Q and A, What is E1 interface in 5G?

 What is E1 interface in 5G?

My friend: Hi Ibrahim, I have a question for you.

Me: Please, go ahead.

My friend: What is the function of E1 interface in 5G?

Me: The E1 interface connects the Centralized Unit Control Plane (CU-CP) to the Centralized Unit User Plane (CU-UP) in the case of CU splitting which is done mainly to optimize the location of different RAN functions according to different scenarios and performance requirements, so the CU can be further separated into its CP and UP parts.

My friend: So, E1 interface is carrying data and control information between CU-CP and CU-UP, right?

Me: No, it is only carrying control information to allow for the coordination between user plane and control plane functions in the CU as normally the user plane information will be directed from CU-UP towards the UPF via NG-U interface. Also, note that as per 3GPP 38.460, the E1 interface should be an open interface that allows for CU separation to happen between different vendors.

My friend: Thank you very much. You made it clear.

Me: You are most welcome

From Ibrahim Sayed
URL = https://www.linkedin.com/in/ibrahim-sayed-88a7747-5g/ 

Is 5G protocol stack different from 4G?

 Is 5G protocol stack different from 4G?

My friend: Hi Ibrahim, I have a question for you.

Me: Please, go ahead.

My friend: Is there any difference between 4G and 5G protocol stack?

Me: Yes, they are different slightly. If you checked the protocol stack of the 5G control plane, you can find similar layers to the 4G control plane, however the protocol stack of the 5G user plane has an extra layer which is SDAP (Service Data Adaptation Protocol) which is used to map each QoS flow into a specific Data Radio Bearer (DRB) as QoS flow is a new concept introduced in 5G and was not available in 4G before.

My friend: So, same layers with same functions, right?

Me: No, it doesn’t mean same layers for 4G and 5G, that same functions are exist for both layers. For example, the PDCP layer in 5G has different functions than 4G such as in 5G, PDCP layer can do PDCP PDU routing for the so called split bearers in case of operating in dual connectivity mode and split bearer concept is not there in 4G, also RRC layer in 5G is responsible for on-demand system information and also RRC inactive state which are new concepts in 5G.

My friend: Thank you very much.

Me: You are most welcome.

From Ibrahim Sayed
URL = https://www.linkedin.com/in/ibrahim-sayed-88a7747-5g/ 

 

Q and A, Is mobility in 5G different from 4G?

 Is mobility in 5G different from 4G?

My friend: Hi Ibrahim, I have a question for you.

Me: Please, go ahead.

My friend: I was wondering if mobility in 5G differs from 4G or they are the same?

Me: Actually, it is different little a bit.

My friend: But, how are they different?

Me: In 4G we have mainly mobility between cells, while in 5G we’ve mobility between cells and beams which is called beam switching as well. So, both the 5G BTS and UE must be capable of changing beams as the radio conditions change.

My friend: But, how beam and cell mobility are done in 5G?

Me: Beam switching is done inside each cell which is called intra-cell mobility which requires layer 1 and layer 2 procedures. While, mobility between cells or what is called inter-cell mobility involves a handover which requires layer 3 procedures. Cell level measurements can be the average of different beams measurement or the value of the strongest beam depending on the algorithm used by each vendor.

My friend: Thanks a lot. You made it clear.

Me: You are most welcome.

From Ibrahim Sayed
URL = https://www.linkedin.com/in/ibrahim-sayed-88a7747-5g/