tailieunhanh - Resource Management in Satellite Networks part 29

Resource Management in Satellite Networks part 29. This book provides significant knowledge on innovative radio resource management schemes for satellite communication systems that exploit lower layer adaptivity and the knowledge of layer 3 IP QoS support and transport layer behavior. The book integrates competencies considering all the parts of system design: propagation aspects, radio resource management, access protocols, network protocols, transport layer protocols, and more, to cover both broadband and mobile satellite systems | 266 Ulla Birnbacher Wei Koong Chai implementation the encoder works at the transport layer by fetching k information packets from the video stream and then transmitting k l UDP packets k of information l of redundancy towards the receiving host. The encoder adds a preamble of 4 bytes for the sequence number which is then cancelled by the decoder. The decoder fetches k of the k l packets per block and recovers the information provided that no more than l packets are lost in a single block of packets. The receiver then feeds the MPEG-4 decoder with the received stream. Different MPEG-4 movies have been broadcast towards the terrestrial WLAN through the satellite channel by using a standard video decoder and home-made FZC encoding decoding software. The authors in 31 used this software to work between the application layer and the UDP transport layer however this software can also be used between layer 2 and 3. The performance evaluation has been based both on subjective perception of QoS and on objective parameters of QoS. The used subjective assessment has been the perceptual quality called the Mean Opinion Score MOS which requires several observers and many tests in order to provide a reasonable statistical spread of results 1 . The reference measure used for an objective video quality assessment has been the Peak Signal to Noise Ratio PSNR calculated on the difference signal between the original error-free sequence and the received decoded sequence. Other general ob jective parameters of QoS such as packet delivery delay and packet loss have been considered in 31 . In what follows the numerical results are presented. Packet Loss - The experiment in un-coded mode no FZC shows that packet loss can be reduced from 13 to about 6 by changing the transmission rate from 11 to Mbit s see Table . In this case the channel occupancy increases by 56 . Interestingly we can note that with FZC and 200 100 coding ratio the packet loss is almost zero. Coding ratio Packet .