Low complexity joint estimation of synchronization impairments in sparse channel for MIMO–OFDM system

Low complexity joint estimation of synchronization impairments and channel in a single-user MIMO–OFDM system is presented in this paper. Based on a system model that takes into account the effects of synchronization impairments such as carrier frequency offset, sampling frequency offset, and symbol timing error, and channel, a Maximum Likelihood (ML) algorithm for the joint estimation is proposed. To reduce the complexity of ML grid search, the number of received signal samples used for estimation need to be reduced. The conventional channel estimation techniques using Least-Squares (LS) or Maximum a posteriori (MAP) methods fail for the reduced sample under-determined system, which results in poor performance of the joint estimator. The proposed ML algorithm uses Compressed Sensing (CS) based channel estimation method in a sparse fading scenario, where the received samples used for estimation are less than that required for an LS or MAP based estimation. The performance of the estimation method is studied through numerical simulations, and it is observed that CS based joint estimator performs better than LS and MAP based joint estimator.     

Thermal properties of channel optical waveguides based on sol–gel materials

Temperature characteristics of various channel waveguides fabricated using the sol–gel technology are analyzed. It is shown that the limitation of transverse sizes of waveguides leads to significant variations in the temperature characteristics due to field concentration in the sol–gel material of the waveguide, which depends on the type of the channel waveguide and its parameters (geometrical sizes and refractive index of the sol–gel material). Recommendations on the selection of the type of waveguide and its parameters for specific applications in multiplexers, switches, optical cavities, etc. are presented.     

Design of band–notched UWB antenna using a hybrid optimization based on ABC and DE algorithms

In this study, a novel UWB antenna with dual band–rejection is designed by using a new hybrid optimization algorithm based artificial bee colony algorithm (ABC) and differential evolution (DE). The hybrid performance of ABC and DE (H–ABCDE) is tested on well–known benchmark functions. To show its performance on a design problem, an optimization interface (OI) which simultaneously communicates with H–ABCDE and an electromagnetic simulation tool is developed. Hence OI integrating H–ABCDE and HyperLynx® 3D EM is used to design and optimize an antenna. A low profile UWB monopole antenna operating over the frequency range of 2.9–13.0 GHz is then designed through OI. In order to achieve band–rejection operation, various slits and strips have been loaded on the antenna. It thus rejects the dual–band of 3.3–3.6 GHz and 5.15–5.825 GHz corresponds to the operation bands of WLAN and WiMAX. Furthermore, the optimized antenna is prototyped to investigate the measurement performance and it is compared with several designs in the literature. Therefore, H–ABCDE can successfully adapt to the extended electromagnetic problem as well as engineering optimization tasks.     

DVFS-aware motion estimation design scheme based on bandwidth–rate–distortion optimization in application processor systems

In this paper, a novel dynamic voltage–frequency scaling-aware (DVFS-aware) bandwidth- efficient motion estimation (ME) scheme is presented for mobile application processor (AP) systems. Under volatile operating performance conditions due to the power management mechanism, we model the coding bandwidth (BW) and coding performance for the video processor as a convex function of the working frequency. In this paper, we present a bandwidth–rate–distortion (B–R–D) optimized framework that will guarantee the smallest possible rate–distortion cost among coding BW constraints applied in video coding design. By formulating the coding bandwidth-constrained ME problem as an optimization problem, known convex optimization theory can be applied to yield optimal resource-constrained compression. Using varied CIF (352×288)- and HP (1280×720)-sized video sequences with different motion activities over our proposed DVFS-aware video coding approach, the excellent results in terms of coding performance and coding bandwidth savings are obtained. With negligible quality loss, the proposed scheme under coding BW constraints achieves 45–65% coding BW usage reduction over HD-sized 30 frame/s video coding.     

Optical flow estimation based on the structure–texture image decomposition

Optical flow approaches for motion estimation calculate vector fields which determine the apparent velocities of objects in time-varying image sequences. Image motion estimation is a fundamental issue in low-level vision and is used in many applications in image sequence processing, such as robot navigation, object tracking, image coding and structure reconstruction. The accuracy of optical flow estimation algorithms has been improving steadily as evidenced by results on the Middlebury optical flow benchmark. Actually, several methods are used to estimate the optical flow, but a good compromise between computational cost and accuracy is hard to achieve. This work presents a combined local–global total variation approach with structure–texture image decomposition. The combination is used to control the propagation phenomena and to gain robustness against illumination changes, influence of noise on the results and sensitivity to outliers. The resulted method is able to compute larger displacements in a reasonable time.     

Joint decoding of convolution codes and estimation of multipath communication channel’s parameters on a sliding interval

Optimal and quasi-optimal non-linear recurrent algorithms of joint decoding of convolution code and estimation of unknown multipath communication channel’s parameters on a sliding interval are synthesized on the basis of mathematics technique of mixed Markov processes in discrete time. Analysis of the obtained quasi-optimal algorithm is performed using statistical modeling on PC.     

Generation of orthogonal UWB shaping pulses based on compressed chirp signal

This study investigates a novel method to numerically generate orthogonal ultrawide band (UWB) shaping pulses based on compressed chirp signal. First, a pulse template with less than 1 ns duration time, which is used to construct a Hermitian matrix, is produced with a compressed chirp pulse. Sub-nanosecond orthogonal pulses are then generated for UWB by using the Hermitian matrix eigenvectors. The simulation results show that the power spectral density distribution of the UWB shaping pulses met the constraint of Federal communications commissions (FCC) spectral mask. The shaping pulses not only have higher spectrum utilization ratio and very short time duration but also have excellent autocorrelation and cross-correlation properties, which is an advantage to reduce the interference between multiusers. Especially, a method to produce sub-nanosecond orthogonal UWB shaping pulses by using a relatively longer duration chirp signal is presented.     

Resource optimization in distributed cooperative multi-relay system based on STBC-OFDM

On the basis of the amplify-and-forward relaying mode, a two-hop distributed cooperative multi-relay system is proposed combining with the space-time block coding OFDM (STBC-OFDM) technique. Taking the maximum end-to-end data rate as optimization criterion, the signal-to-noise ratio (SNR) of receiving terminal is deduced. On the basis of the water-filling theory, the optimal power allocation (OPA) is achieved for each subcarrier in each antenna and each relay node (RN) of the two-hop, to realize the resource optimization. Monte Carlo method is adopted in simulation. The simulation results show that compared with the uniform resource allocation scheme, the proposed OPA strategy can improve the system capacity. And the energy consumption of each transmission bit will be decreased, indicating the improvement of resource efficiency. In the scenario that the total power is limited, the system performance can be enhanced further by the distributed cooperative multi-relay through the diversity gain.     

Design of a 1 × 2 novel optical switch based on polarization converters and splitters

In this paper, a 1?×?2 optical switch based on two TE/TM polarization converters, one 1?×?2-polarization beam splitter and a hybrid 2?×?2-polarization beam splitter/combiner is designed and discussed. The novelty of this work resides in the design of a 2?×?2-hybrid polarization beam combiner/splitter, operating as a 2?×?2 polarization optical switch through the combining and the splitting of polarized signals issued from two TE/TM polarization controllers. The novel hybrid splitter/combiner can route an optical signal either to a bar or a cross port with an extinction ratio higher than 90 dB, thanks to the feature of polarization splitting used in this device to suppress undesired polarization states and minimize the polarization-dependent loss. We have used polarization beam converters to switch between two orthogonal modes in order to facilitate the routing of these signals through the 2?×?2-hybrid polarization splitter/combiner. We changed the polarization states of signals, in our simulation via OptiSystem, through polarization controllers, by modifying only their phase shifts between 0 rad and π rad. The proposed 1?×?2 optical switch presents an average insertion loss of 3.5 dB.

     

Method of the estimation of the parameters of a variable length Markov chain based on Fisher’s exact test

A method of the estimation of the parameters of a variable length Markov chain based on the use of Fisher’s exact test is proposed. The method has been applied to the problem of classification of convolutionally coded binary signals. Computer simulation has shown that the constructed models have a considerably smaller number of parameters as compared to the models based on the Kullbak-Leibler criterion, which is very popular in constructing variable-order Markov models.     

Direction-of-arrival estimation based on spatial–temporal statistics without knowing the source number

Direction-of-arrival (DOA) estimation is a central problem in array processing and has a variety of applications. In this paper, a new algorithm for finding DOAs of multiple temporally correlated signals is devised. The proposed approach is based on the joint diagonalization structure of a set of spatio-temporal correlation matrices. Unlike the subspace-based DOA estimators, it is not necessary to estimate the noise or signal subspace explicitly. Moreover, the proposed method can provide the spatial spectrum and estimate the DOAs even when the number of sources is not known a priori. Interestingly, it is revealed that the well-known MUSIC method is a special case of our algorithm. Simulation results validate that the developed approach is superior to conventional DOA estimators in terms of resolution capability, estimation accuracy, and robustness against array model errors.     

Time–space MIMO system with faster-than-nyquist signaling in frequency-selective fading channel

Multidimensional Systems and Signal Processing - The time–space receive transformation (TSRT) is proposed to increased the achievable rate of the time–space...     

Pulse shape optimization for physical layer UWB communication and performance evaluation in Saleh–Valenzuela channel IEEE 802.15.3a

Ultra-Wideband communication faces constraints on radiated power from regulatory bodies to minimize the co-existing interference with the narrowband communication. These limitations cause sacrifices in terms of data rate. In this paper, a new methodology of pulse shaping is proposed to meet the spectrum mask given by Federal Communication Commission (FCC). This methodology acutely reduces the undesired ringing effect in the time domain which in turn reduces the required power per unit bandwidth of the signal. We select 7th order derivative of Gaussian monocycle as a base pulse and modulate this pulse with Gaussian window in the time domain to achieve the proposed pulse shape. The power spectral density (PSD) of the proposed pulse is perfectly fitted for spectral mask provided by FCC, in comparison of PSD of the base pulse, which in turn simultaneously provides better antenna power resolution due to the reduced ringing effect in the time domain for the proposed pulse. We also analyse the behaviour of the pulse in multi-user Time Hopped (TH) UWB environment for Saleh Valenzuela IEEE 802.15.3a multipath fading channel to find the suitability of the pulse for UWB communication.     

Performance analysis of a rate adaptive multi-band ultra-wideband system based on quadrature fractal modulation scheme

1 Introduction Wornell and Oppenheim[1,2] first proposed a modulation technique as an interesting potential application of dy-homogeneous signals. Due to the fractal properties of the homogeneous signals, this technique is called fractal modulation afterwards. This class of homogeneous signals remains invariant under scaling of the time axis. Dy-homogeneous signals satisfy the dyadic self-similarity property[3] s (t ) = 2 kH s (2 kt) (1) For all integers k and a constant H, termed the degree…     

Direction of arrival estimation of sources with intersecting signature in time–frequency domain using a combination of IF estimation and MUSIC algorithm

Time–frequency (TF) approaches are frequently employed for source localization at low signal to noise ratio. However, TF approaches fail to achieve the desired performance for sparsely sampled signals or signals corrupted by heavy noise in an under-determined scenario when sources are not TF separable. In this study, we propose a new TF method for direction of arrival (DOA) estimation of sources with closely spaced and overlapping TF signature. The proposed method uses a combination of a high-resolution time–frequency distribution and instantaneous frequency estimation method for extraction of sources with intersecting and closely spaced time–frequency signatures. Once sources are extracted, their DOAs are estimated using a well known multiple signal classification (MUSIC) algorithm. Experimental results demonstrate that the proposed source localization method achieves better performance as compared to the conventional time–frequency MUSIC algorithm.

     

Research and design of wap service system based on MISC platform

1 Introduction With the introduction of high mobile handsets with increasingly powerful functions and the applications of WAP2.0 with considerably novel technologies, a series of diverse hot WAP services have come into being and have been successfully lau…     

Development of MIMO–OFDM system and forward error correction techniques since 2000s

The multi-input multi-output–orthogonal frequency division multiplexing (MIMO–OFDM) system serves as one of the most promising techniques that support high data rate and high performance in diverse fading channel conditions. The paper presents an overview of MIMO–OFDM wireless technology, covering advances in physical-layer design, various space–time codes, space–frequency codes and efficient concatenated forward error correction techniques, along with interleaving to yield reduced bit error rate performance (BER). Further, the paper presents the evolution of various performance metrics that are reported since the 2000s in the literature. The evolution outcome is examined using a quadratic nonlinear fitting function to assess the interesting performance metrics. Since BER versus SNR analysis is found as the interesting performance study of the MIMO–OFDM system, the current status of the achieved BER under varying SNR is reviewed and presented.     

Design and simulation of novel TLG–SET based configurable logic cells

Single electron tunneling circuits seem to be promising candidates as basic circuit elements of the next generation ultra-dense VLSI and ULSI circuits for their ultra-low power consumption, ultra-small size, and rich functionality. In this paper, design and simulation of novel configurable logic cells (CLCs) using single electron tunneling (SET) technology based threshold logic gate (TLG) are presented. The proposed CLC can realize all Boolean logic functions by configuring the control bits without changing the structure of the circuit and the parameters of TLG–SET based design. The logic operation of the circuit is simulated using Monte Carlo simulation. According to the simulation results, the circuit operation based on the transfer of single electrons between adjacent islands is stable.     

QSM-IDM – A novel quadrature spatial modulation based on interleaving division multiplexing for multiple antenna system

Quadrature Spatial Modulation (QSM) is a high spectral efficiency Multiple-Input Multiple Output (MIMO) technique used to improve the spectral efficiency of wireless communication systems. The main concept of QSM is to extend the spatial constellation of the conventional Spatial Modulation (SM) in both the in-phase and quadrature components of the data symbol. In this paper, because QSM-based on Interleaving Division Multiplexing (IDM) has not been introduced in the literature as a multiple antenna system, we introduced a novel scheme, called QSM system based on Interleaving Division Multiplexing (QSM-IDM). The antenna sets are also applied to a spreader, before being used to assign an antenna number for information transmission. Analysis and simulations for a flat fading channel show that the proposed QSM-IDM method significantly outperforms the original QSM system with the same data rate, while maintaining a relatively acceptable complexity. The obtained simulation results show that the conducted analysis yields significant improvements for the accuracy of the proposed scheme, with satisfactory complexity.