What is PCI planning in LTE? | PCI Plan steps in Atoll for your LTE Network

What is PCI planning in LTE?
What is the formula for PCI in LTE?

Description: Physical Cell Identity (PCI) is a 16-bit identifier assigned to each cell within a wireless network.

 

Uniqueness: The PCI is used to distinguish one cell from another in the same geographical area. It ensures that neighboring cells have different identities, preventing confusion and interference between them.

 

Assignment: Network planners or optimization tools assign PCI values to each cell during the network planning and configuration phase. These values are typically assigned based on a predefined range and need to be unique within the context of neighboring cells.

 

Role in Handover and Cell Selection: When a mobile device moves through the network, it performs measurements on neighboring cells to decide when to hand over from one cell to another. The PCI is a critical parameter used by the mobile device to identify and select the appropriate neighboring cell during handover.

 

Interference Avoidance: Unique PCIs for neighboring cells help avoid interference between cells operating on the same frequency. This is essential for optimizing the overall performance and capacity of the cellular network.

 

Planning and Optimization: Network planners use PCI planning tools to allocate PCI values to cells in a way that minimizes interference and facilitates efficient handovers.

 

Reconfiguration: In certain situations, such as network expansions or changes, PCI values may need to be reconfigured to maintain optimal network performance.

 

LTE and 5G Networks: PCI is commonly used in LTE networks, and the concept is extended to 5G networks as well. In 5G, there are additional identifiers like NR-PCI (New Radio PCI) used for similar purposes in the NR (New Radio) technology.

 

Proper PCI planning is crucial for the effective functioning of cellular networks, ensuring seamless connectivity and efficient resource management. Network operators and planners use specialized tools, such as Atoll (as mentioned in a previous response), to manage PCI assignments and optimize network performance.

 

There's total 504 physical cell individualities..

These are made up of:

168 cell identity groups with 3 identities each

168×3=504 physical cell identities

PCI =Sub Cell ID + 3 x Cell ID Group

1.   Create your LTE project

In simple two click paste your site / Transmitter data into Atoll. It should include basic information like Site latitude, longitude, antenna, Azimuth, tilts, antenna height and power. At least make sure that the site coordinate, Azimuths and antenna height are correct.

2. Core area Selection

Create the focus zone (core area selection) which is the area we want to plan PCI or change the existing PCI Plan! it is showing in "green color" polygon. Make sure that buffer area (remaining cells) is having an existing PCI plan.

3. Neighbor list planning

To avoid assigning the same PCI plan within neighbors of the cells, it is recommended to create your neighbor plan prior running the PCI Plan.

Below figures illustrate the steps to create the neighbor plan.

An Example of recommended setting is showing below. Hit the button "Calculate" .. the neighbor is calculated as shown in below figure. If happy then, commit the change.

Check quickly the neighbor plan and that can be performed as showing in below figure:

4. Run PCI Planning

Before running the PCI, need to set PSS & SSS ID Status to "Not Allocated".

"Not Allocated" : Any PCI can be modified without any cost.

"Allocated" : the PCI is modifiable only if absolutely necessary.

"Locked" : The PCI not modifiable.

At the Time to run the PCI Plan. Following figure is showing how to do that Settings it will help you to understand.

Mainly and depends on site-to-site distance, the reuse distance can be set accordingly.

In Rural area the PCI reuse distance can be set to higher value.

As the reference Signal (RS) position in the Resource Block (RB) is decided by the output of PCI mod 6, it is good to put some wight for PCI mod 6 and for PCI Mod 30 (UL DMRS).

Also, it is important to check what is the current PCI step used by the operator and if it is fresh PCI planning, I recommend to use PCI Step 8

There are two types of Pci planning steps:

Non-shifted: PCIi mod 6 same for all cells within the site

Shifted: PCIi mod 6 different for all cells within the site

Below are some examples of RS shifted and no shifted scenario:

STEP 1: shifted + same PCI group within site

Example: CI (PSS) = 0,1,2; PCI Group (SSS) = 10

10x3 + 0 = 30

10x3 + 1 = 31

10x3 + 2 = 32

STEP 6: non-shifted + different PCI group within site

Example: CI (PSS) = 1; PCI Group (SSS)= 3,5,7

3x3 + 1 = 10

5x3 + 1 = 16

7x3 + 1 = 22

STEP 8: shifted + different PCI group within site

Example: CI (PSS) = 1,0,2; PCI Group (SSS) = 3,6,8

3x3 + 1 = 10

6x3 + 0 = 18

8x3 + 2 = 26

In PCI Step 1 & 8, the PCI mod 6 is different for all cells within a site.

Basically, in non-shifted RS, the RS in adjacent cells will cause the situation that the RSs will interfere only each other and in shifted RS, the RS will cause interference on PDSCH resource element.

Once all is set, hit the "start" button. the PCI plan will run and changes are showing in blue color. Once completed, "Commit" the change.

5. PCI Plan output check

Use Atoll Audit module to calculate the different collision reuses and the main reuses to be checked is "Physical Cell ID Collision" and the "PCI Mod 6 Collision" with small reuse distance.

Below mention figure was showing an audit report calculated for the same cluster. 

In This example, some cases with PCI Mod 6 collision within 138 m which need to be checked if the sectors are looking to same direction!

 What is PCI planning in LTE?

PCI stands for Physical Cell Identity and is an important parameter used in both LTE (Long-Term Evolution) and 5G (Fifth Generation) cellular networks. It is a unique identifier assigned to each cell within the network to differentiate and distinguish between neighboring cells.

 

What is the formula for PCI in LTE?

it carried by two synchronization signals (PSS&SSS) as PCI=3xSSS+ PSS after UE read these two signals UE can calculate current PCI configuration of the Cell. PCI in LTE is physical layer Cell Identifier. Its range is from 0-503 total Identities as 504. It is consisting of Primary Sync signal and Secondary Sync.