Diversity combining is the technique applied to combine the multiple received signals of a diversity reception device into a single improved signal. Various techniques Various diversity combining techniques can be distinguished: Equal-gain combining: All the received signals are summed coherently. Maximal-ratio combining is often used in large phased-array systems: The received signals are weighted with respect to their SNR and then summed. The resulting SNR yields where is SNR of the received signal . Switched combining: The receiver switches to another signal when the currently selected signal drops below a predefined threshold. This is also often called "Scanning Combining". Selection combining: Of the N received signals, the strongest signal is selected. When the N signals are independent and Rayleigh distributed, the expected diversity gain has been shown to be , expressed as a power ratio. Therefore, any additional gain diminishes rapidly with the increasing number of channels. This is a more efficient technique than switched combining. Sometimes more than one combining technique is used – for example, lucky imaging uses selection combining to choose (typically) the best 10% images, followed by equal-gain combining of the selected images. Other signal combination techniques have been designed for noise reduction and have found applications in single molecule biophysics, chemometrics among other disciplines. Timing combining When the focus is on the wireless transmission of longer signal sequences, such as for example Ethernet packets, specific performance characteristics regarding diversity gain on a parallel redundant wireless transmission system can be observed. For "timing combining", data packets are redundantly and simultaneously sent over parallel paths. On the receiving side, out of the branches the first arriving packet is selected and immediately processed towards the end application. Further copies of the packet -if arriving- are discarded. This type of postdetection combiner is called a "timing combiner", since a significant performance improvement is gained through the immediate processing of the first arriving packet. Switched combining two-way radio example In land-mobile radio, where vehicle-mounted and hand-held radios communicate with a base station radio over a single frequency, space diversity is achieved by having several receivers at different sites. Diversity combining, or voting, in two-way radio systems is a method for improving talk-back range from walkie-talkie and vehicular mobile radios. The receivers are connected to a device referred to as a voting comparator or voter. The voting comparator performs an evaluation of all received signals and picks the most usable received