narrow band (NB)

Narrowband refers to services that are transmitted in a limited frequency band. The term is therefore used equally for services and frequency bands and is interpreted differently in different contexts.

As far as services are concerned, it is narrowband if the services can be transmitted over a limited frequency band. Long-distance telephony over a bandwidth of 3.1 kHz is one such example; shortwave broadcasting and CB radio, which use channel grids of 5 kHz and 10 kHz, are others. To evaluate a narrowband service, the bandwidth required for the service can be related to the available transmission bandwidth. Whereby the frequency response is to be considered flat.

There are definitions of narrowband from the International Telecommunication Union( ITU) and the CCITT. According to these, the frequency range for narrowband extends up to 2 Mbit/s. This is more or less what CCITT specifies. For them, narrowband is below the primary multiplex data rate, which is 2.048 Mbit/s in Europe and 1.544 Mbit/s in the USA.