Vol. 69, n° 9-10, September-October 2014
Content available on Springerlink
Compact notch loaded half disk patch antenna for dualband operation
Ashish Singh, Jamshed Aslam Ansari, Kumari Kamakshi, Anurag Mishra and Mohammad Aneesh
University of Allahabad, India
Abstract In this article, microstrip patch antenna loaded with two symmetrical vertical notches and shorting pin is investigated for dualband operation using circuit theory concept based on modal expansion cavity model. It is found that the antenna resonates at 2.84 and 6.33 GHz for upper and lower resonance frequencies respectively. The bandwidth of the compact notch loaded antenna at lower resonance frequency is 9.94 % (theoretical) and 6.67 % (simulated) whereas at upper resonance frequency, it is 12.99 % (theoretical) and 11.59 % (simulated). The compact notch loaded antenna characteristics are compared with other proposed radiating structures. The theoretical results are compared with IE3D simulation as well as reported experimental results and they are in close agreement.
Keywords Microstrip patch antennas (MSA) – Semi-circular disk – Notches – Shorting pin
Impact of IPv4-IPv6 coexistence in cloud virtualization environment
Kyung Hee University, Suwon, South Korea
Abstract Since January 2011, the IPv4 address space has been exhausted and IPv6 is taking up the place as its successor. Coexistence of IPv4 and IPv6 bears problem of incompatibility, as IPv6 and IPv4 headers are different from each other, thus, they cannot interoperate with each other directly. The IPv6 transitioning techniques are still not mature, causing hindrance in the deployment of IPv6 and development of next generation Internet. Until IPv6 completely takes over from IPv4, they will both coexist. For IPv4–IPv6 coexistence, the following three solutions are possible: (a) making every device dual stack, (b) translation, or (c) tunneling. Tunneling stands out as the best possible solution. Among the IPv6 tunneling techniques, this paper evaluates the impact of three recent IPv6 tunneling techniques: 6to4, Teredo, and ISATAP, in cloud virtualization environment. In virtual networks, these protocols were implemented on Microsoft Windows (MS Windows 7 and MS Windows Server 2008) and Linux operating system. Each protocol was implemented on the virtual network. UDP audio streaming, video streaming and ICMP-ping traffic was run. Multiple runs of traffic were routed over the setup for each protocol. The average of the data was taken to generate graphs and final results. The performance of these tunneling techniques has been evaluated on eight parameters, namely: throughput, end to end delay, jitter, round trip time, tunneling overhead, tunnel setup delay, query delay, and auxiliary devices required. This evaluation shows the impact of IPv4–IPv6 coexistence in virtualization environment for cloud computing.
Semi-blind amplify-and-forward in two-way relaying networks
Wided Hadj Alouane, Noureddine Hamdi, and Soumaya Meherzi
ENIT, El Manar University, Tunis, Tunisia
Abstract This paper addresses the analysis of a two-way semi-blind amplify-and-forward (AF) relay network, in which the relay node requires partial instantaneous channel state information (CSI) to amplify the received signals. First, we derive the expression of end-to-end signal-to-noise ratio in dual-hop transmissions over independent and not necessarily identically distributed Rayleigh fading channels. Based on the opportunistic AF selection relaying, we define bounds of some metrics such as average sum-rate and outage probability. Furthermore, we provide exact and approximate expressions for the average symbol error rate. The obtained results show that the performance of the proposed system decreases slightly while the processing complexity is reduced significantly compared to those of CSI-assisted AF relay schemes. In order to prove the exactness of the proposed analysis, a selection of numerical results is provided.
Keywords Two-way – Relaying – Semi-blind – Sum-rate – Outage probability – SER
A modified PSO technique using heterogeneous boundary conditions for broadband compact microstrip antenna designing
S. Kibria, M. T. Islam, B. Yatim, and R. Azim
Universiti Kebangsaan Malaysia, Bangi, Malaysia
Abstract A modified particle swarm optimization (PSO) variant is implemented on a conventionally optimized broadband antenna. Proposed algorithm uses heterogeneous boundary conditions to particles that fly out of the search space. Search space boundary conditions were chosen depending on which bound was violated. The algorithm is executed using MATLAB for the PSO computations and IE3D. Microstrip antennae inherently suffer from low bandwidth. Thus, a broadband patch antenna is optimized to improve the antenna return loss bandwidth in order to validate the proposed algorithm. For the patch antenna, a significant 12 % bandwidth improvement and 20.84 % size reduction was achieved. It was fabricated and satisfactory conformity was found with simulated results.
Keywords PSO – Microstrip antenna – Boundary condition – Search space – Optimization
Combination of fast Fourier transform and self-adaptive differential evolution algorithm for synthesis of phase-only reconfigurable rectangular array antenna
(2) Department of Electronics and Communication Engineering, National Institute of Technology, Durgapur, India
Abstract Reconfigurable antenna arrays are often capable of radiating multiple patterns by altering the excitation phases of the array elements. In this paper, an efficient method based on FFT is presented for generating dual-radiation pattern from a single rectangular planar array by modifying the excitation phases of the array elements while sharing common amplitudes. The common amplitudes shared by both the patterns and the phases which play the role of turning between the two patterns when updated over zero phase among the elements are computed using Self-adaptive Differential Evolution (SaDE) algorithm. Two different beam-pairs of pencil/pencil and pencil/flat-top are generated from the proposed array while maintaining precise design specifications. The proposed method greatly reduces the computational time as compared with the conventional method for calculating beam patterns. The dynamic range ratio of the excitation amplitudes are kept below a threshold level to reduce the design complexity of the attenuators at the feed network level and to minimize the effect of mutual coupling among the array elements. To illustrate the effectiveness of SaDE, the fitness functions associated with the two beam-pairs are minimized individually using differential evolution (DE) algorithm and particle swarm optimization (PSO) algorithm. Results clearly show the superiority of SaDE over DE and PSO to handle the proposed problem.
An efficiently implementable maximum likelihood decoding algorithm for tailbiting codes
(2) Universidad de Zaragoza, Spain
Abstract Convolutional tailbiting codes are widely used in mobile systems to perform error-correcting strategies of data and control information. Unlike zero tail codes, tailbiting codes do not reset the encoder memory at the end of each data block, improving the code efficiency for short block lengths. The objective of this work is to propose a low-complexity maximum likelihood decoding algorithm for convolutional tailbiting codes based on the Viterbi algorithm. The performance of the proposed solution is compared to that of another maximum likelihood decoding strategy which is based on the A* algorithm. The computational load and the memory requirements of both algorithms are also analysed in order to perform a fair comparison between them. Numerical results considering realistic transmission conditions show the lower memory requirements of the proposed solution, which makes its implementation more suitable for devices with limited resources.
On the energy efficiency of base station cooperation under limited backhaul capacity
CEA, LIST, Gif-sur-Yvette, France
Abstract Recently, energy-efficient (EE) communications have received increasing interest specially in cellular networks. Promising techniques, such as multiple input multiple output (MIMO) and base station (BS) cooperation schemes, have been widely studied in the past to improve the spectral efficiency and the reliability. Nowadays, the purpose is to investigate how these techniques can reduce the energy consumption of the systems. In this paper, we address for a single-user scenario, the energy efficiency of two BSs cooperation under limited backhaul capacity. In order to evaluate the EE metric, we provide first an information-theoretical analysis based on the outage probability, for a quantization model over the backhaul. Then, we extend this EE analysis to a more practical approach with data transmission over the backhaul. For both approaches, we identify by numerical/simulation results the cooperation scenarios that can save energy depending on the backhaul capacity.
Robust antenna array calibration and accurate angle estimation based on least trimmed squares
(2) School of Business Administration, Ajou University, Suwon, South Korea
Abstract A robust antenna array calibration and single target angle estimation algorithm is proposed. The proposed algorithm is based on the least trimmed squares algorithm and operates in two steps. First, the conventional least squares algorithm is used to estimate the intermediate phases (or angle) and the residual values at each element are calculated. In the second step, it excludes large residual elements and uses only the smallest of them, which prevents large errors during the angle estimation. The least trimmed-based phase difference approximation algorithm is simple to implement and is a practical way of mitigating errors at the antenna elements that are due to hardware and imperfect calibration. The results demonstrate that our proposed algorithm is robust and outperforms other algorithms in three scenarios.
Compressive slow-varying wideband power spectrum sensing for cognitive radio
(2) University of Electronic Science and Technology of China, China
Abstract Wideband spectrum sensing is a critical component of a functioning cognitive radio system. Its major challenge is the too high sampling rate requirement. Compressive sensing (CS) promises to be able to deal with it. Nearly all the current CS-based compressive wideband spectrum sensing methods exploit only the frequency sparsity to perform. This paper sets up a new signal model which is sparse in both temporal and frequency domain. Motivated by the achievement of a fast and robust detection of the wideband spectrum change, total variation minimization is incorporated to exploit the temporal and frequency structure information to enhance the sparsity level. As a sparser vector is obtained, the spectrum sensing period would be shortened and sensing accuracy would be enhanced. Both theoretical analysis and numerical experiments demonstrate the performance improvement.