Cellular wireless systems from 2G to today’s 4G have been continuously evolving towards offering broadband connectivity to the users. While the trend of reaching even higher rates will continue in the fifth generation of wireless systems, there is a common consensus that 5G will not only be “4G, but faster“, but it will offer new modes of connectivity to a massive number of simple devices and/or support extremely reliable connections. WILLOW was a precursor to this consensus, as its research plan was proposed back in 2014, when the notions of massive and ultra-reliable communication were in their infancy.
It is very rewarding to see that this plan has become one of the central elements on the global research agenda for wireless communications in relation to 5G systems and beyond. Namely, since 2014 Massive machine-type communications (mMTC) and Ultra-reliable and low-latency communications (URLLC) became two of the three pillars of 5G and the main arguments for the digital revolution brought by 5G and the other emerging wireless systems. Figure 1 was originally part of the WILLOW proposal and it turned into one of the most recognizable graphs that describes the operation of 5G systems. The prevalence of these research topics is seen in the surge of special issues, workshops, and papers dedicated to massive and-or ultra-reliable wireless communications for Internet of Things (IoT). It can thus be confidently stated that WILLOW made a major contribution to the worldwide research agenda on wireless communications. This is seen through the more than 80 publications that came out of the project, some of which already have a large number of citations.
The objective of WILLOW has been to investigate the fundamental wireless schemes and protocols for massive and ultra-reliable lowband connectivity, now widely known as IoT connectivity. The avaliability of IoT connectivity for massive number of devices, as well as support for IoT connections with ultra-high reliability, will introduce disruptive changes in the vertical sectors: energy, transportation, industrial production, health, etc. For example, once ultra-reliable wireless connections are available, the notion of a robot changes from a single physical entity to a distributed group of modules that are wirelessly collaborating towards performing the robotic function. This paradigm fits in the emerging concept of Industry 4.0 taht consists of smart interconnected production facilities.
5G is quickly becoming the foundational digital technology in the world and WILLOW made pioneering contributions to the two novel aspects of 5G, massive and ultra-reliable IoT, which is an indicator for a large potential impact on the society.