802.11ac: all you need to know about the new standard Wi-Fi

The first network device based on 802.11ac is now on sale, and very soon in front of every user there will be a question that whether or not to overpay for a new version of Wi-Fi? Answers to questions about the new technology can be found in this below information regarding the 802.11ac.

802.11ac – background

The last officially approved version of the standard (802.11n), was in development from 2002 to 2009, but its so-called draft version (draft) was adopted in 2007, and like many of you probably remember, routers with support for 802.11n draft can be found in the sale almost immediately after the event.

5G Wi-Fi logo 802.11ac

The developers of routers and other Wi-Fi devices then did absolutely right, without waiting for approval of the final version of the protocol. This allowed them for 2 years before release devices that provide data rates up to 300 Mb / s, and when the standard was finally captured and the first 100% standards-routers, the old modules interoperability is not lost due to follow a rough version of the standard, ensuring compatibility at the hardware level (minor differences can be resolved with firmware update).

With 802.11ac now repeats almost the same story that was with 802.11n. Dates of adoption of the new standard still uncertain (probably not before the end of 2013), but has adopted draft specification is likely to ensure that all devices are released in the future without problems to earn a certified wireless networks.

Until recently, each new version has added to the end of 802.11 new letter (eg, 802.11g), and they grew in alphabetical order. However, in 2011 this tradition was little break and jumped from version 802.11n directly to 802.11ac.

Draft 802.11ac was adopted in October last year, but the first commercial device based on it has appeared just in the past few months. For example, Cisco has released its first router that supports 802.11ac the end of June 2012.

Improvements in 802.11ac

We can definitely say that even the 802.11n has not yet had time to reveal itself in some practical problems, but this does not mean that progress should be in place. In addition to higher data rates, which can be activated only after a few years, every improvement in Wi-Fi brings other benefits: improved signal stability, increased range of coverage, reduced power consumption. All of the above is true for 802.11ac, so here dwell on each item detail.

802.11ac refers to the fifth generation of wireless networks, and in the spoken language can be fixed for him the name of the 5G Wi-Fi, although officially it is not true. In developing this standard, one of the main objectives was put to achieve gigabit transfer rate. While the use of additional, as a rule, is not involved channels to disperse, even 802.11n to an impressive 600 MB / s (you will use four channels, each of which operates at a speed of 150 Mb / s).

Specified speed (gigabit) it was decided not to take any price, and maintaining compatibility with earlier versions of the standard. This means that in mixed networks, all devices will work regardless of which version they support 802.11.

To achieve this goal 802.11ac will continue to operate at a frequency of up to 6 GHz. But if the 802.11n for this purpose once the two frequencies (2.4 and 5 GHz), and in earlier revisions of only 2.4 GHz, the low frequency AC crossed out and leave only the 5 GHz band, since it is more efficient for data transfer.

The last remark may seem somewhat contradictory, because at 2.4 GHz signal is better distributed over long distances, effectively bypassing the obstacle. However, this range is already occupied by a huge number of “household” waves (from the Bluetooth devices to microwave ovens and other home electronics), and its application in practice, only worsens the outcome.

Another reason for the rejection of 2.4 GHz was the fact that in this range is not enough for spectrum to accommodate a sufficient number of channel bandwidth in the 80-160 MHz each.

It should be emphasized that despite the different operating frequencies (2.4 and 5 GHz), IEEE AC audit ensures compatibility with earlier versions of the standard. How this is achieved is not explained in detail, but most likely, the new chips will use the 5 GHz frequency as the base, but when you work with older devices that do not support this range will be able to switch to a lower frequency.

Speed of 802.11ac

The speed increase in 802.11ac will be obtained through several changes. First of all by doubling the bandwidth of the channel. If the 802.11n has already been increased from 20 to 40 MHz, the 802.11ac be as much as 80 MHz (default), and in some cases, and 160 MHz.

In earlier versions of 802.11 (up to N specifications), all data transmitted only in one stream. In N, the number may be 4, although it is still often used; only 2 channel. In practice, this means that the total maximum rate is calculated as the product of the maximum speed of each channel to their number. (802.11n 150 x 4 = 600 MB / s)

In 802.11ac, now the number of channels increased to 8, and the maximum transfer rate in each case can be found, depending on their width. At 160 MHz is obtained 866 Mb / s, and multiplying that number by 8, we obtain a theoretical maximum speed that can provide a standard that is nearly 7 Gb / s, which is 23 times faster than that given by 802.11n.

GB / s and even more so the 7-gigabit data rates initially are able to provide but not in all of the chips. The first models of routers and other Wi-Fi device will work at more modest speeds.

For example, the above-mentioned first Cisco router 802.11ac though surpasses the capabilities of 802.11n, yet also not out of the gigabit range, showing only 866 MB / s. In this case we are talking about the older of the two available models, and the youngest only provides 600 MB / s.

However, significantly lower than those of speed and will not fall even in the most entry-level devices, because the minimum data rate, according to the specifications for the AC is 450 MB / c.
Economical power consumption
Economical energy expenditure will be one of the greatest strengths of AC. Chips based on this technology are already predicting all mobile devices, arguing that this would increase the autonomy not only equal, but at a higher data rate.

Unfortunately, before the release of the first devices to obtain more accurate figures are unlikely to succeed, and when the new models will be on hand to compare the increased autonomy can be only approximate, because the market is unlikely to be a smartphone two identical, differing only in the wireless module. It is expected that large quantities such devices will start to appear on sale towards the end of 2012, although the first signs are already visible on the horizon, such as a laptop Asus G75VW, introduced in early summer.

According to Broadcom, the new devices are up to 6 times energy efficient when compared with their counterparts on the basis of 802.11n. Most likely, the manufacturer of networking equipment refers to some exotic test conditions, and the average savings figure is much lower here, but still much to be manifested in the form of extra minutes and possibly hours of mobile devices.

Increased autonomy, as often happens, is not in this case, a marketing ploy, as a direct consequence of the peculiarities of the technology. For example, the fact that the data will be transmitted at high speed is already a reason for the reduction of energy consumption. Since the same amount of data can be obtained in less time, the wireless module will be turned off earlier and, therefore, cease to apply to the battery.


Formation of directional signal (Beam-forming)

This technique could be applied in signal even in 802.11n, but at the moment it is not standardized, and the use of network equipment from different manufacturers, it is usually worked incorrectly. In all aspects of 802.11ac is standardized, so it will be applied in practice more often, although still optional.

Named method solves the problem of falling signal strength caused by its reflection from various objects and surfaces. Upon reaching the receiver, all these signals come from the phase shift, and thus reduce the total amplitude.

Beam-forming solves this problem as follows. The transmitter determines the estimated location of the receiver and, guided by this information, generates a signal in an unusual way. During normal operation, the signal from the receiver diverges uniformly in all directions, and at beam-force directed at a specific direction, which is achieved by using multiple antennas.

Beam-forming not only improves signal propagation in open territory, but also helps to “break through” the wall. If the router is not used to “took out” in the next room, or provide an extremely volatile relationship at low speed, the quality of reception with AC in the same point will be much better.

802.11ad, as well as 802.11ac, has a second, easier to remember, but the unofficial name – WiGig.

Despite its name, this specification will not be following the 802.11ac. Both technologies were developed simultaneously, and the main purpose (to overcome the gigabit barrier) they have one. Different approaches only. If AC strives to maintain compatibility with previous developments, the AD begins with a blank sheet of paper, which greatly simplifies its implementation.

The main difference between the competing technologies will be the operating frequency, from which follow all the other features. For AD, it is much higher compared to AC and 6 GHz instead of the 5 GHz band.

In this regard, the working range (signal coverage) is also reduced, but it will be much less interference, as the 60 GHz are used less frequently compared with an operating frequency 802.11ac, not to mention the 2.4 GHz band.

At what distance is 802.11ad devices will see each other, is difficult to say. Without specifying figures, official sources said the “relatively small distances in the same room.” The absence of the signal path of the walls and other serious obstacles is also mandatory and a prerequisite for the job. Obviously, we are talking about a few meters away, and symbolically, if the limit would be the same limitation as for Bluetooth (10 meters).

The small radius of transmission will be the reason that the AC and AD technology will not interfere with each other. While the first focuses on wireless networks for homes and offices, then the second will be used for other purposes. Which is, the question still open, but there are rumours that AD finally will replace Bluetooth, which cannot cope with their responsibilities because of the extremely low by today’s standards, the data rate.

The standard also is positioned to “replace wired connections” – it is possible that in the near future it will be known as “Wi-Fi USB” and will be used to connect printers, hard drives, perhaps, monitors and other peripherals.

The current version of the Draft AD has surpassed its original goal (1 GB / s), and the maximum data rate it is 7 GB / s. At the same technology used allows improving these figures, while remaining within the standard.


What is 802.11ac? for ordinary users

It is unlikely at the time of standardization of technologies ISPs will have to offer service plans for the disclosure of which require the power of 802.11ac. Consequently, the actual use of a high-speed Wi-Fi at first can be found only in home networks: fast transfer of files between devices, viewing HD-movies while simultaneously loading the network with other tasks, back up data to external hard drives that are connected directly to the router.

802.11ac not only solves the problem with speed. A large number of devices connected to the router now can create problems, even if the bandwidth of the wireless network is not used to the maximum. Given that the number of devices in each family will continue to grow, to think over the problem have now, and AC is a solution, allowing a network to work with a large number of wireless devices.

AC is spreading among all of the mobile devices. If the new chip will provide at least a 10% increase in autonomy, its use is fully justified even with a small increase in the price of the device. The first smart phones and tablet technology-based AC, probably worth the wait towards the end of the year. As already mentioned, a laptop with 802.11ac already released, but how much we know, this is still the only model on the market.

As expected, the cost of the first AC-router proved to be quite high, and prices plummet in the coming months is hardly worth the wait, especially when you consider how the situation evolved to 802.11n. However, as early as next year, the routers will cost less than $ 150-200, which manufacturers are asked for their first models right now.

According to the leakage of information in small doses, Apple has once again will be among the early adopters of new technology. Wi-Fi has always been a key interface for all devices of the company, for example, 802.11n found its way into Apple equipment immediately after approval of Draft specification in 2007, it is not surprising that 802.11ac is also preparing for an early debut in the part of many devices Apple: laptops, Apple TV, AirPort, Time Capsule, and perhaps, iPhone / iPad.

In conclusion, it is worth recalling that all these speeds are the maximum theoretically achievable. And just as 802.11n actually slower 300 MB / s, the actual speed limit for the AC will be lower than what is specified on the device.

Performance in each case will depend heavily on the equipment used; the presence of other wireless devices, the configuration space, but tentatively, the router that says 1.3 GB / s cannot transmit information faster than 800 MB / s (which is still considerably higher than the theoretical maximum 802.11n).
The maximum speed for a single channel

channel 801.11ac



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