UPLINK, DOWNLINK AND OVERALL LINK PERFORMANCE;
INTERSATELLITE LINKS
Uplinks and downlinks consist of radio-frequency modulated carriers, while intersatellite links can be either radio frequency or optical. Carriers are modulated by baseband signals conveying information for communications purposes. Connections between end users entail an uplink and a downlink, and possibly one or several intersatellite links.
The performance of the individual links that participate in the connection between the
end terminals conditions the quality of service (QoS) for the connection between end users, specified in terms of bit error rate (BER) for digital communications. Chapter 4 has shown how the BER conditions the required value of the ratio of the energy per information bit to the power spectral density of noise (Eb/N0) and how this impacts the value of the link performance evaluated as the ratio of the received carrier power, C, to the noise power spectral density, N0, quoted as the ratio C=N0, expressed in hertz (Hz). This chapter discusses the parameters that impact link performance C/N0 and provides the means to evaluate the performance of an individual link given the transmit and receive equipment in the link or to dimension the transmit and receive equipment in order to achieve a given link performance.
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COMUNICACIONES SATELITALES
En términos astronómicos, un satélite es un cuerpo celeste que gira en órbita en torno a un planeta (por ejemplo, la Luna es un satélite de la Tierra). Sin embargo, en términos aeroespaciales un satélite es un vehículo espacial lanzado por humanos, que describe órbitas alrededor de la Tierra o de otro cuerpo celeste. Los satélites de comunicaciones son fabricados por el hombre y giran en órbita en torno a la Tierra, permitiendo efectuar una multitud de comunicaciones hacia una gran variedad de consumidores, incluyendo suscriptores militares, gubernamentales, privados y comerciales. …
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