Method of establishing a voice over internet protocol, VoIP, call between a calling user equipment, UE, and a called UE

A method of establishing a Voice over Internet Protocol (VoIP) call between a calling User Equipment (UE) and a called UE, wherein said calling UE is served by a packet switched (PS) core network via a radio access network (PS-RAN) and wherein a bearer is to be established between said calling UE and a gateway node in said PS core network, over said RAN, for obtaining access to an Internet Protocol (IP) multimedia subsystem (IMS) network, wherein said method comprises:

• establishing, by said gateway node, said bearer between said calling UE and said gateway node;
• determining, by said gateway node, that said bearer establishment has failed due to a temporary failure;
• retrying to establish, by said gateway node, said bearer between said calling UE and said gateway node.

A method for establishing a Voice over Internet Protocol (VoIP) call between a calling User Equipment (UE) and a called UE, wherein said calling UE is served by a packet switched (PS) core network via a radio access network (RAN) and wherein a bearer is to be established between said calling UE and a gateway node in said PS core network, over said RAN, for obtaining access to an Internet Protocol (IP) multimedia subsystem (IMS) network, wherein said method comprises:

• transmitting, by said calling UE, a request message for requesting establishment of said VoIP call;
• receiving, by said calling UE, a service unavailable message indicating that said establishment of said bearer has failed and comprising an indication that said calling UE should retry said establishment of said VoIP call;
• re-transmitting, by said calling UE, said request message for requesting establishment of said VoIP call of requesting, by said calling UE, re-registration in said IMS network.

An Internet Protocol (IP) Multimedia Subsystem (IMS) Call Session Control Function (CSCF) node for supporting establishment of a Voice over Internet Protocol (VoIP) call between a calling User Equipment (UE) and a called UE, wherein said calling UE is served by a packet switched (PS) core network via a radio access network (RAN) and wherein a bearer is to be established between said calling UE and a gateway node in said PS core network, over said RAN, for obtaining access to said IMS network, wherein the IMS CSCF node comprises:

• receiver circuitry configured to receive a notification message thereby notifying said IMS node that said VoIP call establishment is in progress;
• and
• processing circuitry configured to enable retry to establish said bearer between said calling UE and said gateway node, over said RAN, in case said establishment of said bearer has failed due to a temporary failure.