During the pandemic many people stayed at home, and activities like gaming, video streaming, online shopping, and food delivery all rely on the mobile phone. Sometimes mobile data is intermittent, web pages fail to load, or videos and games stutter. What causes weak mobile signals, and what factors determine signal strength?
The signal bars shown on a phone are not calculated by a unified standard. Different brands, and even different models from the same brand, can display different signal bar counts.
Mobile phones use a dedicated baseband chipset to encode and decode radio signals. In simple terms the baseband chipset acts as a "translator"; if this translator is inefficient, the phone may exhibit weaker signal performance.
As distance from a base station increases, received signal strength drops and the phone must increase its transmit power to receive high-quality signals. Similarly, for a base station to receive a phone's uplink, the phone must transmit at higher power when distant, which can lead to reduced performance and perceived lag.
Electromagnetic waves propagate in directions controlled by the antenna. Obstacles that block or attenuate electromagnetic waves, such as metal bodies of cars or trains, or certain types of building glass, reduce signal strength. In basements or elevators, or at the edge of obstacles where diffraction is limited, a phone may lose signal entirely.
The cellular mobile communication network divides a wide area into many small cells, each served by a base station responsible for user terminals within that cell. This enables users to communicate while moving, with handover and roaming functions. Each cell's coverage is mainly determined by the antenna's azimuth and downtilt.
Antenna azimuth
The azimuth angle is measured clockwise from north to the plane of the antenna, ranging from 0° to 360° (north=0°, east=90°, south=180°, west=270°). Antennas are either omnidirectional or directional; most base stations use directional antennas. A typical base station uses three antennas, each covering 120° to achieve 360° coverage. For example, if an antenna azimuth is 60°, its coverage spans 0° to 120°, with the main lobe centered roughly between 30° and 90° and side lobes outside that range. If you are located within the main lobe, the signal will be stronger; if you are in a side lobe, the signal will be relatively weaker.
Antenna downtilt
Downtilt, also called tilt or elevation angle, indicates the antenna's vertical angle. A larger downtilt results in nearer coverage; a smaller downtilt extends coverage farther. Downtilt settings vary based on installation environment and user distribution. If an antenna has very little downtilt and radiates nearly horizontally, signal strength near the tower can be poor, a phenomenon sometimes referred to as a "coverage hole" under the tower.
In summary, mobile signal strength is closely related to terrain and environment, network coverage design, baseband chipset performance, base station transmit power, propagation obstacles, and antenna installation. Different networks and cells use different radio frequencies and therefore have different propagation characteristics. When a phone has no signal, it may be because the base station's service area is limited and the signal weakens with distance. If you are located in a base station's coverage blind spot, the signal will be relatively weak.
Check mobile signal strength
The standard metric for measuring mobile signal strength is RSRP (Reference Signal Received Power). Signal power is expressed in dBm, typically in the range -50 dBm to -130 dBm; smaller absolute values indicate stronger signals.
iOS devices: Open the phone dialer, enter *3001#12345#*, tap Call, then tap "Serving CELL info" and find "RSRP" to view the precise signal strength value.
Android devices: Open Settings → About phone → Status information → Network, then find "Signal strength" to view the precise current signal value.
