What does carrier or multiple carriers mean in Remote Radio Unit specs?

Question

some RRU specs says it support 8x carrier without MIMO or 4x carriers with MIMO, I do have basic understanding for what is MIMO but I cant warp my head around what carrier mean

In: 1

Answer 1

Radio transmitters work by creating a single constant radio signal at the specific frequency to carry the signal and then modulate this carrier wave with the signal. There are different forms of modulation, amplitude, frequency, phase, etc. but they are all based around a single carrier wave. Using multiple carriers at once means that you can use a wider band then the same modulation on a single carrier. For RRU this means that you can communicate with several single-carrier devices at once or you can combine the bandwidth of multiple carriers to get high transfer rates to other multi-carrier units.