Mobile communication_ch1.pdf

Chapter 1 Introduction to Wireless Comm. System
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Mobile communications
Chapter one:
Introduction to Wireless Communication System
‫وااللكترونية‬ ‫الكهربائية‬ ‫الهندسية‬ ‫التقنيات‬ ‫كلية‬
‫الحاسوب‬ ‫تقنيات‬ ‫هندسة‬ ‫قسم‬
‫محمد‬ ‫طاهر‬ ‫الحمزة‬ .‫م‬ : ‫المادة‬ ‫مدرس‬
‫المرحلة‬
‫الرابعة‬

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Chapter 1
1.1History of wireless communications
Guglielmo Marconi invented the wireless telegraph in 1896. In 1901, he sent telegraphic signals
across the Atlantic Ocean (about 3200 km). His invention allowed two parties to communicate
by sending each other alphanumeric characters encoded in an analog signal. Over the last
century, advances in wireless technologies have led to the radio, the television, the mobile
telephone, and communications satellites. All types of information can now be sent to almost
every corner of the world. Recently, a great deal of attention has been focused on satellite
communications, wireless networking, and cellular technology. Wireless networking is allowing
businesses to develop WANs, MANs, and LANs without a cable plant. The cellular or mobile
telephone is the modern equivalent of Marconi's wireless telegraph, offering two-party, two-way
communication. The first-generation wireless phones used analog technology. These devices
were heavy and coverage was patchy, but they successfully demonstrated the inherent
convenience of mobile communications. The current generation of wireless devices is built using
digital technology. Digital networks carry much more traffic and provide better reception and
security than analog networks.
Fig. (1) Some milestones in Wireless Communications

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1.2 Evolution of mobile communications
 The first version of a mobile radio telephone being used in 1924.
 In 1926 telephone service in trains on the route between Hamburg and Berlin was approved
and offered to 1st class travelers.
 In 1935, Edwin Armstrong demonstrated FM and it has been the primary modulation
technique used for mobile communication systems throughout the world.
 In 1946, the first public mobile telephone service was launched in 25 cities across the United
States (543 users) by BELL Laboratories in USA. Early mobile systems used single high
power transmitters with AM Modulation techniques to give coverage up to about 50 miles
(only limited customers) could get the service. This inefﬁcient use of the radio spectrum
coupled with the state of radio technology at that time severely limited the system capacity.
 A solution to this capacity problem emerged during the 50’s and 60’s when researchers at
Bell Laboratories developed the cellular concept.
 In 1973, Martin Cooper (a Motorola researcher and executive) made the first mobile
telephone call from handheld subscriber equipment.
 In 1983, the ﬁrst analog cellular system deployed in Chicago, USA.
1.3 Mobile Radio Systems around the World
Many mobile radio standards have been developed for wireless systems throughout the world.
Tables below list the most common paging, cordless, cellular, and personal communications
standards used in North America, Europe, and Japan.
1- Post Office Code Standard Advisory Group (POCSAG)
- The world’s most common paging standard.
- Developed by the British Post Office in the late 1970s.
- Supports binary FSK signaling at 512 bps, 1200 bps, and 2400 bps.
2- Cordless telephony (CT2)
- Most popular cordless telephone standards throughout Europe and Asia.
- Developed in Europe.

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- Makes use of microcells which cover small distances, usually less than 100 m, using base
stations with antennas mounted on street lights or on sides of buildings.
- High quality voice transmission: uses battery efficient FSK along with a 32 kbps adaptive
differential pulse code modulation (ADPCM) speech coder.
- Handoffs between base stations are not supported, as it is intended to provide short range
access to the PSTN.
1.4 Classification of mobile radio transmission system
Mobile radio transmission systems may be classified as simplex, half-duplex or full-duplex.
a. Simplex systems: communication is possible in only one direction.
b. Half-duplex: radio systems allow two-way communication using the same radio channel
for both transmission and reception.
c. Full duplex: systems allow simultaneous radio transmission and reception between a
subscriber and a base station, by providing two simultaneous but separate channels
(frequency division duplex, or FDD) or adjacent time slots on a single radio channel
(time division duplex, or TDD) for communication to and from the user.
1.4.1 Frequency division & Time division
Provides simultaneous radio transmission channels for the subscriber and the base station, so that
they both may constantly transmit while simultaneously receiving signals from one another.
At the base station, separate transmit and receive antennas are used to accommodate the two
separate channels.
At the subscriber unit a single antenna is used for both transmission to and reception from the
base station, and a device called a duplexer is used inside the subscriber unit to enable the same
antenna to be used for simultaneous transmission and reception.

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(A) Frequency division duplexing (FDD)
A pair of simplex channels with a fixed and known frequency separation is used to define a
specific radio channel in the system.
- The channel used to convey traffic to the mobile user from a base station is called the
forward channel.
- The channel used to carry traffic from the mobile user to a base station is called the
reverse channel. FDD is used exclusively in analog mobile radio systems.
(B) Time division duplexing (TDD)
Uses the fact that it is possible to share a single radio channel in time, so that a portion of the
time is used to transmit from the base station to the mobile, and the remaining time is used to
transmit from the mobile to the base station. TDD is only possible with digital transmission
formats and digital modulation, and is very sensitive to timing. It is for this reason that TDD has
only recently been used, and only for indoor or small area wireless applications.
1.4.2 Transmission types
•Unicast (point-to-point) transmission is made from one device to a single other device. It means
that the packet is addressed to one receiver.
•Broadcast transmission is made from one device to all other devices. In this case there is just
one sender, but the information is sent to all connected receivers.
•Multicast transmission is made from one device to a subset of the other available devices. In
this case there is just one sender, but the information is sent to a group of receivers.
1.5 Types of wireless communication systems
The major types of wireless communication systems are:
1- Paging Systems
2- Cordless Telephone Systems
3- Satellite communication systems
4- Wireless LAN systems
5- Cellular Telephone Systems

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The cost, complexity, performance, and types of services offered by each of these mobile
systems are different.
1- Paging Systems
Paging systems are communication systems that send brief messages to a subscriber. Depending
on the type of service, the message may be either text or voice messages. In modern paging
systems, news headlines, stock quotations, and faxes may be sent. The issued message is called a
page. The paging system then transmits the page throughout the service area using base stations
which broadcast the page on a radio carrier.
- Paging systems vary widely in their complexity and coverage area.
- Paging systems are designed to provide reliable communication to subscribers. This
necessitates large transmitter powers and low data rates for maximum coverage from
each base station.
Simple paging systems may cover a limited range of 2 to 5 km, or may even be confined to
within individual buildings,
Wide area paging systems can provide worldwide coverage. Wide area paging systems consist
of a network of telephone lines, many base station transmitters, and large radio towers that
simultaneously broadcast a page from each base station (this is called simulcasting)
2- Cordless Telephone Systems
• Provide wireless extension to the telephone network within a limited area
• Two-way (duplex) communications
• Consists of a portable handset, connected to dedicated base station, which is connected to the
telephone network
• 1st generation: household environment
• 2nd generation: allow mobility in workplace and public use with limited coverage in urban
areas

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3- Satellite communication Systems
The main feature of the satellite communication systems
 Very wide range and coverage
 Very useful in sparsely populated areas: rural areas, sea, mountains, etc.
 Target: Vehicles and/or other stationary/mobile uses
 Expensive base station (satellites) systems
4- Wireless LAN (WLAN)
Characterized by
 Low mobility (not for vehicular use)
 High speed data transmission
 Confined regions – buildings and campuses
 Coverage: 100m – 300m per base station
 Uses the following bands (902-928 MHz, 2400-2483.5 MHz, 5725-5850 MHz)
5- Cellular Telephone Systems
The basic cellular system consists of: Mobile station (MS), Base stations (BS) and Mobile
switching center (MSC) or called Mobile telecommunications switching office (MTSO).
- Cellular systems accommodate a large number of users over a large geographic area,
within a limited frequency spectrum.
- Cellular radio systems provide high quality service that is often comparable to that of the
landline telephone systems.
- High capacity is achieved by limiting the coverage of each base station transmitter to a
small geographic area called a cell so that the same radio channels may be reused by
another base station located some distance away.
- Handoff: is a switching technique that enables a call to proceed uninterrupted when the
user moves from one cell to another.

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1.6 Comparison of Common Wireless Communication Systems
Tables below illustrate the types of service, level of infrastructure, cost, and complexity required
for the subscriber segment and base station segment of each of the mobile radio systems
discussed earlier.
Mobile stations:
Base stations:

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1.7 First Generation (1G) systems
The original cellular telephone networks provided analog traffic channels; these are now referred
to as first-generation systems. Since the early 1980s the most common first-generation system in
North America has been the Advanced Mobile Phone Service (AMPS). This approach is also
common in South America, Australia, and China.
 Two 25-MHz bands are allocated to AMPS.
 Each of these bands is split in two to encourage competition (i.e., so that in each market
two operators can be accommodated). An operator is allocated only 12.5 MHz in each
direction for its system.
 The channels are spaced 30 kHz apart, which allows a total of 416 channels per operator.
 21 channels are allocated for control, leaving 395 to carry calls.
 The control channels are data channels operating at 10 kbps.
 The conversation channels carry the conversations in analog using FM.
European Total Access Communication Systems (TACS):
- Deployed in 1985.
- Almost identical to AMPS except that the channel bandwidth is scaled to 25 kHz instead of
30 kHz as in AMPS.
Drawbacks
• Poor voice quality
• Poor battery life
• Limited capacity (number of subscribers)
• No security
• Poor handoff reliability (transition between cells)
• Large phone size

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1.8 Second Generation (2G) systems
Second-generation systems have been developed in early 90s to provide higher quality signals,
higher data rates for support of digital services, and greater capacity. Moreover, The 2G systems
provide:
- Digital voice coding and modulation
- Security (Encryption).
- Error detection and correction.
- Multiple channels per cell.
The key differences between the two generations are:
First Generation (1G) systems Second Generation (2G) systems
Analog systems Digital systems
Designed to support voice channels
using FM, digital traffic is supported
only by the use of a modem that converts
the digital data into analog form.
Provide digital traffic channels, these
readily support digital data; voice traffic is
first encoded in digital form before
transmitting.
No security.
Capable to encrypt the traffic to prevent
eavesdropping (since the user and control
traffics are digitized).
Poor voice quality.
Very clear voice reception, because The
digital traffic stream of lends itself to the
use of error detection and correction
techniques.
Each cell supports a number of channels.
At any given time a channel is allocated
to only one user.
Provide multiple channels per cell, but
each channel is dynamically shared by a
number of users using TDMA or CDMA.
No message service
Enable message service such as short
message service (SMS) and Multimedia
message service (MMS)

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Beginning around 1990, a number of different second-generation systems have been deployed,
such as Global system for mobile communications (GSM), and Interim Standard (IS-95) scheme.
The table below lists some key characteristics of three of the most important of these systems.
GSM IS-95
Year introduced 1990 1993
Developed in Europe North America
BS transmission band 935~960 MHz 869~894 MHz
MS transmission band 890~915 MHz 824~849 MHz
Spacing between forward
and reverse channels
45 MHz 45 MHz
Channel bandwidth 200 KHz 1250 KHz
No. of duplex channels 125 20
Mobile unit maximum power 20 W 0.2 W
Users per channel 8 35
Modulation GMSK QPSK
Carrier bit rate 270.8 kbps 9.6 kbps
The GSM standard has gained worldwide acceptance as the first universal digital cellular system
with modern network features extended to each mobile user
1.102.5 G systems
2.5G is a technology between the 2G and 3G; it is sometimes described as 2G technology
combined with GPRS. 2.5G is an interim solution designed to allow for improved data rates
before 3G implementation. A variety of 2.5G techniques are being employed to improve the
speed of data for enhanced e-mail and Internet access.

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The main features of the 2.5G are:
- Ability to send and receive Email messages.
- Web browsing,
- Speed: 64-144 kbps
Moreover, Built-in camera can be included in the mobile station (Camera phones).
General Packet Radio Service (GPRS)
 GPRS is packet switched technology which based on existing GSM cellular network
infrastructure and adds new packet-switching network equipment.
 The GPRS gives GSM subscribers access to data communication application such as e-
mail and internet using their mobile phone.
 Speed: up to 114 kbps
 The GPRS allows multiple slots of a GSM radio channel be dedicated to an individual
user (Physical channel can be shared between different mobile users).
 Physical channel is only assigned when data needs to be transmitted or received.
1.11 Third Generation (3G) systems
The objective of the third generation (3G) of wireless communication is to provide fairly high-
speed wireless communications to support multimedia, data, and video in addition to voice. 3G
developed in the early 2000s, the main features of the 3G systems are:
 High transmission rate and the support of multimedia services: Multiple-megabit
internet services, video calls, and mobile TV using a single mobile device.
 Data rate: around 2Mbps. Bandwidth: in the order of MHz
The ITU’s International Mobile Telecommunications for the year 2000 (IMT-2000) initiative has
defined the ITU’s view of third-generation capabilities as

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• Voice quality comparable to the public switched telephone network.
• 144-kbps data rate available to users in high-speed motor vehicles over large areas.
• 384 kbps available to pedestrians standing or moving slowly over small areas.
• Support for 2.048 Mbps for office use.
• Support for both packet-switched and circuit-switched data services.
• An adaptive interface to the Internet.
Generally, the technology planned is digital using TDMA or CDMA to provide efficient use of
the spectrum and high capacity.
3G enhancements
3G has the following enhancements over previous networks:
1. Enhanced audio and video streaming
2. Several times higher data speed
3. Video-conferencing support
4. Web and WAP browsing at higher speeds
5. IPTV (TV through the Internet) support
Universal Mobile Telecommunications System (UMTS)
UMTS is a third generation mobile cellular system for networks based on the GSM standard,
developed and maintained by the 3GPP (3rd Generation Partnership Project).
 Aims to provide services for both mobile and fixed subscribers by common call-
processing procedures.
 Uses W-CDMA radio access technology to offer greater spectral efficiency and
bandwidth to mobile network operators.
The UMTS network architecture is split into 3 parts:
1. Core (switching) networks: The core network is responsible for performing switching and
transmission functions. Also known as Mobile Application Part (MAP).

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2. Radio Access networks: provides channel access to mobile users and performs radio
resource management and signaling UMTS will include both terrestrial and global satellite
components. Also known as UMTS Terrestrial Radio Access Network (UTRAN).
3. User Equipment (UE): authentication of users via SIM (subscriber identity module) cards.
High Speed Packet Access (HSPA)
HSPA extends and improves the performance of existing 3G mobile telecommunication
networks utilizing the WCDMA protocols (also referred to as 3.5G). The HSPA specifications:
 increased peak data rates of up to
• 14 Mbit/s in the downlink
• 5.76 Mbit/s in the uplink.
 reduced latency
 Up to five times more system capacity in the downlink up to twice as much system
capacity in the uplink compared with WCDMA.
1.12 Pre-4G technology (3.9G)
The ITU specified a set of requirements for 4G standards, named the International Mobile
Telecommunications Advanced (IMT-Advanced) specification, setting peak speed requirements
for 4G service as follows:
 300 Mbps for high mobility communication (such as from trains and cars).
 1 Gbps for low mobility communication (such as pedestrians and stationary users).
Two 3.9G (Also known as 4G technology) standards are commercially deployed:
 Mobile WiMAX standard (first used in South Korea in 2007),
 Long Term Evolution (LTE) standard (first released in Oslo, Norway and Stockholm,
Sweden since 2009).

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Since the first-release versions of Mobile WiMAx and LTE support much less than 1 Gbps peak
bit rate, they are not fully IMT-Advanced compliant, but are often called 4G by service
providers.
Evolved HSPA (HSPA+)
A further improved 3GPP standard was released late in 2008 with subsequent worldwide
adoption beginning in 2010. The newer standard allows bit-rates to reach as high as 337 Mbit/s
in the downlink and 34 Mbit/s in the uplink. HSPA+ supported with multiple input, multiple
output (2x2 MIMO) technologies and higher order modulation (64 QAM).
Long Term Evolution (LTE)
LTE is a standard for wireless communication of high-speed data for mobile phones and data
terminals. It is based on the GSM/EDGE and UMTS network technologies, increasing the
capacity and speed using a different radio interface together with core network improvements.
The standard is developed by the 3GPP. The LTE features are:
 downlink peak rates of 300 Mbit/s,
 uplink peak rates of 75 Mbit/s
 Quality of Service (QoS) provisions permitting a transfer latency of less than 5 ms in the
radio access network (RAN).
 Has the ability to manage fast-moving mobiles
 Supports scalable carrier bandwidths, from 1.4 MHz to 20 MHz.
 Orthogonal frequency-division multiple access (OFDMA) for the downlink, Single-
carrier FDMA for the uplink to conserve power.
 Supports both FDD and TDD.

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1.13 Fourth Generation (4G) systems
4G provides mobile broadband Internet access, with higher data rate and expanded multimedia
services. The main features of the 4G systems are
 Higher speed 0.1~1 Gbps.
 More security.
 Higher capacity.
 Lower cost than previous generations.
 Provides digital system with voice over-IP (VOIP) technology.
 IPv6 Core.
 Orthogonal frequency-division multiplexing (OFDM) is used instead of CDMA.
One of the main differences between 3G and 4G technology is the elimination of circuit
switching, instead employing an all-IP network. Other differences are:
The 4G system are able to provide a comprehensive IP solution where voice, data and streamed
multimedia can be given to users on an "Anytime, Anywhere" basis.
LTE Advanced (LTE-A)
LTE Advanced is a mobile communication standard and a major enhancement of the Long Term
Evolution (LTE) standard. It was formally submitted as a candidate 4G system to ITU in late

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2009 as meeting the requirements of the IMT-Advanced standard, and was standardized by the
3GPP in March 2011.
The main features of the LTE-Advanced are:
 higher capacity,
 increased peak data rate,
- Downlink 3 Gbps,
- Uplink 1.5 Gbps
 Higher spectral efficiency (30 bps/Hz)
 Increased number of simultaneously active subscribers.
 LTE-Advanced can use up to 8x8 MIMO and 128 QAM in downlink direction.
LTE-Advanced is now available in 31 countries (including South Korea, Australia, France,
Germany, U.K. and the U.S.).

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1.14 Fifth Generation (5G) systems
5G denotes the next major phase of mobile telecommunications standards beyond 4G. 5G can be
a complete wireless communication without limitation, which bring us perfect real world
wireless, supportable to the World Wide Wireless Web (WWWW). The Next Generation Mobile
Networks Alliance defines the following requirements for 5G networks:
 Data rates of several tens of megabits per second should be supported for tens of
thousands of users.
 High speed, high capacity.
 Spectral efficiency should be significantly enhanced compared to 4G.
 Coverage should be improved.
 Signaling efficiency should be enhanced.
 Latency should be reduced significantly compared to LTE.
The Next Generation Mobile Networks Alliance feels that 5G should be rolled out by 2020 to
meet business and consumer demands. In addition to providing simply faster speeds, they predict
that 5G networks also will need to meet the needs of new use cases, such as:
 Internet of Things (IoT).
 Broadcast-like services and lifeline communication in times of natural disaster.
1.15 Evolution parameters of cellular systems
In order to offer higher quality of service to subscribers, the following parameters have
been developed in cellular systems:
1. Higher spectrum utilization efficiency
2. Introduction of new frequencies (radio bands) for use in cellular systems
3. Increased capacity to support more subscribers (users)
4. Higher data transfer rates
5. Offering new services such as Internet access and video calls
6. Improving coverage and hand-off while reducing interference

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7. Improved roaming capability to solve the fragmentation of standards
8. Enhanced security
9. Improved energy efficiency to provide longer talking time
10. Lower service cost

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