Chun-Hung Ho

1.1-Gb/s White-LED-Based Visible Light Communication Employing Carrier-Less Amplitude and Phase Modulation

We demonstrate 1.1-Gb/s visible light communication (VLC) employing carrier-less amplitude and phase modulation (CAP) and a commercially available phosphorescent white light emitting diode (LED). Optical blue filtering, precompensation, and decision feedback equalization are used to compensate the frequency response of the phosphor-based white LED. Various modulation orders of CAP signals are investigated to maximize the capacity of the VLC system. The record data rate of 1.1 Gb/s with the bit error rate performance below the FEC limit of 10-3 is successfully achieved >; 23-cm air-transmission via a 220-MBaud 32-CAP signal.

2 × 2 MIMO radio-over-fiber system at 60 GHz employing frequency domain equalization.

This work experimentally demonstrates the efficacy of the 2 × 2 multiple-input multiple-output (MIMO) technique for capacity improvement of a 60-GHz radio-over-fiber (RoF) system employing single-carrier modulation format. We employ frequency domain equalization (FDE) to estimate the channel response, including frequency response of the 60 GHz RoF system and the MIMO wireless channel. Using FDE and MIMO techniques, we experimentally demonstrate the doubling the of wireless data capacity of a 60 GHz RoF system to 27.15 Gb/s using 16-QAM modulation format, with transmission over 25 km of standard single-mode fiber and 3 m wireless distance.

High spectral efficient W-band OFDM-RoF system with direct-detection by two cascaded single-drive MZMs

W-band wireless transmission has attracted a lot of interest due to its wider available bandwidth (i.e. 75-110 GHz). In this article, we propose a direct-detection orthogonal frequency division multiplexing radio over fiber (OFDM-RoF) system via two cascaded single-drive MZMs at center frequency of 103 GHz. We discuss maximum bandwidth of different modulation formats under forward error correction (FEC) threshold (3.8 x 10(-3)). Up to 40-Gbps 16-QAM OFDM signals is achieved over 25-km fiber and 2-m wireless transmission. To overcome the penalty from uneven frequency response, bit-loading algorithm is applied to discuss data rate and spectral efficiency with signal bandwidth from 5 to 10 GHz. With 10-GHz bandwidth, 46.4-Gb/s data rate and 4.64-bit/s/Hz spectral efficiency was achieved. To achieve 40-Gbps data rate, the required bandwidth of OFDM signal with bit-loading is 2 GHz less than that without bit-loading.

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Multiple-input-multiple-output (MIMO) technology is a promising method to increase spectral efficiency in wireless communications. In this paper, a 60-GHz orthogonal frequency-division multiplexing radio over fiber (OFDM-RoF) system employing 2 × 2 MIMO wireless technology is demonstrated. With the proposed equalizer employing least mean squares (LMS) algorithm, MIMO channel mixing and I/Q-mismatch can be compensated simultaneously. 16-QAM and 32-QAM OFDM signal transmissions under forward error correction (FEC) threshold ( 1×10-3) are demonstrated. A data rate of 76.3 Gb/s can be achieved with a bit-loading algorithm over 25-km fiber transmission and 3.5-m wireless transmission.

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Multiple-input-multiple-output (MIMO) technique for wireless communications is extensively used these days, especially to increase the spectral efficiency of new wireless communication systems like LTE, WiMAX, etc. MIMO in combination with robust modulation techniques like orthogonal frequency division multiplexing (OFDM) provides a good solution for high data rate wireless links. In this paper, the performance of MIMO for a 60 GHz OFDM radio over fiber link is analyzed. System performance of the MIMO system for different antenna spacing is also studied. Using the optimum system parameters, a MIMO OFDM wireless link of up to 51 Gb/s was successfully demonstrated at 60 GHz in a bandwidth of <;7 GHz, with a wireless transmission distance of up to 4 m and optical fiber transmission of 1 km. To our knowledge this is the highest data rate demonstrated in the 7 GHz band of 60 GHz.

2 MIMO OFDM-RoF System Employing LMS-Based Equalizer With I/Q Imbalance Compensation at 60 GHz

We experimentally demonstrated an adaptive I/Q imbalance correction scheme to compensate I/Q-imbalance. With I/Q correction, a 32.65-Gbps OFDM signal at 60 GHz within 7-GHz license-free band is successfully generated and, following 25km SMF transmission, negligible power penalty is observed.

Performance Evaluation of a 60 GHz Radio-over-Fiber System Employing MIMO and OFDM Modulation

This paper investigates the efficacy of two methods for compensating I/Q imbalance, which causes serious performance problems in wideband (6.98-GHz spectrum) millimeter-wave systems employing MIMO signal transmission. A 60-GHz orthogonal frequency division multiplexing (OFDM) RoF system employing 2 × 2 MIMO technology is implemented using a commonly used training symbol arrangement and a proposed method. We experimentally demonstrate that the proposed training symbol arrangement performed significantly better than the commonly used approach. By combining the proposed training symbol arrangement with LMS I/Q compensation and bit-loading, we achieve an extremely high wireless data rate transmission of 75.211 Gb/s over both 50 km of standard single-mode fiber and 3.5-m wireless distance. The optical power penalty after 50-km fiber transmission was only ~1 dB.

32.65-Gbps OFDM RoF signal generation at 60GHz employing an adaptive I/Q imbalance correction

This paper presents a simple 2 × 2 multiple-input multiple-output (MIMO) 60-GHz radio-over-fiber system. Due to the proposed specific frequency arrangement of driving signals, each optical transmitter requires only a single-drive Mach-Zehnder modulator with 3-dB bandwidth of less than 35 GHz. This arrangement of frequencies can increase the tolerance of optical signals to dispersion-induced RF fading, thereby extending fiber transmission distance. Unfortunately, this scheme leads to signal-to-signal beating interference (SSBI), which can deteriorate system performance. Thus, we employed a 2 × 2 MIMO scheme to enhance data capacity by combining two data streams and two corresponding SSBIs prior to signal demodulation. We also developed a novel iterative equalization technique to mitigate SSBI in the MIMO system. The proposed system achieved a maximum capacity of 55.9-Gb/s in the transmission of 7-GHz orthogonal frequency division multiplexing signals over 12-km fiber and 3.5-m air transmission using a bit-loading algorithm.

Theoretical and Experimental Investigation of a 2 × 2 MIMO OFDM Radio-Over-Fiber System at 60-GHz With I/Q Imbalance Compensation

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.

Simple 2 × 2 MIMO 60-GHz Optical/Wireless System With Extending Fiber Transmission Distance

2 × 2 MIMO RoF system employing single-sideband single-carrier modulation is experimentally demonstrated. Compared with OFDM, it has lower PAPR. The highest 84-Gbps data rate within 7-GHz unlicensed band at 60 GHz can be achieved.