Thursday, 16 June 2022

What is a Multi-Band Cell?

Multi-band cells became very popular in modern RAN environment and beside many benefits they also come with some challenges for performance measurement and radio network optimization.

A multi-band cell consists of a default band that shall be used by UEs for initial cell selection and a set of additional frequency band carriers that typically become involved as soon as a dedicated radio bearer (DRB) for payload transmission is established in the radio connection.

The exact configuration of a multi-band cell including all available frequency bands is broadcasted in SIB 1 as shown in the example below.

Different from legacy RAN deployments where – to take the example of a LTE cell – a pair of PCI/eARFCN (Physical Cell Identity/eUTRAN Absolute Radio Frequency Number) always matches a particular ECGI (eUTRAN Cell Global Identity) the multi-band cell has many different PCI/eARFCN combinations belonging to a single ECGI as you can see in the next figure.

Now performance measurement (PM) counters for e.g. call drops are typically counted on the cell ID (ECGI) and thus, in case of mulit-band cells do not reveal on which frequency a radio link failure occurred.

However, knowing the frequency is essential to optimize the radio network and minimize connectivity problems. More detailed information must be collected to find out which of the different frequency bands performs well and which need improvement.

This becomes even more interesting if multi-band cells are used in MORAN RAN sharing scenarios.

In my next blog post I will have a closer look at this special deployment.

3 comments:

Anonymous said...

How different from Multiple bandwidth part in 5G if we extend it to different frequency?

Ralf Kreher said...

BW Part in 5G is used to address spectrum of single cell that is all in the same NR frequency band.

The example described in the blog post is plain LTE where no BWP exists and from the physical (radio) layer perspective it is rather similar to a scenario where 3 physical cells with completely different frequency bands are used.

Anonymous said...

You mentioned in second figure in SINGLE BAND CELL different eARFCN value with different PCI !!?? That’s mean it’s multi band cell not single band!? Any correction?! If it is correct so please could you elaborate it