Infostations - PowerPoint PPT Presentation

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Infostations

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geographical location with a ... The process is automated and should not require any human interaction. ... No need for obsequies coverage. A Typical Scenario ... – PowerPoint PPT presentation

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Title: Infostations


1
Infostations
  • Niraj Patel

2
Background
  • An Infostation is a wireless information
    service, confined to a small
  • geographical location with a limited coverage
    area. As users pass thorough the coverage area,
    the infostation deploys information to their PDA
    laptop computer. The process is automated and
    should not require any human interaction.
    Services an Infostation might provide
  • -Restaurant listings
  • -News
  • -Synchronize Email
  • -Local places of interest
  • Developed at WINLAB in the early 90s,
    Infostation goals are to provide low cost, high
    bit rate, low power network connections to a
    restricted coverage area.

3
An Infostation System
  • 1) Mobile devices,
  • whose users would
  • send and receive
  • data to the Infostation.
  • 2) The Infostation
  • which consists of a
  • Wireless access point
  • that is hooked up to a
  • PC that is connected
  • to the internet.

4
Why Infostations?
  • The problem with existing systems (Cellular) is
    they are primarily
  • designed for voice. Because of this, they have
    to deliver service anywhere, and anytime. Also
    to deliver non voice services, high bit rates are
    necessary which would result in a high costing
    infrastructure.
  • Advantages
  • -Use of unlicensed bands, make it easy to deploy
    and make it cheaper
  • -High Bandwidth (500MB/s)
  • -No need for obsequies coverage

5
A Typical Scenario
  • Consider an Infostation at an airport terminal,
    while in flight the user would have pre-written
    Emails on their PDA. They also decides that they
    would grab a bite to eat after landing. When
    they arrives at the terminal their PDA starts
    talking to the terminal infostation and sends out
    the emails. It also then retrieves local
    restaurant information. This all happens with
    automatically. They would have to do as little
    as possible.

6
Data Transmission (1-2)
  • A cycle transmitted from the infostation.
  • Index Includes information that clients can
    use and determine how or when to listen for
    each item, so they can conserve power by ignoring
    items they do not want.
  • Requests After the index there is a pause.
    This allows clients to decide which items to
    listen to.
  • Data The server transmits requested data items
  • Feedback The client uploads data, or sends
    requests

7
Data Transmission (2-2)
  • Two ways the infostation broadcasts
  • IP multicast The client joins the multicast
    group for the items it want but will receive
    unwanted data packets which it will later drop.
  • Explicit Client Control In this method, the
    index includes information about when each item
    will be transmitted and the client goes into low
    power mode, waking up to receive the desired
    packets, then going back to sleep until its time
    to listen for the next index.
  • In both cases, the client will listen when the
    Infostation sends out the new index in the next
    cycle.

8
Capacity in an InfostationOptimal Vs. Constant
power allocation
  • The reasoning more power is used when the
    mobile device is near the Infostation to maximize
    capacity. This way power is saved to users from
    users who are further away and maximized to the
    optimal conditions.

9
Capacity in Infostations
  • To optimize capacity in an Infostation, a
    different DPSK modulation schemes would be used
    at different SIRs . (DBPSK, DQPSK, 8-DPSK).

10
Capacity in Infostations
  • The different Modulation Schemes have different
    SNRs mapped here with the SIR and Distance
  • Depending on the SIR, a different modulation
    scheme is used.

11
Capacity in Infostations
  • As quality improves, higher
  • modulation schemes are used.
  • Transfer rates vary from 0-24Mbps
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