Glossary  >  Physical Cell ID (PCI)

Physical Cell ID (PCI)

Physical Cell ID (PCI)


Physical Cell ID (PCI) is a physical layer cell identifier in 4G LTE and 5G NR used to indicate the physical identity of a cell during the cell selection procedure. PCI is used for downlink synchronization.

This makes PCI planning one of the most important steps in 4G LTE and 5G NR network design and construction. A well-designed and executed PCI will increase resource utilization and quality of service for mobile subscribers.

On the other hand, poor PCI planning and execution will result in conflicts, which will negatively impact the network.

PCI consists of two parts, the Primary Synchronization Signal (PSS) and Secondary Synchronization Signal (SSS), and can be determined using the formula:

PCI = (3 x SSS) + PSS

In 4G LTE:

PSS can be one of three values between 0 and 2. This value is generated using the Zadoff-Chu sequence.

SSS has a total of 168 values, which means the value can be any number between 0 and 167, generated using a concatenation of 2 m-sequences.

For example, after successfully decoding SSS to be 167 and PSS to be 2, then PCI can be determined as:

PCI = (3 x 167) + 2 = 503

Note: 4G LTE supports a total of 504 unique PCIs whose values range between 0 and 503.

In 5G NR:

PSS can be one of three values between 0 and 2, the same as with 4G LTE. This value is generated using an m-sequence.

SSS has a total of 336 values ranging between 0 and 335. The SSS value here is determined using the PN Gold sequence.

Calculating the PCI in 5G NR follows the same formula as with 4G LTE. Therefore:

If given that SSS is 355 and PSS is 2:

PCI = (3 x 355) + 2 = 1007

Note: 5G NR supports a total of 1008 unique PCIs ranging from 0 to 1007. This means 5G NR supports twice as many PCIs as 4G LTE.

Example of Physical Cell ID in a sentence

"Physical Cell ID is a unique identifier similar in its role to the Primary Scrambling Code of UMTS cells."

Synonyms: PHY-layer cell ID

Related Terms for Physical Cell ID