This Part A considers the situation where a digital fixed link receives interference from radio (natural) noise plus an unwanted interferer of power set at 6 dB above the natural noise. Current fixed link assignment strategies are commonly noise limited. This means that the minimum receiver signal level under fading is set to a particular level with respect to the system noise floor and the ambient noise. The assignments are then planned such that the maximum level of an unwanted signal is set by a protection ratio that results in the unwanted signals typically being approximately 6 dB below the noise. This approach is relatively safe and easy to define, but suffers from being sub-optimum. It is advantageous in maximizing the number of links that can be accommodated in a given band and geographical area to arrange that systems are interference limited. In other words, that the unwanted signals, not natural noise, set the environmental noise floor. Such a strategy brings forth the need to assess the performance of fixed-link receivers in the presence of unwanted signals of other modulation schemes as well as Gaussian noise.
ITU-R REPORT SM.2022-1-2004 history
0000 NF X31-230-1:2013
2004ITU-R REPORT SM.2022-1-2004 The effect on digital communications systems of interference from other modulation schemes