802.11ac is a new wireless LAN standard for meeting the demands of higher bandwidth. This new standard is an update of the .11n standard and downward compatible to wireless LAN clients operating with older standards such as 802.11a/b/g/n. The new standard uses exclusively the 5 GHz frequency. Access Points supporting .11ac should therefore always be dual radio access points for using both 2.4 and 5 GHz.
In general, 802.11ac access points have two radio modules. One radio module supports clients which only have 2.4 GHz 802.11bgn. The other one is a 5 GHz 802.11ac radio module. This enables a smooth migration to the new standard without excluding older clients. Furthermore, the 802.11ac radio module is also compatible to previous clients supporting 802.11a/h (4 Mbit/s) or 802.11an. A mixed operation between 802.11a/h, 802.11an and 802.11ac clients is also possible.
Migrating a network towards .11ac
The following aspects have to be taken into account when converting a network to the 802.11ac standard.
Ethernet cabling and switches
Cabling and switches should have Gigabit standard in the LAN. Earlier versions such as 100Mbit/s should be replaced as these switches are already a bottleneck in 802.11n systems. Professional access points use 1Gbit/s LAN ports with full performance. Two Ethernet cables and a complex bundle of the two Ethernets within the switch are usually not necessary. Whether a Gigabit interface as an uplink is sufficient or a 10 Gigabit interface is necessary has to be decided individually.
Business access points with .11ac standard MIMO 2×2 are recommended because they need less than 12.4 watts and can therefore operate according to the common 802.3af standard via PoE. 802.11ac access points with 3×3 or 4×4 MIMO are not recommended because these need up to 21 watts requiring the mandatory conversion of the PoE infrastructure to work correctly. Access points with 3×3 or 4×4 MIMO can in theory be installed on PoE switches with a 12.4 watt capacity, however the performance of these devices drop, as they would switch to an “emergency program mode” which would only allow them to use 2×2 MIMO. Moreover, 3×3 and 4×4 MIMO access points have higher electricity costs of up to 25€ per year.
If the customer wishes to take a network that has currently been operating on the 2.4 GHz band and convert it to an .11ac 5 GHz network, then a new site survey would be necessary.
First of all, the channel bandwidth has to be determined. Every administrator tries to achieve the best performance from hardware and tends therefore to set up the best possible channel bandwidth (e.g.80 MHz). Nevertheless, in wireless LAN infrastructure with several access points, it has to be taken into account that the same radio channel can be used by several access points but you have to ensure that the field strength of the reused channel at the installed site of the access point is already low enough. To put it more simply: The access points using the same channel have to be far apart from each other.
Teldat’s current access points can be integrated without any problems in already existing installations, and even without large investments. Compared to access points with MIMO 3×3 or MIMO 4×4, Teldat’s devices with MIMO 2×2 have technological advantages. At this time, an investment of MIMO3x3 or MIMO 4×4 access points do not make sense yet because only few terminal devices support this technology. In particular, caution should be taken with low cost devices from the consumer market because these devices very rarely support DFS channels in the 5 GHz area which is extremely important for an .11ac installation, due to the shortage of channels available in the 5GHz network.
Hans-Dieter Wahl: WLAN Business Line Manager
We are surrounded by waves: radar, radio, mobile telephone, Wi-Fi etc., all occupying an established man-made order and based on invisible highways known as frequency bands.
Wi-Fi technology, on the whole, uses 2.4 and 5 GHz bands, a small part of the electromagnetic spectrum divided into a series of channels, over which information flows (like traffic on a freeway). Channel distribution is regulated by legal standards (set up by the USA, Europe, Japan, etc.) to guarantee interoperability between devices emitting waves and prevent interference with others.
802.11n technology and its limitations
The most widely-known Wi-Fi technology is 802.11n. Products using this technology can operate over both bands using 20MHz wide channels.
Channel width is very significant. The greater the width, the better the information transfer rate and, as a result, the faster the connections. However, having a wider channel has its drawbacks: it means increased radio frequency space occupation within a band.
802.11n offers the possibility of operating at a higher speed through channel bonding: joining two 20MHz bands to make one of 40.
This option is easy to accomplish in a 5GHz band, where there are many channels and little operating equipment (although new devices are beginning to ‘colonize’ this area), yet extremely difficult in 2.4GHz. There are only 13 20MHz channels in 2.4GHz, which quickly become congested due to many devices that, in turn, generate interferences. Thus, it’s practically impossible to connect to 40MHz channels in that frequency band.
As expected, it was merely a matter of waiting for new generation technologies, such as 802.11ac, to evolve and improve channel width with the prospect of far better features.
And so it did, with 802.11ac being the first. This technology, operating over 5GHz only, is able to use 20, 40, 80 and so on…up to 160MHz channels!
5GHz, however, is limited in space. Only n channels can fit, depending on their width. In Europe, for example, there are 20-25 20MHz channels, 8-12 40MHz and only 1-2 160MHz. In other words, the same problem rears its head.
So is 802.11ac the answer?
What first drew our attention to this was the new 802.11ac wave 2 Access Points, which offer radio performance of up to 3.5 Gbps, 4 flows and 160MHz channels. Unfortunately, this tends to be restricted to laboratory conditions.
This is because, with so few 160MHz channels available, APs interfere with each other and degrade the signal. So much so, in fact, that network designers have opted for narrower channels: 80MHz, up to 40 in high density areas, to offer users quality connections.
In the end, despite appearing to be the ideal solution for wireless offices and allowing for quality multimedia content distribution, 802.11ac and 802.11n face similar problems. Published transfer rates are never achieved in real life situations (offices) and any improvement to them would need case by case analysis and research on radio distribution.
However, 802.11ac not only has wider channels, it also offers significant technical innovations in just its basic version (wave 1). These include QAM256 modulation, which triples the bandwidth being offered to customers so far and improves MIMO technologies significantly. So far an Access Point could be a Single User MIMO 3×3, or even a 4×4, without tapping into its full potential as there are few terminals on the market that support this. The second version, 802.11ac Wave 2, is a Multiuser MIMO: for the first time an Access Point can simultaneously serve different traffic flows to different users (an AP MIMO4x4 can speak to two portable MIMO2x2 at the same time), and considerably improve net transfer rate to various terminals.
In short, 802.11ac offers users tangible improvements, despite channel difficulties. This solution is here to stay as it provides wireless connectivity services with a quality and performance, which, up until now, was only achieved through cable.
It’s along this technological path Teldat’s putting in considerable time and effort. Not only have we got 802.11ac products already on the market, but are also working in parallel to offer our customers the most competitive solutions as these evolve.
Francisco Navarro: Francisco Navarro, graduated in Physical Science, is a Business Line Manager working within the Marketing Department and responsible for the Teldat Corporate Routers.
The definition of new wireless LAN standards is a continuous process for creating, as well as improving applications and for making them more secure.
The best-known wireless LAN standards by IEEE are certainly 802.11n for wireless LAN applications up to 600 Mbit/s and of course the 802.11ac standards which have recently been introduced into the market, allowing applications up to 6.7 Gbps. Furthermore, this new standard exploits the streams in use more effectively (key word multi-user MIMO).
Wi-Fi HaLow with IEEE 802.11ah is defined by the terms low-power and long range. This standard will no longer use the usual 2.4 and 5 GHz frequency bands but a license free band below 1 GHz. The respective frequency band is country-specific. In Europe, the frequency range between 868 and 868.6 is reserved for 802.11ah. Due to the significantly smaller frequency used by the mentioned standard compared to the current 2.4 GHz, the free space loss is considerably lower, allowing double range compared to 2.4 GHz. Moreover, the new standard will penetrate walls, ceilings or similar obstacles much more easily. A more detailed look into the new standard reveals elements which are well-known from the .11ac standard, such as multi-user MIMO and single-user beamforming. Also the modulation types are already known, DPSK (differential phase shift keying) and QPSK (quadrature phase shift keying) range between 16 and 256 QAM (quadrature amplitude modulation).
Unfortunately, only 1 MHz and 2MHz radio channels are planned for the new .11ah standard. The .11ac standard defines channels with a width of 20, 40, 80 and 160 MHz. Thus, even though the range of .11ah devices will be good, the transmission rates are more geared towards applications with lower transmission rates. The small channel bandwidth enables low power consumption, thus, the new standard is perfectly suitable for battery-powered devices. Marketing strategies for the new standard focus on applications in this context. Therefore, 802.11ah is the standard used for IoT (Internet of Things), Smart Home, connected car applications, digital healthcare and many other applications.
The standard has only just been approved and published recently on 4th January 2016. It will therefore be a while until the first .11ah devices are offered on the market. Moreover, in order to guarantee an interoperability between different manufactures, the WiFi Allicance offers a certification program for 802.11ah-based devices.
ZigBee , the alternative
For those who do not want to wait so long, ZigBee can also be a very interesting alternative and it is also designed for high ranges and low data rates. Zigbee operates on the 2.4 GHz band, it is already available and has an attractive price. Indeed, numerous applications in home automation and industry are in use, thanks to ZigBee.
I am curious to see what will actually happen. Will the new .11ah standard eventually establish itself or will it only be used in niche applications. It will definitely take some more time until the 802.11ah is put into practice. However, the constantly increasing demands for wireless LAN bandwidth make this technology a very promising and interesting topic and will continue to draw our attention in the future. As an innovative manufacturer of wireless LAN devices, Teldat is of course looking forward to the future developments.
Hans-Dieter Wahl: WLAN Business Line Manager