7 citw mobile computing

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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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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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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?


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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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.



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.





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)



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)



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




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.




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.




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.




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.



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:




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




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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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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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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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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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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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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Computing and IT in Workplace Chapter 7

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

7 citw mobile computing

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