How Phone Signals Work: Do Cell Towers Know Which Phone Belongs to Which

Understanding the intricacies of how phone signals work is both fascinating and essential for anyone concerned with mobile communication. In this article, we explore the inner workings of cell towers, including how they 'know' which phone belongs to which. If you’ve ever wondered about this, you’ve come to the right place.
Do cell towers really recognize which phone belongs to which signal? The answer is an unequivocal yes.

How OFDM Enables Multiple Phone Connections

Cellular carriers utilize advanced technologies to manage multiple connections, and one of the key technologies is OFDM (Orthogonal Frequency Division Multiplexing). OFDM allows carriers to split their frequency spectrum into numerous sub-channels, each allocated to a separate device.
Time division and frequency division are combined in OFDM to maximize the number of sub-channels. This innovative approach ensures that each device can transmit and receive data without interference from others.

The Role of a SIM Card

A SIM card is a crucial component in mobile communication. It allows a device to register on a carrier’s network. When a phone connects to a cell tower, a series of handshaking protocols occurs. The tower instructs the phone on which sub-channel to use. For example, when a phone moves to a new tower, this handshaking takes place again, and the phone is assigned a new sub-channel.
Since all towers are part of the same carrier network, they can effectively track which devices are in communication with which tower, thus determining the best path for call routing.

Cell Towers and Device Identification

Cell towers do not focus on the identity of the phone owner but rather on the phone's cellular account. Each phone is associated with a unique identification number, often stored on the SIM card. This identification number serves as a means for the phone to check in with the nearest cell tower for service. The cell tower then sends this ID to a service center to verify if the account is valid. If the account is active, the phone can establish a connection and display the signal strength.
The International Mobile Subscriber Identity (IMSI) is one of the most crucial numbers on a SIM card. The IMSI uniquely identifies the country, mobile carrier, and subscriber. The cell tower queries the IMSI to determine the services available to this specific phone.

The Importance of IMSI in Mobile Communication

The IMSI is a unique identifier for any mobile device. It comprises two important components: the MCC (Mobile Country Code) and the MNC (Mobile Network Code). The MCC identifies the country where the phone is registered, while the MNC identifies the mobile network. The IMSI, along with other identifiers, helps the cell tower determine the services that can be provided to this phone.

Understanding how phone signals work, including the role of SIM cards and OFDM, provides valuable insights into the seamless and efficient operation of modern mobile communication networks.