Within the AbaCUS approach a caller is flexible to use the voice-service provider of his choice, such as VoIP, MNOs, and FNOs, in order to place a call. The caller can reach the callee by dialing directly his MSISDN. In this case the host MNO will collect the call-termination rate. However, a competitive MNO may
generate a virtual MSISDN and allow to the callee to register in his network. Thus, the caller may dial the virtual MSISDN and reach the callee. In that case the guest MNO will profit from the termination rate. Multiple MNOs can participate in an auction, where the caller will request to place a call, reach a callee in a specific location, and demands a certain QoS-guarantee for the duration of this call. This demand is expressed by QoS Classes (QoS-C), which contain parameters related to the sound quality and the network-access waiting-time. MNOs bidding in the auction will reply to this request by proposing their charging demand. The charging demand is expressed by the Termination Rate Classes (TeR-Cs), which contain a potential start-up cost and the desired charging rate. Finally, on a referee role during the AbaCUS auction is the Auction Authority (Au
2), which receives call requests from callers and from MNOs the
selected TeR-C preference per QoS-C.