1. CSE-302: Mobile Computing
Dr. R. B. Patel
Dr. R. B. Patel

2. Breakthrough Technology
Wireless communication networks
–       multiple networks “covering” the globe
–       world- wide deregulation and spectrum auctions
–       standard communication systems and air link interfaces
• Portable information appliances
–       laptops, notebooks, sub- notebooks, and MNCs
–       hand- held computers
–       PDAs and smart phones
• Internet:
–       TCP/ IP& de- facto application protocols
–       ubiquitous web content
Dr. R. B. Patel

3. New Forms of Computing Wireless Computing Nomadic Computing
Mobile Computing
Ubiquitous Computing
Pervasive Computing
Invisible Computing
Distributed Computing
(Client/ Server)
Dr. R. B. Patel

4. Mobile Computing Mobile Computing
• Using:– small size portable computers, handheld, MNC, and other small wearable devices,
• To run stand- alone or network based applications via:– wireless networks: IR, BlueTooth, W- LANs, Cellular,W- Packet Data networks, SAT, etc.
•By : – nomadic and mobile users (animals, agents, trains, cars, cell phones, ….)
Dr. R. B. Patel

5. Mobile Computing
An important question to ask is which technology drove mobile computing to where it is today?
Is it the wireless network technology or the miniaturization and portable computing technology?
Unfortunately, there is no easy answer. An individual with a Palm Pilot will probably answer in favor of the portable technology, whereas a UPS package delivery worker will be more thankful to the wireless technology.
Whatever the right answer might be, more important questions need to be answered: where are we now?
And what are the challenges and impediments facing mobile computing?
Dr. R. B. Patel

6. Mobile computing
Mobile computing represents a shift in the distributed systems paradigm.
The potential of decoupled and disconnected operation, location-dependent computation and communication, and powerful portable computing devices gives rise to opportunities for new patterns of distributed computation that require a revised view of distributed systems.
However, factors such as weak network connectivity, energy constraints, and mobility itself raise new concerns regarding the security, reliability, and even correct-ness of a mobile computing system.
Dr. R. B. Patel

7. Mobile Computing Migration is important for survival
Mobility originated from the desire to move either toward resource or away from scarcity
Mobile computing about both physical and logical computing entities that move
Physical entities are computers that change locations
Logical entities are instances of running user application or a mobile agent
Mobile agents can migrate any where over the Internet.
But applications can only move to a local cluster of computers
Dr. R. B. Patel

8. Buzzwords
Mobile, ubiquitous, nomadic, un-tethered (unsecured), pervasive and any time, any where, any person computing are used by the researchers to refer to computing that uses small portable devices and wireless communication network.
Nomadic computing refer to limited migration
Migration is within a building at a pedestrian speed
Interleaved pattern of user relocation and indoor connections
In the same vein, users carrying laptop with Dialup modems are engaged in nomadic computing
Dr. R. B. Patel

9. Buzzwords (contd...)
Mobile Computing requires: Wireless network to support outdoor mobility and handoff from one network to the next at a pedestrian or vehicular speed
Traveler in car using laptop connected with a GSM phone- engaged in mobile computing
Ubiquitous computing or pervasive computing refers to access to computer network all the time at any location by any person.
Ubiquitous computing cannot be realized unless mobile computing matures.
Dr. R. B. Patel

10. Ubiquitous Computing = Nomadic Computing + Mobile Computing
No Network
Fixed Network
Fixed Wireless Network
Wireless Network
(A)
(B)
Nomadic Computing
Mobile Computing
Ubiquitous computing
Dr. R. B. Patel

11. Nomadic computing
It is another name for mobile computing, is the use of portable computing devices (such as laptop and handheld computers) in conjunction with mobile communications technologies to enable users to access the Internet and data on their home or work computers from anywhere in the world.
People using such a system are sometimes referred to as technomads, and their ability to use that system as nomadicity.
Dr. R. B. Patel

12. Continued …
Nomadicity is the tendency of a person, or group of people, to move with relative frequency.
The need to support today's increasingly mobile workers with nomadic computing, the use of portable computing devices and, ideally, constant access to the Internet and data on other computers.
The goal of nomadic computing is to enable a consistent experience for users anywhere in the world, including as they travel from one place to another.
Dr. R. B. Patel

13. Continued …
A nomadic environment is said to be one that is transparent to the user, regardless of location, the device and platform they're using, the available bandwidth, and whether or not they are in motion at any given time.
Standards such as the Internet Engineering Task Force’s (IETF) Mobile IPv6 standards and Dynamic Host Configuration Protocol (DHCP) can be said to support nomadic computing.
Dr. R. B. Patel

14. Ubiquitous Computing
Ubiquitous computing names the third wave in computing, just now beginning.
First were mainframes, each shared by lots of people. Now we are in the personal computing era, person and machine staring uneasily at each other across the desktop.
Next comes ubiquitous computing, or the age of calm technology, when technology recedes into the background of our lives.
This is also called "Third Paradigm" computing.
Dr. R. B. Patel

15. Sentient computing
Sentient computing is a form of ubiquitous computing which uses sensors to perceive its environment and react accordingly.
A common use of the sensors is to construct a world model which allows location-aware or context-aware applications to be constructed.
Dr. R. B. Patel

16. High-speed wire-line network
Mobile Environment
High-speed wire-line network
Fixed host
Satellite link
Wireless radio Cells
Wireless LAN
Base station
Mobile host
Wireless link
Comm. cell
Dr. R. B. Patel

17. Wireless Telecommunication Networks
Dr. R. B. Patel

18. Emerging Portable Information Devices
The First Wrist PC: Ruputer
The Nokia 9000 Communicator
Subscriber Identification
Module (SIM)
Motorola marco
The Vadem Clio
The Power Ring
The Pocket PC
Motorola Envoy
Dr. R. B. Patel
The Sharp Zaurus
Fujitsu Stylistic 2300/ 3400
Japan’s PHS Phone, Year 2001
Wearable Computers

19. Applications for mobile computing
There are several applications for mobile computing including wireless remote access by travelers and commuters, point of sale, stock trading, medical emergency care, law enforcement, package delivery, education, insurance industry, disaster recovery and management, trucking industry, intelligence and military.
Most of these applications can be classified into: (1) wireless and mobile access to the Internet, (2) wireless and mobile access to private Intranets, and (3) wireless and adhocly mobile access between mobile computers.
Dr. R. B. Patel

20. Beneficiaries of ubiquitous computing
Commuters
Travelers
Stock traders
Medical
Law enforcement
Education
Insurance
Emergency
Trucking
Intelligence
Military
Internet
Intranet
Ad-hoc network
Servers
Clients
Dr. R. B. Patel

21. 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
Dr. R. B. Patel

22. Continued… Frequent Disconnections
– Handoff blank out (>1ms for most cellular system)
–  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
Dr. R. B. Patel

23. Continued… 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)
–       Asymmetric duplex bandwidth
–       Limited communication bandwidth exacerbates the limitation of battery lifetime.
Dr. R. B. Patel

24. Continued… 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: Handheld, communicators, laptops, and other devices
Dr. R. B. Patel

25. Continued… 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
Dr. R. B. Patel

26. Continued… 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 environment related conditions and signals
–       client/server: unless changed, inappropriate and inefficient
Dr. R. B. Patel

27. Continued… Mobile and Wireless Networking Issues – Mobile IP
–       Wireless Transport
–       Ad- Hoc Networks
–       Location Management
–       Wireless Network Benchmarking
–       Ad- Hoc Network Simulation
–       Wireless Link Simulation
Dr. R. B. Patel

28. Continued… Wireless and Mobile Computing Models
–       Mobility- aware Client/ Server using Proxies
–       Disconnected Operations
–       Application- aware Adaptations
–       Mobile Agents and Objects
–       Thin Client/ Server
–       Mobile Caching and Replication
–       Broadcast Disks
–       Service Advertisement and Brokering
–       Smart Pones
Dr. R. B. Patel

29. Continued… Mobile file and Database Systems
–       Wireless File System Access
–       Disconnected File Systems
–       Mobile Access to C/ S or Distributed Databases
–       Ad- Hoc Database Systems
–       Checkpointing
–       Database recovery
–       Mobile Database Design
Dr. R. B. Patel

30. Continued… Mobile Transaction and Workflow – ACID Relaxation
–       Mobile Transaction Models
–       Optimistic Data Replication
–       Semantic- based Conflict Resolution
–       Consensus in Mobile Environment
Dr. R. B. Patel

31. Continued… Wireless and Mobile Applications and Services
–       Application Design for Wireless networks
–       Application Design for Mobility
–       Wireless WWW Access
–       Active Badges (Teleporting)
–       Wireless Classroom (Wireless Campus!)
–       Mobile Groupware
–       Location- sensitive Yellow Service
–       Pervasive Computing and Smart spaces
–       •
Dr. R. B. Patel

32. Continued… Performance and QoS
–       QoS Measures in Wireless and Mobile Environments
–       QoS Guarantees
–       Simulators and Emulaors of Wireless Links
–       Simulators of Mobile and Ad- hoc Networks
–       Wireless Networking Benchmarking
Dr. R. B. Patel

33. Continued… Emerging Standards – The 802.11b – The BlueTooth Standard
–       The Wireless Application Protocol (WAP)
–       The CompactHTML
–       The Network Computer Reference Specification
–       Telecom Standards: UMTS
–       …
Dr. R. B. Patel

34. Continued… Commuters Travelers Stock traders Medical Law enforcement
Internet
Intranet
Education
Insurance
Emergency
Trucking
Intelligence
Military
Intranet
Ad-hoc network
Clients
Servers
Dr. R. B. Patel

35. Challenges Mobility/context aware applications Naming and locating
Routing data and messages
Reliability in presence of disconnection
Data management
Transaction models
Security
Dr. R. B. Patel

36. Continued…
Mobile computing affects entire spectrum of issues in computing
First of all it is distributed + mobile computing
Distributed computing as we know works on static wired network
Node may initiate computation somewhere and migrate to another place.
So two major problems that arise due to mobility
Searching for current location of a mobile node
To impose a communication structure among nodes
Dr. R. B. Patel

37. Continued…
Physical location of mobile host is not the network address, so how do we route the message to a mobile host.
This question is being addressed by two different communities- Internet community and cellular community
Work of Internet community involves Mobile IP
Aims at standards that can extend IP in order to deal with location of mobile host
Mobile IP work assumes connectionless packet switching scenario
Dr. R. B. Patel

38. Continued…
Cellular community’s effort based on location management of cellular phone users
It deals with connection-oriented communication, since it is motivated by issues in call-setup in telephony
Main problem in mobility management is to find an appropriate tradeoff between searching and informing
Searching is performed when address of the message recipient is not known- at least not known precisely
Dr. R. B. Patel

39. Continued…
Informing is a responsibility of the mobile host when it migrates
Extreme situations can be
Mobile host never informs- works for hosts receiving few messages and for hosts which do not move during receiving
Always informs – works well for hosts receiving messages frequently
Dr. R. B. Patel

40. Continued… Ad hoc network routing is the ultimate challenge
Ad hoc networks arise in rapid development scenarios
Emergency disaster management
Military operation in remote sites
Business meeting venues without infrastructure support
Many routing algorithms are designed: such as fisheye, state routing, dynamic source routing, ad hoc on demand routing, etc.
There are interesting application of conventional graph theoretic problems in ad hoc network routing
Dr. R. B. Patel

41. Continued… Dr. R. B. Patel (b) Ad hoc network
(a) Infrastructure-based wireless network
(b) Ad hoc network
Dr. R. B. Patel

42. Continued…
Main cause of loss of packets in wired network is congestion because error rates are very low
In wireless network congestion still remains a problem, but the situation is somewhat reversed
Wired and wireless network require different techniques to achieve reliability and flow control
TCP works is unsuitable for wireless network as it interprets errors packets loss
Dr. R. B. Patel

43. Continued… ITCP (split/indirect TCP) splits TCP into two parts
One between sender and local MSS of the recipient
The other between local MSS and recipient
If MH switches cell during lifetime of a ITCP connection center point of connection moves to new MSS sender remains completely unaware about it
Dr. R. B. Patel

44. Continued… Disconnection/weak connection support is important
CODA file system provides support for this
It is implemented as client side cache management system
The issue concerns making a file system highly available while maintaining consistency
Caching in mobile environment is quite different. MSS cannot keep state information (due to scale) for all clients. So invalidation by notification
Dr. R. B. Patel

45. Continued… Categories of information dissemination
Wide area services – such as stock quotes on national scale
Macro services- such weather on a regional scale
Micro services- traffic condition is an immediate vicinity
Can be extend to even picocells – such finding a parking slot
Dr. R. B. Patel

46. Continued…
Proving services will require addressing of following new issues
Interoperability and adaptability to network environments ranging from high to low bandwidths and infrared communication links
Energy efficient data access
Support for mobility and disconnection
Support for active services, triggers (even notification), and periodic data delivery.
Dr. R. B. Patel

47. Continued… Two modes of information dissemination are Publish
Provide on demand
Publish data is filtered by client and server provides directory information for assisting the filtering
Advantages of information dissemination by publishing are
Hot spots can be broadcast frequently-which saves energy at client, avoid congestion
Directory helps client to tune in selectively
Dr. R. B. Patel

48. Continued…
Handoff management – an MH moves from one cell to another while being connected
Desirable features are
Probability of call dropping is minimized
Ping-pong handoffs avoided
Interruption is minimized
Dr. R. B. Patel

49. Mobile Computing Models
The following models of computing in the mobile environment are currently being researched and investigated:
Client/Server
Client/Proxy/server
Disconnected Operation
Mobile Agents
The Thin Client Model
Dr. R. B. Patel