Implementation Issues in Turbo Decoding for 3GPP FDD Receiver

In the Frequency Division Duplex (FDD) mode of the Third Generation Partnership Project (3GPP) standard, implementation of the turbo decoder, especially for the mobile equipments, faces design decisions related to computational complexity, power efficiency, and memory requirements. In this paper we compare different approaches of low complexity implementation of the turbo decoder, with emphasis on the issues of signal scaling and quantization, the sliding window operation for memory size reduction and the iteration stopping algorithms. The demodulated signal at the output of the RAKE receiver may have a wide dynamic range and it may require many bits of precision. In order to overcome the numerical precision problem and to prevent Log Likelihood ratio (LLR) metric overflow, a scaling algorithm must be used. Our simulation results indicate that the Average Absolute (AA) algorithm using dynamic scaling outperforms other scaling schemes and it is less sensitive to the channel conditions. One of the major challenges in the implementation of a practical turbo decoder is optimization of memory requirements. In this paper we evaluate the performance of the sliding window algorithm using different main and guard window sizes. We show that the bit and block error rate performance of the sliding window scheme mainly depend on the guard window size rather than the main window size. The simulation results indicate that small guard window sizes can significantly decrease the iteration gain for large frames in fast fading channels. Iteration stopping algorithms reduce the power consumption and the latency of the decoder and help to dedicate more resources to other functions of the receiver. The block error distribution in the fading channels makes it even more essential to use an iteration stopping rule. Our simulations conclude that a rule called the minimum absolute value appears to be a very effective, low complexity and robust algorithm. Mohamadreza Marandian Hagh was born in Tabriz, Iran on January 1974. He received the B.S. and the M.S. degrees in electrical engineering from Tehran University with honors in 1996 and 1999, respectively. He is pursuing the Ph.D. degree in electrical engineering at Northeastern University, Boston. His research interests includes information theory, channel coding and iterative techniques for wireless communication systems. His current research is focused on low complexity designs for iterative receivers using Space-Time coding in time-dispersive channels. He is also interested in Exit-Chart analysis of iterative receivers. From 1996 to 1999, he was with Sana Pro Inc. as a system engineer, developing simulation tools for OFDM, WCDMA, CDMA2000. He is currently with Airvana Inc. in Chelmsford, MA and working on 1xEVDO wireless systems. Masoud Salehi received BS degree (Summa Cum Laude) from Tehran University and MS and Ph.D. degrees from Stanford University all in Electrical Engineering. Before joining Northeastern, he was with the Departments of Electrical and Computer Engineering, Isfahan University of Technology and Tehran University. From February 1988 to May 1989 Dr. Salehi was a visiting professor at the Information Theory Research Group, Department of Electrical Engineering, Eindhoven University of Technology, The Netherlands, where he did research in network information theory and coding for storage media.In 1989 Dr. Salehi joined Department of Electrical and Computer Engineering, Northeastern University. Professor Salehi is a member of the CDSP (Communication and Digital Signal Processing) Center. His main areas of research interest are network information theory, source-channel matching problems in single and multiple user systems, data compression, turbo coding, coding for fading channels, and digital watermarking. Professor Salehi’s research has been supported by research grants from the National Science Foundation (NSF), GTE, NUWC, CenSSIS, and Analog Devices. Professor Salehi has also done consulting to the industry including Teleco Oilfield Services and AT&T. Professor Salehi is currently a member of the Editorial Board of The International Journal of Electronics and Communications.Professor Salehi is the coauthor of the textbooks “Communication Systems Engineering”, Prentice-Hall 1994, 2002, “Contemporary Communication Systems Using MATLAB and Simulink” Thomson 1998, 2000, 2004, and “Fundamentals of Communication Systems”, Prentice-Hall 2005. Abhay Sharma received B.E. (Hons) Electrical and Electronics Engineering degree from Birla Institute of Technology and Science, Pilani, India in 1996 and M.S. Electrical Engineering degree from Ohio State University, Columbus in 2000. From 2000 to 2005 he was working with Analog Devices, RF and Wireless Systems Group, Wilmington, USA, where he was working on design and implementation of algorithms for the emerging cellular communication standards. Currently he is working with Allgo Embedded Systems, Bangalore, India, in the area of wireless networks and systems based on the emerging W-PAN wireless technologies. Zoran Zvonar received the Dipl. Ing. degree in 1986 and the M.S. degree in 1989, both from the Department of Electrical Engineering, University of Belgrade, Yugoslavia, and the Ph.D. degree in Electrical Engineering from the Northeastern University, Boston, in 1993.From 1986 to 1989 he was with the Department of Electrical Engineering, University of Belgrade, Belgrade, Yugoslavia, where he conducted research in the area of telecommunications. 1993 to 1994 he was a Post-Doctoral investigator at the Woods Hole Oceanographic Institution, Woods Hole, MA, anconducted research on multiple-access communications for underwater acoustic networks. Since 1994 he has been with the Analog Devices, Communications Division, Wilmington, USA. He is the Manager of the Systems Engineering Group focusing on the design of algorithms and architectures for wireless communications, with emphasis on integrated solutions and real-time software.He was a Guest Editor of the IEEE Transactions on Vehicular Technology, the International Journal of Wireless Information Networks and the ACM/Baltzer Wireless Networks, Associate Editor of the IEEE Communications Letters and a co-editor of the books GSM: Evolution Towards Third Generation Systems, Kluwer Academic Publishers, 1998, Wireless Multimedia Networks Technologies, Kluwer Academic Publishers, 1999 and Software Radio Technologies: Selected Reading, IEEE Press, 2001. Dr. Zvonar is currently Co-Editor of the Radio Communication Series in the IEEE Communications Magazine.     

The WINLAB Network Centric Cognitive Radio Hardware Platform—WiNC2R

This paper presents the design goals and architecture of WiNC2R—the WINLAB Network Centric Cognitive radio hardware platform. The platform has been designed for flexible processing at both the radio physical layer and MAC/network layers with sustained bit-rates of ~10 Mbps and higher. The hardware prototype supports multi band operation with fast spectrum scanning, the ability to dynamically switch between a number of OFDM and DSSS modems and multiple MAC protocols. The radio modems, MAC, and network-layer protocols are implemented in a flexible manner using general-purpose processing engines and a set of dynamically configurable hardware accelerators. An FPGA based platform implementation currently in progress is described in terms of key hardware components including the software-defined modem, the flexible MAC engine and network-level processor. Preliminary prototyping results are reported, and a roadmap for further evolution of the WiNC2R board is provided.     

A Novel Three-State ARQ Scheme for Variable Error-Tate Channels

This paper presents a new type of automatic-repeat-request (ARQ) scheme, Three-State ARQ (TS-ARQ), for error control in data transmission over a noisy channel. The new scheme is based on the Go-Back-N (GBN) protocol and uses three different methods of GBN protocols: basic GBN, n-copy GBN and continuous-GBN. The new ARQ model is applicable for channels having the variable noise level going from low through medium until very high levels. As it is known, such wireless channels are to be found in terrestrial and space (satellite) communications. This model is to be used for the estimation of the noise state in the channel and one of the methods is used, depending of the noise level. When the noise level is low GBN-ARQ is used, in the case of the medium noise level the n-copy GBN is used, and if the noise level is high continuous-GBN will be applied. This paper presents the method of determining the parameters and transfer moments from one state to another. An original mathematical model is given, together with evaluation results. These results are compared with the known methods and the conclusion that the described method provides some better performances is drowned. The implementation of this new procedure is simple as described in the flow chart given in the paper.     

Detection of Structural Features in Biological Signals

In this article structures in biological signals are treated. The simpler—directly visible in the signals, which still demand serious methods and algorithms in the feature detection, similarity investigation and classification. The major actions in this domain are of geometric, thus simpler sort, though there are still hard problems related to simple situations. The other large class of less simple signals unsuitable for direct geometric or statistic approach, are signals with interesting frequency components and behavior, those suitable for spectroscopic analysis. Semantics of spectroscopy, spectroscopic structures and research demanded operations and transformations on spectra and time spectra are presented. The both classes of structures and related analysis methods and tools share a large common set of algorithms, all of which aiming to the full automatization. Some of the signal features present in the brain signal patterns are demonstrated, with the contexts relevant in BCI, brain computer interfaces. Mathematical representations, invariants and complete characterization of structures in broad variety of biological signals are in the central focus.     

Optimization of Microwave-Assisted Extraction of Polyphenolic Compounds from <Emphasis Type="Italic">Ocimum basilicum</Emphasis> by Response Surface Methodology

Microwave-assisted extraction (MAE) was optimized by response surface methodology in order to enhance the extraction of polyphenols from basil (Ocimum basilicum L). Box–Behnken experimental design on three levels and three variables was used for optimization. Influence of ethanol concentration (50, 70, and 90%); microwave power (400, 600, and 800 W); and extraction time (15, 25, and 35 min) on each response were investigated. Experimental results were fitted to a second-order polynomial model, and multiple regression analysis and analysis of variance were used to evaluate model fitness and optimal conditions. Considering the maximum content of extracted total phenols, total flavonoids, and antioxidant activity, the optimal conditions for all investigated response were ethanol concentration of 50%, microwave power of 442 W, and extraction time of 15 min. Under the optimal conditions, obtained basil liquid extract contained 4.299 g gallic acid equivalents/100 g dry weight (DW) of total polyphenols, 0.849 g catechin equivalents/100 g DW of total flavonoids, and IC₅₀ and EC₅₀ values of 9.602 and 82.889 μg/mL, respectively. The development of simultaneous MAE procedure for extraction of total phenols, total flavonoids, and potential antioxidants from basil, represented valorization of basil as valuable source of bioactive compounds.     

Mathematical modelling of soybean oil solubility in supercritical carbon dioxide

The solubility of soybean oil in supercritical carbon dioxide has been determined in the pressure range of 100–300 bar and in the temperature range of 313–323 K. The obtained values (from 0.0005 to 0.02055 g L^?1) have been correlated using four different empirical equations proposed correspondingly by Chrastil, del Valle and Aquilera, Adachi and Lu and Sparks et al. Since the Sparks et al. equation provided the lowest average absolute relative deviation (AARD) (10.25%) than other models in the examined experimental range, a modified equation of Sparks et al. model was developed for predicting the solubility of soybean oil in supercritical carbon dioxide as a function of temperature and density. An improved equation showed the lowest deviation (2.15%) between experimental data than the other empirical equations considered in this study. The proposed equation was also applied for correlating the solubility of linoleic acid (AARD was 2.40%).     

Mass changes accompanying the pseudocapacitance of hydrous RuO2 under different experimental conditions

Pseudocapacitance reaction of hydrous ruthenium oxide was investigated by cyclic voltammetry combined with electrochemical quartz-crystal nanobalance (EQCN) in sulfuric acid as well as in neutral solutions of Na₂SO₄ and K₂SO₄. The ruthenium oxide electrode was prepared by attaching the ruthenium oxide particles on gold covered quartz electrode. The results show that there are different types of charge taking place simultaneously during the redox reaction of ruthenium oxide electrode. Their contribution to the overall charge depends on the experimental conditions. Depending on the potential and electrolyte used the redox reaction of ruthenium oxide is accompanied either by mass loss or by mass gain. The average molar masses of the species exchanged between the solid phase and the electrolyte solution depend on the potential and scan rate. The effect of Nafion™ top layer was also investigated. It has been found that it does not affect significantly the overall specific capacitance of ruthenium oxide electrode but the apparent molar masses of exchanged species decrease in comparison with the uncovered electrodes.