Wireless Communications and
Mobile Computing
Wireless Communications and
Mobile Computing
Chapter 1
Introduction
Outline

Introduction

History wireless communications

Types of services

wireless vs mobile

Strength and weaknesses

Applications
Introduction

Wireless communication involves the process of sending/reciving
information through invisible waves in the air.
- Information such as text, voice, and video are carried through the radio
frequency of electromagnetic spectrum.

Electromagnetic spectrum refers to invisible radio frequencies on which
wireless signals travel. E.g: TV remote control uses Infrared Wave.

Wireless Communication is one of the biggest engineering success
whose market size dominating the whole economy.
e.g + 5 billion GSM subscribers are there in the world.

The working habits, have been changed to “anywhere, anytime.”
- Mobility of workers have increased.
Cont...
 Large number of applications have been developed,
- wireless sensor networks monitor factories,
- wireless links replace the cables between computers & keyboards
mouse and other peripheral devices.
- wireless positioning systems monitor the location of trucks.

This variety of new applications cause technical challenges for
the wireless engineers to become bigger with each day.
History : How it all started



Marconi invented the wireless telegraph in 1896.
 By encoding alphanumeric characters in analog signals, he sent
telegraphic signals across the Atlantic Ocean.
 This leds to many developments in wireless communication that
support radio, television, mobile telephone, and satellite systems
that have changed our lives.
Unidirectional information transmission: device either transmit
data or receive data, but not both.
- was done for entertainment broadcasting.
By the late 1930s, the need for bidirectional mobile communi
cations emerged.
– Military, police departments, fire station….
History....

Many sophisticated military radio systems were developed during
and after WW2.

1946, the first mobile telephone system have an interface to the
Public Switched Telephone Network (PSTN),
-
This interface was not automated, but rather consisted of human
telephone operators.
-
Has a total of six speech channels for the whole city, the system
soon met its limits.
 Led to investigations of how the number of users could be increased
History...

Researchers at AT & T’s Bell Labs found the answer:
- the cellular principle, where the geographical area is divided into
cells; different cells might use the same frequencies.
- To this day, this principle forms the basis for the majority of wireless communications.

In 1957, the Soviet Union launched the first satellite(Sputnik) an
d the U.S.A soon followed.
History: Cellular Systems

1970s saw a revived interest in cellular communications
- Device miniaturization made the vision of portable devices more
realistic.
- Motorola, AT&T, Ericson

Nordic Mobile Telephone (NMT) system
- use digital switching technology that allows to combine different cells
in a large area into a single network.

Advanced Mobile Phone System (AMPS).
- analog phone standards in the U.S.A


1980s, the phones were portable, but definitely not handheld.
- In most languages, they were just called “carphones”.
But at the end of the 1980s, handheld phones with good speech
quality and quite acceptable battery lifetime flourish.
History: GSM and the Worldwide Cellular
Revolution


Analog phones have a bad spectral efficiency and due to the rapid
growth of the cellular market, operators had a high interest in
making room for more customers.
In 1990s,the European Telecommunications Standards Institute
(ETSI) group came up with a digital cellular standard that would be
come mandatory throughout Europe and was later adopted in most
parts of the world:
- Global System for Mobile communications (GSM).
 GSM got wide acceptance with short period.
- better speech quality, and the possibility for secure communications.
- by the year 2000, market penetration in Western Europe and Japan
had exceeded 50% growth rates were spectacular.
Overview of
Cellular communication Systems

1G: Basic mobile telephony service
- Based on analog cellular technology
- American Mobile Phone (AMPS) and NMT in Europe


2G: mobile telephony services for mass users with encryption and
efficient utilization of the radio spectrum.
- Digital cellular technology……… GSM and CDMA
2.5G: Mobile Internet/data services together with voice services
- Packet switching technology adding into 2G
- Providing mobile data services over 2G networks
- GPRS (General Packet Radio Service) and EDGE

3G: enhanced 2.5G services with improved mobile internet
services and emerging new applications
- CDMA2000 and UMTS (Universal Mobile Telecommunication System)
History :New wireless systems
• A whole range of new services was introduced in the 1990s.
• Cordless started to replace the “normal” telephones.
- The first versions of these phones used analog technology; however,
digital technology proved to be superior. Among other aspects, the
possibility of listening into analog conversations, and the possibility
for neighbors to “highjack” an analog cordless Base Station (BS) and
make calls at other people’s expense, led to a shift to digital communi
cations.
 Fixed wireless access and Wireless Local Loop (WLL)
- to address the “last mile” problem: in other words, replacing the copper
lines to the homes of the users by wireless links, but without the specific
benefit of mobility.
Types of Wireless Services

Broadcast



The first wireless service was broadcast radio.
Properties
- information is only sent in one direction.
- transmitted information is the same for all users.
- information is transmitted continuously.
Simple
- Transmitter does not need to have any knowledge about the
receivers.
- Simplex
- No. of users does not matter.
Services…

Paging




unidirectional wireless communications systems.
Properties
- User can only receive information, but cannot transmit.
- The information is intended for, and received by, only a sing
le user.
- The amount of transmitted information is very small.
used by doctors, police allowing them to react to emergencies in
shorter time.
better area coverage
Services…

Cellular Telephony


most important form of wireless communications.
Properties: information flow is bidirectional.(full duplex)
Services…

Trunking radio


there is no connection between the wireless system and the PSTN;
 it allows the communications of closed user groups.
 Obvious applications include police departments, fire departments,
taxis, and similar.
Services

Group calls: several users simultaneously, or several conference call
between multiple users of the system.

Call priorities: enable the prioritization of calls and allow dropping a
low-priority call in favor of a high-priority one.

Relay networks: the range of the network can be extended by using
each Mobile Station (MS) as a relay station for other MSs.
Services…
Cordless telephony

describes a wireless link between a handset and a BS that is directly connec
ted to the public telephone system.

main difference from a cellphone is associated with, and can communicate
with, only a single BS thus no mobile switching center; rather, the BS is dir
ectly connected to the PSTN.

Properties

no need to find out the location of the MS. Similarly, there is no need to
provide for handover between different BSs.
there is no central system, there is no need for frequency planning.

there are no network operators that can charge fees for connections fro
m the MS to the BS;
Services…

Wireless Local Area Networks (WLANs)

very similar to that of cordless phones.

connecting a single mobile user device to a public landline system.
Laptop -to-Internet.
main advantage is convenience for the user, allowing mobility.
can even be used for connecting fixed- location computers (desktops).



Major difference between WLANs and cordless phones is the required data
rate( Cordless 64kbps, more than 700kbps for wLAN).

Number of standards have been developed for WLAN, all of which carry the
identifier IEEE 802.11.

The original IEEE 802.11 standard 1Mbit/s, the very popular 802.11b (also
known under the name WiFi) allows up to 11Mbit/s and the 802.11a extends
that to 55Mbit/s. Even higher rates are realized by the 802.11n standard.
Services…

Personal area network(PAN)





coverage area even smaller than that of WLANs,
number of standards for PANs have been developed by the IEEE 802.15
group
intended for simple “cable replacement” duties.
Ex: Bluetooth standard allow to connect a hands-free headset to a phone
without requiring a cable; here, the distance between the two devices is
less than a meter.
In such applications, data rates are fairly low (<1Mbit/s).
PAN…

Recently, wireless communications between (DVD player to TV), between
computer and peripheral devices (printer, mouse), and similar applications
have gained importance.
- data rates in excess of 100Mbit/s are used(DVD player to TV).

Networks for even smaller distances like Body Area Networks (BANs),
which enable communications between devices located on various parts of a
user’s body: monitoring of patients’ health and of medical devices.
e.g., pacemakers.
Services…
Fixed Wireless Access
Essentially replacing a dedicated cable connection between the user
and the public landline system.
- no mobility of the user devices.
The distances bridged by this services devices are much larger
(between 100m and several tens of kilometers).
• Its main market for covering rural areas, and for establishing connec
tions in developing countries that do not have any wired infrastructure
in place.
●
Services...

Ad hoc Networks and Sensor Networks

Up to now, we've dealt with infrastructure-based wireless communications,
Where certain components (base stations, TV transmitters, etc.) are intended
by design to be in a fixed location.
Devices are mobile, organize themselves into a network according to
their location and necessity. Such networks are called ad hoc networks.

There can still be “controllers” in an ad hoc network, but the choice of
which device acts as master and which as slave is done opportunistically
whenever a network is formed.
Cont...



The advantages of ad hoc networks
 low costs (because no infrastructure is required), high flexibility.
The drawbacks
 reduced efficiency, smaller communication range, and restrictions
on the number of devices that can be included in a network.
Ad hoc networks play a major role in the recent abundance of sensor
networks, which allow communications between machines for the
purpose of building control (controlling air conditioning, lighting, etc.,
based on sensor data), factory automation, surveillance, etc.
Satellite Systems

Cover very large areas.

Distance several hundred kilometers





the transmit powers need to be larger,
high-gain antennas need to be used,
communications from within buildings is almost impossible.
costs of setting up a satellite – are much higher
Global Positioning System (GPS) use growing

Satellite signals used to pinpoint location.

Popular in cell phones, PDAs, and navigation devices.
Is wireless mobile? Or Is mobile wireless?




Mobile and Wireless are often used interchangeably but in
reality, they are two very different concepts applied to modern
computing and technology.
Mobile is a word that is commonly used to describe portable
devices.
A mobile device is one that is made to be taken anywhere.
Therefore, it needs an internal battery for power, and must be
connected to a modern mobile network that can help it to send
and receive data.
Cont...


Wireless, on the other hand, does not mean mobile.
Traditional computers or other non-mobile devices can access
wireless networks.
Examples:


WLAN,
WAN can even use components of 3G or 4G wireless systems
made specifically for mobile devices, but that doesn’t mean
that the devices on these networks are mobile. They may still
be plugged in or require proximity to a router or network
node.
Cont...

A communication device can exhibit any one of the following
characteristics:

Fixed and wired


Example: desktop computer in an office. Neither weight nor power
consumption of the devices allow for mobile usage. The devices
use fixed networks for performance reasons.
Fixed and wireless:
 This mode is used for installing network e.g. in historical buildings
to avoid damage by installing wires or at trade shows to ensure fast
network setup. -> address the “last mile” problem.


Mobile and wired:
 Many of yesterday’s laptops fall into this category; users carry
the laptop from one hotel to others, reconnecting to the hotel’s
network via the telephone network and a modem.
Mobile and wireless:
 No cable restricts the user, who can roam between different
wireless networks.
 Most technologies discussed in this course deal with this type of
device and the networks supporting them.
 Today’s most successful example for this category is GSM with
more than 5 Billion users.
Service ?

What are the different types
of wireless services that we
have seen on the previous
class?

Broadcast

Paging

Cellular Telephony

Trunking Radio

Cordless Telephony

Wireless LAN,PAN,BAN

Fixed wireless access

Ad hoc and sensor Nets

Satellite services
Requirements..

Different applications have
different requirements

Data rate

Range & no of users

Mobility

Energy consumption

Use of spectrum

Direction of transmissions

Service Quality
Requirements…

Data rate : fewer bits/sec upto gigabits/sec
 Sensor networks: ~ 1kbits/s
 Temperature, speed ….
 Speech communications: 5 - 64kbits/s
 Cordless, Cellular telephony
 Elementary data service: 10 - 100kbits/s
 2G\2.5G cellular data service.
 Communication b/n computer peripherals: 1Mbits/s
 Mouse, key board…..
 High speed data: 0.5-100Mbits/s
 WLAN , 3G cellular
 PAN : 100Mbits/s
 Entertainment systems TV, DVD,Game, PC
Requirements…

Range (coverage area)






BAN: ~1M
PAN: ~10M
WLAN: few 100M
Fixed wireless: 5-10km
Cellular : 10-50Km
Satellite systems: 1000km- 36,000km
Data rate Vs Range
Requirements…

Mobility


Fixed devices: Office desktop
Nomadic: Certain place for certain time(min/hrs)


Low mobility: Pedestrian speed


Cordless telephone
High Mobility: 30-150km/h


Laptops
Vehicle
Extreme high mobility: 300-1000km/hr

High speed trains, planes
Data rate Vs Mobility
Requirements…

Energy consumptions: critical aspect

Rechargeable batteries




One way batteries


Nomadic & mobile devices
Standby time and operating time are critical.
Cellphone: Min 48hr standby 2hr talk time .
Sensors
Power mains

Base stations(BSs) and fixed devices.

Weight of MS is determined (70-80%) by its battery.

Weight & size are critical for sales.
Requirements...

Use of spectrum

Spectrum refers to the invisible radio frequencies that wireless signals travel over.
 Spectrum dedicated to service/operator
 Frequency controlled by operator.
 Free spectrums



Used by different service operators.
ISM radio band 2.4GHz: Micro oven , wifi, Bluetooth,…
Interference is managed by users.
Requirements…

Direction of transmission




Simplex
Half-duplex
Full duplex
Asymmetric duplex
Data rate depends on the direction.
Examples: Satellite uplink & downlink

Requirements…

Service Quality

Speech quality



Mean opinion score (MOS): rates the quality of image/voice
Subjective to human judgments.
Data transmission speed:
Measured in bits per second, bit/s
 Admissible delay(latency)


Voice less than 100milisec (if delay >100ms the quality and
consistency of the voice starts to decline)
Security & safety (sensors ) – latency is vital
Economic and social aspects

Strength

Social & cultural factor






Mobile life style (Anytime Anywhere)
Increase of social communication
Increase revenue & productivity
Ease of setup
Less expensive
Development in mobile devices(dynamic)
Cont...
Weakness and issues
Social issue
-
Technology issues
Privacy
Security (easy to tap)
Health issues (Brain cancer)
Noise pollution, (irritation in classroom)
Accident (use of cellphone while driving)
-
Lack of standards
High cost of technology
Quality of service
Device limitation
Low data rates
Applications….

List some wireless system applications in
different areas of our life?
At Home
satellite
WiFi
WiFi 802.11g/n
WiFi
WiFi
bluetooth
cellular
Applications….

List some wireless system applications in
different areas of our life?
On the Move
On the Road
GSM/UMTS,
20
DAB,
RA,
 Road condition,
 Weather,
 Location-based services,
 Emergency
Other Applications
•
Vehicles
•
Emergencies
•
Business
•
Agriculture
•
Replacement of wired networks
•
Infotainment and more
•
Location dependent services
Cont...
•
Vehicles
•
•
•
•
Navigation , tracking(GPS)
Music, news, weather report (DAB)
Collision avoidance(wireless sensors)
Accident reporting , Traffic reporting (Ad- hoc)
Fig: Stalled vehicle warning
Cont...
•
Emergencies
•
•
•
Wireless networks are the only means of communication
in the case of natural disasters such as hurricanes or eart
hquakes. (wireless ad-hoc networks)
Accident reporting (wireless sensors)
Business
•
Traveling salesman, having instant access to company’s
database: to ensure that files on his or her laptop reflect
the current situation(business) anytime anywhere
Cont...
•
Agriculture and Natural Resources
Animal tracking and identification.
Monitoring water or flood levels.
Monitor crop health, rainfall, temperature and other met
erological data.
• Track shipments of perishable crops and crop inputs
Replacement of wired networks
•
Remote sensors for weather forecasts, earthquake detecti
on, or to provide environmental information.
•
•
•
•
Disaster Recovery/Military
•
Wireless communication and mobile computing capability
can make a difference between life and death!
• rapid deployment
• efficient resource and energy usage
• flexible: unicast, broadcast, multicast, anycast
• resilient: survive in unfavorable and untrusted
environments
Habitat Monitoring
Basestation
Future Wireless Networks
Ubiquitous Communication Among People and Devices
Next-generation Cellular
Wireless Internet Access
Wireless Multimedia
Sensor Networks
Smart Homes/Spaces
Automated Highways
In-Body Networks
All this and more …