802.11ac: what we need to know about the new standard Wi-Fi
On the shelves are full of new devices based on 802.11ac, which are already on sale, and very soon, each user will be asked if it is worth to overpay for a new version of Wi-Fi? I will try to highlight the answers to the questions concerning the new technology in this article.
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 was adopted in 2007, and as many probably remember, routers supporting 802.11n draft can It was found on sale almost immediately after the event.
')
The developers of routers and other Wi-Fi devices arrived then quite right, without waiting for the approval of the final version of the protocol. This allowed them to release devices for 2 years earlier, providing data transfer rates of up to 300 Mb / s, and when the standard was finally captured on paper and the first 100% standardized routers appeared, the old modules did not lose compatibility by following the draft version providing compatibility at the level of iron (minor differences could be resolved by updating the firmware).
With 802.11ac, the story is almost the same as it was with 802.11n. The timing of the adoption of the new standard is still not exactly known (presumably not earlier than the end of 2013), but the already adopted draft specification is likely to ensure that all devices now released will work without any problems with certified wireless networks.
Until recently, each new version added a new letter (for example, 802.11g) at the end of the 802.11 standard, and they increased in alphabetical order. However, in 2011, this tradition was slightly violated and jumped from the 802.11n version immediately to 802.11ac.
Draft 802.11ac was adopted last October, but the first commercial devices based on it appeared literally in the last few months. For example, Cisco released its first 802.11ac router at the end of June 2012.
802.11ac enhancements
You can definitely say that even 802.11n has not yet had time to reveal itself in some practical tasks, but this does not mean that progress should stand still. In addition to a higher data transfer rate, which can only be used in a few years, each Wi-Fi improvement brings other benefits: increased signal stability, increased coverage, lower power consumption. All of the above is also true for 802.11ac, so below we will focus on each item in more detail.
802.11ac belongs to the fifth generation of wireless networks, and in the spoken language it can be fixed to the name 5G WiFi, although officially it is incorrect. When developing this standard, one of the main goals was to achieve a gigabit data transfer rate. While the use of additional channels, usually not yet involved, allows even 802.11n to be dispersed to an impressive 600 Mb / s (for this purpose 4 channels will be used, each of which operates at 150 Mb / s), the gigabit bar for it and will not take, and this role will go to his successor.
It was decided to take the indicated speed (one gigabit) not at any cost, but with preservation of compatibility with earlier versions of the standard. This means that in mixed networks, all devices will work regardless of which version of 802.11 they support.
To achieve this goal, 802.11ac will still operate at up to 6 GHz. But if in 802.11n two frequencies were used for this at once (2.4 and 5 GHz), and in earlier revisions only 2.4 GHz, in AC, the low frequency is crossed out and only 5 GHz will be left, since it is more efficient for data transmission.
The last remark may seem somewhat contradictory, since at 2.4 GHz the signal propagates better over long distances, more efficiently bending around obstacles. However, this range is already occupied by a huge amount of “domestic” waves (from Bluetooth devices to microwave ovens and other home electronics), and in practice its use only worsens the result.
Another reason for the refusal of 2.4 GHz was the fact that there is not enough spectrum in this band to accommodate a sufficient number of channels 80-160 MHz wide each.
It should be emphasized that, despite the different operating frequencies (2.4 and 5 GHz), IEEE ensures that the AC revision is compatible with earlier versions of the standard. How this is achieved is not explained in detail, but most likely, new chips will use 5 GHz as the base frequency, however, when working with old devices that do not support this range, they will be able to switch to lower frequencies.
Speed
A noticeable speed increase in 802.11ac will be obtained through several changes at once. First of all, by doubling the channel width. If in 802.11n it has already been increased from 20 to 40 MHz, then in 802.11ac it will be as much as 80 MHz (by default), and in some cases 160 MHz.
In earlier versions of 802.11 (up to N specifications), all data was transmitted only in one stream. In N, their number can be 4, although so far only 2 channels are most often used. In practice, this means that the total maximum speed is calculated as the product of the maximum speed of each channel by their number. For 802.11n, we get 150 x 4 = 600 Mb / s.
The 802.11ac went further. Now the number of channels has been increased to 8, and the maximum possible transmission rate in each case can be found out depending on their width. At 160 MHz, 866 MB / s is obtained, and, multiplying this figure by 8, we obtain the maximum theoretical speed that the standard can provide, that is, almost 7 Gb / s, which is 23 times faster than 802.11n.
Gigabit, and even more so the 7-gigabit data transfer rate, at first, not all chips can provide. The first models of routers and other Wi-Fi devices will operate at more modest speeds.
For example, the first Cisco 802.11ac router, although it exceeds the capabilities of the 802.11n, nevertheless, also did not get out of the “doggit” range, demonstrating only 866 MB / s. In this case we are talking about the older of the two available models, and the youngest provides only 600 MB / s.
However, the speeds will also not noticeably fall even in the devices of the initial level itself, since the minimum possible data transfer rate, according to the specifications, is 450 Mb / s for AC.
Energy saving
The economical use of energy will be one of the greatest strengths of AC. Chips based on this technology are already predicting to all mobile devices, arguing that this will increase autonomy not only with equal, but also with a higher data transfer rate.
Unfortunately, before the release of the first devices, it is unlikely that more accurate figures will be obtained, and when the new models are on hand, the increased autonomy can only be compared approximately, since the market is unlikely to have two identical smartphones differing only in a wireless module. It is expected that massively such devices will begin to appear on sale closer to the end of 2012, although the first signs are already visible on the horizon, for example, the Asus G75VW laptop, introduced at the beginning of summer.
According to Broadcom, new devices are up to 6 times more energy efficient when compared to their 802.11n-based counterparts. Most likely, the manufacturer of network equipment refers to some kind of exotic testing conditions, and the average savings will be much lower than this, but it should still be noticeable in the form of additional minutes, and possibly mobile operating hours.
Increased autonomy, as is often the case, is not in this case a marketing ploy, since it directly follows from the features of the technology. For example, the fact that data will be transmitted at a higher speed is already a reason for reducing energy consumption. Since the same amount of data can be obtained in less time, the wireless module will be disconnected earlier and, therefore, will no longer access the battery.
Formation of a directional signal (Beamforming)
This signal conditioning technique could have been used in 802.11n, but at that time it was not standardized, and, as a rule, using network equipment from different manufacturers, it worked incorrectly. In 802.11ac, all aspects of the work of beeforming are unified, so it will be used more often in practice, although it still remains optional.
The named technique solves the problem of a drop in the signal power caused by its reflection from various objects and surfaces. Upon reaching the receiver, all these signals come with a phase shift, and thus reduce the total amplitude.
Bimforming solves this problem as follows. The transmitter approximately determines the location of the receiver and, guided by this information, generates a signal in an unusual way. In normal operation, the signal from the receiver diverges evenly in all directions, and during bimforming it is directed in a strictly defined direction, which is achieved with the help of several antennas.
Bimforming not only improves the distribution of the signal in an open area, but also helps to “pierce” the walls. If earlier the router is not
If you “got” into the next room or provided an extremely unstable connection with low speed, then with AC the reception quality at the same point will be much better.
802.11ad
802.11ad, as well as 802.11ac, has a second, easier to remember, but unofficial name is WiGig.
Despite the name, this specification will not be next to 802.11ac. Both technologies began to develop simultaneously, and their main goal (to overcome the gigabit barrier) is the same. Different only approaches. If AC seeks to maintain compatibility with previous developments, then AD begins with a clean sheet of paper, which greatly simplifies its implementation.
The main difference between the rival technologies will be the working frequency, from which all other features follow. For AD, it is an order of magnitude higher than AC and is 60 GHz instead of 5 GHz.
In this regard, the working range (covered by the signal) will also decrease, but it will have much less interference, since 60 GHz is used less frequently than the working frequency 802.11ac, not to mention 2.4 GHz.
At what distances the 802.11ad devices will see each other is difficult to say. Without specifying the figures, official sources talk about "relatively small distances within the same room." The absence of walls and other serious obstacles on the way is also a necessary and necessary condition for work. Obviously, we are talking about a few meters, and it is symbolic if the limit would be the same restriction as for Bluetooth (10 meters).
The small radius of the transmission will cause the AC and AD technologies not to conflict with each other. If the former is aimed at wireless networks for homes and offices, then the latter will be used for other purposes. In which, the question is still open, but there are already rumors that AD will finally replace Bluetooth, which is unable to cope with its duties due to the extremely low data transfer rate by today's standards.
The standard is also positioned to “replace wired connections” - it is quite possible that in the near future it will become known as “wireless USB” and will be used to connect printers, hard drives, and possibly monitors and other peripherals.
The current Draft version of AD is already ahead of its original goal (1 Gb / s), and the maximum data transfer rate in it is 7 Gb / s. In this case, the technology used allows to improve these indicators, while remaining within the standard.
What 802.11ac means for ordinary users
It is unlikely that by the time of technology standardization, Internet service providers will already start offering tariff plans, the disclosure of which requires the power of 802.11ac. Consequently, the real application of faster Wi-Fi can be found at first only in home networks: fast transfer of files between devices, watching HD movies while simultaneously downloading other tasks to the network, backing up data to external hard drives connected directly to the router.
802.11ac not only solves the problem with speed. A large number of devices connected to the router can now create problems, even if the bandwidth of the wireless network is not used to the maximum. Given that the number of such devices in each family will only grow, it is necessary to think about the problem now, and AC is its solution, allowing one network to work with a large number of wireless devices.
The fastest AC will spread in the environment of mobile devices. If the new chip provides at least a 10% increase in autonomy, its use will fully justify itself even with a slight increase in the price of the device. The first smartphones and tablets based on AC technology are likely to wait closer to the end of the year. As already mentioned, a laptop with 802.11ac has already been released, but as far as is known, this is still the only model on the market.
As expected, the cost of the first AC routers was quite high, and the sharp fall in prices in the coming months is hardly worth the wait, especially if you remember how the situation evolved with 802.11n. However, early next year, routers will cost less than $ 150-200, which manufacturers are asking for their first models right now.
According to leaking small doses of information, Apple will once again be among the first adherents of the new technology. Wi-Fi has always been a key interface for all devices of the company, for example, 802.11n found its way into the Apple technology immediately after the approval of the Draft specification in 2007, so it is not surprising that 802.11ac is also preparing for an early debut as part of many Apple devices: laptops, Apple TV, AirPort, Time Capsule, and possibly iPhone / iPad.
In conclusion, it is worth recalling that all the mentioned speeds are the most theoretically achievable. And just like 802.11n actually runs slower than 300 Mb / s, the real speed limits for AC will also be lower than what is indicated on the device.
The performance in each case will strongly depend on the equipment used, the availability of other wireless devices, the configuration of the room, but roughly, a router with a 1.3 Gb / s capacity can transmit information no faster than 800 Mb / s (which is still noticeably higher than the theoretical maximum of 802.11n) .
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 was adopted in 2007, and as many probably remember, routers supporting 802.11n draft can It was found on sale almost immediately after the event.
')
The developers of routers and other Wi-Fi devices arrived then quite right, without waiting for the approval of the final version of the protocol. This allowed them to release devices for 2 years earlier, providing data transfer rates of up to 300 Mb / s, and when the standard was finally captured on paper and the first 100% standardized routers appeared, the old modules did not lose compatibility by following the draft version providing compatibility at the level of iron (minor differences could be resolved by updating the firmware).
With 802.11ac, the story is almost the same as it was with 802.11n. The timing of the adoption of the new standard is still not exactly known (presumably not earlier than the end of 2013), but the already adopted draft specification is likely to ensure that all devices now released will work without any problems with certified wireless networks.
Until recently, each new version added a new letter (for example, 802.11g) at the end of the 802.11 standard, and they increased in alphabetical order. However, in 2011, this tradition was slightly violated and jumped from the 802.11n version immediately to 802.11ac.
Draft 802.11ac was adopted last October, but the first commercial devices based on it appeared literally in the last few months. For example, Cisco released its first 802.11ac router at the end of June 2012.
802.11ac enhancements
You can definitely say that even 802.11n has not yet had time to reveal itself in some practical tasks, but this does not mean that progress should stand still. In addition to a higher data transfer rate, which can only be used in a few years, each Wi-Fi improvement brings other benefits: increased signal stability, increased coverage, lower power consumption. All of the above is also true for 802.11ac, so below we will focus on each item in more detail.
802.11ac belongs to the fifth generation of wireless networks, and in the spoken language it can be fixed to the name 5G WiFi, although officially it is incorrect. When developing this standard, one of the main goals was to achieve a gigabit data transfer rate. While the use of additional channels, usually not yet involved, allows even 802.11n to be dispersed to an impressive 600 Mb / s (for this purpose 4 channels will be used, each of which operates at 150 Mb / s), the gigabit bar for it and will not take, and this role will go to his successor.
It was decided to take the indicated speed (one gigabit) not at any cost, but with preservation of compatibility with earlier versions of the standard. This means that in mixed networks, all devices will work regardless of which version of 802.11 they support.
To achieve this goal, 802.11ac will still operate at up to 6 GHz. But if in 802.11n two frequencies were used for this at once (2.4 and 5 GHz), and in earlier revisions only 2.4 GHz, in AC, the low frequency is crossed out and only 5 GHz will be left, since it is more efficient for data transmission.
The last remark may seem somewhat contradictory, since at 2.4 GHz the signal propagates better over long distances, more efficiently bending around obstacles. However, this range is already occupied by a huge amount of “domestic” waves (from Bluetooth devices to microwave ovens and other home electronics), and in practice its use only worsens the result.
Another reason for the refusal of 2.4 GHz was the fact that there is not enough spectrum in this band to accommodate a sufficient number of channels 80-160 MHz wide each.
It should be emphasized that, despite the different operating frequencies (2.4 and 5 GHz), IEEE ensures that the AC revision is compatible with earlier versions of the standard. How this is achieved is not explained in detail, but most likely, new chips will use 5 GHz as the base frequency, however, when working with old devices that do not support this range, they will be able to switch to lower frequencies.
Speed
A noticeable speed increase in 802.11ac will be obtained through several changes at once. First of all, by doubling the channel width. If in 802.11n it has already been increased from 20 to 40 MHz, then in 802.11ac it will be as much as 80 MHz (by default), and in some cases 160 MHz.
In earlier versions of 802.11 (up to N specifications), all data was transmitted only in one stream. In N, their number can be 4, although so far only 2 channels are most often used. In practice, this means that the total maximum speed is calculated as the product of the maximum speed of each channel by their number. For 802.11n, we get 150 x 4 = 600 Mb / s.
The 802.11ac went further. Now the number of channels has been increased to 8, and the maximum possible transmission rate in each case can be found out depending on their width. At 160 MHz, 866 MB / s is obtained, and, multiplying this figure by 8, we obtain the maximum theoretical speed that the standard can provide, that is, almost 7 Gb / s, which is 23 times faster than 802.11n.
Gigabit, and even more so the 7-gigabit data transfer rate, at first, not all chips can provide. The first models of routers and other Wi-Fi devices will operate at more modest speeds.
For example, the first Cisco 802.11ac router, although it exceeds the capabilities of the 802.11n, nevertheless, also did not get out of the “doggit” range, demonstrating only 866 MB / s. In this case we are talking about the older of the two available models, and the youngest provides only 600 MB / s.
However, the speeds will also not noticeably fall even in the devices of the initial level itself, since the minimum possible data transfer rate, according to the specifications, is 450 Mb / s for AC.
Energy saving
The economical use of energy will be one of the greatest strengths of AC. Chips based on this technology are already predicting to all mobile devices, arguing that this will increase autonomy not only with equal, but also with a higher data transfer rate.
Unfortunately, before the release of the first devices, it is unlikely that more accurate figures will be obtained, and when the new models are on hand, the increased autonomy can only be compared approximately, since the market is unlikely to have two identical smartphones differing only in a wireless module. It is expected that massively such devices will begin to appear on sale closer to the end of 2012, although the first signs are already visible on the horizon, for example, the Asus G75VW laptop, introduced at the beginning of summer.
According to Broadcom, new devices are up to 6 times more energy efficient when compared to their 802.11n-based counterparts. Most likely, the manufacturer of network equipment refers to some kind of exotic testing conditions, and the average savings will be much lower than this, but it should still be noticeable in the form of additional minutes, and possibly mobile operating hours.
Increased autonomy, as is often the case, is not in this case a marketing ploy, since it directly follows from the features of the technology. For example, the fact that data will be transmitted at a higher speed is already a reason for reducing energy consumption. Since the same amount of data can be obtained in less time, the wireless module will be disconnected earlier and, therefore, will no longer access the battery.
Formation of a directional signal (Beamforming)
This signal conditioning technique could have been used in 802.11n, but at that time it was not standardized, and, as a rule, using network equipment from different manufacturers, it worked incorrectly. In 802.11ac, all aspects of the work of beeforming are unified, so it will be used more often in practice, although it still remains optional.
The named technique solves the problem of a drop in the signal power caused by its reflection from various objects and surfaces. Upon reaching the receiver, all these signals come with a phase shift, and thus reduce the total amplitude.
Bimforming solves this problem as follows. The transmitter approximately determines the location of the receiver and, guided by this information, generates a signal in an unusual way. In normal operation, the signal from the receiver diverges evenly in all directions, and during bimforming it is directed in a strictly defined direction, which is achieved with the help of several antennas.
Bimforming not only improves the distribution of the signal in an open area, but also helps to “pierce” the walls. If earlier the router is not
If you “got” into the next room or provided an extremely unstable connection with low speed, then with AC the reception quality at the same point will be much better.
802.11ad
802.11ad, as well as 802.11ac, has a second, easier to remember, but unofficial name is WiGig.
Despite the name, this specification will not be next to 802.11ac. Both technologies began to develop simultaneously, and their main goal (to overcome the gigabit barrier) is the same. Different only approaches. If AC seeks to maintain compatibility with previous developments, then AD begins with a clean sheet of paper, which greatly simplifies its implementation.
The main difference between the rival technologies will be the working frequency, from which all other features follow. For AD, it is an order of magnitude higher than AC and is 60 GHz instead of 5 GHz.
In this regard, the working range (covered by the signal) will also decrease, but it will have much less interference, since 60 GHz is used less frequently than the working frequency 802.11ac, not to mention 2.4 GHz.
At what distances the 802.11ad devices will see each other is difficult to say. Without specifying the figures, official sources talk about "relatively small distances within the same room." The absence of walls and other serious obstacles on the way is also a necessary and necessary condition for work. Obviously, we are talking about a few meters, and it is symbolic if the limit would be the same restriction as for Bluetooth (10 meters).
The small radius of the transmission will cause the AC and AD technologies not to conflict with each other. If the former is aimed at wireless networks for homes and offices, then the latter will be used for other purposes. In which, the question is still open, but there are already rumors that AD will finally replace Bluetooth, which is unable to cope with its duties due to the extremely low data transfer rate by today's standards.
The standard is also positioned to “replace wired connections” - it is quite possible that in the near future it will become known as “wireless USB” and will be used to connect printers, hard drives, and possibly monitors and other peripherals.
The current Draft version of AD is already ahead of its original goal (1 Gb / s), and the maximum data transfer rate in it is 7 Gb / s. In this case, the technology used allows to improve these indicators, while remaining within the standard.
What 802.11ac means for ordinary users
It is unlikely that by the time of technology standardization, Internet service providers will already start offering tariff plans, the disclosure of which requires the power of 802.11ac. Consequently, the real application of faster Wi-Fi can be found at first only in home networks: fast transfer of files between devices, watching HD movies while simultaneously downloading other tasks to the network, backing up data to external hard drives connected directly to the router.
802.11ac not only solves the problem with speed. A large number of devices connected to the router can now create problems, even if the bandwidth of the wireless network is not used to the maximum. Given that the number of such devices in each family will only grow, it is necessary to think about the problem now, and AC is its solution, allowing one network to work with a large number of wireless devices.
The fastest AC will spread in the environment of mobile devices. If the new chip provides at least a 10% increase in autonomy, its use will fully justify itself even with a slight increase in the price of the device. The first smartphones and tablets based on AC technology are likely to wait closer to the end of the year. As already mentioned, a laptop with 802.11ac has already been released, but as far as is known, this is still the only model on the market.
As expected, the cost of the first AC routers was quite high, and the sharp fall in prices in the coming months is hardly worth the wait, especially if you remember how the situation evolved with 802.11n. However, early next year, routers will cost less than $ 150-200, which manufacturers are asking for their first models right now.
According to leaking small doses of information, Apple will once again be among the first adherents of the new technology. Wi-Fi has always been a key interface for all devices of the company, for example, 802.11n found its way into the Apple technology immediately after the approval of the Draft specification in 2007, so it is not surprising that 802.11ac is also preparing for an early debut as part of many Apple devices: laptops, Apple TV, AirPort, Time Capsule, and possibly iPhone / iPad.
In conclusion, it is worth recalling that all the mentioned speeds are the most theoretically achievable. And just like 802.11n actually runs slower than 300 Mb / s, the real speed limits for AC will also be lower than what is indicated on the device.
The performance in each case will strongly depend on the equipment used, the availability of other wireless devices, the configuration of the room, but roughly, a router with a 1.3 Gb / s capacity can transmit information no faster than 800 Mb / s (which is still noticeably higher than the theoretical maximum of 802.11n) .
Source: https://habr.com/ru/post/149806/
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