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Abstract-This paper presents a multimedia streaming service in a mobile (3G) environment that, in addition to in-band congestion signals such as packet losses and delay variations, receives congestion cues from a Network Coverage Map Service (NCMS) to make rate-control decisions. The streaming client routinely queries the NCMS to assess the network conditions at future locations along its expected path. The streaming client may ask the streaming server for short-term transmission bursts to increase pre-buffering when it is approaching areas with bad network performance to maintain media quality. If needed, the client may also switch to a different encoding rate (rate-switching) depending on the severity of expected congestion. These notifications are scheduled as late as possible, so that any changes in network conditions and/or changes in user's movements can be taken into account (late scheduling). Using this type of geo-predictive media streaming service we show that the streaming client can provide pause-less playback and better quality of experience to the user.

Abstract-Wireless cellular environments, such as UMTS, are often affected by congestion and errors, which are inherent to wireless transmission channels due to fading, interference, resource scarcity, mobility, etc. For a conversational video application to be successful i.e., to provide good viewing quality to the receiver at all times, the sender must be able to quickly adapt its sending/encoding rate (and other related parameters) to that offered by the link. Moreover, for a rate adaptation scheme to be successful, the receiver must provide timely feedback in order to mitigate further losses due to congestion. In this paper, we investigate different rate adaptation mechanisms and redefine them for 3GPP networks, reusing existing RTCP extensions standardized in the IETF and in 3GPP where possible.

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