946 publications from this institution
Wireless communication systems must increasingly support a multitude of machine-type communications (MTC) devices, thus calling for advanced strategies for active user detection (AUD). Recent literature has delved into AUD techniques based on compressed sensing, highlighting the critical role of signal sparsity. This study investigates the relationship between frequency diversity and signal sparsity in the AUD problem. Single-antenna users transmit multiple copies of non-orthogonal pilots across multiple frequency channels and the base station independently performs AUD in each channel using the orthogonal matching pursuit algorithm. We note that, although frequency diversity may improve the likelihood of successful reception of the signals, it may also damage the channel sparsity level, leading to important trade-offs. We show that a sparser signal significantly benefits AUD, surpassing the advantages brought by frequency diversity in scenarios with limited temporal resources and/or high numbers of receive antennas. Conversely, with longer pilots and fewer receive antennas, investing in frequency diversity becomes more impactful, resulting in a tenfold AUD performance improvement.
This paper describes the first available 5G testbeds as designed by 5G CHAMPION, a collaborative research project undertaken by over twenty consortium members and targeting the provision of 5G services at the 2018 Winter Olympics in Korea. In order to provide 5G services such as augmented reality (AR), virtual reality (VR), high quality, interactive multi-player video games, the testbeds shall fulfill the challenging requirements such as ultra-high data rates, ultra-reliable low latency, and mass connectivity. To meet such requirements, revolutionary testbed architectures are proposed, designed to be flexible, cost- and energy-efficient, through adopting state-of-art multi-radio access technologies (RAT) in client devices and in the network. The testbeds will also provide mmWave wireless backhaul, an interoperable and seamless connection between two different access networks located in Europe and on the site of the Korean Winter Olympic Games.
