Concerning the problem that the existing bitrate adaptation algorithms based on Dynamic Adaptive Streaming over Hyper Text Transfer Protocol （HTTP） （DASH） have low buffer utilization and low average bitrate， a Bitrate Adaptive Switching based on Buffer Compensation （BASBC） algorithm based on DASH standard was proposed. Firstly， the bandwidth fluctuation was analyzed according to the download speeds of the recent downloaded fragments， and thereby obtaining the estimated bandwidth. Secondly， according to the estimated bandwidth and current bitrate level， bitrate higher/lower switching thresholds were set in the buffer to control bitrate switching to higher level and consum buffer time， or to control bitrate switching down gradually and accumulate buffer time， respectively， so that a consumption-accumulation buffer state loop was formed in video buffer. The average bitrate of video playback of BASBC algorithm is higher than that of Dynamic Adaptive Step-wise Bitrate Switching （DASBS） algorithm for HTTP streaming， thereby effectively improving the bandwidth utilization. Although the average bitrate of the proposed algorithm is slightly lower than that of Rate Smooth Switching （RSS） algorithm based on DASH standard， the smoothness of bitrate switching of the proposed algorithm is better， improving the switching stability. Experimental results show that the proposed algorithm has good performance such as high bandwidth utilization， switching smoothness and switching stability in dynamic network environment， which can effectively improve the Quality of Experience （QoE） of users.

In order to improve the performance of the Simultaneous Wireless Information and Power Transfer (SWIPT) system, a new cache-aided full-duplex relay collaborative system model was constructed, and the free Energy Access Points (EAPs) were considered as the extra energy supplement of relay nodes in the system. For the system throughput optimization problem, a new SWIPT relay selection strategy based on power allocation cooperation was proposed. Firstly, a problem model on the basis of the constraints such as communication service quality and source node transmit power was established. Secondly, the original nonlinear mixed integer programming problem was transformed into a pair of coupling optimization problems through mathematical transformation. Finally, the Karush-Kuhn-Tucker (KKT) condition was used to solve the internal optimization problem with the help of Lagrange function, so that the closed-form solution of the power allocation factor and the relay transmit power was obtained, and the external optimization problem was solved based on this result, so as to select the best relay for the cooperative communication. The simulation experimental results show that, the free EAPs and the configuration of cache for the relay are feasible and effective, and the proposed system is significantly better than the traditional relay cooperative communication systems in terms of throughput gain.

The deficiency of evaluation scheme for the imperceptibility of Natural Language Watermarking (NLW) seriously restricts the development in this field. To resolve this problem, combining the characteristics of natural language and the knowledge of psycholinguistics and considering the difficulty for human to understand natural language, an imperceptibility perceptual model and an automatic evaluation scheme were proposed. The proposed scheme evaluated the imperceptibility from three aspects: syntax error, collocation error and semantic loss. Finally, four different watermarking schemes including the T-Lex watermarking system based on absolute synonym substitution, the relative synonymous substitution watermarking system, the watermarking system based on syntactic tree and the Chinese syntactic watermarking system were used to compare the results of the proposed automatic method and manual method whose confidence coefficient is 90%. The two methods get the same conclusion: the imperceptibility of NLW based on word is better than that of NLW based on sentence, and the automatic evaluation scheme is effective for the imperceptibility of NLW.

The conventional steganalysis techniques does not work in zero-watermarking technology because it does not modify carrier text. However, active attack model on text zero-watermarking has not been well studied. In order to solve this problem, an active attack algorithm for text zero-watermarking was proposed. Making use of synonym substitution technology, sync-attack and birthday-attack were defined. Through combining the two active attack methods, a lexical active attack algorithm on text zero-watermarking was designed and implemented. The experimental result shows the proposed algorithm can effectively destroy zero-watermarking without modifying carrier text massively.