What kind of 5G base station is in a light pole?
The coming 5G mobile network technology promises faster transmission of larger data volumes and with lower latency times. In Orbis, we have been following the technological development and discussing with our partners what will be the mobile network base stations and network installation like in the future.
For example, if we think of the self-driving vehicles to be able to operate, they need a new kind of infrastructure and network construction. Wireless network will transmit the data needed by the cars and thus will have to cover the routes they travel. Communication must work extremely reliably in order to make this critical application trustworthy. 5G technology meets this need.
In network installation, 5G limitations are mainly defined by two technical features. First, higher frequency of the signal shortens the signal range, which means the positioning of base stations is denser – ‘like streetlamps’. Secondly, the network latency (meaning the delay that happens in data communication over a network) cannot be more than 1 millisecond in 5G. This means that data cannot be transmitted too far for processing, therefore small data centers are needed near the operating network.
Light poles are short
The typical height of a base station today is 30-150 meters. Light pole, instead, is only around 6-10 meters high. When a 5G base station is placed in a ‘streetlamp’, its antenna is located much lower and therefore the coverage area of the base station is smaller. Also, due to radiation safety, high-power radios are not suitable for light poles.
Less room for technology in the light pole
Today in Finland, there may be up to 15 radios and thus at least 9 antennas in a single base station mast. Typically, one radio unit serves one technology of one telecom operator (e.g., 2G, 3G or 4G). The more telecom operators and technologies, the more radios, antennas and cables in the mast. 5G radio unit has an integrated antenna, which decreases the number of cables when RF jumper cables are no longer needed.
In the example case of the self-driving vehicles, base stations will be placed to lighting poles. There will be probably 2-3 antennas per pole aligned parallel with the road. To work, the radios need both power and fiber optic cabling as well as enclosures for cable connections. Because the cabling inside the pole requires a certain amount of space, the diameter of the pole will inevitably grow larger than in the traditional light pole.
Challenge to ensure power supply
Reliability requirements for the base stations call for the possibility to make emergency calls even in cases of power disruption. The radio units mainly operate with 48V DC power, because this way their operation can be ensured with UPS batteries in case of disruptions. Adding batteries and rectifiers to the light pole increases the size remarkably.
Alternatively, electricity could be converted into alternating current, but this would require the use of rare radio units suitable for AC power. Whether the power backup requirement remains applicable to the entire 5G network remains to be seen.
One cabling solution for multiple services
Cabling for the light pole can be compressed into a smaller space by combining the power supply and data transmission either in a hybrid cable or in a common enclosure. The complete, ready-to-install set is designed to fit different kind of poles and to speed up installation. Orbis OptoMast Smart CityTM is a durable, weatherproof product family designed for this purpose.
When the power and data transmission cables are installed for the base station, the pole can be expanded to a so-called Smart Pole that provides services through different applications. For example, the pole environment can be monitored with sensors that deliver information and based on that e.g. information the sensors provide the remotely controlled led lights light road users way.
Active devices in the base station
Baseband unit (BBU) is an active device that processes the signal from the radio unit and transmits it to the mobile network. Traditionally, BBU’s are placed in the cabinet under the mast.
In a light pole application, the space required by these devices is so large that in practice the batteries, rectifiers and BBU’s must be placed in a cabinet located at the bottom of the pole. In the urban areas, the cabinet can be disguised as a bench, but along the roads of self-driving cars other solutions must be used.
Another option is to collect BBU’s of several base stations and take them a little further into a common BBU hotel or data center. This solution is called the C-RAN architecture.
Each radio unit requires one pair of optical fibers for data transmission. However, it makes no sense and it is costly to dig countless amounts of cables to the ground. C-RAN uses WDM technology to transfer data from multiple radios in the same fiber. When selecting components for the fiber optic network, the technical options are also limited by the latency target of the 5G network.
When are the 5G base stations coming?
Best practices are being developed and pilot networks for testing have already been built. In commercial use, telecom operators will first add 5G technology to existing base stations and to a few selected locations where new technology is utilized. The time of driverless vehicles is only after several years. It is not likely that 5G network will be built to cover the all areas in the country. The focus is on the urban areas where there are enough users and use cases from the business point of view.
Writer: Paula Meuronen, Orbis Oy
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