OFDM-RoF System Research Articles

3×3 MIMO 60-GHz OFDM-RoF System With Long-Distance Wireless Transmission Enabled by MIMO Volterra Filtering

A 3×3 60-GHz multiple-input multiple-output (MIMO) radio-over-fiber system with an MIMO Volterra filter was demonstrated. The main objective of the proposed scheme is to compensate for the nonlinear distortion caused by radio frequency (RF) power amplifiers (PAs) before the signals reaches the transmitter antennas—particularly when the PAs operate with a high input power to achieve a high output RF power for long-distance wireless transmission. When the required wireless transmission distance is only 7 m, the 3×3 MIMO system with careful control of the PA input power can achieve a data rate of 126 Gbps. However, the data rate decreases rapidly over a longer wireless distance because of the larger loss. By eliminating nonlinear distortion and interchannel interference simultaneously, MIMO Volterra filtering can significantly increase the achievable data rate of a long-distance system. When the required data rate is 90 Gbps (or 100 Gbps), the maximum wireless transmission distance is 118 m (or 70 m) with the aid of MIMO Volterra filtering, but it is only 74 m (or 40 m) without MIMO Volterra filtering.

Precoding-enabled OFDM-ROF transmission system with self-pumping structure

Precoding-enabled orthogonal frequency division multiplexing (OFDM) is proposed in radio-over-fiber (ROF) system based on a flexible self-pumping structure. Different from the use of two lasers, one laser-driven Mach-Zehnder modulator generates multiple spectra and forms self-pumping structures by selecting signal and pump light, which can effectively reduce the system cost and eliminate the laser phase conversion noise. The signal-to-noise ratio (SNR) of OFDM-ROF fluctuates wildly induced by non-ideal frequency response of optical/electrical devices and channel fading effects, and the BER performance is severely deteriorated. Therefore, seven common channel-independent precoding techniques are used and evaluated for the OFDM-ROF systems. The analysis of the results shows that seven precoding techniques can equalize uneven SNR on data subcarriers. Meantime, constant amplitude zero autocorrelation sequence-based matrix transform (CAZACT), Zadoff-Chu matrix transform (ZCT), discrete Fourier transform (DFT) have significant advantages in reducing the peak-to-average power ratio (PAPR). When the received optical power (ROP) is −3dBm, the BERs of the system under the seven precoding schemes are all lower than the hard decision - forward error correction threshold (HD-FEC). In addition, receiver sensitivity and comb flatness gain can also be achieved by the precoded OFDM compared to the conventional OFDM.

Distinguishing the effect of frequency selective fading of a low cost 64 quadrature amplitude modulation direct-detection OFDM ROF system employing fiber Bragg grating to generate optical mm-wave

Distinguishing the effect of frequency selective fading of a low cost 64 quadrature amplitude modulation direct-detection OFDM ROF system employing fiber Bragg grating to generate optical mm-wave

Analyzing the BER and optical fiber length performances in OFDM RoF links

Radio over fiber (RoF) can be assessed as a system of most convenient combination of optical fiber and radio signals. The technique of orthogonal frequency division multiplexing (OFDM) considers as a data distribution over a huge number of carriers having spaced from each other with specific frequencies at overlap bands. Hence incorporates OFDM with the optical fiber, OFDM-RoF system can be increased the modulation RF access capacity besides high-speed data transmission, it considers a broadband communication trend of the current and future applications specifically for 5G mobile. The optical network scenarios of various RF can be model with optisystem software, and OFDM in addition to use a section of the orthogonal multiplex frequency of 16-quadrature amplitude modulation (QAM) RF modulating signal. In the optical domain, Mach-Zehnder modulator (MZM) optical modulators are used to carry out different results with different fiber lengths. An OFDM-RoF wireless communication system considers as advanced data rate transmission achievement by minimum delays. The essential goal of this paper is for identifying the minimum bit error rate (BER) for the 16-QAM modulation with varying fiber length. The OFDM-RoF system can be able for realizing a fiber length 100 km with a restricted decreasing in the received power so that the constellation noise is became greater despite of applying electrical amplification and optical amplification.

Probabilistic shaping based constellation encryption for physical layer security in OFDM RoF system.

The physical layer security of radio-over-fiber (RoF) system is a very important problem for future communication. In this paper, a novel probabilistic shaping (PS) based constellation encryption scheme is proposed in which two bit-level encryption operations are firstly performed according to chaotic sequences and hash values. The chaotic sequences are generated by hyperchaotic system and hash values are obtained by SHA-512. Then PS is applied to enhance transmission performance. After PS-16-quadrature amplitude modulation (QAM), constellation encryption is implemented aiming at maintaining overall shaping distribution unchanged and improving security. An encrypted PS-16-QAM orthogonal frequency division multiplexing (OFDM) signal is successfully transmitted over 50 km standard single-mode fiber (SSMF) and 5 m wireless channel in our experiment. The results demonstrate that the key space of 10121 is achieved to defend malicious attacks. Moreover, the proposed PS-based encryption scheme can obtain approximately 2.4 dB gain at a BER of 10-3 compared with traditional OFDM signal. Thus, the proposed scheme has a good application prospect in the future OFDM-RoF system due to the dominant BER and security performance.

Analysis of a framework implementation of the transceiver performances for integrating optical technologies and wireless LAN based on OFDM-RoF

The greatest advantages of optical fibers are the possibility of extending data rate transmission and propagation distances. Being a multi-carrier technique, the orthogonal frequency division multiplexing (OFDM) can be applicable in hybrid optical-wireless systems design owing to its best spectral efficiency for the interferences of radio frequency (RF) and minor multi-path distortion. An optical OFDM-RoF-based wireless local area network (W-LAN) system has been studied and evaluated in this work. The outline for integrating an optical technology and wireless in a single system was provided with the existence of OFDM-RoF technology and the microstrip patch antenna; these were applied in the Optisystem communication tool. The design of the proposed OFDM-RoF system is aimed at supporting mm-wave services and multi-standard operations. The proposed system can operate on different RF bands using different modulation schemes like 4,16 and 64QAM, that may be associated to OFDM and multidata rates up to 5 Gbps. The results demonstrate the robustness of the integrated optical wireless link in propagating OFDM-RoF-based WLAN signals across optical fibers.

Enhanced sampling frequency offset resistance method based on precoding technique in W-band OFDM RoF systems

Precoding technique is proposed and experimental demonstrated to resist sampling frequency offset (SFO) in W-band OFDM RoF systems. Walsh–Hadamard transform (WHT)-precoding, discrete Hartley transform (DHT)-precoding, Zadoff–Chu transform (ZCT)-precoding, and orthogonal circulant matrix transform (OCT)-precoding are investigated and compared. SFO-induced inter-carrier interference (ICI) on each subcarrier of conventional OFDM and OFDM with precoding (precoded-OFDM) are theoretical analyzed. Experimental results indicate OFDM with OCT-precoding (OCT-OFDM) can obtain a remarkable resistance to the SFO-induced ICI in W-band OFDM RoF systems.

A-STBC incorporated power-efficient Radio over Fibre system

MIMO–OFDM based Radio over Fibre (RoF) system has emerged as a potential candidate to realize highly-reliable, power- and spectral-efficient wireless systems. However, low spectral-efficiency in conjunction with high peak-to-average power ratio (PAPR) of the FFT based conventional OFDM degrades the system performance and demands high power to attain the required BER. To reduce this high power requirement to attain the threshold BER (10−3), a discrete wavelet transform (DWT) approach is incorporated with conventional MIMO–OFDM-RoF system in this work. The proposed Wavelet-OFDM (W-OFDM) system is integrated with Alamouti-Space–time Block Codes (A-STBC) and the resulting MIMO–OFDM signal is transported over a RoF link of 10 Km in the presence of non-linearity. Moreover, at radio access point (RAP), the received RF signals are transmitted over Rayleigh faded wireless-channel in the presence of additive white Gaussian noise (AWGN) and phase-offset arising due to imperfect carrier phase-estimation. The proposed system equipped with 16-PSK and 64-PSK modulation schemes claims power efficacy of 68% and 40% respectively in achieving the threshold BER in contrast to the conventional system under low non-linearity scenario.

Real-Time Generation and Reception of OFDM Signals for $X$ -Band RoF Uplink With Heterodyne Detection

A field-programmable gate arrays-based real-time orthogonal frequency-division multiplexing (OFDM) transceiver is implemented for the uplink of an $X$ -band radio-over-fiber (RoF) system with heterodyne detection for the first time. Digital intermediate-frequency $I/Q$ modulation and demodulation, and forward error correction are applied. Minn’s timing synchronization method is slightly modified with reduced implementation complexity for the proposed OFDM-RoF system. By using Reed–Solomon code with symbol interleaving technique, the real-time transmission of the $X$ -band 16-ary quadrature amplitude modulation OFDM-RoF signal over 10-m wireless and 2.26-km single mode fiber link is successfully achieved with a post-FEC bit error rate below $1\times 10^{-9}$ .

Performance Analysis of Digital Modulation for Coherent Detection of OFDM Scheme on Radio over Fiber System

Radio over fiber (RoF) system with the coherent detection offers high linearity for the transparent transport of high-frequency microwave signals, and better receiver sensitivity compared with intensity-modulated direct detection systems. The purpose of this paper is to analyze the performance of digital modulation for coherent detection of orthogonal frequency division multiplexing (OFDM) scheme on RoF system at 10 Gbps up to 100 km fiber length. The results show that coherent detection of OFDM-RoF system with 16 quadrature amplitude modulation (16-QAM) has the value of bit error rate (BER) and the symbol error rate (SER) is very low and its constellation is better compared with other modulation formats (4-QAM, quadrature phase shift keying (QPSK), 8-PSK and 16-PSK), which BER 16-QAM is 0.053 and SER is 15.7%. The results also show that BER value of 4-QAM and QPSK relatively similar to fiber length variations. In general, an increasing value of the BER and SER for each modulation format are almost equal to the fiber length of 60-70 km (Region I and II). However, there is a significant increase in the value of BER in fiber length of 80-100 km (Region III. A and III. B) for the modulation of 4-QAM, QPSK, 8-PSK, and 16-PSK.

Performance Analysis of Digital Modulation for Coherent Detection of OFDM Scheme on Radio over Fiber System

Radio over fiber (RoF) system with the coherent detection offers high linearity for the transparent transport of high-frequency microwave signals, and better receiver sensitivity compared with intensity-modulated direct detection systems. The purpose of this paper is to analyze the performance of digital modulation for coherent detection of orthogonal frequency division multiplexing (OFDM) scheme on RoF system at 10 Gbps up to 100 km fiber length. The results show that coherent detection of OFDM-RoF system with 16 quadrature amplitude modulation (16-QAM) has the value of bit error rate (BER) and the symbol error rate (SER) is very low and its constellation is better compared with other modulation formats (4-QAM, quadrature phase shift keying (QPSK), 8-PSK and 16-PSK), which BER 16-QAM is 0.053 and SER is 15.7%. The results also show that BER value of 4-QAM and QPSK relatively similar to fiber length variations. In general, an increasing value of the BER and SER for each modulation format are almost equal to the fiber length of 60-70 km (Region I and II). However, there is a significant increase in the value of BER in fiber length of 80-100 km (Region III. A and III. B) for the modulation of 4-QAM, QPSK, 8-PSK, and 16-PSK.

Performance analysis of BER in OFDM-RoF system using 16-QAM modulation for wireless network

Orthogonal Frequency Division Multiplexing (OFDM) is a modulation technique to transmit wired and wireless media. Radio over Fibre (RoF) system consists of both wireless and optical links. It is proved technology for the wireless access technique, and the OFDM has core technology for major part of the wireless network. The OFDM-RoF system is the subject of much research of various topics at the moment. OFDM-RoF system provides high speed, large capacity and high spectral efficiency in the recent 4G and upcoming 5G mobile technology with fast data transmission. OFDM has specific modulation methods such as PSK, BPSK, QPSK, and QAM techniques. The aim of this paper is to perform and simulate BER and Q-Factor of OFDM-RoF system at different parameters, including 16-QAM modulation technique using OptiSystem13.0 simulation software.

Performance analysis of BER in OFDM-RoF system using 16-QAM modulation for wireless network

Orthogonal Frequency Division Multiplexing (OFDM) is a modulation technique to transmit wired and wireless media. Radio over Fibre (RoF) system consists of both wireless and optical links. It is proved technology for the wireless access technique, and the OFDM has core technology for major part of the wireless network. The OFDM-RoF system is the subject of much research of various topics at the moment. OFDM-RoF system provides high speed, large capacity and high spectral efficiency in the recent 4G and upcoming 5G mobile technology with fast data transmission. OFDM has specific modulation methods such as PSK, BPSK, QPSK, and QAM techniques. The aim of this paper is to perform and simulate BER and Q-Factor of OFDM-RoF system at different parameters, including 16-QAM modulation technique using OptiSystem13.0 simulation software.

W-band OFDM Radio-over-Fiber system with power detector for vector signal down-conversion.

This Letter proposes a W-band OFDM RoF system at 103.5 GHz employing power detector to support vector signal down-conversion. Additional RF tone is generated and transmitted from central office to replace the local oscillator at a wireless receiver. With a proper frequency gap and power ratio between the RF tone and the OFDM-modulated signal, the impact from signal-to-signal beating interference can be minimized. The data rate can achieve a 40 Gbps 16 QAM OFDM signal over 25 km fiber and 2 m wireless transmission.

DM-DD OFDM-RoF System With Adaptive Modulation Using a Gain-Switched Laser

We propose a 60-GHz orthogonal frequency division multiplexing (OFDM) radio over fiber system based on direct modulation-direct detection using an externally injected gain-switched DFB laser with adaptive modulation format. Power fading due to chromatic dispersion is mitigated by optimizing the bias current. Adaptive modulation for OFDM is used to improve the signal transmission performance. A 15.31-Gb/s 60-GHz OFDM signal generation and transmission over 25-km standard single-mode fiber is experimentally demonstrated.

WDM–OFDM–RoF system based on optical coupling tandem single-sideband modulation

The authors report on a WDM–OFDM–RoF system based on a novel optical coupling tandem single-sideband (O-TSSB) transmitter for one wavelength carrying two radio frequency signals. The impact of nonlinear distortion consisting of harmonic distortion and intermodulation distortion in this system is theoretically investigated and it has been found that the O-TSSB transmitter can reduce the nonlinear distortion effectively. Transmission over 25 and 50 km of standard single mode fiber is successfully demonstrated and it indicates that the modulation index 0.6 is more adapted to O-TSSB transmitter. The error vector magnitude of the system based on O-TSSB transmitter after transmission over 25 km is $$<$$ 0.05, relative to the traditional electric coupling tandem single-sideband transmitter. For O-TSSB transmitter, all channels after 25 km transmission achieve performance below the $$10^{-3}$$ forward error correction limit.

60-GHz Direct Modulation-Direct Detection OFDM-RoF System Using Gain-Switched Laser

We propose a 60-GHz orthogonal frequency-division multiplexing radio over fiber system based on direct modulation-direct detection using an externally injected gain-switched distributed feedback (DFB) laser. External injection from a master laser into the gain-switched DFB laser is used to mitigate chirp in the directly modulated DFB laser and 25-km fiber transmission is investigated. Power fading due to multipath transmission induced by fiber chromatic dispersion is theoretically analyzed and experimentally demonstrated.

A Novel Cost-effective OFDM WDM-PON Radio Over Fiber System Employing FBG to Generate Optical mm-wave

AbstractWe have investigated and demonstrated a novel scheme to generate 2.5 Gbit/s 64 QAM orthogonal frequency division multiplexing (OFDM) signals for Radio Over Fiber (ROF) systems. We employ Fiber Bragg Grating (FBG) because the repetitive frequency of the RF source and the bandwidth of the optical modulator are largely reduced and the architecture of the ROF system is simpler. Wavelength-Division-Multiplexed Passive Optical Network (WDM-PON) has been considered as a promising solution for future broadband access networks. Principle of WDM-PON access network compatible with OFDM-ROF systems is investigated. This novel scheme which has multiple double-frequency technique to generate mm-wave signal to carry OFDM signals is a practical scheme to be applied for future broadband access networks.

40 Gb/s 4-QAM OFDM radio over fiber system at 60 GHz employing coherent detection

In this paper, the simulation of 60 GHz millimeter-wave radio over fiber link with 4-QAM OFDM modulation format at 40 Gb/s over 150 km SMF is proposed. The 60 GHz millimeter-wave signal is generated by the optical heterodyne method. Coherent detection has been used at the receiver to down-convert millimeter-wave signal to IF band. Introduction of the OFDM modulation in RoF-based system realizes the benefits of higher order modulations (such as 4-QAM, 16-QAM, etc.) to ensure the good spectral efficiency and multi-gigabit access. The performance of the system is analyzed by Q-factor and BER by which it can be shown that the best results are obtained at the input power of 10 dBm. The simulation results clearly demonstrate the feasibility of this 4-QAM OFDM RoF system over 150 km fiber link.

Chromatic Dispersion-Induced Optical Phase Decorrelation in a 60 GHz OFDM-RoF System

We propose and demonstrate a 25-Gb/s 16-quadrature amplitude modulation orthogonal frequency division multiplexing 60-GHz radio over fiber transmission system based on a gain-switched optical comb source. The impact of the phase noise caused by the optical phase decorrelation due to the chromatic dispersion is theoretically studied and experimentally investigated by employing a high linewidth comb source and transmitting over a 50-km standard single-mode fiber reel. A time delay precompensation is deployed based on the study of phase noise in order to reduce the phase noise impact, and thereby improve system performance.