How to connect a small municipality far from fibre routes

This is nothing new: consider the structure of municipalities in the Czech Republic, with a large number of small municipalities that have fewer residents. Almost 3,500 municipalities have fewer than 500 inhabitants. How do operators calculate the cost of laying an optical connection network in municipalities of this size?

The market potential in a municipality of 500 people must be divided by 3, which is the average number of members of a household in the countryside.  Of these roughly 166 households, an optimistic 30% will connect. That puts us at about 55 customers with an expected bill of between CZK 300 – 500 per month. Please note that this is definitely not profit: the amount includes VAT, fixed costs, the costs of services in higher network layers, and equipment at the customer's premises. The construction cost of an fibre network has a metric proven in practice. A metre costs CZK 1,000, a little less in open terrain, which is why the cost of an easement for laying the network is also factored in. These are multi-million investments, so it is at least clear why we are asking for grant money from the European Funds specifically for connecting remote municipalities. The analysis by the Ministry of Industry and Trade (MPO) showed that no telecommunications cable, nor even a prepared duct, leads to one thousand municipalities. Yet even small municipalities without a cable connection commonly have telecommunications services available. How is this done? By radio links, which transmit data between two points using directional parabolic antennas. This is a technology that is developing rapidly, and its possibilities are growing enormously. So that you can understand how professional radio links work, I will briefly explain the principle of communication in an optical fibre.

Glass fibres carry electromagnetic waves of a very high frequency, namely light. More than one colour of light, i.e. wavelengths, can be inserted into the communication medium. The medium for signal transmission is glass, and the signal transmitter is a laser. In addition to the stability of conditions for signal propagation, another advantage of glass fibre is the large bandwidth that laser sources can use when modulating signals. The basic telecommunications principles can be expressed for laypeople in a simple relationship: the greater the usable bandwidth, the greater the transmission speed at the same modulation rate. What does the word modulation mean? Imagine smoke signals. Smoke is there, or smoke is not. Two states. If you need to transmit a lot of information using two states, you will suddenly need many smoke fires. That is exactly what bandwidth is. Increasing the number of states increases the transmission capacity, but reduces the observer's ability to distinguish individual pieces of information. With several clearly separated signal sources, the observer is able to recognise information with high sensitivity and accuracy and pass it on.

In the case of transmission technologies, the signal source is a modulator and the observer is a demodulator, just as with the optical transmission medium. In the case of radio communication, the transmission medium is air.

The biggest disadvantage of radio data transmission is the limited bandwidth. Technically it is no problem to use wide channels with professional equipment, but we have to adapt to other uses – the frequency spectrum is quite crowded. Only in the last decade has the new frequency space of millimetre waves begun to be used industrially on a mass scale. The disadvantages of these bands are perfectly offset by the available bandwidth, which, similarly to optical communication, runs into the units of gigahertz. Previously it was extremely expensive to build equipment capable of communicating at frequencies in the tens of gigahertz, with sufficient stability and the high power needed to overcome increased attenuation during rain. Today it is a commodity: a professional radio link with a transmission capacity of as much as 10 Gbps can be bought for a few hundred thousand CZK. The condition for successful operation of such a link is an acceptable distance between the points. Stable links that are insensitive to rain work up to a distance of around 3 kilometres; with a backup in a lower band, they are built up to a distance of roughly 8 kilometres. Thanks to their physical properties, the problem of mutual interference does not arise, which is why their use is free of charge after registration with the Czech Telecommunication Office (CTU). For installation points, a fixed boom must be used. Direct line of sight between the data transmission points is absolutely essential. In the Czech Republic, the 71–86 GHz band is used for these purposes. More than 7,000 such links are currently registered.

How about longer distances? Professional links on traditional, lower frequencies have also undergone remarkable development. Because bandwidth is limited in these, development has gone down the route of increasing the modulation rate. Remember the two states of the smoke signals? Modern communications technology can handle 4,096 states. And to top it all off, it can also insert several carrier frequencies that are phase-shifted relative to one another, so as to multiply the transmitted capacity without increasing the fee. Even so, long-distance transmissions are limited in capacity compared with the millimetre bands. For affordable 112 MHz XPIC equipment, a transmission capacity of 2 Gbps is envisaged. The advantage is the ability to transmit data between points as far apart as even 20 kilometres, with resistance to any rain. Don't believe it? Mobile networks also use radio technologies on a large scale: up to 80% of repeaters are connected by a professional point-to-point link. With further relaxation of the regulatory restrictions applying to classic, non-millimetre bands, we expect transmission capacity to rise to 5 Gbps, with a time horizon of 2024. The technologies are ready and available. Why are high capacities not available on radio links in all municipalities and at all mobile repeaters? With the exception of specific short-range bands, operators are obliged to pay licence fees to the state. There is a direct proportion between the fee and the bandwidth, and the fees collected by the state are by no means low.

As mayors of municipalities, you can contribute a great deal to speeding up internet services in your municipality. Simply order from the town hall a service that enables the local provider/operator to recover its investment in the connection network. The fibre network will eventually be brought in, whether through coordination with the region, a grant from the European funds, or because a corporate customer is found who needs a connection backed up more than once.

Jakub Rejzek

The author is president of the largest association of providers of fixed connections to electronic communications networks, Výbor nezávislého ICT průmyslu z.s. (Independent ICT Industry Committee). As an expert, he is a candidate for the Central Bohemian Regional Council, with the aim of removing barriers to the construction of technical infrastructure and coordinating construction with public investment. He has experience in digitalisation processes and data collection, and supports transparent processes based on open data available to the general public.

We also recommend reading the article Benefits of a fibre connection.

Updated 15 April 2024