Root Raised Cosine Pulse Shaping Research Articles

Generalized frequency division multiplexing system performance with companding transform and pulse shaping filter

Generalized Frequency Division Multiplexing (GFDM) is considered as new candidates for futuristic multicarrier modulation technique. But GFDM suffers from high Peak to Average Power Ratio (PAPR) that leads to severe degradation in Bit Error Rate (BER) performance. In present work, Piecewise Nonlinear Companding Transform (PNCT) along with root raised square pulse shaping performance is analyzed to suppress high PAPR in GFDM system and to improve the BER performance. The pulse shaping filters have significant impact on the PAPR performance in GFDM system. By properly considering the rolloff factor in root raised cosine filter with companding transform can effectively handle the high PAPR of GFDM. The simulation results show that root raised cosine pulse shaping along with companding transform significantly achieves the better BER performance and can avoid distortion that occurs in the nonlinear amplifiers of the transmitter leads to reduced PAPR.

A Very Low Complexity Successive Symbol-by-Symbol Sequence Estimator for Faster-Than-Nyquist Signaling

In this paper, we investigate the sequence estimation problem of binary and quadrature phase shift keying faster-than-Nyquist (FTN) signaling and propose two novel low-complexity sequence estimation techniques based on concepts of successive interference cancellation. To the best of our knowledge, this is the first approach in the literature to detect FTN signaling on a symbol-by-symbol basis. In particular, based on the structure of the self-interference inherited in FTN signaling, we first find the operating region boundary defined by the root-raised cosine pulse shape, its roll-off factor, and the time acceleration parameter of the FTN signaling where perfect estimation of the transmit data symbols on a symbol-by-symbol basis is guaranteed, assuming noise-free transmission. For noisy transmission, we then propose a novel low-complexity technique that works within the operating region and is capable of estimating the transmit data symbols on a symbol-by-symbol basis. To reduce the error propagation of the proposed successive symbol-by-symbol sequence estimator (SSSSE), we propose a successive symbol-by-symbol with go-back- $K$ sequence estimator (SSSgb $K$ SE) that goes back to re-estimate up to $K$ symbols, and subsequently improves the estimation accuracy of the current data symbol. Simulation results show that the proposed sequence estimation techniques perform well for low intersymbol interference scenarios and can significantly increase the data rate and spectral efficiency. Additionally, results reveal that choosing the value of $K$ as low as 2 or 3 data symbols is sufficient to significantly improve the bit-error-rate performance. Results also show that the performance of the proposed SSSgb $K$ SE, with $K = 1$ or 2, surpasses the performance of the lowest complexity equalizers reported in the literature, with reduced computational complexity.

Polynomial Pulses for Mitigating Fiber Nonlinearity in Coherent Optical Fiber Communications

Root polynomial (RP) pulses are considered for mitigating fiber nonlinearity for 128 Gb/s dual-polarization 8-ary quadrature-amplitude-modulation dense wavelength division multiplexed (DWDM) systems. RP pulses exhibit a fast asymptotic decay rate, low peak-to-average power ratio, and narrow pulse width. Consequently, they are tolerant toward intrachannel nonlinearity, digital-to-analog converter quantization effects, and timing recovery errors. In a nine-channel DWDM transmission experiment with a 25 GHz channel spacing and null-to-null modulated optical signal bandwidth of 25 GHz, the RP pulse shape yields a maximum distance of 4800 km, which extends the transmission distance by 300 km (length of the recirculating loop) relative to the root raised cosine pulse shape.

A Novel Zadoff-Chu Matrix Transform Precoded Interleaved-OFDMA Uplink System for 4G Cellular Systems: Peak to Average Power Ratio Performance

High Peak to Average Power Ratio (PAPR) is one of the major drawbacks in the Orthogonal Frequency Division Multiple Access (OFDMA) systems. In this paper, we present a novel Zadoff-Chu Matrix Transform (ZCMT) precoding based Interleaved-OFDMA uplink system with improved PAPR for the upcoming 4G cellular systems. The proposed system is based on the precoding of constellation symbols with ZCMT precoder in such a way that the system becomes Constant Envelope OFDMA (CE-OFDMA). The CE-OFDMA signal allows the Radio-Frequency (RF) high power amplifier to operate near its saturation levels, thus maximize the power efficiency. However, even 0 db PAPR or CE-OFDMA systems must contend with pulse shaping to keep out of band radiation low and to meet the transmission spectrum mask requirement. Hence, the PAPR is analyzed with Root Raised Cosine pulse shaping. Simulation results show that proposed system has better PAPR gain than the walsh-hadamard transform (WHT) precoded Interleaved-OFDMA uplink systems and the conventional Interleaved-OFDMA uplink systems.

A multicarrier QAM modulator for WCDMA base-station with on-chip D/A converter

In this paper, design and implementation of a multicarrier quadrature amplitude modulation (QAM) modulator for a wideband code division multiple access (WCDMA) base-station with a 14-bit on-chip D/A converter is described. The modulator is capable of modulating four carriers with four independent in phase (I) and quadrature (Q) data streams. The proposed modulator structure consists of an interpolation chain for data streams and four digital frequency synthesizer/modulators, which are based on a coordinate rotation digital computer (CORDIC) vector rotation algorithm. The interpolation chain consists of a root-raised cosine pulse shaping filter and three half-band filters for image filtering. The modulated carriers are combined to form a multicarrier WCDMA signal. The SINC-attenuation effect of a digital/analog (D/A) converter is canceled by an inverse-SINC predistortion filter. The multicarrier signal is converted to the analog domain with a 14-bit current steering D/A converter, which is integrated on the same silicon chip. The modulator is implemented with a 0.35-mum BiCMOS process with CMOS transistors only

Spread-time CDMA resistance in fading channels

We study and examine the effect of fading channels on the performance of spread-time/code division multiple access (ST/CDMA). We consider two different models for fading channel and obtain the average signal to interference plus noise ratio (SIR) for ST/CDMA in both cases. We also obtain the SIR for spread-spectrum/CDMA (SS/CDMA) and compare the results with that of ST/CDMA. Depending upon the transmitted chip pulse shape, and in the absence of thermal noise, spread-time (ST) performance is equal to or greater than spread spectrum (SS). For example ST/CDMA has 0.62 dB higher SIR value compared to SS/CDMA with root raised cosine pulse shape with rolloff factor 0.22 used in W-CDMA. The spread-time technique was first proposed by Crespo et al. (1991, 1995), and US Patents no. 5177768, 5175744, 5175743, 5173923, and is considered as the time-frequency dual of spread spectrum technique.

Subchip multipath delay estimation for downlink WCDMA system based on Teager-Kaiser operator

Accurate detection and estimation of overlapping fading multipath components is vital for many communication systems, particularly for positioning technologies. Traditional approaches used for channel estimation generally fail in estimating closely-spaced multipath components in code-division multiple access (CDMA) systems. Here, we present a highly efficient technique for asynchronous downlink WCDMA multipath delay estimation with subchip resolution capability based on nonlinear Teager-Kaiser operator concept. The behavior of this technique is influenced considerably by the pulse shape waveform. Both rectangular and root raised cosine pulse shaping filters are considered.