Popular Science: Mobile 5G WiFi those things (two)



Thanks for Jeff_hill's delivery.

Many people must have such confusion: everyone is familiar with the 2G/3G/4G communication standard, 5 G what, how to go with the WiFi pull on the relationship. The previous article explains that traditional WiFi is susceptible to interference and there are two reasons:

WLAN 802.11 standard equipment deployment dense, easy to produce the same frequency interference

Non-WLAN standard devices are also using the 2.4G ISM band

Summed up, is the main use of WiFi before the 2.4GHz band, too "congestion", in order to solve the problem of the extension of a new way: the inclusion of the new spectrum resources--5ghz Band. The so-called 5G WiFi, highlighted is the WiFi network spread in the 5G band, rather than the birth of what is higher than 4G 5G communication standards .

Since WiFi Federation certified devices are compliant with the WLAN (Wireless LAN) 802.11 standard, and this standard has been in development, so support different 802.11 standard WiFi devices, data transfer effect (speed, distance, wall) is not the same.

The most common criteria:

802.11b Standard . Spread on the 2.4G band, providing only 20MHz of standard bandwidth, the highest transfer rate 11mbit/s.

802.11g Standard . Also spread on the 2.4G band, the same only provides 20MHz standard bandwidth, but the maximum transfer rate is increased to 54mbit/s and backwards compatible with 802.11B devices.

All devices that can connect to a WLAN network, whether on a mobile phone or a computer, generally support these two standards. It is clear that devices that support the 802.11G standard can have a higher transfer rate.

802.11a Standard

Spread in the 5G band, and also only provide 20MHz standard bandwidth, the maximum transfer rate is 54mbit/s.

Although the 802.11A standard is one of the WLAN's original standards, it was established as early as 1999 (the same rate as the 802.11G standard was established 2003 years ago), but due to propagation in the 5G band, the vast majority of devices that support 802.11b/g cannot be compatible with.

802.11A standard spread in the 5G frequency band, this frequency band currently less civilian, so compared to the increasingly crowded 2.4G band, not susceptible to interference, there is better data throughput performance. However, the 5G signal is more easily absorbed by the wall, and the transmission distance is less than 802.11b/G.

802.11n Standard

This standard is a change worthy of writing. It can be spread simultaneously in the 2.4/5ghz band, the maximum transfer rate of a single channel is increased to 72.2mbit/s, and 20mhz/40mhz Two bandwidth options are provided, and MIMO technology is introduced.

Allow twice times the standard bandwidth of 20MHz 40MHz, like a road road widened by one times, the original only two vehicles can now pass through 4 vehicles simultaneously. As a result, the rate of data transfer increases by a factor of one per time.

As for, MIMO technology may have fewer people to understand. Here's just a quick explanation.

MIMO is multi-input and output technology, wireless network communication data through multiple cutting, after multiple antennas for synchronous transmission, because the wireless signal in the process of transmission, susceptible to a variety of factors and interference, will take different reflection or traversal path, so the time to reach the receiving end is inconsistent. In order to avoid the data being out of sync and not being able to regroup, receive the driven by multi-antenna receive, the receiver signal uses the DSP to recalculate the way, according to the time difference factor, divides the separate data the output correct and the fast data stream. As the data of wireless transmission is segmented and transmitted, it not only reduces the single data flow, but also extends the transmitting distance, and expands the antenna receiving range.

In short,MIMO technology instantly increases the data rate of several times, without the need for additional spectrum, while also extending the signal reception distance . The MIMO technology under the 802.11N standard supports a maximum of 4-way expansion, as if providing a 4-layer stereo lane.

Normal highways are upgraded to highways (up to 72.2mbit/s at the maximum rate of 20MHz bandwidth), with the road widening one-fold (double bandwidth available), and 4-storey three-dimensional road (4X MIMO support). combined with these three improved 802.11n standards, the overall data throughput is theoretically up to an astonishing 600mbit/s.

802.11AC Standard

This is what we commonly known as 5G WiFi, it only spreads in the 5G band, provides 20/40/60/80mhz four kinds of bandwidth options, MIMO technology from 4 multiplexed to the maximum support 8 multiplexing, the transmission rate of a single channel under different bandwidth has also improved.

The 802.11ac can almost be seen as a revised version and a reinforced version of 802.11n. Only in the 5G band, "Revised" There is also a 2.4G selectable transmission frequency band, while increasing the bandwidth selection of 60/80mhz, MIMO technology expansion to 8 multiplexing, the maximum transmission rate of a single channel is increased, the equivalent of further widening of the road, three-dimensional plus more layers, the speed limit of the highway is wider. Overall data throughput, so there's a huge leap.

Here is a comprehensive comparison of the different 802.11 standards:

Devices that you can connect to Wi-Fi (WiFi) in your hand, typically indicate which WLAN 802.11 standards can be supported.

Support different standards, the data transfer effect will vary greatly. This is why manufacturers are aggressively promoting their phones to support dual-channel Wifi/5gwifi. adjourned

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