1. University of Turkish Aeronautical Association Computer Engineering Department CENG 453 Mobile Computing Tansel Dökeroglu, Ph.D. tdokeroglu@thk.edu.tr Room 169 1

2. 2 Books

3. 3 Android Books

4. Mobile Computing Mobile computing refers to computing in a distributed system in which some processes or processors can move. –Moving processes  logical mobility, realized by agents. –Moving processors  physical mobility, realized by moving devices. Mobile computing extends a distributed computing environment with a new dimension of mobility. –Most existing mobile computing systems are based on client- server computing systems. –Recent mobile computing solutions consider general distributed computing, namely, peer-to-peer computing environments. –Mobility generalizes the network reconfiguration problem. Many mobile computing techniques have their root in distributed systems. 4

5. Mobile Computing vs. Others Mobile computing relies on wireless networking and communications and extends distributed computing –new issues of client movement, location management and context-awareness, not to mention the limitations of devices. Pervasive computing extends mobile computing, making use of small equipment and sensors. –The number of devices and volume of data can increase several orders of magnitude –new issues like data streaming need to be handled. 5

6. Mobile Computing vs. Others Networking is the base layer, with communication primitives. Wireless networking and communications extends networking protocols to cover lack of link and movement of devices –GPRS, 3G, IPv6, WLAN. Distributed computing covers fundamental issues to utilize computers over a network. –coordination mechanism to make the solutions work –general problem solving approaches Internet computing is more on the practical issues of developing programs and applications that work over internet. –using Java and related technology. –can be considered a case of distributed computing. 6

7. Mobile Computing is Taking a computer and all necessary files and software out into the field. Being able to use a computing device even when being mobile and therefore changing location. Portability is one aspect of mobile computing. The ability to use computing capability without a pre- defined location and/or connection to a network to publish and/or subscribe to information. A variety of wireless devices that has the mobility to allow people to connect to the internet, providing wireless transmission to access data and information from wherever location they may be. 7

8. The Era of “Mobile Computing” 8 Mobile Computing Mobile/Wireless Network

9. GSM Base Stations Nokia PrimeSite Ericsson RBS 2000 1997 9

10. Motorola Marco 1995 Specs Newton OS 1.3 4MB ROM 687KB Flash RAM 320x240 Monochrome LCD resistive touchscreen RS422 serial port Localtalk support 1 PCMCIA Slot (5V or 12V) 1 Sharp ASK infrared port 4 AA batteries, rechargeable NiCd batteries First released January 1995 It weighs 1.8 pounds and is 7.5 inches high, 5.8 inches wide and 1.4 inches deep USD 900-1400 10

11. The Nokia 9000 Communicator 1996 11

12. Laptops, Notebook, Sub Notebooks & Netbooks Laptops: 1991 Notebooks: 1996 Netbooks: 2006 12

13. Wearable Computers 13 Oculus Virtul Reality

14. Wireless Helmet? 14

15. The Projection Keyboard 15

16. Today The iphone Plastic Logic QUE 22Moo MyVu Portable projectors Andriod The iPad 16

17. Tablet 2010 2010-2011 17

18. 18 Sensors

19. Burada 19

20. 20 Sensors

21. 21 Accelerometers An accelerometer is a device that measures proper acceleration ("g-force").

22. 22 Accelerometers have multiple applications in industry and science. Highly sensitive accelerometers are components of inertial navigation systems for aircraft and missiles. Accelerometers are used to detect and monitor vibration in rotating machinery. Accelerometers are used in tablet computers and digital cameras so that images on screens are always displayed upright. Accelerometers are used in drones for flight stabilisation. Pairs of accelerometers extended over a region of space can be used to detect differences (gradients) in the proper accelerations of frames of references associated with those points. Accelerometers

23. 23 Hardware side of a typical smart phone

24. 24 Software side of a typical smart phone The bootrom (called "SecureROM" by Apple) is the first significant code that runs on an iDevice.

25. Firmware 25 In electronic systems and computing, firmware is a type of software that provides control, monitoring and data manipulation of engineered products and systems. Typical examples of devices containing firmware are embedded systems (such as traffic lights, consumer appliances, and digital watches), computers, computer peripherals, mobile phones, and digital cameras. The firmware contained in these devices provides the low-level control program for the device. A remote control is a very simple example of an engineered product that contains firmware. The firmware monitors the buttons, controls the LEDs, and processes the button presses in order to send data in a format the receiving device (a TV set, for example) can understand and process.

26. 26 Properties of a typical smart phone

27. 27 Properties of a typical smart phone

28. Mobile Computing Motivations –Availability of wireless network at reducing communication cost. –Widespread use of handheld devices with increasing computing power and lower cost. –Integration of communication and computing devices (Tablet computer, SmartPhones). –Detection of the physical or logical location of a device. –Making use of wireless network to access information and perform data processing, resource sharing at high capacity servers. –Extend the ability and usefulness of handheld devices. Goal –Access to information anywhere, anytime, anyway. 28

29. Mobile Computing vs. others Related concepts –Wireless computing computing without a wire. the most primitive form, e.g. using 802.11b, 802.11g or bluetooth. –Nomadic computing computing on the move. clients or users are moving. physically mobile computing, perhaps prolonged disconnection. –Ubiquitous computing invisible computing or subconscious computing. computers and their functionality available to users without being noticed. –Pervasive computing immersive computing (virtual reality). use of wearable computers. a current name for ubiquitous computing. 29

30. Mobile Computing vs. Others built upon distributed computing discipline closely related to –networking and wireless communications, –internet computing and cloud computing, –pervasive computing. 30

31. 31 also called ubiquitous computing is the growing trend towards embedding microprocessors in everyday objects so they can communicate information. The words pervasive and ubiquitous mean "existing everywhere." Pervasive computing devices are completely connected and constantly available. Pervasive computing

32. Pervasive Computing Industry revolution vs information revolution 32

33. Pervasive Computing Devices

34. Pervasive Computing Principles –Decentralization based on distributed systems. with information synchronization. devices and applications are embedded into wireless networking infrastructure. –Diversification should target on different users with different needs. must be able to manage the diversity. –Connectivity boundless connectivity. –Simplicity convenient and intuitive to use. good and mature human computer interface. 34

35. Pervasive Computing The wearable computer project MicroOptical display IR tag reader Body bus junction 802.11 bridge Internet appliance Battery Body network hub single Board computer 35

36. 36 Fueled by advances in mobile computing, wearable robotics are growing more sophisticated and finding use in medicine, manufacturing, and the military. The engineers behind the suit had developed a system that appears to read the brain’s intentions courtesy of electroencephalographic, or EEG, sensors

37. Distributed Systems A distributed system is a system supporting distributed computing. There is no universal definition. It is generally a collection of autonomous computers, connected together by some communication media, usually a network. They are capable of sharing resources and capable of providing service for one another. The processors cooperate to achieve an overall goal. Users may view the resulting environment as a single computing facility. 37

38. Distributed Systems Distributed hardware –Processors and memory are physically separated, connected only via communication media. Distributed control –Each processor is autonomous, running its own program. –They cooperate together in a voluntary manner. Distributed data –Data for a program may scatter around and need to be exchanged to carry out a task. Resource sharing –Expensive resources can be shared among different users. 38

39. Distributed Systems Openness –System is visible to user, and can be modified and extended when needs arise. –For example, Unix is an open system and IBM PC has an open architecture. Concurrency –Processors are autonomous and running concurrently. –Several jobs may be executed simultaneously. Scalability –It is relatively easy to build a large system using similar approach to build a small system. –For example, Internet is built from smaller networks. 39

40. Distributed Systems Fault tolerance –Processors more available (high availability), independent failure mode and preferably graceful degradation. –System can still function when some parts are down. Transparency –User should not perceive the system as being composed of different parts and the lower level of functionality must be concealed. –For example, send/receive using a socket should not be concerned with data link and network connections. –Forms of transparency include access, location, concurrency, replication, failure, migration, performance, scaling. 40

41. New Features in Mobile Computing Limited asymmetric bandwidth and high latency –Wireless channels are of limited bandwidth and asymmetric. –Perhaps of speed of grade of modems. Weak connectivity and low reliability –Disconnection to channels can easily occur (planned or unplanned) and can be prolonged. –Messages may be lost with much higher probability. Low processing power and energy –Battery is expensive and limited. –Screen or display is small. Mobility of devices –Need to track location of devices and to provide proper services. –Invalidation to data upon change of location. Low physical security –Mobile devices are easily lost, broken or stolen. High degree of heterogeneity –Devices are very different in nature, e.g., Palm and Pocket PC are programmed differently, worse for embedded systems and devices. 41

42. Objectives of Mobile Computing To run existing distributed applications To provide distributed services To share data and resources To maintain efficiency To keep communication and operational cost down To conserve energy To achieve consistency among views of different users To be scalable in supporting numerous users 42

43. New Solutions to Old Problems Solve problems in distributed systems –Hardware and computer architecture –Communication architecture and protocols –Distributed operating systems –Synchronization need –File systems –Databases systems –Real-time processing –Multimedia support with QoS –Dynamic system reconfiguration –Security –Application requirement and design –User interfaces design (on mobile devices) 43

44. Mobile Computing Architecture Fixed network can be dedicated special network for the mobile system. Fixed network can also be the Internet or Intranet. Infrastructured Systems –MSS (mobile support station, or base station) + –MU (Mobile unit, mobile station, mobile client) –WLAN, Cellular Net., etc. Ad hoc systems –Mobile nodes + mobile nodes –Mobile Adhoc NETwork (MANET), WSN (Wireless Sensor Network), VANET (Vehicular Ad Hoc Networks), etc. 44

45. VANETs (Vehicular Ad Hoc Networks) Like MANETs: –They self-organize over an evolving topology –They may rely on multi-hop communications –They can work without the support of a fixed infrastructure Unlike MANETs: –They have been conceived for a different set of applications –They move at higher speeds (0-40 m/s) –They do not have battery and storage constraints 45

46. VANETs Communication modes: –Vehicle-to-Vehicle (V2V) among vehicles –Vehicle-to-Infrastructure (V2I), between vehicles and Road-Side Units (RSUs) –Vehicle-to-X (V2X), mixed V2V-V2I approach V2V V2I V2V V2I RSU 46

47. Mobile Computing Architecture 47 Server MU (mobile unit) MSS (mobile support station) Fixed network Wireless radio cell (19.2Kbps) WLAN

48. Mobile Computing Architecture 48

49. Mobile Applications Personal applications –Web and email access. –Personal information management. –Personalized use of computer resources. –Weather and traffic report. –Network games. Commercial applications –Stock price quotation. –Inventory control for traveling salesperson. –Banking activities. –Bus-stop information kiosk at major bus terminals. –Push-based advertisement on vehicle. –e-coupon. –Generic M-commerce applications. finance e-commerce/finance finance logistics/tourism tourism e-commerce/tourism e-commerce personal/tourism personal 49

50. 50 Radio-frequency identification (RFID) is the wireless use of electromagnetic fields to transfer data, for the purposes of automatically identifying and tracking tags attached to objects.

51. Location Tracking Active badge/RFID card with sensor technology –An early application of sensor technology in location tracking, developed by AT&T Cambridge Lab, for tracking and locating of individuals within a building. –Each building office is equipped with one or more networked sensors to detect these transmission signals. Biometrics cards with bluetooth and RFID deployed at US Homeland Security Office May 2005. –Requirement: strong resistance to terrorist exploitation and rapid electronic authentication. –Could Hong Kong smart ID do that? –Problem: signal could be detected. 51

52. Location-Awareness Location and mobility are the two major factors to be capitalized in a mobile application. Applications can be based on the current location of a user. Example –Emergency vehicle routing to caller of 999. –Deliver me a pizza as I am hungry! –Deliver value-added information based on current position. –Logistics arrangement can be made based on location. Send the goods to an alternative location if traffic jam is out-of- control for receiving the goods. 52

53. Context-Awareness Context vs. Location? A context-aware application is an application that adapts its behavior to a changing environment. It needs to gather contextual information about its environment, usually through the use of sensors. User does not need to give all information and the application should try to figure out the rest. The follow-me type of applications: –Application knows the location of a user: Smart map (Telenor Research) that always maintain the current user position at center. Nearest restroom/toilet depends on gender. –When in a room, system can look up user profile for preferred room setting, or mode of operation for a speaker. 53

54. Intelligent Home Intelligent home networking system with general technology –Use mobile phone technology to instruct a home control computer for home automation equipment. WiMAX (802.16), 802.11, Bluetooth etc. Transmit signal and control electronic devices via power line. Smart TV 54

55. Intelligent Home 55

56. 56 Master here

57. 57 Intelligent Home

58. Applications of Mobile Computing Instant messaging? –10 million iMode users in Japan since 18 months of introduction, also used by Greece Olympics. –15.6 billion SMS messages in China January 2004. Mobile games? –$9 billion sold in 2004. Mobile web access? –WAP, iMode, WWW –How to resolve the bandwidth problem? 3G?4G? Location-dependent services? –Sensor network infrastructure cost? Context-aware services? –Locating a best restaurant closest by sensing e-cash in e-wallet and dining preference. How can the communication infrastructure match with the application functionality and bandwidth / mobility requirement? –High bandwidth can be resulted, using pico-cells, but the client movement speed must be limited. 58

59. Bandwidth Requirement 3G current Ethernet wireless LAN 59

60. 60 Asynchronous Transfer Mode (ATM) is "a telecommunications concept defined by ANSI and ITU standards for carriage of a complete range of user traffic, including voice, data, and video signals". ATM was developed to meet the needs of the Broadband Integrated Services Digital Network (ISDN), as defined in the late 1980s, and designed to unify telecommunication and computer networks. Asynchronous Transfer Mode

61. 61 It was designed for a network that must handle both traditional high-throughput data traffic (e.g., file transfers), and real-time, low-latency content such as voice and video. The reference model for ATM approximately maps to the three lowest layers of the ISO-OSI reference model: network layer, data link layer, and physical layer. ATM is a core protocol used over the backbone of  The public switched telephone network (PSTN) and  Integrated Services Digital Network (ISDN) Asynchronous Transfer Mode

62. 62 is a family of wireless communications standards initially designed to provide 30 to 40 megabit-per- second data rates, with the 2011 update providing up to 1 Gbit/s for fixed stations. The name "WiMAX" was created by the WiMAX Forum, which was formed in June 2001 to promote conformity and interoperability of the standard. 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". WiMAX (Worldwide Interoperability for Microwave Access)

63. 2009 63 Smartphone OS Market Share

64. 64 Smartphone Operating System Market Share The largest shareholder is the Android Operating System

65. 65 Smartphone OS Market Share

66. 66 Android 6.0 Marshmallow

67. 67 is a Java platform designed for embedded systems (mobile devices are one kind of such systems). Target devices range from industrial controls to mobile phones (especially feature phones) and set-top boxes. Java ME was formerly known as Java 2 Platform, Micro Edition (J2ME). Dalvik is a process Virtual Machine (VM) in Google's Android operating system that executes applications written for Android. Dalvik is used on mobile devices and more recently on devices such as smart TVs and weRbles. Java Platform, Micro Edition, or Java ME,

68. 68 Objective-C Objective-C is a general-purpose, object-oriented programming language that adds Smalltalk-style messaging to the C programming language. It is the main programming language used by Apple for the OS X and iOS operating systems, and their respective application programming interfaces (APIs): Cocoa and Cocoa Touch.AppleOS XiOS

69. New Forms of Computing Wireless Computing Nomadic Computing Mobile Computing Ubiquitous Computing Pervasive Computing Invisible Computing Distributed Computing (Client/Server) 69

70. Mobile Computing Using: –small size portable computers, hand-helds, and other small wearable devices, To run stand-alone applications (or access remote applications) via: –wireless networks: IR, BlueTooth, W-LANs, Cellular, W- Packet Data networks, etc. By : –nomadic and mobile users (animals, agents, trains, cars, cell phones, ….) 70

71. Nomadic, Mobile & Ubiquitous No Network Mobile ComputingNomadic Computing Wireless Network (B) Fixed Network Wireless Network (A) Fixed Wireless Network Ubiquitous Computing 71

72. Impressive Wireless Infrastructure! Satellite Macro-Cell Micro-Cell Urban In-Building Pico-Cell Global Suburban dik © In-Room (BlueTooth) 72

73. Wireless Network Convergence 2G/3G Mobility-Bandwidth Trade-off Mobility Bandwidth 10K 100K 1M 10M 100M 1G Room GlobalGSM D-AMPS/IS-95 DECT WLAN UMTS National Regional Metropolitan Campus Office 1-7 GHz 0.1-2 GHz 0.1-2.3 GHz 2-4 GHz 2-7 GHz >2 GHz 20-50 GHz 73

74. UMTS: Universal Mobile Telecomm. Standard Global seamless operation in multi-cell environment (SAT, macro, micro, pico) Global roaming: multi-mode, multi-band, low-cost terminal, portable services & QoS High data rates at different mobile speeds: 144kbps at vehicular speed (80km/h), 384 kbps at pedestrian speed, and 2Mbps indoor (office/home) Multimedia interface to the internet Based on core GSM. 74

75. Wireless Network Overlay Satellite Macro-Cell Micro-Cell Urban In-Building Pico-Cell Global Suburban dik © 75

76. Beneficiaries of Ubiquitous Computing Commuters Travelers Stock traders Medical Law enforcement Package delivery Education Insurance Emergency Trucking Intelligence Military Clients Adhoc network Servers Intranet Internet 76

77. Limitations of the Mobile Environment  Limitations of the Wireless Network  heterogeneity of fragmented networks  frequent disconnections  limited communication bandwidth  Limitations Imposed by Mobility  Limitations of the Mobile Computer 77

78. Frequent Disconnections  Handoff blank out (>1ms for most cellulars)  Drained battery disconnection  Battery recharge down time  Voluntary disconnection (turned off to preserve battery power, also off overnight)  Theft and damage (hostile environment)  Roam-off disconnections 78

79. Limited Communication Bandwidth  Orders of magnitude slower than fixed network  Higher transmission bit error rates (BER)  Uncontrolled cell population  Difficult to ensure Quality of Service (QoS)  Availability issues (admission control)  Asymmetric duplex bandwidth  Limited communication bandwidth exacerbates the limitation of battery lifetime. 79

80. Limitations of the Mobile Computer  Short battery lifetime (max ~ 5 hours)  Subject to theft and destruction => unreliable  Highly unavailable (normally powered-off to conserve battery)  Limited capability (display, memory, input devices, and disk space)  Lack of de-facto general architecture: hand- helds, communicators, laptops, and other devices 80

81. Limitations Imposed by Mobility  Lack of mobility-awareness by applications  inherently transparent programming model (object-, components-oriented, but not aspect-oriented)  lack of environment test and set API support  Lack of mobility-awareness by the system  network: existing transport protocols are inefficient to use across heterogeneous mix of fixed/wireless networks  session and presentation: inappropriate for the wireless environment and for mobility  operating systems: lack of env. related conditions and signals  client/server: unless changed, inappropriate and inefficient 81

82. Evolution of Wireless LAN In late 1980s, vendors started offering wireless products, which were to substitute the traditional wired LAN (Local Area Network) products. The idea was to use a wireless local area network to avoid the cost of installing LAN cabling and ease the task of relocation or otherwise modifying the network's structure. 82

83. Evolution of Wireless LAN The question of interoperability between different wireless LAN products became critical. IEEE standard committee took the responsibility to form the standard for WLAN. As a result IEEE 802.11 series of standards emerged. 83

84. Evolution of Wireless LAN WLAN uses the unlicensed Industrial, Scientific, and Medical (ISM) band that different products can use as long as they comply with certain regulatory rules WLAN is also known as Wireless Fidelity or WiFi in short There are many products which use these unlicensed bands along with WLAN. 84

85. Evolution of Wireless LAN Examples could be cordless telephone, microwave oven etc. There are 3 bands within the ISM bands. –These are 900-MHz ISM band, which ranges from 902 to 928 MHz; –2.4-GHz ISM band, which ranges from 2.4 to 2.4853 GHz; and –the 5.4 GHz band, which range from 5.275 to 5.85 GHz. WLAN uses 2.4 GHz and 5.4 GHz bands. WLAN works both in infrastructure mode and ad hoc mode 85

86. Evolution of Wireless PAN Techniques for WPANs are infrared and radio waves. Most of the Laptop computers support communication through infrared, for which standards have been formulated by IrDA (Infrared Data Association- www.irda.org). Through WPAN, a PC can communicate with another IrDA device like another PC or a Personal Digital Assistant (PDA) or a Cellular phone. 86

87. Evolution of Wireless PAN The other best known PAN technology standard is Bluetooth. Bluetooth uses radio instead of infrared. It offers a peak over the air speed of about 1 Mbps over a short range of about 10 meters. The advantage of radio wave is that unlike infrared it does not need a line of sight. WPAN works in ad hoc mode only 87

88. Mobile computing Mobile computing can be defined as a computing environment over physical mobility. The user of a mobile computing environment will be able to access data, information or other logical objects from any device in any network while on the move. 88

89. Mobile computing Mobile computing system allows a user to perform a task from anywhere using a computing device in the public (the Web), corporate (business information) and personal information spaces (medical record, address book). 89

90. Mobile computing Mobile computing is used in different contexts with different names. The most common names are: – Mobile Computing: The computing environment is mobile and moves along with the user. This is similar to the telephone number of a GSM (Global System for Mobile communication) phone, which moves with the phone.GSM The offline (local) and real-time (remote) computing environment will move with the user. In real-time mode user will be able to use all his remote data and services online. 90

91. Mobile computing –Anywhere, Anytime Information: This is the generic definition of ubiquity, where the information is available anywhere, all the time. –Virtual Home Environment: (VHE) is defined as an environment in a foreign network such that the mobile users can experience the same computing experience as they have in their home or corporate computing environment. For example, one would like to put ones room heater on when one is about 15 minutes away from home. 91

92. Mobile computing –Nomadic Computing: The computing environment is nomadic and moves along with the mobile user. This is true for both local and remote services. –Pervasive Computing: A computing environment, which is pervasive in nature and can be made available in any environment. –Ubiquitous Computing: A disappearing (nobody will notice its presence) everyplace computing environment. User will be able to use both local and remote services. 92

93. Mobile computing –Global Service Portability: Making a service portable and available in every environment. Any service of any environment will be available globally. –Wearable Computers: Wearable computers are those computers that may be adorned by humans like a hat, shoe or clothes (these are wearable accessories). 93

94. Mobile Computing Functions We can define a computing environment as mobile if it supports one or more of the following characteristics: User Mobility: –User should be able to move from one physical location to another location and use the same service. –The service could be in the home network or a remote network. –Example could be a user moves from London to New York and uses Internet to access the corporate application the same way the user uses in the home office. 94

95. Mobile Computing Functions Network Mobility: –User should be able to move from one network to another network and use the same service. –Example could be a user moves from Hong Kong to New Delhi and uses the same GSM phone to access the corporate application through WAP (Wireless Application Protocol). In home network he uses this service over GPRS (General Packet Radio Service) whereas in Delhi he accesses it over the GSM network. 95

96. Mobile Computing Functions Bearer Mobility: –User should be able to move from one bearer to another and use the same service. –Example could be a user was using a service through WAP bearer in his home network in Bangalore. He moves to Coimbatore, where WAP is not supported, he switch over to voice or SMS(Short Message Service) bearer to access the same application. 96

97. Mobile Computing Functions Device Mobility: –User should be able to move from one device to another and use the same service. –Example could be sales representatives using their desktop computer in home office. During the day while they are on the street they would like to use their Palmtop to access the application. 97

98. Mobile Computing Functions Session Mobility: –A user session should be able to move from one user-agent environment to another. –Example could be a user was using his service through a CDMA (Code Division Multiple Access) IX network. The user entered into the basement to park the car and got disconnected from his CDMA network. User goes to home office and starts using the desktop. The unfinished session in the CDMA device moves from the mobile device to the desktop computer. 98

99. Mobile Computing Functions Service Mobility: –User should be able to move from one service to another. –Example could be a user is writing a mail. To complete the mail user needs to refer to some other information. In a desktop PC, user simply opens another service (browser) and moves between them using the task bar. User should be able to switch amongst services in small footprint wireless devices like in the desktop. 99

100. Mobile Computing Functions Host Mobility: –The user device can be either a client or server. –When it is a server or host, some of the complexities change. –In case of host mobility the mobility of IP needs to be taken care of. 100

101. Logical Functions of Mobile Computing The mobile computing functions can be logically divided into following major segments: 1.User with device: The user device, this could be a fixed device like desktop computer in office or a portable device like mobile phone. Example: laptop computers, desktop computers, fixed telephone, mobile phones, digital TV with set-top box, palmtop computers, pocket PCs, two way pagers, handheld terminals, etc. 101

102. Logical Functions of Mobile Computing 2.Network: Whenever a user is mobile, he will be using different networks at different places at different time. Example: GSM, CDMA, iMode, Ethernet, Wireless LAN, Bluetooth etc. 102

103. Logical Functions of Mobile Computing 3.Gateway: This is required to interface different transport bearers. These gateways convert one specific transport bearer (transporter) to another transport bearer. Example: From a fixed phone (with voice interface) we access a service by pressing different keys on the telephone. 103

104. Logical Functions of Mobile Computing 4.Middleware: This is more of a function rather than a separate visible node. In the present, context middleware handles the presentation and rendering of the content on a particular device. It will also handle the security and personalization for different users 104

105. Logical Functions of Mobile Computing 5.Content: This is the domain where the origin server and content is. This could be an application, system, or even an aggregation of systems. The content can be mass market, personal or corporate content. Origin server will have some means to accessing the database and the storage devices 105