Mobile and Sensor Systems
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(2) About Me.
(3) In this course. • The course will include aspects related to general understanding of . – Mobile and ubiquitous systems and networks. – Sensor systems and networks. 3 .
(4) List of Lectures. • Lecture 1: Introduction to Mobile Systems.. • Lecture 2: Mobile Medium Access Control and Wireless Systems.. • Lecture 3: Infrastructure, Ad-hoc and Delay Tolerant Mobile Networks.. • Lecture 4: Sensor Systems and MAC Layer Protocols.. • Lecture 5: Sensor Networking Routing Protocols.. • Lecture 6: Sensor Systems Reprogramming and Mobile Sensing.. • Lecture 7: Mobile Phone Sensing.. • Lecture 8: Practical: Mobile Phone Programming.. 4 .
(5) Teaching Material . • No required textbook.. • Some suggested readings:. – Schiller, J. (2003). Mobile communications. Pearson (2nd ed.). . – Karl, H. & Willig, A. (2005). Protocols and architectures for wireless sensor networks. Wiley. . – Agrawal, D. & Zheng, Q. (2006). Introduction to wireless and mobile systems. Thomson.. • Specific lectures will reference research papers which can be used for additional reading.. 5 .
(6) In this lecture. • We will describe mobile systems and their applications and challenges.. • We will start talking about wireless networks.. 6 .
(7) Smart Phones: the Computing Platform of the Future. 7 .
(8) Smart Phones: the Computing Platform. 8 .
(9) Some Numbers. • Number of worldwide mobile cellular subscribers increased from 34 million in 1993 to nearly 5.5 million subscribers by 2011.. • The number of cellular subscribers surpasses the number of wired phone lines.. 9 .
(10) Source: The Economist 10 .
(11) Location-based Social Network Systems. 11 .
(12) Geographic Recommender Systems. Mirco Musolesi .
(13) 13 .
(14) Credit: CNet . 14 .
(15) Fundamental Challenges in Mobile Computing. • Mobile devices are resource-constrained.. • Mobile connectivity is highly variable in performance and reliability.. • Mobile devices are inherently less secure.. 15 .
(16) Mobile Devices are Inherently Resource Constrained. • Mobile devices rely on batteries. . • Energy consumption due to:. – Computation (CPU, co-processors). – Display. – Communication. – Sensing. • Energy-efficient algorithms are needed. . 16 .
(17) Mobile Devices are Inherently Resource Constrained. • Computational constraints. – But, for example, in the Samsung Galaxy SIII you have1.4 GhZ quadcore Cortex A-9 +GPU. • Memory constraints. – But, for example, in the Samsung Galaxy SIII you have1GB or 2GB of RAM. 17 .
(18) Mobile Connectivity is Highly Variable in Performance and Reliability . • Various types of connectivity:. – Cellular (GSM, 3G, 4G, etc.). – WiFi. – Bluetooth. – Near Field Communication (NFC). – …. • Constraints related to:. – Coverage issues. – Trade-offs: energy consumption, throughput, costs. 18 .
(19) Mobile Devices are Inherently Less Secure . • Wireless not wired communication:. – Eavesdropping.. – Need for encrypted communication.. • Devices can be stolen:. – Devices might also be accessible by everyone (for example, sensors). . 19 .
(20) Ubiquitous and Mobile Computing. “The most profound technologies are those that disappear.”. Mark Weiser (1952-‐1999) . 20 .
(21) Copyright: PARC . Mirco Musolesi . 21 .
(22) Mirco Musolesi . 22 .
(23) Issues in Designing Mobile Computing Systems. • Distributed systems issues:. – Remote communication. – Fault tolerance. – Remote information access. – Distributed security. • Networking issues:. – Wireless communication. – Transport layer for wireless channel. 23 .
(24) Issues in Designing Mobile Computing Systems. • Databases issues:. – Disconnected operations. – Weak consistency . • Energy issues:. – Adaptation in terms of communication. – Intelligent uploading of data. – Hardware aspects. 24 .
(25) Issues in Designing Mobile Computing Systems. • HCI issues:. – Limited interface. – Interaction with the devices (input, etc.). – Ergonomics. • Privacy issues:. – Location sharing. – Activity recognition. • Security issues:. – Encrypted communication. 25 .
(26) Wireless and Mobile Networks. Background: . • Number of wireless (mobile) phone subscribers now exceeds number wired phone subscribers!. • Number of wireless Internet-connected devices soon to exceed number of wired Internet-connected devices. – laptops, Internet-enabled phones promise anytime Internet access. • Two important (but different) challenges. – wireless: communication over wireless link. – mobility: handling the mobile user who changes point of attachment to network. 26 .
(27) Elements of a wireless network. network infrastructure . wireless hosts v laptop, PDA, IP phone v run applicaQons v may be staQonary (non-‐ mobile) or mobile § wireless does not always mean mobility . 27 .
(28) Elements of a wireless network. network infrastructure . base staQon v typically connected to wired network v relay -‐ responsible for sending packets between wired network and wireless host(s) in its “area” § e.g., cell towers, 802.11 access points . 28 .
(29) Elements of a wireless network. network infrastructure . wireless link v typically used to connect mobile(s) to base staQon v also used as backbone link v mulQple access protocol coordinates link access v various data rates, transmission distance . 29 .
(30) Characteristics of selected wireless link standards. Data rate (Mbps). 200 54 5-11. 802.11n 802.11a,g 802.11b. 4 1. 802.11a,g point-to-point. data. 802.16 (WiMAX) UMTS/WCDMA-HSPDA, CDMA2000-1xEVDO. 3G cellular enhanced. 802.15. .384. 3G. UMTS/WCDMA, CDMA2000. .056. 2G. IS-95, CDMA, GSM. Indoor. Outdoor. 10-30m. 50-200m. Mid-range outdoor. Long-range outdoor. 200m – 4 Km. 5Km – 20 Km 30 .
(31) Elements of a wireless network. network infrastructure . infrastructure mode v base staQon connects mobiles into wired network v handoff: mobile changes base staQon providing connecQon into wired network . 31 .
(32) Elements of a wireless network. ad hoc mode v no base staQons v nodes can only transmit to other nodes within link coverage v nodes organize themselves into a network: route among themselves . 32 .
(33) Wireless network taxonomy. single hop infrastructure (e.g., APs) . no infrastructure . host connects to base staQon (WiFi, WiMAX, cellular) which connects to larger Internet no base staQon, no connecQon to larger Internet (Bluetooth, ad hoc nets) . mulQple hops host may have to relay through several wireless nodes to connect to larger Internet: mesh net no base staQon, no connecQon to larger Internet. May have to relay to reach other a given wireless node MANET, VANET . 33 .
(34) Suggested Readings. • Mark Weiser. The Computer for the 21th Century. Scientific American. September 1991.. • Mark Weiser. Some Computer Issues in Ubiquitous Computing. Communications of the ACM.Vol. 36. Issue 7. July 1993.. • M. Satyanarayanan. Pervasive Computing: Vision and Challenges. IEEE Personal Communications. Vol. 8 Issue 4. August 2001.. • Chapter 6 of James F. Kurose and Keith W. Ross. Computer Networking. A Top Down Approach. 6th Edition. Pearson 2012.. 34 .
(35) Acks . • Some material for the slides of this course has been contributed by:. • Dr Christos Efstratiou, . • Dr Nicholas Lane, . • Dr Mirco Musolesi,. • Dr Sarfraz Nawaz.. 35 .
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