Concerning the fact that the existing rate adaptation algorithms based on Dynamic Adaptive Streaming over HTTP (DASH) have frequent bitrate switching and low average bitrate in wireless network, a Rate Smooth Switching (RSS) algorithm based on DASH standard was proposed. Firstly, a sliding window was used by the bandwidth detection mechanism of the algorithm to sample the download speed of historical segments to calculate the bandwidth offset coefficient, the fluctuation of the bandwidth was initially determined according to the value of offset coefficient, and the situation of the fluctuation was further determined whether there was a consistent variation trend, thereby distinguishing continuous variation and short-term jitter of the bandwidth, and the bandwidth prediction value corresponding to each circumstance was calculated. Secondly, with bandwidth fluctuation, buffer occupancy and variation, bandwidth prediction value considered, the rate decision model of the algorithm adopted Fast Buffering (FB), Slow Switching (SS), Fast Rising (FR), Limited Declining (LD), Stable Holding (SH) strategies and sleeping mechanism to dynamically control the video bitrate selection process. The experimental results show that compared with fuzzy-based DASH rate adaptation algorithm and modulated throughput driven rate adaptation algorithm, the proposed algorithm can not only increase the bitrate to optimum level in the shortest time at the beginning of video playback to improve the average bitrate, but also minimize the number of bitrates' switching in the case of sudden change and frequent fluctuation of bandwidth, thus obtaining a good quality of experience for wireless video users.

Due to the inherent randomness of bandwidth, the existing rate adaptation algorithms based on Dynamic Adaptive Streaming over Hyper Text Transfer Protocol (DASH) fail to make a balance between playback fluency and video quality. Concerning the above problem, a State machine-based DASH (SDASH) algorithm was proposed to analyze and control the rate switching process. Firstly, the influence factors of client's Quality of Experience (QoE) were fully considered and numerically analyzed. Secondly, six bitrate states were proposed according to the influence factors, and the relations between the video bitrate and the changes in influence factors' values were used as the state transition conditions. Finally, while the playback buffer and the bitrate deviation ratio satisfying the threshold condition, the video bitrate was switched to a rate level which has the relatively optimum overall performance of playback fluency and video quality. The experimental results demonstrate that the proposed algorithm can not only improve the video bitrate compared with the fuzzy-based DASH adaptation algorithm but also avoid bitrate plunging, thus reaching a balance between playback fluency and video quality, and leading to an improvement of QoE.

In order to solve the problem of updating distance information frequently in the traditional method of setting uplink synchronization based on ranging information, a uplink clock synchronization method based on location information was proposed. Firstly, by measuring the pseudoranges to form a nonlinear system of equations, the location information of the terrestrial unit was located by using the solution method based on the principle of least squares. Then, due to the known location information of satellite movement, the change relationship of the distance between the satellite and the ground with time could be further obtained. The distance was converted into time delay to obtain the time advance of the uplink signal transmission of the terrestrial unit. Finally, the transmitter of the terrestrial unit was adjusted to make that the uplink signal could just arrive at the satellite in the assigned time slot with high accuracy, and the purpose of uplink clock synchronization was achieved. The simulation results show that, the proposed method can realize the synchronization of uplink clock in the satellite constellation communication system with high accuracy for the static units in the earth surface all over the world, and avoid the frequent ranging updates with high accuracy.

BWDSP100 is a 32-bit static scalar Digital Signal Processor (DSP) with Very Long Instruction Word (VLIW) and Single Instruction Multiple Data (SIMD) features, which is designed for high-performance computing. Its Instruction Level Parallelism (ILP) is acquired though clustering and special SIMD instructions. However, the existing compiler framework can not provide support for these SIMD instructions. Since BWDSP100 has much SIMD vectorization resources and there are very high requirements in radar digital signal processing for the program performance, an SIMD optimization which surpported the selection of single or double word mode was put forward based on the traditional Open64 compiler according to the characteristics of BWDSP100 structure, and it can significantly improve the performance of some compute-intensive programs which are widely used in DSP field. The experimental results show that this algorithm can achieve speedup of 5.66 on average compared with before optimization.

To comprehensively consider the factors influencing the moving objects in uncertain environment, a k-anonymity privacy-preserving method for the trajectory recorded by automatic identification system was presented. Firstly, an uncertain spatial index model was established which was stored in grid quadtree. Then the continuous k-Nearest Neighbor ( KNN) query method was used to find the trajectory which had the similar area to the current trajectory, and the trajectory was added to the anonymous candidate set. By considering the network scale influence on the effectiveness of the anonymous information and the probability of attacker's attack on trajectory, the optimal exploit chain of trajectory was generated by using the heuristic algorithm to strengthen the trajectory privacy-preserving. Finally, the experimental results show that, compared with the traditional method, the proposed method can decrease the information loss by 20% to 50%,while the information distortion can maintain below 50% with the enlarge of query range and the cost loss is cut down by 10% to 30%.The proposed method can effectively prevent malicious attackers from the information access of trajectory,and can be applied for the official boat to law enforcement at sea.

Concerning the problem that deadzone quantization in image compression cannot protect the edges of images effectively, a novel quantization algorithm called Lowpass subband Maxima Mapping Quantization (LMMQ) was proposed. In all kinds of subbands after wavelet transform, the importance of the coefficients in lowpass subbands could be decided by the average value of all coefficients in highpass subbands which have a mapping relationship with the coefficients in lowpass subbands. During quantization, the coefficients of highpass subbands were quantized by deadzone quantization in JPEG2000. The quantization step size of coefficients in lowpass subbands could be adaptively refined because of their own importance, so the edges of images could be protected effectively. The proposed algorithm has an advantage of adaptability in the aspect of coefficient selection when the step size is refined, and has higher encoding speed in Tier1 of EBCOT (Embedded Block Coding with Optimized Truncation) than traditional JPEG2000. The experimental results show that the proposed algorithm has an advantage of protecting the edges of images and has 0.2 dB more than traditional deadzone quantization.

Concerning the low efficiency of present methods of IP lookup, a new data lookup algorithm based on Multi-Bit Priority Tries (MBPT) was proposed in this paper. By storing the prefixes with higher priority in dummy nodes of multi-bit tries in proper order and storing the prefixes for being extended in an auxiliary storage structure，this algorithm tried to make the structure find the longest matching prefix in the internal node instead of the leaf node. Meanwhile, the algorithm avoided the reconstruction of router-table when it needed to be updated. The simulation results show that the proposed algorithm can effectively minimize the number of memory accesses for dynamic router-table operations, including lookup, insertion and deletion, which significantly improves the speed of router-table lookup as well as update.

In view of the problem that data for Named Data Networking (NDN) cache is replaced efficiently, a new replacement policy that considered popularity and request cost of data was proposed in this paper. It dynamically allocated proportion of popularity factor and request cost factor according to the interval time between the two requests of the same data. Therefore, nodes would cache data with high popularity and request cost. Users could get data from local node when requesting data next time, so it could reduce the response time of data request and reduce link congestion. The simulation results show that the proposed replacement policy can efficiently improve the in-network hit rate, reduce the delay and distance for users to fetch data.

To find out QoS routing quickly and reliably,an new ant colony system algorithm rooted in Dijkstra strategy was suggested out.The source code flooded searching ants to all its adjoining and QoS-satisfied nodes.Every adjoining node selected out the best-performance one due to an early-setted judgmental function from all the arrived ants,then copied and flooded it again.The ants went on flooding until it got to the aim node at last.After searching all the possible routs between the source node and the aim node,this algorithm must be able to find out the QoS routing fitted for request.As proved in example followed,this algorithm has virtue of briefness,efficiency and strong convergence.