Spectrum Efficiency Metrics

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Broadcast systems vs. point-to-point systems, in which broadcast systems are intended to distribute identical content from one origination point to many reception points, while point-to-point systems are intended to establish many individual communication links between two points (senders and receivers).

  • Fixed service vs. mobile service, in which a fixed service uses a stationary high gain antenna that requires precise pointing to the satellite, while a mobile service allows user mobility through the use of an omni-directional antenna that does not require pointing.

    An additional distinction that will be useful for metric definition is geostationary vs. non-geostationary satellite system, which specifies whether or not the satellite operates in an orbit that is geostationary. While this distinction is more of a system architecture characteristic as opposed to a service type, it does affect the amount of spectrum re-use that can be achieved between different satellite systems, so it therefore influences how spectrum efficiency is determined.

    Within each service type, an appropriate spectrum efficiency metric will be proposed. As a consequence of the system design tradeoffs in satellite systems, it is sometimes possible to improve a spectrum efficiency metric by making a change within the system design that degrades a value point for the end user. For example, spectrum efficiency in terms of bits-per-second-per Hz of spectrum can be increased by increasing the size (antenna aperture diameter) of the user antenna, which enables higher order modulation to be employed. Larger antenna sizes, however, are generally undesirable, especially in consumer applications. It is therefore useful to identify additional efficiency considerations that will need to be evaluated along with the core spectrum efficiency metric to provide an overall evaluation of the spectrum efficiency so that the stand alone spectrum efficiency metric does not drive an undesirable satellite system design.

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