Transcript Data Provisioning Services for mobile clients

Data Provisioning Services
for mobile clients
by
Mustafa Ergen
Authors: Mohit Agarwal and Anuj Puri
{mohit,anuj}@eecs.berkeley.edu
Berkeley WOW Group
University of California Berkeley
Outline
Motivation
Problem Definition
Main Idea
System Architecture
Software Architecture
Application Design
Motivation
Cost of downloading data remains high
in Wireless Networks
Many wireless applications can be
designed without need for real time
support
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Stored multimedia (music, video,
presentations)
Locality maps (with 3d renderings etc)
Problem Definition
Design a wireless network for
mobile clients to access bufferable
data
Main Idea
Since data is delay tolerant, it suffices to provide
intermittent “bursty” access to the network
Introduce buffers in the network to exploit


The variability in bandwidth
Delay tolerance of data
Changes the paradigm from
“Anywhere Anytime” connectivity to
“Somewhere Sometime” connectivity
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Infostation Model (First Proposed by Rutgers-WINLAB)
Interesting Scenarios
Automobile Clients

Say a “burst” of 5 seconds every minute
BW
Time
Passengers in Commuter Trains/Buses

Route is predictable and large data traffic
make this architecture very suitable
System Architecture
Mini Base Stations
Proxy
Internet /
DataBase Server
Intermediate Network
Mobile
System Architecture
Mini base stations (MBS) placed every mile

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Freeways, city etc
Connect them with backbone network
Typical range ~ 100m (radius)
When mobile passes under an MBS, it
downloads the data that it needs

The whole file is transferred across several MBS
More number of users can be handled pu
area (for the same average data rate)
Key Issues
Data Provisioning Protocol Design

Interface and functionality of each layer
Design of applications for such a
network
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Carefully manage varying bandwidth
Data-Management Issues
How to make data available at the MBS when
the mobile passes under it
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Bandwidths on the links feeding the MBS may be
small or the communication delays there may be
larger
Mobile may be under an MBS for a short duration
How much data to “push” to which MBS
How is the mobility and bandwidth
information shared among different entities
We need some intelligence in the network
The need for a Proxy
Proxy acts as an interface to Internet


It downloads and stores the file from the DB
Avoids connection setup delays involved if every
Infostation were to communicate with the Internet
Runs data management algorithms to exploit
bursty link of the mobile.

Makes data available at the MBS before mobile
arrives.
Carries out higher layer communication with
the mobile
Software Architecture
APP
ProxyAPP
TL
TL
DPL
DPL
MAC
MAC
Mobile
MBS
IP
TCP/IP
APP
DPL
Proxy
DB
TL: Transport Layer
End to End functionality between
mobile and the proxy
Connection Setup
Acks for Reliability (if required)
Packetization
No Congestion Control
DPL: Data Provisioning Layer
Mobile
Registration
Registration
Dereg
Data
Data
MBS
Proxy
DPL Contd.
Registration
Rate Control while sending data
Mobility prediction
Buffering at

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Proxy: Data that is sent down by TL has to be be
buffered until it is forwarded to correct MBS
MBS: Data that is sent from DPL of Proxy is
buffered until it can be delivered to mobile
DPL Contd.
•Data Structure maintained at DPL
Proxy
Mobile/Session ID
Registered or not
MBS/RTT/BW
Map/Speed/Direction
Next MBS/RTT/BW
Data Buffer
MBS
Mobile/Session ID
Registered or not
Proxy’s Address
Time Left
Data
Buffer
Over all Picture
Mobile requests a file (map / music stream)
Default Proxy is the MBS through which the
request was made
Proxy fetches the file from the DB
Proxy delivers a segment of this file to the
MBS where mobile is registered
As mobile moves, Proxy “pushes” some part
of the file to “next” MBS even before mobile
has registered there
MBS buffer the segments and deliver it to the
mobile when it passes under its coverage
Application Design
Application may have an alternate
(costly, ubiquitous) network like 3G
cellular available
Intelligent buffering to reduce the
download costs

download more in the cheaper mini base
stations
Relationship to Mobile IP
Runs independently of Mobile IP
MBS can act as foreign agents also

However small burst duration may not be
enough for Mobile IP
Mobile may choose to use either
protocols depending on the data
required and the network available
Conclusion
We have proposed an architecture for
providing cheaper access to wireless
data
Designed the software architecture for
this network
We are currently in the process of
implementing this network on a small
testbed