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In 3GPP standard, LTE networks are currently specified by considering Mobile VoIP combined with IMS for session control to ensure voice calls support. So, Mobile VoIP over LTE with IMS can be considered as a target for voice support migration from the current support in Circuit Switched (CS) Domain. Because Mobile VoIP services could potentially be supported over HSPA in the coming years and LTE coverage will probably not correspond to HSPA networks coverage before several years, it is necessary to assess if there is a potential interest and way to anticipate Mobile VoIP services launch with, first, a support over HSPA/HSPA+. Thus, on the first hand, the aim of this paper is to analyse the architecture evolutions of current mobile networks for voice support as Mobile VoIP over HSPA/HSPA+, CS over HSPA, the corresponding drivers but also technical requirements, limitations and maturity on the different network parts. On the second hand, the paper aims at analysing the economic appropriateness of supporting voice services over those architecture evolutions. For this, two different analyses have been carried out in parallel. The first one addresses the economic opportunity for a 3G mobile network operator, in terms of expenditure savings, to deploy VoIP over HSPA and/or CS over HSPA. The second analysis assesses the possible costs for VoIP services, in the perspective of tariff setting. In this analysis, "fair" allocation mode based on the traffic of the different services is favoured. Finally, this paper synthesizes the different pros and cons of each solution in terms of QoS, capacity performance, development maturity and techno-economic analysis. Depending on operator's strategy for migration to VoIP over LTE, the choice of launching one solution prior to another will have to take into account all these topics.