Video Streaming over Wireless Networks

The next generation wireless systems should support multimedia streaming applications. Multimedia streams are usually modelled by variable-bit-rate (VBR) traffics. Video streams are generated by applying an encoder --- such as an MPEG-4 encoder --- to digitized video traces. The result is a periodic sequence of packets with nonconstant length. The size of each packet is related to the information content of the frame and its location inside the group of frames.

To support video applications, the network should provide appropriate resources --- in terms of guaranteed bandwidth and buffer size --- for the
encoded trace.  In this research, we devise a technique for non-conservative resource allocation. Nevertheless, we would like to avoid the necessity of selecting a probability model for input traffic. We measure the network performance in terms of percentile of the queue size. The proposed approach is stochastic; nonetheless, no explicit  model for input traffic is imposed.

An acceptable level of quality-of-service (QoS) for the transmitted stream will be provided if the wireless network can guarantee a minimum bandwidth for encoded video stream. For a real-time application, an acceptable bandwidth would be the peak rate. If a bandwidth equal to the peak rate is allocated to the video stream, each packet will arrive at the receiver early enough so that it can be played back in its proper time instant. Although using the peak rate will guarantee a real-time playback of the video stream, it will require a large allocated bandwidth and will lead to a conservative network design. On the other hand, if the allocated bandwidth is smaller than the peak rate, some packets will not arrive in time for playback. In such cases, a buffer will be used to store the packets. The packets will be played back after an appropriate amount of traffic is accumulated in the buffer. The packets will be collected in the playback buffer and will be read into the decoder in a constant rate. In practice, there exists a relationship between the size of the playback buffer, the induced delay, the speed of transmission, and the percentage of data that will be buffered. In this research, we formulate this relationship and use it to estimate the performance of video streaming applications in a wireless environment.