Efficient and multi-level privacy-preserving communication protocol for VANET

In this paper, we introduce an efficient and multi-level conditional privacy preservation authentication protocol in vehicular ad hoc networks (VANETs) based on ring signature. The proposed protocol has three appealing characteristics: First, it offers conditional privacy preservation authentication: while every receiver can verify that a message issuer is an authorized participant in the system only a trusted authority can reveal the true identity of a message sender. Second, it is equipped with multi-level countermeasure: each vehicle can select the degree of privacy according to its own requirements. Third, it is efficient: our system outperforms previous proposals in message authentication and verification, cost-effective identity tracking in case of a dispute, and low storage requirements. We demonstrate the merits gained by the proposed protocol through extensive analysis.     

Image bilevel thresholding based on multiscale gradient multiplication

This paper introduces a novel global thresholding approach that exploits the multiscale gradient information. The multiscale gradient information, that is, the product of gradient magnitude (PGM), is obtained by multiplying the responses of the first derivative of Gaussian (FDoG) filter at three adjacent space scales. The output threshold is selected as the one that maximizes a new objective function of the gray level variable t. The objective function is defined as the ratio of the mean PGM values of the boundary and non-boundary regions in the binary image obtained by thresholding with variable t. Through analysis of 35 real images from different application areas, our results show that the proposed method can perform bilevel thresholding on the images with different histogram patterns, such as unimodal, bimodal, multimodal, or comb-like shape. Its segmentation quality is superior to five popular thresholding algorithms.     

Joint scheduling and routing algorithm with load balancing in wireless mesh network

Wireless mesh network (WMN) is a promising solution for last mile broadband internet access. Mesh nodes or mesh routers are connected via wireless links to form a multi-hop backbone infrastructure and improving throughput is the primary goal. While previous works mainly focused on either link level protocol design or complex mathematical model, in this paper, we investigate the performance gains from jointly optimizing scheduling and routing in a multi-radio, multi-channel and multi-hop wireless mesh network. Then, two optimization objectives are addressed by considering wireless media contention and spatial multiplexing. The first objective is to maximize throughput by exploiting spatial reuse while the second one is to ensure fairness among different links. We design a cross-layer algorithm by considering both MAC layer and network layer. Simulation results show that our joint optimization algorithm can significantly increase throughput as well as fairness.     

An efficient stabilized fast Newton adaptive filtering algorithm for stereophonic acoustic echo cancellation SAEC

This paper addresses the field of stereophonic acoustic echo cancellation (SAEC) by adaptive filtering algorithms. Recently, we have proposed a new version of the fast Newton transversal FNTF algorithm for SAEC applications. In this paper, we propose an efficient modification of this algorithm for the same applications. This new algorithm uses a new proposed and simplified numerical stabilization technique and takes into account the cross-correlation between the inputs of the channels. The basic idea is to introduce a small nonlinearity into each channel that has the effect of reducing the inter-channel coherence while not being noticeable for speech due to self masking. The complexity of the proposed algorithm does not alter the complexity of the original version and is kept less than half the complexity of the fastest two-channel FTF filter version. Simulation results and comparisons with the extended two-channel normalized least mean square NLMS and FTF algorithms are presented.     

Hybrid method for designing digital Butterworth filters

A procedure for designing digital Butterworth filters is proposed. The procedure determines the denominator and the numerator of the filter transfer function based on the positions of the poles in the s-plane and zeros in the z-plane, respectively, and calculates the gain factor using a maximum point normalization method. In contrast to some conventional algorithms, the presented procedure is much simpler by directly obtaining the filter with 3-dB frequencies. This makes the presented algorithm a useful tool for determining the boundaries in electronic or communication systems’ frequency responses. Moreover, the proposed algorithm is compatible with high-order transformations which are the limitations of general pole-zero placement techniques. The proposed method is illustrated by the examples of designing the low-pass, high-pass, band-pass, and band-stop filter.     

On the effect of Multiple Access Interference in a Space Time Spreading Time Hopping PPM UWB system

This study investigates the effect of multiple sources using STS across a Time-Hopping-PPM Modulation that is over an UWB Saleh-Valenzuela channel with each source using two transmit antennas. We model and analyze this system, showing that the presence of such MAI results in a significant degradation in BER performance. Simulation results show that for strong signal strength of interfering MAI signals degradation in BER performance is observed for the cases where we have five and 10 distinct MAI sources present when using Walsh-Hadamard thirty two chip spreading sequences. Using simulation, we investigate the use of other sets of orthogonal spreading sequences with improved cross correlation properties and find that for some sequences a significant improvement is seen compared to Walsh-Hadamard sequences when they are similarly misaligned. We show that MAI degrades the BER performance of such systems and that selection of improved cross correlation spreading code sequence sets improves BER.     

Local Upsampling Fourier Transform for accurate 2D/3D image registration

An accurate image registration method based on Local Upsampling Fourier Transform (LUFT) is developed in this paper. It uses a hierarchical strategy to estimate more accurate image pair’s registration parameters, which consists of a coarse estimation and a robust and efficient refinement stage as well. The initial parameter is estimated through a conventional Phase Only Correlation (POC) method in the coarse stage, and then it is refined by the Local Upsampling Fourier Transform in frequency domain to achieve higher accuracy. Furthermore, as will be shown in many experiments, the LUFT can achieve more accurate translation and rotation estimation, and it is efficient, robust to noise, and it can be applied to accurate 2D and 3D image rotation and translation estimation.     

A framework for establishing trust in the Cloud

Cloud infrastructure is expected to be able to support Internet scale critical applications (e.g. hospital systems and smart grid systems). Critical infrastructure services and organizations alike will not outsource their critical applications to a public Cloud without strong assurances that their requirements will be enforced. Central to this concern is that the user should be provided with evidence of the trustworthiness of the elements of the Cloud without getting involved into infrastructure details. In addition, users should be able to control their outsourced data at public Clouds. Establishing Cloud’s trust model is important but the Cloud’s infrastructure complexity and dynamism makes it difficult to address. This paper focuses on an important angle in this direction. We start by identifying the related challenges for establishing trust in the Cloud, and then propose a foundation framework which can help in addressing the identified challenges. Our focus is on IaaS Cloud type and on organizations as Cloud users.     

A hybrid channel assignment strategy to QoS support of video-streaming over multi-channel ad hoc networks

Currently multi-channel multi-interface ad hoc networks (multi-channel ad hoc networks) have received amount of interest, especially under the context of real-time traffics, such as video applications. Channel assignment is one of the key challenges in multi-channel ad hoc networks. In this paper, based on a representative hybrid channel assignment strategy named as HMCP, a statistic link load based hybrid channel assignment strategy, SLL-HCA, is presented to obtain a better channel assignment metric than that in HMCP. SLL-HCA is based on the HMCP protocol and adopts the statistic link load metric to ensure load balancing in a two-hop neighborhood, and to prevent both the hidden node problem and the exposed node problem. In addition, an enhanced strategy, VE-SLL-HCA, by setting harsher channel assignment conditions and reserving lower interference of routing path for video-streaming traffic than other non-video traffic, is proposed to improve the QoS support of video-streaming over multi-channel ad hoc networks. Simulation results show that SLL-HCA achieves better throughput performance than HMCP in the presence of background traffic including CBR traffic or VBR traffic; and, the PSNR QoS metric for video-streaming is enhanced when using VE-SLL-HCA compared with SLL-HCA and HMCP, which confirms the validity of the proposed strategy for video-streaming traffics. Moreover, the simulation results also indicate that non-video traffic unlikely suffers an unacceptable performance in terms of throughput.