ARFCN (Absolute Radio-Frequency Channel Number)

ARFCN (Absolute Radio-Frequency Channel Number) is a term used in mobile communication systems such as GSM (Global System for Mobile Communications) and UMTS (Universal Mobile Telecommunications System) to identify a specific radio frequency channel. ARFCN is an important parameter in cellular networks as it is used to define the frequency band on which the communication takes place.

In this article, we will discuss ARFCN in detail, including its definition, calculation, and its importance in mobile communication systems.

What is ARFCN?

ARFCN is a unique identifier assigned to each frequency channel in a mobile communication system. It is a standardized numbering system used to identify the frequency of the communication channel. The ARFCN is used in conjunction with other parameters such as BTS (Base Transceiver Station) identity, cell identity, and frequency hopping sequence to ensure that each mobile device is connected to the correct communication channel.

The ARFCN consists of two parts: the first part indicates the frequency band, and the second part indicates the frequency channel within that band. The first part is fixed for a given mobile communication system, while the second part can vary depending on the specific channel used.

For example, in GSM, the first part of the ARFCN indicates the frequency band, with the range from 0 to 1240 used to identify the uplink frequency (mobile device to BTS), and the range from 512 to 885 used to identify the downlink frequency (BTS to mobile device). The second part of the ARFCN indicates the specific frequency channel within that band.

How is ARFCN calculated?

The ARFCN is calculated using a mathematical formula that takes into account the frequency band and the frequency channel within that band. The formula used to calculate the ARFCN varies depending on the mobile communication system used.

In GSM, the formula used to calculate the ARFCN is as follows:

ARFCN = 10 * (N - 1) + F

Where N is the frequency band number, and F is the frequency channel within that band. The frequency band number N ranges from 0 to 124, and the frequency channel F ranges from 0 to 7. The resulting ARFCN ranges from 0 to 1240.

In UMTS, the formula used to calculate the ARFCN is more complex due to the use of frequency bands in both the uplink and downlink channels. The formula is as follows:

ARFCN = 5 * (N - N_offset) + F

Where N is the frequency band number, N_offset is the offset value used to differentiate between uplink and downlink channels, and F is the frequency channel within that band. The resulting ARFCN ranges from 0 to 16383.

Importance of ARFCN in mobile communication systems

ARFCN is an essential parameter in mobile communication systems, as it helps to identify the frequency channel used for communication. It is used to establish a connection between the mobile device and the BTS, ensuring that both devices are communicating on the same frequency channel.

In a cellular network, multiple BTSs may be operating in the same geographic area, each using a different set of frequency channels. The ARFCN is used to ensure that each mobile device is connected to the BTS that provides the best signal quality and coverage in the area.

ARFCN is also used for handover, which is the process of transferring a mobile device from one BTS to another as it moves between cells. During handover, the ARFCN is used to identify the new BTS and frequency channel to which the mobile device should connect.

Finally, ARFCN is also used for frequency hopping, which is a technique used to improve the security and reliability of the communication signal. Frequency hopping involves switching between different frequency channels during a call to reduce the likelihood of interference and eavesdropping. ARFCN is used to determine the sequence of frequency channels to be used during frequency hopping.

Limitations of ARFCN

While ARFCN is an important parameter in mobile communication systems, it does have some limitations. One limitation is that it is only applicable to the specific mobile communication system for which it was designed. For example, the ARFCN used in GSM is not applicable to other mobile communication systems such as CDMA (Code Division Multiple Access) or LTE (Long-Term Evolution).

Another limitation is that the ARFCN does not provide any information about the quality of the signal or the amount of traffic on the frequency channel. Therefore, it is possible for a mobile device to be connected to a frequency channel with poor signal quality or high traffic, resulting in poor call quality or dropped calls.

Conclusion

In conclusion, ARFCN is an important parameter in mobile communication systems that is used to identify the frequency channel used for communication. It is calculated using a mathematical formula that takes into account the frequency band and frequency channel within that band. ARFCN is used to establish a connection between the mobile device and the BTS, ensuring that both devices are communicating on the same frequency channel. It is also used for handover and frequency hopping. While ARFCN has some limitations, it remains an essential parameter in mobile communication systems that enables reliable and secure communication.