, HSDPA, EDGE, GPRS, WLAN with VPN, GSM, UMTS) direct access to customer data e.g. contracts, stored in a central location consistent databases for all agents mobile office Replacement of fixed networks remote sensors, e.g., weather, earth activities(ieee , IEEE a) flexibility for trade shows (IEEE802.11n) LANs in historic buildings (all WLAN standards) Entertainment, education,... outdoor Internet access (HSDPA, LTE) intelligent travel guide with up-to-date (location dependent) information ad-hoc networks for multi user games (IEEE802.11s, Bluetooth) Chapter 1 Page 57

6 Location (context) dependent services Location aware services what services, e.g., printer, fax, phone, server etc. exist in the local environment Follow-on services automatic call-forwarding, transmission of the actual workspace to the current location Information services push : e.g., current special offers in the supermarket pull : e.g., where do I get the best Black Forrest Cherry Cake? Support services Caches, intermediate results, state information etc. follow the mobile device through the fixed network What s about Privacy and Security who should gain knowledge about the location Chapter 1 Page 58

7 Mobile devices Chapter 1 Page 59

8 Effects of device portability Power consumption limited computing power, SSD (Solid State Disk) due to limited battery capacity CPU: power consumption ~ CV 2 f C: internal capacity of a technology mode, reduced by higher integration V: supply voltage, can be reduced to a certain limit f: clock frequency, can be reduced temporally (due to the use of extremely high scaled technology C has a mayor influence on the total power consumption) Loss of data (reliability) higher probability, has to be included in advance into the design (e.g., defects, theft) Using data storage more and more as cloud storage limits this problem Limited user interfaces compromise between size of fingers and portability integration of character/voice recognition, abstract symbols Limited memory 128GB FLASH in tablets is currently possible alternatively other new types of non volatile storage Chapter 1 Page 60

9 Wireless networks in comparison to fixed networks Higher loss-rates due to interference and other mechanisms in wireless transmission emissions of, e.g., engines, lightning (only in lower frequency range up to 200 MHz) mainly interference with other users in the higher frequency range As a rule of thumb: BER (wired) ; BER (wireless) Restrictive regulations of frequencies frequencies have to be coordinated, useful frequencies are almost all (statically) occupied New approaches for cognitive radio is in research and development (overlay/ underlay approaches) Low transmission rates local >>100 Mbit/s, cellular currently up to 30 (HSPA+) In the new generation of cellular networks the speed difference between Local and regional will not play any more any role. E.G. LTE will support up to 100 Mb/s Higher delays, higher jitter connection setup time with GSM in the second range, several hundred milliseconds for other wireless systems Jitter and delay may impact the QoS (quality of service) but with LTE low latency services that will be as good as in wired networks Lower security, simpler active attacking radio interface accessible for everyone, base station can be simulated, Security is an important issue of research in wireless systems Always shared medium The capacity of a network is divided between the participants. This is a growing concern for the further development of wireless systems. Chapter 1 Page 61

10 Early history of wireless communication Many people in history used light for communication heliographs, flags ( semaphore ), 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 ( ): theory of electromagnetic fields, wave equations (1864) H. Hertz ( ): demonstrates with an experiment the wave character of electrical transmission through space Chapter 1 Page 62

11 History of wireless communication I 1896 Guglielmo Marconi first demonstration of wireless telegraphy (digital!, UWB pulstransmission) long wave transmission, high transmission power necessary (> 200 kw) 1907 Commercial transatlantic connections huge base stations (30*100 m high antennas) 1915 Wireless voice transmission New York - San Francisco 1920 Discovery of short waves by Marconi reflection at the ionosphere smaller transmitter 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 Page 63

12 History of wireless communication II 1928 many TV broadcast trials (across Atlantic, color TV, TV news) 1933 Frequency modulation (E. H. Armstrong) 1958 A-Netz in Germany analog, 160 MHz, connection setup only from the mobile station, no handover, 80 % coverage, customers 1972 B-Netz in Germany analog, 160 MHz, connection setup from the fixed network too (but location of the mobile station has to be known) available also in A, NL and LUX, customer in D 1979 NMT at 450 MHz (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) 1984 CT-1 standard (Europe) for cordless telephones Chapter 1 Page 64

13 History of wireless communication III 1986 C-Netz in Germany analog voice transmission, 450 MHz, hand-over possible, digital signaling, automatic location of mobile device was in use until 2000, services: FAX, modem, X.25, , 98 % coverage 1988 first discussion of UMTS networks as a solution of a worldwide wireless communication system (later known as IMT-2000 ) 1991 Specification of DECT Digital European Cordless Telephone (today: Digital Enhanced Cordless Telecommunications) MHz, ~ m range, 120 duplex channels, 1.2 Mbit/s data transmission, voice encryption, authentication, up to several user/km 2, used in more than 50 countries 1992 Start of GSM commercial operation in D as D1 and D2, fully digital, 900 MHz, 124 channels automatic location, hand-over, cellular roaming in Europe - now worldwide in more than 200 countries services: data with 9.6 kbit/s, FAX, voice,... Chapter 1 Page 65

14 History of wireless communication IV 1994 E-Netz in Germany GSM with 1800 MHz, smaller cells As Eplus in D ( % coverage of the population) 1996 HiperLAN (High Performance Radio Local Area Network) ETSI, standardization of type 1: GHz, 23.5 Mbit/s recommendations for type 2 and 3 (both 5 GHz) and 4 (17 GHz) as wireless ATM-networks (up to 155 Mbit/s) 1997 Wireless LAN - IEEE IEEE standard, GHz and infrared, 2 Mbit/s already many (proprietary) products available in the beginning 1998 Specification of GSM successors for UMTS (Universal Mobile Telecommunication System) as European proposals for IMT Iridium 66 satellites (+6 spare), 1.6 GHz to the mobile phone Chapter 1 Page 66

15 History of wireless communication V 1999 Standardization of additional wireless LANs IEEE standard b, GHz, 11 Mbit/s Bluetooth for piconets, 2.4 Ghz, < 1 Mbit/s Decision about IMT-2000 Several members of a family : UMTS, cdma2000, DECT, Start of WAP (Wireless Application Protocol) and i-mode First step towards a unified Internet/mobile communication system Access to many services via the mobile phone 2000 GSM with higher data rates HSCSD offers up to 57.6 kbit/s First GPRS trials with up to 50 kbit/s (packet oriented!) UMTS auctions/beauty contests Hype followed by disillusionment (100 B DM payed in Germany for 6 licenses!) 2001 Start of 3G systems CDMA 2000 in Korea, UMTS tests in Europe, Foma (almost UMTS) in Japan 2010 Roll out of first LTE systems in Germany Chapter 1 Page 67

16 Wireless systems: Overview of the development 1981: NMT : NMT 900 cellular phones 1992: GSM 1994: DCS : CDMA 1983: AMPS 1991: D-AMPS 1993: PDC 1982: Inmarsat-A 1988: Inmarsat-C satellites 1992: Inmarsat-B Inmarsat-M 1998: Iridium cordless phones 1980: CT0 1984: CT1 1987: CT : CT 2 wireless LAN 1991: DECT 199x: proprietary 1997: IEEE : b, Bluetooth analogue digital 2000: GPRS 2001: IMT G fourth generation: when and how? 200?: Fourth Generation (Internet based) 2000: IEEE a Chapter 1 Page 68

17 Mobile phone subscribers worldwide reached 5.3 billion (2011) Chapter 1 Page 69

18 Development of mobile telecommunication systems CDMA TDMA FDMA CT0/1 AMPS NMT CT2 IS-136 TDMA D-AMPS GSM PDC IS-95 cdmaone GPRS cdma2000 1X EDGE IMT-FT DECT IMT-SC IS-136HS UWC-136 1G 2G 2.5G 3G IMT-DS UTRA FDD / W-CDMA IMT-TC UTRA TDD / TD-CDMA IMT-TC TD-SCDMA IMT-MC cdma2000 1X EV-DO 1X EV-DV (3X) Chapter 1 Page 70

19 Wireless Communication Areas of research in mobile communication capacity and bandwidth efficiency due to shortage in available spectrum transmission quality (bandwidth, error rate, delay) modulation, coding, interference media access, regulations security and reliability Cognitive Radio based on SDR (software defined radio) systems Mobility location dependent services location transparency quality of service support (delay, jitter, security)... Portability power consumption limited computing power, sizes of display,... usability Chapter 1 Page 71

20 Development of Mobile Access Speed Source: VTC-2007, Fettweis Chapter 1 Page 72

21 Simple reference model used here Application Application Transport Transport Network Network Network Network Data Link Data Link Data Link Data Link Physical Physical Physical Physical Radio Medium Chapter 1 Page 73

22 Influence of mobile communication to the layer model Application layer Transport layer Network layer Data link layer Physical layer service location new applications, multimedia adaptive applications congestion and flow control quality of service addressing, routing, device location hand-over authentication media access multiplexing media access control encryption modulation interference attenuation frequency Chapter 1 Page 74

23 Overlay Networks - the global goal Chapter 1 Page 75

24 Mobile Communications I Chapter 2: Physical Layer Issues

25 Frequencies for communication twisted pair coax cable optical transmission 1 Mm 300 Hz 10 km 30 khz 100 m 3 MHz 1 m 300 MHz 10 mm 30 GHz 100 m 3 THz 1 m 300 THz VLF LF MF HF VHF UHF SHF EHF infrared visible light UV VLF = Very Low Frequency UHF = Ultra High Frequency LF = Low Frequency SHF = Super High Frequency MF = Medium Frequency EHF = Extra High Frequency HF = High Frequency UV = Ultraviolet Light VHF = Very High Frequency D:\Kraemer Rolf\Documents\Vorlesungen\Vorlesung MK1-2012\freqchrt.pdf Frequency and wave length: = c/f wave length, speed of light c 3 x 10 8 m/s, frequency f Chapter 2 Page 77

26 Frequencies for mobile communication VHF-/UHF-ranges for mobile radio simple, small antennas deterministic propagation characteristics, reliable connections SHF and higher for directed radio links, satellite communication small antenna, focusing large bandwidth available Wireless LANs use frequencies in UHF to SHF spectrum some systems planned up to EHF E.g. IHP working on systems for 100 Gb/s at 250 GHz limitations due to absorption by water-, oxygen- and other gasmolecules (resonance frequencies) (Application Resonance Spectroscopy weather dependent fading, signal loss caused by heavy rainfall etc. WLAN uses unlicensed spectrum in ISM-bands (Industrial, Scientific, Medical) in the 2.4 GHz and 5.2 to 5.8 GHz range) Chapter 2 Page 78

27 Frequencies and regulations ITU-R holds auctions for new frequencies, manages frequency bands worldwide (WRC, World Radio Conferences) Europe USA Japan Cellular Phones Cordless Phones Wireless LANs Others GSM , / , , / , / UMTS (FDD) , UMTS (TDD) , CT , CT DECT IEEE HIPERLAN , RF-Control 27, 128, 418, 433, 868 AMPS, TDMA, CDMA , TDMA, CDMA, GSM , PACS , PACS-UB IEEE , RF-Control 315, 915 PDC , , , PHS JCT IEEE RF-Control 426, 868 Chapter 2 Page 79

28 Signals I physical representation of data function of time and location signal parameters: parameters representing the value of data (e.g. 0-1 values can be represented by different frequencies, different amplitudes, different phases etc. classification continuous time/discrete time continuous values/discrete values analog signal = continuous time and continuous values digital signal = discrete time and/or discrete values (digital values are not restricted to binary values) today also combinations are being used e.g. discrete values and continuous time signal parameters of periodic signals: period T, frequency f = 1/T, amplitude A, phase shift sine wave as special periodic signal for a carrier: s(t) = A t sin(2 f t t + t ) Chapter 2 Page 80

29 Fourier representation of periodic signals g( t) 1 2 c n 1 a n sin(2 nft ) n 1 b n cos(2 nft ) ideal periodic signal real composition (based on harmonics) Chapter 2 Page 81

30 Signals II Different representations of signals amplitude (amplitude domain) frequency spectrum (frequency domain) phase state diagram (amplitude M and phase in polar coordinates) A [V] A [V] Q = M sin t[s] Composed signals transferred into frequency domain using Fourier transformation Digital signals need infinite frequencies for perfect transmission f [Hz] modulation to a carrier frequency for transmission (analog signal!) I= M cos Chapter 2 Page 82

31 Antennas: isotropic radiator Radiation and reception of electromagnetic waves, coupling of wires to space for radio transmission Antennas are resonant structure thus they are limited to certain frequency ranges Isotropic radiator: equal radiation in all directions (three dimensional) - only a theoretical reference antenna Real antennas always have directive effects (vertically and/or horizontally) Radiation pattern: measurement of radiation around an antenna Is used as reference for measuring of antennas (EIRP= Equivalent Isotropic Radiated Power) y z z x y x ideal isotropic radiator Chapter 2 Page 83

32 Antennas: simple dipoles Real antennas are not isotropic radiators but, e.g., dipoles with lengths /4 on car roofs or /2 as Hertzian dipole shape of antenna proportional to wavelength Metallic Surface /4 /2 Example: Radiation pattern of a simple Hertzian dipole y y z x z x simple dipole side view (xy-plane) Gain: maximum power in the direction of the main lobe compared to the power of an isotropic radiator (with the same average power) Gain measure in dbi ( 10*log 10 P max /P i ) (there might be other reference Antennas like e.g. dipole etc.) side view (yz-plane) Chapter 2 Page 84 top view (xz-plane)

33 Antennas: directed and sectorized Often used for microwave connections or base stations for mobile phones (e.g., radio coverage of a valley) y x y z z x directed antenna side view (xy-plane) side view (yz-plane) top view (xz-plane) z z x x sectorized antenna top view, 3 sector top view, 6 sector Chapter 2 Page 85

34 Antennas: diversity Grouping of 2 or more antennas multi-element antenna arrays Antenna diversity and passive Active (e.g. MIMO) switched diversity, selection diversity receiver chooses antenna with largest output diversity combining combine output power to produce gain co-phasing needed to avoid cancellation /4 /2 /4 /2 /2 /2 + + ground plane Chapter 2 Page 86

35 MIMO: Modes Chapter 2 Page 87

36 Antenna Animations D:\Kraemer Rolf\Documents\Vorlesungen\Vorlesung MK1-2012\LPDA_xy.avi D:\Kraemer Rolf\Documents\Vorlesungen\Vorlesung MK1-2012\monocone_finite_gp.avi D:\Kraemer Rolf\Documents\Vorlesungen\Vorlesung MK1-2012\VIVALDI_xy.avi D:\Kraemer Rolf\Documents\Vorlesungen\Vorlesung MK1-2012\movie_kurz.avi Chapter 2 Page 88