MOOC on 'Ultra-dense Networks for 5G and its Evolution': Challenges and lessons learned - Lopez-Morales, M. J.; Urquiza-Villalonga, D. A.; Gonzalez-Morin, D.; Nidhi; Khan, B.; Kooshki, F.; Al-Sakkaf, A.; Leyva, L.; Farkhari, H.; Medda, D.; Seitanidis, I.-N.; Abu-Sabah, A.; et al. (2022 31st Annual Conference of the European Association for Education in Electrical and Information Engineering (EAEEIE), 2022)