Until now, many users are connected to the Internet via an Ethernet cable, but now laptops, tablets and smartphones, which simply need wireless Wi-Fi technology, have gained momentum. Earlier speed wireless connection left much to be desired, and reliability "limped". At the moment, all modern Wi-Fi adapters comply with the IEEE 802.11n standard, which allows you to transfer HD content over a wireless network, although the transfer of this type of data is not always comfortable on devices of this standard.
In theory, we have the following throughput devices:
- up to 150 Mbps when using 1 antenna
- up to 600 Mbps when using 4 antennas
On practice real speed 1.5 - 2 times lower than stated.
When choosing a router, first of all, rely on the support of the 802.11n Wi-Fi standard, as it is the most modern and is compatible with equipment of previous generations: 802.11 a, 802.11 b and 802.11 g. The next standard to replace 802.11n will be - 802.11ac or 5G wifi.
Currently available for purchase Wi-Fi 802.11ac-enabled network equipment, which manufacturers release on the market marked "draft". You will not experience any problems with device compatibility, especially since there was a similar story with the 802.11 n standard. The Wi-Fi 802.11n standard is now the most popular. Plus, he has not exhausted his potential. The transfer rate is sufficient for most users.
Benefits of a Wi-Fi 802.11ac Router
- high throughput
- long range
- reduced power consumption
One of the reasons for the appearance WiFi technology 802.11ac - Achieving 1Gbps throughput. Importantly, compatibility with previous generations of network equipment has been preserved. Wi-Fi 802.11 ac has been upgraded to 5 GHz to improve data transfer speeds. As you know, 802.11n devices operate at 2.4GHz. In order to combine technologies, 802.11ac Wi-Fi equipment is capable of switching to 2.4 GHz. Many have already seen for sale, and some are currently using dual frequency routers.
It is important to consider that radio waves at a frequency of 2.4 GHz is better bend around obstacles, thereby spreading over long distances, but this frequency range is subject to interference from various household appliances. In addition, in this frequency range it is not possible to place a sufficient number of channels with a width of 80-160 MHz each. Namely, a twofold increase in the channel width made it possible to increase the throughput of Wi-Fi 802.11ac technology. Based on this, the frequency of 5 GHz becomes a more rational option. Indeed, in addition to the increased width of the channels, their maximum amount- from 4 for the 802.11n Wi-Fi standard to eight for 802.11ac.
If we take into account that the bandwidth of one 160 MHz channel is 866 Mbps, then the peak data transfer rate of the Wi-Fi 802.11ac standard with 8 antennas is about 7 Gbps. For most Wi-Fi 802.11 ac enabled devices, the channel width will be limited to 80 MHz and the number of channels will be limited to three. As a result, we get a throughput of 1.3 Gbps.
What is beamforming?
Directional signal generation technology, so-called beamforming, appeared before the final specifications of Wi-Fi 802.11n were approved, but even with the transition to 802.11 ac, it remains optional. Nevertheless, beamforming itself is already a fully formed technology, which avoids problems with incompatibility. network equipment from different manufacturers. Beamforming is able to minimize signal attenuation after radio waves encounter various obstacles.
How the technology works
The transmitter determines the approximate location of the receiver and directs the signal to strictly given direction, which affects the increase in the range of points WiFi access, a prerequisite is only the presence of several antennas in the transmitter, directed in different directions.
Power consumption wi-fi 802.11 ac
Every smartphone or tablet user has experienced fast discharge mobile device battery during active use wireless connection. In theory wifi controllers 802.11ac consumes 6 times less power to transfer data at the same speed as 802.11n. In practice, the numbers are much more modest, but the results are noticeable. In addition, the increased bandwidth of 802.11ac Wi-Fi technology allows you to download data from the Internet faster and, when completed, the controller goes to sleep to reduce power consumption. In the near future, mobile devices(smartphones and tablets) will use energy-efficient 802.11ac Wi-Fi controllers with data transfer rates from 433 Mbps to 866 Mbps.
Wi-Fi controllers 802.11ac
Currently released 802.11ac Wi-Fi controllers support 1 to 4 80 MHz channels with a bandwidth of 433 Mbps each, so their peak data transfer rate is only 1.7 Gbps. Now you can buy wifi router with support for Wi-Fi 802.11ac, but, however, with a speed limited to 1.3 Gb / s from NETGEAR, TP-Link, D-Link, ASUS, Belkin and Buffalo.
The article describes the question of why built-in or external WiFi the module does not see the 5 GHz network.
What is the advantage of 5 GHz network compared to 2.4 GHz? For people living in apartment buildings next to other devices along the landing plus from above / below, this is, first of all, less “interference”. In addition, 23 separate transmission channels ... Such a network, of course, cannot boast of a similar coverage, but we can’t even catch a signal on the street. In general, we decided to set the router to a frequency of 5 GHz, however ...
What are the symptoms?
- or the newly purchased adapter does not see them
- or before that reception on both channels was confident, but now ...
- have you upgraded to Windows 10?
5 GHz network is not visible: the reason is the adapter
Let's start with how your adapter (with which you pick up the signal from the router) looks like from the point of view of the system. Let's use the command in cmd
netsh wlan show drivers
I highlighted the line I was looking for. Several scenarios are possible. If a Windows terminal returns the types of supported modules as a list:
- 802.11g and 802.11n - the module sees only 2.4 GHz networks
- 802.11ac– sees only 5 GHz networks
- 802.11a, 802.11g and 802.11n - 2.4 and 5 GHz networks are available
- 802.11n , 802.11g and 802.11b - the module sees only 2.4 GHz networks
Yes, regarding the 802.11n standard, there is a small snag here: it supports 5 GHz, only not all network adapters can support both standards. The problem is in the versions: there are two versions of 802.11n 2006 and 802.11n Dual Band 2009 .
Based on the following figure, the module built into the laptop does not support communication with the 5 GHz band (and most of them do). But this one sees a lot:
5 GHz network is not visible: the reason is in the router
Done with the adapter. You can try to find a more suitable driver version for installed card However, I'm afraid there's nothing you can do about it. But with a router, things are easier. Or harder. If you need a strong signal in both bands (in the hope of a confident and fast reception on the 5 GHz frequency), you should know about the support of those by your or future router. And if the router does not output a signal at 5 GHz, there are only two reasons:
- router is faulty
- Wi-Fi settings are simply wrong (disabled due to incorrect settings, but by default they should be exactly enabled)
Here I am no longer your assistant. Each of the routers has its own settings for the 5 GHz frequency. Some of the manufacturers include 5GHz reception right into the name (eg NetgearXXX and NetgearXXX-5G). the very same the right way find out - “google” the router model and find out from the help from the manufacturer or in the forum.
Can't see 5GHz network after Windows 10 upgrade
Well, this is a traditional problem for many devices: the drivers just don't fit. You can “play” with them by installing updated ones from the manufacturer’s website or rolling back to previous version. Sample Plan at work, I sketched in the article “ wifi error: limited access". And don't forget to disable automatic update drivers.
Wi-Fi - how much in this sound ... I think everyone knows that Wi-Fi is wireless the local network. And it would seem that Wi-Fi can be complicated, everything is simple, but it wasn’t enough, for example, to read the specification of the router. What is not written there IEEE802.11n, IEEE802.11b, IEEE802.11g,Frequency range 2.4 GHz, 5 GHz. To understand this, you need to have two higher educations in the field of IT. But in fact, everything is not as complicated as it seems, in this article I will try to explain what the numbers and numbers that accompany WiFi devices a.
So let's start with the IEEE standards (Institute of Electrical and Electronics Engineers) is an international non-profit association of specialists in the field of technology, a world leader in the development of standards for radio electronics and electrical engineering. The main goal of IEEE is standardization in the field of IT. So, in order to distinguish between standards, numbers are written after the IEEE abbreviation that correspond to a certain group of standards, for example:
- Ethernet is the standards of the IEEE 802.3 group
- WiFi is IEEE 802.11 group standards
- WiMAx are IEEE 802.16 group standards
| IEEE standard |
Technology name in English | Frequency range of networks, GHz | Year of WiFi alliance ratification | Theoretical throughput, Mbps |
|---|---|---|---|---|
| 802.11b | Wireless b | 2,4 | 1999 | 11 |
| 802.11a | Wireless a | 5 | 2001 | 54 |
| 802.11g | Wireless g | 2,4 | 2003 | 54 |
| Super G | 2,4 | 2005 | 108 | |
| 802.11n | Wireless N, 150Mbps | 2,4 | - | 150 |
| Wireless N Speed | 2,4 | - | 270 | |
| Wireless N, 300Mbps | 2,4 | 2006 | 300 | |
| Wireless Dual Band N | 2.4 and 5 | 2009 | 300 | |
| Wireless N, 450Mbps | 2.4/ 2.4 and 5 | - | 450 | |
| 802.11ac | wireless ac | 5 | - | 1300 |
This table shows that with each new standard, the speed of a Wi-Fi network is steadily increasing. If you see on any device (router, laptop, etc.) the inscription IEEE 802.11 b / g / n, this means that the device supports three standards 802.11b, 802.11g, 802.11n (at the time of this writing, this is the most popular combinations, since 802.11a is outdated and uses the 5 GHz frequency band, and 802.11ac has not yet gained much popularity).
It's time to understand the frequency ranges in which Wi-Fi networks operate, there are two of them - 2.4 GHz (more precisely, the frequency band 2400 MHz-2483.5 MHz) and 5 GHz (more precisely, the range 5.180-5.240 GHz and 5.745-5.825 GHz).
Most devices operate at 2.4 GHz, which means using the 2400 MHz-2483.5 MHz band with a 5 MHz step frequency. these bands form channels, for Russia there are 13 of them
Channel Lower frequency Center frequency Upper frequency
1
2.401 2.412
2.423
2
2.406 2.417
2.428
3
2.411 2.422
2.433
4
2.416 2.427
2.438
5
2.421 2.432
2.443
6
2.426 2.437
2.448
7
2.431 2.442
2.453
8
2.436 2.447
2.458
9
2.441 2.452
2.463
10
2.446 2.457
2.468
11
2.451 2.462
2.473
12
2.456 2.467
2.478
13
2.461 2.472
2.483
Frequency channels in the 5GHz spectral band:
| Channel | Frequency, GHz | Channel | Frequency, GHz | Channel | Frequency, GHz | Channel | Frequency, GHz | |||||||
| 34 | 5,17 | 62 | 5,31 | 149 | 5,745 | 177 | 5,885 | |||||||
| 36 | 5,18 | 64 | 5,32 | 15 | 5,755 | 180 | 5,905 | |||||||
| 38 | 5,19 | 100 | 5,5 | 152 | 5,76 | |||||||||
| 40 | 5,2 | 104 | 5,52 | 153 | 5,765 | |||||||||
| 42 | 5,21 | 108 | 5,54 | 155 | 5,775 | |||||||||
| 44 | 5,22 | 112 | 5,56 | 157 | 5,785 | |||||||||
| 46 | 5,23 | 116 | 5,58 | 159 | 5,795 | |||||||||
| 48 | 5,24 | 120 | 5,6 | 160 | 5,8 | |||||||||
| 50 | 5,25 | 124 | 5,62 | 161 | 5,805 | |||||||||
| 52 | 5,26 | 128 | 5,64 | 163 | 5,815 | |||||||||
| 54 | 5,27 | 132 | 5,66 | 165 | 5,825 | |||||||||
| 56 | 5,28 | 136 | 5,68 | 167 | 5,835 | |||||||||
| 58 | 5,29 | 140 | 5,7 | 171 | 5,855 | |||||||||
| 60 | 5,3 | 147 | 5,735 | 173 | 5,865 | |||||||||
Accordingly, in the Russian Federation we have the following non-overlapping channels with a width of 20 MHz indoors:
1.5150-5250MHz
36: 5180 MHz
40: 5200 MHz
44: 5220 MHz
48: 5240 MHz ( this channel effective if the next lane is used)
2.5250-5350MHz(Check if this band can be used)
52: 5260MHz
56: 5280 MHz
60: 5300 MHz
64: 5320 MHz
Due to the rarer use and large numbers of channels of Wi-Fi points, the speed wifi work increases. But to use 5GHz, it is necessary that not only wifi source(router) worked at this frequency, but also the device itself (laptop, tablet, phone, TV). The disadvantage of using 5GHz is the high cost of equipment, in comparison with devices operating at a frequency of 2.4 GHz, and a shorter range compared to 2.4 GHz.
There are more and more gadgets with Wi-Fi. 2.4 GHz networks already work poorly due to a large number devices? Did you notice it too? Even when using 1, 5, 9 and 13 channels, is it impossible to get an acceptable capacity and total network performance? Well, is there good news. The 5GHz band is almost completely free now. And besides, there are much more channels available for placing access points. As many as 19 to accommodate a width of 20 MHz with minimal crossover. Almost any Apple device can use 5GHz with 802.11A/N standard. In addition, it is in this range that they prefer to work if there is an opportunity to choose. The latest Wi-Fi standard 802.11AC can use 20/40/80MHz channel widths. New MacBooks prefer to work with a channel width of 80 MHz if possible. The 2.4 GHz band dried up in 2017 and new standard WiFi doesn't support it. Well, now there is a reason to promote the director to new access points with support for 802.11A / N / AC (just kidding). 802.11AC started appearing on Apple devices in 2013 and is now standard on all products. Soon other vendors will follow the company from Cupertino.
We will conduct a study of the compatibility of Wi-Fi devices with 5 GHz frequencies. At using an iPhone 5s c Mikrotik hAP AC lite, I noticed that it will not connect to the network when changing the frequency on the access point. At first I decided that this was not the right regionality, so I decided to write an appropriate article. Router Version OS 6.38.5
Let's go to MikroTik on the tab with interfaces and open wlan2. Let's choose the region Belarus.
I will show a screen with MikroTik frequency selection for our region. It's huge:
On the table, the possibility of connecting with all frequency options was tested. Ranges 5180-5320, 5500-5700 are allowed for use in our country. 19 non-overlapping channels 20 MHz wide (width) are in bold . For the unaited state 2 region, it is a secret to say that a range of 5705-5825 MHz is additionally offered. Apple iPhone 5s turned out to be able to work in it without changing the region (Belarus). As you can see, the frequency is enough for everyone :-)
Let's set the channel width to 20/40 MHz Ce and continue the study. It turned out to be interesting that the smartphone was able to connect to the network only in the range 5180-5320, 5500-5580. What is a software bug? Or wide channels in the ranges 5600-5700, 5705-5825 are prohibited in our region? In any case, this must be borne in mind. It turns out that we have only 6 and not 9 non-overlapping channels with a width of 40 MHz. After all, we want all devices to be able to work with a 5 GHz network, right?
Let's set the channel width to 20/40/80 MHz Ce. Now we were able to connect only when the access point frequency was set to 5180, 5260, 5500. In total, only 3 non-overlapping channels in which you can get maximum compatibility with the iPhone 5s configured for the Belarusian region.
When using a frequency of 5260-5580 MHz, you should pay attention that the Wi-Fi access point does not turn on immediately, but with a delay of 60 seconds. For 5600-5640, the delay is apparently even greater.
Judging by the inscription and recalling the history of the development of Router OS, it can be assumed that a search for radar signals is underway and if they are detected, the access point will not turn on. There is no such thing in the range 5705-5825.
Let me remind you that channels 12 and 13, which are allowed in our country for the 2.4 GHz band, cannot be used by some devices brought from other regions. The reverse situation is also possible: a device certified for our region may not connect to a range that is not allowed in our country. Macbook Air with the Belarusian region I could not see the network in the range 5600-5640 *, therefore, in order to ensure maximum compatibility with client devices, I advise you not to use these frequencies . You should also limit the use of channels with a width of 20/40 and 20/40/80 MHz only for 5120-5300, 5500-5580 MHz. This will allow all devices designed and certified for our region to connect (they are the majority, after all).
* - MacBook, unlike the iPhone, takes the region code using the outdated 802.11d protocol and is compatible with Wi-Fi networks may be different.
And for those who want their laptop to work even with networks that are incorrectly configured, we recommend in the settings network adapter select support for the entire frequency range. in the network control center and public access You can configure the Wi-Fi module:
According to the Belarusian legislation, it is not prohibited to use client devices that can operate in ranges not allowed in our country. But access points cannot be operated on the wrong frequencies.
p.s. What is the performance of 802.11AC? I have seen with my own eyes the throughput between the client and the access point up to 160 Mbps with a channel width of 80 MHz with a 1x1 MIMO scheme on SMB protocol. In the 802.11AC standard, not only frequencies and channel widths for certain regions are limited, but also different kind technology. In most CIS countries, beamforming technology that affects performance is prohibited.
Tutorial: How to set up MikroTik from scratch?
Learn to work with equipment MikroTik and RouterOS according to the video course "". Go through the lessons at a comfortable pace and when it is convenient - all materials remain with you indefinitely. The course includes 162 video lessons, 45 laboratory work, questions for self-examination and abstract. After completing the course, you will be able to set up a MikroTik router from scratch, even if you do not have real equipment available. You can watch the beginning of the course for free by leaving a request.
Read 20830 once Last modified Friday, 09 November 2018 17:22
I think I won’t be much mistaken if most of us have an Internet connection like this: there is some fairly high-speed wired channel to the apartment (now gigabit is not uncommon), and in the apartment he is met by a router that distributes this Internet to clients, giving them a “black” ip and performing address translation.Quite often, a strange situation is observed: with a high-speed wire, a very narrow wifi channel is heard from the router, which does not load even half of the wire. At the same time, although formally Wi-Fi, especially in its ac version, supports some huge speeds, when checking, it turns out that either Wi-Fi connects at a lower speed, or connects, but does not give out speed in practice, or loses packets, or all together.
At some point, I also encountered a similar problem, and decided to set up my Wi-Fi in a human way. Surprisingly, it took about 40 times longer than I expected. In addition, it somehow happened that all the instructions for Wi-Fi setup, which I found, converged to one of two types: in the first it was proposed to put the router higher and straighten the antenna, to read the second, I lacked an honest understanding of spatial multiplexing algorithms.
Actually, this note is an attempt to fill a gap in the instructions. I will say right away that the task has not been fully resolved, despite decent progress, the connection stability could still be better, so I would be glad to hear the comments of colleagues on the described topic.
Chapter 1:
So the problem statementThe Wifi router offered by the provider has ceased to cope with its duties: there are long (30 seconds or more) periods when the ping to the access point does not pass, very long (about an hour) periods are observed when the ping to the access point reaches 3500 ms, there are long periods when the connection speed with the access point does not exceed 200 kbps.
Scanning the range using the inSSIDer windows utility produces the picture presented at the beginning of the article. There are 44 Wifi SSIDs in the 2.4 GHz band and one network in the 5.2 GHz band in the district.
Solution tools
Celeron 430 self-assembly computer, 2b Ram, SSD, fanless, two wireless network cards on a Ralink rt2800pci chip, Slackware Linux 14.2, Hostapd from Git as of September 2016.
Assembling the router is beyond the scope of this post, although I note that the Celeron 430 performs well in fanless mode. I note that the current configuration is the latest, but not final. Perhaps there are still improvements to be made.
Solution
In fact, the solution would, in a good way, be to run hostapd with minimal configuration changes. However, experience confirmed the truth of the saying “it was smooth on paper, but forgot about the ravines” so well that it took the writing of this article to systematize knowledge about all the non-obvious details. Also, I initially would like to avoid low-level details for the sake of harmony of presentation, but it turned out that this is impossible.
Chapter 2
A bit of theoryFrequencies
WiFi is the standard wireless networks. From the point of view of OSI L2, the access point implements a switch type hub, but most often it is also combined with an OSI L3 switch of the “router” type, which leads to a fair amount of confusion.We will be most interested OSI layer L1, that is, in fact, the environment in which the packets go.
Wi-Fi is a radio system. As you know, a radio system consists of a receiver and a transmitter. AT wifi hotspot access and the client device perform both roles in turn.
The Wi-Fi transmitter operates on a certain frequency. These frequencies are numbered, and each number corresponds to a certain frequency. Important: despite the fact that for any integer there is a theoretical correspondence to this number of a certain frequency, Wi-Fi can only work in limited frequency bands (there are three of them, 2.4 GHz, 5.2 GHz, 5.7 GHz), and only on some of the numbers.
Full list You can see the correspondences in Wikipedia, but it is important for us that when setting up an access point, you need to specify on which channel the carrier frequency of our signal will be located.
An obscure detail: not all Wi-Fi standards support all frequencies.
There are two Wi-Fi standards: a and b. "a" is older and operates in the 5GHz band, "b" is newer and operates in the 2.4GHz band. At the same time, b is slower (11 mbit instead of 54 mbit, that is, 1.2 megabytes per second instead of 7 megabytes per second), and the 2.4 GHz band already accommodates fewer stations. Why this is so is a mystery. It is doubly a mystery why there are practically no standard access points in nature.
(Image borrowed from Wikipedia.)
(Actually, I'm being a little disingenuous, because a also supports the 3.7 GHz frequency band. However, I haven't seen a single device that knows anything about this band.)
Wait, you ask, but there are also 802.11g, n, ac - standards, and they seem to just beat the unfortunate a and b in speed.
But no, I will answer you. The g standard is a belated attempt to bring speed b to speed a, in the 2.4 GHz band. But why, you answer me, did you even remember about b? The answer is because even though the ranges of both b and g are called 2.4, they are actually slightly different, and the range of b is one channel longer.
The standards n and ac have nothing to do with ranges at all - they regulate the speed, and nothing more. Standard point n can be either "in the base" a (and operate at 5 GHz), or "in the base" b and operate at 2.4 GHz. I don’t know about the ac standard point, because I haven’t seen it.
That is, when you buy an access point n, you need to look very carefully at what ranges this n works in.
It is important that at one moment in time one wifi chip can only work in one range. If your access point claims that it can work in two at the same time, as, for example, they do free routers from popular providers Virgin or British Telecom, so it actually has two chips.
Channel Width
Actually, I have to apologize because I said earlier that one range is longer than another without explaining what "longer" is. Generally speaking, not only the carrier frequency is important for signal transmission, but also the width of the coded stream. Width - this is what frequencies above and below the carrier the existing signal can climb. Usually (and fortunately in Wi-Fi), the channels are symmetrical, centered on the carrier.So in Wi-Fi there can be channels with a width of 10, 20, 22, 40, 80 and 160 MHz. At the same time, I have never seen access points with a channel width of 10 MHz.
So, one of the most amazing properties of Wi-Fi is that despite the fact that the channels are numbered, they intersect. And not only with neighbors, but even with channels through 3 from yourself. In other words, in the 2.4 GHz band, only access points operating on channels 1, 6, and 11 do not intersect with 20 MHz streams. In other words, only three access points can work side by side so as not to interfere with each other.
What is an access point with a channel width of 40 MHz? The answer is - and this is an access point that occupies two channels (non-overlapping).
Question: and how many channels with a width of 80 and 160 MHz fit in the 2.4 GHz band?
Answer: No one.
The question is, what affects the width of the channel? I do not know the exact answer to this question, I could not check it.
I know that if the network intersects with other networks, the connection stability will be worse. Channel width of 40 MHz gives more crossovers and worse connection. According to the standard, if there are other working access points around the point, the 40 MHz mode should not be enabled.
Is it true that twice the channel width gives twice the bandwidth?
It seems to be, but it is impossible to verify.
Question: If my access point has three antennas, is it true that it can create three spatial streams and triple the connection speed?
Answer: unknown. It may turn out that three antennas, two can only be engaged in sending, but not receiving packets. And the signal speed will be asymmetrical.
Question: So how many megabits does one antenna give?
Answer: You can see here en.wikipedia.org/wiki/IEEE_802.11n-2009#Data_rates
The list is strange and non-linear.
Obviously the most important parameter- this is the MCS-index, which determines the speed.
Question: Where do these strange speeds come from?
Answer: There is such a thing as HT Capabilities. These are optional chips that can slightly correct the signal. Chips are very useful: SHORT-GI adds a little speed, about 20 Mbps, LDPC, RX STBC, TX STBC add stability (that is, they should reduce ping and packet loss). However, your hardware may simply not support them and still be quite “honest” 802.11n.
Signal strength
The easiest way to deal with bad connection- is to fry more power into the transmitter. Wi-Fi has a transmission power of up to 30 dBm.Chapter 3
The solution of the problemFrom all of the above vinaigrette, it would seem that the following conclusion can be drawn: Wi-Fi can implement two “modes” of functioning. “Improving speed” and “Improving quality”.
The first one, it would seem, should say: take the most unoccupied channel, channel width 40 MHz, more antennas (preferably 4), and add more Capabilities.
Second - remove everything except the basic n-mode, turn on more power, and turn on those Capabilities that add stability.
Recalling once again the proverb about ravines, we will describe what kind of uneven terrain awaits us when trying to implement plans 1 and 2.
Ravine zero
Although Ralink rt2x00 family chipsets are the most popular chipsets supporting the n standard and are found both in high-end (Cisco) and low-end (TRENDNET) cards, and moreover, they look exactly the same in lspci, they can have radically different functionality, in particular, support only the 2.4 band, only the 5GHz band, or support incomprehensibly limited parts of both bands. What is the difference is a mystery. It's also a mystery why a card with three antennas only supports Rx STBC in two streams. And why don't they both support LDPC.First ravine
There are only three non-overlapping channels in the 2.4 band. We have already spoken on this topic and I will not repeat myself.Second ravine
Not all channels allow you to increase the channel width to 40 MHz, moreover, what channel width the card agrees to depends on the card chipset, card manufacturer, processor load and weather on Mars.The third and largest ravine
Regulatory domainIf you did not have enough for happiness that you yourself wifi standards are a noble vinaigrette, then rejoice that every country in the world strives with all sorts of different Wi-Fi ways infringe and restrict. In the UK, things are still not so bad, unlike, say, the USA, where the Wi-Fi spectrum is regulated to the point of impossibility.
So, the regulatory domain may require restrictions on the power of the transmitter, on the ability to launch an access point on the channel, on acceptable modulation technologies on the channel, and also require some “spectrum pacification” technologies, such as DFS(dynamic frequency selection), radar detection (which each domain has its own, say, in the Americas almost everywhere offered by the FCC, in Europe it’s different, ETSI), or auto-bw (I don’t know what it is). At the same time, with many of them, the access point does not start.
Many regulatory domains simply ban certain frequencies altogether.
You can set the regulatory domain with the command:
Iw reg set NAME
The regulatory domain can be omitted, but then the system will be guided by the union of all restrictions, that is, the worst possible option.
Fortunately, firstly, data on regulatory domains are available in open access on the kernel site:
And you can search for them. In principle, it is probably possible to patch the kernel so that it ignores the regulatory domain, but this requires rebuilding the kernel, or at least the crda regulatory daemon.
Fortunately, the iw phy info command displays all the capabilities of our device, taking into account (!) the regulatory domain.
So, how do we fix the state of our Wi-Fi?
First, let's find a country in which Channel 13 is not banned. A path of at least half the frequency will be empty. Well, there are quite a few such countries, although some, without prohibiting it in principle, however, prohibit it either high speed n, or generally creating an access point.
But one channel 13 is not enough for us - because we want a larger signal-to-noise ratio, which means we want to launch a point with a signal strength of 30. We are looking for-looking in CRDA, (2402 - 2482 @ 40), (30) 13 channel, width 40 MHz, signal strength 30. There is a country New Zealand.
But what is it, at 5 GHz, DFS is required. In general, this is theoretically a supported configuration, but for some reason it does not work.
An optional task that can be completed by people with advanced social skills:
Gather signatures / movement in support of accelerated relicensing of Wi-Fi bands in the ITU (well, or at least in your country) in general towards expansion. This is quite real, some deputies (and candidates for deputies), thirsting for political points, will be happy to help you.
This is ravine number 4
The access point may not start with DFS, without explanation. So, which regulatory domain should we choose?There is one! The freest country in the world, Venezuela. Its regulatory domain is VE.
A full 13 channels of the 2.4 band, with a power of 30 dBm, and a relatively relaxed 5 GHz band.
Asterisk challenge. If you have a complete disaster in your apartment, even worse than mine, there is a separate, bonus level for you.
Regulatory domain "JP", Japan, allows you to do a unique thing: run an access point on the mythical channel 14. True, only in mode b. (Remember, I said that there are still small differences between b and g?) So if everything is really bad for you, then channel 14 can be a salvation. But then again, it is physically supported by a few client devices and access points. Yes and maximum speed at 11 Mbit is somewhat discouraging.
Copy /etc/hostapd/hostapd.conf into two files, hostapd.conf.trendnet24 and hostapd.conf.cisco57
We trivially edit /etc/rc.d/rc.hostapd to run two copies of hostapd.
In the first one, we indicate channel 13. True, we indicate the signal width of 20 MHz (capability 40-INTOLERANT), because, firstly, this way we will be theoretically more stable, and secondly, “law-abiding” access points simply will not start at 40 MHz from -because of the clogged range. Set capability TX-STBC, RX-STBC12. We cry that capabilities LDPC, RX-STBC123 are not supported, and SHORT-GI-40 and SHORT-GI-20, although they are supported and slightly improve speed, but also slightly lower stability, which means we are removing them.
True, for amateurs, you can patch hostapd so that the force_ht40 option appears, but in my case it makes no sense.
If you are in a strange situation when access points turn on and off, then for special gourmets you can rebuild hostapd with the ACS_SURVEY option, and then the point itself will first scan the range and select the least “noisy” channel. Moreover, in theory, it should even be able to move at will from one channel to another. However, this option did not help me, alas :-(.
So, our two points in one case are ready, we start the service:
/etc/rc.d/rc.hostapd start
The points are starting successfully, but ...
But the one that works on the 5.7 range is not visible from the tablet. What the hell is this?
Ravine number 5
The damned regulatory domain works not only on the access point, but also on the receiving device.Specifically my Microsoft Surface Pro 3, although made for the European market, in principle does not support the 5.7 band. I had to switch to 5.2, but then at least the 40 MHz mode started up.
Ravine number 6
Everything started up. The points started, 2.4 shows a speed of 130 Mbps (would be SHORT-GI, it would be 144.4). Why a card with three antennas only supports 2 spatial streams is a mystery.Ravine number 7
It started up, and sometimes the ping jumps up to 200, and that's it.And the secret is not at all hidden in the access point. The fact is that according to the rules of Microsoft, WiFi drivers the cards themselves must contain software for finding networks and connecting to them. Everything is like in the good old days, when a 56k modem had to have a dialer with it (which we all changed to Shiva, because the dialer that came with the standard delivery Internet Explorer 3.0 was too terrible) or the ADSL modem had to have a PPPoE client.
But even those who do not have a regular utility (that is, everyone in the world!), Microsoft took care of it by making the so-called “Wi-Fi auto-configuration”. This auto-configuration cheerfully spits on the fact that we are already connected to the network, and scans the range every X seconds. Windows 10 doesn't even have a "refresh networks" button. Works fine as long as there are two or three networks around. And when there are 44 of them, the system freezes and gives out a few seconds of 400 ping.
"Autoconfiguration" can be disabled with the command:
netsh wlan set autoconfig enabled=no interface="???????????? ????" pause
Personally, I even made myself two batch files on the desktop “enable autoscan” and “disable autoscan”.
Yes, please note that if you have Russian Windows, then most likely network interface will have a name in Russian in the IBM CP866 encoding.
Summery
I've rolled out a rather long sheet of text, and I should have ended it with a brief summary of the most important things:1.
The access point can only work in one range: 2.4 or 5.2 or 5.7. Choose carefully.
2.
The best regulatory domain is VE.
3.
The commands iw phy info, iw reg get will show you what you can do.
4.
Channel 13 is usually empty.
5.
ACS_SURVEY, 20MHz channel width, TX-STBC, RX-STBC123 will improve signal quality.
6.
40 MHz, more antennas, SHORT-GI will increase the speed.
7.
hostapd -dddtK allows you to run hostapd in debug mode.
8.
For amateurs, you can rebuild the core and CRDA, increasing the signal strength and removing the restrictions of the regulatory domain.
9.
Wi-Fi auto-discovery in Windows turns off netsh command wlan set autoconfig enabled=no interface="???????????? ????"
10
. Microsoft Surface The Pro 3 does not support the 5.7 GHz band.
Afterword
I am most of the materials used in writing this manual, found either in google or in mana to iw, hostapd, hostapd_cli.In fact, the problem IS NOT SOLVED. At times, the ping still jumps to 400 and stays at that level, even for the “empty” 5.2 GHz band. Therefore:
I am looking for a Wi-Fi spectrum analyzer in Moscow, equipped with an operator, with whom I could check what the problem is, and whether it is that there is a very important and secret military institution nearby that no one knows about.
P.S
Wi-Fi operates at frequencies from 2 GHz to 60 GHz (less common formats). This gives us a wavelength of 150mm to 5mm. (Why do we even measure radio in frequencies, and not in wavelengths? It's also more convenient!) I, in general, have an idea, buy wallpaper from a quarter-wavelength metal mesh (1 mm is enough) and make a Faraday cage to guarantee isolate yourself from neighborhood Wi-Fi, and at the same time from all other radio equipment, such as DECT phones, microwaves and road radar(24 GHz). One problem is that it will also block GSM/UMTS/LTE phones, but you can allocate a stationary charging point for them by the window.I will be glad to answer your questions in the comments.
