Routers and antennas:
What really matters with wireless networks

A stable and powerful wireless connection is the basis of modern wireless network solutions. Not only a suitable router is crucial for this, but also the correctly selected and installed antennas. This article shows which aspects should be taken into account.

A wireless network is made up of several components, with the wireless router playing the central role. When selecting a device, it is important to ensure that it offers the performance required for the respective application, for example sufficient computing power for routing tasks. It is equally important to configure the device correctly.

The antennas are at least as relevant. However, they are often underestimated in practice. Even a high-quality router cannot perform to its full potential if unsuitable antennas are used or positioned unfavorably. To ensure good network quality, antennas must be selected that are suitable for the technologies used (e.g. MIMO, 4G/5G, WLAN or GNSS), cover the correct frequency ranges, offer sufficient gain and are suitable for the intended mounting form. The cables and connectors used also play an important role, particularly with regard to attenuation and shielding.

The choice of a suitable antenna depends primarily on the specific application and location. A few basic questions should therefore be answered before making a selection:

• Which radio technologies are used (e.g. mobile radio, WLAN, GNSS)?
• How many antennas are required for this (keyword MIMO)?
• Is the installation indoors or outdoors?
• What is the distance between the router and the antenna?
• What range or area coverage is required?
• Does the assignment take place in a rural environment or in an urban area?
  Do special standards or regulations have to be complied with, for example for fire protection, road traffic or rail applications?

The positioning of routers and antennas must be carefully planned. It is important to position the antenna in the immediate vicinity of the router and with as little shadowing as possible – i.e. not under seats or behind metal surfaces.

Once the locations have been determined, the required cable lengths are calculated. As a rule of thumb: Depending on the cable quality and frequency range, lengths of up to 3 meters (from approx. 2 GHz) and up to 5 meters (below 2 GHz) make sense. In addition, the losses increase significantly, which is why special low-loss extension cables with attenuation values below 0.2 dB/m should be used for longer distances. This allows total lengths of over 10 meters to be achieved. However, if the cable runs become too long, the connection deteriorates considerably. In such cases, a wireless solution is no longer practical and wired alternatives must be used.

If several radio services are used, such as mobile radio and navigation, combined antennas are a good choice, combining different antennas in one housing. The main advantages of these are their quick and easy installation, low installation effort and identical cable lengths. The reduced intervention is a particular advantage for vehicles or rented appliances.

However, depending on the structure of the antenna emitters, mutual interference can occur that limits the usable bandwidth or influences navigation signals. Individual antennas are only advantageous if they can be mounted at a sufficient distance from each other – usually more than 30 cm. The greater this distance, the less the mutual influence.

A special application is WLAN in vehicles: As the mobile radio antenna of the router should always be mounted outside the vehicle, a combined mobile radio/WLAN antenna on the roof of an emergency vehicle or train cannot guarantee the desired WLAN coverage for emergency services or passengers in and around the vehicle. In such situations, it is advisable to separate the antennas and place the WLAN antenna in the interior or on the sides of the vehicle – i.e. where the WLAN is actually used.

The antenna performance is significantly influenced by the ambient conditions. To ensure optimum signal transmission, the environment should be adapted accordingly. The entire system – consisting of antenna, cable connection and router – must be taken into account. In addition, legal regulations, such as road traffic or fire protection guidelines, may have to be complied with for both the antenna and the router.