Requests for communication via mobile devices can be disruptive to the current task or social situation. To reduce the frequency of disruptive requests, one promising approach is to provide callers with cues of a receiver's context through an awareness display, allowing informed decisions of when to call. Existing displays typically provide cues based on what can be readily sensed, which may not match what is needed during the call decision process. In this paper, we report results of a four week diary study of mobile phone usage, where users recorded what context information they considered when making a call, and what information they wished others had considered when receiving a call. Our results were distilled into lessons that can be used to improve the design of awareness displays for mobile devices, e.g., show frequency of a receiver's recent communication and distance from a receiver to her phone. We discuss technologies that can enable cues indicated in these lessons to be realized within awareness displays, as well as discuss limitations of such displays and issues of privacy.  The rapid proliferation of mobile communication devices such as cell phones has enabled ubiquitous communication among family, friends, and colleagues. This has obvious benefits, but receiving requests for communication at inopportune moments can be very disruptive to the current task [33] or social situation [2, 33] . To identify suitable moments for initiating communication, callers must be able to balance their need for communication with the receivers' need to remain engaged in the task or social situation. Existing mechanisms for maintaining this balance include allowing receivers to choose among many notification modalities such as ring tones and ring styles (e.g., audio, vibrate, silent) or by leveraging the caller-id function. However, these mechanisms are receiver-oriented -the receiver is forced to decide whether or not to accept a call in advance without knowing the caller's purpose. Enabling callers to push more context information (e.g., text messages indicating purpose) to the receiver offers one possible solution, as it would allow a receiver to make a more informed decision of whether to accept the call. However, the explicit effort required by the caller (entering the message) and imposed on the receiver (reading and interpreting the message) may outweigh any increase in the receiver's ability to moderate incoming calls. A promising alternative is to develop communication-oriented awareness displays that provide a caller with cues of the receiver's context (e.g., see [13, 18, 21, 34] ), allowing the caller to make a more informed decision of whether now is an appropriate time to call. A compelling benefit of this approach is that it maintains the balance in effort between caller and receiver in the call initiation process. For example, a caller can consult the awareness display to decide whether to initiate the request, while a receiver may use notification modalities or caller-id to decide whether to accept. Existing awareness displays typically provide callers with context information that can be readily sensed (e.g., presence, schedule, conversation, etc.) [4, 13, 18, 34] ; which may not match what is actually needed during the call initiation process. Studies confirm that callers will indeed utilize context information to coordinate their communication requests [2, 11] , but, similarly, these studies have only considered context information that could be readily sensed or was otherwise believed to be important. As a result, there is still not adequate understanding of what range of context information should be included within awareness displays for communication devices such as mobile phones. In this paper, we report the results of a four week diary study of mobile phone usage, where users recorded in situ what context information they considered when deciding whether to initiate a call (caller perspective), and what information they wished callers had considered before calling them (receiver perspective). Use of this particular research method allowed us to gain access to users' ongoing thought processes during everyday life situations [6] . Our study focused on the use of mobile devices due to their prevalence and because communication requests from these devices are often disruptive to our daily tasks and social situations [32] . Results from our study provide further insight into what types of context information is needed during the call initiation process. For example, our more surprising findings included that the frequency of a receiver's recent communication and distance from receiver to their phone were often considered in the call initiation process, yet are not provided in existing awareness displays. We distill our findings into a set of design lessons that can be leveraged to improve the design of awareness displays for mobile devices. By citing existing and forthcoming technologies, we also describe realistic techniques that could be used to sense much of the context information indicated in our lessons. Finally, we present evidence from our study highlighting potential limitations of using awareness displays and user concerns of privacy. In this section, we describe costs of interruption caused by mobile devices, techniques for coordinating communication, and how our work differs from other studies of telecommunications devices. The rapid proliferation of mobile devices has made people more accessible for communication. This offers incredible convenience,
The reason is that the incoming call is welcome for someone as it provides a mental break from the current task which is needed for her REF .
Should I call now? understanding what context is considered when deciding whether to initiate remote communication via mobile devices
GI '07
Computer Science