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![1D-RAKE receiver [3].](publication/258378575/figure/fig10/AS:329950004563980@1455677619987/1D-RAKE-receiver-3_Q320.jpg)
The aim of this paper is to combine smart antenna beamforming and RAKE receiver in wideband code division multiple access (WCDMA). The proposed method combines spatial diversity as well as temporal diversity to improve the performance and overcome both interferences and multipath fading. This investigation has focused on one of the new proposed bli...
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... Пространственно-временной алгоритм с решетчатым кодированием был предложен в [4]. Простая схема пространственно-временной обработки кодированных сигналов была предложена в [5] и рассматривается как один из стандартов для мобильной связи пятого поколения [6][7][8][9][10]. ...
In this paper, two different receiver structures to multiuser detection that are appropriate for the code-division multiple-access systems with antenna arrays in fading channels are investigated and compared. We analyze and compare the performance of the two different multiuser detection structures for uplink or downlink channels. The number of elements of receiving antenna array may be limited in the downlink channel due to the small size of receivers. We assume a synchronous system, but it can be easily extended to an asynchronous system. The first approach is based on the distributed decorrelator where the signal decorrelation is performed by each receiving antenna element independently and decorrelated outputs are combined according to the maximum ratio. The second approach is the central decorrelator where the signal decorrelation is performed once collectively on the outputs from all elements of receiving antenna array. Both decorrelators provide the same performance in the additive white Gaussian noise channels. The distributed decorrelator provides the better performance in flat fading channels. We employ the decorrelator to demonstrate our results. The results discussed in the present paper can be extended to other configurations such as the blind adaptive space-time multiuser detection.
... The adaptive beamformer extracts the wanted signal by directing the main beam towards the Angle of Arrival (AOA) of the user and the nulls towards the directions of other active users. The researchers published in these years a new receiver to resolve both the co-channel interference and the multipath of the signal involved in the channel ( [3], [4], [5], [6], [7], [8], and [9]). In this research, we are testing one of the best combinations of a RAKE receiver with an adaptive antenna array adopted by the Sub Block NLMS-DRMTA algorithm that proposed in [5], then compared its performance with Sample base NLMS-DRMTA algorithm that proposed in [10] and with the conventional CDMA. ...
... The performance has been tested regarding bit error rate in the presence of multipath environment, interference, and noise. In this combination, the size of users can override the size of antenna array beamformer without high decreasing to the performance [8]. ...
This paper presents a new amalgamation of the RAKE receiver with three-fingers, and the Sub-Block-Based Normalized Least Mean Square-Despread-Respread Multi-Target Array (NLMS-DRMTA) algorithm for multiuser detection in Wideband Code Division Multiple Access (WCDMA) systems. The new method uses together temporal diversity and the space diversity, for getting a significant enhancement in Bit Error Rate (BER) performance, As well as reducing unwanted signals and Indirect signals effects. The combination of the rake receiver and the Sub-Block-Based algorithm was compared versus the single antenna CDMA and sample-based NLMS-DRMTA algorithm. This method can equip users more than the number of antenna array elements. Consequently, it is an extra productive strategy for expanding channel limit. Thus, it opens the route to an answer for limiting the impacts of multipath effects and interference from other users, in this manner enhancing the quality of services. Simulation results show that the sub-block algorithm overcomes the others without a rake system in both environments (AWGN or/and multipath fading). But with the rake, this algorithm will suffer from degradation in its BER performance. Also, the sample base algorithm takes advantages performance in the presence of rake receiver.
... On the other hand, increasing synchronization mismatch between multipath delays and RAKE finger estimated delays degrades BER performance. Some of the previous research efforts in the area of adaptive beamforming algorithms did not utilize the knowledge of PN sequences in CDMA communications (Shirvani-Moghaddam and Sadeghi, 2011;Azubogu et al, 2012). On the other hand, this knowledge is explicitly exploited by CDMA specific adaptive algorithms that utilize the spatial separation among users through knowledge of their PN sequences by steering the main beam in the direction of the desired user and nulling in the directions of interferers (Connor, 2005). ...
... (1) where is the m-thuser received signal, M is the number of active users sharing the channel, and is the AWGN. can be expressed as(Shirvani-Moghaddam andSadeghi, 2011) ...
... The main objective of this research effort was to improve the BER of adaptive base-station antenna beamforming receiver in the uplink transmission for WCDMA systems in Multi-User Applications (MUAs). Adaptive beamforming algorithms adopted in previous research efforts in combined beamformer-RAKE receivers do not utilize the orthogonality of PN sequences in WCDMA communications((ShirvaniMoghaddam and Sadeghi, 2011;Azuboguet al, 2012). On the other hand, this orthogonality is explicitly utilized by adaptive beamforming algorithms based on DRMTA adaptive algorithms(Connor, 2005;Rong, 1996;Ronget al, 1997). ...
In this paper, we present a novel combination of the three-finger RAKE receiver and the Normalized Least Mean Square-Despread Respread Multi Target Array (NLMS-DRMTA) beamforming algorithm for applications in multiuser detection in wideband Code Division Multiple Access (CDMA) systems. The proposed approach utilizes both temporal diversity of the RAKE receiver and the space diversity of smart antenna array, leading to a significant improvement in Bit Error Rate (BER) performance, as well as a reduction interferences and multipath effects. The BER of the proposed receiver was benchmarked against the conventional CDMA, the Block-Based (BB) Least Squares (LS-DRMTA) and BB Least Squares-Despread Respread Multi Target Constant Modulus Array (LS-DRMTCMA) receivers. Both the RAKE and non-RAKE cases were considered for the CDMA and the two block-based beamformer receivers. The BER results confirm that the proposed receiver outperforms all other methods considered in this paper by two orders of magnitude. In addition, our approach can handle cases in which the number of users exceeds that of the antenna array elements without sacrificing performance. Hence, it is a more efficient method for increasing channel capacity. Consequently, it opens the way for a more efficient solution for minimizing the effects of multipath fading and interference in multiuser detection, thereby improving the quality of services.
... Recently, Shirvani and Sadeghi [25] proposed a new combination of CCM-RLS and RAKE receiver in multi user detection (MUD) wideband CDMA systems. In this paper, the performance of four receivers, correlator, 1D-RAKE, correlator + CCM-RLS beamforming, and 2D-RAKE with CCM-RLS beamforming is evaluated in terms of bit error rate (BER) for different signal to noise ratios (SNRs), modulation sizes and the number of array elements. ...
The main purpose of this article is to evaluate and to compare the performance metrics, array factor (AF),
signal to interference plus noise ratio (SINR), mean square error (MSE), bit error rate (BER), and also computational complexity of different modified blind adaptive beamforming algorithms based on constrained constant modulus (CCM). Two modified algorithms use adaptive step size mechanisms
in the stochastic gradient (SG) algorithm for adjusting the step size. The third one, CCM-RLS, uses recursive least squares (RLS) optimization algorithm which is replaced by the inverse correlation matrix instead of the step size. In the case of a uniform linear array (ULA) and 5 users, one as desired signal and the others as interference signals, simulation results show that the modified algorithms, CCM-
RLS, CCM-SG-time averaging adaptive step size (TAASS) and CCM-SG-modified adaptive
step size (MASS), offer higher performance with respect to conventional CCM-SG, respectively. Comparing the performance of CCM-RLS and adaptive step size versions of CCM-SG show that CCM-RLS
converges faster and it can cancel the interferences close to the desired signal, more effectively. Moreover, the resulting SINR level is higher and BER is less than the other methods. However, CCM-SG-MASS and CCM-SG-TAASS have less computational complexity, additions and multiplications.
Since ultra wideband (UWB) communication systems operate with short pulses and high data rates, the effect of noises and channel fading appeared upon receipt. The rake receiver scheme is used to collect the copies of the time-shifted original signal to make multi-path signals that are separately correlated by correlators. In line of sight (LOS) and non-line of sight (NLOS) propagation indoor environments and according to channel models proposed by IEEE 802.15.4a, M-max adaptive rake receiver (ARR) was proposed with three rake receiver-combining techniques, i.e., maximal ratio combining (MRC), equal gain combining (EGC), and selective combining (SC) that were simulated to capture the fingers output signal energy with perfect channel estimation. A matched filter for the UWB impulse radio was connected to maximize the desired signal over the noises. To minimize the mean squared error (MSE), an adaptive filter using a M-max partial update recursive least squares (RLS) algorithm was used to update the coefficients (tap weights) of the combiner at the decay states to keep the signal-to-noise ratio (SNR) at its optimal values. The proposed rake receiver had the good performance under the RLS proper parameters for the four channel models and three combining techniques. The MRC technique plays a more significant role in reducing the bit error rate (BER).
