Power lines affect television antennas

Factors influencing LTE reception

Which factors have a negative effect on reception quality & how can you improve it?

If the choice fell on Internet access via a radio medium, for example UMTS / HSPA or LTE, you have to familiarize yourself precisely with the local conditions. The weakest link in the entire connection chain is and remains the so-called air interface, i.e. the radio link between your own terminal and the base station.

The quality of this connection is extremely important for the performance of the Internet connection, but not necessarily responsible for all problems. A weighty, secondary problem is the fact that all users in a cell have to share the capacity of this air interface, which means that overloads can occur very quickly. Particularly at "rush hour" around 8:00 p.m., severe cuts can be observed even with perfect reception conditions. One reason why the throttling practice is unfortunately necessary in general. Nevertheless, one represents Good radio connection is the most important basis for an interference-free and stable connection.

If you are planning to order your own LTE connection (see home tariffs with LTE), you should assess and take into account all the important parameters from the outset. To do this, it must be known which factors negatively affect the radio link and which countermeasures could be effective. In the following we want to show you in detail which these are. Here we go!

1. negative factors influencing the reception quality

The biggest problem with a wireless connection is simply the distance. Just a few meters after being emitted from the antenna, the field strength of the emitted wave decreases drastically, as the following diagram shows.

Diagram 1: Free space attenuation according to the Friis formula

After only one meter, the signal strength drops by 30 dB. That corresponds to a reduction to a thousandth! However, the radio wave is attenuated less and less with increasing distance, the curve follows a logarithmic function. Nevertheless, the reception power that ultimately has to be picked up and used by the respective recipient is very low. A very common reception value of -100 dBm corresponds to a power of 0.0000000000001 W = 1-13 W = 1 pW (picowatt). It should now be clear to everyone why this delicate connection needs some attention. A further weakening this reception performance comes about when the Line of sight is interrupted or the receiving device is in a building (with insulation & heat protection glazing). In this case, the radio waves have to overcome an additional obstacle.

1.1 Problem when operating a terminal device inside an (isolated) building

Apart from the weakening of the LTE reception signal when entering the building, the radio waves are further absorbed and reflected each time they hit another obstacle in the room. These reflections then form what is known as an interference pattern; the same signal then occurs several times in space with different transit times. This can lead to overlapping of the radio waves, which alternately add up or can also be canceled. The problem with adding the waves is that it is signals with different transit times that have been superimposed. In the event of extinction, there are dead spots in the middle of the room.

It is best to place the LTE router near the window

The problem with the different transit times can also cause it to higher ping times, because the end device always has to check which signal is "the best" and the most up-to-date.

Furthermore, there is the possibility that the reception level fluctuates due to the cancellations, which of course also applies fluctuating data rates can lead if the reception level becomes too bad. These fluctuations can be particularly strong if the interference pattern that forms in the room changes. For example by modifying the objects or people in the room (movement). This "disturbance" then causes a permanent change in the fields. Opening a door or crossing a room can be such a disturbance, for example.

As for the received signal (downlink), these things also apply to your own transmission signal (uplink). Before it can spread in the direction of the base station, it is attenuated by the masonry or reflected x-times. Exactly the same interferences, cancellations and runtime shifts are formed. At the same time, these interferences have an effect on the quality of the connection. Since your own transmission signal is the weakest link in the entire signal chain (no MIMO, low transmission power, smaller antennas), the effects of the upload can be even more drastic.

1.2 Several base stations nearby

In principle, it is desirable for a network provider to provide a very close-knit network of base stations. That means good coverage and creates capacity for many users - the cell utilization is reduced as a result. So more transmitter locations mean only good things for the stability and data transmission rate of an LTE connection !? You already guessed that this is only half the story. Unfortunately, there are also negative implications, which are particularly noticeable among users who want to use a very high-bit-rate data connection.

So what's the problem? All base stations of a provider use the same frequencies. If 2 base stations are now approximately the same distance, this can affect the performance of your own connection somewhat. First of all, your own device is only ever connected to one base station. All signals from this station can be "understood" and all "own data" can be filtered out as normal. However, the radio signals from the other station are "foreign" and cannot be processed by the terminal. These signals thus act as interferers, which fall into the frequency channel of their own connection. The result is that the measured RSSI increases, while the RSRP remains the same. So the SINR and the RSRQ decrease, which consequently deteriorates the connection quality. More about this here in the first part of our reception special.

1.3 other influences

Unfortunately, the weather can literally thwart your LTE connection. Inversion weather conditions (fog), heavy snowfall or rain, sometimes considerably hinder the propagation of radio waves. The same applies to obstacles between the imaginary line of sight from the transmitter to the receiver (i.e. you). A level line of sight is considered ideal, which unfortunately is only possible in the rarest of cases. Common obstacles are forests, hills or tall buildings such as churches. With our height profile tool, you can at least make topographical obstacles visible and analyze them.

By the way, forests are particularly a problem when foliage begins in spring. Then an otherwise perfect connection in winter can suddenly only show a fraction of the performance. In this article, however, we show that a lack of line of sight does not necessarily have to be a problem.

2.1 The perfect antenna position

internal paddle antennas on the Easybox 904 LTE router

Regardless of whether you use an external external antenna or the internal (e.g. paddles on the router) device antennas. A lot can be achieved with a "good" antenna location.

But what does good mean? Basically, the antennas (or the end device when using the device antennas) should be positioned as high as possible. Especially when there is no line of sight, every gain in height is worth striving for. This is the only way to get out of the diffuse stray field of the wave diffraction area and into the vicinity of the direct signal. External antennas should always be installed outdoors and as high as possible.

Directional antennas must be precisely aligned with the base station. With LTE's MIMO functionality, the maximum possible data rate in the downlink can be almost doubled. To do this, it is necessary either to use a MIMO-capable antenna or to work with two individual antennas. These should each be mounted offset by 90 ° in their polarization. If the antenna mast is the highest point on the building, sufficient lightning protection must be ensured! In general, by the way, the simple formula that the most expensive antenna is always the best solution does not apply. Like you for every need find the optimal LTE antenna individually, you can find out here in this PDF.

Advantages of using an external LTE antenna

The greatest advantage of an antenna in the open is hidden behind the possibility of a free choice of the really best possible location. While the simple end device with the internal antennas is pretty much fixed in terms of location (for example with regard to power supply / WiFi range), an external LTE antenna can also be installed at the highest point of the building (see also height profile tool). The better positioning (outdoors & at a good height), as well as the likely existing antenna gain, usually more than compensate for the losses of the antenna cable. Even with 10 to 15 meters of antenna cable, an improvement in reception of 15… 20 dB is quite realistic. Of course, this can be further optimized by using high quality cables. Unfortunately, these are also quite expensive.

In principle, almost all reception problems that were mentioned at the beginning can be eliminated with the help of an external antenna. By installing it outdoors and at a suitable height, problems that arise within the building, in the form of interference, can be completely eliminated. In addition, an antenna works much better in this position and when there is no line of sight, as the proportion of the direct signal increases with every meter gain in altitude. When using a directional antenna, other interferers that are not in the opening angle of the antenna, such as other base stations, can also be masked out.

Conclusion

• When using indoor receivers, ensure that they are exposed and close to the window,
• If possible, install a suitable external LTE antenna, but make sure that the cable runs are short,
• align them optimally on the transmission mast -> this is how it works.

»Advisor" Improve reception with LTE "
»Significance of the RSRQ value for interpreting the reception quality
»Carry out a speed test
»Build your own LTE antenna - instructions
»How fast is LTE?

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