Zengbin Zhang, University of California, Santa Barbara;
David Chu, Microsoft Research;
Xiaomeng Chen, University of Science and Technology of China;
Thomas Moscibroda, Microsoft Research Asia;
Mobile gaming is a big driver of app marketplaces. However, few mobile games deliver truly distinctive gameplay experiences for ad hoc collocated users. As an example of such an experience, consider a sword fight dual between two users facing each other where each user's phone simulates a sword. With phone in hand, the users' thrusts and blocks translate to attacks and counterattacks in the game. Such Phone-to-Phone Mobile Motion Games (MMG) represent interesting and novel gameplay for ad hoc users in the same location. One enabler for an MMG game like sword fight is continuous, accurate distance ranging. Existing ranging schemes cannot meet the stringent requirements of MMG games: speed, accuracy and noise robustness. In this work, we design FRA, a new ranging scheme that can localize at 12Hz with 2cm median error while withstanding up to 0dB noise, multipath and Doppler effect issues. Our implementation runs on commodity smartphones and does not require any external infrastructure. Moreover, distance measurement accuracy is comparable to that of Kinect, a fixed-infrastructure motion capture system. Evaluation on users playing two prototype games indicate that FAR can fully support dynamic game motion in real-time.
Paper is online at http://www.cs.ucsb.edu/~zengbin/files/swordfight-mobisys12.pdf
A demo video of SwordFight can be found at http://research.microsoft.com/en-us/projects/mobile-motion-gaming/
Public Review uploaded by MonicaLam:
This public review was prepared by Monica Lam.
This is a very interesting paper, one that even the general public may find appealing, as it introduces a new genre of game play dubbed Phone-to-Phone Motion Mobile Games (MMG). The underlying technology is a fast and accurate phone-to-phone acoustic based ranging system. Unlike the Wii and Kinect, this genre of games can be played with just commodity phones, making such games much more widely portable and accessible. Phone-to-phone locational gaming has previously been proposed, but this is the first paper that demonstrates the feasibility of this game play model.
Besides being well motivated, this is also an excellent system paper. It identifies accurate range finding as the core technical challenge, characterizes it, proposes a solution, and measures the results. The key insight behind the efficient range finding algorithm is to first use autocorrelation to narrow down a window to execute cross-correlation. Pipelining is also introduced to reduce the latency of the algorithm. It presents two original games built on the range-finding primitive. For comparison, it shows that the research prototype outperforms Kinect, a commercial game system. More impressively, the games are well developed enough to be played for real, and informal evaluations of the games suggest that they are fun.
As described by the authors in the conclusion, this paper provides just a starting point. There are various limitations to the proposed techniques and the study; for example, the audible tones detracts from the game play experience and that more formal evaluation of the playability of such games needs to be conducted. It is the prospect that this paper will inspire much follow-on research and development of commercial games that makes this paper particularly exciting.
We would like to thank Prof. Lam for the encouraging review comments. We believe that the concept of Mobile Motion Games (MMG) has a big potential to enrich the existing landscape of mobile games and to attract significant interest from mobile users. It represents a new type of game, which shifts away the players’ focus from the small phone screen, and instead lets the player directly engage in the physical interaction with other players. In this sense, the specific SwordFight game we describe and evaluate in our paper is just one prototypical MMG game, and we hope that other MMG games will be designed and developed in the future.
Technically, our work comprises solutions to enabling continuous, fast and accurate distance ranging between two mobile phones. The key contributions are using a combination of autocorrelation and cross-correlation algorithms for peak-detection, a pipelined processing model, and a technique to counter the Doppler effect. However, it is clear that our solutions represent only a first step, and they are still be far from optimal. The signal-processing part, in particular, still offer ample room for improvements. In order to gain a better understanding of users’ opinion on MMG games, we are actively developing a more mature version of the games proposed in the paper, and our goal is to release these games in the mobile application market in the future. We also plan to conduct experiments to understand the impact of certain issues like the occasional blockage of human hands, or the heterogeneity of mobile phone hardwares and operating systems.