This paper addresses the problem of source-rate control in video streaming over wireless networks. The wireless channel resources are assumed to be shared among a variable number of stations using a contention-based access mechanism. In this context, the resulting throughput available for the video server has been proved to be bursty, which is a feature that makes the high-quality video streaming quite difficult. To face the channel burstiness, we propose a solution that focuses on the fluidity of the video playback by controlling the occupancy of the playback buffer so as not to exceed a desired rate of buffer starvation occurrences. While this constraint has been guaranteed, the encoder maximizes the source bit rate. Rate control is performed adaptively on the basis of a per-interval approach, which has the advantage to reduce the fluctuations in the source bit rate, ensuring smooth variations in video quality and avoiding the "saw" effect that is typically observed in frame-based rate control. Because of its low computational complexity, the proposed scheme is attractive for real-time operation. Simulations are carried out to assess the performance of the proposed scheme.
Power Management mechanisms are widely adopted in Wireless LANs to achieve appreciable power saving. In DCF iBSS networks, all stations in doze mode with pending frames are awaken by the AP at the beginning of next beacon interval. Such stations then switch to the active mode for the reception of the frames. In this work, we propose a different power management technique based on giving the AP the power of deciding which stations with pending frames to wake up. Indeed, there are several circumstances with high channel traffic in which it is better to defer the transmission so as to reduce the expected energy consumption. The AP decision is taken in view of the energy consumption due to collisions and transmissions together with the introduced latency. Through simulations, we show the performance of the proposed method, which may lead to an overall energy saving of about 40% respect to the standard Power Management.
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