Diversity technique
The concept of diverse redundancy to increase availability or improve reliability has long been used in many technical areas. In communications engineering, diversity technology is used for redundant transmission of data via stochastically independent channels that are only prone to errors with a low probability at the same time.
Operating modes
In radio transmission technology , a basic distinction is made between the following forms of diversity operating modes:
Time diversity
The information in the user data is staggered several times and thus sent several times over the same radio channel in order to compensate for time-dependent fluctuations in signal strength.
Spatial diversity
Two or more send-receive paths are operated here. This is mostly realized by spatially separated antennas which are operated in parallel. Depending on the method, the receiving device then selects the strongest received signal or the bandpass layer combines the received radio signals.
Frequency diversity
The same signal is transmitted simultaneously over two or more different carrier frequencies. In the event of interference or a complete signal cancellation, it is to be expected that not all frequency ranges used will be affected. When the signal is transmitted in parallel, two or more transmitters and receivers are operated in parallel and thus occupy two or more frequency bands.
Combiner
An important element in diverse transmission systems is the combiner , which brings together the diverse redundant signals on the receiving side, or selects the better one for further processing. The combiner technologies are traditionally classified according to Brennan in the English-language specialist literature as follows:
- English maximum ratio combiner
- English Equal-Gain Combiner
- English Scanning / Switching Combiner
- English Selection Combiner
To merge by parallel redundant longer transmitted signal sequences, such as, data packets of the principle was in 2012. English timing Combining defined. In principle, working in a similar way to an English selection combiner , a timing combiner immediately forwards the first completely received data packet for processing and discards the packet copies that subsequently arrive via the redundant paths. As a result, the fastest channel always wins and a considerable improvement can be achieved not only with regard to packet loss, but above all the time behavior in wireless data transmission and wide area data transmission.
literature
- ^ DG Brennan: Linear Diversity Combining Techniques . In: Proceedings of the IRE . 47, No. 6, June 1959, ISSN 0096-8390 , pp. 1075-1102. doi : 10.1109 / JRPROC.1959.287136 .
- ↑ a b M. Rentschler, P. Laukemann: Performance analysis of parallel redundant WLAN . In: Proceedings of 2012 IEEE 17th International Conference on Emerging Technologies Factory Automation (ETFA 2012) . September 2012, pp. 1–8. doi : 10.1109 / ETFA.2012.6489647 .
- ^ Mark Graham: Applying High Availability Design and Parallel Redundancy Protocol (PRP) in Safety Critical Wide Area Networks . In: Journal of Telecommunications System & Management . tape 04 , no. 01 , July 29, 2015, ISSN 2167-0919 , doi : 10.4172 / 2167-0919.1000120 ( omicsgroup.org [accessed June 29, 2017]).