What is LTE Rach procedure?

Random Access Procedure:- In order to be synchronized with the network, RACH procedure is used. Suppose a UE wants to access the network, so first it will try to attach or syncronise with the network. In LTE a separate channel PRACH ( Physical Random Access Channel) is provided for initial access to the network.

Why Rach is used in LTE?

Machine-to-machine communication (M2M) is a technology to provide interaction among network devices without human intervention. Due to infrastructure characteristics, LTE networks are highly expected to become the deployment network of M2M devices.

What is difference between PRACH and Rach?

RACH is transport-layer channel; the corresponding physical-layer channel is PRACH.

How many types of Rach are there?

Two types of RACH : Contention Based and NonContention Based In each LTE cell, total 64 preamble signatures are available and UE select randomly one of these signatures.

What is RACH root sequence?

The RACH Root. Sequence index indicates the first root sequence number that is to be used by. a UE for preamble generation. 25. This formula is applicable when Ncs unrestricted set and preamble format.

What happens when RACH fail?

The selected RACH Preamble is transmitted. A RACH Response (RAR) with respect to the RACH Preamble transmitted in step 1) is received. If the RACH Response reception fails, the Preamble Transmission counter value is increased by 1, and a back-off time is applied if necessary, and the process returns back to step 1).

What happens when Rach fail?

What is Rach root sequence?

What is contention based RACH in LTE?

It means the same PRACH preamble from multipe UE reaches the NW at the same time.. this kind of PRACH collision is called “Contention” and the RACH process that allows this type of “Contention” is called “Contention based” RACH Process.

What is RACH optimization?

The automatic RACH optimization function automates the required continuous adaptation of the RACH. The automatic RACH optimization function can automatically react when receiving notification over X2 of a RACH parameter change in a neighboring cell.

What is Rach preamble in LTE?

How the information is encoded into PRACH (RACH Preamble)? In LTE, all the information (data) after PRACH Preamble has its own binary structure meaning that they are translated into a certain data structure. However, the information in PRACH Preamble is represented by purely physical properties.

How important is the Rach design in networking?

Even in terms of protocol design, RACH design can be one of the most important / critical portions. If you have any experience of testing UE or UE modem chipset at the very early stage of the development, you would have noticed that RACH is the most challenging point in terms of troubleshooting.

How to initiate Rach procedure?

To initiate RACH procedure, UE will send RACH request after it receives request from UE RRC. How many types of RACH procedure are there? There are 2 types of RACH procedure.

When a UE is supposed to send Rach?

It shows exactly when a UE is supposed to send RACH depending on a parameter called “PRACH Configuration Index”. For example, if the UE is using “PRACH Configuration Idex 0”, it should transmit the RACH only in EVEN number SFN (System Frame Number).

How does ENB determine when UE will transmit the Rach?

The answer is ‘eNB determines it via prach-Configindex IE in SIB2’. Refer to prach-ConfigIndex section for the details. How does Network knows exactly when UE will transmit the RACH?