How I created seamless Wi-Fi

In our office, not so long ago, the task was ripe to make a seamless Wi-Fi-coverage, for a long time they endured and shuffled, but in the end they did it. I will share the experience of how it was. It began with the fact that two years ago we completely switched to IP-PBX and almost wiped out analog phones including, as a result, DECT. However, portable handsets are needed and in addition to SIP desktop phones, several Tecom Wi-Fi phones have been bought. I myself, as the person responsible for the technical part of the company, constantly go to the office with various Wi-Fi devices, and also the managers. Many have on hand the mentioned Wi-Fi SIP phones, + the warehouse has a couple of Wi-Fi terminals, there are just Androids and Apples with installed SIP clients from the PBX. Previously, everything was decided by several Wi-Fi routers, in principle, it was also acceptable (the office is small), but exactly while you are sitting still - went, that's it, the conversation ended, and a Skype connection crashes even faster. This began to annoy the management and managers pretty much and they started raiding that wi-fi was not wi-fi. Attempts to simply increase the number of routers clearly did not solve the problem.

I began to read, and yet read that everything had been invented for a long time before us. There are Wi-Fi points that can make the client switch among themselves without disconnection or almost without disconnection. Moreover, there is a lot of such equipment on the market, it remains only to choose according to the budget and adequacy. It turned out that there are a lot of publications on this topic in the foreign Internet, we have less. A huge minus of these systems is that they all want a controller that stands like a cast-iron bridge and some especially greedy also require licenses to connect each point. I brought a quote to our office on one such respected equipment, the eyes of the general were widened and the answer was visible on his face even before he read this calculation.

In general, as the problem was studied, a sporting interest woke up - is it possible to make a smooth WiFi coverage (just like on the forums) with normal money and so that without these controllers? It turned out you can.

True, the choice of option took time, but after downloading it turned out that we need access points that support the 802.11r and 802.11k protocols. These protocols are responsible for the fast, almost instantaneous switching of subscribers from one point to another. The market provides many options with support for these protocols, but either past the price, or again on the controller. As a result, I came across the right option by accident. Was in the summer at the Ibis hotel in Kazan at the weekend with his wife and in all corridors there were “pancakes” with the inscription EDIMAX on the ceiling. When you are looking for it for a long time and intently, you begin to pay attention to how "adults" are done. Googled what it was, found it - it turned out to be not a great problem. And lo and behold! This Edimax turned out to work without a controller. All that is needed is to assign one of the points to the controller.

On the manufacturer’s website there was such a clever picture where they boast about how everything “flows” from them from one point to another.



To be honest, I got hooked on her. Also two floors are painted like ours, a staircase, a straight shot in the head.

We looked closer at the specifications - it seems to be suitable, the price is not shocking.
At first they bought two: 1 ceiling and one wall (honestly, it was embarrassing that I had not encountered this brand before, but the benefit of the OZPP gives us 14 days to return).
And, oddly enough, it worked.

Now in order.

First, a little theory. Briefly about the mentioned 802.11r / k protocols (excerpts from the Internet):

802.11k- Reduces the search time for access points with the best signal parameters. According to this protocol, information about neighboring access points and the status of their channels is transmitted to the client.

That is, as I understand it, even without starting the movement, the subscriber’s device already knows in advance where roaming is possible and which access point will serve it better. And this is actually what we need.

802.11r - uses the Fast Basic Service Set Transition technology, which allows you to store encryption keys for everything from network access points. As a result, the client is freed from the process of full authentication with the server - just 4 short messages are enough to switch to a new access point. This property allows you to spend on the transition no more than 50 milliseconds.

In general, these protocols turned out to be very common, but not all subscriber / client devices and even access points on the market support these protocols. Although, for example, apple devices (no matter how anyone refers to them) turned out to support these standards almost from 2011. Therefore, the construction of communication, so to speak, on the basis of domestic access points will reduce the attempt to organize seamless roaming to naught - without 802.11k / r support, switching can take up to 3 seconds. There is no talk of seamlessness with such lags in switching! What I came across in my experiments with routers.

Now I turn to the direct construction of a WiFi network. As I said, we initially took 2 points of this Edimax and, after a successful test, slightly expanded the park within the budget. I specifically took several different access points (naturally of the same manufacturer) that work both in the 802.11ac standard and only in 802.11n, for the network as a whole it does not matter. It is essential that they support 802.11k / r protocols. Why did you take different ones? - they have a different radiation pattern and some of them are cheaper. For example, in places where there are few subscribers, I set up relatively simple access points, and in the meeting room, at the management, as well as in other places with a lot of people I mounted top models. Well, again, Wi-Fi AC, fashionable, fast and free 5 GHz band. And they don’t care with the warehouse, and the N300 will do it.

As for the specifics, I chose from EDIMAX PRO models: CAP300 , CAP1750 , WAP1200 and WAP1750 . Moreover, the WAP1750 in this case acts as a controller. In general, Edimax has a lot of network equipment of the household type, but you should not confuse it, I'm talking about their business series now and this is really not a bad equipment in my opinion.

About installation:

Set up access points in the office.



I received the broadcast according to the plan, which you see on the screenshot of the Edimaksov point management system. It is at every point and, in principle, any could be a controller. This system has an e-map function. That is, you can drag a building diagram into the web-interface or the territory there and indicate the scale and places where the points stand on it. As a result, the system will show approximate coverage areas. In general, not a breakthrough, but convenient.



My office has two floors and for the test I placed one access point in the meeting room on the first floor (on the plan on the right), and three other access points were located on the second along the corridor. I emphasize that the signal level everywhere should be good enough - nevertheless, I do seamless roaming and here it is unacceptable to walk with a laptop and look for the place of the best reception. The screenshot shows the stage of about half the work, only 4 points are mounted, now there are already 7. All points are PoE-shny, so I had to start another PoE switch on the farm. Existing ports were already occupied by telephones. As a result, every corner is covered and the same Tekomovsky phones work on the network better than DECTs.

By the way, a photo of the real access points involved in solving the problem:



- EDIMAX CAP300



- EDIMAX WAP1200



- EDIMAX CAP1750

This is the Edimaks most fashionable point. Built-in MIMO 3x3 antenna, 2 bands and all the pies. It is not large in the picture, but in real life it is slightly larger than its counterparts САР300 / САР1200 - the size of a small pancake pan with low sides.



- EDIMAX WAP1750

At ceiling points, the directivity pattern is approximately 190 degrees for wall-mounted 360 and the antennas are external, therefore more powerful and illuminate spherically. But for the sake of truth, I would like for the antennas to be a little more powerful. I set WAPs in “lonely” zones and difficult places with thick ceilings. In principle, a brick wall and ceiling breaks through, but if the horns were more powerful, it would be even better. Perhaps in the future I will replace the standard RP-SMA connector on the WAP points with other third-party antennas. Along the way, the problem surfaced that there are almost no 2.4 + 5 GHz combined antennas on the market. Why is it not clear. The advantage of WAPs is the presence of 2 PoE ports, PoE at the input (the point itself is powered) and PoE af to the output, you can connect something else to it. In the context of my shortage of PoE ports, it can be very suitable in the future.

So, after mounting the points, we proceed to the roaming setup itself. We turn to the WAP1750 point planned to be the controller and tell her that she is now the leader in the pack. We check the connection with other points, open the Edimax Pro NMS (Network Management Suite) control panel and see that all access points are on the network.



Everything lives, a dumb check of Internet access in different places of the office says that everything seems to be OK. The connection does not break, but you need to somehow make sure that it is so on something more substantial.

Well, we turn to the most important thing - we are testing the network under load (the moment of truth is coming. Now we’ll check who is actually lying). To do this, we conduct field tests - we load WiFi with streaming video downloaded from YouTube and broadcast it on the network. We could connect directly to YouTube, but then we would depend on an external Internet channel, where theoretically possible failures that would affect the purity of the experiment.



Now the most important thing - I take a tablet, pick up a video, broadcast it over a Wi-Fi network and go around the office. I move from one room to another, go along the corridor, go down the stairs to the floor below, go through there, go up and come to the starting point. The whole process took several minutes, registered with an external action camera and is located here .



By the following link you can see the same video, but with a demonstration of the process of preparing the broadcast.



I ask you not to judge strictly for the quality of shooting and still look at both materials, here I bring only a few still images.







Actually, this video is the main goal of the experiment. I specially installed the external camera so that both the tablet and the office were visible at the same time, in order to confirm the purity of the tests. Please note that the video with the motorcyclist flows smoothly, is not interrupted for a second and does not slow down. Moreover, the word second in this case looks too large - there are no failures even for tenths of a second. Naturally, if such heavy traffic as streaming video is broadcast without failures, then significantly lighter VoIP traffic is transmitted simply to the URA.

So this function can be used to organize voice communications within offices using SIP phones or communicators, as is actually done with us. That is, DECT with such a normally built network is not needed at all.

In this case, I did not go into details and did not show the WiFi settings and the network part. The aim of the experiment was to demonstrate the possibility of organizing wireless access with seamless coverage and real roaming, which really works. It turned out to be possible to do this without a controller, and most of the time it took installation and cable routing. The setting is elementary.

I hope you repeat the experiment, make sure I'm not lying. Well, and spread the best practices further. And I'm going to spin the director for a prize. Joke.

PS I want the author of the video “Motor trial in the city” Mikhail Vichkasov not to beat me for using his personal video for my educational purposes.