My friend: Hi Ibrahim, I have a question for you.
- Me: Please, go ahead.
My friend: I was wondering if we are going to design an Open RAN network using 5G, which DU can we use, centralized DU or distributed DU?
- Me: Actually, it depends on which services you are targeting to provide at this network. For example, if you need to apply URLLC use case, so you have to use distributed DU, where the DU is located at the cell site with the RU, while if only eMBB use case is required, then you can go for centralized DU where the DU is located far from the cell site, for example at the Edge cloud. But if both use cases are required, then distributed DU can be used to support both services together.
My friend: So, latency is the only factor to determine the DU location?
- Me: No, latency is only one of the factors you have, but there are other factors that you should consider as well. One of them is the transmission capacity for the fronthaul interface between the RU and the DU, so if the fronthaul design reveals that you need a capacity of 50Gbps at the fronthaul interface for one 5G site including multiple 5G carriers and the MNO has fiber links with capacity around 20Gbps only and there is no room for transmission upgrade as per the current situation, that means simply we can’t use centralized DU and we have to go for distributed DU. And of course, if the transmission capacity is enough, then we have the flexibility to go for the centralized DU.
My friend: I got these two points now
- Me: That’s great, however there is one point as well that is very important which is the distance between the RU location at the cell site and the DU location assuming for example that the DU will be located at the Edge cloud. As if this distance is 30Km, for instance, then we can’t use centralized DU and we have to go for distributed DU as fronthaul distance shouldn’t be high otherwise no signal can be detected at both sides, the RU and the DU.
My friend: Thank you so much. You made it very clear.
- Me: You are most welcome.