Adaptive frame length algorithm for inter-satellite links

In view of the low ranging efficiency of the conventional fixed frame-length algorithm in the inter-satellite link,an adaptive frame-length algorithm is proposed. The frame length is adjusted adaptively according to the results of ranging and velocity measuring to improve ranging efficiency. Buffers which enable the frame length to be selected discretely and adaptively are introduced to avoid frequent hopping of the frame-length.Frame length marker is created to automatically identify the frame-length for frame synchronization procedures in receivers. The feasibility and the validity of the proposed algorithm to improve the efficiency of ranging are verified through both theoretic analysis and simulation,and the efficiency improves up to 88% when there are five buffers. This improvement can be further enhanced by increasing the number of buffers. Proper allocation of inter-satellite buffers is required to make a balance between the ranging efficiency and the system complexity.

Error Resilient Video Communication Based on Picture Level Adaptive Frame / Field Coding

Packet loss protection method based on picture level adaptive frame /field coding (PAFF)was presented. Firstly,the end-to-end rate-distortion analysis for PAFF on the current frame was performed. Secondly,in order to evaluate the severity of error propagation in the following frames,the error propagation intensity and human visual quality sensitivity of different areas were taken into consideration. It was followed by the quantification of relative importance. Finally,the proper coding mode was chosen utilizing an unequal comparison procedure. The simulation results show that the proposed method can improve peak signal-to-noise ratio (PSNR) up to 0. 9 dB and 1. 6 dB comparing with the field only and the dispersed flexible macro-block ordering (FMO)only methods respectively.

Adaptive TDMA slot assignment protocol for vehicular ad-hoc networks

This paper proposes a novel adaptive time division vehicular ad-hoc networks. ATSA divides different sets multiple access （TDMA） slot assignment protocol （ATSA） for of time slots according to vehicles moving in opposite directions. When a node accesses the networks, it choices a frame length and competes a slot based on its direction and location to communication with the other nodes. Based on the binary tree algorithm, the frame length is dynamically doubled or shortened, and the ratio of two slot sets is adjusted to decrease the probability of transmission collisions. The theoretical analysis proves ATSA protocol can reduce the time delay at least 20% than the media access control protocol for vehicular ad-hoc networks （VeMAC） and 30% than the ad-hoc. The simulation experiment shows that ATSA has a good scalability and the collisions would be reduced about 50% than VeMAC, channel utilization is significantly improved than several existing protocols.

A Novel MBAFF Scheme of AVS

Adaptive frame/field coding techniques have been adopted in many international video standards for interlaced sequence coding. When the frame/field adaptation is applied on the picture level, the coding efficiency is improved greatly, compared with the pure frame coding or the pure field coding. The picture-level adaptive frame/field coding （PAFF） selects frame coding or field coding once for one picture. If this frame/field adaptation is extended to Macro Block （MB） level, the coding efficiency will be further increased. In this paper, a novel MB-level adaptive frame/field （MBAFF） coding scheme is proposed. In the proposed MBAFF scheme, the top field of the current picture is used as a reference. The experiments are implemented on the platforms of Audio Video coding Standard （AVS） base profile and H.264/AVC, respectively. On the AVS platform, 0.35dB gain can be achieved averagely, compared with AVS1.0 anchor. On the H.264/AVC platform, 0.16dB gain can be achieved averagely, compared with MBAFF scheme of H.264/AVC. Additionally, an extensive subjective quality enhancement can be achieved by the proposed scheme.