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\markboth{E*phone (Sprint) -- Proprietary and Confidential}{E*phone
(Sprint) -- Proprietary and Confidential}

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\title{E*phone (Sprint)}
\author{Henning Schulzrinne}
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\section{Introduction}

This document describes the overall hardware and software architecture of
the e*phone, and its integration into the Sprint WAP architecture. The
hardware design is likely to see two versions. The first one, called 2.3,
is based on the currently available prototype, shown in
Fig.~\ref{fig:ephone_wap}. This device has the following features:

\begin{itemize}
\item SIP/RTP-compliant Internet device;
\item 10 Mb/s Ethernet interface;
\item optically isolated digital input for sensors such as alarms or
IR presence;
\item 16-bit stereo audio codec, with ability to configure one stereo
input as an analog sensor input;
\item all aspects automatically configured via DHCP;
\item automatic time synchronization (no blinking 12:00\ldots).
\end{itemize}

A future version of the hardware will likely have the following
additional characteristics:
\begin{itemize}
\item higher integration, resulting in lower hardware cost;

\item larger LCD (touch) screen, subject to cost constraints;

\item USB interface for connection of keyboards and possibly video
input;

\item possibly a DAA to allow use on analog phone lines in addition to
Ethernet.
\end{itemize}

A wireless portable device, suitable as a replacement for a cordless
phone for use in Wi-Fi (IEEE 802.11) home networks, is also planned, based on
the same hardware design.

\section{WAP Operation}

WAP is motivated by two limitations of wireless devices, their small
screen and the extremely limited access bandwidth.  The latter
restriction does not apply here, but the screens available on desk
phones are likely to be just as small in many cases as those on cell
phones, primarily for reasons of cost.  Thus, in our architecture we
avoid the complexity of implementing WAP in the e*phone.  Instead, a WAP
proxy translates the WAP protocol stack, including WML and WMLscript, to
a simple ``terminal'' interface, i.e., the 64-character display on the
e*phone and the key press indications from the e*phone.  Each display
update and keystroke is transmitted as a single SIP {\MESSAGE}
request\footnote{This is only marginally less efficient than traditional
telnet usage.}.

\ps{\textwidth}{!}{ephone_wap}{E*phone with WAP capability}

By default, the e*phone transmits SIP {\MESSAGE} messages to its
designated SIP proxy, which then routes them to a SIP-WAP gateway. 
Alternatively, the messages can be exchanged directly between the
SIP-WAP gateway and the e*phone.  The gateway or the server can also
send idle messages to the e*phone, which are displayed when no call is
in progress, with the ability of the user to select, for example, the
service advertised.  By using the SIP third-party mechanism
\cite{draft-rosenberg-sip-3pcc} or PINT (a SIP profile) \cite{rfc2848},
voice calls can be directly established to the advertiser.

Just like web browsers have bookmarks, it is also possible to provide a
similar functionality in the e*phone. We intend to provide the ability
to have the SIP server upload user agent configuration information in
the SIP {\REGISTER} response that configures the speed dial buttons. The
e*phone has 15 such buttons, so that, with a ``shift'' key, about 30
URLs can be pre-programmed, consisting of any mixture of SIP URLs or WAP
pages.

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