Teemu Kämäräinen

Towards pervasive and mobile gaming with distributed cloud infrastructure

Cloud gaming, where the game is rendered in the cloud and is streamed to an end-user device through a thin client, is rapidly gaining ground. Latency is still a key challenge to cloud gaming: highly interactive games can become unplayable even with response delays below 100 ms. To overcome this issue, we propose to deploy gaming services on a more distributed cloud infrastructure, and to instantiate gaming servers in close proximity of the user when necessary in order to shorten the response delay. Our prototype distributed cloud gaming platform also allows flexible configuration of gaming controls and video streams, enabling the use of public displays in mobile cloud gaming. We test our prototype with two games in different deployment scenarios, and measure the response delay and power consumption of the mobile devices. Our experiment results confirm that it is feasible to improve the quality of gaming experience through the deployment strategies provided by the proposed system.

A First Look at Quality of Mobile Live Streaming Experience: the Case of Periscope

Live multimedia streaming from mobile devices is rapidly gaining popularity with services such as Periscope, Meerkat, and Facebook Live. However, little is known about their anatomy. In order to shed light on this matter, we examine the Periscope service. We first crawl the service to understand its usage patterns and then perform an in-depth analysis of its salient features. In particular, we study the protocols and adaptation strategies involved, the typical quality of experience indicators, such as playback smoothness and latency, video quality, and their influencing factors. Finally, we report on the energy consumption of the application.Live multimedia streaming from mobile devices is rapidly gaining popularity but little is known about the QoE they provide. In this paper, we examine the Periscope service. We first crawl the service in order to understand its usage patterns. Then, we study the protocols used, the typical quality of experience indicators, such as playback smoothness and latency, video quality, and the energy consumption of the Android application.

Dissecting the End-to-end Latency of Interactive Mobile Video Applications

In this paper we measure the step-wise latency in the pipeline of three kinds of interactive mobile video applications that are rapidly gaining popularity, namely Remote Graphics Rendering (RGR), Mobile Augmented Reality (MAR), and Mobile Virtual Reality (MVR). The applications differ from each other by the way in which the user interacts with the application, i.e., video I/O and user controls, however in all the user experience is highly sensitive to end-to-end latency. Long latency between a user control event and display update renders the application unusable. Hence, understanding the nature and origins of latency of these applications is of paramount importance. We show through extensive measurements that control input and display buffering have a substantial effect on the overall delay. Our results shed light on the latency bottlenecks and the maturity of technology for seamless user experience with these applications.

Performance evaluation of remote display access for mobile cloud computing

Mobile applications are increasingly exploiting cloud computing to overcome the resource limitations of mobile devices. To this end, the most computationally expensive tasks are offloaded to the cloud and the mobile application simply interacts with a remote service through a network connection. One way to establish such a connection is given by remote display access, in which a mobile device just operates as a thin client by relaying the input events to a server and updating the screen based on the content received. In this article, we specifically address remote display access as a means for mobile cloud computing, with focus on its power consumption at mobile devices. Different from most of the existing literature, we take an experimental approach based on real user sessions employing different remote access protocols and types of applications, including gaming. Through several experiments, we characterize the impact of the different protocols and their features on power consumption and network utilization. We conclude our analysis with considerations on usability and user experience.

Exploring Vision-Based Techniques for Outdoor Positioning Systems: A Feasibility Study

Recent advances from wearables have significantly changed the way how humans communicate with the surrounding environment. To some extent, they have extended and augmented the capability of humans. For example, with a Google Glass, people can take pictures simply by winking eyes twice, which releases human hands from the cumbersome image-taking process. Thus, it enables new application scenarios that were not possible before. In this paper, we investigate utilizing vision-based techniques to provide a wearable positioning system. Specifically, we propose a Human-centric Positioning System (HoPS) that utilizes traffic signposts together with context information for real-time positioning. Towards that direction, we make three primary contributions: (1) we make several important observations that guide our design of HoPS system; for example, we find out that approximately 40 percent of traffic signposts monopolize a cell tower, and there are at most six signposts within the coverage of a single cell tower; (2) we investigate the impact factors of object detection success rate, and find its correlation with image quality, and resolution; and (3) we design and implement HoPS and an advanced version of HoPS based on additional context information from Wi-Fi network, which we name HoPS-WiFi. Experimental results demonstrate the effectiveness of HoPS, especially HoPS-WiFi, which can estimate the relevant location correctly within 1.3 seconds.

A Measurement Study on Achieving Imperceptible Latency in Mobile Cloud Gaming

Cloud gaming is a relatively new paradigm in which the game is rendered in the cloud and is streamed to an end-user device through a thin client. Latency is a key challenge for cloud gaming. In order to optimize the end-to-end latency, it is first necessary to understand how the end-to-end latency builds up from the mobile device to the cloud gaming server. In this paper we dissect the delays occurring in the mobile device and measure access delays in various networks and network conditions. We also perform a Europe-wide latency measurement study to find the optimal server locations and see how the number of server locations affects the network delay. The results are compared to limits found for perceivable delays in recent human-computer interaction studies. We show that the limits can be achieved only with the latest mobile devices with specific control methods. In addition, we study the expected latency reduction by near future technological development and show that its potential impact is bigger on the end-to-end latency than that of replication of the service and server placement optimization.

Latency and throughput characterization of convolutional neural networks for mobile computer vision

We study performance characteristics of convolutional neural networks (CNN) for mobile computer vision systems. CNNs have proven to be a powerful and efficient approach to implement such systems. However, the system performance depends largely on the utilization of hardware accelerators, which are able to speed up the execution of the underlying mathematical operations tremendously through massive parallelism. Our contribution is performance characterization of multiple CNN-based models for object recognition and detection with several different hardware platforms and software frameworks, using both local (on-device) and remote (network-side server) computation. The measurements are conducted using real workloads and real processing platforms. On the platform side, we concentrate especially on TensorFlow and TensorRT. Our measurements include embedded processors found on mobile devices and high-performance processors that can be used on the network side of mobile systems. We show that there exists significant latency-throughput trade-offs but the behavior is very complex. We demonstrate and discuss several factors that affect the performance and yield this complex behavior.

CloudVR: Cloud Accelerated Interactive Mobile Virtual Reality

High quality immersive Virtual Reality experience currently requires a PC setup with cable connected head mounted display, which is expensive and restricts user mobility. This paper presents CloudVR which is a system for cloud accelerated interactive mobile VR. It is designed to provide short rotation and interaction latencies through panoramic rendering and dynamic object placement. CloudVR also includes rendering optimizations to reduce server-side computational load and bandwidth requirements between the server and client. Performance measurements with a CloudVR prototype suggest that the optimizations make it possible to double the servers framerate and halve the amount of bandwidth required and that small objects can be quickly moved at run time to client device for rendering to provide shorter interaction latency. A small-scale user study indicates that CloudVR users do not notice small network latencies (20ms) and even much longer ones (100-200ms) become non-trivial to detect when they do not affect the interaction with objects. Finally, we present a design of CloudVR extension to multi-user scenarios.

Can You See What I See? Quality-of-Experience Measurements of Mobile Live Video Broadcasting

Broadcasting live video directly from mobile devices is rapidly gaining popularity with applications like Periscope and Facebook Live. The quality of experience (QoE) provided by these services comprises many factors, such as quality of transmitted video, video playback stalling, end-to-end latency, and impact on battery life, and they are not yet well understood. In this article, we examine mainly the Periscope service through a comprehensive measurement study and compare it in some aspects to Facebook Live. We shed light on the usage of Periscope through analysis of crawled data and then investigate the aforementioned QoE factors through statistical analyses as well as controlled small-scale measurements using a couple of different smartphones and both versions, Android and iOS, of the two applications. We report a number of findings including the discrepancy in latency between the two most commonly used protocols, RTMP and HLS, surprising surges in bandwidth demand caused by the Periscope app’s chat feature, substantial variations in video quality, poor adaptation of video bitrate to available upstream bandwidth at the video broadcaster side, and significant power consumption caused by the applications.