How Mobile Coverage Works

Base Stations and Cell Sectors

A base station (also called a Node B in 3G, eNodeB in 4G, or gNodeB in 5G) is the fixed radio equipment that communicates with mobile devices. Each base station typically hosts multiple antenna panels mounted on a tower or rooftop structure. The geographic area served by a single base station is divided into sectors — usually three, each covering approximately 120 degrees of azimuth.

Each sector constitutes a separate cell, which forms the basic unit of a cellular network. When you make a call or access data, your device is connected to a specific cell. As you move, the network continuously evaluates signal quality and switches your connection to a better cell — a process called handover.

In dense urban areas, cells may have a radius of just a few hundred meters. In rural Germany, a single base station may cover several kilometers. The relationship between cell size and capacity is inverse: smaller cells support more simultaneous users at higher data rates.

Frequency Bands

Mobile networks operate across a range of licensed radio frequency bands, each with distinct propagation characteristics. German operators hold spectrum in multiple bands simultaneously, using each for specific coverage and capacity purposes.

Low-Band (700–900 MHz)

Frequencies below 1 GHz propagate over long distances and penetrate buildings effectively. In Germany, the 700 MHz band (Band 28) was reallocated from digital television broadcasting and auctioned in 2015. All three operators use this band for wide-area 4G coverage and, increasingly, for 5G NR.

The 900 MHz band (Band 8) is used for 2G (GSM) and 3G (UMTS) legacy services by all operators, as well as for 4G LTE in some deployments.

Mid-Band (1800–2600 MHz)

Mid-band frequencies provide a balance between range and data capacity. The 1800 MHz band (Band 3) is the most widely deployed LTE band in Germany and carries the majority of 4G data traffic in urban and suburban areas. The 2100 MHz band (Band 1) has historically been used for 3G UMTS and is now being refarmed for 4G and 5G.

The 2600 MHz band (Band 7) adds capacity in high-density areas such as city centers, stadiums, and transit hubs, but its shorter range makes it unsuitable for rural deployment.

High-Band (3.5 GHz+)

The 3.4–3.8 GHz spectrum (Band n78) is the primary 5G NR frequency in Germany, auctioned in 2019. It delivers substantially higher peak data rates than 4G but has limited range — typically 300 to 800 meters per cell in outdoor conditions. This means urban areas require far more base stations per km² compared to low-band coverage.

Millimeter wave frequencies (above 24 GHz) are being trialed in Germany but have not been deployed at scale for public networks. Their very short range and poor building penetration limits them to indoor or fixed-wireless applications.

Signal Propagation

Radio signals do not travel in straight lines through a uniform medium. Instead, they are subject to path loss (power decreasing with distance), shadowing (attenuation by terrain and buildings), and multipath fading (signal arriving via multiple reflected paths and interfering with itself).

Propagation models used by German operators typically follow the ITU-R or 3GPP-specified path loss formulas, adjusted for local terrain data from the Deutsche Telekom or German Federal Institute for Geosciences and Natural Resources datasets. These models underlie the coverage predictions shown on operator maps.

Diffraction and Reflection

At lower frequencies, radio waves can diffract around obstacles such as hills and large buildings — this is why 700–900 MHz provides coverage in valleys and behind terrain features where line-of-sight to the base station is impossible. At higher frequencies (above 2 GHz), diffraction is reduced and coverage gaps behind obstacles become more pronounced.

Reflection from buildings and surfaces creates multipath signals. Modern LTE and 5G equipment uses MIMO (Multiple-Input Multiple-Output) antenna technology to exploit these multipath components to increase throughput rather than treating them as interference.

Handover and Mobility

As a mobile device moves through a network, it must seamlessly transfer its connection from one cell to another. This process is called handover (or handoff). The network continuously monitors the signal quality reported by the device and triggers a handover when a neighboring cell offers a better connection.

In LTE, the handover decision is made by the eNodeB (base station), which communicates with adjacent eNodeBs via the X2 interface. In 5G NR, the same function is performed by the gNodeB using the Xn interface. The process typically completes in 20–50 milliseconds, imperceptible to most applications.

Carrier Aggregation

Modern 4G and 5G devices in Germany can simultaneously use multiple frequency bands — a technique called carrier aggregation (CA). For example, a device might aggregate 10 MHz on Band 20 (800 MHz) for coverage with 20 MHz on Band 3 (1800 MHz) for capacity, combining them into a single logical channel delivering higher throughput than either band alone.

Interference and Network Capacity

When multiple base stations transmit on the same or adjacent frequencies, their signals can interfere with each other. German operators manage inter-cell interference through careful frequency planning, power control, and coordination algorithms defined in the 3GPP standards.

Network capacity — how many users can be served simultaneously at acceptable quality — depends on the total spectrum bandwidth available, the modulation order (e.g., 256-QAM in LTE-Advanced), the MIMO configuration, and cell density. Congestion is most commonly experienced during large public events, rush hour in dense urban areas, or during emergency situations when many people simultaneously attempt to access the network.

Frequently Asked Questions