Wireless Communications Part 2 April 10 2000 Mobile

Wireless Communications Part 2 April 10, 2000

Mobile Radio Systems u mobile originally meant any radio terminal that can be moved during operation u now, portable describes a radio terminal that can be hand-held and used by someone at walking speed (like a portable telephone) u mobile is reserved for a radio terminal attached to a fast-moving vehicle like a car (the familiar cell phone)

Global Mobile Radio Systems u u u CT 2 and DECT (Digital European Cordless Telephone) are the two most popular cordless phone standards used in Europe and Asia NTT in Japan implemented the world’s first cellular system in 1979 in 1981, the Nordic Mobile Telephone system (NMT 450) Extended European Total Access Cellular System (ETACS) was deployed in 1985 and is very similar to AMPS in the US GSM (Global System for Mobile) was first deployed in 1991 in a 900 Mhz band designated for all of Europe

Mobile Radio Systems u systems can be simplex, one direction only like paging u half-duplex, which allow two-way communication, but one direction at a time because only one channel is provided for transmission and reception u full-duplex provide two simultaneous, separate channels (frequency division duplex) or adjacent time slots on a single channel (time division duplex) for communication to and from the user

Mobile Radio Systems: Dividing Spectrum u frequency – each user is allocated a band of the available frequency u time – division multiplexing each user is allocated a slice of time called a carrier

Mobile Radio Systems: Dividing Spectrum u code – – division multiplexing based on direct sequence spread spectrum break up a data signal up using a unique pattern for that user and spread their signal

Cellular Telephone Systems u carry voice messages via radio frequency channels rather than traditional telephone lines u frequency reuse – by assigning the same frequency in two different cells, the frequency can be reused as long as the cells are sufficiently far apart u low power transmitters and small coverage zones

Cellular Telephone Systems u each service area is divided into hexagonally shaped cells u each cell site has a receiver antenna which picks up signals and then transmits them to a computerized mobile telephone switching office (MTSO) u a base station at each cell site receives, transmits, and switches calls to and from any mobile unit in the cell to the MTSO ((hand-off and central control)

Cellular Telephone Systems u the MTSO tracks a mobile phone as it moves from cell to cell and takes the signal from the appropriate cell, keeps track of time and billing for each mobile unit u the mobile switching office relays a continual signal from the cell phone to the phone system

Mobile Telephony and Cellular Systems u cellular radio telephone u first mobile telephone service introduced in the US in 1946 u by 1976, the Bell Mobile Phone Service could accommodate 543 customers in a market of 10 million people in New York u major obstacles were amount of frequency needed for one call, inefficient use of spectrum u concept of breaking a coverage zone into small cells, each reusing portions of the spectrum to increase spectrum usage was implemented in the late 1970 s

Mobile Telephony and Cellular Systems u first US mobile telephony system AMPS (Advanced Mobile Phone System) was deployed in 1983 by Ameritech in Chicago u in 1991, USDC (US Digital Cellular) system hardware was installed u AMPS has been phased out as users accept digital phones

Technologies u analog FM and frequency division multiple access (FDMA) is being replaced by digital modulation and time division multiple access (TDMA) u a cellular service based on CDMA (code division multiple access) has been developed by Qual. Comm and standardized by TIA (Telecommunications Industry Association)

Mobile Telephony and Cellular Systems u first – – generation - early 1990’s based on analog communication using frequency modulation and frequency division multiple access (FDMA) AMPS was common in North and South America, Australia and China u second generation technology – developed to use the frequency spectrum more efficiently – digital techniques time division multiplexing (TDM) or code division multiple access (CDMA) advanced call processing features like voice mail and call forwarding GSM – – –

Mobile Telephony and Cellular Systems u Third generation - cellular, wireless, and PCS – – – use CDMA and TDMA and spread spectrum and narrowband digital FDMA integrate services into one standard a single handset will support voice, data, and video

Mobile Telephony and Cellular Systems u GSM – – – first implemented in Europe in 1991 to address the problem of many incompatible systems similar systems now exist in South America, Asia, North Africa, the Middle East, and Australia over 256 operators in 110 countries one of its most attractive features is the use of a Subscriber Identification Module (SIM), a portable smart card or plug-in module that identifies the subscriber, rather than the unit employs data encryption user data rates of up to 9. 6 kbps are supported

Mobile Telephony and Cellular Systems u GSM – move into mobile data communications in Europe – plans to develop high speed circuit switched methods to multiplex channels to support largescale file transfers, fax, mobile video communications – http: //www. gsmworld. com

CDMA and GSM u CDMA has greater capacity than AMPS or GSM u enhanced privacy – technology was originally developed by the military to scramble signals u supports bandwidth on demand u improved coverage characteristics, so fewer cells are needed u http: //www. cdg. org

Wireless Subscribers u Ericson’s market share and penetration by country u http: //www. ericson. com/BR/reflist

Personal Communication Systems (PCS) u devices range from pagers to personal digital assistants (PDAs) which integrate fax, phone, and information services u predict that half of all Americans will be using PCSs by 2003 u England Germany have systems which were available in 1993 and 1994 u still searching for the “killer ap” u users want sufficient bandwidth, access regardless of location, easy, transparent access using a single device

Wide Area Data Transmission on a PCS Network u voice and data transmission via cellular or satellite phone networks u mobile computers include laptops, notebook, notepad, pen-based computers, special preprogrammed data collection device u error detection and flow control methodologies are proprietary – – little interoperability lack of third-party vendors

Global Wireless Teleworkers u u fully mobile groups like sales staff – GTE (USA) sells telecom services and products service engineers – IBM (UK, Phillipines, USA) for computer maintenance – Honeywell Bull (Australia) for computer maintenance emergency services – Derbyshire Ambulance (UK), Swedish Police parcel delivery – Federal Express (Germany, UK, USA) – market researchers

Global Wireless Teleworkers • Real estate – ERA Realty (Singapore) u Banking – Co-op Bank (UK), Banco de Brazil u doctors u marketing staff u telecommuters u contractors, architects, tradesmen