Easy Accessible Voice Gateway between Mbone and ISDN/PSTN Networks

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Easy Accessible Voice Gateway between Mbone and
ISDN/PSTN Networks

• Linqing Liu and Torsten Braun
• Institute of Computer Science and Applied
  Mathematics 
• University of Berne
• liubraun_at_iam.unibe.ch

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Outline

• Introduction
• Scenario
• Main functionalities
• Structure
• Audio forwarding and support unit
• Gateway control unit
• Usage and some sample snapshots
• Gateway administration
• Limitation and future work

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Introduction

• IP based telephony is booming with low cost
  long-distance calls.
• IP telephony is convenient to set up conference
  without the need of expensive Multipoint Control
  Unit (MCU).
• Related work
• -ISDN4Linux
• -Mbone2Tel
• -AudioGate in MECCANO project
• Architecture and implementation of an easy
  accessible voice gateway between MBONE and ISDN
  with integration of existing component from
  public domain software.

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Scenario
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Conference scenario
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Main functionalities

• Display available multicast session list via
  HTML/WML pages, keyword searchable.
• User registration/creating new session via
  HTML/WML.
• Get session contact information via
  HTML/WML/SMS/Email.
• Click-to-dial for existing gateway users.
• Gateway administration/configuration via HTML.

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Processing client request
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Main structure
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Audio forwarding and support unit

• Responsible for converting audio data between
  Mbone and ISDN/PSTN networks, listening to
  existing Mbone sessions and announcing new
  sessions over the Mbone
• Try to use existing software in public domain as
  components for audio forwarding and support unit
• -Using AudioGate in MECCANO project as audio
  
• forwarding component.
• -Using mSD as daemon to listen Mbone session
  
• information.
• -Using mAnnouncer to send out SDP file over
  Mbone for new session announcement.

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AudioGate functionalities

• Calling users can be authenticated based upon
  their Calling Line Identification (CLI)
• Allow to assign a full name to each of these
  numbers for presentation in the Mbone Sesion.
• Provide a simple (easily configurable) voice menu
  for prompting callers for a conference selection.
• Conferences can either be explicitly selected
  through the voice menu or callers can
  automatically be put into a particular
  conference.
• Imposes no artificial limits on the number of
  simultaneous calls it can handle. The only
  practical limit is the number of B channels that
  are available. Support one or more ISDN BRI
  boards.

• Supports up to nine simultaneous conferences.
• Can be configured to use any number of ISDN
  Multiple Subscriber Numbering (MSN). Some of them
  can be directly mapped into a conference while
  others may first lead into a voice menu.
• Supports muting/
• unmuting callers using Dual-Tone Multi-Frequency
  (DTMF) for control. The initial status for the
  callers can be configured in the AudioGate
  initialization file.
• All codecs and transmission modes (particularly
  including redundancy coding) supported by Robust
  Audio Tool (RAT) are supported by AudioGate.

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Gateway control unit

• Main component to achieve easy accessibility.
• Provide user registration via HTML/WML web pages
  with selectable Mbone session list.
• Create new Mbone session via HTML/WML.
• Enable user calling participant via
  HTML/WML(click-to-dial).
• Gateway administration/configuration via HTML.

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Gateway control unit(cont.)
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Display Session Information and User Registration

• Transform mSD cache files to HTML/WML pages.
• Generate HTML/WML page according to keywords
  inputted by users, together with registration
  form.
• Provide gateway contact information after user
  registration.

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Screen snapshot after inputting TV as searching
keyword
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Display gateway contact information
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Create New Sessions via HTML/WML

• Generate SDP files via HTML/WML interfaces in
  compliance with SDP, MALLOC, SAP requirements.
• Announce the new sessions via mAnnouncer.
• Display new session information in HTML/WML pages
  and send the new session information to
  email/SMS.
• Support click-to-dial by utilizing the relevant
  functionality from AudioGate.

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Snapshot for creating a new session with WAP
mobile phone
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Gateway Administration

• Gateway configuration via HTML interface with
  system administrator authentication.
• Gateway accounting mechanism via parsing
  AudioGate log files.

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Snapshot for gateway administration
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Limitations and future works

• Implemented in Linux PC with ISDN BRI board.
• One ISDN board support two lines.
• Limited slots for ISDN boards.
• AudioGate supports nine sessions simultaneously.
• Future works
• -To develop a mechanism for seamless service
  without interrupting existing users.
• -To support AudioGate Mbus interface in future
  versions.