Which network is Helium Mobile on?

Excuse me, could you please clarify which network Helium Mobile operates on? I'm curious to understand the underlying technology and infrastructure that supports this mobile service, especially given the growing popularity of Helium and its unique approach to decentralized wireless networks. Could you elaborate on whether it leverages existing cellular networks, or if it operates on a completely different, perhaps blockchain-based, framework? Your insight would be greatly appreciated.