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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

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Data Provisioning Services for mobile clients

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  1. Data Provisioning Servicesfor mobile clients by Mustafa Ergen Authors: Mohit Agarwal and Anuj Puri {mohit,anuj}@eecs.berkeley.edu Berkeley WOW Group University of California Berkeley

  2. Outline • Motivation • Problem Definition • Main Idea • System Architecture • Software Architecture • Application Design

  3. 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)

  4. Problem Definition • Design a wireless network for mobile clients to access bufferable data

  5. 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)

  6. 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 BW Time

  7. System Architecture Mini Base Stations Proxy Internet / DataBase Server Intermediate Network Mobile

  8. 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)

  9. Key Issues • Data Provisioning Protocol Design • Interface and functionality of each layer • Design of applications for such a network • Carefully manage varying bandwidth

  10. 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

  11. 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

  12. Software Architecture APP ProxyAPP APP TCP/IP TL TL IP DPL DPL DPL MAC MAC MBS Proxy DB Mobile

  13. TL: Transport Layer • End to End functionality between mobile and the proxy • Connection Setup • Acks for Reliability (if required) • Packetization • No Congestion Control

  14. DPL: Data Provisioning Layer Registration Dereg Registration Data Data Mobile MBS Proxy

  15. 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

  16. DPL Contd. • Data Structure maintained at DPL MBS Proxy 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

  17. 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

  18. 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

  19. 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

  20. 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

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