ofono – open source telephony june 2009 denis kenzior oscon 2009

oFono – Open Source Telephony

June 2009

Denis Kenzior

OSCON 2009

22Software and Services Group 2

Intel Confidential

Agenda

• What is Telephony?

• What is GSM?

• Past Approaches

• oFono

• Questions


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What is Telephony?

• Definition: The use or operation of an apparatus (as a telephone) for transmission of sounds as electrical signals between widely removed points

• Today it is much more than that:– POTS– Mobile Telephony– IP Telephony


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Product Categorization

• Plain old telephony system


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• Desktop devices


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• Mobile Telephony Devices


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Convergence

• Line between “Mobile” and “Desktop” telephony is blurring– Laptops / Netbooks with 3G– Mobile Phones with WiFi– Mobile Internet Devices (MID)

• Power Management

• Standards, Carrier Compliance

• Comprehensive solution for Mobile Telephony missing– Start with the best candidate: GSM


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Understanding GSM

• GSM – Global System for Mobile communications

• Used by 80% of the mobile market

• 3 Billion subscribers

• 212 Countries

• Digital Voice & Data network


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Understanding GSM

• Voice

• Data

• Fax

• General Packet Radio Service (GPRS)

• Supplementary Services

• Short Messaging Service (SMS)

• Cell Broadcast (CB)

• Enhanced SMS (EMS)

• Multimedia Messaging Service (MMS)

• Location Services

• (U)SIM Application Toolkit ( USAT / STK )


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What makes GSM so hard?

• Voluminous specifications– Call Handling– Supplementary Services– SMS– Cell Broadcast– USSD– Sim Toolkit

• Vendor / Carrier Enhancements– Enhanced SMS (EMS)– Smart Messaging– WAP– OTA

• Technological / Storage Limitations– Number, kind of calls– SIM Filesystem


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What makes GSM really hard?

• Backwards Compatibility– Several evolutions of the spec– Each adds new capabilities, but does not deprecate old ones

• Every bit counts– 7 Bit alphabet– Packing / Unpacking– Binary data structures

• Broken Hardware


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Past Approaches: Qt Extended (Qtopia)

• Developed by Trolltech (now Nokia)

• Dual license (GPL / Commercial)

• Embedded Application Platform

• Fairly Comprehensive Telephony solution– Modem adaptation layer– Modem simulation– Voice / Data, GPRS, SMS / CB– Sim Toolkit support– Custom IPC system based

• Not quite GCF ready out of the box


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Past approaches: FSO

• Aims to provide fully Open Source mobile phones• Open Hardware• Open Source OS & applications

– Similar in scope to Qtopia– Device management APIs– Telephony APIs– Contacts APIs– GPS / Locality

• Telephony based on frameworkd / ogsmd / gsmd– Provides low-level procedural APIs over DBUS, Python based– Modem Adaptation layer– Handles Voice / Data calls, SMS & Cell Broadcast

• Really not GCF ready


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Why reinvent the wheel?

• Qtopia– Custom IPC, broadcast based, no point to point– Too slow– Too heavy– Too complex

• FSO– Does not really consider multiple backend implementations– Only mobile phone useage, no desktop use cases– Logic pushed onto the application– Standards compliance an afterthought– Too slow

• Need something for the 21st century


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Introducing oFono

• oFono is a core system daemon– DBUS API

• Launched by Intel & Nokia on May, 2009

• Licensed under GPL v2– Core and plug-ins are always Open Source

• Plug-ins can be licensed under GPL or GPL compatible (e.g. certain versions of BSD)

• Client applications can choose any license


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oFono: Architecture


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oFono: Philosophy

• Support for all kinds of devices– Desktop– Notebook / Netbook– MID / Mobile Phone– Other embedded devices

• Fast and Light

• Easy to use, powerful API

• Easy to extend

• Command line & graphical interfaces possible

• User Interface easy to replace, logic in the daemon

• Focus on standards compliance from the start

• Ready for the 21st century


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Broad Support

• Support multiple technologies– AT Commands– Library / Socket APIs– AT command-like interfaces

• Bluetooth Handsfree devices

• Support multiple devices simultaneously– USB modems– Serial Modems– Bluetooth devices– Simulated Devices


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Keep experts where they belong

• oFono– Takes care of core logic– Addresses all Telephony aspects that are “Hard to get it right”– Stable and Standards based – Take care of hardware / vendor idiosyncrasies– Take care of compliance– Telephony experts go here

• UI has different focus– Animations– Ease of use– Graphic Design– UI experts go here, not telephony experts


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API so good, anyone can use it

• Consistent– Naming conventions– Similar structure

• Minimal– No Bloat, no more than one way of accomplishing a task– It is easier to add than to change– Most important things first– Feature creep is bad

• Complete– Accomplish everything a typical UI can

• Easy to use


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All Interfaces look alike

• Methods

• Properties– Readonly– Readwrite

• Signals– Emitted when events of interest happen

• Two special methods dealing with properties– dict GetProperties()– SetProperty(string property, variant value)

• Special signal dealing with properties– PropertyChanged(string property, variant value)


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Make it extendable

• Plug-ins can:– Add new modem adaptations– Storage backend for call history– Write to the SIM– Read from the SIM– Send SMS– Receive SMS

• Plug-ins are also first-class citizens:– Add new (unofficial) D-Bus APIs– Example: Datagrams over SMS


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Make UI writer’s job easier

• Multiple user interfaces can be active at the same time– All applications will be informed via DBUS signals when something

has changed

• UI tasks can be logically separated– Dialer– Settings– SMS Client

• UI Applications do not need to be resident

• State is kept by the daemon– State query is fast


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Make UI writer easily replaceable

• UI should be easy to replace– Branding– Customization– Look & Feel

• Can be Open Source or proprietary license


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Standards Compliance

• Take care of magic MMI incantations (22.030)– Registration– Activation– Interrogation– Deactivation– Erasure

• Unrecognized Requests are– Checked for validity– Passed onto the network in the form of a USSD


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Take care of the gory details

• Read & Write appropriate entries to the SIM– Subscriber Numbers– Message Waiting Indications– Service Numbers– Mailbox Numbers– Call Forwarding Settings– Outgoing Call History– Incoming Call History– Cell Broadcast Identifiers


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Take care of the really gory details

• Service Provider Display– Support Mobile Virtual Network Operators (MVNO)– Files on the SIM control how the operator is displayed

• EFspn• EFspdi• EFspni

• Operator Display– Operator lists outdated– Broadcasting the name is not good enough– Enhanced Operator Name

• EFpnn• EFpnni• EFopl


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• Don’t use SIM for Contacts– Limited storage– Limited attribute length– Limited set of attributes– Management details tend to bleed through into UX– SyncML is just better

• Don’t use SIM for SMS– Limited space– Out-of-space conditions

Welcome to the 21st Century


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Peer Collaboration

• oFono plugin for BlueZ– Provides server-side Handsfree Profile capability

• oFono plugin for ConnMan– Planned– Will provide network management of 3G connection

• Future– Time / Timezone settings– Modem emulator

• DUN• Serial Port Profile

– OTA


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Current Development

• Network Registration

• Voice Calls

• Supplementary Services– Call Waiting, Hold, Multiparty– User Determined User Busy– Explicit Call Transfer– Call Forwarding– Call Settings– Call Barring– Advice of Charge

• SMS– Send– Receive

• SIM Phonebook export using vCard 3.0


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Future Work

• Cell Broadcast

• USSD

• Message Waiting Indicators

• GPRS– PPP– Vendor specific

• Power Management


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Questions?

• Website– http://ofono.org

• Code– http://git.kernel.org/?p=network/ofono/ofono.git;a=summary

• Mailing List– [email protected]

• IRC– #ofono on freenode.net


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Legal Information

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Copyright © 2009, Intel Corporation. All rights are protected.

ofono – open source telephony june 2009 denis kenzior oscon 2009

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