If you know the results of the ratings of mobile operators developed by our website, you are well aware that the average data download speed is about 10 times lower than the maximum values announced by the operators. It can be assumed that the average data download speed through the LTE network in Poland is 20 Mbit / s. But recently I had the opportunity to see that it could be better. I have just finished my trip around Krakow, where I checked how LTE works in the small town of Skavina.
We connect mountain cities with poor coverage and slow internet. We also often hear the opinion that LTE-Advanced base stations (ie those that support frequency combination) are located only in large cities. Therefore, it is widely believed that mobile networks work well only in provincial cities. I use LTE in Wrocławda on a daily basis and I can’t complain about the lack of coverage. Therefore, when traveling around Poland, out of complete curiosity, I check how fast the Internet is in different cities. Results vary, but they often fluctuate around the average speeds seen in monthly rankings. However, there are exceptions. Yesterday I went around Krakow and passed Skavina to a local gas station to refuel my car. By the way, I looked at the smartphone screen and saw “full range” LTE. So I immediately launched the SpeedTest mobile app to check my internet speed.
LTE networks are fast, but we don’t see that
The result is 80 Mbit / s for download and 35 Mbit / s for sending on a slightly outdated old Samsung Galaxy S4 mini. This device has a Category 4 LTE modem, so it works only on the classic 4G network without frequency accumulation. However, this does not surprise me. At 1:38 in the morning, it is unlikely that anyone uses a smartphone, so I was the only person who generated more traffic at a nearby base station. When I returned to Vroslava, I realized that I wanted to check some details about this transmitter. The BTSearch portal helps here.
The Play network station, located near the gas station in Skawina, supports all available LTE frequencies for the operator: 800 MHz, 1800 MHz, 2100 MHz and 2600 MHz. After a transfer speed of about 35 Mbit / s, I almost used a band dedicated to a frequency block with a bandwidth of at least 15 MHz in the LTE network. Information on frequency reserves can be found on the UKE website. They show that the Play network has such blocks in the 2100 MHz and 2600 MHz bands. The 2100 MHz band is shared between two technologies (3G and 4G), and the base station under analysis uses two 3G channels in this band. This means that during the test, I used a frequency of 2600 MHz, which is a block with a width of 20 MHz. While downloading the data, I got a result of 53% of the maximum speed, in this case 150 Mbit / s. However, this ratio was better at the time of shipment, ie. 70% of 50 Mbit / s.
LTE networks are fast, but have limited capabilities
There is a fundamental difference between what we expect and what we receive. In advertising materials, operators provide the maximum data download speed that can be achieved in practice, but only in special cases. Let me complete the analysis of my sample. During the car trip, I was transferred between the base stations of the operator. When I was within range of a multi-system base station, my device switched to a frequency that offered the fastest Internet speed. So, I switched to the so-called capacitive range, ie already mentioned 2600 MHz. However, during data transmission, the base station assigned me most of the resources of a particular sector. This means that there were other users’ devices in the same sector. And here we come to the essence of the matter. The total data transfer rate of all users in a given sector is called capacity. In practice, this value cannot exceed the maximum theoretical data download speed of 150 Mbit / s (or 200 Mbit / s with 256 QAM modulation) for a 20 MHz block. For narrower radio channels, this value is optionally lower.
In turn, the sum of the capacities of all sectors in a given frequency range is the capacity of this band. The more of these sectors, the greater the capacity. Therefore, operators use sector antennas, which allow them to serve more customers. If we add the capacities of all the bands supported by the base station, we get the capacity of the base station. At this point, we face another limitation. The capacity of the base station cannot exceed the bandwidth of the gateway used. It can be wired (for example, optical fiber or twisted pair Ethernet) and wireless (radio connection). At the current stage of development of the LTE network, we face a situation where the capacity of the base station is limited not by radio technology, but by the transition to the backbone network. Unfortunately, it is not possible to connect optical fibers everywhere, and only some base stations have radio connections with a capacity of 1 Gbit / s. That is why mobile operators are investing in the backbone infrastructure needed to build a high-speed LTE network and in the future to expand 5G.