Advanced signal processing helps 5G achieve speed targets
Mobile phone infrastructure was first introduced in the late 1980s. Since then, it has gone through several generations, each faster and more capable than the previous. Now we are up to generation five, or 5G. The current generation, 4G, works well for individuals, but can suffer bottlenecks when large groups of people in the same area use a network simultaneously. The new standard solves this congestion problem, potentially offering a 1 000x capacity improvement compared to 4G. Nevertheless, this is essentially a theoretical possibility. Achieving it will depend on the future availability of certain technological improvements. In contrast to other groups studying the possibility of moving the 5G radio band from below 6 GHz to above 60 GHz, the EU-funded ADVANTAG5 project addresses the bandwidth problem by introducing directionality to the radio beam transmission. This research was undertaken with the support of the Marie Skłodowska-Curie programme. Regarding radio communications, a range of radio frequencies is called a band. Each user, or antenna, is allocated a certain small slice. It is like how individual radio stations are described as broadcasting on a certain allocated frequency (called centre frequency), yet in fact they broadcast slightly to either side of that as well. “In current systems,” explains project coordinator, Dr Marko Kosunen, “only one centre frequency can be used at a time, because otherwise transmissions would interfere with each other.”
Beam directionality via signal processing
The ADVANTAG5 approach allows duplicate use of each frequency by introducing controlled directionality to the transmission and reception radio beams. The beamforming is achieved via new signal processing methods, developed by the project. These methods involve the processing of multi-user digital signals via the project’s special new silicon chip. Signals received at the antenna, which in this case means a mobile phone tower, carry information from all users from different directions. Yet, this is filtered so that each of the multiple signals produced by the signal processing element contain only information of a specific user.
New antennas aid processing
The control of the beam direction is aided by the new beamforming receivers, specially developed by the team. These work by controlling the sampling of received signals, and by combining the signals received via different antenna paths. ADVANTAG5 also developed efficient digital transmitter structures, which support multiple channels broadcast from a single antenna. Researchers successfully demonstrated the new methods as well as the new equipment, which includes transmitters and receivers. The results are now available for industrial uptake, and the industry has shown strong interest. In the meantime, the team will be refining the design further. The methods developed during the project will be incorporated into the teaching of communications engineering courses at Aalto University, Finland. “I really see our work as a game changer in terms of electronics design in future,” says Kosunen. “It combines circuit development and optimisation by programmatic means, eventually with machine learning, in a way not seen before.” This work will help proposed 5G infrastructure operate at its promised speed. For users, this will greatly accelerate data rates.
Keywords
ADVANTAG5, radio, 5G, antenna, signal processing, 4G, mobile phone, communications, bandwidth
