Study Of The Key Technologis For Guaranteeing The QoS Of The Real-time Video Communications On NGN

Recently, the Next Generation Network(NGN) has developed at very fast speed. NGN is essentially an IP based network that enables any category of customers to receive wide range of internet services which is springing up, such as VOD, IPTV, and so on. Multimedia services requires core network to provide end-to-end quality-of-service (QoS) guarantees and enough bandwidth.The issue of guranteeing the QoS of Real-time video communications on NGN is researched in this thesis. The central contents are as follows:Based on the estimation model of video subjective quality, a bandwidth allocation strategy for video communications on next generation network was presented. Aiming at the variable network status, two algorithms of the bandwidth allocation are involved, one of which is used to guarantee the QoS of the different priority terminals, and the other of which is used to maximize the total video quality of all the terminals. When the network status has changed worse, experimental results show that the Peak Signal-to-Noise Ratio (PSNR) of recovery video quality can be increased by more than 14dB using the proposed method. In addition, when the network status has degraded too much to meet the video bit rate requirement of all the active terminals, the proposed bandwidth allocation algorithm can also guarantee the total video quality of all the terminals as maximal as possible.According to the network abstraction layer unit (NALU) of H.264 and the characteristic of real-time video communication, a novel format of real-time transport protocol (RTP) payload, which provides the protection to the data of the terminals, was presented. Using forward erasure correction and data interleaving, this method could provide the unequal protection mechanism to the H.264 video stream. The more important the H.264 video stream, the stronger protection it could provide. Simulation results show that the quality of the reconstructed video can be greatly increased with similar bit rates by using the presented method.When the terminals ask for the video communications based on media gateway (MG)/media gateway controller (MGC) on NGN, the strategy, which is used by the MGC to allocate the initial value of the bandwidth, was presented. When the network bandwidth has decreased or been allocated irrationally and this leads to the bad video quality of the terminals between the MG of the sender and the MG of the receiver, MGC should use the bandwidth allocation strategy for the terminals based on the request of the terminals. At last, an extension packet of H.248 protocol was presented, the packet can be used by MGC to inform MG about using FEC to protect the data of the terminals. Simulation results show that the methords can guarantee the QoS of video communications and make use of the bandwidth resource effectively.