Data transmitted from network towers to cell phones can be detected by all devices within range, but encryption typically prevents eavesdropping on individual conversations. Technologies like Code-Division Multiple Access (CDMA) and Time-Division Multiple Access (TDMA) facilitate multiple simultaneous communications. While microwaves and millimeter waves can be directed, targeting a single device is impractical and does not enhance security compared to encrypted broadcasts. Antennas are designed with specific gain patterns to focus radio frequency energy in certain directions, allowing for effective communication over larger areas. The concept of steering signals using phased array antennas is noted for its efficiency, though practical challenges exist in integrating multiple antennas into handheld devices.
