Bikash Sadhukhan. M.Tech(CSE) Lecturer. Dept of CSE/IT Techno India College of Technology
Mobile Communication Entails transmission of data to and from handheld devices Two or more communicating devices At least one is handheld or mobile Location of the device can vary either locally or globally Communication takes place through a wireless, distributed, or diversified network
Brief history of Wireless communication 1901 Marconi s first demonstration of transatlantic wireless communication using electromagnetic waves 1907 onwards commercial transatlantic communication 1920 discovery of short waves by Marconi 1928 many TV broadcast trials 1950s-1970s --- Some commercial installations of fixed wireless telephony, e.g., A-Netz and Bnertz systems in Germany 1970 ALOHANET: first packet radio network (University of Hawaii) 1979 Nordic Mobile Telephony (NMT) system 1981 start of Global Spéciale Mobile (GSM) specification 1982 start of American Advanced Mobile Phone System (AMPS) specification 1984 CT-1 standard (Europe) for cordless telephones 1991 Digital European Cordless Telephony (DECT)
Brief history of Wireless communication 1992 Start of GSM 1996 High Performance Radio Local Area Network (HiperLAN) 1997 wireless LAN standard IEEE802.11 released 1998 specification of the Universal Mobile Telecommunication System (UMTS) as European proposal for IMT-2000 1999 new wireless LAN standards 802.11b and 802.11a 1999 first specification of Bluetooth 2000 GSM with higher data rates and first GPRS trials 2001 start of third generation (3G) systems 2001 specification of the fixed wireless broadband standard IEEE 802.16 (WiMax) released 2003 Improved version IEEE 802.16a released 2003 IEEE802.11g released 2003 IEEE 802.15.4 standard released (which eventually led to the development of the ZigBee application stack)
Guided Transmission Metal wires and optical fibres guided or wired transmission of data Guided transmission of electrical signals takes place using four types of cables Fibre- and wire- based transmission and their Fibre- and wire- based transmission and their ranges:
Four types of cables for Guided Transmission 1. Optical fibre for pulses of wavelength 1.35 1.5 µm 2. Coaxial cable for electrical signals of frequencies up to 500 MHz and up to a range of about 40 m 3. Twisted wire pairs for conventional (without coding) electrical signals of up to 100 khz and up to a range of 2 km, or for coded signals of frequencies up to 200 MHz and a range of about 100 m 4. Power lines, a relatively recent advent in communication technology used for long-range transmission of frequencies between 10 khz and 525 khz
Guided Transmission Advantages Transmission along a directed path from one point to another Practically no interference in transmission from any external source or path Using multiplexing and coding, a large number of signal-sources simultaneously transmitted along an optical fibre, a coaxial cable, or a twisted-pair cable
Guided Transmission Disadvantages Signal transmitter and receiver fixed (immobile). No mobility of transmission and reception points. Number of transmitter and receiver systems limits the total number of interconnections possible
Unguided Wireless Transmission Electrical signals transmitted by converting them into electromagnetic radiation Radiation transmitted via antennae that radiate electromagnetic signals Various frequency bands within the electromagnetic spectrum Different transmission requirements f = c/λ = (300/ λ)mhz [λ in meter]
Classification of wireless networks
Wireless personal area network (WPAN) Network between devices carried by a person Examples Interconnection between a mobile phone and a headset Interconnection between a laptop and projector equipment Wearable computing: everything from helmets, sunglasses to clothes Technologies InfraRed (IrDA) IEEE 802.15 radio standards
Wireless local area network (WLAN) Network between devices in home and office environment; typically gives access to a fixed infrastructure Examples: Interconnection of stationary and mobile devices such as desktops, laptops, telephones, television, etc. Internet access at public venues such as airports, restaurants, conferences, etc. Technologies IEEE 802.11 radio standards (WiFi) Digital Enhanced Cordless Telephony (DECT)
Wireless metropolitan area network (WMAN)
Wireless Wide area networks (WWAN)
Range vs. data rate
Wireless transmission fundamentals Frequency spectrum Radio propagation Signals and antennas Modulation Channel conditions Effects of mobility Multiple access Medium access control
Frequencies for communication
Frequencies for communication Orderly use of frequency spectra reduces interference International Telecommunications Union (ITU) for worldwide coordination Federal Communications Commission (FCC) in the US European Conference for Posts and Telecommunications (CEPT) and European Telecommunication Standards Institute (ETSI) in Europe License spectrum is allocated for proprietary use, e.g., cellular communication Unlicensed spectrum is available for general use (with restrictions), e.g., 2.4 GHz ISM band
Mobile devices
Effects of device portability
Wireless networks in comparison to fixed networks
Simple reference model used here
Influence of mobile communication to the layer model
Development of mobile communication systems
First and Second Generations (1G & 2G) First generation wireless devices only voice signals Second generation (2G) devices communicate voice as well as data signals have data rates of up to 14.4 kbps The 2.5G and 2.5G+ are enhancements of the second The 2.5G and 2.5G+ are enhancements of the second generation and support data rates up to 100 kbps
Third generation (3G) mobile devices communication Higher data rates than 2G and support voice, data, and multimedia streams Facilitates data rates of 2 Mbps Data rates are higher for short distances and 384 kbps for long distance transmissions Enable transfer of video clips and faster multimedia communication
AMPS AMPS is an analog cellular phone system using FDMA. Invented by Bell Labs and first installed in the United States in 1982. It was also used in England
D-AMPS The second generation of the AMPS systems is D- AMPS and is fully digital. D-AMPS was carefully designed to co-exist with AMPS so that both first- and second-generation mobile phones could operate simultaneously in the same cell.
GSM - Global System for Mobile Communication GSM offers several types of connections voice connections, data connections, short message service multi-service options (combination of basic services) Three service domains: Bearer Services: Telecommunication services to transfer data between access points data service (circuit switched) synchronous: 2.4, 4.8 or 9.6 kbit/s asynchronous: 300-1200 bit/s data service (packet switched) synchronous: 2.4, 4.8 or 9.6 kbit/s asynchronous: 300-9600 bit/s
GSM service domains Telematic Service Telecommunication services that enable voice communication via mobile phones Offered services Mobile telephony: Primary goal of GSM was to enable mobile telephony offering the traditional bandwidth of 3.1 khz Emergency number: Common number throughout Europe (112); mandatory for all service providers; free of charge; connection with the highest priority (preemption of other connections possible) Voice mailbox (implemented in the fixed network supporting the mobile terminals) Electronic mail (MHS - Message Handling System, implemented in the fixed network) Short Message Service (SMS)
GSM service domains Supplementary Services Services in addition to the basic services, cannot be offered stand-alone Similar to ISDN services besides lower bandwidth due to the radio link May differ between different service providers, countries and protocol versions Important services identification: forwarding of caller number suppression of number forwarding automatic call-back conferencing with up to 7 participants locking of the mobile terminal (incoming or outgoing calls)
Performance characteristics of GSM Communication - mobile, wireless communication; support for voice and data services Total mobility - international access, chip-card enables use of access points of different providers Worldwide connectivity - one number, the network handles localization High capacity - better frequency efficiency, smaller cells, more customers per cell High transmission quality - high audio quality and reliability for wireless, uninterrupted phone calls at higher speeds (e.g., from cars, trains) Security functions - access control, authentication via chip-card and PIN
GPRS -General Packet Radio Service A packet-oriented service for mobile stations data transmission and their access to the Internet A speed enhanced data transmission service designed for GSM systems Speed enhanced data transmission by packetizing data and simultaneous transmission of packets over different channels Uses the unused slots and channels in TDMA mode of a GSM network for packetized transmission from a mobile station Data-packets of a single mobile station transmit through a number of time slots Advantage: one step towards UMTS, more flexible Disadvantage: more investment needed (new hardware)
EDGE (Enhanced Data rates for GSM Evolution) EDGE is a more advanced upgrade tod the GSM standard and requires the addition of new hardware and software at existing base stations. 8 PSK communication to achieve higher rates of up to 48 kbps per 200 khz channel High date rates compares to up to 14.4 kbps in GSM. Using coding techniques the rate can be enhanced to 384 kbps for the same 200 khz channel
CDMA (Code Division Multiple Access) CDMA supports high data rates Initial evolution of CDMA was 2.5 G. But Nowadays CDMA supports high data rates and considered as 3G. Voice as well as data and multimedia streams. CDMA more robust for multi-path delays and provides higher immunity towards frequency selective fading Each mobile station s or base transceiver s signals are coded with two or three codes Signals of higher voice and data quality and small bit-error rates Soft handover- Soft handover means that an MS at the boundary of two adjacent cells does not have to drop calls due to signal break during handover at the boundary region CDMA systems provide seamless connectivity to the MS CDMA systems perform power control by open loop or close loop methods to solve the problem of drowning of signals from far mobile terminals by those from the near terminals CDMA systems employ spread spectrum techniques (DSSS and FHSS) for medium access control thus problems in narrow band transmission not present
UMTS (Universal mobile telecommunication system) Communicates at data rates of 100 kbps to 2 Mbps It combines CDMA for bandwidth efficiency and GSM for compatibility. It support several technologies for transmission and gives a framework for security and management functions.
Comparison of GSM and CDMA
Mobile computing A Definition The process of computation on a mobile device In mobile computing, a set of distributed computing systems or service provider servers participate, connect, and synchronize through mobile communication protocols Mobile computing as a generic term describing ability to use the technology to wirelessly connect to and use centrally located information and/or application software through the application of small, portable, and wireless computing and communication devices
Mobile computing Provides decentralized (distributed) computations on diversified devices, systems, and networks, which are mobile, synchronized, and interconnected via mobile communication standards and protocols. Mobile device does not restrict itself to just one application, such as, voice communication Offers mobility with computing power Facilitates a large number of applications on a single device
Limitations to mobile computing Resource constraints: Battery Interference: the quality of service (QoS) Bandwidth: connection latency Dynamic changes in communication environment: variations in signal power within a region, thus link delays and connection losses Network Issues: discovery of the connection-service to destination and connection stability Interoperability issues: the varying protocol standards Security constraints: Protocols conserving privacy of communication