In its most recently published "Hype Cycle", the renowned business consultancy Gartner sees 5G at the zenith of exaggerated expectations. The focus of mobile operators is primarily on the mass market and secondly as a replacement for ADSL in rural areas. The selling point is Gbit/s.
Mobility is a central theme of 5G technology. In particular, public transport in urban areas and between city-centers offers a wide range of application options and opportunities. For this reason, 100 Mbit/s were required along rails and motorways for the allocation of frequencies in Germany.
NetModule is represented in these segments with its two product lines NB2800 and NB3800. The added value of 5G lies in the reliability and deterministic behavior that enables real-time and security-relevant applications.
The communication architectures of cars, buses and trains follow the same principles: Separation of safety-relevant communication and infotainment as well as the transition from fieldbus to Ethernet. In addition, for trains, the devices are duplicated and operated redundantly. But even there, the trend is clearly towards 5G. After almost 30 years, at the end of this decade, GSM-R will be replaced with the 5G based FRMCS.
Regional trains already have up to 9 parallel mobile telecommunications systems, each with its own antenna system on the roof. With 5G, MIMO antenna technology is now absorbed, i.e. 9 x 4 antennas and cables. Obviously, there is a need for optimization here, especially since 5G offers via slicing the possibility to strictly separate applications and set independent performance characteristics. Safety-relevant functions are realized by short latency and guaranteed performance features, in parallel entertainment or infotainment can be operated cost-effectively, since now only one system is necessary instead of two. This is, in simple terms, the principle behind 'slicing'. Due to the fact that the same conditions rarely prevail at both ends of the train, it is possible to achieve better performance by combining the two above-mentioned information streams.
The use cases for 5G in public transport are:
- Passenger information
- Passenger WIFI
- Telematics
- Video surveillance and accessibility
- Preventive maintenance
- Charging and battery management for hybrid and electric drive
- High-precision maps with updated additional information
- Support for autonomous driving
- Remote driving and concierge service
LTE or 5G?
Most of these applications can also be implemented with LTE (and currently will), but with limitations. Especially in autonomous driving, it becomes clear that the application depends on the speed of real-time communication. This means that the data speed is necessary to ensure functionality.
Differences 5G (NR) versus 4G (LTE)
The differences in spectral efficiency between 5G and LTE are rather small and of interest for the scientific community. However, New Radio enables deterministic behavior with high reliability and short latency (uRLLC), and that's, what makes the difference:
Both standards are available in frequency duplex and time duplex methods. This means that for speech and hearing, either different frequencies or successively different time slots are used. Simultaneous speech and hearing create interference and makes decoding more difficult, but with 5G it is possible.
One of the key differences is that 5G was developed for MIMO, while MIMO is an option for LTE. This is where channel reciprocity comes into its own. When sending and receiving at the same frequency, the determination of the channel parameters is much simplified. The base station can combine 64 receiving and transmitting antennas into one sector, even more in the millimeter wave range. Mathematically, the whole thing can be regarded as beamforming.
MIMO should not be confused with reception diversity. In one method (diversity) one switches between the antennas and selects the best signal, while in the other (MIMO) one sends and receives a different encoded signal on all antennas. A phase-coded signal then leads to a change in the antenna diagram.
Obviously, the antennas at the base station are larger and the amplifier more powerful than on the end device. The 64 antennas in the urban or 8 in the rural area, stand 1, 2 or 4 antennas vis-à-vis, which do not all send, but can receive.
MIMO works differently than send- and receive diversity. At the base station as well as on the end device there are several antennas for transmission and reception. Unlike LTE, where MIMO is just an option, 5G is designed to get the most out of the transmission. The price to be paid is a large number of antennas at the base station and on the device. However, the higher the frequency, the smaller the antennas.
The table shows the theoretical maximum data rate, if 100 MHz were fully available. However, at 3.5 GHz only 70% of this is available for the downlink and 20% for the uplink.
These are theoretical values according to the standard TS38.306, these values should be tested under realistic conditions.
Reliable real-time communication (uRLLC)
For commercial applications, 5G's unique selling point is the reliable real-time communication. Of course, the radio connection isn't quite real-time, but deterministic behavior is achieved, while LTE still feels like ADSL to end customers. Of course, LTE also works well, if you use language with 12.2 kbps over a Cat.6 connection.
But it is not just about the air interface, because in the communication chain the overall result is only as good as its weakest link. While the 5G air interface is called "New Radio", a whole new architecture of the core network, the Next Generation Core Network, arises in the shadows. This is no longer hierarchical, but applications are hung on a bus in parallel. This makes it easy to add new services without letting the previous house of cards collapse. Slicing is then the ability to run these applications in isolation from the device, via the air interface, from the transmission network to the core network. In comparison, the LTE core network (EPC), which is based on IMS, has proven to be too complex to simply try out new services.
Mobile operators are still shying away from investment in the new core network. The so-called "non-standalone architecture" is a hybrid, in which the data streams in the middle are led out of the 5G base station and then forwarded to the existing LTE-base station and the core network. New applications and real-time communication are not possible in this way.
Radio coverage is a necessary but not sufficient condition
Roads used to be built first and then they were filled with cars. But would that work for 5G? Is it sufficient to suggest ubiquitous coverage that people switch from LTE to 5G? It is undisputed that network operators first must offer 5G coverage before an ecosystem can be built. There is no hen-egg dilemma here. The price of high data rates is more bandwidth in the higher frequency bands and consequently smaller cells are obtained. In the case of public transport, this means an explicit coverage along roads and trains.
High data rates, as expected at 5G, need a certain signal strength. To transfer 8 bits at 256 QAM versus 6 bits at 64 QAM per symbol, you simply need more power, especially at the edge of the cell.
While GSM was still slightly above the television spectrum, 5G enters the range of millimeter waves, because there is still a free spectrum for relative wide channels. The price you need to pay for this, is high. Cells were in the rural areas still in the order of 10 km, one has to accept only hundreds of meters at 3.5 GHz. For the musician and physicist, it is understandable: with every octave you lose half of the range. Therefore, the mobile operator must invest more in infrastructure. It is then seducing to offer the label fraud 5G in frequency bands, where the propagated data rates simply cannot be achieved.
Timing
There is now a 5G-capable iPhone and also 5G router (CPE) for home use. Obviously, we are still in the early stages and the question that arises is: when will we have a self-supporting ecosystem? In a January 2020 study "The 5G Era - New horizons for advanced electronics", McKinsey writes that the market development will take place in waves. The consumer segment will achieve its first state of maturity in 2022. The blue circle in the drawing shows the relative business potential. This wave is followed by applications of reliable real-time communication. The third wave will culminate in 2025 and affect IoT applications. The whole thing seems to be in the future, but the basics - the radio supply and the 5G core network - must be created today.
Why does NetModule first offer a 5G evaluation router and the finished product later?
There are a few basic questions that need to be considered before an introduction:
- What is the coverage level along the transport route?
- Is it possible to reach the desired data rates in uplink (end point to infrastructure) and downlink (infrastructure to the end device)?
- What is the optimal antenna installation for MIMO to work in the receiving and transmitting path?
- Is it possible to install the router to minimize cable losses?
- Is 5G really better than LTE in practice and is it worth the investment?
Starting with the last question, we have to admit that in many cases the router will not work in 5G mode at all but will fall back on LTE or sometimes even UMTS due to the coverage problem discussed above.
Minimizing the cable length or the direct connection of the router to the antenna are options to check. Active antennas have been discussed for some time and the evaluation router can provide the necessary basis of experience.
MIMO is the key to achieving the desired data rates. Here, Network operators have some experience on the base station side.
The practical experience regarding the vehicle is lacking. A subsequent check of the entire installation is often not feasible. Now our evaluation router can be used in because it allows to test the performance and applications in advance.
A typical driver for 5G would be the use of video surveillance on trains or buses. High-resolution cameras generate high data rates and require some synchronization so that the image does not flicker or jerk. In any mobile communication technology and also at 5G, the communication between the terminal device and the base station is the Achilles tendon, which must be properly dimensioned.
The data sheets of 5G smartphones show optimistic data rates. In practice, these are probably lower, even under the best conditions. However, for planning and implementing of a service in public transport, it is essential to know how much of the data rates are left in practice, in order to build a functioning business model.
The NetModule 5G evaluation router is based on the proven NB2800 and NB3800 router models. The modular architecture of both product lines enables the functional integration of 5G modem modules due to standardized interfaces. This router provides the user with a tool to prepare effectively and efficiently for the installation and application of 5G routers on public transport.
Conclusion
5G will absolutely contribute to global economic growth. However, there are not only advantages, such as shorter latency times and maximum transmission rates – but also challenges, which need to be considered. Benefiting from 5G also means preparing properly and investing only when it is worth it!
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