Análise de eficiência energética de redes cooperativas em ambientes subaquáticos utilizando codificação de rede e OFDMA

Abstract

Underwater Acoustic Networks (UWANs) are used to collect data and to monitor various types of applications, from the offshore industry to military installations. Similarly to terrestrial wireless sensor networks, it is also possible to explore the broadcast nature of the wireless channel and employ the concept of cooperative communications in order to combate the fading. In a cooperative network, nodes help each other by relaying the information broadcasted by their partners. However, more than just increasing reliability, one must also expend efforts towards increasing the network lifetime, since it is not desirable to oftenly reaplace the batteries of the wireless nodes. Thus, in this work we adopt the energy efficiency (in Joules/bit) as performance metric to evaluate some network-coded cooperative (NCC) protocols. More specifically, it is considered a scenario where the multiple access is performed by means of subcarrier allocation-aided OFDMA, extending the results of a recently proposed NCC-OFDMA scheme. In the proposed scheme, referred to as generalized dynamic network coding (GDNC)-OFDMA, more than just achieving diversity from time domain, it is shown that the diversity order can be increased even further, by relaxing a constraint imposed to the NCC-OFDMA scheme that only a set of nodes is able to transmit redundant information. The results of this work, which encompasses mathematical analysis supported by computer simulations, adopt real acoustic modems parameters, show that the proposed GDNC-OFDMA scheme is capable of present improved energy efficiency in several practical scenarios.