Multi-coded Variable PPM for High Data Rate Visible Light Communications

A novel color clustered optical RGB multiple-input multiple-output (MIMO) system is presented. As visible light can be divided into three primary regions of red, green and blue, data can be modulated and transmitted separately using these three color clusters. Each color cluster comprised of 30 RGB LEDs is modulated using on-off-keying (OOK), and selection combining is performed at the receiver, producing a diversity effect within that color cluster. The simulations demonstrate that the proposed RGB MIMO VLC system provides high performance via a relatively simple design of MIMO. Moreover, the proposed system ensures sufficient illumination from LEDs and offers extended distance if more LEDs are applied.

Section: Introductionmentioning

confidence: 99%

Color Clustered Multiple-input Multiple-output Visible Light Communication

Han

Sewaiwar

Tiwari

et al. 2015

“…However, it is ineffective to strike the load balance using just hardware with the average optical flow at each wavelength for each port in such works. Meanwhile, the key components such as tunable wavelength converters are still costly or immature for practical deployment [18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Dynamic Load-Balancing Algorithm Incorporating Flow Distributions and Service Levels for an AOPS Node

Zhang¹,

Xu²,

Sun³

2014

An asynchronous optical packet-switching (AOPS) node with load-balancing capability can achieve better performance in reducing the high packet-loss ratio (PLR) and time delay caused by unbalanced traffic. This paper proposes a novel dynamic load-balancing algorithm for an AOPS node with limited buffer and without wavelength converters, and considering the data flow distribution and service levels. By calculating the occupancy state of the output ports, load state of the input ports, and priorities for data flow, the traffic is balanced accordingly. Simulations demonstrate that asynchronous variant data packets and output traffic can be automatically balanced according to service levels and the data flow distribution. A PLR of less than 0.01% can be achieved, as well as an average time delay of less than 0.46 ns.

“…Pulse dual-slope modulation [28], which is a variant of VPPM, offers improved flicker mitigation. Multicoded VPPM [29] adopts cyclic M-ary PPM for higher rates. Time-multiplexed OOK [26,30] was developed to insert an ON or OFF time period without adaptive control of the mean optical power.…”

Section: Introductionmentioning

confidence: 99%

Optimal Signal Amplitude of Orthogonal Frequency-Division Multiplexing Systems in Dimmable Visible Light Communications

Yun

Lee

Ahn

et al. 2014

Visible light communications (VLC) using the intensity modulation of light-emitting diodes (LEDs) provides a new communication medium to overcome the shortage of radio spectrum, and allows reuse of LED lighting infrastructures. Orthogonal frequency-division multiplexing (OFDM) was introduced to VLC for its merits in mitigating the fading effects resulting from delay spread, and in avoiding low-frequency ambient interference. Noise and clipping are two major factors that degrade the performance of OFDM in VLC. A larger signal easily overcomes noise, but experiences impairment by clipping. Therefore, degradation due to clipping has a trade-off relationship with that due to noise, depending on the signal amplitude of OFDM. In this paper, the optimal signal amplitude in the trade-off is obtained by simulation when the dimming and LED intensity are given. The former indicates a user's requirement for lighting, and the latter represents the channel quality. The required LED intensity-to-noise ratio, as the channel quality that guarantees dimming as well as an adequate bit-error rate (BER), is also discussed.