http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2013 , Hindawi Publishing Corporation . All rights reserved. Thu, 16 May 2013 11:42:15 +0000 http://www.hindawi.com/journals/jece/2013/240814/ This work presents a new efficient parallel carrier recovery architecture suitable for ultrahigh speed intradyne coherent optical receivers (e.g., ≥100 Gb/s) with quadrature amplitude modulation (QAM). The proposed scheme combines a novel low-latency parallel digital phase locked loop (DPLL) with a feedforward carrier phase recovery (CPR) algorithm. The new low-latency parallel DPLL is designed to compensate not only carrier frequency offset but also frequency fluctuations such as those induced by mechanical vibrations or power supply noise. Such carrier frequency fluctuations must be compensated since they lead to higher phase error variance in traditional feedforward CPR techniques, significantly degrading the receiver performance. In order to enable a parallel-processing implementation in multigigabit per second receivers, a new approximation to the DPLL computation is introduced. The proposed technique reduces the latency within the feedback loop of the DPLL introduced by parallel processing, while at the same time it provides a bandwidth and capture range close to those achieved by a serial DPLL. Simulation results demonstrate that the effects caused by frequency deviations can be eliminated with the proposed low latency parallel carrier recovery architecture. Pablo Gianni, Laura Ferster, Graciela Corral-Briones, and Mario R. Hueda Copyright © 2013 Pablo Gianni et al. All rights reserved. Sun, 12 May 2013 10:23:47 +0000 http://www.hindawi.com/journals/jece/2013/587108/ This paper presents an improved decision feedforward equalizer (DFFE) for high speed receivers in the presence of highly dispersive channels. This decision-aided equalizer technique has been recently proposed for multigigabit communication receivers, where the use of parallel processing is mandatory. Well-known parallel architectures for the typical decision feedback equalizer (DFE) have a complexity that grows exponentially with the channel memory. Instead, the new DFFE avoids that exponential increase in complexity by using tentative decisions to cancel iteratively the intersymbol interference (ISI). Here, we demostrate that the DFFE not only allows to obtain a similar performance to the typical DFE but it also reduces the compelxity in channels with large memory. Additionally, we propose a theoretical approximation for the error probability in each iteration. In fact, when the number of iteration increases, the error probability in the DFFE tends to approach the DFE. These benefits make the DFFE an excellent choice for the next generation of high-speed receivers. Ariel L. Pola, Juan E. Cousseau, Oscar E. Agazzi, and Mario R. Hueda Copyright © 2013 Ariel L. Pola et al. All rights reserved. Mon, 29 Apr 2013 09:07:33 +0000 http://www.hindawi.com/journals/jece/2013/741251/ Digital IIR filter implementations are important building blocks of most communication systems. The chosen number format (fixed-point, floating-point; precision) has a major impact on achievable performance and implementation cost. Typically, filter design for communication systems is based on filter specifications in the frequency domain. We consider IIR filter design as an integral part of communication system optimisation with implicit filter specification in the time domain (via symbol/bit error rate). We present a holistic design flow with the system's bit error rate as the main objective. We consider a discrete search space spanned by the quantised filter coefficients. Differential Evolution is used for efficient sampling of this huge finite design space. We present communication system performance (based on bit-true simulations) and both measured and estimated receiver IIR chip areas. The results show that very small number formats are acceptable for complex filters and that the choice between fixed-point and floating-point number formats is nontrivial if precision is a free parameter. Alexander Melzer, Andreas Pedross, and Manfred Mücke Copyright © 2013 Alexander Melzer et al. All rights reserved. Thu, 18 Apr 2013 17:01:04 +0000 http://www.hindawi.com/journals/jece/2013/568780/ Interconnection Network (IN) is a key element for all parallel processing applications. Multistage Interconnection Network (MIN) is an efficient IN for these applications, as it has the quality of excellent performance at low cost with high reliability. MINs are effective medium for message broadcasting. Doing the same task in faulty situations is a critical challenge. In this paper, we have presented a new Fault Tolerant Interconnection Network named as Irregular Advance Omega Network (IAON); also we have presented its routing algorithm. IAON is the modified form of Advance Omega Network. The proposed MIN can endure multiple faults and provides a suitable path between every source to every destination. We have examined the fault tolerance capacity of IAON and compared its performance with other existing MINs. In order to check the performance of proposed MIN, message broadcasting was performed in three conditions as follows: (1) when network was fault free; (2) when network was Single Switch Faulty in every stage; (3) when network was Double Switch Faulty in every stage. Results showed that IAON performed better than the earlier proposed MINs. Ved Prakash Bhardwaj and Nitin Copyright © 2013 Ved Prakash Bhardwaj and Nitin. All rights reserved. Tue, 16 Apr 2013 07:50:44 +0000 http://www.hindawi.com/journals/jece/2013/489515/ This paper presents a methodology for the preservation of audio documents, the operational protocol that acts as the methodology, and an original open source software system that supports and automatizes several tasks along the process. The methodology is presented in the light of the ethical debate that has been challenging the international archival community for the last thirty years. The operational protocol reflects the methodological principles adopted by the authors, and its effectiveness is based on the results obtained in recent research projects involving some of the finest audio archives in Europe. Some recommendations are given for the rerecording process, aimed at minimizing the information loss and at quantifying the unintentional alterations introduced by the technical equipment. Finally, the paper introduces an original software system that guides and supports the preservation staff along the process, reducing the processing timing, automatizing tasks, minimizing errors, and using information hiding strategies to ease the cognitive load. Currently the software system is in use in several international archives. Federica Bressan and Sergio Canazza Copyright © 2013 Federica Bressan and Sergio Canazza. All rights reserved. Mon, 15 Apr 2013 09:50:16 +0000 http://www.hindawi.com/journals/jece/2013/374165/ This paper presents a novel indoor navigation and ranging strategy via monocular camera. By exploiting the architectural orthogonality of the indoor environments, we introduce a new method to estimate range and vehicle states from a monocular camera for vision-based SLAM. The navigation strategy assumes an indoor or indoor-like manmade environment whose layout is previously unknown, GPS-denied, representable via energy based feature points, and straight architectural lines. We experimentally validate the proposed algorithms on a fully self-contained microaerial vehicle (MAV) with sophisticated on-board image processing and SLAM capabilities. Building and enabling such a small aerial vehicle to fly in tight corridors is a significant technological challenge, especially in the absence of GPS signals and with limited sensing options. Experimental results show that the system is only limited by the capabilities of the camera and environmental entropy. Koray Çelik and Arun K. Somani Copyright © 2013 Koray Çelik and Arun K. Somani. All rights reserved. Sun, 14 Apr 2013 10:25:03 +0000 http://www.hindawi.com/journals/jece/2013/948598/ Justinian Anatory, Moises V. Ribeiro, Andrea M. Tonello, and Ahmed Zeddam Copyright © 2013 Justinian Anatory et al. All rights reserved. Sun, 14 Apr 2013 09:13:41 +0000 http://www.hindawi.com/journals/jece/2013/908905/ Mosaics are images obtained by cementing together small colored fragments and are an ancient example of discrete primitive-based images. Artificial mosaics are illustrations composed by a set of small images called “tiles” that tessellate a source image aiming to reproduce the original visual information in a mosaic-like style. In this paper, we propose a mosaic generation technique based on gradient vector flow (GVF) together with a set of tile cutting heuristics evaluated according to aesthetic criteria. The effectiveness of the proposed approach has been confirmed by a series of tests and comparisons with state-of-the-art techniques. Sebastiano Battiato, Alfredo Milone, and Giovanni Puglisi Copyright © 2013 Sebastiano Battiato et al. All rights reserved. Wed, 03 Apr 2013 09:00:18 +0000 http://www.hindawi.com/journals/jece/2013/834793/ Transformation and quantization play a critical role in video codecs. Recently proposed algebraic-integer-(AI-) based discrete cosine transform (DCT) algorithms are analyzed in the presence of quantization, using the High Efficiency Video Coding (HEVC) standard. AI DCT is implemented and tested on asynchronous quasi delay-insensitive logic, using Achronix SPD60 field programmable gate array (FPGA), which leads to lower complexity, higher speed of operation, and insensitivity to process-voltage-temperature variations. Performance of AI DCT with HEVC is measured in terms of the accuracy of the transform coefficients and the overall rate-distortion (R-D) characteristics, using HM 7.1 reference software. Results indicate a 31% improvement over the integer DCT in the number of transform coefficients having error within 1%. The performance of the 65 nm asynchronous hardware in terms of speed of operation is investigated and compared with the 65 nm synchronous Xilinx FPGA. Considering word lengths of 5 and 6 bits, a speed increase of 230% and 199% is observed, respectively. These results indicate that AI DCT can be potentially utilized in HEVC for applications demanding high accuracy as well as high throughput. However, novel quantization schemes are required to allow the accuracy improvements obtained. Nilanka Rajapaksha, Amila Edirisuriya, Arjuna Madanayake, Renato J. Cintra, Dennis Onen, Ihab Amer, and Vassil S. Dimitrov Copyright © 2013 Nilanka Rajapaksha et al. All rights reserved. Sun, 31 Mar 2013 11:22:40 +0000 http://www.hindawi.com/journals/jece/2013/365692/ An analytical model and a methodology are presented for the analysis of CMOS injection-locked frequency dividers with direct injection, which are used in modern wireless communication systems. The amplitude and phase of the oscillation in the synchronous operation mode, as well as the locking range, are found in explicit form. The width of the locking range is determined by the condition of the existence and stability of synchronous oscillations. The accuracy of the model and of the presented formulas is validated through a comparison with experimental results, which are in good agreement with the analytical ones. Antonio Buonomo and Alessandro Lo Schiavo Copyright © 2013 Antonio Buonomo and Alessandro Lo Schiavo. All rights reserved. Thu, 28 Mar 2013 15:45:52 +0000 http://www.hindawi.com/journals/jece/2013/712376/ Power line communication, that is, using the electricity infrastructure for data transmission, is experiencing a renaissance in the context of Smart Grid. Smart Grid objectives include the integration of intermittent renewable energy sources into the electricity supply chain, securing reliable electricity delivery, and using the existing electrical infrastructure more efficiently. This paper surveys power line communications (PLCs) in the context of Smart Grid. The specifications G3-PLC, PRIME, HomePlug Green PHY, and HomePlug AV2, and the standards IEEE 1901/1901.2 and ITU-T G.hn/G.hnem are discussed. Lars Torsten Berger, Andreas Schwager, and J. Joaquín Escudero-Garzás Copyright © 2013 Lars Torsten Berger et al. All rights reserved. Mon, 25 Mar 2013 10:05:19 +0000 http://www.hindawi.com/journals/jece/2013/272341/ The key bottleneck for secondary spectrum usage is the aggregate interference to the primary system receivers due to simultaneous secondary transmissions. Existing power allocation algorithms for multiple secondary transmitters in the TV white space either fail to protect the TV service in all cases or they allocate extremely low power levels to some of the transmitters. In this paper, we propose a power allocation algorithm that favors equally the secondary transmitters and it is able to protect the TV service in all cases. When the number of secondary transmitters is high, the computational complexity of the proposed algorithm becomes high too. We show how the algorithm could be modified to reduce its computational complexity at the cost of negligible performance loss. The modified algorithm could permit a spectrum allocation database to allocate near optimal transmit power levels to tens of thousands of secondary transmitters in real time. In addition, we describe how the modified algorithm could be applied to allow decentralized power allocation for mobile secondary transmitters. In that case, the proposed algorithm outperforms the existing algorithms because it allows reducing the communication signalling overhead between mobile secondary transmitters and the spectrum allocation database. Konstantinos Koufos and Riku Jäntti Copyright © 2013 Konstantinos Koufos and Riku Jäntti. All rights reserved. Thu, 21 Mar 2013 15:47:52 +0000 http://www.hindawi.com/journals/jece/2013/402514/ Power Line Communication (PLC) is the response for nowadays high demand of multimedia services in domestic environment, not only for its fast and reliable transfer characteristics but also for its flexible low cost implementation, since the PLC technology uses the existing electrical network infrastructure and the omnipresent outlets throughout the home. The transfer of such a high bit rate through the mains network generates acceptable radiated emission regulated by international standards, but the increment in speed for new generation PLC may cause higher levels of emissions. This paper explains the use of the Time Reversal (TR) technique to mitigate radiated emissions from PLC systems. This method was probed experimentally in real electrical networks with excellent results: in 40% of the observations, the Electromagnetic Interference (EMI) generated by PLC transmission could be reduced by more than 3 dB, and this EMI mitigation factor could increase to more than 10 dB in particular configurations. Amilcar Mescco, Pascal Pagani, Michel Ney, and Ahmed Zeddam Copyright © 2013 Amilcar Mescco et al. All rights reserved. Thu, 21 Mar 2013 14:14:37 +0000 http://www.hindawi.com/journals/jece/2013/718574/ This paper proposes a real-time method for capturing and reproducing spatial audio based on a circular microphone array. Following a different approach than other recently proposed array-based methods for spatial audio, the proposed method estimates the directions of arrival of the active sound sources on a per time-frame basis and performs source separation with a fixed superdirective beamformer, which results in more accurate modelling and reproduction of the recorded acoustic environment. The separated source signals are downmixed into one monophonic audio signal, which, along with side information, is transmitted to the reproduction side. Reproduction is possible using either headphones or an arbitrary loudspeaker configuration. The method is compared with other recently proposed array-based spatial audio methods through a series of listening tests for both simulated and real microphone array recordings. Reproduction using both loudspeakers and headphones is considered in the listening tests. As the results indicate, the proposed method achieves excellent spatialization and sound quality. Anastasios Alexandridis, Anthony Griffin, and Athanasios Mouchtaris Copyright © 2013 Anastasios Alexandridis et al. All rights reserved. Tue, 19 Mar 2013 15:25:58 +0000 http://www.hindawi.com/journals/jece/2013/892628/ HomePlug AV2 is the solution identified by the HomePlug Alliance to achieve the improved data rate performance required by the new generation of multimedia applications without the need to install extra wires. Developed by industry-leading participants in the HomePlug AV Technical Working Group, the HomePlug AV2 technology provides Gigabit-class connection speeds over the existing AC wires within home. It is designed to meet the market demands for the full set of future in-home networking connectivity. Moreover, HomePlug AV2 guarantees backward interoperability with other HomePlug systems. In this paper, the HomePlug AV2 system architecture is introduced and the technical details of the key features at both the PHY and MAC layers are described. The HomePlug AV2 performance is assessed, through simulations reproducing real home scenarios. Larry Yonge, Jose Abad, Kaywan Afkhamie, Lorenzo Guerrieri, Srinivas Katar, Hidayat Lioe, Pascal Pagani, Raffaele Riva, Daniel M. Schneider, and Andreas Schwager Copyright © 2013 Larry Yonge et al. All rights reserved. Thu, 14 Mar 2013 18:48:37 +0000 http://www.hindawi.com/journals/jece/2013/189436/ The novel probabilistic models of the random variations in nanoscale MOSFET's high frequency performance defined in terms of gate capacitance and transition frequency have been proposed. As the transition frequency variation has also been considered, the proposed models are considered as complete unlike the previous one which take only the gate capacitance variation into account. The proposed models have been found to be both analytic and physical level oriented as they are the precise mathematical expressions in terms of physical parameters. Since the up-to-date model of variation in MOSFET's characteristic induced by physical level fluctuation has been used, part of the proposed models for gate capacitance is more accurate and physical level oriented than its predecessor. The proposed models have been verified based on the 65 nm CMOS technology by using the Monte-Carlo SPICE simulations of benchmark circuits and Kolmogorov-Smirnov tests as highly accurate since they fit the Monte-Carlo-based analysis results with 99% confidence. Hence, these novel models have been found to be versatile for the statistical/variability aware analysis/design of nanoscale MOSFET-based analog/mixed signal circuits and systems. Rawid Banchuin Copyright © 2013 Rawid Banchuin. All rights reserved. Thu, 07 Mar 2013 13:47:15 +0000 http://www.hindawi.com/journals/jece/2013/179538/ The design of nanometric electronic devices requires novel materials for improving their electrical performance from stages of design until their fabrication. Until now, several DC electrical conductivity models for composite materials have been proposed. However, these models must be valued to identify main design parameters that more efficiently control the electrical properties of the materials to be developed. In this paper, four different models used for modeling DC electrical conductivity of carbon nanotube-polymer composites are studied with the aim of obtaining a complete list of design parameters that allow guarantying to the designer an increase in electrical properties of the composite by means of carbon nanotubes. Rafael Vargas-Bernal, Gabriel Herrera-Pérez, Ma. Elena Calixto-Olalde, and Margarita Tecpoyotl-Torres Copyright © 2013 Rafael Vargas-Bernal et al. All rights reserved. Tue, 05 Mar 2013 11:14:23 +0000 http://www.hindawi.com/journals/jece/2013/679032/ MIMO OFDM is a very promising technique for future wireless communication systems. By applying direct conversion architecture, low-cost, low-power, small size, and flexible implementation of MIMO OFDM systems can be realized. However, the performance of direct conversion architecture-based MIMO OFDM systems can be seriously affected by RF impairments incling carrier frequency offset (CFO) and I/Q-imbalance. While OFDM is sensitive to CFO, direct conversion architecture is sensitive to I/Q imbalance. Such RF impairments aggravate as the carrier frequency becomes higher for example, beyond 60 GHz. To achieve the desired high performance of MIMO OFDM, such RF impairments have to be compensated for. In this paper, the joint compensation of CFO, transmitter and receiver frequency-selective I/Q imbalance, and the MIMO radio channel is investigated. Two preamble-based schemes are proposed for impairment parameter estimation. The proposed preambles are constructed both in time and frequency domains and require much less overhead than the state-of-the-art designs. Furthermore, much lower computational complexity is allowed, enabling efficient implementation. The advantages and effectiveness of both proposed schemes are compared and verified by numerical simulations and complexity analysis. Jian Luo, Wilhelm Keusgen, and Andreas Kortke Copyright © 2013 Jian Luo et al. All rights reserved. Tue, 26 Feb 2013 08:38:05 +0000 http://www.hindawi.com/journals/jece/2013/973813/ The microelectronics area constantly demands better and improved circuit simulation tools. Therefore, in this paper, rational homotopy perturbation method and Boubaker Polynomials Expansion Scheme are applied to a differential equation from a nonlinear circuit. Comparing the results obtained by both techniques revealed that they are effective and convenient. H. Vazquez-Leal, K. Boubaker, L. Hernandez-Martinez, and J. Huerta-Chua Copyright © 2013 H. Vazquez-Leal et al. All rights reserved. Thu, 14 Feb 2013 17:10:36 +0000 http://www.hindawi.com/journals/jece/2013/129589/ Circuits and systems able to process high quality video in real time are fundamental in nowadays imaging systems. The circuit proposed in the paper, aimed at the robust identification of the background in video streams, implements the improved formulation of the Gaussian Mixture Model (GMM) algorithm that is included in the OpenCV library. An innovative, hardware oriented, formulation of the GMM equations, the use of truncated binary multipliers, and ROM compression techniques allow reduced hardware complexity and increased processing capability. The proposed circuit has been designed having commercial FPGA devices as target and provides speed and logic resources occupation that overcome previously proposed implementations. The circuit, when implemented on Virtex6 or StratixIV, processes more than 45 frame per second in 1080p format and uses few percent of FPGA logic resources. Mariangela Genovese, Ettore Napoli, Davide De Caro, Nicola Petra, and Antonio G. M. Strollo Copyright © 2013 Mariangela Genovese et al. All rights reserved. Sun, 10 Feb 2013 11:07:24 +0000 http://www.hindawi.com/journals/jece/2013/635086/ We consider the design of the front-end receiver for broadband power line communications. We focus on the design of the input impedance that maximizes the signal-to-noise ratio (SNR) at the receiver. We show that the amplitude, rather than the power, of the received signal is important for communication purposes. Furthermore, we show that the receiver impedance impacts the amplitude of the noise term. We focus on the background noise, and we propose a novel description of the noise experienced at the receiver port of a PLC network. We model the noise as the sum of four uncorrelated contributions, that is, the active, resistive, receiver, and coupled noise components. We study the optimal impedance design problem for real in-home grids that we assessed with experimental measurements. We describe the results of the measurement campaign, and we report the statistics of the optimal impedance. Hence, we study the best attainable performance when the optimal receiver impedance is deployed. We focus on the SNR and the maximum achievable rate, and we show that power matching is suboptimal with respect to the proposed impedance design approach. Massimo Antoniali, Andrea M. Tonello, and Fabio Versolatto Copyright © 2013 Massimo Antoniali et al. All rights reserved. Tue, 05 Feb 2013 13:48:31 +0000 http://www.hindawi.com/journals/jece/2013/328395/ Yi Su, Fangwen Fu, and Shuo Guo Copyright © 2013 Yi Su et al. All rights reserved. Tue, 05 Feb 2013 13:37:34 +0000 http://www.hindawi.com/journals/jece/2013/908906/ Heesung Kwon, Xiaofei Hu, James Theiler, Alina Zare, and Prudhvi Gurram Copyright © 2013 Heesung Kwon et al. All rights reserved. Thu, 31 Jan 2013 15:03:39 +0000 http://www.hindawi.com/journals/jece/2013/715816/ In cognitive radio ad hoc networks, a frequently changing environment, varying channel occupancy statistics, and heterogeneous spectrum availability result in a need to meet on a common channel and to initiate a communication. This process of two or more CRs, meeting each other in the same channel, is called a rendezvous (RDV). RDV is essential for establishment of a communication link. Hence, methods guaranteeing that all nodes meet periodically in reasonable periods of time should be developed. In this study, we evaluate a torus Quorum System (QS) and Difference Set (DS) based rendezvous protocol in an asymmetric channel view case (heterogeneous channel availability). Regardless of the diversity of channels of CRs the protocol guarantees RDV on either all channels or almost all channels. Furthermore, the nodes meet multiple times on different channels in a period, which increases the chance of successful establishment of a communication link. Sylwia Romaszko Copyright © 2013 Sylwia Romaszko. All rights reserved. Wed, 30 Jan 2013 07:39:59 +0000 http://www.hindawi.com/journals/jece/2013/746763/ To enable the smart grid concept, it is fundamental to consider the in-home/building context where, beside the conventional home networking services, home automation and smart energy management services have to be offered. In this paper, we consider the in-home/building scenario, for which we propose a convergent network architecture to enhance the performance of the narrowband power line communication (PLC) G3-PLC technology through its integration with an Ethernet-based network. To this end, we define the protocols characterizing the network modules, namely, switches and routers, which allow for integrating the G3-PLC with Ethernet devices. Since Ethernet represents a convergent standard for many communication devices, by adding this functionality to G3-PLC, interconnectivity with other heterogeneous nodes can be offered. Furthermore, since the G3-PLC medium access control layer is based on a carrier sense multiple access scheme, its performance decreases when the number of network nodes contending for the channel increases. Therefore, we evaluate the network performance when an optimized time division multiple access scheme is adopted. The proposed convergent network architecture has been implemented in the OMNeT++ network simulator. Luca Di Bert, Salvatore D'Alessandro, and Andrea M. Tonello Copyright © 2013 Luca Di Bert et al. All rights reserved. Sun, 30 Dec 2012 16:04:54 +0000 http://www.hindawi.com/journals/jece/2012/753541/ This paper reviews quorum systems (QS) from the perspective of cognitive radio networks. Quorum systems were originally developed for and widely used in the scope of operating systems. Recently, quorum systems have been also started to be applied to wireless communications. The objective of this paper is threefold. First, the paper provides survey and guidance on the use of quorum systems. Second, it shows that QS properties provide an interesting alternative towards an asynchronous communication in cognitive radio ad hoc networks (CRANs). Due to properties of quorum systems it is possible to establish CRANs without employing a common control channel (CCC), perfect synchronization, or central controller architecture. QS properties can be efficiently utilized to handle the rendezvous (RDV) problem in CRANs. New RDV protocols must be designed in such a way that there is a guarantee that all nodes meet periodically within reasonable periods of time. Since pseudorandom solutions do not provide this guarantee, systematic approaches are needed such as QSs. Third, we also propose a novel distributed RDV protocol, MtQS-DSrdv, which is based on mirror torus QS and difference set concepts. The proposed protocol guarantees RDVs on all available channels while CR nodes have the same channel set. Sylwia Romaszko and Petri Mähönen Copyright © 2012 Sylwia Romaszko and Petri Mähönen. All rights reserved. Sat, 29 Dec 2012 15:51:33 +0000 http://www.hindawi.com/journals/jece/2012/214012/ Charalampos C. Tsimenidis, Yuriy Zakharov, Christophe Laot, Konstantinos Pelekanakis, Paolo Casari, and Andrey K. Morozov Copyright © 2012 Charalampos C. Tsimenidis et al. All rights reserved. Tue, 18 Dec 2012 07:57:55 +0000 http://www.hindawi.com/journals/jece/2012/802606/ In the context of Long-Term Evolution (LTE), the next generation mobile telecommunication network, femtocells are low-power base stations that efficiently provide coverage and capacity indoors. This paper presents a computationally efficient dynamic system-level LTE simulator for enterprise femtocell scenarios. The simulator includes specific mobility and traffic and propagation models for indoor environments. A physical layer abstraction is performed to predict link-layer performance with low computational cost. At link layer, two important functions are included to increase network capacity: Link Adaptation and Dynamic Scheduling. At network layer, other Radio Resource Management functionalities, such as Admission Control and Mobility Management, are also included. The resulting tool can be used to test and validate optimization algorithms in the context of Self-Organizing Networks (SON). J. M. Ruiz-Avilés, S. Luna-Ramírez, M. Toril, F. Ruiz, I. de la Bandera, P. Muñoz, R. Barco, P. Lázaro, and V. Buenestado Copyright © 2012 J. M. Ruiz-Avilés et al. All rights reserved. Thu, 13 Dec 2012 14:08:57 +0000 http://www.hindawi.com/journals/jece/2012/879626/ Fast windowed update algorithms capable of independently updating the odd discrete cosine transform (ODCT) and odd discrete sine transform (ODST) of a running data sequence are analytically developed. In this algorithm, to compute the ODCT coefficients of a real-time sequence, we do not require the ODST coefficients. Similarly, the ODST coefficients of the shifted sequence can be calculated without using ODCT coefficients. The running input data sequence is sampled using a rectangular window. However, this idea can be easily extended for other windows. The update algorithm derived herein can be used to compute the transform coefficients of the shifted sequence as new data points are available. The complexity of developed algorithm is . The validity of algorithm is tested by MATLAB simulations. S. Akhter, V. Karwal, and R. C. Jain Copyright © 2012 S. Akhter et al. All rights reserved. Tue, 04 Dec 2012 13:12:21 +0000 http://www.hindawi.com/journals/jece/2012/372572/ A phenomenal increase in the number of wireless devices has led to the evolution of several interesting and challenging research problems in opportunistic networks. For example, the random waypoint mobility model, an early, popular effort to model mobility, involves generating random movement patterns. Previous research efforts, however, validate that movement patterns are not random; instead, human mobility is predictable to some extent. Since the performance of a routing protocol in an opportunistic network is greatly improved if the movement patterns of mobile users can be somewhat predicted in advance, several research attempts have been made to understand human mobility. The solutions developed use our understanding of movement patterns to predict the future contact probability for mobile nodes. In this work, we summarize the changing trends in modeling human mobility as random movements to the current research efforts that model human walks in a more predictable manner. Mobility patterns significantly affect the performance of a routing protocol. Thus, the changing trend in modeling mobility has led to several changes in developing routing protocols for opportunistic networks. For example, the simplest opportunistic routing protocol forwards a received packet to a randomly selected neighbor. With predictable mobility, however, routing protocols can use the expected contact information between a pair of mobile nodes in making forwarding decisions. In this work, we also describe the previous and current research efforts in developing routing protocols for opportunistic networks. Aarti Munjal, Tracy Camp, and Nils Aschenbruck Copyright © 2012 Aarti Munjal et al. All rights reserved.