RAKE Receiver

U radu je dan teorijski opis CDMA sustava i njegovih osnovnih načela rada. Uz tehniku raspršenog spektra, opisana je i kontrola snage te ortogonalni kodovi. Objašnjen je dizajn RAKE prijemnika, njegova funkcija i način rada. Na temelju simulacije napravljena je analiza utjecaja parametara prijemnika na kvalitetu detektiranog signala u različitim propagacijskim scenarijima.The paper presents a theoretical description of the CDMA system and it's basic principles of operation. The spread spectrum technique is described along with power control and orthogonal codes. The design of RAKE receiver is explained as it's function and operation technique. Analysis of influence of different parameters of receiver on the quality of detected signal in different propagation scenarios is made on the base of simulation

A Robust Adaptive MMSE Rake Receiver for DS-CDMA System in a Fast Multipath Fading Channel

In this paper, we propose a robust adaptive minimum mean square error (MMSE) Rake receiver for asynchronous DS-CDMA systems. The receiver uses the modified MMSE criterion that incorporates the differential detection and the amplitude compensation for interference cancellation in a time-varying multipath fading channel. We investigate that the proposed Rake receiver can achieve the higher output signal to interference plus noise ratio (SINR) than the conventional adaptive Rake receiver, since the modified MMSE criterion does not attempt to track the time-varying MMSE solution. Computer simulations verify that the performance of the proposed Rake receiver is better than those of the conventional and the adaptive Rake receiver

Chip equalized adaptive rake receiver for DS-CDMA UWB systems

Conventional Rake receiver is a popular and effective method of utilizing the diversity offered by a DS-CDMA and multipath communication channel. The proposed Rake receiver is useful for suppression of multiple access interference in a multipath channel. The receiver works on chip level equalization on each Rake finger to cancel multi-access interference. Simulation results show that the convergence, diversity gain and bit error probability performance of the proposed receiver is much better than conventional adaptive Rake receiver in multipath channels

A NEW PARALLEL INTERFERENCE CANCELLATION ALGORITHM FOR RAKE SYSTEMS

In order to suppres the multi-path interference (MPI) in the DS CDMA system, a new RAKE receiver based on parallel interference elimination is first proposed in this paper data symbol tentative decision is obtained by linear decision; the multi-path interference are evaluated by tentative decision and known user information. Then the performance over Rayleigh fading channel are analyzed and compared to conventional parallel interference cancellation (PIC) and RAKE receiver. It is shown that RAKE receiver performance can be improved greatly by using this method with simple structure and easy implementation

Interference Suppression in WCDMA with Adaptive Thresholding based Decision Feedback Equaliser

WCDMA is considered as one of the 3G wireless standards by 3GPP. Capacity calculation shows that WCDMA systems have more capacity compared to any other multiple access technique such as time division multiple access (TDMA) or frequency division multiple access (FDMA). So it is widely used. Rake receivers are used for the detection of transmitted data in case of WCDMA communication systems due to its resistance to multipath fading. But rake receiver treat multiuser interference (MUI) as AWGN and have limitation in overcoming the effect of multiple access interference (MAI) when the SNR is high. A de-correlating matched filter has been used in this thesis, which eliminates and improves system performance. But the given receiver works well only in the noise free environment. A DFE, compared to linear equaliser, gives better performance at severe ISI condition. The only problem in this equalisation technique is to select the number of symbols that are to be fed back. This thesis gives an idea on multiple symbol selection, based on sparity where an adaptive thresholding algorithm is used that computes the number of symbols to feedback. Simulated results show a significant performance improvement for Regularised Rake receiver along with thresholding in terms of BER compared to a rake receiver, de-correlating rake receiver and regularised rake receiver. The performance of the receiver in different channels is also analysed

Performance Evaluation of Adaptive Continuous Wavelet Transform based Rake Receiver for UWB Systems

This paper proposes an adaptive continuous wavelet transform (ACWT) based Rake receiver to mitigate interference for high speed ultra wideband (UWB) transmission. The major parts of the receiver are least mean square (LMS) adaptive equalizer and N-selective maximum ratio combiner (MRC). The main advantage of using continuous wavelet rake receiver is that it utilizes the maximum bandwidth (7.5GHz) of the UWB transmitted signal, as announced by the Federal Communication Commission (FCC). In the proposed ACWT Rake receiver, the weights and the finger positions are updated depending upon the convergence error over a period in which training data is transmitted. Line of sight (LOS) channel model (CM1 from 0 to 4 meters) and the Non line of sight (NLOS) channel models (CM, CM3 and CM4) are the indoor channel models selected for investigating in this research . The performance of the proposed adaptive system   is evaluated by comparing with conventional rake and continuous wavelet transform (CWT) based rake. It showed an improved performance in all the different UWB channels (CM1 to CM4) for rake fingers of 2, 4 and 8. Simulations showed that for 8 rake fingers, the proposed adaptive CWT rake receiver has shown an SNR improvement of 2dB, 3dB, 10dB and 2dB respectively over CWT rake receiver in different UWB channels CM1, CM2, CM3 and CM4

A RAKE Receiver Employing Maximal Ratio Combining (MRC) Without Channel Estimation for UWB Communications

An alternative method to channel estimation is presented as a means of supplying a RAKE receiver with the coefficients for Maximal Ratio Combining (MRC). The proposed RAKE receiver utilizes Time-Hopping Pulse Position Modulation (TH-PPM), and is specifically designed to be used in Ultra Wideband (UWB) communication systems in which channel estimation becomes problematic because of the high sampling rate required. The MRC coefficients are determined by a simple process of averaging the received energy for a given correlator finger over the course of a pilot sequence of P pulses. Performance of the proposed RAKE receiver is investigated through simulation using a discrete-time implementation of the multi-path channel model published by the IEEE 802.15.3 task group. The proposed RAKE receiver’s Bit-Error-Rate (BER) performance is compared against other RAKE receivers relying on channel estimation

A New Combination of RAKE Receiver and Adaptive Antenna Array Beamformer for Multiuser Detection in WCDMA Systems

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 blind beamforming algorithms. It is based on constrained constant modulus (CCM) algorithm which is used for deriving a recursive-least-squares (RLS-) type optimization algorithm. We illustrate the comparison of bit error rate (BER) of the proposed receiver with simple correlator and also 1D-RAKE receiver in multiuser detection (MUD) WCDMA. The simulation results show that the proposed 2D-RAKE receiver offers lower BER rather than conventional ones, that is, it is an effective solution for decreasing the effect of interference and increasing the capacity, in a joint state

RAKE receiver for the UMTS system

Tato práce se zabývá teoretickým popisem dějů probíhajících v systému UMTS při práci se signálem, jeho rozprostřením za použití modulační techniky DS SS(direct sequence spread spectrum) a následným zpracováním signálů v RAKE přijímači. Popisem jeho základních funkcí: přizpůsobeným filtrováním, deskramblováním, derozprostřením a integrací. Navíc je práce doplněna o výsledky simulace přijímače pro nízký počet vzorků v programu MATLAB, dále vytvoření aplikace simulující RAKE přijímač a její výsledky.This thesis is focused on theoretical description of procedures which take place in the UMTS system when processing a signal, its spreading with modulation technique DS SS(direct sequence spread spectrum), and subsequent processing in the RAKE receiver. Another focus is made in the basic functions of a RAKE receiver: match filtering, descrambling, despreading and integration. Aditionally, this thesis is suplemented with the results of a RAKE receiver simulation for a small number of samples in the MATLAB software and creation of aplication that simulates the receiver and its results.