The HSS (Home Subscriber Server) is the concatenation of the HLR (Home Location Register) and the AuC (Authentication Center) â two functions being already present in pre-IMS 2G/GSM and 3G/UMTS networks.
Three Days Grace's music has been described as post-grunge, hard rock, alternative rock, alternative metal and nu metal. Their self-titled album mostly uses the sounds of alternative metal and post-grunge. However, on their second album One-X, the band had more guitar solos and a more melodic sound.
The rock hard encyclopedia arranged the band musically between Scorpions and Accept. According to Manfred Meyer from Metal Hammer, some would rank the band alongside Accept and Scorpions as the third most important hard-rock band in Germany.