Classical Constant Modulus Algorithm Research Articles

Blind Fuzzy Adaptation Step Control for a Concurrent Neural Network Equalizer

Mobile communications, not infrequently, are disrupted by multipath propagation in the wireless channel. In this context, this paper proposes a new blind concurrent equalization approach that combines a Phase Transmittance Radial Basis Function Neural Network (PTRBFNN) and the classic Constant Modulus Algorithm (CMA) in a concurrent architecture, with a Fuzzy Controller (FC) responsible for adapting the PTRBFNN and CMA step sizes. Differently from the Neural Network (NN) based equalizers present in literature, the proposed Fuzzy Controller Concurrent Neural Network Equalizer (FC-CNNE) is a completely self-taught concurrent architecture that does not need any training. The Fuzzy Controller inputs are based on the estimated mean squared error of the equalization process and on its variation in time. The proposed solution has been evaluated over standard multipath VHF/UHF channels defined by the International Telecommunication Union. Results show that the FC-CNNE is able to achieve lower residual steady-state MSE value and/or faster convergence rate and consequently lower Bit Error Rate (BER) when compared to Constant Modulus Algorithm-Phase Transmittance Radial Basis Function Neural Network (CMA-PTRBFNN) equalizer.

Efficient Blind Beamforming Algorithms for Phased Array and MIMO RADAR

In this paper, we devised two new adaptive blind beamformers based on well-known constant modulus algorithm (CMA) and least square CMA (LS-CMA). First, we improved the convergence rate of CMA and then applied Hanning window to both CMA and LS-CMA to reduce side-lobe level (SLL). These new algorithms are Hanning window CMA (HW-CMA) and Hanning window LS-CMA (HW-LS-CMA),- Simulation results show the significant improvement in the convergence rate and drastic reduction in the SLL. The proposed HW-CMA converges within less than 10 iterations and the SLLs of both algorithms are reduced below −44 dB with the improvement of 33 dB as compared to classical CMA. Hence the proposed beamformers can be used in advanced communication applications.

Robust Blind Beam Formers for Smart Antenna System Using Window Techniques

In this paper, we devised three efficient adaptive blind beamformers for smart antenna system based on popular constant modulus algorithm (CMA). Slow convergence rate of classical CMA limits its utilization in wireless communication applications where the channel conditions are rapidly changing. To overcome this problem, we firstly improved the convergence rate of CMA by making a step size adaptive. This makes CMA to converge within 10 iterations. Furthermore, to reduce the side lobe level (SLL), we applied three different windows namely; hanning, hamming and kaiser to the improved CMA and these algorithms are called as H-CMA, HW-CMA and KW-CMA respectively. Simulated results show that, KW-CMA has highest reduction in SLL as compared to H-CMA and HW-CMA. It has -80dB peak SLL with an improvement of 70.89dB for ten antenna elements than the conventional CMA for the same conditions. Hence the proposed algorithms exhibit fast convergence rate and reduced SLL. These key features make the smart antenna system robust and efficient and can be used in advanced wireless communication applications like radar, sonar and mobile communications.

Blind equalization for minimum-shift keying coherent optical communication system

Abstract. The blind equalization of minimum-shift keying (MSK) in coherent optical communication is investi-gated. After the classical constant modulus algorithm (CMA) equalization step, the output of the equalizer doesnot necessarily coincide with a delayed androtated version of the input MSK signal. In our MSK coherent opticalsystem, a blind equalization criterion is proposed to eliminate the latter indeterminacy. Simulation results showthat the 10-Gb∕s MSK system successfully recovers MSK signal from various transmission impairments. © 2014Society of Photo-Optical Instrumentation Engineers (SPIE) [DOI: 10.1117/1.OE.53.4.046107] Keywords: blind equalization; minimum-shift keying; optical coherent system; constant modulus algorithm.Paper 140025 received Jan. 7, 2014; revised manuscript received Feb. 25, 2014; accepted for publication Mar. 12, 2014; publishedonline Apr. 29, 2014. 1 IntroductionRecently,minimum-shiftkeying(MSK)haspaidmoreatten-tion in the optical communication, owing to its constantamplitude and a continuous phase at every bit transitioninstant and a narrow power spectrum.

Antenna polarization diversity for high-speed polarization multiplexing wireless signal delivery at W-band

We propose and experimentally demonstrate a novel architecture for a W-band integrated optical wireless system, which adopts a 2×2 multiple-input multiple-output (MIMO) wireless link based on antenna polarization diversity, and can realize 80 km single-mode fiber-28 transmission and 2 m wireless delivery for up to 39 Gbaud polarization-division-multiplexing quadrature-phase-shift-keying (PDM-QPSK) signal at 100 GHz. Classic constant-modulus-algorithm (CMA) equalization is adopted at the receiver to implement polarization demultiplexing. The 2×2 MIMO wireless link adopts one pair of horizontal-polarization (H-polarization) horn antennas (HAs) and one pair of vertical-polarization (V-polarization) HAs. Because the two pairs of HAs are fully isolated, the wireless cross talk can be effectively avoided. Thus, compared to the 2×2 MIMO wireless link at the same antenna polarization, the adoption of antenna polarization diversity cannot only make the HA adjustment easier but can also reduce the required CMA tap number. After removing 20% forward-error-correction overhead, the 39 Gbaud baud rate corresponds to a net bit rate of 130 Gb/s, which, to our best knowledge, is the highest bit rate per PDM channel demonstrated for wireless signal delivery up to now.

Optical-wireless-optical full link for polarization multiplexing quadrature amplitude/phase modulation signal transmission

We propose and experimentally demonstrate an optical wireless integration system at the Q-band, in which up to 40 Gb/s polarization multiplexing multilevel quadrature amplitude/phase modulation (PM-QAM) signal can be first transmitted over 20 km single-mode fiber-28 (SMF-28), then delivered over a 2 m 2 × 2 multiple-input multiple-output wireless link, and finally transmitted over another 20 km SMF-28. The PM-QAM modulated wireless millimeter-wave (mm-wave) signal at 40 GHz is generated based on the remote heterodyning technique, and demodulated by the radio-frequency transparent photonic technique based on homodyne coherent detection and baseband digital signal processing. The classic constant modulus algorithm equalization is used at the receiver to realize polarization demultiplexing of the PM-QAM signal. For the first time, to the best of our knowledge, we realize the conversion of the PM-QAM modulated wireless mm-wave signal to the optical signal as well as 20 km fiber transmission of the converted optical signal.

Faster than fiber: over 100-Gb/s signal delivery in fiber wireless integration system

We summarize several different approaches for the realization of large capacity (>100Gb/s) fiber wireless integration system, including optical polarization-division-multiplexing (PDM) combined with multiple-input multiple-output (MIMO) reception, advanced multi-level modulation, optical multi-carrier modulation, electrical multi-carrier modulation, antenna polarization multiplexing and multi-band multiplexing. These approaches can effectively reduce the signal baud rate as well as the required bandwidth for optical and electrical devices. We also investigate the problems, such as wireless multi-path effect due to different wireless transmission distance, existing in the large capacity fiber wireless integration system. We demonstrate these problems can be effectively solved based on advanced digital-signal-processing (DSP) algorithms including classic constant modulus algorithm (CMA). Moreover, based on the combination of these approaches as well as advanced DSP algorithms, we have successfully demonstrated a 400G fiber wireless integration system, which creates a capacity record of wireless delivery and ushers in a new era of ultra-high bit rate (>400Gb/s) optical wireless integration communications at mm-wave frequencies.

Baud-spaced constant modulus blind equalization via hybrid genetic algorithm and generalized pattern search optimization

The present paper deals with the formulation of the baud-spaced constant modulus blind equalization in the presence of Gaussian noise as an unconstrained optimization problem via the use of genetic algorithm and generalized pattern search (GPS) algorithm. Simulation results show that the proposed approach is more robust to the adopted initialization strategy and much more likely to outperform the classical constant modulus algorithm in terms of minimum-squared error, intersymbol interference and error vector magnitude quantities.

A novel blind adaptive space-time receiver for multi-code DS-CDMA

Abstract-The capacity of conventional wireless communications systems based upon Direct-Sequence Code Division Multiple Access (DS-CDMA) schemes, is mainly limited by Multiple Access Interference (MAI). Therefore, methods aimed at reducing MAI are mandatory solutions to increase the capacity of such systems. Smart Antennas are a promising technology for improving the performance of high capacity mobile communications systems, because they are expected to be able to increase the Signal to Interference plus Noise power Ratio (SINR) of the received signals by dynamically adapting the equivalent array beam pattern in order to track the movements of the users within the cell. In this paper we propose a novel blind adaptive beamforming algorithm tailored for the up-link of multi-code multi-rate DS-CDMA wireless communications systems. Our proposal is based upon a modified Constant Modulus (CM) criterion, whose fundamental feature is the capability to overcome the main drawback of the classic CM algorithm, which lies in its difficulty of ensuring the convergence toward the desired user. The proposed algorithm exploits user-specific information intrinsically known at the receiver, which is the code uniquely associated to each user, without requiring the knowledge of the spatiotemporal propagation channel nor any specific training sequence. Within this paper we present a broadband solution, designed to temporally re-align uncorrelated clusters of multipaths, as well as spatially recombine correlated multipaths belonging to the same cluster. Computer simulations show that our proposed technique can effectively exploit path diversity and multipath correlation, also in the presence of Doppler effect and time-variable propagation conditions.