  Mobile cloud gaming enables high-end games on constrained devices by
streaming the game content from powerful servers through mobile networks.
Mobile networks suffer from highly variable bandwidth, latency, and losses that
affect the gaming experience. This paper introduces Nebula, an end-to-end cloud
gaming framework to minimize the impact of network conditions on the user
experience. Nebula relies on an end-to-end distortion model adapting the video
source rate and the amount of frame-level redundancy based on the measured
network conditions. As a result, it minimizes the motion-to-photon (MTP)
latency while protecting the frames from losses. We fully implement Nebula and
evaluate its performance against the state of the art techniques and latest
research in real-time mobile cloud gaming transmission on a physical testbed
over emulated and real wireless networks. Nebula consistently balances MTP
latency (<140 ms) and visual quality (>31 dB) even in highly variable
environments. A user experiment confirms that Nebula maximizes the user
experience with high perceived video quality, playability, and low user load.
