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Publication
Sistema de transmissão de áudio digital
| Name: | Description: | Size: | Format: | |
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| 4.32 MB | Adobe PDF |
Authors
Advisor(s)
Abstract(s)
O presente trabalho pretende abordar a transmissão sem fios de áudio
digital, assentando em dois objetivos primordiais: o apoio a pessoas em locais
sem cobertura de redes GSM (Global System for Mobile) e a monitorização
remota de fenómenos acústicos ambientais.
Desenvolveram-se protótipos para comunicação bidirecional, difusão de
mensagens gravadas e transmissão de mensagens em diferido para uso em
locais remotos sem acesso à rede GSM ou com acesso vedado ou condicionado
por condições extremas (nomeadamente catástrofes naturais, incêndios e
acidentes com elevado grau de destruição).
Um outro aspeto desenvolvido foi a gravação de áudio em alta qualidade
12 bits e 44,1 kHz (com vista a recolher informação acústica em locais remotos),
recorrendo a protótipos com cartão de memória e ao posterior envio para um
recetor.
Foram testados vários cenários de propagação em ambiente real, para os
diferentes tipos de protótipos em causa. Para os sistemas de qualidade voz, em
condições normais, obteve-se uma ligação bem-sucedida a cerca de 2 km de
distância.
Para os protótipos de gravação e transmissão de alta qualidade, os
resultados foram igualmente satisfatórios, com uma baixa taxa de erro e áudio
sem alterações.
Inicialmente foi estudado o componente rádio nRF24L01+, como
módulo integrado com Arduíno. Em seguida, foi equacionado o XBee, como
potencial rádio alternativo. Foi escolhido o primeiro pelo facto de este
componente permitir um débito máximo de transmissão de 2 Mbps, acesso ao
meio com latência reduzida e o seu alegado baixo consumo de energia.
The present work aims to address the wireless transmission of digital audio, based on two main objectives: the emergency support to people in places without coverage of GSM networks (Global System for Mobile)) and the remote monitoring of environmental acoustic phenomena. Prototypes have been developed for two-way communication, broadcasting of recorded messages and transmission of deferred messages for use in remote locations without access to the GSM network or with access sealed or conditioned by extreme conditions (namely natural disasters, fires and accidents with a high degree of destruction). Another aspect developed was the recording of audio in high quality 12 bits and 44.1 kHz (with the goal to collecting acoustic information in remote locations), using prototypes with memory card and subsequent sending to a receiver. Several propagation scenarios were tested in real environment for the different types of prototypes concerned. For voice quality systems, under normal conditions, a successful connection was obtained about 2 km away. For high-quality recording and transmission prototypes, the results were equally satisfactory, with a low error rate and unchanged audio. Initially, the radio component nRF24L01++was studied as an integrated module with Arduino. XBee was then considered as an alternative radio potential. The first was chosen because this component allows a maximum transmission throughput of 2 Mbps, access to the medium with reduced latency and its alleged low power consumption.
The present work aims to address the wireless transmission of digital audio, based on two main objectives: the emergency support to people in places without coverage of GSM networks (Global System for Mobile)) and the remote monitoring of environmental acoustic phenomena. Prototypes have been developed for two-way communication, broadcasting of recorded messages and transmission of deferred messages for use in remote locations without access to the GSM network or with access sealed or conditioned by extreme conditions (namely natural disasters, fires and accidents with a high degree of destruction). Another aspect developed was the recording of audio in high quality 12 bits and 44.1 kHz (with the goal to collecting acoustic information in remote locations), using prototypes with memory card and subsequent sending to a receiver. Several propagation scenarios were tested in real environment for the different types of prototypes concerned. For voice quality systems, under normal conditions, a successful connection was obtained about 2 km away. For high-quality recording and transmission prototypes, the results were equally satisfactory, with a low error rate and unchanged audio. Initially, the radio component nRF24L01++was studied as an integrated module with Arduino. XBee was then considered as an alternative radio potential. The first was chosen because this component allows a maximum transmission throughput of 2 Mbps, access to the medium with reduced latency and its alleged low power consumption.
Description
Keywords
Sistema de transmissão Auxílio Monitorização Transmissão digital Redes multimédia nRF24L01+ Transmission system Assistance Monitoring Digital transmission Multimedia networks Engenharia Eletrotécnica - Telecomunicações . Faculdade de Ciências Exatas e da Engenharia