Transcript Mobile Data Management

Class Number – CS486
Class Name –
Mobile and
Sensor Data
Management
Instructor – Sanjay Madria
Lesson Title - Introduction
What is Pervasive Computing?
• “Pervasive computing is a term for the
strongly emerging trend toward:
– Numerous, casually accessible, often invisible
computing devices
– Frequently mobile or embedded in the
environment
– Connected to an increasingly ubiquitous
network structure.”
– NIST, Pervasive Computing 2001
Party on Friday
• Update Smart Phone’s calendar with
guests names.
• Make a note to order food from
Dinner-on-Wheels.
• Update shopping list based on the
guests drinking preferences.
• Don’t forget to swipe that last can of
beer’s UPS label.
• The shopping list is always up-todate.
Party on Friday
• AutoPC detects a near Supermarket that advertises
sales.
• It accesses the shopping list and your calendar on the
Smart Phone.
• It informs you the soda and beer are on sale, and
reminds you that your next appointment is in 1 hour.
• There is enough time based on the latest traffic report.
Party on Friday
• Smart Phone reminds you that you need to order
food by noon.
• It downloads the Dinner-on-Wheels menu from
the Web on your PC with the guests’ preferences
marked.
• It sends the shopping list to your CO-OP’s PC.
• Everything will be delivered by the time
you get home in the evening.
Mobile Applications
•
Expected to create an entire new class of
Applications
– new massive markets in conjunction with the Web
– Mobile Information Appliances - combining personal
computing and consumer electronics
• Applications:
– Vertical: vehicle dispatching, tracking, point of sale
– Horizontal: mail enabled applications, filtered information
provision, collaborative computing…
Mobile and Wireless Computing
• Goal: Access Information Anywhere, Anytime,
and in Any Way.
• Aliases: Mobile, Nomadic, Wireless, Pervasive,
Invisible, Ubiquitous Computing.
• Distinction:
• Fixed wired network: Traditional distributed computing.
• Fixed wireless network: Wireless computing.
• Wireless network: Mobile Computing.
 Key Issues: Wireless communication, Mobility,
Portability.
Terminologies
• GSM - Global System for Mobile Communication
– GSM allows eight simultaneous calls on the same radio
frequency and uses narrowband TDMA. It uses time as
well as frequency division.
• TDMA - Time Division Multiple Access
– With TDMA, a frequency band is chopped into several
channels or time slots which are then stacked into
shorter time units, facilitating the sharing of a single
channel by several calls
• CDMA - Code Division Multiple Access
– data can be sent over multiple frequencies
simultaneously, optimizing the use of available
bandwidth.
– data is broken into packets, each of which are given a
unique identifier, so that they can be sent out over
multiple frequencies and then re-built in the correct
order by the receiver.
TDMA
Wireless Technologies
• Wireless local area networks (WaveLan, Aironet) –
Possible Transmission error, 1.2 Kbps-15 Mbps
• Cellular wireless (GSM, TDMA, CDMA)– Low
bandwidth, low speed, long range - Digital: 9.6-14.4
Kbps
• Packet radio (Metricom) -Low bandwidth, high speed,
low range and cost
• Paging Networks – One way
• Satellites (Inmarsat, Iridium(LEO)) – Long Latency,
long range, high cost
Mobile Network Architecture
Wireless characteristics
• Variant Connectivity
– Low bandwidth and reliability
• Frequent disconnections
• predictable or sudden
• Asymmetric Communication
– Broadcast medium
• Monetarily expensive
– Charges per connection or per message/packet
 Connectivity is weak, intermittent and expensive
Portable Information Devices
• PDAs, Personal Communicators
–
–
–
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Light, small and durable to be easily carried around
dumb terminals, palmtops, wristwatch PC/Phone,
will run on AA+ /Ni-Cd/Li-Ion batteries
may be diskless
• I/O devices: Mouse is out, Pen is in
• Wireless connection to information networks
– either infrared or cellular phone
• Specialized Hardware (for compression/encryption)
Portability Characteristics
• Battery power restrictions
– transmit/receive, disk spinning, display, CPUs,
memory consume power
• Battery lifetime will see very small increase
– need energy efficient hardware (CPUs, memory)
and system software
– planned disconnections - doze mode
Power consumption vs. resource utilization
Portability Characteristics Cont.
• Resource constraints
– Mobile computers are resource poor
– Reduce program size – interpret script languages (Mobile
Java?)
– Computation and communication load cannot be
distributed equally
• Small screen sizes
 Asymmetry between static and mobile computers
Mobility Characteristics
• Location changes
• location management - cost to locate is added to
communication
• Heterogeneity in services
– bandwidth restrictions and variability
• Dynamic replication of data
• data and services follow users
• Querying data - location-based responses
• Security and authentication
 System configuration is no longer static
What Needs to be Reexamined?
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Operating systems - TinyOS
File systems - CODA
Data-based systems – TinyDB
Communication architecture and protocols
Hardware and architecture
Real-Time, multimedia, QoS
Security
Application requirements and design
PDA design: Interfaces, Languages
Mobility Constraints
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CPU
Power
Variable Bandwidth
Delay tolerance, but unreliable
Physical size
Constraints on peripherals and GUIs
Frequent Location changes
Security
Heterogeneity
Expensive
Frequent disconnections but predictable
What is Mobility?
•
A device that moves between
– different geographical locations
– Between different networks
• A person who moves between
– different geographical locations
– different networks
– different communication devices
– different applications
Device mobility
• Laptop moves between Ethernet, WaveLAN and
Metricom networks
– Wired and wireless network access
– Potentially continuous connectivity, but may be
breaks in service
– Network address changes
– Radically different network performance on
different networks
– Network interface changes
• Can we achieve best of both worlds?
– Continuous connectivity of wireless access
– Performance of better networks when available
Mobility Means Changes
• Addresses
– IP addresses
• Network performance
– Bandwidth, delay, bit error rates, cost, connectivity
• Network interfaces
– PPP, eth0, strip
• Between applications
– Different interfaces over phone & laptop
• Within applications
– Loss of bandwidth trigger change from color to
B&W
• Available resources
– Files, printers, displays, power, even routing
Bandwidth Management
• Clients assumed to have weak and/or
unreliable communication capabilities
• Broadcast--scalable but high latency
• On-demand--less scalable and requires
more powerful client, but better response
• Client caching allows bandwidth
conservation
Energy Management
• Battery life expected to increase by only
20% in the next 10 years
• Reduce the number of messages sent
• Doze modes
• Power aware system software
• Power aware microprocessors
• Indexing wireless data to reduce tuning time
Why Mobile Data Management?
• Wireless Connectivity and use of PDA’s, handheld
computing devices on the rise
• Workforces will carry extracts of corporate
databases with them to have continuous connectivity
• Need central database repositories to serve these work
groups and keep them fairly upto-date and consistent
Mobile Data Applications
• Sales Force Automation - especially in
pharmaceutical industry, consumer goods,
parts
• Financial Consulting and Planning
• Insurance and Claim Processing - Auto,
General, and Life Insurance
• Real Estate/Property Management Maintenance and Building Contracting
• Mobile E-commerce
Mobility – Impact on DBMS
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Handling/representing fast-changing data
Scale
Data Shipping v/s Query shipping
Transaction Management
Replica management
Integrity constraint enforcement
Recovery
Location Management
Security
User interfaces
DBMS Industry Scenario
• Most RDBMS vendors support the mobile scenario but no design and optimization aids
• Specialized Environments for mobile applications:
Sybase Remote Server
Synchrologic iMOBILE
Microsoft SQL server - mobile application support
Oracle Lite
Xtnd-Connect-Server (Extended Technologies)
Scoutware (Riverbed Technologies)
Query Processing
• New Issues
– Energy Efficient Query Processing
– Location Dependent Query Processing
• Old Issues - New Context
– Cost Model
Location Management
• New Issues
– Tracking Mobile Users
• Old Issues - New Context
– Managing Update Intensive Location
Information
– Providing Replication to Reduce Latency for
Location Queries
– Consistent Maintenance of Location
Information
Transaction Processing
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New Issues
– Recovery of Mobile Transactions
– Lock Management in Mobile Transaction
Old Issues - New Context
Extended Transaction Models
– Partitioning Objects while Maintaining
Correctness
Data Processing Scenario
• One server or many servers
• Shared Data
• Some Local Data per client , mostly subset of
global data
• Need for accurate, up-to-date information, but some
applications can tolerate bounded inconsistency
• Client side and Server side Computing
• Long disconnection should not constraint availability
• Mainly Serial Transactions at Mobile Hosts
• Update Propagation and Installation
Personal Communication System
(PCS)
A system where wired and wireless networks are integrated for
establishing communication.
PSTN
AC
HLR
VLR
MSC (MTSO)
MSC (MTSO)
BS
Wireless component
EIR
MS
MS
PSTN: Public Switched Network.
MSC: Mobile Switching Center. Also called MTSO
(Mobile Telephone Switching Office).
BS:
Base Station.
MS:
Mobile Station. Also called MU (MobileUnit)
or Mobile Host (MH).
HLR: Home Location Register.
VLR: Visitor Location Register.
EIR:
Equipment Identify Register.
AC:
Access Chanel.
Personal Communication System
(PCS)
Wireless Components
MSC (MTSO)
BS
MS
MS
Cell
Wireless
component
Personal Communication System
(PCS)
Mobile cells
The entire coverage area is a group of a number of cells.
The size of cell depends upon the power of the base
stations.
MSC
PSTN
Personal Communication System (PCS)
Problems with cellular structure
 How to maintain continuous communication
between two parties in the presence of
mobility?
Solution: Handoff
 How to maintain continuous communication
between two parties in the presence of mobility?
Solution: Roaming
 How to locate of a mobile unit in the entire
coverage area?
Solution: Location management
Personal Communication System
(PCS)
Handoff
A process, which allows users to remain in touch, even
while breaking the connection with one BS and
establishing connection with another BS.
MSC
MSC
New BS Old BS
Old BS
MSC
MSC
Old BS
New BS
New BS
Old BS
New BS
Personal Communication System
(PCS)
Handoff
To keep the conversation going, the
Handoff procedure should be completed while the
MS (the bus) is in the overlap region.
Cell overlap region
G
Old BS
New BS
Personal Communication System
(PCS)
Roaming

Roaming is a facility, which allows a subscriber to
enjoy uninterrupted communication from anywhere in
the entire coverage space.

A mobile network coverage space may be
managed by a number of different service providers.
They must cooperate with each other to provide
roaming facility.

Roaming can be provided only if some
administrative and technical constraints are met.
Personal Communication System
(PCS)
Roaming
Administrative constraints
 Billing.
 Subscription agreement.
 Call transfer charges.
 User profile and database sharing.
 Any other policy constraints.
Personal Communication System
(PCS)
Roaming
Technical constraints
 Bandwidth
mismatch.
For example,
European 900MHz band may not be available
in other parts of the world.

Integration of a new service provider into the network.
A roaming subscriber must be able to detect this new
provider.
 Service
providers
must
be
able
to
communicate with each other. Needs some
standard.
 Mobile station constraints.
Personal Communication System
(PCS)
Roaming
Two
basic
operations
management are
 Registration
(Location
in
roaming
update):
The
process of informing the presence or
arrival of a MU to a cell.
 Location tracking: the process of locating
the desired MU.
Personal Communication System
(PCS)
Roaming
Registration (Location update): There are six different
types of registration.
 Power-down registration. Done by the MU when it
intends to switch itself off.
 Power-up registration. Opposite to power-down
registration. When an MU is switched on, it
registers.
 Deregistration. A MU decides to acquire control
channel service on a different type of network
(public, private, or residential).
Personal Communication System
(PCS)
Roaming
Registration (Location update): There are six different
types of registration.



New system/Location area registration: when the location
area of the MU changes, it sends a registration message.
Periodic registration: A MU may be instructed to periodically
register with the network.
Forced registration: A network may, under certain
circumstances, force all MUs to register.
Personal Communication System
(PCS)
Registration
Two-Tier Scheme
HLR: Home Location Register
A HLR stores user profile and the geographical
location of each moving object at a prespecified location
VLR: Visitor Location Register
A VLR stores user profile and the current
location who is a visitor to a different cell than
its home cell.
Personal Communication System
(PCS)
Registration
Two-Tier Scheme steps. MU1 moves to cell 2.
Cell 1
Cell 2
MU1
MU1
Personal Communication System
(PCS)
Registration
Steps
1.
MU1 moves to cell 2. The MSC of cell 2 launches a
registration query to its VLR 2.
2.
VLR2 sends a registration message containing MU’s
identity (MIN), which can be translated to HLR address.
3.
After registration, HLR sends an acknowledgment back
to VLR2.
4.
HLR sends a deregistration message to VLR1 (of cell 1)
to delete the record of MU1 (obsolete).
VLR1
acknowledges the cancellation.
Personal Communication
System (PCS)
Location tracking (MU2 wants to communicate with MU1)
Steps
1. VLR of cell 2 is searched for MU1’s profile.
2. If it is not found, then HLR is searched.
3. Once the location of MU1 is found, then the
information is sent to the base station of cell
1.
4. Cell 1 establishes the communication.