WRC2023: A Synopsis Peter Barnett Consultant
digital video compression techniques mean that many television programme channels can be carried in the same bandwidth as one analogue TV channel, and high definition television has become widespread. So what happened at WRC23? On the face of it, very little of immediate importance: broadcasting remains the primary use of the 470 MHz to 694 MHz band, but all European countries are now permitted to use this band for mobile services on a secondary basis. Secondary means its use must not cause harmful interference to the primary service, which leads us to look at coexistence. Coexistence Coexistence means the use of closely related frequencies for different types of service, resulting in both types of signal being presented to the receiver. An example of coexistence is the use of frequencies in the band below 694 MHz for TV, and in the band above 694 MHz, known as the upper adjacent band, for mobile services. When mobile services started using this band, there were many cases of harmful interference to TV, mainly arising from the mobile signals overloading masthead amplifiers and distribution amplifiers. To achieve successful coexistence, in many cases filtering had to be introduced to reduce mobile signals to acceptable levels that no longer caused problems for television.
Every four years or so, the International Telecommunications Union based in Geneva holds a World Radiocommunications Conference (WRC) to revise the Radio Regulations, an international treaty determining the way in which radio systems make use of the frequency spectrum. The most recent WRC, known as WRC23, was held in Dubai in November and December 2023, and was attended by around 3,500 delegates. Among many other topics, it considered the use of the UHF frequency bands used for terrestrial television and international mobile telecommunications (IMT). Most readers will be familiar with the changes to the UHF TV bands that have taken place in recent years: TV signals used to be found across the band from 470 MHz to 862 MHz, but the upper part of that range has now been vacated by TV transmissions, and has been taken over for use by mobile phone systems. The band used by TV is now limited to the range from 470 MHz to 694 MHz. Despite the reduction in bandwidth by nearly one half, we have seen a large increase in the number of programme channels. (Many of us can remember that prior to 1982 we had just three analogue TV channels to choose from!) This increase has been enabled principally by the transition from analogue to digital. Analogue television had several constraints that digital does not need, such as avoiding the use of adjacent RF channels, and requiring relatively high signal to noise ratios. Advanced
Television and mobile networks are fundamentally different from each other.
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