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Computing and IT in the WorkplaceCT006-1
Mobile Computing
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Computing and IT in Workplace Chapter 7 2
Learning Outcomes
At the end of this section,YOU should be able to:
Describe the development of mobile computing
Explain the various types of mobile computing and their
differences
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What is Mobile Computing?
What is mobile computing?
User access to networks with the help of portable communication
devices such as laptops and PDAs.
This would allow users to:
Access,
Transfer,
Share,
data or information at any time and place.
This form of communication also enable users to be mobile & wireless
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What is Mobile Computing?
Definition of the terms mobile and wireless:
mobile can refer to User mobi l i tyand Device po rtabi l ity:
User mobility. This means users who have access to the same
or similar telecommunication services at different places. Device portability. It refers to the communication device that
moves (with or without a user).
wireless refers to communication devices:
This involves accessing a network or other communication
partners without the use of wires.
A communication device can thus exhibit one of the following
characteristics: Fixedand wired, Mobile and wired, Fixedand
wireless, and Mobile and wireless.
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What is Mobile Computing?
Fixedand wired: Refers to a typical desktop computer in an office.
Contributing factors are; Heavy in weight, High power consumption, and Uses
cabled networks.
Mobi leand wired: Refers to laptops. Contributing factors are; light in weight, uses
the telephone network and a modem.
Fixedand wireless: Refers to network installations. Contributing factors are: To
avoid damage by installing wires, fast network setup, and option for not wanting to
lease lines from competitor.
Mobi leand wireless: Refers to total portability. Contributing factors are: No cable
restrictions, controlled roaming between wireless networks. In relation to thismodule, this approach and its accompanying technologies shall be the main focus!
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Where can mobile computing be applied?
Where can mobile computing be applied?
This refers to scenarios where the use of mobile and wireless devices is suitable
and beneficial. With continuous advancements and growth of such devices today,
the spectrum it affects is wide.
Common application areas for wireless networks and mobile communicationincludes:
Vehicles
Emergencies
Businesses
Replacement of wired networks
Infotainment and more
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Where can mobile computing be applied?
Vehicles
Already in place in some vehicle commercially available. Includes devices,
instruments, and application enabling passengers to be informed or even to
control their surroundings.
Examples may include; music, news, road conditions, weather reports, andother broadcast information received via digital audio broadcasting (DAB) with
1.5 Mbps.
Emergencies
Emergency services such as ambulances will have a high-quality wireless
connection to the hospital. This would allow vital information about injuredpersons to be sent to the hospital from the scene of the emergency.
Within the Hospital itself, mobile and wireless technology would also be
beneficial. Physicians and staff can have access to vital information even on
the move or during emergencies.
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Businesses
Particularly with respect to Sales staff who need instant access to the
companys database(s).
With wireless access, the portable devices used can be turned into a true
mobile office.However, efficient and powerful synchronization mechanisms are needed to
ensure data consistency.
Replacement of wired networks
This is used as an alternative owing to economical, environmental and
regulatory constraints, or flexibility issues.
Examples of application; Remote sensors, Tradeshows, and Historical
buildings.
Where can mobile computing be applied?
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Where can mobile computing be applied?
Infotainment and more
Wireless networks can provide up-to-date information at any appropriate
location. This involves access to the Internet.
Applications can include online payments, purchases, and even
entertainment. Enabling technologies:
UMTS (Universal Mobile Telecommunications System)
GPS (Global Positioning System)
WLAN (Wireless Local Area Network) / Piconets
GSM (Global System for Mobile communication)
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The devices used for mobile computing
The devices used for mobile computing
The devices introduced change and evolve constantly particularly in relation
to the size, shape, weight, and computing power.
Thus, there may be a grey area when it comes to classifying the devices.
The following is a list of examples of mobile and wireless devices based ontheir increasing performance (CPU, memory, display, input devices, etc.):
Sensor
A very simple wireless device which is represented by a sensor
transmitting state information. (Example: An alarm system that could
warn the owner of the house if theres been a break-in via SMS)
Embedded controllers
Many of todays appliances can contain a simple or sometimes more
complex controllers. (Example: Remote gates, or activating the
Microwave oven using the mobile phone)
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Pager
A very simple to use receiver which mostly can display only short text
messages. There are two versions: One-way and Two-ways pagers.
However, this device has been superseded by Mobile phones.
Mobile phonesA device which has increased in its capabilities to the extent of
incorporating those of a PDA and is gaining in popularity. This gave rise
to the term PDA phones.
Personal digital assistant (PDA)
Typically used as an organizer and offers simple to relatively complicated
office software. Such devices also allow for upgrades through flash cards
or expansion cards with various functionality. The popularity of PDAs
may be superseded by PDA phones
The devices used for mobile computing
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Pocket computer
The next steps toward full computers capability are pocket computers
offering tiny keyboards, colour displays, and simple versions of
programs. Communication for such devices can be in the form of
Bluetooth, InfraRed, or Wi-Fi.
Notebook/laptop
Such devices offer more or less the performance of standard desktop
computers and most of time, the same software as well. Communication
for such devices can either be wired or wireless. As for the latter, again it
can be via Bluetooth, InfraRed, or Wi-Fi.
The devices used for mobile computing
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Issues affecting mobile computing
Issues affecting mobile communication
Interference
Wireless communication unlike wired, the transmission medium used cannot
be protected against interference using shielding like a cable. Sources of
interference include; Radio Frequency (RFI) and Electromagnetic (EMI)interference.
Regulations and spectrum
Frequencies have to be coordinated, and unfortunately, only a very limited
number are available owing to technical and political reasons. Thus, new
research on how to use available frequencies more efficiently is being carriedout.
Low bandwidth
Although the bandwidth and speed is gradually increasing, it still losses out to
the wired bandwidth. While local wireless networks may support up to 54
Mbps, wide area networks only offer some 10 Kbps.
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Issues affecting mobile computing
This is nowhere near to the 1 Gbps of the wired equivalent. To remedy this,
researchers have to look for more efficient communication protocols with low
overhead.
High delays, large delay variation
A serious problem for communication protocols used in todays Internet is thebig variation in link characteristics. In wireless systems, delays of several
seconds can occur, and links can be very asymmetrical.
Lower security, simpler to attack
There is a large threat of eavesdropping owing to the nature of radio
interface. Security techniques and mechanisms must not only be in place but
should be efficient and simple to use.
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Issues affecting mobile computing
Shared medium
Since radio access is achieved through a shared medium therefore the
service providers would have to compete for the medium. One major
issue arising is how to provide quality of service efficiently with different
combinations of access, coding, and multiplexing schemes.
Ad-hoc networking
Wireless and mobile computing allows for spontaneous networking with
prior set-up of an infrastructure. However, this has raised concerns over
routing capabilities, service discovery, network scalability, reliability, andstability.
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Principles behind mobile computing systems
Following the standard basic reference model to structure
communication systems.
This involves a 5-tier protocol stack implemented in the communication
systems.
The full protocol stack consists of different layers; Application layer,Transport layer, Network layer, Data link layer, and Physical layer.
The following diagram illustrates where the protocol stack is applied to for
the mobile and wireless communication system:
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Principles behind mobile computing systems
Application
Transport
Network
Data Link
Physical
Application
Transport
Network
Data Link
Physical
RadioMedium
Physical
Data Link
Network
Data Link
Physical
Network
Public switch
Pen computer
Radio tower
VAX
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Principles behind mobile computing systems
Application layer
The applications are situated on top of all transmission-oriented layers.
Issues addressed includes:
- service location,- support for multimedia applications,
- adaptive applications that can handle the large variations in
transmission characteristics, and
- wireless access to the WWW using portable device.
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Principles behind mobile computing systems
Transport layerThis layer is used in the reference model to establish an end-to-end
connection. Issues addressed includes:
- quality of service,
- flow and congestion control, and
- transport protocols known from the Internet, TCP, and UDP, are to
be used over a wireless link.
Network layer
This layer is responsible for routing packets through a network or
establishing a connection between two entities over many other immediate
systems. Issues addressed includes:- addressing,
- routing,
- device location, and
- handover between different networks.
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Principles behind mobile computing systems
Data link layer
The main tasks of this layer includes:
- accessing the medium,
- multiplexing of different data streams,
- correction of transmission errors, and
- synchronization(i.e., detection of a data frame).
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Principles behind mobile computing systems
Physical layer
This is the lowest layer in a communication system and is responsible
for the conversion of a stream of bits into signals that can be
transmitted on the sender side. For wireless communication, the
issues to be addressed are:
- frequency selection,
- generation of the carrier frequency,
- signal detection, and
- modulation of data onto a carrier frequency (depending on
the transmission scheme).
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Wireless Network
A short history of wireless computing
First Generation (1G)
Wireless technologies includes AMPS (Advanced Mobile Phone system) used
in the US, TACS (Total Access Communication System) in Europe, and NMT
(Nordic Mobile Telephone) in Japan. All these were analog systems. Thismeans they can only be used for voice and have highly variable call quality
and are very insecure. Typical data rates were 9.6kbps or lower.
Second Generation (2G)
Technologies includes TDMA (Time Division Multiple Access) and CDMA
(Code Division Multiple Access) used in the Unites States, PDC (PersonalDigital cellular) in Japan, and GSM (Global Systems for Mobile
communications) in Europe. All these are digital in nature and provide
improved system performance and security. Typical data rates vary from
9.6kbps to 14.4kbps.
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Wireless Network
A short history of wireless computing
Third Generation (3G)
Technologies includes UMTS (Universal Mobile Telecommunications System)
used in Europe and CDMA2000 (Code Division Multiple Access). Data rates
range from 144kbps to 2000kbps.
Fourth Generation (4G)
Technologies which are still in the research labs now. It focuses on Wireless
Asynchronous Transfer Mode (WATM) which has the potential to provide data
rates of 10Mbps to 150Mbps, low bit error rate, and high quality of service.
Bit error rate(BER): BER is the number of error bits in a signal expressed as afraction of the number of transmitted bits.
Quality of service(QoS): Qos is a measurement of guarantees that can be made
in meeting certain performance requirements.
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Wireless Network
Introduction to Wireless LAN
The global goal of WLANs is to replace office cabling, to enable
connectionless access to the internet and to introduce a higher flexibility for
ad-hoc communication.
Some advantages of WLANs are:
Flexibility
Within radio coverage, nodes can communicate without further
restriction. Radio waves can penetrate walls, senders and receivers can
be placed anywhere.
Planning
Only wireless ad-hoc networks allow for communication without previous
planning, any wired network needs wiring plans.
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Design
Wireless networks allow for the design of small, independent devices
which can for example be put into a pocket. Cables not only restrict users
but also designers of small PDAs, notepads etc.
Robustness
Wireless networks can survive disasters or users pulling a plug. Networks
requiring a wired infrastructure will usually break down completely.
Cost
After providing wireless access to the infrastructure via an access point forthe first user, adding additional users to a wireless network will not
increase the cost.
Advantages Wireless Network
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Disadvantages of Wireless Network
However, WLANs also have several disadvantages: Quality of service
WLANs typically offer lower quality than their wired counterparts. The
main reasons for this are the lower bandwidth due to limitations in radio
transmission, higher error rates due to interference, and higher
delay/delay variation due to extensive error correction and detectionmechanisms.
Proprietary solutions
Due to slow standardization procedures, many companies have come up
with proprietary solutions offering standardized functionality plus many
enhanced features.
Restrictions
All wireless products have to comply with national regulations. Several
government and non-government institutions worldwide regulate the
operation and restrict frequencies to minimize interference.
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Disadvantages of Wireless Network
Safety and security
Using radio waves for data transmission might interfere with high-
tech equipment in, e.g., hospitals. Special precautions have to be
taken to prevent safety hazards.
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Commercial Success of Wireless Network
Many different, and sometime competing, design goals have to be taken into
account for WLANs to ensure their commercial success:
Global operation
WLAN products should sell in all countries so, national and international
frequency regulations have to be considered.
Low power
Devices communicating via a WLAN are typically also wireless devices
running on battery power. The LAN design should take this into account and
implement special power-saving modes and power management savings.
License-free operation
LAN operators do not want to apply for a special license to be able to use
the product. The equipment must operate in a license-free band, such as the
2.4 GHz ISM band.
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Commercial Success of Wireless Network
Robust transmission technology
Compared to their wired counterparts, WLANs operate under difficult
conditions. If they use radio transmission, many other electrical devices can
interfere with them (vacuum cleaners, hairdryers, etc.)
Simplified spontaneous cooperation
To be useful in practice, WLANs should not require complicated setup
routines but should operate spontaneously after power-up. These LANs
would not be useful for supporting, ad-hoc meetings.
Easy to use
In contrast to huge and complex wireless WANs, wireless LANs are madefor simple use. They should work on plug-and-play.
Protection of investment
A lot of money has already been invested into wired LANs. The WLANs
should protect this investment by being interoperable with the existing
networks.
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Commercial Success of Wireless Network
Safety and security
Wireless LANs should be safe to operate, especially regarding low
radiation if used e.g., in hospitals. Users cannot keep safety distances
to antennas.
Transparency for application
Existing applications should continue to run over WLANs, the only
difference being higher delay and lower bandwidth.
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Cellular Network
Digital cellular networks are the segment of the market for mobile and
wireless devices which are growing most rapidly.
They are the wireless extensions of traditional PSTN or ISDN networks. It
has provided faultless roaming with the same mobile phone nation or even
worldwide.Today, data traffic is continuously growing, which sees the advancements
in wireless data transmission using cellular systems.
One such system is Global Systems for Mobile communications
(GSM), which happen to be the most popular digital system according
to the worldwide market (GSM Association, 2002).
GSM chosen as the main focus despite being a fully digital 2G system
because of its market success and also due to the system architecture
that served many other systems as an early example.
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Cellular Network
GSM has many open interfaces and network entities defined in its
specification.
This enabled network providers to choose between many different
products from different vendors.
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A short history of cellular networks
The first generation comprises analog systems, which typically rely
on FDMA.
The first 2G systems hit the market in the early nineties.
In the US D-AMPS was a digital successor of AMPS.In Europe, GSM was developed as a replacement for several
versions of NMT, and PDC was introduce in Japan.
All the above mentioned 2G systems introduced a TDMA mechanism
in addition to FDMA, which is still used for channel separation.
With cdmaOne, the first CDMA technology was available in the US
as a competitor to TDMA.
Between the second and third generation there is no real
revolutionary step.
Cellular Network
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CDMA/FDMA/TDMA
Which telecommunication service is
better for you?
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Computing and IT in Workplace Chapter 7
International Cocktail Party
FDMA Large room divided up into small
rooms. Each pair of people takes turns
speaking.
TDMA Large room divided up into smallrooms. Three pairs of people per room,
however, each pair gets 20 seconds to speak.
CDMA No small rooms. Everyone is speakingin different languages. If voice volume is
minimized, the number of people is maximized.
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Definitions
TDMA Time Division Multiple Access
FDMA Frequency Division Multiple Access
CDMA Code Division Multiple Access
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Cellular Network
GPRS introduced a packet-oriented service and higher data rates to
GSM (but can also be used for TDMA systems in general).
EDGE proposes a new modulation scheme, and cdmaOne was
enhanced to cdma2000 1x offering higher data rates.
All three systems mentioned above are often called 2.5G systems.
Following was the inclusion of CDMA technology to the systems to
become 3G systems.
While the number of different systems might be confusing, there are
some natural development paths. Most network providers offering GSM
service today will deploy UMTS, while cdmaOne users will choose
cdma2000 for simpler migration.
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Global System for Mobile Communication - GSM
Used by over 800 million people in more than 190 countries, it is regarded as
the most successful digital mobile telecommunication system around the
world.
The primary goal of GSM was to provide a mobile phone system that
allows users to roam throughout Europe and provides voice servicescompatible to ISDN and other PSTN systems.
GSM is a typical second generation system, replacing the first
generation analog systems.
However, it does not offer high worldwide data rates that the third
generation systems such as UMTS, are promising.
GSM was initially deployed in Europe using 890-915 MHz for uplinks
and 935-965 MHz for downlinks, which is now called GSM 900.
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Global System for Mobile Communication - GSM
Later versions include:
GSM 1800 MHz (1710-1785 MHz uplink, 1805-1880 MHz
downlink) which is also called DCS (digital cellular system) 1800
GSM 1900 MHz used in the US adopts 1850-1910 MHz uplinkand 1930-1990 MHz downlink, also called PCS (personal
communication service) 1900.
Generally GSM was designed for voice services and it still constitutes
the main use of this system.
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Review Questions
Discuss the various types of wireless networks
and cellular networks.
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Q & A
Question and Answer Session
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Topic and Structure of next session
Real Time System 1
What we will cover next