Mobile computing
- 2. History of mobile computing? By 2012 the number of mobile subscribers throughout the world will reach 5 Billion, of which close to 1.5 Billion will use wireless communicators (3G) as gateways to the Internet Oct 23, 2013 2
- 3. World wide Internet penetration rate increases rapidly. 25% of the world population access to the Internet by 2012, >1 billion of Internet users will use mobile as their only access means Oct 23, 2013 3
- 4. What is mobile computing? Today, access to information and computing services is necessary everywhere ◦ not only from our "home base," but also while we are traveling and when we reach a different location. Mobile computing ◦ Techniques that allow mobile users to use portable computing devices to run stand-alone applications and / or to access remote ones via wireless networks. Oct 23, 2013 4
- 5. Mobile computing = mobile + computing, another wave in computing evolution. ◦ Different kinds of mobility Terminal mobility: movement of processors / devices - caused by mobile devices. User mobility: movement of users – caused by traveling people. Logical mobility: movement of processes - caused by mobile codes. ◦ Different modes of computing Small office: take the service/application with users - computing is offline Home office: maintain the access to the same service/application at different places – computing is online Mobile office: move to different places and the service/application follows – computing is moving (follow-me) Oct 23, 2013 5
- 6. Evolution of computing paradigm Mainframe Client/Server Personal Computer Internet Mobile Internet Fixed Location Branch Office Remote Office Mobile Workplace Age of Centralized Computing Age of Distributed Computing Age of Personal Computing Age of Networked Computing Age of Mobile Computing 1960 1980 1990 2000 2003 2010 Unwired Enterprise Oct 23, 2013 6
- 7. Synonym of mobile computing Mobile computing often uses wireless and mobile networks as access technologies. ◦ Wireless and mobile networks extend networking capacity to cover the areas of lack of wired link and support movement of devices Wireless communication plays an important role in mobile computing. But, mobile computing does not necessarily mean wireless. Oct 23, 2013 7
- 8. Today’s applications Internet, Wireless Networks & Mobile Computing ◦ Mobile users use wireless communications to access to the Web information and services Provider Network WAP Terminal SQL Products WAP Gateway Merchant 1 Internet - WML pages - list of merchants SQL WAP / Agent Server SQL Merchant n Products
- 9. Corporations ◦ M-business / M-office (working remotely - job dispatch, calendar, email, workflow, etc) ◦ M-commerce (logistics, inventory control) Consumers ◦ M-commerce (shopping, banking, payment, etc) ◦ Mobile web access / mobile email / SMS ◦ Mobile P2P (file sharing, gaming, etc.) Government ◦ ◦ ◦ ◦ ◦ ◦ / Public services / Militaries M-healthcare (emergency with in-time patient condition info.) Transportation Tourism (navigation with maps, location-aware travel hints, etc) Intelligent home Environment monitoring Battle field communications Oct 23, 2013 9
- 10. Enabling factors Motivations and driving forces ◦ Increasing demands on access to information, communication, and cooperation anywhere, anytime, anyway. ◦ Technology reality may support such demands Increasing availability of wireless networks at reduced cost. Widespread use of handheld devices with increasing computing power and lower cost. Integration of communication and computing devices (PDA, iPhone, smart phone, intelligent sensor). Advances in techniques of detecting location of a device – location based services. Oct 23, 2013 10
- 11. Device Vision Mobile phones ◦ 1973: First cellphone call ◦ 2007: ~ 3.3 billion mobile phone subscribers ◦ 2009: ~ 4.6 billion Smart ◦ ◦ ◦ ◦ phones are mobile phones have operation systems can connect to the internet: web browsing, email, etc have advanced computing ability: send and receive text & multimedia messages (SMS, MMS), take pictures, etc
- 12. Mobile computing means more… Mobile computing is also closely related to Internet computing technologies ◦ Mobile computing uses Internet computing technologies The layered protocol stack and client/server paradigm ◦ Mobile computing allows the application not to connect the network all the time Mobile Internet, Wireless Internet HTTP client / server protocols => WAP XML, HTML => WML, XHTML J2SE/J2EE, .Net => J2ME/J2EE, .Net Mobile Oct 23, 2013 12
- 13. Forthcoming applications Example: Vehicle Networks transmission of news, road condition, traffic information, weather, music via DAB personal communication using mobile phone networks positioning via GPS local ad-hoc network with vehicles close-by to prevent accidents, report traffic jams, guidance system, etc vehicle data (e.g., from busses, high-speed trains) can be transmitted in advance for maintenance busses, trucks, and trains can transmit logistic information for, e.g., fleet management. UMTS, WLAN, GSM, cdma2000, DAB, ... ad oc h Personal Travel Assistant, DAB, PDA, laptop, GSM, UMTS, WLAN, Bluetooth, ...
- 14. What’s the future picture? Oct 23, 2013 14
- 15. Wireless: Convergence Oct 23, 2013 15
- 16. Challenges of mobile computing Where do the challenges come from? ◦ Distinct characteristics of mobile and wireless computing: Wireless communications Mobility Portability Oct 23, 2013 16
- 17. Challenges Wired channel ◦ Wired channel can be easily engineered Too many noises? – use shell to protect against electromagnetic noise Large signal attenuation? - use repeaters to amplify the signal Data rate too low? - upgrade to coaxial cable or optical fiber Low error rate - Good quality: 10-6; Optical fiber: 10-11 ~ 10-12 Wireless channel ◦ Wireless channel is hardly be engineered High background noises Signal strength fluctuates significantly Low data rate High error rate – Radio: 10-2 or worse Oct 23, 2013 17
- 18. Challenges Wired channel – what if more than one transmitter? Switching Center or Every user accesses the network by means of a dedicated channel Dedicated Channel New user is served by a new wired-line circuit Network Access Point Access capacity is guaranteed. Oct 23, 2013 18
- 19. Challenges Wireless channel – what happens? Sh are d Ch ann e Wireless users access the network by means of a shared channel l Access capacity is inherently limited. Base Station Oct 23, 2013 19
- 20. Mobility Different modes of mobility ◦ Personal mobility : reaching a mobile user using a logical identity, irrespective of what device he/she is using, current location in the network, or even which network he/she is located in ◦ Session mobility : maintaining access to the same network service / application at different places ◦ Service / application mobility : making a service/application available to mobile user when the user has moved to another location with other but similar resources (e.g., print using the nearest printer) – following me service Oct 23, 2013 20
- 21. Challenges Dynamic change of physical locations ◦ Mobile users may use their phones at different places Dynamic change of logical addresses ◦ Users may use their laptops to access different networks Frequent change of system configuration ◦ Mobile users may use PDAs with cellular networks when outdoor and with WLANs when indoor. Oct 23, 2013 21
- 22. Challenges Location dependency ◦ Location management problem: How does the network know where the intended recipient of a message is currently located? Cellular scenario Where is 97532468? Send broadcast messages from every base station.
- 23. Portability • Minimize power consumption - larger battery life, smaller battery size - lesser weight • Smaller user interface - handwriting, voice recognition, pens, virtual reality screens. • Small storage capacity - Compressed file systems
- 24. Topics in mobile computing Mobile computing models ◦ Mobile C/S Models ◦ Simple C/S model, Client/Agent/Server model, Client/Intercept/Server model Mobile Peer-to-Peer Model Mobile hosts plays the same role and cooperate to ◦ Discover peers and resources Route query requests Perform specified tasks Mobile Agent Model Code mobility (with computation, data, and state) Autonomous and Asynchronous Oct 23, 2013 24
- 25. Topics in mobile computing Mobile C/S model ◦ C/S model can still be used in mobile environment - mobile hosts act as the clients requesting service from server located at fixed network. ◦ However, mobile C/S model deviates from the C/S model used for distributed system in several ways. ◦ Mobile C/S model cannot assume continuous network connectivity and powerful client ability RPC (Remote process control) is not suitable due to disconnection; Direct message exchange is not good neither due to weak connectivity and slow network. Need to decouple the communication in synchronous RPC; Use indirection with messages queued at the two ends.
- 26. Topics in mobile computing Mobile P2P model ◦ No central server, actually no difference between client and server: All nodes have the same role, serving as both server and client Relying on collaboration ◦ Completely decentralized & asynchronous operations ◦ Nodes can communicate with each other directly Oct 23, 2013 26
- 27. Topics in mobile computing Mobile agent (MA) model ◦ A MA is a “process on the move” – dispatched by one host, encapsulating a thread of execution along with a package of code, data, and execution state Executes at a host for a while, halts execution, dispatches itself to another host, and resumes execution there - all under its own control logi c logi c logi c mobile agent X Migrating mobile agent X mobile agent X Host A Oct 23, 2013 Host B 27
- 28. Topics in mobile computing Mobile agent features ◦ Mobility Actively travels across the network, carrying partial / intermediate results calculated at the previous host Not just alternative to message passing; can perform additional tasks along its way of traveling ◦ Autonomous Decides by itself what to do and how, when and where it ought to move ◦ Asynchrony Mobile agents and users can execute at the same time without blocking each other Oct 23, 2013 28
- 29. Summary Mobile computing systems have different constraints and hence different solutions. Main challenges are due to Wireless - unreliable. Mobility - dynamism of information. Portability - limited resources Resource list for further information on mobile computing. Oct 23, 2013 29
Editor's Notes
- #2: {}