Combining received signals
In communications technology , existing reception diversity (for example antenna diversity) can be used to gain diversity by combining the signals from the individual receiver branches. According to Brennan, a number of different complex procedures are known for this:
- Constructive combining
- merges the available signals from several receiving units into one overall signal. For this purpose, the individual signals are brought into the same phase position beforehand.
- Equal gain combining
- simply adds the available signals.
- Maximum-ratio combining or maximum-ratio combining
- combines the signal currents weighted according to their signal-to-noise ratio, which effectively amplifies the useful signal to the maximum possible signal-to-noise ratio. The weighting factor of the individual signal is proportional to its signal-to-noise ratio.
- Switched / scanning combining
- If the signal strength drops below a certain threshold value, a better transmission channel is selected.
- Selection Combining
- The strength of all input signals is continuously compared and the strongest signal is used at each point in time.
- Timing combining
- The principle of "timing combining" was defined in 2012 to merge longer signal sequences that are transmitted redundantly in parallel, such as data packets. A " timing combiner " immediately forwards the first completely received data packet for processing and discards the packet copies arriving later via the redundant paths. As a result, the fastest channel always “wins” and not only can a considerable improvement be achieved in terms of packet loss, but also, above all, the time behavior in wireless data transmission.
literature
- ^ DG Brennan, "Linear diversity combining techniques," Proc. IRE, vol. 47, no. 1, pp.1075-1102, June 1959
- ↑ Rentschler, M .; Laukemann, P., "Performance analysis of parallel redundant WLAN," Emerging Technologies & Factory Automation (ETFA), 2012 IEEE 17th Conference on, vol., No., Pp.1,8, 17-21 Sept. 2012