Guard interval
An English guard interval , and guard interval called, is in the communications technology used to prevent that certain transfers mix. They increase the interference immunity against propagation delays, echoes and reflections , to which digital data are usually very susceptible. The length of the guard interval determines how susceptible a transmission is to interference. The longer such an interval, the better it protects against interference, but the lower the channel effectiveness.
In OFDM , each symbol is preceded by a guard interval, which contains a copy of the signal curve at the end of the symbol. Interferences such as signal echoes or delayed reception of other transmissions with the same signal course (single frequency network ), the total time interval of which is less than the duration of the guard interval, can be corrected at the receiver by a suitable selection of the evaluation range ( FFT window).
With TDMA , the time span of each user ends with a guard interval in order to limit the influence of transmission delays and thereby prevent data loss and reduce interference for the following user.
Web links
literature
- Sandra Knörzer: Radio channel modeling for OFDM communication systems in high-speed trains . KIT Scientific Publishing, 2009, ISBN 978-3-86644-361-7 .