@article{ihsan_energy-efficient_2025,

title = {Energy-Efficient TDMA-NOMA for RIS-Assisted Ultra-Dense VLC Networks},

author = {Asim Ihsan and Muhammad Asif and Wali Ullah Khan and Isaac N. O. Osahon and Sujan Rajbhandari},

doi = {10.1109/tgcn.2024.3511114},

issn = {2473-2400},

year  = {2025},

date = {2025-09-01},

journal = {IEEE Transactions on Green Communications and Networking},

volume = {9},

number = {3},

pages = {1239–1253},

abstract = {This paper proposes an energy-efficient optimization technique for downlink indoor visible light communication (VLC) systems using hybrid non-orthogonal multiple access (NOMA) and reconfigurable intelligent surfaces (RIS). The approach considers a hybrid time division multiple access-NOMA (TDMA-NOMA) to provide massive connectivity to multi-clusters. Clusters of users are formed using NOMA while TDMA is used to allocate a specific time slot within a communication frame. The proposed technique optimizes the precoding at the multi-LED transmitter, RIS tuning parameters, and time-slot allocation parameters for each cluster to maximize the system’s energy efficiency (EE). The EE optimization problem is solved through the block coordinate descent (BCD) framework, which splits the optimization problem into two blocks. An alternating optimization (AO) framework is used in the first block to optimize the transmit precoding through conic quadratic programming (CQP) and RIS tuning parameters through a semidefinite programming (SDP) technique based on the surrogate optimization method. The second block allocates energy-efficient time-slot for each cluster through linear programming (LP) approach to further improve the EE of the system. The simulation results indicate that the proposed BCD framework achieves fast convergence and excellent performance in terms of the EE of the system while maintaining low computational complexity.},

keywords = {Energy Efficiency, Hybrid TDMA-NOMA Systems, Reconfigurable Intelligent Surfaces, Resource Allocations, Visible Light Communication},

pubstate = {published},

tppubtype = {article}

}

@article{xu_integrated_2025,

title = {Integrated Positioning and Communication Relying on Wireless Optical OFDM},

author = {Chao Xu and Christos Masouros and Shinya Sugiura and Periklis Petropoulos and Robert G. Maunder and Lie-Liang Yang and Harald Haas and Lajos Hanzo},

url = {https://ieeexplore.ieee.org/abstract/document/10900727},

doi = {10.1109/JSAC.2025.3543532},

issn = {1558-0008},

year  = {2025},

date = {2025-05-01},

urldate = {2025-10-08},

journal = {IEEE Journal on Selected Areas in Communications},

volume = {43},

number = {5},

pages = {1721–1737},

abstract = {Visible Light Positioning and Communication (VLPC) is a promising candidate for implementing Integrated Sensing And Communication (ISAC) in the unlicensed 400 THz to 800 THz band. The current Visible Light Positioning (VLP) systems mainly operate based on the Received Signal Strength (RSS) of the Line-of-Sight (LoS) path. However, its accuracy is degraded by interferences from Non-LoS (NLoS) paths. Furthermore, in Visible Light Communication (VLC) systems, the estimation of Channel State Information (CSI) also becomes challenging, when the optical channel becomes dispersive. Against this background, we propose a new VLPC scheme using Direct Current (DC) biased Optical Orthogonal Frequency-Division Multiplexing (VLPC-DCO-OFDM), where OFDM-based sensing is applied for the sake of improving the resolution of the estimated Channel Impulse Response (CIRs) exploited for positioning functionality. The CIRs estimated by sensing are further exploited to provide enhanced CSI for communication data detection. Moreover, we propose a hybrid Radar-RSS based solution, where the conventional RSS-aided VLP method is invoked for the sake of refining OFDM radar. Our simulation results demonstrate that the proposed VLPC-DCO-OFDM scheme – which simultaneously supports the triple functionalities of illumination, bi-static sensing and communication – is capable of achieving centimeter-level positioning accuracy and Giga-bits-per-second data rate.},

keywords = {Accuracy, Bandwidth, bi-static, Channel estimation, Estimation, Integrated sensing and communication, ISAC, Light emitting diodes, multipath, NLoS, non-line-of-sight, Nonlinear optics, OFDM, Optical sensors, orthogonal frequency-division multiplexing, Radar, Visible Light Communication, visible light positioning, VLC, VLP},

pubstate = {published},

tppubtype = {article}

}

@article{tang_joint_2024,

title = {Joint In-Phase and Quadrature Non-Orthogonal Multiple Access for Multi-User VLC},

author = {Yuru Tang and Chen Chen and Cuiwei He and Bohua Deng and Min Liu and Xinke Tang and H. Y. Fu and Harald Haas},

url = {https://ieeexplore.ieee.org/document/10557663/},

doi = {10.1109/JLT.2024.3414834},

issn = {0733-8724, 1558-2213},

year  = {2024},

date = {2024-10-01},

urldate = {2024-10-30},

journal = {Journal of Lightwave Technology},

volume = {42},

number = {20},

pages = {7219–7228},

keywords = {LRDC, Visible Light Communication},

pubstate = {published},

tppubtype = {article}

}

@article{yoshida_rgbsinglechip_2024,

title = {RGB‐Single‐Chip OLEDs for High‐Speed Visible‐Light Communication by Wavelength‐Division Multiplexing},

author = {Kou Yoshida and Cheng Chen and Harald Haas and Graham A. Turnbull and Ifor D. W. Samuel},

url = {https://onlinelibrary.wiley.com/doi/10.1002/advs.202404576},

doi = {10.1002/advs.202404576},

issn = {2198-3844, 2198-3844},

year  = {2024},

date = {2024-10-01},

urldate = {2024-10-30},

journal = {Advanced Science},

pages = {2404576},

abstract = {Abstract 

 Organic light‐emitting diodes (OLEDs) have been developed for high‐speed transmitters of visible‐light communication (VLC) but so far the possibility of direct fabrication of multiple colors on a single substrate has not been exploited for multi‐Gbps data transmission. Very fast red‐, green‐, and blue (RGB)‐emitting OLEDs are developed on a single substrate to realize high data transmission speed by wavelength division multiplexing (WDM). −6 dB electrical bandwidth of over 100 MHz is achieved for all colors by selecting fluorescent materials with nanosecond emission lifetimes and little overlap between their emission spectra and incorporating them into OLEDs designed for high‐speed operation. Optical microcavities in top‐emitting OLED structures are used to minimize spectral overlap. A record data transmission rate for an OLED transmitter system of 3.2 Gbps is demonstrated, by transmitting data with the 3 colors simultaneously and separating each data by dichroic mirrors. The results show that WDM with integrated RGB pixels is a useful way to increase the data transmission rate of a VLC system based on OLED transmitters, which has the potential to enable multi‐gigabit transmission by displays. The availability of high‐speed multiple‐color devices as developed here also expands applications of OLEDs for spectroscopy, sensing, and ranging.},

keywords = {LRDC, OLEDs, Visible Light Communication},

pubstate = {published},

tppubtype = {article}

}