Networking

How many antennas must a router have to have good coverage?

Since the launch of the WiFi 4 standard, both routers and WiFi access points have incorporated more and more antennas, whether they are external antennas or internal antennas. Is it really necessary to have so many WiFi antennas in a router? How many WiFi antennas should a router have to have good coverage and speed? Today in RedesZone we are going to talk about the number of antennas, and what is the use of a router having so many.

What are the antennas of a router?

The antennas in a wireless router are what provide us with WiFi connectivity so that we can connect wirelessly with any device. Before talking about the number of antennas, let’s talk about the components that a router incorporates inside:

  • CPU : it is in charge of processing all the data of the router.
  • Switch : it is in charge of managing all the wired connectivity, and it connects with the CPU directly to know where it should direct these packets
  • RAM memory : it is responsible for storing all the processes that the router firmware incorporates, the operation is the same as that of a PC. It is a volatile memory, every time we restart the router all the information is erased.
  • Flash memory : it is a non-volatile memory that is internal to routers, it is used to store the firmware and “load it” when the router starts, it is something like the SSD or hard disk of a PC. An important detail is that it not only serves to store the firmware, but also the configuration of the router itself. Thanks to this flash memory, we will not have to configure the router every time we start it.

If we talk about a wireless router, we also have a chipset that is specifically responsible for managing wireless connectivity, this is called a WiFi controller. If our router has a single frequency band, we will only have one WiFi controller. If we are facing a simultaneous dual band or simultaneous triple band router, we will have two or three WiFi controllers respectively.

The WiFi controllers are individual chipsets, although in some router models, the main CPU itself is also in charge of managing the wireless network, since it has a WiFi controller internally. Low and mid-range routers are usually like this to save costs for a dedicated chipset exclusively. The WiFi controller is the one that determines how many antennas a WiFi router can have, if the WiFi controller only supports 2 antennas, then we cannot decide to put 3 antennas, because the third we will not be able to connect internally to the WiFi controller. Some widely known wireless controller manufacturers are Broadcom, Qualcomm and also Realtek, the latter manufacturer is mostly in the low and mid range routers as they are cheaper.

Types of antennas

In the world of WiFi we have several types of antennas, the omni-directional ones that emit in all directions (in the horizontal plane), the sectorial ones that emit in a certain sector of 90, 120, 135 or 180 degrees, and the directional ones that emit with a smaller angle of incidence, about 30 or 45 degrees. In all home WiFi routers we have omni-directional antennas, because we are interested in providing WiFi coverage in all directions in the horizontal plane.

Regarding the gain of the antennas, we will find a gain between 3dBi and 5.5dBi approximately, we must bear in mind that the more dBi of gain we have, the more sensitivity the antenna will have and we can cover greater horizontal coverage, but sacrificing the coverage vertical because the vertical angle of incidence is smaller. Therefore, in a domestic environment it is recommended not too much antenna gain, especially if we have a house with several floors.

Internal antennas or external antennas?

Currently we are finding routers and WiFi Mesh systems that have internal or external antennas, in fact, in some models we have a combination of both, for some frequency bands they are external antennas and in other internal antennas. Regardless of whether they are internal or external antennas, the antenna cable itself that is on the board can be soldered directly to the power amplifiers, or they make use of a UFL connector to give the possibility of changing the antenna cable in the future. .

When the antennas are internal, we normally have an antenna cable that is soldered or to a UFL connector from the power amplifier, to the area of ​​the router where the internal antenna has been located, which is still a kind of metal plate in several sides of the router. In the following photo you can see an internal antenna of the FRITZ! Box 7590 router:

When the antennas are external, we normally have the antenna cable that is soldered or to a UFL connector from the power amplifier, to the RP-SMA connector of the external antenna, which we will screw later to have coverage. In the following photo you can see the antenna cable (black color) to the RP-SMA connector of the ASUS RT-AX88U router:

Regarding the question of which is better, if external or internal antennas, as a general rule, routers that have external antennas provide greater coverage, but this depends on many factors: signal strength, signal losses through the antenna cable, and the loss by the RP-SMA connector of the external antenna, in addition to the gain of the external antenna.

A very important aspect is that we can orient the external antennas and modify their position by ourselves, to test if in a certain place the performance has improved or it has not, the most advisable thing is to place the router antennas in a different position. to radiate in all directions. However, MIMO and Beamforming technology will work so that it is not so necessary to orient the external antennas in our router, but in certain complex scenarios where we have houses with several floors, it would be advisable to try to change the position of the antennas and not have all of them in the same way. vertical.

Internal antennas normally provide coverage in the form of a sphere, and not donut-shaped as with external antennas. Therefore, while an internal antenna provides more complete coverage (to all sides), an external antenna can go further in the horizontal plane. One aspect in favor of external antennas (removable with RP-SMA connector) is that we can change them for higher gain ones. At the level of transmission power, in both it will be the same because the limit is set by the legislation in force in each country.

The most normal thing is that the same router with external antennas and internal antennas always have the same coverage, but if in a router with internal antennas we put obstacles near it, logically it will be affected by them and they will provide less coverage. For this reason, many router manufacturers design them to stand vertically and not put books on top of it, which is dangerous for both router cooling and WiFi coverage.

What are so many antennas for in a router?

With the launch of the WiFi 4 standard, MIMO (Multiple Input Multiple Output) was launched, a technology that allows us to take advantage of more than one antenna to communicate simultaneously with a specific wireless client. This means that if a router has two antennas (regardless of whether they are internal or external), it allows a WiFi client with two antennas to use both simultaneously for twice the speed. The same happens if we have a router with three antennas and a WiFi client with three antennas, we will have triple the speed than if we used a single antenna.

A very important detail is that if a router has four antennas and the WiFi client only has two, then logically they will only be able to communicate with two antennas, but the other two remaining antennas of the router can be used by another WiFi client to send and receive data in how long the one currently transmitting ends. Therefore, a greater number of antennas will allow us a greater capacity of simultaneously connected WiFi clients.

With the WiFi 5 and WiFi 6 standards, MIMO has been further improved with the launch of MU-MIMO. While with MIMO you cannot transfer data simultaneously from or to several WiFi clients at the same time, MU-MIMO does allow it. A router that has a total of four antennas and supports MU-MIMO will be able to transfer data to the following clients simultaneously:

  • A WiFi client with two antennas
  • A WiFi client with an antenna
  • A WiFi client with an antenna

But if we connect WiFi clients with only one antenna, we could transfer data to up to four clients simultaneously.

Therefore, the number of antennas that a WiFi router has matters a lot for:

  • Provide higher WiFi speed to clients with two antennas or more.
  • Provide higher speed globally if MU-MIMO is supported
  • Greater capacity of the WiFi network, more number of connected WiFi clients without the speed being affected too much.

We must remember that MU-MIMO technology is only available in the WiFi 5 version (WiFi AC Wave 2) in the 5GHz band, and in the new WiFi 6 standard it is available in both frequency bands (2.4GHz and 5GHz). A very important detail is that, currently, the maximum number of antennas that we have available in top-of-the-range domestic routers is four antennas for each WiFi frequency band.

Do you place the router antennas correctly?

Routers with internal antennas, there is no possibility of moving them anywhere, what is recommended is to leave the area where we are going to place the router free, so as not to have additional obstacles and that the WiFi signal reaches better. Regarding external antennas, depending on how many antennas the router has and the design of the equipment, the most normal thing is to place them differently and not all vertically, to try to radiate in all directions as if it were a sphere. However, both MIMO and Beamforming technology will work together to always provide us with the best coverage, even if we have the antennas vertically.

In some tests that we have carried out, we have tried to place the antennas horizontally to better reach the floor below where we carry out the performance tests, and the speed difference is negligible, around 5% is gained approximately. If you are in an environment where the coverage is really weak, it is possible that in this case it is worth moving the antennas to try to improve the coverage received by wireless clients.

How much coverage is gained with each antenna of a router?

In outdoor spaces, if a router has one or more antennas, we will not notice much improvement in terms of coverage. But indoors it is critical that a router incorporates two or more antennas, to take advantage of both the MIMO and MU-MIMO technologies that we have explained before, as well as to take advantage of the Beamforming technology. Beamforming technology allows you to vary the phase relationship of the signal in each antenna, to “focus” the wireless signal on a specific WiFi client, and provide it with a greater range and speed. If our router has two or more antennas for each frequency band, we can take advantage of all these technologies.

In indoor spaces, the wireless WiFi signal does not stop bouncing with the different objects in our home, people, furniture and much more, and, of course, the signal will gradually fade. Thanks to the aforementioned technologies, the WiFi signal can choose several different routes to the same destination, using each antenna with a different path to reach the wireless client, and later “activating” the one that gives us the best result. The more antennas we have in a WiFi router, the probability that none of them will be able to reach the destination is less, it is what is called antenna diversity, because these antennas are physically separated and use a signal with different phase, which which aids in reducing noise and interference from multipaths.

Generally speaking, adding more antennas in the router or in the WIFi clients, makes the coverage greater, the quality of the signal increases, and also the WiFi performance (speed). Lastly, it also improves the reliability of the wireless link.

Due to everything that influences the coverage of WiFi networks, it is difficult to quantify how much we will gain in coverage with each additional antenna that a router has. The first thing that we must take into account is the operation of MIMO and MU-MIMO, since it is directly related to the antennas that we have, but in this case, we are not talking about coverage but about the maximum speed that we can achieve. Regarding coverage, taking into account the performance obtained by dozens of routers with many different antenna configurations, from RedesZone we believe that having three WiFi antennas for each frequency band is the best in coverage / performance / price of the equipment.

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