An MMSE-based beamforming algorithm for smart antenna applied to an MC-CDMA system with co-channel interference (original) (raw)
Related papers
2000
An alternative way of adaptive beamforming is presented in this paper. The main contribution of the new technique is in its simplicity with a minimal loss of accuracy. Total computational load for computing a suboptimal weight vector from each new signal vector is about (2 2 + 5 ). It can further be reduced down to (3 ) by approximating the autocorrelation matrix with the instantaneous signal vector at each snapshot. The required condition on the adaptive gain for the proposed algorithm to converge is derived analytically. The proposed beamforming algorithm is applied to the base station of a code-division-multiple access (CDMA) mobile communication system. The performance of the proposed method is shown in multipath fading communication channels in terms of the signal-to-interference + noise ratio (SINR), the bit error rate (BER), and the achievable capacity of a given CDMA cell/sector. Index Terms-Adaptive array system, code-division-multiple access (CDMA) mobile communications, Lagrange multiplier, maximum eigenvalue, time-space filtering.
Performance of adaptive beamforming algorithm for LMS-MCCDMA MIMO smart antennas
The International Arab Journal of Information Technology, 2009
We propose a downlink multiple-input multiple-output multi-carrier code division multiple access system with adaptive beamforming algorithm for smart antennas. The algorithm used in this paper is based on the least mean square, with pilot channel estimation and the zero forcing equalizer in the receiver, requiring reference signal and no knowledge channel. multi-carrier code division multiple access is studied in a multiple antenna context in order to efficiently exploit robustness against multipath effects and multiuser flexibility multi-carrier code division multiple access and channel diversity offered by multiple-input multiple-output systems for radio mobile channels. Computer simulations, considering multi-path Rayleigh Fading Channel, interference inter symbol and interference are presented to verify the performance.Simulation results demonstrate a significant performance improvement using our proposed receiver structure for a multiple-input multiple-output system with the presence of large Interferences. Therefore, the BER performance of the proposed system is much better than STBC-multi-carrier code division multiple access system with RMSE algorithm. In the other hand it can be seen that, as a number of antennas at transmitter and receiver increases, the performance also improves and the number of interferences decrease the performance of the system with the same Rayleigh fading environment.
International journal of computer applications, 2013
The main objective of the multi-antenna technology is improving the capacity of cellular systems. These techniques can also make other improvements such as the scope of the system, reducing the transmission power of mobile (and therefore increasing energy autonomy) and improved link performance. This was the context of this paper study whose objective was to study the contribution and providing of the use of adaptive antennas in multiuser detection for MC-CDMA system. Transmission implicated in the MC-CDMA system has potential interference rejection but not sufficiently in the case of strong interference. Therefore it need to use beamforming algorithms. This work is also interested in MIMO-MC-CDMA with multiple-beamforming (MBF) at the receiver, that uses multiple antennas at transmitter and receiver. This paper presents also the performance of general MIMO-MC-CDMA system used Multi-Beamformer with sequences of references at receiver and space time block code (STBC) or vertical bell labs space-time architecture (V-BLAST) at the transmitter, with minimum mean square error (MMSE) adaptive algorithm under Rayleigh fading channels.
Evaluation of Adaptive Beamforming Algorithm Of Smart Antenna
2013
The adoption beamformation of smart antenna techniques is increase the interference moderation future of wireless systems. It is expected to have a significant impact on the efficient use of the spectrum, the minimization of the cost of build new wireless networks, the optimisation of service quality, and realization of diaphanous operation across multi technology wireless networks. This paper presents the brief functioning account of LMS algorithm on smart antenna (SA) system in context of adaptive beamforming. The capabilities of smart / adaptive antenna are easily employable to Cognitive Radio and OFDMA system. Further, Implementation that resolves around the LMS adaptive algorithm, chosen for its reckoning restraint and high constancy into the MATLAB simulation of an adaptive array of a smart antenna base station system, is look into its performance in the presence of multipath components and multiple users.
Due to recent substantial development in the field of wireless communication, there is a need to maximize spectral efficiency so that the extensive increase in traffic can be accommodated efficiently. Smart antenna system is a major source to maximize spectral efficiency and capacity of the wireless networks. It consists of an adaptive antenna array that continuously adjusts its radiation characteristics (beam-width of main lobe, side lobe levels and position of nulls) to produce narrow beam in the direction of arrival (DOA) of desired signal and to place nulls in the DOA of interferer signals so that maximum SINR (Signal to Interference and Noise Ratio) is obtained. Smart antennas are becoming more popular now a days due to extensive advancement in the field of digital signal processing and real time implementation of adaptive signal processing techniques on FPGA’s. In this paper we analyze various adaptive beamforming algorithms including LMS (Least Mean Squares), CMA (Constant Modulus Algorithm), RLS (Recursive Least Squares) and CGM (Conjugate Gradient Method) through simulating different parameters like radiation pattern, amplitude response, mean square error and absolute weights of an N-element array for a certain number of iterations. The obtained simulation results are very helpful to evaluate performance and quality of adaptive beamforming algorithms.
Performance of Adaptive Beamforming Techniques in Smart Antenna
2012
The smart antenna is a new technology and has been applied to the mobile communication system such as GSM and CDMA. Advent of powerful, low-cost, digital processing components and the development of software-based techniques has made smart antenna systems a practical reality for both base station and mobile station of a cellular communications systems in the next generation. The core of smart antenna is the selection of smart algorithms in adaptive array. Using beam forming algorithms the weight of antenna arrays can be adjusted to form certain amount of adaptive beam to track corresponding users automatically and at the same time to minimize interference arising from other users by introducing nulls in their directions. Thus interferences can be suppressed and the desired signals can be extracted. This research work provides description, comparative analysis and utility of various reference signal based algorithms as well as blind adaptive algorithms. Exhaustive simulation study of...
A novel adaptive beamforming algorithm for antenna array CDMA systems with strong interferers
2002
Blind beamforming based on the maximum signal-to-noise ratio (MSNR) can improve the performance of the array system only when the processing gain of the given code-division multiple-access (CDMA) system is high enough such that the desired signal can become dominant after the despreading [3], [15]. In this paper, we consider a maximum signal-to-(interference plus noise) ratio (MSINR) beamforming. The MSINR performance criterion is chosen to effectively deal with strong interferers. It is shown in this paper that a blind MSINR beamforming is possible by directly utilizing input and output signals of correlators of the CDMA systems. In addition, we propose an adaptive beamforming algorithm at a lower computational complexity-about (7 5 )-where is the number of antenna elements of the array system. Simulation results are presented in various signal environments to show the performance of the proposed adaptive algorithm.
Performance analysis of adaptive beamforming algorithm for smart antenna system
2012 International Conference on Informatics, Electronics & Vision (ICIEV), 2012
Orthogonal Frequency Division Multiplexing (OFDM) is gaining popularity for high data rate communication systems. We propose the use of adaptive beamforming for interference rejection in OFDM systems, due to its advantages over equalization. An adaptive beamformer uses the concept of spatial filtering to direct the antenna beam towards the desired signal/transmitter and place a null towards the interfering signal. The Fast Fourier Transform (FFT) at the receiver end of an OFDM system enables the use of frequency domain beamforming to reduce narrow band interference individually across all the subcarriers. We implemented both decision directed and blind algorithms. Use of these algorithms reduced the Bit Error Rate (BER) to a great extent. The performance analysis for Least Mean Square (LMS) algorithm, Recursive Least Squares (RLS) and Constant Modulus Algorithm (CMA) for hundred OFDM symbols and five hundred and twelve subcarriers, four hundred and is provided.
Fast Adaptive Beamforming Algorithm for a Smart Antenna System in Mobile Communications
This paper proposes an adaptive beamforming algorithm for a smart antenna system in mobile communications. The proposed adaptive beamforming algorithm uses an adaptive variable step size Least Mean Square (LMS) algorithm for creating nulls towards the interferences and maximize the gain in the other direction. It is called Fast Variable Step Size LMS algorithm ( FVSSLMS). This new algorithm uses a large step size in the initial stage to speed up the convergence and gradually decrease it to a smaller one during the convergence. Computer simulation shows the performance of the proposed algorithm has obviously enhanced over that of LMS algorithm and other variable step size algorithm (VSSLMS) in terms of deep null in the direction of interference signals and fast convergence time.
Smart Antennas for Multiuser DS/CDMA Communications in Multipath Fading Channels
IEICE Transactions on Communications, 2005
Smart antennas, with spatial processing, used in code division multiple access (CDMA) multiuser communications can enhance range, reliability and capacity. Moreover, the adaptive beamforming technologies can remove unwanted noise and jamming from the received signal. In this paper, we use least mean square algorithm and propose four adaptive antenna receiver structures for directsequence (DS) CDMA multiuser environment with multipath fading channels. Narrowband and wideband adaptive array receiver structures are considered in this paper. LMS algorithms are employed in both narrowband and wideband receiver structures to adjust the spreading code coe cients. We call these new schemes as Wiener code filters. The weights of the adaptive beamformer and the spreading code are updated every bit interval, so the computational complexity is very low. Simulation examples are given to compare the performances of the proposed receiver structures.