Improving the work of Wi-Fi. Part 2. Features of equipment

Friends, this article is a continuation of the first part of a series of articles on how to improve the work of WiFi in the office or in the enterprise.

Expectations and surprises

As an introduction, we present some facts.

The power of Wi-Fi - the signal at the point of reception depends on several circumstances:

distance (from client to access point);
antenna gain;
directivity pattern;
the presence of external interference (including from devices with Bluetooth, microwave ovens, and so on);
obstacles in the path of the signal.

Therefore, if there is a change of landscape, the appearance of "foreign" signal sources, the installation of additional isolating walls, and so on, one has to adapt to the new conditions.

Important! It is impossible to speculatively determine all the nuances that affect the quality of the wireless network. To produce more or less accurate data in each case, you need to conduct a preliminary study.

Much depends on client devices. One of the interesting examples is the case when the internal IT infrastructure was designed a long time ago and was fully adapted for the 2.4 GHz band. However, the massive popularity of devices on 5 GHz has made its own adjustments. It took a partial replacement of wireless equipment and a change in the map of the location of access points, taking into account the recommendations to place customers in the “line of sight”.

To clarify those or other preliminary decisions, detailed terrain mapping (survey and mapping of Wi-Fi signal coverage from all access points) helps.

Sometimes at the initial stage, one has to be content only with knowledge of the approximate number of devices and an approximate layout, and to clarify the questions that arise after installation with subsequent testing and debugging in place. This also applies to the choice of antennas for signal amplification.

The situation with the design and modernization of Wi-Fi is somewhat reminiscent of the prevention of morbidity. Of course, no one has the exact prediction of what diseases will have to fall ill in the near future. However, knowing the general principles, such as adherence to the rules of hygiene, maintaining a healthy lifestyle and following the recommendations of doctors, you can avoid many troubles.

Similarly, when designing various systems, one cannot know everything in advance, but there are some general principles to which our article is dedicated.

Additional antenna, repeater or data transfer between points?

There are several ways to improve networking. Accordingly, there are several types of equipment that helps to do this.

Additional antenna

Additional external antennas are used to amplify the signal of access points. Sometimes an amplifier is included in the kit besides the antenna itself. Such devices often have external power supply, for example, from a power outlet.

The main merit of the antenna is that it simply increases the signal power.

This approach is good when there is a vast space where a small number of customers are located. For example, an industrial warehouse. Placing the antenna from a single point under the ceiling in the center of the room, you can get accessibility throughout the area for several storekeepers and warehouse visitors.

If you put two such powerful emitters side by side, instead of helping each other, they will introduce mutual interference.

It should be remembered that no matter how powerful the antenna is, the number of connected clients will be limited and limited by the internal resources of one access point.

For a busy office "anthill", when most consumers are next to each other, building a network based on a single access point, even with the most powerful antenna, is not a good idea. More power is not so demanded here, load balancing between several points, the ability to accept more simultaneous requests from customers or block unwanted access will be much more useful.

Therefore, we leave the access point with an external antenna in its place - in splendid isolation under the roof of the warehouse and move on to another item of our description.

Using repeaters

A repeater is a device that receives a signal from an access point and sends it to the client, or vice versa from the client to the point.

This allows you to extend your wireless network coverage. Customers without any problems will be able to connect to the repeater in areas where the signal starts to weaken.

The disadvantage of this type of device is the need for the repeater not only to communicate with the client, but also to interact with the main access point. If only one radio module is used, respectively, and it has to work “for two”., Which reduces the speed of access over the network. This option is usually found in inexpensive devices for home use.

For situations where the speed drop is unacceptable, it is recommended to use models of repeaters with two radio modules. Having a second Wi-Fi receiver transceiver ensures a more stable and faster wireless network.

Another fact that needs to be taken into account is the ability to work in both bands: 2.4 GHz and 5 GHz. Some outdated or very simple home-only models support a single 2.4 GHz band.

Council If you decide to use repeaters, then it is worth considering the model AC1300 MU-MIMO - a dual-band repeater wireless network.

Using a wireless signal to connect multiple access points

This option is used when it is not possible to connect all access points to a single network using cable infrastructure. This is somewhat similar to the use of repeaters, but instead of a “stupid” repeater, they use a full access point.

As in the case of a repeater, it is strongly recommended to use access points with two Wi-Fi interfaces. One of them will be used to communicate with the neighboring point, and the second - to ensure interaction with customers.

If in this mode a point with a single interface works (for this you need to configure the interface in AP + Bridge mode), the final data transfer rate between the client and Wi-Fi network resources will be significantly lower.

This dependence is related to the fact that Wi-Fi technology uses time division multiplexing (TDM), and data transmission at a time is possible only from one network participant in one direction.

Unfortunately, work in this mode does not provide distribution between several access points. As already described in the article “Synchronization of Wi-Fi Access Points for Collaboration” - a situation arises when a large number of users are connected to remote access and nearby access points are practically not loaded.

The most preferable option is to use the connection of access points via a network cable with synchronization through a dedicated Wi-Fi network controller.

On the wall or on the ceiling?

There are various options for the placement of access points. Depending on the convenience, the specifics of the room: a large office, a small office, a restaurant, a shop and so on - you have to select the most suitable accommodation option. In some cases, the access point is more convenient to place on the wall, in some - under the ceiling or even under the roof itself. A separate case - access points for outdoor placement, simply put “on the street”, but at the moment we will deal only with equipment for internal premises.

Placing the access point on the wall is your difficulty You may need to drill walls for fixing, to solve issues with the power supply and network cables, and so on.

And what if the access point is placed not on the wall, but immediately under the ceiling? What difficulties await here?

First of all, there may be problems with fixing the point to the ceiling. For example, in modern offices they make a false ceiling of plasterboard, which makes its own adjustments to the equipment placement process.

Therefore, you need to immediately consider the option of mounting.

If you intend to connect the access points to the network by means of cables, it may be necessary to additionally conduct special chutes over the false ceiling, in which the power cables and communications of the local network will be laid.

If there is no false ceiling, the question of drilling ceilings and connecting power and network cables to an access point may not be the easiest thing.

Recently offices in the “loft” style are widespread, in which the concept of a ceiling is completely absent, and various pipes and communications pass over the heads of employees. In this situation, fix the access point and conduct cables to it will be much easier. However, the presence of large metal objects such as thick pipes, fittings, gratings - all this can change the conditions for the passage of the signal. Let me remind you that the final answer to the applicability of a particular scheme can only be given by special research or specific practical experience.

The figure shows option 1 with ceiling placement. With this arrangement, the access points can affect each other. And here you will need the standard methods of reducing mutual interference: the use of various channels and power adjustment, described in the article “Improving the performance of Wi-Fi. General principles and useful things .

Figure 1. Location of access points under the ceiling.

However, ceiling placement can provide better coverage of the entire office space.

Direction of the emitted signal

Having weighed all the advantages of one or another option, you should not rush to simply outweigh the access point from the wall to the ceiling, or vice versa, from the ceiling to the wall. For a start it is worth solving the issue of changing the directionality of the signal

For equipment for a wireless network, originally intended for placement on the ceiling, the signal is propagated by radial circles, the center of which is the receiving-transmitting module (see Figure 2).

Figure 2. Signal propagation at wall and ceiling placement.

What happens if an access point for ceiling placement is taken and simply hung on the wall? In this case, the signal will be well accessible only in close proximity. For customers on the opposite side of the room, the signal level will be significantly lower and the connection will not be of very high quality.

A similar problem occurs if the wall access point is placed on the ceiling. Its directional pattern is not directed round the circle, but from the wall on which the point hangs - along the room (see Figure 2). If such a point is on the ceiling, then the main coverage area will be directly below it. Simply put, the radio module of this point will “shoot at the floor,” from top to bottom.

As mentioned above, in some cases it is not so easy to immediately select the optimal location for all access points. Fortunately, Zyxel has universal models that allow you to select the mode of use depending on the placement: on the ceiling or on the wall.

Note We recommend to pay attention to the models that are adapted to the two mounting options, and also have two radio modules, for example, NWA1123-AC PRO .

The versatility of accommodation is also worth considering if you plan to move the office. In this case, it will be wise to select adaptable access points.

Let's summarize

There are no “for all occasions” methods, but adherence to some of the recommendations allows you to avoid many of the problems of designing, deploying and maintaining a Wi-Fi network.

Do not place transmitters too close to each other.

In some cases it is better to use access points for placement on the ceiling, in others - on the wall. You must consider the radiation pattern for each of the options. There are universal access points with the ability to switch the mode of use.

In the next article in this series, we will talk in more detail about the placement of wireless equipment.