Mobile Comm Ch1
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Transcript of Mobile Comm Ch1
Mobile Communication System Introduction Cellular concept Large scale and small scale fading Analog cellular mobile system Digital cellular mobile system Low power wireless communication system CDMA digital cellular standard Mobile terminals Global mobile satellite system 3G systems
Books
Wireless Communications Theodore S Rappaport
Mobile and Personal Communication Systems and Services Raj Pandya
Mobile Communication Engineering William CY Lee
Termwork Evaluation
Attendance 05 marks Internal Tests 10 marks Journal 10 marks
8 Tutorials 2 Assignments Objective test
Introduction
Underlying vision for mobile and PCS is to enable communication with a person At any time At any place (Reachability)
Home, office, in public, in transit In any form (Accessibility)
Cellular phone, office wired phone, Fax, PDA
“Mobile” : Any radio terminal that could be moved during operation
Now Any radio terminal that is attached to a high speed
mobile platform Cellular telephones
“portable” : Any radio terminal that can be handheld and used by someone at walking speed
Cordless phones Walkie-talkies
Limitations of conventional mobile systems
Limited service capability Used a single high powered transmitter with an antenna
mounted on a tall tower that lead to Large coverage area Limited assigned channels Frequency reuse was not possible
Limited number of active users at any given time
Poor service performance Limited number of channels
Limited number of active users at a time High blocking probability during busy hours
Inefficient frequency spectrum utilization Frequency utilization measurement
Measures maximum no. of customers that can be served by one channel at busy hour
As number of customers increase Mo increases Blocking probability increases
channelsofNumber
customersofNumberM o __
__
Mobile and PCS represent evolution and enhancements in many directions like
Increased capacity and coverage Global roaming and service delivery Interoperability between different radio environments Support of high bit rate data, internet and multimedia services Wireless-wireline integration for mobile broadband services Global coverage using satellite constellations
Rapid worldwide growth has demonstrated that wireless communication is a robust, viable voice and data transport technology
Since the initial commercial introduction of Advanced
Mobile Phone System (AMPS), mobile radio communication has seen explosive growth fueled by
Digital and RF circuit fabrication improvements New large scale circuit integration Miniaturization technologies which makes portable radio
equipment smaller, cheaper and more reliable Digital switching techniques facilitating large scale deployment of
affordable, easy-to-use radio communication networks Frequency reuse capabilities Advances in digital signal processing techniques and integrated
circuit technology
Systems have evolved to address a range of applications and markets which includes Digital cellular mobile Cordless telephony Satellite mobile systems Paging systems Walkie-talkies WLAN Bluetooth UWB systems
Classified as Simplex
Paging systems Half-duplex
Walkie-talkies Duplex
Uses FDD/TDD Cordless telephony Cellular telephony
Evolution
Standard Type Year MA Freq band Mod Ch BW
AMPS Cellular 1983 FDMA 824-894 MHz FM 30 kHz
NAMPS Cellular 1992 FDMA 824-894 MHz FM 10 kHz
USDC Cellular 1991 TDMA 824-894 MHz /4-DQPSK 30 kHz
IS-95 Cellular/ PCS
1993 CDMA (DSSS)
824-894 MHz QPSK/ BPSK
1.25 MHz
POCSAG Paging 1970’s Simplex Several FSK 12.5 kHz
PACS Cordless/ PCS
1994 TDMA/ FDMA
1.85-1.99GHz /4-DQPSK 300 kHz
Major Mobile Radio Standards in North America
Standard Type Year MA Freq band Mod Ch BW
NTT Cellular 1979 FDMA 400/800 MHz FM 25 kHz
JTACS Cellular 1988 FDMA 860-925 MHz FM 25 kHz
PDC Cellular 1993 TDMA 810-1501 MHz
/4-DQPSK 25 kHz
NTACS Cellular 1993 FDMA 843-925 MHz FM 12.5 kHz
PHS Cordless 1993 TDMA 1895-1907 MHz
/4-DQPSK 300 MHz
NTT Paging 1979 FDMA 280 MHz FSK 12.5 kHz
Major Mobile Radio Standards in Japan
Standard Type Year MA Freq band
Mod Ch BW
ETACS Cellular 1985 FDMA 900 MHz FM 25 kHz
GSM Cellular/ PCS
1990 TDMA 890-960 MHz
GMSK 200 kHz
CT2 Cordless 1989 FDMA 864-868 MHz
GFSK 100 kHz
DECT Cordless 1993 TDMA 1.88-1.9GHz
GFSK 1.728 MHz
Major Mobile Radio Standards in Europe
GMPCS These are developed to complement cellular and
personal communication networks whose radio coverage is confined to populated areas
GMPCS systems like Iridium Globalstar Teledesic
operate as overlay networks for existing cellular and PCS networks
Mobile generations First generation
Analog cellular mobile system FDMA/FM/FDD
Second generationprovides atleast 3 times increase in spectrum efficiency Digital cellular mobile system
TDMA/FDD CDMA/FDD
Low power wireless and PCS Rely on sophisticated DSP in handset and BS
Popular second generation standards Three TDMA standards
GSM (Europe, Asia, Australia) IS-136 or NADC (North America) PDC (Japan)
One CDMA standard IS-95 or cdmaOne
These systems were developed to meet business and regulatory requirements in specific countries and/or regions leading to incompatible systems that are unable to provide global mobility
2G networks only support single user data rates (10 kbps) which is too slow for rapid email and internet browsing applications
Evolution toward high data rate packet mode capabilities was a key requirement
Hence new data centric standards have been developed that can be overlaid upon existing 2G technologies
These represent 2.5G technology and allow existing 2G equipment to be modified and supplemented with new base station add-ons and subscriber unit software upgrades
Upgradation to 2.5G 3 upgrade paths for GSM
High speed circuit switched data (HSCSD)
General packet radio service (GPRS)
Enhanced data rate for GSM evolution (EDGE)
Two of them also support IS-136 GPRS EDGE
1 upgrade path available for IS-95 IS-95B
3-G Technology Aim
Consolidation of different wireless environments like cellular mobile, cordless telephony, satellite mobile services under a single standard
Ensuring global mobility in terms of global seamless roaming and delivery of services
Action ITU formulated a plan (IMT-2000) to implement a global
frequency band in 2000 MHz range 3G evolution for CDMA leads to cdma2000 Eventual 3G evolution for GSM, IS-136 and PDC leads to
W-CDMA or UMTS (under ETSI) which is based on network fundamentals of GSM as well as merged vision of GSM and IS-136 through EDGE
Paging systems Message sent to a paging
subscriber via a paging system access number (toll free no.) with a telephone keypad or a modem
Issued message is called a page
Paging system then transmits page throughout service area using BS which broadcasts page on a radio carrier
Classification based on their complexity and coverage area Simple paging system : 2-5km Wide area paging system
Consists of a network of telephone lines, BS transmitters and large radio towers that simultaneously broadcast (simulcasting)
Paging receivers are simple and inexpensive Application : to provide reliable communication
to subscribers wherever they are. Hence Requires large transmitter powers (kW) and low data
rates for max coverage from each BS
Cordless Telephone Systems Uses radio to connect a
portable handset to a dedicated BS which is then connected to a dedicated telephone line with a specific telephone number on PSTN
Provides users with limited range and mobility
Cellular Telephone Systems Provides wireless connection to PSTN for any
user located within the radio range of system Accomodates large number of users over a large
geographical area within a limited frequency spectrum
High capacity achieved by limiting coverage of each BS transmitter to a small geographical area called cell so that frequency reuse can be done
Sophisticated switching technique called handoff enables call to proceed uninterrupted when user moves from one cell to another
Smaller the cell size More efficient spectrum
utilization (higher frequency reuse)
More system capacity Operational unit
comprises of MSC/ MTSO Base station Mobile station
MTSO Acts as central switching office for calls to and from
PSTN Coordinates activities of all BS and connects entire
cellular system to PSTN Major functions
Call switching, routing and overall control Interface with PSTN Coordination and system management Subscriber registration and billing Control of subscriber location and hand-off Provision of services (Call redirection, Call barring)
Base Station Transmits to and receives from all mobile phones within the area
of cell Interface between MTSO and mobile unit,ie connects
simultaneous mobile calls via telephone lines or microwave links to MSC
Consists of Control unit Radio channels Several transmitting and receiving antennas on tower
Mobile unit Consists of control unit, transceiver and antenna system May be mounted on a vehicle or used as a portable hand-held unit
Communication between BS and mobile is defined by a standard Common Air interface (CAI) that specifies 4 different channels
Forward voice channel (FVC) Channels used for voice transmission from BS to MS
Reverse voice channel (RVC) Channels used for voice transmission from MS to BS
Forward control channel (FCC) and reverse control channel (RCC) Channels responsible for initiating mobile calls Involved in setting up a call and moving it to an unused voice channel Handles supervisory and data messages to facilitate automatic
channel changes and handoff instructions