Data Provisioning Servicesfor mobile clients

byMustafa Ergen

Authors: Mohit Agarwal and Anuj Puri{mohit,anuj}@eecs.berkeley.edu

Berkeley WOW GroupUniversity of California Berkeley

Outline

MotivationProblem DefinitionMain IdeaSystem ArchitectureSoftware ArchitectureApplication Design

Motivation

Cost of downloading data remains high in Wireless Networks Many wireless applications can be designed without need for real time support 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 networkIntroduce 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 Infostation Model (First Proposed by Rutgers-

WINLAB)

Interesting Scenarios

Automobile Clients Say a “burst” of 5 seconds every minute

Passengers in Commuter Trains/Buses Route is predictable and large data traffic

make this architecture very suitable

Time

BW

System Architecture

Proxy

Internet /DataBase Server

Mini Base Stations

MobileIntermediate Network

System Architecture

Mini base stations (MBS) placed every mile 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 Carefully manage varying bandwidth

Data-Management Issues

How to make data available at the MBS when the mobile passes under it 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 MBSHow is the mobility and bandwidth information shared among different entitiesWe 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

TL

DPL DPL

MAC

DPL

TL

MAC

Mobile MBS Proxy

APP APP

DB

ProxyAPP

IP

TCP/IP

TL: Transport Layer

End to End functionality between mobile and the proxyConnection SetupAcks for Reliability (if required)PacketizationNo Congestion Control

DPL: Data Provisioning Layer

MBS ProxyMobile

RegistrationRegistrationDereg

Data Data

DPL Contd.

RegistrationRate Control while sending dataMobility predictionBuffering at 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.

Mobile/Session ID Registered or not MBS/RTT/BW Map/Speed/Direction Next MBS/RTT/BW Data Buffer

Mobile/Session ID Registered or not Proxy’s Address Time Left Data Buffer

Proxy MBS

•Data Structure maintained at DPL

Over all Picture

Mobile requests a file (map / music stream)Default Proxy is the MBS through which the request was madeProxy fetches the file from the DBProxy delivers a segment of this file to the MBS where mobile is registeredAs mobile moves, Proxy “pushes” some part of the file to “next” MBS even before mobile has registered thereMBS 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 availableIntelligent buffering to reduce the download costs download more in the cheaper mini

base stations

Relationship to Mobile IP

Runs independently of Mobile IPMBS 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 dataDesigned the software architecture for this networkWe are currently in the process of implementing this network on a small testbed