LTE RACH SR formula

But if have preamble format zero in LTE your cell radius can be 14 km apart from that it won’t access.
It depends on preamble format.
Also to have max radius defined.

We have expected cell size parameter which defined TA distance.

Definition of cellradius parameter for cell:

“Indicates the radius of the cell, that is, the farthest distance that a cell can cover under the condition of keeping certain network performance. If this parameter is set to a value greater than 100 km, the Extended Cell Access Radius Beyond 100km feature takes effect. Only FDD cells can be configured with a radius more than 100 km. This parameter applies only to LTE FDD and LTE TDD.”

Ok great and new info :+1:

Another preamble format serve high distance.

Never seen such parameter 100 km radius.

We can check preamble format 3gpp, you wil get answers.
For RACH planning.

It’s Huawei approach.
In real life there are no cells of 100 km cellradius.

But if preamble format do whatever it can’t access above that cell radius.

Preamble format is linked with PRACH config index but these defined subframe, radius for RACH preamble.

No point in changing radius more than that.

Yes, there is a point, as users are located 20 km away from eNB.

RACH access depends on preamble format.

True, but if you have users on same cells at 1km, 3km, 5km, 7km, 9km, 11km, 13km, 15km, 17km, 20km… what you gonna do with that cell?
You have to find a value that accommodate all users.
From each of the distance above.

This link clearly mentions of all RACH used to access in preamble format in LTE.


That’s why major overshooters like sea area or remote area can have access issue due to preamble format zero and it is serving behind that point.

You need to use the right preamble format according to distance.

Yes, that’s why I specified the link.

For example chose preamble format 2.

But if set zero and we change cell radius for that no use.

I have seen network in Europe with all cells having cellradius 2000 m.
Such a disaster.
And tilts 0, 1 and 2 degrees.