Sasa Junuzovic

IllumiShare: sharing any surface

Task and reference spaces are important communication channels for remote collaboration. However, all existing systems for sharing these spaces have an inherent weakness: they cannot share arbitrary physical and digital objects on arbitrary surfaces. We present IllumiShare, a new cost-effective, light-weight device that solves this issue. It both shares physical and digital objects on arbitrary surfaces and provides rich referential awareness. To evaluate IllumiShare, we studied pairs of children playing remotely. They used IllumiShare to share the task-reference space and Skype Video to share the person space. The study results show that IllumiShare shared the play space in a natural and seamless way. We also found that children preferred having both spaces compared to having only one. Moreover, we found that removing the task-reference space caused stronger negative disruptions to the play task and engagement level than removing the person space. Similarly, we found that adding the task-reference space resulted in stronger positive disruptions.

Requirements and recommendations for an enhanced meeting viewing experience

We have found that viewing recorded meetings using traditional meeting viewers whose interfaces consist of an automatic speaker and a fixed context view does not provide sufficient information and control to the users. In particular, a survey of users who watch meeting recordings on a regular basis revealed that it is also useful to provide (1) speaker-related information, including who the speaker is talking to, looking at, and being interrupted by, and (2) more control of the interface, including changing the relative sizes of the speaker and context views and navigating within the context view. We present a 3D interface prototype designed specifically to meet these requirements when viewing recorded meetings. We describe in detail the results of a user study comparing the effectiveness of the new and traditional style interfaces with respect to these requirements. Based on this study, we present a set of guidelines for future interfaces.

Read, write, and navigation awareness in realistic multi-view collaborations

Read, write, and navigation awareness allow users of a multi-view collaborative editor to get fine-grained information about whether others are reading what they are editing, where others are editing, and to which areas of the document others have navigated, respectively. We derive new high-level tools that directly support the three kinds of awareness. The results of a decision-making study involving the use of these tools revealed that write awareness helps with fine-grained conflict prevention, read awareness reduces unnecessary verbal communication, and navigation awareness is most effective when coupled with read and write awareness. Thus, the study identifies specific uses of the three forms of awareness and motivates tools for supporting them.

What did i miss?: in-meeting review using multimodal accelerated instant replay (air) conferencing

People sometimes miss small parts of meetings and need to quickly catch up without disrupting the rest of the meeting. We developed an Accelerated Instant Replay (AIR) Conferencing system for videoconferencing that enables users to catch up on missed content while the meeting is ongoing. AIR can replay parts of the conference using four different modalities: audio, video, conversation transcript, and shared workspace. We performed two studies to evaluate the system. The first study explored the benefit of AIR catch-up during a live meeting. The results showed that when the full videoconference was reviewed (i.e., all four modalities) at an accelerated rate, users were able to correctly recall a similar amount of information as when listening live. To better understand the benefit of full review, a follow-up study more closely examined the benefits of each of the individual modalities. The results show that users (a) preferred using audio along with any other modality to using audio alone, (b) were most confident and performed best when audio was reviewed with all other modalities, (c) compared to audio-only, had better recall of facts and explanations when reviewing audio together with the shared workspace and transcript modalities, respectively, and (d) performed similarly with audio-only and audio with video review.

Response times in N-user replicated, centralized, and proximity-based hybrid collaboration architectures

We evaluate response times, in N-user collaborations, of the popular centralized (client-server) and replicated (peer-to-peer) architectures, and a hybrid architecture in which each replica serves a cluster of nearby clients. Our work consists of definitions of aspects of these architectures that have previously been unspecified but must be resolved for the analysis, a formal evaluation model, and a set of experiments. The experiments are used to define the parameters of and validate the formal analysis. In addition, they compare the performances, under the three architectures, of existing data-centric, logic-centric, and stateless shared components. We show that under realistic conditions, a small number of users, high intra-cluster network delays, and large output processing and transmission costs favor the replicated architecture, large input size favors the centralized architecture, high inter-cluster network delays favor the hybrid architecture, and high input processing and transmission costs, low think times, asymmetric processing powers, and logic-intensive applications favor both the centralized and hybrid architectures. We use our validated formal model to make useful predictions about the performance of the three kinds of architectures under realistic scenarios we could not create in lab experiments.

AIR conferencing: accelerated instant replay for in-meeting multimodal review

When people attend meetings they may miss parts of the discussion if they, for example, step out to take a phone call, go to the bathroom, or have a momentary lapse in concentration. As a result, they may need to catch up on what they missed upon returning to the meeting. Asking other attendees for a recap is often disruptive. To avoid such disruptions, we have developed an Accelerated Instant Replay (AIR) Conferencing system for videoconferencing that enables participants to privately catch up to an ongoing meeting. We explored several mechanisms where the meeting content is replayed at an accelerated rate so that the participants can catch up to the live discussion reasonably quickly.

Formally analyzing two-user centralized and replicated architectures

We have developed a formal performance model for centralized and replicated architectures involving two users, giving equations for response, feedthrough, and task completion times. The model explains previous empirical results by showing that (a) low network latency favors the centralized architecture and (b) asymmetric processing powers favor the centralized architecture. In addition, it makes several new predictions, showing that under certain practical conditions, (a) centralizing the application on the slower machine may be the optimal solution, (b) centralizing the application on the faster machine is sometimes better than replicating, and (c) as the duration of the collaboration increases, the difference in performances of centralized and replicated architectures gets magnified. We have verified these predictions through new experiments for which we created synthesized logs based on parameters gathered from actual collaboration logs. Our results increase the understanding of centralized and replicated architectures and can be used by (a) users of adaptive systems to decide when to perform architecture changes, (b) users who have a choice of systems with different architectures to choose the system most suited for a particular collaboration mode (defined by the values of the collaboration parameters), and (c) users locked into a specific architecture to decide how to change the hardware and other collaboration parameters to improve performance.

Lazy scheduling of processing and transmission tasks in collaborative systems

A collaborative system must perform both processing and transmission tasks. We present a policy for scheduling these tasks on a single core that is inspired by studies of human perception and the real-time systems field. It lazily delays the execution of the processing task if the delay cannot be noticed by humans. We use simulations and formal analysis to compare this policy with previous scheduling policies. We show that the policy trades-off an unnoticeable degradation in performance of some users for a much larger noticeable improvement in performance of others.

Multicasting in groupware

While multicast has been studied extensively in many domains such as content streaming and file sharing, there is little research applying it to synchronous collaborations involving shared access to a distributed object. Based on several cases of real-world collaborations involving instant messaging, distributed lectures, and computationally-intensive collaborative game playing, we show that compared to traditional centralized and replicated collaboration architectures, a new bi-architecture collaboration system model with multicasting support can improve response, feedthrough, and task completion times. In addition, we show that to optimize performance, the set of traditionally considered factors, consisting of network delays and transmission costs, must be expanded to include several new factors, such as processing costs, scheduling policies, and think times. In one or more of the real-world collaborations we consider, we show that multicast (a) can increase feedthrough times if processing costs and scheduling policies are not considered and (b) may degrade or improve task completion times depending on the cost of computing the multicast overlay.

Scheduling in variable-core collaborative systems

The performance of a collaborative system depends on how two mandatory collaborative tasks, processing and transmission of user commands, are scheduled. We have developed multiple policies for scheduling these tasks on computers that have (a) one processing element on the network interface card and (b) one or more processing cores on the CPU. To compare these policies, we have a developed a formal analytical model that predicts their performance. It shows that the optimal scheduling policy depends on several factors including the number of cores that is available. We have implemented a system that supports all of the policies and performed experiments to validate the formal model. This system is a component of a self-optimizing scheduler we have developed that improves response times by automatically choosing the scheduling policy based on number of cores and other factors.