Conventional Cyclic Prefix OFDM Research Articles

PAPR reduction in CP-OFDM (5G) using hybrid technique

The Cyclic Prefix Orthogonal Frequency Division Multiplexing (CP-OFDM) is a 5G multicarrier waveform that offers great data speeds and improvements in spectrum utilisation. The primary CP-OFDM’s weakness is its excessive peak-to-average power ratio (PAPR), which is a characteristic of all multicarrier modulation techniques. We study the application of a hybrid technique approach how to lower the peak to average power ratio (PAPR) in a CP-OFDM system. We also evaluated the outcomes of peak to average power ratio (PAPR) decrease in CP-OFDM, utilising a hybrid technique with Group Codeword Shift (GCS), Median Codeword Shift, Selective Codeword Shift (SCS), and Conventional CP-OFDM. When compared to the non-hybrid technique, the simulation results indicate that the hybrid approach is superior in reducing the peak PAPR by more than 65 percent.

PAPR Reduction in Cyclic Prefix OFDM (5G) System using Group Codeword Shifting Technique

Cyclic Prefix Orthogonal Frequency Division Multiplexing (CPOFDM) is a 5G multicarrier waveform that enables high data rates and spectrum efficiency improvements. The primary drawback of CPOFDM is that it has a high peak to average power ratio (PAPR), which is a characteristic of all multicarrier modulation techniques. We study the application of a Group Codeword Shift (GCS) approach to reduce the peak to average power ratio (PAPR) in a CPOFDM system in this article. Additionally, we compared the results of peak to average power ratio (PAPR) reduction with low complexity in CPOFDM using a Group Codeword Shift (GCS) approach, Selective Codeword Shift (SCS), Median Codeword and Conventional CPOFDM.

Energy Harvesting for TDS-OFDM in NOMA-Based Underwater Communication Systems.

Non-orthogonal multiple access (NOMA) is considered a promising multiple access technique for fifth generation (5G) mobile networks and tactical internet due to its high spectral efficiency. Thanks to the high spectral efficiency of NOMA, it can be a strong candidate suitable for the limited channel bandwidth of underwater acoustic communication. The NOMA transmitter is employing superposition coding (SC). The NOMA receiver is based on the successive interference cancellation (SIC) technique. The multicarrier NOMA adopts orthogonal frequency division multiplexing (OFDM) as a multicarrier modulation (MCM) technique; however, conventional cyclic prefix OFDM (CP-OFDM) and zero padding (ZP-OFDM) have inefficient spectral efficiency. Thanks to efficient synchronization and high energy-spectral efficiency of the time-division synchronization OFDM (TDS-OFDM), it is a significant attractive candidate for underwater multicarrier communication. However, wasting the power transmission of long guard intervals in the battery-based underwater communication is represented as one of the TDS-OFDM main drawbacks. Harvesting energy and improving the energy efficiency of acoustic-based TDS-OFDM-NOMA represent high achievement goal battery recharging challenges due to the ocean environment. This paper proposes time switching simultaneous wireless information and power transfer (TS-SWIPT) to harvest the energy of transmitted power over the guard interval in the TDS-OFDM-NOMA scheme. The proposed energy harvested scheme harvests the energy from the wasted power in the long guard interval and improves the energy efficiency of the TDS-OFDM multicarrier scheme. This study demonstrates the superiority of the proposed TDS-OFDM-NOMA over the underwater acoustic channel by revealing high energy efficiency, high spectral efficiency, better bit error rate performance, and high system data throughput.

X-Transform Time-Domain Synchronous IM-OFDM-SS for Underwater Acoustic Communication

Time-domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) is presented to enhance the spectral and energy efficiency over the conventional cyclic prefix OFDM and zero padding OFDM, but the interbloc interference (IBI) between the data block and adjacent pilot symbols deteriorates its performance. The IBI is considered as the main TDS-OFDM drawback in the harsh long-delay underwater acoustic (UWA) multipath channel. This article proposes a new scheme called X-transform time-domain synchronous index modulation (IM) OFDM to eliminate the TDS-OFDM IBI, explore the multipath diversity, and reduce the peak-to-average power ratio (PAPR). Particularly, X-transform, which merges the discrete Hartley transform and discrete Fourier transform in a very low-complexity unitary matrix, and IM techniques have been employed to remove the effects of IBI existing in underwater acoustic (UWA) TDS-OFDM. Moreover, compressive sensing has been adopted to guarantee a reliable UWA channel estimation based on a guard interval IBI-free region. The proposed scheme is evaluated over simulated and experimental UWA channels. The computer simulation and the real experiment show the outperformance of the proposed scheme in terms of bit error rate, computational complexity, PAPR, energy efficiency, and spectral efficiency over its conventional benchmarks.

A Comparison of CP-OFDM, PCC-OFDM and UFMC for 5G Uplink Communications

Polynomial-cancellation-coded orthogonal frequency division multiplexing (PCC-OFDM) is a form of OFDM that has waveforms which are very well localized in both the time and frequency domains and so it is ideally suited for use in the 5G network. This paper analyzes the performance of PCC-OFDM in the uplink of a multiuser system using orthogonal frequency division multiple access (OFDMA) and compares it with conventional cyclic prefix OFDM (CP-OFDM), and universal filtered multicarrier (UFMC). PCC-OFDM is shown to be very much less sensitive to time and frequency offsets than either CP-OFDM or UFMC. For a given constellation size, PCC-OFDM in additive white Gaussian noise (AWGN) requires 3 dB lower signal-to-noise ratio (SNR) for a given bit-error-rate, and the SNR advantage of PCC-OFDM increases rapidly when there are timing and/or frequency offsets. For PCC-OFDM no frequency guard-band is required between different OFDMA users. PCC-OFDM is completely compatible with CP-OFDM and adds negligible complexity and latency, because it uses a simple mapping of data onto pairs of subcarriers at the transmitter, and a simple weighting-and-adding of pairs of subcarriers at the receiver. The weighting-and-adding step, which has been omitted in some of the literature, is shown to contribute substantially to the SNR advantage of PCC-OFDM. A disadvantage of PCC-OFDM (without overlapping) is the potential reduction in spectral efficiency because subcarriers are modulated in pairs, but this reduction is more than regained because no guard band is required and because, for a given channel, larger constellations can be used.

Time Spread-Windowed OFDM for Spectral Efficiency Improvement

This letter proposes a new orthogonal frequency division multiplexing (OFDM)-based waveform, called time spread-windowed OFDM (TS-W-OFDM). TS-W-OFDM applies a windowing procedure to improve spectral efficiency and a time spreading method to create a block signal structure. Numerical results show that TS-W-OFDM has higher spectral efficiency and nearly same error rate compared to the conventional cyclic prefix-OFDM, windowed-OFDM (W-OFDM), weighted overlap and add-based OFDM (WOLA-OFDM), and filtered-OFDM (F-OFDM). In addition, they also show that TS-W-OFDM has lower complexity than W-OFDM, WOLA-OFDM, and F-OFDM.

Two‐stage frequency‐domain oversampling receivers for cyclic prefix orthogonal frequency‐division multiplexing systems

Orthogonal frequency-division multiplexing (OFDM) is a widely adopted technique in most wireless applications. It has been shown that zero padded OFDM (ZP-OFDM) with frequency-domain oversampling (FDO) can exhibit better performance than cyclic prefix OFDM (CP-OFDM) if the whole OFDM symbol is oversampled in the frequency domain. In this study, the authors propose a novel FDO-based scheme for CP-OFDM, which consists of two stages. First, the conventional CP-OFDM receiver is adopted to estimate the transmitted data and channel information. Second, the received symbol is reconstructed to reduce inter-symbol interference and oversampled in the frequency domain. The proposed scheme combines FDO and symbol reconstruction together, which enables the minimum mean square error (MMSE) and zero forcing (ZF) equalisers to exploit the channel information in high-dimensional non-orthogonal subcarrier domain and thus significantly suppress the interference on multipath channels. Simulation results show that the proposed FDO-MMSE CP-OFDM receiver can achieve much better bit error rate performance than the traditional CP-OFDM receiver and is comparable to the ZP-OFDM receiver with FDO.

Phase Noise Correction Based on TPS Symbols for the Chinese DTTB System

In orthogonal frequency division multiplexing (OFDM) system, phase noise (PHN) from oscillator can severely reduce the performance by causing: common phase error (CPE) and inter-carrier interference (ICI). The impact of PHN on received signal can be characterized by the circular convolution of the transmitted signal and the discrete Fourier transform (DFT) of PHN signal in frequency domain. Digital television/terrestrial multimedia broadcasting (DTMB), announced as the Chinese digital television terrestrial broadcasting (DTTB) standard, adopted the time-domain synchronous OFDM system (TDS-OFDM) system which has 36 continuous transmission parameter signaling (TPS) symbols in frequency domain which be used for PHN suppression. Based on a linearized parametric model for PHN, least squared (LS) estimation and fast Fourier transform (FFT) approaching method for PHN correction are proposed in this paper. The effects of the PHN on channel estimation in both TDS-OFDM system and conventional cyclic prefix OFDM (CP-OFDM) are also investigated. Simulations show that the proposed algorithm can effectively reduce the PHN and improve the symbol error rata (SER) of TDS-OFDM systems over both additive white Gaussian noise (AWGN) and broadcasting multipath channel. In practice, the FFT-approaching method can be applied to the DTMB receiver-chip design directly with low implementation cost.

Analysis, Optimization, and Implementation of Low-Interference Wireless Multicarrier Systems

This paper considers pulse-shaping multicarrier (MC) systems that transmit over doubly dispersive fading channels. We provide exact and approximate expressions for the intersymbol and intercarrier interference occurring, in such systems. This analysis reveals that the time and frequency concentration of the transmit and receive pulses is of paramount importance for low interference. We prove the (nonobvious) existence of such jointly concentrated pulse pairs by adapting recent mathematical results on Weyl-Heisenberg frames to the MC context. Furthermore, pulse optimization procedures are proposed that aim at low interference and capitalize on the design freedom existing for redundant MC systems. Finally, we present efficient FFT-based modulator and demodulator implementations. Our numerical results demonstrate that for realistic system and channel parameters, optimized pulse-shaping MC systems can outperform conventional cyclic-prefix OFDM systems