This document develops an analysis of the performance of a VoIP application over W-CDMA HSUPA. It starts by describing fundamental issues about VoIP. Then, it investigates several limiting factors of HSUPA voice capacity, i.e. HSUPA control channel overhead. Finally, this work introduces techniques not only to circumvent the current limitations of HSUPA but also to enhance its capabilities to support real-time services. In particular, a gated mode, named VoIP mode is examined.