FIXED TELEPHONE, MOBILE TELEPHONE AND SATELLITE COMMUNICATION SYSTEMS
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Flexible · Affordable · Accessible the people’s university TEL 213/05 Telecommunication Principle Tutorial 4: FIXED TELEPHONE, MOBILE TELEPHONE AND SATELLITE COMMUNICATION SYSTEMS Semester January 2012
FIXED TELEPHONE, MOBILE TELEPHONE AND SATELLITE COMMUNICATION SYSTEMS
FIXED TELEPHONE, MOBILE TELEPHONE AND SATELLITE COMMUNICATION SYSTEMS
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1. Flexible Affordable Accessible the peoples university TEL
213/05 Telecommunication Principle Tutorial 4: FIXED TELEPHONE,
MOBILE TELEPHONE AND SATELLITE COMMUNICATION SYSTEMS Semester
January 2012
2. the peoples university Flexible Affordable Accessible
Introduction Students used to focus on either data communications
or voice communications. Today, the two fields are merging. Most
voice systems are computer controlled and data networks support
voice. Anyone studying the field of data communications and
networks must learn some basic telecommunications too.
Telecommunications used to be just voice.
3. the peoples university Flexible Affordable Accessible Basic
Telephone Systems POTS is the plain old telephone system that
connects most homes and small businesses. POTS lines were designed
to transmit the human voice, which has a bandwidth less than 4000
Hz. A telephone conversation requires two channels, each occupying
4000 Hz.
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Various telephone channels and the assignment of frequencies
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Limitations of Basic Telephone Systems A 4000 Hz analog signal can
only carry about 33,600 bits per second of information while a 4000
Hz digital signal can carry about 56,000 bits per second. If you
want to send information faster, you need a signal with a higher
frequency. POTS cannot deliver faster signals.
6. the peoples university Flexible Affordable Accessible Basic
Telephone Systems - Loops The local loop is the telephone line that
runs from the telephone companys central office to your home or
business. The central office is the building that houses the
telephone companys switching equipment and provides a local dial
tone on your telephone. If you place a long distance call, the
central office passes yourtelephone call off to a long distance
provider.
7. the peoples university Flexible Affordable Accessible Local
Loops
8. the peoples university Flexible Affordable Accessible Local
Access Transport Areas The USA is divided into a few hundred local
access transport areas (LATAs). If your call goes from one LATA to
another, it is a long distance call and is handled by a long
distance telephone company. If your call stays within a LATA, it is
a local distance call and is handled by a local telephone
company.
9. the peoples university Flexible Affordable Accessible Trunk
A trunk is a special telephone line that runs between central
offices and other telephone company switching centers. A trunk is
usually digital, high speed, and carries multiple telephone
circuits. A trunk is typically a 4-wire circuit, while a telephone
line is a 2-wire circuit. Not associated with a single telephone
number like a line is. A telephone number consists of an area code,
an exchange, and a subscriber extension. The area code and exchange
must start with the digits 2-9 to separate them from long distance
and operator services.
10. the peoples university Flexible Affordable Accessible When
the telephone company installs a line, it must not proceed any
further than 12 inches into the building. This point is the
demarcation point, or demarc. Modular connectors, such as the
RJ-11, are commonly used to interconnect telephone lines and the
telephone handset to the base. When the handset is lifted off the
base (off-hook), an off- hook signal is sent to the central
office.
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Telephone Systems Services Foreign exchange service (FX) - customer
calls a local number which is then connected to a leased line to a
remote site. Wide area telecommunications services (WATS) discount
volume calling to local and long distance sites. Off premises
extensions (OPX) - dial tone at location B comes from the PBX at
location A.
12. the peoples university Flexible Affordable Accessible PBX
Private branch exchange (PBX) - a common internal phone switching
system for medium to large-sized businesses. Provides advanced
intelligent features to users, such as: 4-digit, special prefixes
for WATS (wide area telephone service), FX, etc (private dialing
plans) PBX collects dialed digits and intelligently decides how to
route this call for lowest cost
13. the peoples university Flexible Affordable Accessible PBX
Advanced Features Voice mail Routes incoming calls to the best
station set (automatic call distribution) Provides recorded
messages and responds to touch-tone requests (automated attendant)
Access to database storage and retrieval (interactive voice
response)
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Components CPU, memory, telephone lines, trunks Switching network
Supporting logic cards Main distribution frame Console or
switchboard Battery back-up system
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Cordless system What is cordless system? History of cordless
system. Frequencies Performance Wireless phone handsets Types of
cordless system Analog Digital
16. the peoples university Flexible Affordable Accessible What
is cordless system? Cordless system is basically general term of
cordless telephones and cordless telecommunication systems. Cord
means wire , so cordless system means wireless system.
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Cordless telephone with base
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Definition: A cordless telephone or portable telephone is a
telephone with a wireless handset that communicates via radio waves
with a base station connected to a fixed telephone line, usually
within a limited range of its base station (which has the handset
cradle). The base station is on the subscriber premises, and
attaches to the telephone network the same way a corded telephone
does.
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Current cordless telephone standards, such as PHS and DECT, have
blurred the once clear-cut line between cordless and mobile
telephones by implementing cell handover, various advanced
features, such as data-transfer and even, on a limited scale,
international roaming.
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Unlike a corded telephone, a cordless telephone needs mains
electricity to power the base station. The cordless handset is
powered by a rechargeable battery, which is charged when the
handset sits in its cradle.
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Limitations: Residential a single base station can provide in-house
voice and data support Office A single base station can support a
small office Multiple base stations in a cellular configuration can
support a larger office Telepoint a base station set up in a public
place, such as an airport
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Frequencies In the US, seven frequency bands have been allocated by
the FCC for uses that include cordless phones. These are: 1. 1.7
MHz (1.64 MHz to 1.78 MHz & up to 5 Channels, AM System) 2.
4350 MHz (Base: 43.72-46.97 MHz, Handset: 48.76- 49.99 MHz,
allocated in 1986 for 10 channels, and later 25 Channels, FM
System) 3. 900 MHz (902928 MHz) (allocated in 1990) 4. 1.9 GHz
(18801900 MHz) (used for DECT communications outside the U.S.)
23. the peoples university Flexible Affordable Accessible 5.
1.9 GHz (1920-1930 MHz) (developed in 1993 and allocated U.S. in
October 2005) 6. 2.4 GHz (allocated in 1998) 7. 5.8 GHz (allocated
in 2003 due to crowding on the 2.4 GHz band).
24. the peoples university Flexible Affordable Accessible Types
(standards) of Cordless telephone Digital cordless phones (i)
Digital Enhanced Cordless telecommunication(DECT) (ii)Personal
Handy-Phone System(PHS) Analog cordless phones The main distinction
among types of cordless phones is the way to transmit their
signals.
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Application of DECT Domestic cordless telephony, using a single
base station to connect one or more handsets to the public telecoms
network. Enterprise premises cordless PABXs and wireless LANs,
using many base stations for coverage. Calls continue as users move
between different coverage cells, through a mechanism called
handover. Calls can be both within the system and to the public
telecoms network. Public access, using large numbers of base
stations to provide high capacity building or urban area coverage
as part of a public telecoms network. Fido
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Features of DECT Typical abilities of a domestic DECT Generic
Access Profile (GAP) System include: Multiple handsets to one base
station and one phone line socket. This allows several cordless
telephones to be placed around the house, all operating from the
same telephone jack. Interference-free wireless operation to around
100 metres (109 yards) outdoors, much less indoors when separated
by walls . - For instance, generally immune to interference from
other DECT systems, Wi-Fi networks, video senders, Bluetooth
technology, baby monitors and other wireless devices.
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Mobile Telephone Systems
28. the peoples university Flexible Affordable Accessible Early
Cellular Telephone Systems Advanced Mobile Phone System (AMPS)
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Problem with AMPS
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Mobile Telephone Switching Office (MTSO) Systems
31. the peoples university Flexible Affordable Accessible FDMA
in Mobile Phones Frequency division multiple access (FDMA) systems
are like frequency division multiplexing in that they allow many
users to share a block of spectrum by simply dividing it up into
many smaller channels. Each channel of a band is given an assigned
number or is designated by the center frequency of the channel. One
subscriber is assigned to each channel. Typical channel widths are
30kHz, 200kHz, 1.25MHz and 5MHz.
32. the peoples university Flexible Affordable Accessible FDMA
Process 1. A base station can receive radio signals in a given band
of spectrum 2. The band of frequency is broken up into smaller
bands (subbands) 3. Each transmitter (user) transmits to the base
station using radio waves in its own subband 4. When a user is
assigned to a subband, it transmits to the base station using a
sine wave with the center frequency in that band 5. When the base
station is tuned to the frequency of the desired user, it receives
no portion of the signal transmitted by another in-cell user. 6.
Multiple local transmitters in a cell do not interfere with one
another.
33. the peoples university Flexible Affordable Accessible Time
division Multiplexing (TDMA)
34. the peoples university Flexible Affordable Accessible TDMA
Process 1. Time is broken into time slots (small, equal-length
intervals) 2. Assume there are N users in the cell 3. Base station
groups N consecutive slots into a frame 4. Each user is assigned
one slot per frame. This slot assignment stays fixed as long as the
user communicates with the base station (the length of the phone
conversation) 5. In each time slot, the assigned user transmits a
radio wave using a sine wave at the center frequency of the
frequency band assigned to the base station.
35. the peoples university Flexible Affordable Accessible Code
division Multiple Access (CDMA)
36. the peoples university Flexible Affordable Accessible CDMA
Method 1 (frequency hopping Method) 1. Each user is assigned a
frequency hopping pattern (a fixed set of frequency values) 2. Time
is divided into slots 3. In the first time slot, a given user
transmits to the base station using the first frequency in its
frequency hopping sequence. 4. In the next time interval, it
transmits using the second frequency value in its frequency hope
sequence, and so on. This way the transmit frequency keeps changing
in time.
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Satellite Movement
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Satellite Formulas
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Satellite Formulas Keplers third Law:
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Example Satellite Calculations
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Solution
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Communication Satellites Communication satellites are not
originators of the signal to be transmitted Act as relay stations
for earth sources The satellite contains a receiver that picks up
the transmitted signal, amplifies it, and translates it to another
frequency (uplink 6GHz). The signal is then retransmitted to the
receiving stations on earth (downlink 4 GHz). Known as
transponder.
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Satellite Bands and Frequencies As C Band is full, most modern
satellite systems use the Ku Band:
44. the peoples university Flexible Affordable Accessible The C
Band
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Example A mobile transponder operates in the C band. Assume a local
oscillator frequency of 2GHz. What is the uplink receiver frequency
if the downlink transmitter is on channel 4? What is the maximum
theoretical date rate if one transponder is used for binary
transmission?
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Solution The downlink frequency of channel 4 is 3840 MHz. The
downlink frequency is the difference between the uplink frequency
fu and the local oscillator frequency, fLO The bandwidth of one
transponder channel is 36MHz. For binary transmission, the maximum
theoretical data rate or channel capacity C for a given bandwidth B
is: C=2B =2(36)=72Mbps
47. the peoples university Flexible Affordable Accessible TDMA,
FDMA, CDMA To maximize the use of the available spectrum in
satellite transponders and to ensure access for as many users as
possible, all satellites use some form of multiplexing.
Frequency-division multiplexing (FDMA) was used in early
satellites. Time division multiple access (TDMA) is used in newer
satellites.
48. the peoples university Flexible Affordable Accessible TDMA,
FDMA, CDMA TDMA assigns each user a time slot on the full bandwidth
of the transponder channel. Modulation methods are BPSK and QPSK,
although multilevel QAM (16 QAM, 32 QAM, 256 QAM) is used to
increase digital transmission speeds at a given bandwidth.
Code-division multiple access (CDMA) spreads the signals of
multiple users over the full transponder channel bandwidth and sort
them by the use of pseudorandom codes. CDMA also provides security
and provides multiple access while conserving spectrum.
49. the peoples university Flexible Affordable Accessible Thank
you!