Data Provisioning Services for mobile clients by Mustafa Ergen Authors: Mohit Agarwal and Anuj Puri 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 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 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 Mobile Intermediate 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 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 TL DPL MAC DPL TL MAC Mobile MBSProxy APP DB ProxyAPP IP TCP/IP

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 MBSProxyMobile Registration Dereg Data

DPL Contd. Registration Rate Control while sending data Mobility prediction Buffering 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 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