| # | Mobile Computing |
Mobile Computing 
Migration is important for survival.
Mobility originated from the desire to move ei- ther toward resources or away from scarcity.
Mobile computing about both physical and logi- cal computing entities that move.
Physical entities are computers that change lo- cations
Logical entities are instances of a running user application or a mobile agent.
Mobile agents can migrate any where over inter- net.
But active applications can only move to a local cluster of computers.
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| R. K. Ghosh | CSE 100, April, 2005 | 1 of 19 |
| # | Mobile Computing |
Buzzwords 
Mobile, ubiquitous, nomadic, untethered, perva- sive and any time, any where, any person com- puting are used by researchers to refer to com- puting that uses small portable devices and wire- less communication n/w.
Nomadic computing refer to limited migration.
{Migration is within a building at a pedestrian speed.
{Interleaved pattern of user relocation and in- door connections
In the same vein, users carrying laptop with
DIAL-UP modems are engaged in nomadic com- puting.
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| R. K. Ghosh | CSE 100, April, 2005 | 2 of 19 |
| # | Mobile Computing |
Buzzwords 
Mobile computing requires
{wireless n/w to support outdoor mobility and hando from one n/w to the next at a pedes- trian 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 can not be realized unless mobile computing matures.
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| R. K. Ghosh | CSE 100, April, 2005 | 3 of 19 |
| # | Mobile Computing |
Relationships: Nomadic{Mobile 
Laptops, PDAs, other hand held device
| No | Fixed | Fixed | Wireless | wireless | ||||||||
| wireless | ||||||||||||
| n/w | n/w | n/w (A) | n/w (B) | |||||||||
| n/w | ||||||||||||
| Nomadic computing | Mobile computing | |||||||||||
| Ubiquitous computing | ||||||||||||
| " | Department of C S E | ! | |
| R. K. Ghosh | CSE 100, April, 2005 | 4 of 19 |
| # | Mobile Computing |
Challenges 
Mobility/context aware applications
Naming and locating
Routing data and messages
Reliability in presence of disconnection
Data management
Transaction models
Security
| " | Department of C S E | ! | |
| R. K. Ghosh | CSE 100, April, 2005 | 5 of 19 |
| # | Mobile Computing |
Challenges 
Mobile computing a ects entire spectrum of is- sues in computing.
First of all it is distributed + mobile computing.
Distributed computing as we know works on static wired network.
Node may initiate computation some where and migrate to another place.
So two major problem that arise due to mobility
{Searching for current location of a mobile node.
{To impose a communication structure among nodes.
| " | Department of C S E | ! | |
| R. K. Ghosh | CSE 100, April, 2005 | 6 of 19 |
| # | Mobile Computing |
Challenges 
Physical location of mobile is not the network address, so how do we route the message to a mobile host.
This question is being addressed by two di erent 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 connection-less, packet switching scenario.
| " | Department of C S E | ! | |
| R. K. Ghosh | CSE 100, April, 2005 | 7 of 19 |
| # | Mobile Computing |
Challenges 
Cellular community's e ort based on location management of cellular phone users.
It deals with connection oriented communica- tion, since it is motivated by issues in call-setup in telephony.
Main problem in mobility management is to nd an appropriate trade-o between searching and informing.
Searching is performed when address of the mes- sage recipient is not known { at least not known precisely.
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| R. K. Ghosh | CSE 100, April, 2005 | 8 of 19 |
| # | Mobile Computing |
Challenges 
Informing is a responsibility of the mobile unit when it migrates.
Extreme situations can be
1.Mobile unit never informs { works for units receiving few messages and for units which don't move during receiving.
2.Always informs { works well for units receiving messages frequently.
| " | Department of C S E | ! | |
| R. K. Ghosh | CSE 100, April, 2005 | 9 of 19 |
| # | Mobile Computing |
Challenges 
Ad hoc network routing is the ultimate challenge.
Ad hoc networks arise in rapid deployment sce- narios:
1.Emergency disaster management.
2.Military operation in remote sites.
3.Business meeting venues without infrastruc- ture support.
Many routing algorithms are designed: AODV,
DSR, DSDV, TORA, FSR, LAR, ABR, etc.
There are interesting application of conventional graph theoretic problems in ad hoc network rout- ing.
| " | Department of C S E | ! | |
| R. K. Ghosh | CSE 100, April, 2005 | 10 of 19 |
| # | Mobile Computing |
Challenges 
Main cause of loss of packets in wired network is congestion because error rates are very low.
In wireless n/w congestion still remains a prob- lem, but he situation is some what reversed.
Wired and wireless n/w require di erent tech- niques to achieve reliability and ow control.
TCP works is unsuitable for wireless n/w as it interprets errors as packet loss.
| " | Department of C S E | ! | |
| R. K. Ghosh | CSE 100, April, 2005 | 11 of 19 |
| # | Mobile Computing |
Challenges 
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 life time of a ITCP connection center point of connection moves to new MSS. sender remains completely un- aware about it.
| " | Department of C S E | ! | |
| R. K. Ghosh | CSE 100, April, 2005 | 12 of 19 |
| # | Mobile Computing |
Challenges 
Disconnection/weak connection support is im- portant.
CODA le system provides support for this.
It is implemented as a client side cache manage- ment system.
The issue concerns making a le system highly available while maintaining consistency.
Caching in mobile environment is quite di er- ent. MSS can not keep state information (due to scale) for all client. So invalidation by noti - cation.
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| R. K. Ghosh | CSE 100, April, 2005 | 13 of 19 |
| # | Mobile Computing |
Challenges 
Categories of information dissemination:
1.Wide area services { such as stock quotes on national scale
2.Macroservices { such weather on a regional scale.
3.Microservices { tra c condition in an imme- diate vicinity.
Can be extend to even picocells { such nding a parking slot.
| " | Department of C S E | ! | |
| R. K. Ghosh | CSE 100, April, 2005 | 14 of 19 |
| # | Mobile Computing |
Challenges 
Providing services will require addressing of fol- lowing new issues
{Interoperability and adaptability to n/w en- vironments ranging from high to low band- widths and infra red communication links
{Energy e cient data access.
{Support for mobility and disconnection.
{Support for active services, triggers (even no- ti cation), periodic data delivery.
| " | Department of C S E | ! | |
| R. K. Ghosh | CSE 100, April, 2005 | 15 of 19 |
| # | Mobile Computing |
Challenges 
Two modes of information dissemination are
1.Publish.
2.Provide on demand.
Published data is ltered by client and server provides directory information for assisting theltering.
Advantages of information dissemination by pub- lishing are:
{Hot spots can be broadcast frequently { which saves energy at client, avoid conges- tion.
{Directory helps client to tune in selectively.
| " | Department of C S E | ! | |
| R. K. Ghosh | CSE 100, April, 2005 | 16 of 19 |
| # | Mobile Computing |
Challenges 
Hando management { an MH moves from one cell to another while being connected.
Desirable features are:
{probability of call dropping is minimized.
{ping-pong hando s avoided.
{interruption is minimized.
| " | Department of C S E | ! | |
| R. K. Ghosh | CSE 100, April, 2005 | 17 of 19 |
| # | Mobile Computing |
Challenges 
Conventional model will not work.
Kangaroo-joey transaction
Two-tier transaction
Team transaction
Isolation-Only transaction
| " | Department of C S E | ! | |
| R. K. Ghosh | CSE 100, April, 2005 | 18 of 19 |
| # | Mobile Computing |
Challenges 
Security is a major concern.
Authentication schemes.
Encryption schemes.
Payment schemes.
{E-tickets { getting a service by producing a ticket.
{E-currency { issues like anonymity, credit- worthiness, non-repudiation, etc.
Mobile agent security.
| " | Department of C S E | ! | |
| R. K. Ghosh | CSE 100, April, 2005 | 19 of 19 |
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