Disadvantage of 5G NR option 3A over 3X

Hi All.

Can anyone tell what is the disadvantage of 5G NR option 3A over 3X?

Admin note: this post was updated with image below.

This can help:

I guess Excess load on LTE for option 3A, both SRB and DRB managed by LTE.

In 3X, signalling(SRB) will be done by master node LTE only, data will be split between LTE and NR from secondary node NR.

Data split will be in 3A as well but it will be managed by EPC.

What’s the disadvantage if that splits happen in EPC (3A) or through gNB PDCP (3X)?

How does it matter?

On 3a data spilt you can keep like this:

  • Dldataspilitthreholdinbytes infinity (blocking the data).
  • Dldataprimarypath Secondary cell group.

Where on 3x you can keep like this:

  • Dldataspilitthreholdinbytes (b100/or other value).
  • Dldataprimarypath Secondary cell group.

Why World deployed 3X not 3A?

Robust coverage, peak data rate & good mobility with less latency…

Do we define 3A or 3X anything in RAN side?

The difference is that data going to the EPC is over S1 link which will have latency due to larger distance between site to Core.

But with 3x, the x2 link between 5G and 4G is like an internal short path which gives you the lower latency and low packet losses improving experience.

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We have x2u on 3x also, here gNB carry on most of the traffic and avoids excessive LTE upgradations.

So it’s a EPC configuration or RAN configuration?

Why RAN supplier is saying they don’t support 3A?

In 3A, frequent path switch can happen if NR coverage is not continuously good.

It increases signalling, delay and performance.

  • 3 - hardware issue (MCG - eNB)
  • 3A - SCG (gNB) coverage issue (when TDD is there)
  • 3X - above 2 issues resolved with this option

Thanks… So, these are the disadvantages in 5G NR NSA Architectures Option 3 and 3A which led 3GPP to come up with Option 3X architecture.