As soon as many users and hardware manufacturers have become familiar with n-WLAN, there are already the first devices with a new, even faster standard. The successor of n-WLAN is called 802.11ac or short: ac-WLAN. The new devices promise radio transmission rates of up to 1300 Mbit / s. We will tell you whether the upgrade is worthwhile and show the different WLAN standards at a glance.
The classics: a- and g-WLAN
The fastest home network routers of the (still) current n-WLAN class are significantly lower with transmission rates of up to 450 Mbit / s. So what improvements does the new WLAN generation offer against its predecessors? And is worth the switch to a new ac router now? In this context, the characteristics and distribution of the preceding WLAN standards play a decisive role.
Funk Solo: simple n-WLAN
Before it comes to the technical cornerstones of ac-WLAN, first a brief overview of the WLAN standards that are currently being applied in the various network devices in retail and at home. Only with the help of this information can you guess the pros and cons for the purchase of an ac WLAN router.
Dual transmission: Dual-band n-WLAN
The overview table below shows the most important similarities and differences of all relevant WLAN standards. The information refers to home network devices in the United States and the corresponding dualband combinations.
Why a second frequency band?
Two different radio frequency bands are currently available for the WLAN radio: the 2.4 GHz band and the 5 GHz band. In order for a wireless connection to be established, the receiver and transmitter must transmit in the same frequency band. A router, which only radiates at 2.4 GHz, can not enter a wireless connection with a notebook whose WLAN adapter transmits exclusively in the 5 GHz band. The frequency band (and the maximum transmission rate) that can be used by a WLAN device can be determined from the WLAN standards indicated on the package or in the manual.
The g-WLAN standard (802.11g), which is still widespread in the United States, is, for example, transmitted in the 2.4 GHz band with a maximum gross data rate of 54 Mbit / s. G-WLAN uses a transmission channel with a bandwidth of 20 MHz. Although g-WLAN has been replaced in recent years by the successor standard n-WLAN (2.4 GHz), there are still many g-WLAN devices in American households. Even the trade still offers such devices.
The a-WLAN standard (802.11a), which is more common in the USA and is also out of date, also transmits up to a maximum of 54 Mbit / s - however, in the 5 GHz frequency band. Pure a-WLAN devices can therefore not enter into a connection with pure g-WLAN devices. In order to solve this problem of communication, there were already, in the past, first dual-band devices whose WLAN modules could radiate in both frequency bands.
Such WLAN adapters were often found in business notebooks. Business users could thus not only plug in to the prevailing g-WLANs here, but if necessary also use a corresponding a-WLAN network abroad.
Just like g-WLAN, its successor, n-WLAN, also basically uses the 2.4 GHz band, where the transmission channel can be extended from 20 MHz to 40 MHz. A further increase in speed occurs with n-WLAN through the data transmission over several parallel data streams. The term "MIMO" for "Multiple-Input-Multiple-Output" or "Multiple (data) input - multiple (data) output".
Depending on the number of antennas and the transmitting and receiving units installed in the WLAN module, MIMO increases the transmission power of home networks to up to 450 Mbps. According to 802.11n specifications, up to 600 Mbps is possible.
In order for the communication to older WLAN devices to work, n-WLAN is downwards compatible with the g-WLAN standard. There is usually a note or a corresponding certificate from the WiFi Alliance, which lists all supported standards in lowercase, such as 802.11b / g / n.
The "b" stands for a standard which also transmits in the 2.4 GHz band. It is compatible with g- and n-WLAN, but has a transmission rate of no more than 11 Mbit / s. Although this b-WLAN standard has long since ceased to play a role in the home network, it is still indicated on every package of a WLAN device.
Download: Table
Ac-WLAN: the 5 GHz band turbo
Most of the newer n-WLAN devices are now dual-banded and offer an additional connectivity in the 5 GHz band in addition to the 2.4 GHz band. The top speed in the 5 GHz range is just as much as that of n-WLAN with 2.4 GHz at currently 450 Mbps. For this purpose, the maximum bandwidth (40 MHz) and three parallel data streams must be used. Also n-WLAN with 5 GHz is downwards compatible to its slower predecessor standard a-WLAN. However, the transmission rate is limited to 54 Mbps.
Dual band-capable n-WLAN routers can simultaneously simultaneously connect a WLAN in the 2.4 GHz band and a second in the 5 GHz band. The standards of a dual-banded n-WLAN router are now commonly referred to as 802.11a / b / g / n. The most powerful dual-band routers also run under the name "N900", since they can span a wireless LAN with 450 Mbps in each frequency band. But what is the benefit of a second WLAN in the 5 GHz band?
Channel restriction
As before, WLANs in American households are mainly using the 2.4 GHz band, as nearly all home-capable devices are equipped with 2.4 GHz WLAN (802.11b / g / n). Even with an optimal distribution of the transmission frequencies, only three to four neighboring WLANs can radiate without interfering with each other. In densely populated residential areas, this value is usually exceeded very quickly.
The mutual overlaying of the radio networks leads to falling transmission rates and also limits the range of the individual WLANs. For example, video transmissions can lead to annoying connection breaks. If you have a fast a / b / g / n router (N900, N750), bandwidth-intensive and time-critical transmissions can be routed via the 5 GHz WLAN, which is still little used. However, the corresponding WLAN clients in the home network must also be equipped with a fast a / b / g / n WLAN adapter.
Unfortunately, there are still very few devices in the market that are equipped with 5 GHz WLAN, such as few expensive notebooks. Network-capable devices of entertainment electronics, such as Blu-ray players, media players or smart TVs, usually have only one network connection and b / g / n WLAN. From 5-GHz WLAN no trace. A retrofit is almost always required. For living room appliances, fast Ethernet bridge with a / b / g / n-WLAN is the best solution.
Conclusion
This allows multiple LAN devices to be connected simultaneously to the dual-band router via the 5-GHz band. However, an n-WLAN connection at 5 GHz is much more effective than an n-WLAN connection at 2.4 GHz due to obstacles such as walls or floor coverings.
The 802.11ac standard (ac-WLAN), on the other hand, promises significantly more performance in the 5 GHz band. First of all, ac-WLAN describes only radio connections in the 5 GHz band. The reason: In the 5 GHz band, more than 300 MHz bandwidth is available, which the new ac-WLAN standard can use for transmissions. Although the first available ac-routers use only a part of this bandwidth, they already reach the threefold transmission rate of a fast N900 router.
In the 2.4 GHz band, however, the limit is reached with n-WLAN (2.4 GHz). Even faster data connections can hardly be realized in the 2.4 GHz band, since only a narrow transmission corridor of a maximum of 80 MHz bandwidth is available.
This multiplication of the transmission rate in the case of ac-WLAN is achieved on the one hand by an additional broadening of the transmission bandwidth to 80 MHz (optionally even up to 160 MHz). Compared to the 2.4 MHz band, the 5 GHz band offers a three to four times the number of usable transmission channels. A further increase in the speed is achieved by a more powerful coding of the data signal via the so-called quadrature amplitude modulation (QAM).
Finally, with ac-WLAN, the number of parallel data streams (MiMo) can be increased to up to eight, while the n-WLAN standard defines a maximum of four MiMo streams. For a better connection also over unfavorable connecting distances ensures also in the ac-WLAN standard prescribed Beamforming. In this case, the ac router determines the best connection path to the WLAN client via its multiple antenna.
Beamforming allows the router to some extent to direct its radio signal to the WLAN client and to avoid obstacles. However, for a maximum transmission rate between ac routers and receivers, the WLAN client must also be equipped with ac-WLAN.
Currently, there are no devices with integrated ac-WLAN. Already available USB 2.0 adapters do not reach the maximum transmission rate of ac-WLAN because the USB interface is limited to 480 Mbps. As a suitable replacement for ac-WLAN routers, currently only ac-WLAN bridges are recommended. Trendnet and Cisco offer this.
All currently available wireless WLAN routers use only the lowest frequency block in the 5 GHz band with channels 36 to 48. This block is completely occupied by the 80 MHz wide transmission channel in the ac transmission mode. If one of the neighbors converts its home network also to ac-WLAN, its ac-router also func- tions on channels 36 to 48. This has an effect on the maximum transmission power of both WLAN networks, which is significantly reduced.
In order to avoid alternative and unused 5 GHz channels, the ac routers must have the automatic frequency change (Dynamic Frequency Control, DFS). In addition, they must be able to reduce their transmission power using Transmit Power Control (TCP). As long as an ac router does not support DFS or TCP, it can not use the rest of the 5 GHz frequency spectrum.
In the remaining functions and equipment features, the ac routers are quite similar to their N900 predecessors. All ac routers also have a fast 2.4 GHz n-WLAN integrated, have a gigabit switch with four four LAN ports and one or two USB ports with NAS function for the integration of USB memory into the home network . The market overview provides a small overview.
The new ac WLAN routers use the five-GHz WLAN, which is still little used in the United States, far better than the dual-band routers of the predecessor standard n-WLAN. This is also shown when bridging difficult links using beamforming. If you want to achieve top speeds and the best possible connection performance in the home network, you need a correspondingly fast remote.
This is currently only available as an ac-WLAN Ethernet bridge. Alternative client devices with integrated ac WLAN are currently not available on the market. With ac WLAN sticks the fast WLAN is braked by the slow USB 2.0.
Problematic is the current channel usage in the 5 GHz band, which is currently limited for all ac routers. DFS and TCP are not expected to be upgraded by means of firmware updates, but will only be available in the next ac router generation. Without these functions, the use of the remaining 5 GHz band is not allowed.
Who already has a powerful n-WLAN dual-band router in use, should wait with the switch to ac-WLAN still so long until the ac-routers with DFS support the automatic frequency change. Who immediately needs a fast dual-band router, should access the ac router and not an N900 device. The clear power-up in the 5 GHz band is far too great for the low price difference between the two device classes.
Download: Table
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