The author is the head of technical and infrastructure department at German national public broadcaster Deutschlandradio.
The reception of radio programs with smartphones is becoming increasingly important for radio makers, particularly due to young people’s tendency to use their hand-held devices for a wide range of purposes — information and entertainment, social media networks, smart home and smart speakers, amongst others.
There is no doubt that broadcasters have to be present on that platform with both linear and non-linear audio, with social media and the various functions of the internet.
At first glance, 5G broadcasts seem to be a promising solution for the future of broadcasting, and a viable solution to bring radio to the smartphone — one device and one transmission standard on one transmitter network. But who will benefit from this — the user, the mobile network operators, radio broadcasters or the industry as a whole?
Physical laws for radio communication are still valid for 5G as for DAB and all the other broadcasting and telecommunication schemes. From the well-known Shannon limit of 1948 we know that a minimum of energy per bit is necessary in order to provide an error-free transmission over a channel with a certain bandwidth (Eb/N0 = −1.6 dB in AWGN-Channel).
New and very efficient transmission systems like 5G are able to transmit very high data rates in a channel of a certain bandwidth, however, the energy per bit will never fall under the minimum defined by the Shannon law. With other words, the higher the data rate of a transmission system, the higher the signal-to-noise ratio required. This means in practice for a certain transmitting power the size of the transmitter cell will be reduced for higher data rates accordingly.
Now, from a theoretical point of view with respect to the energy per transmitted useful bit (including all the overhead), there is no significant difference in performance between 5G modulation schemes compared to the still very robust system of DAB+.
The 5G broadcast mode provides also a robust QPSK modulation to make use of bigger cell sizes. However, the expected performance compared to DAB especially in a single frequency network is rather the same. In fact, there are no results of a system comparison in the field available and therefore it is reasonable to focus on other basic differences between the idea of 5G broadcast and conventional DAB+ broadcasting.
Today, DAB radio receivers have an external antenna as well as car receivers. In comparison to a smartphone with a less sensitive built-in antenna, the link budget for the required field strength differs at minimum of 15 dB or even 20 dB and more.
This means that in order to achieve the same coverage for radio reception by smartphones, 10 dB more transmitting power is required. This is also true for 5G broadcast networks, so that 5G broadcast networks for smartphone reception have to aim for 10 dB more transmitting power compared to a conventional DAB+ network. In practice, this means that a significantly denser transmitter network is required for 5G broadcast to smartphones than for conventional DAB+.
The reduction of the transmitter distance can be anticipated easily from the CCIR propagation curves. For example for VHF propagation a loss of field strength of 20 dB corresponds to a reduction of the distance to the transmitter from 30 km to 10 km.
With the basic transmitter distance of about 60 km for DAB+ networks, the average transmitter distance for 5G broadcasting to smartphones has to be around 20 km. In fact this means that the transmitter distance has to be reduced by a factor of three in order to overcome a loss of 20-dB field strength. This means nine times more transmitters in the area are required in order to achieve the same coverage as a conventionally planned DAB+ network. Can radio broadcasters really afford this? In fact round about 10 dB more transmitting power results in 10 dB more money.
For the time being, the national DAB multiplex in Germany comprises of 130 transmitters in a nationwide SFN. Today, coverage stands at around 95% for mobile reception, but in order to reach 99% coverage, the number of transmitters has to be increased to 250 at least and may be around 400 (including small gap fillers) in the long term.
With 5G Broadcast round about 10 times more transmitters will be required which might sum up to 2,500 or even 4,000 transmitters in Germany. The mobile network in Germany comprises already 40,000 transmitters today and everybody experiences that this is rather not enough. Concerning 5G mobile networks, experts anticipate that future high data rate networks will be based on a cell size of less than 1 square kilometre, which would sum-up to around 400,000 transmitters in Germany for nationwide area coverage.
What can we learn from these facts?
- The DAB+ network with its low number of transmitters is the most efficient network to realize a full area coverage
- The 5G broadcast networks, the mobile network and future 5G mobile networks require far too much transmitters for a full area coverage that nobody can expect the same area coverage as for DAB radio services
Assume e.g. transmitting costs for a full area DAB network in Germany of about €25 million per year. In order to gain 10 dB more transmitting power for smartphone reception, the network will cost a nationwide broadcaster approximately €250 million per year, as opposed to €25 million a year for conventional DAB. In Germany, no broadcaster is in a position to afford this amount of money — the price for this purpose to reach smartphones with radio is incredible high, and quite frankly, out of reach for any public broadcaster.
If one says that 5G would only be applied in cities as opposed to rural areas, the additional costs would indeed be lower. However, setting aside a budget of €10 million a year for this purpose is also unrealistic for a broadcaster and, should this sum even be available, it would certainly make more sense to spend it on the DAB network, where coverage gaps could be closed, and where broadcasters and consumers could benefit from it.
What’s more, it wouldn’t make sense for a broadcaster to give up nationwide DAB coverage. In order to supply 10% of the area with 5G broadcast to mobile phones for the same amount of money.
So, if broadcasters are far from being able to afford 5G broadcasting, who would pay for this? Mobile network operators will never provide a 5G-radio service for free, and broadcasters will not pay for 5G broadcasting either, so there really is no business model for either.
The one and only solution is that the user pays for the broadcasting service to his smartphone — this could be done by a contract with the broadcaster or with the mobile network operator, something that is already being done today with 3G/4G.
The smartphone user has a mobile contract and pays for the data volume on an individual basis. This enables the mobile network operator to set up very dense mobile networks that have enough power to be received by small smartphones. This works perfectly for radio with LTE and even UMTS, so why wait for 5G broadcasts?
Users already have radio services available on smartphones today, and it works well, so long as the user has enough high-speed volume on his contract.
Today, hybrid radio with DAB+ and Internet via mobile networks or via Wi-Fi at home provides the most suitable solution. Hybrid radio is the perfect fit for all broadcaster and user requirements, as with DAB+ it allows broadcasters the proven and most efficient radio network at an affordable price for area-wide coverage. It allows for free access of the users to radio and information, regardless of whether they live in cities or in rural areas, and whether or not they can afford a high-volume data contract for their mobile phones.
Hybrid DAB radio provides broadcasters with a content distribution platform directly linked to the customers, and independent of the commercially driven infrastructure of mobile network operators. This may be an advantage for emergency warnings, too.
On the other hand, users already have audio streaming and additional non-linear services available on their smartphone via the Internet. So, the only need for radio broadcasters today is to think about attractive hybrid radio services, and an impactful marketing strategy for their brand.
I cannot comprehend why broadcasters and politicians would want to switch a system running with DAB and IP with the more expensive, and in practical terms less efficient system that is 5G. Instead, why not use and extend the existing and approved technology? Hybrid radio is the best approach both economically and in terms of efficiency, and this is unlikely to change in the future.
Diversity between broadcaster networks and mobile phone networks will result in better efficiency and will offer more advantages than disadvantages for broadcasters as well as for users — so proceed with Hybrid DAB and IP. There is no need for 5G for radio broadcast.