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An unscented Kalman filter (UKF)-based channel-tracking method is proposed for a fast time-varying multipath fading channel in a multicarrier code-division multiple-access (MC-CDMA) system. The mobile radio channel is modeled as an autoregressive (AR) random process. The parameters of the AR process and the channel gain are simultaneously estimated...
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... in the system. The nth multicarrier block symbol (duration T ) for user j is formed by taking μ symbols d 1 j (n), . . . , d μ j (n) in parallel, which are spread by the user's spreading code c j with length N . Thus, the μ spread symbols are placed into N s = μN available subchannels. The block diagram of the MC-CDMA transmitter is shown in Fig. 1. In the rest of this paper, for simplicity of notation, we concentrate only on the case where each user transmits one symbol (μ = 1) in each MC-CDMA block symbol. The transmitted symbol is simply repre- sented as d j (n) for user j. Therefore, the total number of subchan- nels is N s = N . The Walsh-Hadamard spread code c j for user j ...
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... 978-1-5090-3239-6/17/$31.00©2017 IEEE In literature we find that Kalman filtering techniques using linear filters i.e., Kalman filter and non-linear i.e., EKF(Extended Kalman Filter) and UKF(Unscended Kalman Filter) have been proposed for channel equalization for Rayleigh Fading channel. Both Blind and Semi-Blind techniques are used for channel equalization and channel estimation for Rayleigh fading channel using different types of Kalman filters[10][11][12][13][14][15][16][17][18][19][20]. In this paper we have used semi-blind method of channel equalization using EKF(Extended Kalman Filter).OFDM (Orthogonal Frequency Division Multiplexing) is a type of frequency division multiplexing. ...
Channel Equalization in Telecommunication is the process of removal of any distortions that have incurred when any signal is transmitted through any channel. In this paper pilot based channel equalization using EKF(Extended Kalman Filter) for Rayleigh fading channel model is proposed. Using the pilot bits and the training sequences the channel state information is obtained, which is used to effectively equalize the signals transmitted. The Extended Kalman Filter used for equalization is bandwidth efficient and has low computational complexity. The results obtained by Extended Kalman Filter equalization and MMSE equalization are compared and it is found that the Extended Kalman Filter is computationally less complex and is efficient.
... This is the reason that symbol timing and carrier frequencies need to be acquired [10]- [12]. The estimates for multi-path gain are necessary because many demodulators collect energy from several paths [13]. The receiver design also needs the information of multi-path gain. ...
... This makes the UKF converge faster than the EKF when the channel variation cannot be modeled by a specific function. Some research efforts have been conducted to apply UKF in channel estimation [27]- [29], with the work in [27] and [28] that is directly related to CE in CDMA networks. Aside from that, the UKF can provide better control of the noise component. ...
... This makes the UKF converge faster than the EKF when the channel variation cannot be modeled by a specific function. Some research efforts have been conducted to apply UKF in channel estimation [27]- [29], with the work in [27] and [28] that is directly related to CE in CDMA networks. Aside from that, the UKF can provide better control of the noise component. ...
Future broadband wireless applications must effectively work under highly dynamic and strong multipath channel conditions, where severe time- and frequency-selective fading effects will coexist. Although some advanced techniques, such as 2-D block spread coding and antenna diversity techniques, can be applied to the code-division multiple-access (CDMA) networks to improve the performance, an accurate estimation of the channel is normally required. Conventional channel estimators (CE) such as the minimum-mean-square-error (MMSE)-based CE cannot effectively track the channel when the time-selective fading of the channel becomes severe. The performance will even be deteriorated in a multiuser environment, where multiple-access interference (MAI) exists. Therefore, in this paper, we demonstrate the challenges to CE in 2-D block spread coding networks through analytical derivation and then propose an unscented Kalman-filter (UKF)-based iterative CE for uplink transmission in multicarrier CDMA networks. By jointly working with the MMSE-CE, our proposed UKF-based approach can effectively track the dynamic changes in the time-selective fading channel and compensate for the estimation lag caused by the Doppler effects. Our scheme can also effectively mitigate the impact of the residual MAI, which resulted from the detection process. Simulation analysis demonstrates the good estimation performance and the quick convergence of the proposed MMSE-UKF CE, particularly under fast-varying channel conditions.
In wireless communication system field the main efforts have been directed towards the channel estimation. Since the transmitted dataare prone to the channel noise. The error controlled codes are used to minimize channel noise but these codes are bandwidth inefficient. In order to solve these problems several coded modulation schemes for different channel conditions were proposed in literature [1-4,19]. To match the channel conditions both coding and modulation are combined in coded modulation schemes. Superposition Coded Modulation (SCM) is one among theCoded modulation schemes [5-6]. The SCM systemis explained in detail in section II. In this paper we are proposing channel estimation technique for the SCM system. The efficient channel estimation techniques are essential for the equalizer to work efficiently.The channel state information is very crucial in the wireless communication system. In order to maximize the SNR at the receiver, several channel approximation algorithm was proposed for rapid convergence and for improving MSE performance[7]. The channel estimation using pilot sequences were proposed in both time and frequency domain in[8]. The decision direct channel estimation technique has been proposed in[9]which are based on Kalman filter. The technique mentioned in[9] has no overhead pilot symbols. But the decision direct method adopted in the[9] has delay problem. This leads to slow channel tracking in fast fading channel.
This paper investigates the channel estimation method for multiuser Multiple Input/Multiple Output (MIMO) multi-carrier code division multiple access (MC-CDMA) communication systems. For the asynchronous uplink transmission situation, the receiver needs to estimate the channel parameters, including the multi-path gain coefficient, the carrier phase offset and the transmission time delay, to demodulate the received signals. Based on the knowledge of the spreading sequences, the proposed parameter estimation method employs the Least Mean-Squared Error (LMSE) criterion in the required parameters for the multiuser MIMO MC-CDMA systems. The Quasi Mean Square Accuracy Coefficient (QMSAC) that allows the search for multiple parameters to be split into single parameter estimation is introduced. Some simulation examples for uplink scenario are given to demonstrate the effectiveness of the proposed methods.
An algorithm, based on frequency domain accumulation for the cyclic autocorrelation of MC-CDMA signals, is proposed to estimate the signal parameters: useful data duration, symbol duration, and chip duration in multipath fading channel. Firstly the cycle autocorrelation of received MC-CDMA signals is computed, then frequency domain accumulation is used to reduce the influence of noise. At last, through interval measurement between the peak pulses in different slices, parameters mentioned above can be estimated. Meanwhile, for the estimation of symbol duration, a novel accumulative average method is developed: by averaging amplitudes of the spectral lines in each column parallel to the time-delay axis in the three-dimensional diagram, the symbol duration can be obtained. The cyclic autocorrelation expression of MC-CDMA signal has been derived, and simulation results show that the proposed algorithm is effective and works well under the condition of low signal-to-noise ratio (SNR).
The quality of a wireless link can be described by three basic parameters, namely transmission rate, transmission range and transmission reliability. With the advent of multiple-input multiple-output (MIMO) assisted Multicarrier code division multiple access (MC-CDMA) systems, the above-mentioned three parameters may be simultaneously improved. The MC-CDMA combined with the MIMO technique, has become a core technology for future mobile radio communication system. However, possible potential gain in spectral efficiency is challenged by the receiver's ability to accurately detect the symbol due to inter symbol interference (ISI). Multipath propagation, mobility of transmitter, receiver and local scattering cause the signal to be spread in frequency, different arrival time and angle, which results in ISI in the received signal. This will affect overall system performance. The use of MC-CDMA mitigates the problem of time dispersion. However, still it is necessary to remove the amplitude and phase shift caused by channel. To solve this problem, a multiple antenna array can be used at the receiver, not only for spectral efficiency or gain enhancement, but also for interference suppression. This can be done by the, efficient channel estimation with strong equalization. This paper proposes MIMO MC-CDMA system, Minimum mean square error (MMSE) equalization with pilot based channel estimation. The simulation result shows improved Bit error rate (BER) performance when the sub carrier (SC) and antenna configuration were increased.
In this paper, we examine the channel estimation problem for one-way relay network(OWRN) under time-selective fading channel scenario. Our aim is to estimate the individual channels of each relay hop at the destination with unknown data from source. We utilize the relay's aided estimation function through superimposing pilots at relay, adopt the autoregressive (AR) model to characterize the time-varying individual channels, and construct the nonlinear dynamic state space for the individual channels. Furthermore, one low-complex data-decision directed UKF is designed to implement online time-varying individual channel tracking. Finally, simulation results will be provided to corroborate our proposed studies.
Now a days mobile cellular communication is becoming basic need in day to day life. At the same time security issues and errors in data communication are also increasing. So it is very essential to choose coding techniques to improve the Bit Error Rate and at the same time providing security in 4G technology by performing various simulations. The main aim of the paper is to develop better codes to provide the best BER Performance under the mentioned conditions by performing various simulations. In this paper MC-CDMA is proposed to mitigate the effect of frequency selective fading channel, while power control is proposed to combat Rayleigh fading channel fluctuation. The performance of MC-CDM is to be evaluated using best codes in Additive White Gaussian Noise (AWGN) and Rayleigh fading channel. Computer simulation is to be conducted to evaluate the performance of MC-CDMA as well as control the bit error rate (BER) as a function of bit energy to noise density ratio (Eb/No). The investigation of multi user Demodulation scheme and realization of fully functional system is to be done for developing an algorithm for the detection of multi-users in CDMA system by using a noisy gradient approach.
