150 Kbps is a good internet speed

One gigabit, 867 megabits - when you buy a router, insane transmission speeds are often promised on the packaging. But what does that mean in practice? And why does the video stream sometimes stop at the end?

Berlin (dpa / tmn) - 400, 600 or 800 megabits per second (Mbit / s)? Or even a gigabit and more? If you believe the information on the packaging of wireless routers, there can be no traffic jams or slowdowns in video streaming in the home network. But in practice it is usually slower.

Especially with WLAN, the speeds achieved in practice often deviate significantly from the information in the data sheet. There are technical reasons for this, as Ernst Ahlers from the computer magazine “c't” explains. With WLAN, there is only one transmission channel for all devices in the wireless network set up by the router - the selected wireless channel. “Up to now, they have not been able to send and receive at the same time,” he says. "That is why the WLAN transmission protocol provides for breaks in transmission, during which everyone has to listen in order to agree who can transmit next." No data streams flow during these breaks. "Nevertheless, the individual WLAN data packets actually fly at maximum speed with a good wireless connection."

Some routers, with WLAN 2.4 and 5 gigahertz (Ghz), sometimes even 60 GHz, serve several radio bands simultaneously - a so-called "simultaneous dual band". Their maximum possible data rates are then often added up in the advertising: "For example, 300 Mbit / s gross to 2.4 GHz and 867 Mbit / s gross to 5 GHz then become 1167 or rounded 1200 Mbit / s," says Ehlers. A very theoretical value, "because all clients known to me so far only work on one radio band." In general, the following applies: The typical gross-net ratio for WLAN is around 50 percent. The promises on the packaging are not fundamentally wrong, but they are also not realistic.

And there is another factor: "When it comes to Internet access, the home network is only as fast as the slowest component," says Kai Petzke from the telecommunications portal "Teltarif.de". In other words: an old notebook with slow WLAN will not be accelerated even by a router with the latest wireless technology.

Techniques such as MIMO (Multiple Input Multiple Output) should bring more speed into the wireless network. Several radio antennas are used that send parallel data streams, according to the “CHIP” WLAN manual 2017. Example: If a large video file is streamed via a MIMO router with three antennas, each transmission unit will ideally transmit a third of the data. With the widespread WLAN standard 802.11n this is theoretically 150 Mbit / s per data stream, with the newer standard 802.11ac a nominal 433 Mbit / s. Theoretically.

In practice, many factors still disrupt the function and ultimately also the speed of the data flow in the WLAN: wireless networks of the neighbors, walls and concrete ceilings or an unfavorable location for the router. All of this can slow down the wireless network even further. And by no means all devices have mastered modern transmission technologies. "For example, it is of little use if a router can achieve up to 867 Mbit / s gross in the 5 GHz band, but all clients are wrangling over its 2.4 GHz radio module, which can achieve a maximum of 300 Mbit / s gross" says Ernst Ahlers. Many older or cheaper devices often do not even transmit at 5 gigahertz.

But even if many high-speed routers cannot ultimately deliver the advertised speed, with more modern standards and technologies such as MIMO they can still cope better with the growing number of networked devices in modern households.

And one more thing should not be forgotten: The specified maximum speeds for routers only ever refer to data exchange within the network. If data is loaded directly from the Internet, the maximum speed of the WLAN does not matter. Then everything only goes as fast as the Internet access allows. "For actual Internet access, it is a maximum of 16 Mbit / s with ADSL, with VDSL usually 25 to 50 Mbit / s, with VDSL vectoring up to 100 Mbit / s and with cable connection up to 400 Mbit / s," says Kai Petzke. Again, these are theoretical values ​​that are not always achieved in practice.

The simplest thing with the transmission speed is when a computer or other network device is connected to the router with a LAN cable. "If routers like laptops have gigabit ethernet ports, the cable reliably provides 1000 Mbit / s, otherwise at least 100 Mbit / s," says Kai Petzke.