On 2G/GSM, the whole network would drop for 30 minutes, just zero reception on the phone.
On 3G, you'd have reception but calls were impossible and texts mostly failed.
On 3G+HSDPA, texts also worked fine but data became unusable as people sent fireworks photos
On early 4G, not much changed from HSDPA since the networks were busier from more people using smartphones and social media
On LTE Advanced and 5G it's all a non-event now, everything works fine
On 2G/GSM, the whole network would drop for 30 minutes, just zero reception on the phone.
On 3G, you'd have reception but calls were impossible and texts mostly failed.
On 3G+HSDPA, texts also worked fine but data became unusable as people sent fireworks photos
On early 4G, not much changed from HSDPA since the networks were busier from more people using smartphones and social media
On LTE Advanced and 5G it's all a non-event now, everything works fine