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Melhoria da eficiência de comunicação HF utilizando algoritmos de seleção de débito binário evoluidos
| Name: | Description: | Size: | Format: | |
|---|---|---|---|---|
| 4.48 MB | Adobe PDF | |||
| 4.47 MB | Adobe PDF |
Advisor(s)
Abstract(s)
As comunicações na banda das altas frequências (HF) têm evoluído tecnologicamente,
desde o final dos anos 80, sendo esta evolução motivada pela potencial robustez desta forma
de comunicação em situações de catástrofe e de emergência, e pelo custo de manutenção e
implementação das comunicações via satélite. Apesar do reaparecimento do interesse nas
comunicações HF, existem vários desafios envolvidos, como a operação rádio com relações
sinal-ruido (SNR) tipicamente muito baixas e variação do sinal devido a mudanças frequentes
na camada da Ionosfera. Para lidar com as variações do canal em HF, surgiram várias
tecnologias como os algoritmos de seleção automática do débito binário (DRC). As soluções
existentes (Trinder e RapidM) foram estudadas, e com base nas vulnerabilidades detetadas,
foram propostas versões melhoradas de ambos os algoritmos: Avoiding Cut-Off State (ACOS)
e Bit Error Optimization (BEO). A primeira proposta reduz o número de ocorrências de corte
na ligação (correspondente a taxas de erro de bit superiores a 10-3) e a segunda aumenta a
disponibilidade da ligação e elimina as oscilações de débito binário. Quando comparadas
com as versões originais, ambas as propostas demonstram melhores desempenhos, seja num
sistema de simulação ou em condições reais de propagação.
High frequency (HF) band communications have undergone a remarkable technologic evolution, since the 80s, motivated by their potential robustness to catastrophic and emergency situations, and by the high costs involved in implementing and maintaining satellite links. Despite the renewed interest on HF communications, there are a lot of challenges involved, like the operation with very low signal-to-noise ratios (SNR) and signal variation due to the frequent changes in the Ionosphere constitution. In order to deal with the variability of the HF channel, several technologies have emerged like the Data Rate Change (DRC) algorithms. Former DRC algorithms solutions were studied (Trinder and RapidM), and based on their vulnerabilities, improved versions were proposed for both algorithms: Avoiding Cut-Off State (ACOS) and Bit Error Optimization (BEO). The first proposal reduces the occurrences of link cut-offs (corresponding to bit error rates higher than 10-3), and the second increases the link availability and eliminates data rate oscillations. When compared to the original versions of the algorithms, both proposals showed significant performance improvements, either when evaluated in a simulation environment, or in real field propagation tests.
High frequency (HF) band communications have undergone a remarkable technologic evolution, since the 80s, motivated by their potential robustness to catastrophic and emergency situations, and by the high costs involved in implementing and maintaining satellite links. Despite the renewed interest on HF communications, there are a lot of challenges involved, like the operation with very low signal-to-noise ratios (SNR) and signal variation due to the frequent changes in the Ionosphere constitution. In order to deal with the variability of the HF channel, several technologies have emerged like the Data Rate Change (DRC) algorithms. Former DRC algorithms solutions were studied (Trinder and RapidM), and based on their vulnerabilities, improved versions were proposed for both algorithms: Avoiding Cut-Off State (ACOS) and Bit Error Optimization (BEO). The first proposal reduces the occurrences of link cut-offs (corresponding to bit error rates higher than 10-3), and the second increases the link availability and eliminates data rate oscillations. When compared to the original versions of the algorithms, both proposals showed significant performance improvements, either when evaluated in a simulation environment, or in real field propagation tests.
Description
Keywords
Algoritmos de seleção de débito binário Comunicações em HF Comunicações via Ionosfera Comunicações via Satélite Data rate change algorithms HF Communications Ionosphere communications Satellite communications