This book constitutes the refereed proceedings of the 4th International Conference on Wired/Wireless Internet Communications, WWIC 2006, held in Bern, Switzerland, in May 2006. The book presents 29 revised full papers, organized in topical sessions on wireless networks, UMTS and OFDM, mobile ad-hoc networks, power saving and sensor networks, voice and video over wireless networks, mobility, TCP, signalling, charging, and security.