Session Initiation Protocol (SIP)

The Session Initiation Protocol (SIP) has been widely adopted for Instant Messaging (IM) and VoIP telephony both by the enterprise and in service provider systems. Till now, SIP functionality has been accessible to endusers primarily via computing platforms such as an IM client on a laptop or on communication platforms such as an IP Phone or a cell phone. We show that wearable devices such as the IBM Linux Watch (WatchPadTM) can play a powerful role as a control device in a SIP infrastructure, given their easily accessible, always available, and visible user-interfaces. We have designed and prototyped several key control applications, using a SIP User Agent on the WatchPad, such as the ability to initiate and route incoming and outgoing phone calls, receive simple queries as Instant Messages, and call initiation based on address books residing on wearable devices.

An interesting feature of SIP is the ability to separate the control and media portions of a connection. In fact, they may take place at different devices. Thus SIP allows a level of indirection and late binding of the media device. This is a powerful concept and has the potential to do for communications what pointers did for programming by separating data from addresses and virtual memory did for large programs by creating virtual addresses to overcome limits of real addresses. Since the ability to exercise control places very few requirements on end devices, it is possible to make wearable devices with a TCP/IP stack part of the SIP infrastructure. We argue that wearable computers are ideally suited for setting up sessions because of their availability and ability to get the user’s attention in varied situations. Wearable computers also contain information that can be used to personalize and improve the user experience. Similarly stationary devices are better suited to play the media because they have fewer constraints in terms of power, size, networking, etc. The above balance is unlikely to change because it is based on human behavior patterns and basic physics. Our investigation and implementation shows that wearable devices can plug an important gap and significantly enhance user experience. Power can be saved on mobile devices by transferring calls to stationary wired devices.

The WatchPad behaves as a control point for all user communications. Examples that we have implemented include

1) Initiate phone calls between stationary devices. 2) Transfer an incoming phone call to a nearby stationary device. 3) Transfer an ongoing phone call from a stationary device on to a mobile device.

The WatchPad does not handle media Media is handled by an infrastructure device, such as a desktop phone. The figures below shows the WatchPad setting up a call between two stationary phones and then transferring the call to the user's mobile phone.

More details can be found in

Unleashing the power of wearable devices in a SIP infrastructure, Arup Acharya, Stefan Berger, Chandra Narayanaswami, Proc of IEEE PerCom 2005, pp. 159-168. Extended version invited for publication in Elsevier Pervasive and Mobile Computing Journal.

Page was last updated on May, 2005.