While mobile phones made a significant evolution in recent years from single-purpose communication devices to multi-purpose devices, the fundamental design of phone call applications did not evolve accordingly. While its implementation leveraged from new hardware and software capabilities, the fundamental decisions people are able to make when they receive a call did not change. Currently, when a call comes in, a modal dialog opens where the callee can either decline or accept the call. A recent study found that the current user interfaces of phone call applications (phone UIs) often lead to an increased overhead when application usage is being interrupted by phone calls. In this paper, we revisit phone call UIs for multipurpose smartphones. We contribute a new design space for mobile phone call UIs, going beyond the simple accept-or-decline dilemma. We present a prototype implementation and discuss open challenges.

1. Problem and Idea
• Mobile phones evolved form single-purpose devices to multi-purpose devices
• The design of phone call applications did not evolve accordingly
• Incoming phone calls can interrupt concurrent application use
• We revise the design of call applications to allow for higher degree of multitasking
Matthias Böhmer - matthias.boehmer@dfki.de
Sven Gehring - sven.gehring@dfki.de
Jonas Hempel - jonashempel@gmail.com
Antonio Krüger - antonio.krueger@dfki.de
Extending Phone Call Applications
a) Current design: Full-screen modal dialogs providing only options to accept or decline call
b) Postponing calls: Additional third option besides accept/decline to allow user to return to previous application
c) Multiplexing: Allows user to keep attention in previous application while call is pending
d) Background notifications: Puts incoming call into background for user to pickup call at will
e) Scheduling on app completion: Wait until task is done and display call when user leaves previous app
Revisiting Phone Call UIs
for Multipurpose Mobile Phones
CALLER NAME CALLER NAME
CALLER NAME
Discussion, Challenges and Future Work
• A model for predicting overhead would allow to determine which option (b to e) to choose for handling calls
• When user is multitasking the caller needs to be kept in line, e.g. by signalling “user is currently writing a mail”
• Other modalities need to be taken into account (esp. vibration and ringtone) and aligned with visual notification
a) Current design b) Postponing calls c) Multiplexing d) Background notification
Prototype Implementation
• Android-based implementation of approach c)
• Available for study in the wild and testing
• Android App CallHeads
• http://goo.gl/hm43O4