ceived signal power. This can be referred to relatively constant, regardless of Y. For a given noise as power-limited operation (in contrast to bandwidth- power density, any increase of the information data rate limited operation, see below) as, in this case, an in- then implies a similar relative increase in the minimum crease in the available bandwidth does not substan- required signal power S = Eb.R at the receiver. On the tially impact what received signal power is required other hand, for bandwidth utilizations larger than one the for a certain data rate. minimum required, Eb/No increases rapidly with Y. On the other hand, in case of high-bandwidth utiliza- Thus, in case of data rates in the same order as or larger tion, i.e. in case of data rates in the same order as or than the communication bandwidth, any further increase exceeding the available bandwidth, any further in- of the information data rate, without a corresponding crease in the data rate requires a much larger relative increase in the available bandwidth, implies a larger, increase in the received signal power unless the eventually much larger, relative increase in the minimum bandwidth is increased in proportion to the increase in required received signal power. data rate. This can be referred to bandwidth-limited operation as, in this case, an increase in the bandwidth 4.3.1.1 High data rates in will reduce the received signal power required for a certain data rate. noise-limited scenarios From the discussion above, some basic conclusions can be Thus, to make efficient use of the available received signal drawn regarding the provisioning of higher data rates in power or, in the general case, the available signal-to-noise ratio, the transmission bandwidth should at least be of the a mobile-communication system when noise is the main source of radio-link impairment (anoise-limited scenario): same order as the data rates to be provided. Assuming a constant transmit power, the received signal power can always be increased by reducing the The data