Browsing by Author "Liu, Huan-Ching"

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Analog-to-Digital Conversion Using Sub-Nyquist Sampling Rate in Flexible Delay-Division Multiplexing OFDMA PONs
(2016-05-15)
Wei, Chia-Chien
;
Liu, Huan-Ching
;
Lin, Chun-Ting
;
Chi, Sien
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光電系統研究所
This paper details a delay-division multiplexing (DDM) scheme for orthogonal frequency-division multiple access (OFDMA) passive optical networks (PONs). Unlike detection in a conventional OFDMA PON, the detection of OFDM signals in the proposed scheme involves an analog-to-digital converter (ADC) operating at a sampling rate below the Nyquist rate for each optical network unit (ONU). Based on preallocated relative time delays among the ONUs, preprocessed signals sent from an optical line terminal can be detected as different downstream signals following spectral aliasing caused by ADCs operating at a sub-Nyquist sampling rate. It should be noted that the proposed scheme reduces the requirement of sampling rate, but not the analog bandwidth of an ADC, such that all sent subcarriers can be retained before spectral aliasing. Thus, the proposed DDM scheme can reduce computational complexity and power consumption in the demodulation process, leading to an improvement in cost efficiency. In experiments, we demonstrate that each ONU with an ADC operating at 1/2-1/32 of the Nyquist sampling rate is able to receive 1/2-1/32 of the downstream data, with an insignificant performance penalty. Furthermore, in the DDM scheme, the sampling instant of an ADC is a key parameter in the selection of required data. This paper also proposes a method for estimating the adjustments required in the sampling instant at ONUs. The proposed method is based on the use of deviations in the channel response, which provides the ability to identifywith a high degree of precision the adjustments required for an ADC with sub-Nyquist sampling rate. Estimation error associated with the necessary adjustments has only negligible effects on performance, thereby confirming the reliability of the proposed method.
Novel Delay-Division-Multiplexing OFDMA Passive Optical Networks Enabling Low-Sampling-Rate ADC
(2015)
Wei, Chia-Chien
;
Liu, Huan-Ching
;
Lin, Chun-Ting
;
光電系統研究所
;
Institute of Photonic System
Without extra hardware, the proposed delay-division-multiplexing scheme reduces sampling rate and FFT size at ONUs in OFDMA-PONs to 1/2 similar to 1/32 of conventional ones. Sending preprocessed signals, various aliasing-free subcarriers can be received dynamically by controlling delays.
Simple Receiving Scheme in 100-GHz DD OFDM RoF Systems Employing Low-Sampling-Rate ADCs and Digital Preprocess
(2015)
Liu, Huan-Ching
;
Lin, Chi-Hsiang
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Lin, Chun-Ting
;
Wei, Chia-Chien
;
Huang, Hou-Tzu
A simple low-sampling-rate receiving scheme is proposed for W-hand OFDM-RoF systems, Using the proposed preprocess, aliasing-free suhcarriers can be received, and employing the optimized delays to ADCs can achieve the performance insensitive to sampling rate.
W-band DD-OFDM-RoF System Employing Pilot-aided PAPR Reduction
(2014-01-01)
Huang, Hou-Tzu
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Lin, Chun-Ting
;
Liu, Huan-Ching
;
Hsu, Hsun-Hao
;
Wu, Meng-Fan
We propose and experimental demonstrate a high spectral efficiency direct-detection radio-over-fiber (DD-RoF) system in W-band. To overcome the issue of peak-to-average power ratio (PAPR) in orthogonal frequency-division multiplexing (OFDM) signals, this study proposes a pilot-aided PAPR reduction simplified from Tellado's tone reservation. Using a 10-GHz 16-QAM OFDM signal, BER was improved from 1.3 x 10(-3) to 5.0 x 10(-4) over 4-km fiber and 2-m wireless transmission. Using a 32-QAM OFDM signal, the pilot-aided PAPR reduction improved the data rate from 45.2 Gbps to 47.6 Gbps under FEC limits (BER=3.8 x 10(-3)).