1. Mobile Computing Introduction
UNIT – 1
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2. Wireless System Definitions
Mobile Station
A station in the cellular radio service intended for use while in motion at unspecified locations. They can be either hand-held personal units (portables) or installed on vehicles (mobiles)
Base station
A fixed station in a mobile radio system used for radio communication with the mobile stations. Base stations are located at the center or edge of a coverage region. They consists of radio channels and transmitter and receiver antennas mounted on top of a tower.
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3. Wireless System Definitions
Mobile Switching Center
Switching center which coordinates the routing of calls in a large service area. In a cellular radio system, the MSC connections the cellular base stations and the mobiles to the PSTN (telephone network). It is also called Mobile Telephone Switching Office (MTSO)
Subscriber
A user who pays subscription charges for using a mobile communication system
Transceiver
A device capable of simultaneously transmitting and receiving radio signals
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4. Wireless System Definitions
Control Channel
Radio channel used for transmission of call setup, call request, call initiation and other beacon and control purposes.
Forward Channel
Radio channel used for transmission of information from the base station to the mobile
Reverse Channel
Radio channel used for transmission of information from mobile to base station
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5. Wireless System Definitions
Simplex Systems
Communication systems which provide only one-way communication
Half Duplex Systems
Communication Systems which allow two-way communication by using the same radio channel for both transmission and reception. At any given time, the user can either transmit or receive information.
Full Duplex Systems
Communication systems which allow simultaneous two-way communication. Transmission and reception is typically on two different channels.
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6. Wireless System Definitions
Handoff
The process of transferring a mobile station from one channel or base station to an other.
Roamer
A mobile station which operates in a service area (market) other than that from which service has been subscribed.
Page
A brief message which is broadcast over the entire service area, usually in simulcast fashion by many base stations at the same time.
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7. Cellular Phone Networks
Kabul BS BS
Internet
Kandahar
MTSO
MTSO
PSTN BS
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8. Types of wireless communication
celullar
wireless computer network
radio service
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9. The Wireless Revolution
Cellular is the fastest growing sector of communication
industry (exponential growth since 1982, with over 2 billion users worldwide today)
Three generations of wireless
First Generation (1G): Analog 25 or 30 KHz FM, voice only, mostly vehicular communication
Second Generation (2G): Narrowband TDMA and CDMA, voice and low bit-rate data, portable units.
2.5G increased data transmission capabilities
Third Generation (3G): Wideband TDMA and CDMA, voice and high bit-rate data, portable units
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10. Wireless Local Area Networks (WLANs)
0101
1011
Internet
Access
Point
WLANs connect “local” computers (100m range)
Breaks data into packets
Channel access is shared (random access)
Backbone Internet provides best-effort service
Poor performance in some apps (e.g. video)
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11. Wireless LAN Standards
802.11b (Current Generation)
Standard for 2.4GHz ISM band (80 MHz)
Frequency hopped spread spectrum
Mbps, 500 ft range
802.11a (Emerging Generation)
Standard for 5GHz NII band (300 MHz)
FDM with time division
20-70 Mbps, variable range
Similar to HiperLAN in Europe
802.11g (New Standard)
Standard in 2.4 GHz and 5 GHz bands
FDM
Speeds up to 54 Mbps
In 200?,
all WLAN
cards will
have all 3
standards
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12. Design Challenges Hardware Design
Precise components
Small, lightweight, low power
Cheap
High frequency operations
System Design
Converting and transferring information
High data rates
Robust to noise and interference
Supports many users
Network Design
Connectivity and high speed
Energy and delay constrains
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13. The Need for Wireless/Mobile Networking
Demand for Ubiquitous Computing
Anywhere, anytime computing and communication
You don’t have to go to the lab to check your
Pushing the computers more into background
Focus on the task and life, not on the computer
Use computers seamlessly to help you and to make your life more easier.
Computers should be location aware
Adapt to the current location, discover services
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14. Some Example Applications of Ubiquitous Computing
You walk into your office and your computer automatically authenticates you through your active badge and logs you into the Unix system
You go to a foreign building and your Personal Digital Assistance automatically discovers the closest public printer where you can print your schedule and give to your friend
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15. More Examples
You walk into a Conference room or a shopping Mall with your PDA and your PDA is smart enough to collect and filter the public profiles of other people that are passing nearby
Of course other people should also have smart PDAs.
The cows in a village are equipped with GPS and GPRS devices and they are monitored from a central location on a digital map.
No need for a person to guide and feed them
You can find countless examples
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16. How to realize Ubiquitous Computing
Small and different size computing and communication devices
Tabs, pads, boards
PDAs, Handhelds, Laptops, Cell-phones
A communication network to support this
Anywhere, anytime access
Seamless, wireless and mobile access
Need for Personal Communication Services (PCS)
Ubiquitous Applications
New software
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29. What is Mobility
Initially Internet and Telephone Networks is designed assuming the user terminals are static
No change of location during a call/connection
A user terminals accesses the network always from a fixed location
Mobility and portability
Portability means changing point of attachment to the network offline
Mobility means changing point of attachment to the network online
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30. Degrees of Mobility Walking Users Vehicles Low speed
Small roaming area
Usually uses high-bandwith/low-latency access
Vehicles
High speeds
Large roaming area
Usually uses low-bandwidth/high-latency access
Uses sophisticated terminal equipment (cell phones)
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31. What is Mobile Computing
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33. Definitions – Mobile Computing
What is mobile computing?
Computing that is not obstructed while the location of it changes
Mobile computing = ?
Mobile computing draws from
Wireless communications and networking
Ability to communicate via wireless links
Ubiquitous and pervasive computing
Ability to provide computing anywhere and anytime (ubiquitous), usually in a seamless manner, potentially not perceived (pervasive)
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34. Introduction
Mobile computing is a form of human– computer interaction by which a computer is expected to be transported during normal usage.
Mobile computing has three aspects:
mobile communication
mobile hardware
mobile software
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35. Mobile communication
The first aspect addresses communication issues in ad-hoc and infrastructure networks as well as communication properties, protocols etc
Mobile hardware
The second aspect is on the hardware, e.g., mobile devices or device components.
Mobile software
The third aspect deals with the characteristics and requirements of mobile applications.
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37. Characteristics of Mobile Computing
Fixed and wired:
Typical LAN
Mobile and wired:
Wi-Fi
Fixed and wireless:
This mode is used for installing networks, e.g., in historical buildings to avoid damage by installing wires, or at trade shows to ensure fast network setup.
Mobile and wireless:
GSM and Wi Max
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38. APPLICATIONS OF MOBILE COMPUTING
Vehicles
Music, news, road conditions, weather reports, and other broadcast information are received via digital audio broadcasting (DAB) with 1.5 Mbit/s.
For personal communication, a universal mobile telecommunications system (UMTS) phone might be available offering voice and data connectivity with 384 kbit/s.
The current position of the car is determined via the global positioning system (GPS).
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39. Cars driving in the same area build a local ad- hoc network for the fast exchange of information in emergency situations or to help each other keep a safe distance.
In case of an accident, not only will the airbag be triggered, but the police and ambulance service will be informed via an emergency call to a service provider.
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40. Emergencies
An ambulance with a high-quality wireless connection to a hospital can carry vital information about injured persons to the hospital from the scene of the accident.
Wireless networks are the only means of communication in the case of natural disasters such as hurricanes or earthquakes.
In the worst cases, only decentralized, wireless ad-hoc networks survive.
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41. Credit Card Verification:
At Point of Sale (POS) terminals in shops and supermarkets, when customers use credit cards for transactions, the intercommunication required between the bank central computer and the POS terminal, in order to effect verification of the card usage, can take place quickly and securely over cellular channels using a mobile computer unit.
This can speed up the transaction process and relieve congestion at the POS terminals.
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42. Replacement of Wired Networks
wireless networks can also be used to replace wired networks, e.g., remote sensors, for tradeshows, or in historic buildings.
Due to economic reasons, it is often impossible to wire remote sensors for weather forecasts, earthquake detection, or to provide environmental information.
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43. Infotainment
wireless networks can provide up-to-date information at any appropriate location.
Another growing field of wireless network applications lies in entertainment and games to enable, e.g., ad-hoc gaming networks as soon as people meet to play together.
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44. Limitations of Mobile Computing
Resource constraints: Battery
Interference: Radio transmission cannot be protected against interference using shielding and result in higher loss rates for transmitted data or higher bit error rates respectively
Bandwidth: Although they are continuously increasing, transmission rates are still very low for wireless devices compared to desktop systems. Researchers look for more efficient communication protocols with low overhead.
Dynamic changes in communication environment: variations in signal power within a region, thus link delays and connection losses
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45. Interoperability issues: the varying protocol standards
Security constraints: Not only can portable devices be stolen more easily, but the radio interface is also prone to the dangers of eavesdropping. Wireless access must always include encryption, authentication, and other security mechanisms that must be efficient and simple to use.
Network Issues: discovery of the connection- service to destination and connection stability
Interoperability issues: the varying protocol standards
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46. A simplified reference model
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47. Wireless Standards
Different methods and standards of wireless communication have developed across the world, based on various commercially driven requirements.
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48. The table below summarizes the different 802.11 standards:
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50. Metropolitan Area Network (MAN)
Wireless Metropolitan Area Network (MAN) is the name trademarked by the IEEE Working Group on Broadband Wireless Access Standards for its wireless metropolitan area network standard (commercially known as WiMAX), which defines broadband Internet access from fixed or mobile devices via antennas.
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52. WiMAX
 WiMAX is defined as Worldwide Interoperability for Microwave Access by the WiMAX Forum, formed in June 2001 to promote conformance and interoperability of the IEEE standard, officially known as WirelessMAN.
The Forum describes WiMAX as "a standards- based technology enabling the delivery of last mile wireless broadband access as an alternative to cable and DSL".
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54. Evolution of Mobile Computing
Mobility
Identity authentication
Pervasive identity data
Intelligent Data Services
Games and the 'intelligent home'
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55. Compare AOC and SOC Client
Mobile technology can be implemented with :
Sometimes On Connectivity (SOC) to mobile devices
Always On Connectivity (AOC).
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56. BSI Consulting coined SOC and AOC terminology in order to effectively describe to our clients the communications frequency and performance: capabilities of alternatives for mobile computing solutions.
SOC clients can work effectively in a disconnected mode and take advantage of wireless or wired connections when they are available while AOC clients must be connected all or most of the time to be effective.
SOC client technology typically requires a Pocket PC or WinCE device in order to have sufficient processing power and data storage capability
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57. SOC clients have the ability to store large amounts of data on the mobile device and provide the user with a complete application solution even when the user does not have a wireless or wired data connection.
Data updates can occur when wireless, Internet dialup, network or desktop synchronization connections are available. Regardless of connectivity, productive work can proceed.
Data updates, when they do occur, can be fast bursts of small amounts of data rather than entire screen images that AOC clients employ..
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58. Mobile computing OS
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