Zero-forcing Frequency-domain Equalization Research Articles

Simplified approach for symbol error rate analysis of SC-FDMA scheme over Rayleigh fading channel

In this paper, we present a comprehensive analytical study of the symbol error rate (SER) of single-carrier frequency-division multiple access (SC-FDMA) with zero-forcing frequency domain equalization (ZF-FDE) over a Rayleigh fading channel. SC-FDMA is considered as a potential waveform candidate for fifth-generation (5G) radio access networks (RANs). First, the NC fold convolution of the noise distribution of an orthogonal frequency-division multiplexing (OFDM) system is computed for each value of the signal-to-noise ratio (SNR) in order to determine the noise distribution of the SC-FDMA system. NC is the number of subcarriers assigned to a user or the size of the discrete Fourier transform (DFT) precoding. Here, we present a simple alternative method of calculating the SER by simplifying the NC fold convolution using time and amplitude scaling properties. The effects of the NC fold convolution and SNR over the computation of the SER of the SC-FDMA system has been separated out. As a result, the proposed approach only requires the computation of the NC fold convolution once, and it is used for different values of SNR to calculate the SER of SC-FDMA systems.

A Circulated Block Transmission Scheme for FTN Signaling

Fast-Than-Nyquist (FTN) transmission is a promising method to improve the spectrum efficiency for future wireless communication systems. However, this benefit of FTN is at the price of inducing the inter-symbol interference (ISI), which increases the complexity of the receiver. In this paper, a circulated block transmission scheme for FTN signaling, i.e. CB-FTN system is proposed. The detail implementation structure of CB-FTN transceiver is presented, in which the ISI caused by FTN transmission is canceled by the frequency-domain equalization (FDE), and the inter-block interference (IBI) caused by the multi-path channel is overcome by the cyclic-prefix. The postprocessing signal to noise ratio (pSNR) is analyzed for the CB-FTN receiver with zero-forcing FDE in AWGN channel, which is verified by the simulation results. Moreover, the BER performances and computational complexity of CB-FTN system are compared with the existed scheme.

Interference Mitigation in MC-CDMA System with CFO compensation based Modified MMSE-FDE Technique

carrier Code Division Multiple Access (MC-CDMA) has been an attractive technique for wireless communication because it offers high data rate, high spectral efficiency, large system capacity, less transmit power and less implementation complexity. But due to Carrier Frequency Offset (CFO), which comes into account due to asynchrony between transmitter and receiver local oscillators or by Doppler Effect due to high mobility, orthogonality among the subcarriers gets effected resulting in Inter Carrier Interference (ICI) which leads to rapid degradation in performance of MC-CDMA system. In this paper, the performance of Uplink MC-CDMA system with Zero forcing- frequency domain Equalization (ZF-FDE), conventional MMSE equalizer and Modified MMSE-FDE using Walsh-Hadamard spreading sequence in multipath fading channel has been analyzed. Simulation has been performed using 32 subcarriers and 64 subcarriers for these equalization techniques. Simulation results confirm excellent performance of the Modified MMSE-FDE which outperforms the conventional MMSE equalization and ZF- FDE. The further improvement in performance is achieved by employing 64 subcarriers instead of 32 subcarriers. Numerical equations and simulation results are given to support the analysis. Keywords-CDMA, CFO, MMSE-FDE, ZF, ICI, Walsh-Hadamard Sequence.

BER Analysis for Zero-Forcing SC-FDMA Over Nakagami-m Fading Channels

In this paper, we present an analytical study of the bit error rate (BER) for single-carrier frequency-division multiple access (SC-FDMA) transmission over frequency-selective fading channels when zero-forcing frequency-domain equalization is applied. SC-FDMA, which can be described as a precoded version of orthogonal frequency-division multiple access (OFDMA), is regarded as a promising candidate for next mobile communication systems due its favorable envelope characteristics and low peak-to-average-power ratio (PAPR), compared with that of OFDMA. We focus on Nakagami-m fading channels and provide a method to calculate BER values with a single numerical computation. We provide a closed-form expression for the BER with binary phase-shift keying (BPSK) and square M-ary quadrature amplitude modulation (M-QAM) under the assumption of independence among channel frequency responses for allocated subcarriers.