Diversity scheme

The concept of diversitary redundancy to increase availability and improve the reliability is used in many technical fields for a long time. In communications with the diversity technique is carried out to the redundant transmission of data over stochastically independent channels, which are prone to error in only a small probability of the same time.

Modes

In radio transmission technology, a fundamental distinction between the following forms of diversity modes:

Time diversity

User data are repeatedly sent over the same channel time offset to compensate for time-dependent variations in the signal strength.

Space diversity

In this case, two or more transmitter-receiver channels are operated. This is achieved mostly by spatially separated antennas. The receiver selects the strongest received signal.

Frequency diversity

The same signal is simultaneously transmitted over two or more carrier frequencies. In case of faults or a complete signal loss is to be expected that not all frequency ranges used are affected. In the parallel transmission of the signal transmitter and two receivers are operated in parallel and thereby uses two frequency bands.

Assemblers

An important element in such a diversitary transmission system is the so called " Combiner ", which combines the signals on the receiving side again diversely redundant, or selects the better for further processing. The " combiner " technologies are traditionally classified according to Brennan as follows:

• Maximal ratio combiner
• Equal Gain Combiner
• Scanning / switching combiner
• Selection Assemblers

To merge of parallel redundantly transmitted longer signal sequences, such as data packets, has been defined the principle of " combining timing " in 2012. In principle, similar to working as a " Selection Combiner " initiates "Timing Combiner " on the first fully received data packet immediately for processing and discards the redundant paths on the following incoming packet copies. This always "wins" the fastest channel and it can be a significant improvement not only be above all of the time response achieved with wireless data transfer with respect to packet loss, but.