Adequação ao requisito cintilação em sistemas de comunicação via luz visível mediante uso de sinais OFDM com envoltória constante

• Autor(a) principal: Neves, José Luís Costa
• Data de Publicação: 2018
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Espírito Santo (riUfes)
• Texto Completo: http://repositorio.ufes.br/handle/10/10709
• topic: Comunicação via luz visível (VLC); Cintilação luminosa (Flicker); Relação entre potência de pico e potência média (PAPR); Sinais com envoltoria constante; Engenharia Elétrica; Multiplexação ortogonal por divisão de frequência; 621.3

The scarcity of electromagnetic spectrum has been a problem in the development of new wireless applications. To solve this problem, visible light communication has emerged as a promising and complementary technology to radiofrequency due to its advantages such as green technology, unlicensed spectrum, low power consumption, high privacy protection and resistance to electromagnetic interference . Allied to this, because it is a technology that uses light emitting diodes for data transmission, also guaranteeing the lighting function, it allows its use in di erent types of environments. Orthogonal frequency division multiplexing (OFDM) in visible light communication systems has been attractive because of its ability to combat intersymbol interference and ensuring high data rates. However, OFDM signals have large amplitude uctuations, resulting in high peak-to-average power ratio (PAPR) and therefore can degrade the quality of the illumination due to Flicker light. Flickering light is harmful to vision and causes eye fatigue, seizures, headache, malaise, and other problems. The present work presents a simulation and experimental study that evaluates the performance of the OFDM transmission technique that transmits signals with constant envelope (CE-OFDM) in a communication system via visible light, by means of the adequacy of the Flickering requirements. The CE-OFDM system is based on the phase modulation of an electric carrier and reduces the PAPR parameter to 3 dB. The results obtained in the line-of-sight channel using a bandwidth of 5 MHz showed that, by adapting the icker requirements and considering the mapping levels 4, 16 and 64-QAM, the CE-OFDM system presents a upper performance than those presented by the conventional OFDM and ACO-OFDM systems. The results also showed that, in the presence of non-linearities introduced by the LED, the CE-OFDM system presents greater robustness.