- What are electromagnetic fields?
- Static and low-frequency fields
- What are static and low-frequency electric and magnetic fields?
- Direct and alternating voltage
- Effects of static and low-frequency fields
- Reports & Evaluations
- Radiation protection relating to the expansion of the national grid
- Basics transfer of electrical power
- High-frequency fields
- What are high-frequency fields?
- Applications high-frequency fields
- Radiation protection in mobile communication
- What is mobile communication?
- Reports and evaluations
- What is optical radiation?
- UV radiation
- What is UV radiation?
- Sun but safe!
- Effects of UV radiation
- Protection against UV radiation
- UV index
- Infrared radiation
- What is ionising radiation?
- Radioactivity in the environment
- Where does radioactivity occur in the environment?
- What is the level of natural radiation exposure in Germany?
- Air, soil and water
- Building materials
- Industrial residues (NORM)
- BfS laboratories
- Applications in medicine
- Radiation protection in medicine: international activities
- Applications in daily life and in technology
- Radioactive radiation sources in Germany
- Register high-level radioactive radiation sources
- Type approval procedure pursuant to RöV and StrlSchV
- Cabin luggage security checks
- Radioactive materials in watches
- Ionisation smoke detectors (ISM)
- What are the effects of radiation?
- Effects of selected radioactive materials
- Consequences of a radiation accident
- Cancer and leukaemia
- Genetic radiation effects
- Individual radiosensitivity
- Epidemiology of radiation-induced diseases
- Ionising radiation: positive effects?
- Risk estimation and assessment
- Radiation protection
- Basic information
- Occupational radiation protection
- Nuclear accident management
- What is an emergency?
- What happens in an emergency?
- Federal and state tasks
- In the event of an emergency
- Measuring networks
- Exercises for emergency situations
- Defence against nuclear hazards
- Service offers
- Radon measurements
- Incorporation monitoring
- Biological dosimetry
- Online library
- About us
- Science and research
- Research concept
- Scientific collaborations
- EU research framework programme
- BfS research programme
- Third-party funded research
- Departmental research
- Selected research projects
- Selected research results
- Professional opinions
- Science Council
- Laws and regulations
- BfS Topics in the Bundestag
- Between 1992 and 1995, the first completely digital mobile telephone networks went into operation in Germany.
- These networks, which are still used today, operate according to the GSM standard (Global System for Mobile Communications).
- They employ radio frequencies in the range of 900 MHz and 1800 MHz.
In order to provide wide area coverage with mobile radio applications, the areas to be served are divided into radio network cells, each of which is covered by stationary radio transmitter stations (base stations or base transceiver stations). Usually three sectors, which each cover an angle of 120°, are each provided with one or several radio channels from one location. Three antennas, staggered against each other, are installed at one antenna location.
Base stations and radio network cells
The base stations communicate with the mobile terminals using high-frequency electromagnetic fields. The base stations are connected to a mobile switching centre via cable or radio link systems. The radiated powers of the stations typically range from 10 to 50 watts. They depend, among other things, on the size of the relevant cell whose typical radii can vary between a few tens of metres for so-called pico cells and 35 kilometres for macro cells in rural areas, and on the number of people making calls at the same time. Nowadays, well-developed mobile network coverage with small cell networks is provided especially in cities. New base stations are continued to be built to increase the capacity and to cover dead zones. However, new stations mostly use more advanced mobile communications technologies such as UMTS or LTE.
Distinguishing the cells
As several phone calls are usually conducted at the same time within the same cell, their radio signals have to be distinguishable. Initially they are distinguished by the frequencies of the radiation.
Every mobile network operator is assigned a frequency range by the Federal Network Agency (formerly: Regulatory Authority for Telecommunications and Posts RegTP) which is divided into several narrow frequency bands (frequency channels). Adjacent cells use different frequency bands to avoid interference between phone calls.
Time slot technique
In order to increase the number of possible simultaneous conversations in a cell, the so-called time slot technique is employed. A period of 4.62 milliseconds is divided into 8 time slots of 0.577 milliseconds each. A particular mobile phone uses only one of the 8 time slots for sending information to the base station during a phone call. In the remaining time slots, the base station can receive information from other mobile phones. For an individual mobile phone this results in a pulsed transmission signal with one pulse per 4.62 milliseconds, which equates to a pulse repetition frequency of 217 Hz. This is referred to as a low-frequency pulsed high-frequency signal. The pulsing of the base station signals depends on the number of simultaneous conversations in each frequency channel and can vary significantly.
State of 2018.01.17