Hongming Yang

Full-duplex relay VLC in LED lighting triangular system topology

Visible light communications (VLC), in terms of luminaire-to-luminaire communications, can play an important role in a wide range of applications in indoor light emitting diode (LED) lighting systems. One of the main challenges in such VLC systems though is the limited range of reliable communications. In order to enhance the VLC range without compromising the network throughput, we consider full-duplex relay VLC in a general triangular topology under amplify-and-forward and decode-and-forward processing at the relay luminaire. We analyze the system performance in terms of bit error rate (BER) and show that multiple orders of magnitude improvement in BER is achieved as compared to direct link VLC under practical indoor conditions.

Full-duplex relay VLC in LED lighting linear system topology

Visible light communications (VLC) with light emitting diodes (LEDs) and photodiodes enables a wide range of applications in LED lighting systems. One of the main challenges in VLC is the limited range of reliable communications, owing mainly to the non-coherent nature of optical communications and limited output power of LED luminaires. In order to enhance VLC range without compromising the network throughput, we consider full-duplex relay VLC. Specifically, we consider a basic 3-luminaire (source, relay and destination) linear system topology under amplify-and-forward and decode-and-forward processing at the relay luminaire. Due to full-duplex operation at the relay luminaire, a self-interference signal component arises and is subsequently canceled out as part of the relay processing. We analyze the system performance in terms of bit error rate (BER) and show that multiple orders of magnitude improvement in BER is achieved as compared to direct link VLC under practical indoor conditions.

Disaggregated Daylight–Artificial Light Sensing

Control of lighting systems that adapt to daylight is known to be energy efficient. An underlying challenge in such control is the estimation of daylight level. We consider the problem of disaggregated estimation of the daylight and artificial light levels in a lighting system. To facilitate this disaggregation, the light output from each light source is modulated and the system operates under a carrier sense multiple access with collision avoidance protocol. At the light sensor, the received electrical signal is a superposition of the light contributions from daylight and artificial light sources. We present algorithms to process the sensor signal to estimate the daylight and artificial light levels. An optimum joint least-squares estimator is analyzed and, subsequently, two practical successive estimation algorithms are proposed. The performance of these algorithms is evaluated analytically and validated via experimental results.