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In this paper, we present an optimized topology maintenance framework used in AVStreamer P2P media streaming system. To help new incoming clients get an initial view of the whole network, a new weak hierarchy model is designed to share burdens among different servers. Based on this new model, several key techniques are adopted: node evaluation criteria which can help optimize the node-list cache, receiver-driven gossip which is used to update node-list cache from others more effectively, random walk algorithm which can make the network more random, and status polling which is used to ensure the aliveness of each node cached. Experimental results show that the proposed techniques are effective. [ABSTRACT FROM AUTHOR]

A joint source-channel coding (JSCC) scheme based on adaptive wavelet pretreatment for robust progressive image transmission over wireless fading channels using MIMO-OFDM was proposed. We pointed out that he peak signal to noise ratio (PSNR) of the reconstructed image degrades a little while the complexity decreases sharply when adding pretreatment block before DWT. On the other hand, OFDM can get good performance in the frequency selective fading channel. So in this paper, a JSCC scheme based on adaptive wavelet pretreatment for image transmission over MIMO-OFDM system was analyzed. What‘s more, the wavelet pretreatment block is loaded adaptively according to the channel condition. Simulation shows that: after adding the pretreatment block before DWT and post-treatment to the reconstructed image in good channel condition, the complexity of the SPIHT and the channel coder decreases sharply due to the compression ratio, but the PSNR of the receivedimage loses only a little; when the channel condition is getting worse ,the pretreatment block is deleted accordingly. [ABSTRACT FROM AUTHOR]