Broadband Phone Technology
The Broadband Phone system combines two key underlying
technologies:
- Thin-client technology based on our
VNC system means that the Broadband
Phone is stateless—no important information is held in the
device. The phone simply displays graphics from the server and
sends back input from pen-strokes or finger-presses on the
screen. This is similar in concept to an existing phone; if it is
replaced with another one, the user doesn't lose their phone
number or access to any of their services. Compare that with the
applications and data on a home PC!
- SIP-based IP telephony
means that the Broadband Phone does not need to plug into a traditional
telephone line, but transmits voice in digital form over the
network. Signalling and advanced service provision is done
using SIP which is very
widely seen as the cornerstone of
next-generation communication services.
Other types of data can be sent alongside the voice so, for example,
users can share information or play an interactive game while
talking.
System Architecture
The Broadband Phone system consists of a central server (or server
cluster), a number of end user platforms (typically, but not
necessarily, Broadband Phones) and an optional gateway to the PSTN.
Because of our uncompromising thin-client approach, the central server
cluster hosts virtually all of the services, right down to the SIP User
Agents for each end user platform. Our servers are primarily Linux-based,
but the software can also run under Solaris or, without too much
modification, Windows NT.
An overview of the Broadband Phone system architecture is depicted in this
diagram.
Advantages of the Broadband Phone
The Broadband Phone has many advantages,
primarily owing to the thin client approach. For instance, it is:
- Reliable
- The phone itself is stateless, with no
application software to crash, no information to lose, and zero user
maintenance required. A new phone plugged in simply picks up where the old
one left off. Nothing is downloaded to the phone, so there is no risk of
viruses.
- Mobile
-
By this we mean cross-platform mobility rather than physical mobility.
Because the system is designed to interact
with the endpoint using very simple protocols, it can easily be retargeted
at different devices. When working
at home, your phone could take on all the facilities normally available at
your office. Your personal phone display could even be made to migrate to
your PC screen, to a callbox, or to your car dashboard. Of course,
as wireless networks proliferate and improve, your phone display could also
migrate to your wireless PDA in which case cross-platform mobility would
become physical mobility.
- Scalable
-
A major challenge in creating the Broadband
Phone architecture was to produce a system which could scale to millions of
users worldwide, and yet still be viable for a small
enterprise. The solution lies in the network-centric philosophy, which
brings an economy of scale through shared resources and centralised
management.
- Future proof
- Because the phone contains no web browser or
other applications, and because all data is kept by the service provider,
it never needs upgrading with new storage space or processors. The phone
simply reflects whatever applications are made available on the network,
where it is easy to change the software or hardware as required, for
instance to add a new application.
Why 'Broadband'?
- High-speed, or broadband, networks
are becoming the norm, to support the explosive growth in demand for the
exciting multimedia services available on the Internet. The Broadband
Phone system was designed with such networks in mind, where the maximum
benefit can be drawn from the radical thin-client approach. However,
the actual bandwidth required for the Broadband Phone varies with the
specific applications deployed. For multimedia-intensive applications
(e.g. video, high quality stereo audio, real-time interactive games, etc)
true broadband is required. In this case, the underlying broadband connection
might be Ethernet, cable modem, xDSL, or wireless. For other applications
(e.g. telephony, directories, web, email, etc) less powerful network connections
will suffice. These include ISDN or even dial-up over a standard
telephone line.
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