Open Topics

Vol. 69, n° 5-6, May-June 2014
Content available on Springerlink

Improved method for searching interleavers from a certain set using Garello’s method with applications for the LTE standard

Lucian Trifina, Daniela Tarniceriu
Technical Iniversity Gh. Asachi, Iasi, Romania

Abstract In this paper, we propose a method for searching interleavers within a certain class, with the aim of designing turbo codes with good distance spectrum. The method is based on a modified version of Garello’s algorithm and consists in the calculation of frame error rate truncated upper bound. Here, it is applied to quadratic permutation polynomial (QPP) interleavers able to outperform those chosen for the long-term evolution (LTE) standard, for lengths up to 1,504 bits. Three classes of interleavers have been analyzed: (1) the set of QPP interleavers with the largest spread, (2) the set of QPP interleavers with a spread parameter equal to that of LTE interleaver and the highest refined nonlinearity degree, and (3) the complete set of all QPP interleavers for lengths up to 1,008. The distance spectrum optimization is made for all classes. Compared to previous methods for finding QPP-based interleavers, the search complexity is reduced, with improved performances in terms of search time, allowing interleavers of higher length. For lengths up to approximately 450, the best interleavers were found in the first class. For longer lengths, the second class contained the best ones.

Keywords Turbo codes – Distance spectrum – Garello’s method – QPP interleavers – LTE standard

Security analysis of two lightweight RFID authentication protocols

Wang Shao-hui1, 2, 3, Han Zhijie1, 2, Liu Sujuan1, 2 and Chen Dan-wei1, 2
Nanjing University of Posts and Telecommunications, China
2 Jiangsu High Technology Research Key Laboratory for Wireless Sensor Networks, Nanjing, China
3 Network and Data Security Key Laboratory of Sichuan Province, Nanjing, China

Abstract One of the key problems in radio frequency identification (RFID) is security and privacy. Many RFID authentication protocols have been proposed to preserve security and privacy of the system. Nevertheless, most of these protocols are analyzed and it is shown that they cannot provide security against some RFID attacks. Strong authentication and strong integrity (SASI) is the first ultra-lightweight authentication protocol introduced rotation shift operation and RFID authentication protocol with permutation (RAPP) is a new ultra-lightweight authentication protocol with permutation. In this paper, we give the security analysis on these two protocols. An active attack is presented on RAPP, and using the property of the left rotation and permutation operations, we can deduce the relationship of bits of random number or secret keys at different positions, thus obtain all the secrets shared by the reader and the tag. A passive full-disclosure attack is proposed on SASI. Using SASI’s construction weakness, our attack can reveal all the secrets shared by the reader and tag by eavesdropping about 48 rounds of the authentication messages.

Keywords RFID – Lightweight authentication – Permutation – Privacy – Active attack

Jitter analysis of an IPP tagged traffic stream in an {IPP,M}/M/1 queue

Geza Geleji and Harry Perros
North Carolina State University, Raleigh, USA

Abstract We study a single server queue with two different arriving streams, a tagged arrival process and a background arrival process. The tagged traffic is assumed to be an interrupted Poisson process (IPP) and the background traffic is Poisson. The service time is exponentially distributed, and customers are served in a FIFO manner. We obtain numerically the probability density function of the inter-departure time of the IPP tagged arrival process, from which we calculate its jitter, defined as a percentile of the inter-departure time. Numerical results of the 95th percentile and the squared coefficient of variation of the tagged inter-departure time are given as a function of the arrival rate of the background traffic.

Keywords Queueing – Multi-class – Jitter – Percentile

Electrical stochastic modeling of cell for bio-electromagnetic compatibility applications

Sébastien Lalléchère1, 2, Pierre Bonnet1, 2, and Françoise Paladian1, 2
1 Clermont University-University Blaise Pascal, France
2 CNRS, UMR 6602, Aubière, France

Abstract These works were dedicated to the electrical modeling of biological cell subjected to pulsed electromagnetic fields. From the variability of living parameters encountered, an accurate modeling of the electrical and stochastic parameters is necessary. In this paper, we propose simple stochastic approaches based upon a Monte Carlo-like “philosophy” to integrate uncertainties. The use of robust stochastic methods in the field of bio-electromagnetic compatibility allows an improvement of both the efficiency and precision of the technique. The potential aimed applications relying in the study on the sensitivity of biological and electrical parameters in the start of the electroporation phenomenon. We will present the electrical model and the theoretical foundations of these techniques—they will be illustrated on numerical examples.
Keywords Bio-electromagnetic compatibilityElectrical cellUncertaintiesStochastic computational electromagnetics

Hardware realization of the robust time–frequency distributions

Nikola Žarić, Srdjan Stanković and Zdravko Uskoković
University of Montenegro, Faculty of Electrical Engineering, 20000 Podgorica, Montenegro

Abstract A hardware realization of the L-estimate forms of robust time–frequency distributions is proposed. This hardware realization can be used for instantaneous frequency estimation for signals corrupted by a mixture of impulse and Gaussian noise. The most complex part in the hardware implementation is the block that performs sorting operation. In addition to the continuous realization, a recursive realization of the Bitonic sort network is proposed as well. The recursive approach also provides a fast sorting operation with a significantly reduced number of components. In order to verify the results, the FPGA implementations of the proposed systems were designed.

Keywords Robust time–frequency distributions – Bitonic sort network – FPGA implementation

Performance evaluation of an efficient reduced-complexity time synchronization approach for OFDM systems

Leïla Nasraoui, Leïla Najjar Atallah and Mohamed Siala
Higher School of Communications (SUP’COM), Ariana, Tunisia

Abstract This paper presents a performance analysis of a recently proposed preamble-based reduced-complexity (RC) two-stage synchronization technique. The preamble, composed of two identical subsequences, is first used to determine an uncertainty interval based on Cox and Schmidl algorithm. Then, a differential correlation-based metric is carried using a new sequence obtained by element wise multiplication of the preamble subsequence and a shifted version of it. This second step is performed to fine tune the coarse time estimate, by carrying the differential correlation-based metric over the uncertainty interval of limited width around the coarse estimate, thus leading to low computational load. In this paper, we first discuss some complexity issues of the RC approach compared to previously proposed algorithms. Then, we study the effect of the training sequence class and length choices on the synchronization performance in the case of multipath channels. The impact of the uncertainty interval width on the trade-off between performance and complexity is also studied. The two-stage approach was found to provide almost equal performance to those obtained by the most efficient differential correlation-based benchmarks. However, it has a very reduced computational load, equivalent to that of sliding correlation-based approaches.

Keywords OFDM – Synchronization – Preamble – m-Sequences – Gold sequences – Kasami sequences – Sliding correlation – Differential correlation

Adaptive surface extraction from anisotropic volumetric data: contouring on generalized octrees

Ricardo Uribe Lobello, Florence Denis and Florent Dupont
University of Lyon, France

Abstract In this article, we present an algorithm to extract adaptive surfaces from anisotropic volumetric data. For example, this kind of data can be obtained from a set of segmented images from the sampling of an implicit function, or it can be built by using depth images produced by time-of-flight cameras. However, for many applications as geometry modeling, rendering, or finite elements, it is better to use an explicit surface representation. This surface must fit to the geometrical and topological features of the object in order to obtain a good approximation and to avoid topological artifacts. Our algorithm is able to extract adaptive surfaces that accurately approximate the geometry of the original object while minimizing aliasing effects. In addition, our solution is suitable to handle the anisotropy of volumetric representations. In comparison with relevant methods in the state of the art, ours offers a good compromise between mesh quality and precision in the geometrical approximation.

Keywords Surface extraction – Multi-resolution models – Volumetric representation – Image processing