Mobile Ad hoc Networks (MANETs) are temporary formed, infrastructure-less networks. The performance metrics deteriorate due to the unstable channel conditions, network connectivity, mobility and resource limitations. To improve different performance metrics, various cross-layering approaches are utilized where different OSI layer information are exchanged. AODV is a popular distance vector proactive routing algorithm. In our research we investigate a modified version of AODV routing protocol, based on route discovery by utilizing Physical Layer information instead of the minimum hop count approach of the default distance vector algorithm. The research also elaborates how the proposed model uses the received SNR to find its route. The paper also proposes future research direction for utilizing Polar Coding for fading channel. The results of the simulations show improvement on the existing default AODV performance metrics like MANET traffic throughput, application specific response time, data dropped, delay etc.
Distributed video coding is an emerging area of research for digital video driven partly by the widespread use of video acquisition devices by the consumers. In this paper, we present a distributed video coding scheme based on zero motion identification at the decoder and constrained rate adaptive low density parity check (LDPC) codes. Zero-motion-block identification mechanism is introduced at the decoder, which takes the characters of video sequence into account. The constrained error control decoder can use the bits in the zero motion blocks as a constraint to achieve a better decoding performance and further improve the overall video compression efficiency. It is only at the decoder side that the proposed scheme exploits temporal and spatial redundancy without introducing any additional processing at the encoder side, which keeps the complexity of the encoding as low as possible with certain compression efficiency. As a powerful alternative to Turbo codes, LDPC codes have been applied to our scheme. Since video data are highly non-ergodic, we use rate-adaptive LDPC codes to fit this variation of the achievable compression rate in our scheme. But one most basic difference between LDPC codes in our scheme and conventional channel coding is that in our scheme, we can make sure some bits are known. Those bits can work as constraints to the decoder and improve the decoding performance. We propose a constrained LDPC decoder not only to improve the decoder efficiency but also to speed the convergence of the iterative decoding. Simulation demonstrates that the scheme has significant improvement in the performances. In addition, the proposed constrained LDPC decoder may benefit other application.
To improve the accuracy and reliability of modulation recognition at low signal to noise ratio (SNR) and few knowledge of signal parameter, the novel method based on the cyclic spectral feature and support vector machine(SVM) is presented. In the process of novel algorithms, the cyclic spectral analysis is used to realize the feature extract of the modulated signals, and the Eigenface method is used to reduce the amount of spectral coherence feature. Then, a new scheme of classification based on support vector machine is presented to classify the modulation signal. The experiment shows that the modulation classification accuracy of presented method is significantly improved at low SNR environment.
Distributed video coding (DVC) is a new video coding paradigm that shifts the complexity from the encoder side to the decoder side. One particular case of DVC, the Wyner-Ziv coding scheme, encodes each video frame separately and decodes the video sequence jointly with side information. This paper presents a new Wyner-Ziv video coding scheme based on hierarchical block matching algorithm (HBMA). In this proposed scheme, the side information is greatly refined to assist the reconstruction of the Wyner-Ziv frames. The bidirectional motion estimation and the forward motion estimation are associated to generate the interpolated frame from temporally adjacent key frames to attain the high fidelity side information. During the bidirectional motion estimation, the size of the block and the search area vary at different levels of hierarchy. In additional, the motion vectors are inherited from big blocks to small blocks by choosing the smallest mean-of-the-absolute-difference value among neighboring blocks. Preliminary experiment results show that the proposed scheme can achieve better rate-distortion performance by 0.5-1 dB compared to the existing Wyner-Ziv video coding with the slightly increased decoding complexity.
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