A Survey on Cloud Gaming: Future of Computer Games

Wei Cai, Ryan Shea, Chun-Ying Huang, Kuan-Ta Chen, Cheng-Hsin Hsu,
Jiangchuan Liu, and Victor C. M. Leung
Department of Electrical and Computer Engineering, University of British Columbia, Canada
School of Computing Science, Simon Fraser University, Canada
Department of Computer Science and Engineering, National Taiwan Ocean University, Taiwan
Institute of Information Science, Academia Sinica, Taiwan
Department of Computer Science, National Tsing Hua University, Taiwan

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1  Motivations

Cloud gaming refers to a new way to deliver computer games to users, where computationally complex games are executed on powerful cloud servers, the rendered game scenes are streamed over the Internet to gamers with thin clients on heterogeneous devices, and the control events from input devices are sent back to cloud servers for interactions. In late 2000's, we started to see cloud gaming services offered by startups, such as OnLive [1], Gaikai [2], and Ubitus [3]. We also witnessed that Gaikai was acquired by SONY, which is a major game console developer [4]. This was followed by the competition between Sony's PlayStation Now and NVIDIA's Grid Game Streaming Service, which further heats up the cloud gaming market. In fact, a 2014 report from Strategy Analytics [5] indicates that the number of cloud gaming users will increase from 30 million in 2014 to 150 million in 2015. The same report also predicts that other leading game console developers will soon join the cloud gaming market.
The tremendous popularity of cloud gaming can be attributed to several potential advantages to gamers, game developers, and service providers. For gamers, cloud gaming enables them to: (i) have access to their games anywhere and anytime, (ii) purchase or rent games on-demand, (iii) avoid regularly upgrading their hardware, and (iv) enjoy unique features such as migrating across client computers during game sessions, observing ongoing tournaments, and sharing game replays with friends. For game developers, cloud gaming allows them to: (i) concentrate on a single platform, which in turn reduces the porting and testing costs, (ii) bypass retailers for higher profit margins, (iii) reach out to more gamers, and (iv) avoid piracy as the game software is never downloaded to client computers. For service providers, cloud gaming: (i) leads to new business models, (ii) creates more demands on already-deployed cloud resources, and (iii) demonstrates the potential of other/new remote execution applications, since cloud gaming imposes the strictest constraints on various computing and networking resources.
Despite the great opportunities of cloud gaming, several crucial challenges must be addressed by the research community before it reaches its full potentials to attract more gamers, game developers, and service providers. First, cloud gaming platforms and testbeds must be built up for comprehensive performance evaluations. The evaluations include measurements on Quality of Service (QoS) metrics, such as energy consumption and interaction latency, and Quality of Experience (QoE) metrics, such as gamer perceived gaming experience. Building platforms and testbeds, designing the test scenarios, and carrying out the evaluations, require significant efforts, while analyzing the complex interplay between QoS and QoE metrics is even more difficult. Second, the resulting platforms and evaluation procedures allow the research community to optimize various components, such as cloud servers and communication channels. More specifically, optimization techniques for better resource allocation and distributed architecture are possible at cloud servers, and optimal content coding and adaptive transmissions are possible in the communication channels. Indeed, more and more research papers aim to address these and other challenges. Nonetheless, to the best of our knowledge, there is no comprehensive survey on cloud gaming research. This may delay or even prevent researchers, who are interested in cloud gaming or other remote execution applications, from joining the community.

2  Scope and Tentative Organization

We plan to survey the cloud gaming literature using the following classifications.
  1. Cloud Gaming Overview: We survey the overview, introductory, and positioning papers on either general cloud gaming, or specialized topics, such as mobile cloud gaming and Game-as-a-Service (GaaS).
  2. Cloud Gaming Platforms: We consider papers that construct basic cloud gaming platforms, which support different performance evaluation methodologies. These studies can be further categorized into three groups: system integration, QoS evaluations, and QoE evaluations.
    1. System Integration: The fundamental step of cloud gaming research, like many other systems areas, is to put up basic platforms, based on existing tools. We summarize such system integration efforts, which serve as cornerstones of related research.
    2. Quality of Service Evaluations: We survey the studies on objective metric evaluations, which algorithmically quantify the system performance, i.e., without subject assessments. Existing papers focus on two objective metrics, Energy Consumption and Interaction Delay. The energy consumption is critical to mobile cloud gaming clients, in order to prolong the precious battery life. The interaction latency refers to the time difference between a user input and the corresponding game scene update on the client computer. Because gamers are highly sensitive to interaction latency [6], its measurement methodologies draw a lot of attentions in the literature.
    3. Quality of Experience Evaluations: We discuss the papers on subjective metric evaluations, which are based on user studies, where subject gamers give opinion scores to their cloud gaming experience. Conducting user studies is inherently expensive and tedious, and thus most QoE studies attempt to derive analytical models between the QoS and QoE metrics. The resulting models may in turn be used to optimize cloud gaming platforms.
  3. Optimizing Cloud Gaming Platforms: We consider papers that optimize cloud gaming platforms from specific aspects; usually each work focuses on optimizing one or a few components. Such studies can be further categorized into two groups: cloud server infrastructure and communications.
    1. Cloud Server Infrastructure: The existing studies on optimizing cloud server infrastructure are surveyed. Several papers study the Resource Allocation problem of server and network resources among multiple data center, server nodes, and gamers to optimize the overall cloud gaming experience, where diverse criteria are considered. Other papers optimize the Distributed Architectures of cloud gaming platforms, e.g., using Peer-to-Peer (P2P) overlays or multi-tier clouds for better performance and scalability.
    2. Communications: We survey the existing work on optimizing the efficiency of content streaming over the dynamic and heterogeneous communication channels. These studies are further classified into two groups. First, several papers consider the problem of Data Compression, e.g., layered coding and graphics compression are proposed, which may outperform the conventional 2D image compression in certain environments. Second, there are papers on Adaptive Transmissions, which cope with the network dynamics by continuously changing various parameters, such as encoding bitrate, frame rate, and image resolution. The same adaptive transmissions may also be used to absorb the negative impacts due to insufficient resources on cloud servers and game clients.
  4. Development, Deployment, and Other Concerns: We survey the development environments, deployments and other concerns. For example, short history of cloud gaming industry is presented and the current cloud gaming services are detailed.
The proposed article not only surveys the state-of-the-art cloud gaming research, but also reveals the opportunities for further research. The lessons learned when developing cloud gaming platforms and optimizing cloud gaming experience are also useful for other remote execution applications with strict real-time requirements. Last, our discussions on practical issues are useful to cloud gaming practitioners.

3  Short Author Biographies

Ryan Shea [S'08] received the B.Sc. degree in computer science from Simon Fraser University, Burnaby, BC, Canada, in 2010, where he is currently pursuing the Ph.D. degree with the Network Modeling Laboratory, and received the Certificate in University Teaching and Learning from the same university. He has been a Network Administrator with various nonprofit groups. His current research interests include computer and network virtualization, and performance issues in cloud computing. Mr. Shea received the Best Student Paper Award at IEEE/ACM IWQoS'2012.
Wei Cai [S'12] is a PhD candidate in the Department of Electrical and Computer Engineering at the University of British Columbia, Canada. His research areas include gaming as a service, mobile cloud computing, quality of experience and software engineering. Cai received an MSc in electrical engineering and computer science from Seoul National University, Korea. He is a co-recipient of the IEEE CloudCom Best Paper Award 2014, SmartComp Best Paper Award 2014, and CloudComp Best Paper Award 2013.
Chun-Ying Huang [S'03, M'08] is an Associate Professor at the Department of Computer Science and Engineering, National Taiwan Ocean University. He received his B.S. in Computer Science from National Taiwan Ocean University in 2000 and M.S. in Computer Information Science from National Chiao Tung University in 2002. Dr. Huang received his Ph.D. in Electrical Engineering Department from National Taiwan University in 2007. His researches focus on computer network and network security issues, including traffic measurement and analysis, malicious behavior detection, and multimedia networking systems. Dr. Huang is a member of ACM, CCISA, IEEE, and IICM.
Kuan-Ta Chen (a.k.a. Sheng-Wei Chen) [S'04, M'06] is a Research Fellow at the Institute of Information Science and the Research Center for Information Technology Innovation (joint appointment) of Academia Sinica. Dr. Chen received his Ph.D. in Electrical Engineering from National Taiwan University in 2006, and received his B.S. and M.S. in Computer Science from National Tsing-Hua University in 1998 and 2000, respectively. His research interests include quality of experience, multimedia systems, and social computing. He has been an Associate Editor of IEEE TRANSACTIONS ON MULTIMEDIA since 2011. He is a member of ACM, IEEE, IICM, and CCISA.
Cheng-Hsin Hsu [S'09, M'10] received his Ph.D. degree from Simon Fraser University, M.Eng. degree from University of Maryland, and M.S./B.S. degrees from National Chung-Cheng University. He is an Associate Professor at Department of Computer Science in National Tsing Hua University since 2014, and was an Assistant Professor at the same department between 2011 and 2014. Before that, he was with Deutsche Telekom Lab, Motorola Inc., and Lucent Technologies. He was a Visiting Assistant Researcher at University of California, Irvine and a Visiting Research Consultant at Qatar Computing Research Institute in Summer 2013 and 2014, respectively. His research interests are in multimedia networking, mobile computing, and computer networks. He has been served as an Associate Editor for ACM Transactions on Multimedia Computing, Communications, and Applications (TOMM) since January 2014, and for IEEE MMTC E-Letter between 2012 and 2014. He was on the ACM SIGMM History Preservation Committee between 2010 and 2014, and on the IEEE MMTC Review Board Committee between 2010 and 2012. He and his colleagues won the Best Paper Award at IEEE RTAS'12, TAOS Best Paper Award at IEEE GLOBECOM'12, Best Paper Award at IEEE Innovation'08, and Best Demo Award at ACM Multimedia'08.
Jiangchuan Liu [S'01, M'03, SM'08] is a Full Professor in the School of Computing Science, Simon Fraser University, British Columbia, Canada, and an EMC-Endowed Visiting Chair Professor at Tsinghua University, Beijing, China (2013–2016). He is a corecipient of the ACM TOMCCAP Nicolas D. Georganas Best Paper Award 2013, ACM Multimedia Best Paper Award 2012, IEEE Globecom 2011 Best Paper Award, and IEEE Communications Society Best Paper Award on Multimedia Communications 2009. His research interests include multimedia systems and networks, cloud computing, social networking, online gaming, big data computing, wireless sensor networks, and peer-to-peer and overlay networks.
Victor C. M. Leung [S'75, M;89, SM'97, F'03] is a Professor of Electrical and Computer Engineering and holder of the TELUS Mobility Research Chair at the University of British Columbia (UBC). His research is in the areas of wireless networks and mobile systems. He has co-authored more than 800 technical papers in archival journals and refereed conference proceedings, several of which had won best-paper awards. Dr. Leung is a Fellow of IEEE, a Fellow of the Royal Society of Canada, a Fellow of the Canadian Academy of Engineering and a Fellow of the Engineering Institute of Canada. He is serving or has served on the editorial boards of JCN, IEEE JSAC, Transactions on Computers, Wireless Communications, and Vehicular Technology, Wireless Communications Letters, and several other journals. He has provided leadership to the technical program committees and organizing committees of numerous international conferences. Dr. Leung was the recipient of the 1977 APEBC Gold Medal, NSERC Postgraduate Scholarships from 1977-1981, a 2012 UBC Killam Research Prize, and an IEEE Vancouver Section Centennial Award.

References

[1] "OnLive web page," January 2015, http://www.onlive.com/.
[2] "GaiKai web page," January 2015, http://www.gaikai.com/.
[3] "Ubitus web page," January 2015, http://www.ubitus.net.
[4] "Cloud gaming adoption is accelerating ... and fast!" July 2012, http://www.nttcom.tv/2012/07/09/cloud-gaming-adoption-is-acceleratingand-fast/.
[5] "Cloud gaming to reach inflection point in 2015," November 2014, http://tinyurl.com/p3z9hs2.
[6] M. Claypool and K. Claypool, "Latency and Player Actions in Online Games," Communications of the ACM, vol. 49, no. 11, pp. 40-45, Nov. 2006.


Sheng-Wei Chen (also known as Kuan-Ta Chen)
http://www.iis.sinica.edu.tw/~swc 
Last Update September 19, 2017