A look at the AVM product comparison shows that current FRITZ!WLAN repeaters such as 1750E or 1160 support a function called "crossband repeating". What exactly is that and why is the function for rapid data exchange in a home network important?
A step backwards: same band repeating
Repeaters receive the wireless signal from the FRITZ!Box and re-transmit it, thereby extending the reception range. In technical jargon this process is called "repeating". FRITZ!Box and client (e.g., smartphone, tablet, notebook) exchange data, with the repeater serving as the central exchange.
Older devices used the 2.4 GHz band exclusively, but since the introduction of Wireless AC, the 5 GHz band has also been available. These bands involve a frequency range in which router, repeater and client communicate. If FRITZ!Box and repeater support only the 2.4 GHz band, for example, repeating takes place only on that band. This is referred to as "same band repeating".
Crossband repeating works in a different way. When router and repeater support both bands, they are always connected to each other on the two bands. Parallel exchange accelerates the transmission. The individual clients are connected to the repeater either via the 2.4 GHz or 5 GHz band, but benefit from crossband communication to the FRITZ!Box.
No loss of speed
In same band repeating the data packets are first received by the repeater and then re-transmitted. Speed is halved in favor of increased range. In crossband repeating when the data switches from one band to the other during transmission, there is no loss of speed. That's possible because transmission and reception can run parallel during the switch. With same band repeating, data transmission and reception occur one after the other. Therefore, crossband repeating trumps same band for fast communication in the home network.
Intelligent band selection
With its current repeaters AVM goes one step further by equipping these devices with "intelligent crossband repeating", which independently selects the most suitable band for transmission. In practice it looks like this: The repeater selects a band for each registered client and re-transmits the data accordingly. When Wireless AC is used, the repeater re-transmits data from a 5-GHz client to the Box via that band (same band), while a 2.4-GHz client changes the band and continues along the 5 GHz track (crossband).
Of course that works in the other direction too. If the router can transmit only on the 2.4 GHz band, the communication to the repeater takes place there. From that point the data switches to the 5 GHz band in order to reach the intended clients.