Shihao Zhang

Experimental Demonstration of IFDMA for Uplink Visible Light Communication

In this letter, we propose an experimental demonstration of uplink visible light communications based on interleaved frequency division multiple access (IFDMA) with high spectral and power efficiencies, low complexity of the transmitter, high tolerance against multipath-induced distortion, and synchronization error. We show that IFDMA with a lower peak-to-average power ratio offers improved bit error rate (BER) performance compared with the orthogonal frequency division multiplexing access. For the uplink, the increase in the transmission span is ~4 cm at a BER of 10-5.

Efficient frequency-domain channel equalisation methods for OFDM visible light communications

We present efficient frequency domain channel estimation methods based on the ISFA, MMSE and WIFA schemes for the orthogonal frequency division multiplexing (OFDM) visible light communications (VLC) system.

Experimental Demonstration of OFDM/OQAM Transmission for Visible Light Communications

We propose a modified orthogonal frequency division multiplexing/offset quadrature amplitude modulation (OFDM/OQAM) scheme for visible light communications (VLC). The OFDM/OQAM VLC system can efficiently boost the data rate, and combat multipath induced the inter symbol interference (ISI) and inter carrier interference (ICI). To combat the effect of intrinsic imaginary interference, intrasymbol frequency-domain averaging and minimum mean squared error (MMSE), combined with interference approximation method, are proposed. The experiment results show that the proposed system offers similar bit error rate performance to that of OFDM, while the bit rate is increased by 9% for the elimination of cyclic-prefix and guard band.

Time-domain channel estimator for polarization interleaving direct-detection orthogonal frequency-division multiplexing passive optical network

We propose an efficient time-domain channel estimation method for polarization interleaving orthogonal frequency-division multiplexing passive optical network with direct detection. Compared with the frequency-domain least-square channel estimator and intrasymbol frequency-domain averaging, the time-domain channel estimator with overhead reduction demonstrates better system robustness against transmission impairments, such as optical noise, chromatic dispersion, and polarization mode dispersion.

Efficient frequency-domain channel equalization methods for dual-polarization orthogonal frequency-division multiplexing/offset quadrature amplitude modulation-passive optical network

Abstract. We present dual-polarization orthogonal frequency-division multiplexing/offset quadrature amplitude modulation (OFDM/OQAM) transmission for passive optical network (PON) with intensity modulation and direct detection, which has high spectral efficiency and high robustness against chromatic dispersion (CD) and polarization mode dispersion (PMD). The frequency-domain optical fiber channel transmission model for dual-polarization OFDM/OQAM-PON with the CD- and PMD-induced intrinsic imaginary interference (IMI) effect is systemically deduced. The intrasymbol frequency-domain averaging (ISFA) and minimum mean-squared error (MMSE) with the full loaded (FL) and half loaded (HL) preamble structures are used to mitigate the IMI effect. Compared with the conventional interference approximation method, the ISFA and MMSE offer improved receiver sensitivity. For channel estimation, the FL method is more effective than the HL method in mitigating the IMI effect and optical noise.

Weighted interframe averaging-based channel estimation for orthogonal frequency division multiplexing passive optical network

Abstract. Weighted interframe averaging (WIFA)-based channel estimation (CE) is presented for orthogonal frequency division multiplexing passive optical network (OFDM-PON), in which the CE results of the adjacent frames are directly averaged to increase the estimation accuracy. The effectiveness of WIFA combined with conventional least square, intrasymbol frequency-domain averaging, and minimum mean square error, respectively, is demonstrated through 26.7-km standard single-mode fiber transmission. The experimental results show that the WIFA method with low complexity can significantly enhance transmission performance of OFDM-PON.

Experimental demonstration of visible light communications with OFDM/OQAM modulation

We propose a modified OFDM/OQAM scheme for VLC, which can efficiently boost the data rate and combat multipath induced distortions. To combat the effect of IMI, ISFA and MMSE combined with IAM are proposed.

Dual-polarization OFDM/OQAM-PON with efficient channel equalization methods

We present dual-polarization OFDM/OQAM transmission for passive optical network. The ISFA and MMSE with the full loaded and half loaded preamble structures are used to mitigate the intrinsic imaginary interference.

Interleaved frequency division multiple access for uplink VLC

We propose an uplink visible light communication (VLC) scheme based on interleaved frequency division multiple access (IFDMA), which provides some highly desirable features such as high spectral efficiency and high tolerance against multipath distortion. Compared with OFDMA, the IFDMA has lower PAPR and lower computation complexity at the transmitter. The experiment results show that the increased transmission span is about 7.5-cm at a BER of 10−5 for IFDMA compared with the OFDMA.

Time-domain channel estimation for polarization interleaving OFDM-PON

We propose an efficient time-domain channel estimation method for polarization interleaving orthogonal frequency division multiplexing passive optical network (OFDM-PON) with direct detection. Compared with the frequency-domain least square channel estimator (FLSE) and intra-symbol frequency-domain averaging (ISFA), the time-domain channel estimator (TD-CE) with overhead reduction demonstrates better system robustness against transmission impairments, such as optical noise, chromatic dispersion, and polarization mode dispersion.