System for communication between a first terminal and a second terminal, comprising: a first gateway configured for connection to the first terminal (A i) on the one hand and to a set of at least two parallel wireless networks (N k) on the other hand, a first of said networks (N 1) including a 5G Radio Access and a second of said networks (N 2) being a non-5G network, and a second gateway configured for connection to said set of networks (N k) on the one hand and the second terminal (B j) on the other hand, which second gateway comprises a second 5G Core Network having a second Authentication Server Function, AUSF,, a second Unified Data Management, UDM,, a second Access and Mobility Management Function, AMF,, a second Network Exposure Function, NEF,, a second Policy Control Function, PCF,, and a second Session Management Function, SMF,, characterized in that the first gateway is configured for connection to a first of said networks (N 1) which is a 5G network comprised of a first 5G Core Network having a first Authentication Server Function, AUSF,, a first Unified Data Management, UDM,, a first Access and Mobility Management Function, AMF,, a first Network Exposure Function, NEF,, a first Policy Control Function, PCF,, and a first Session Management Function, SMF,, and of said 5G Radio Access, wherein the first gateway comprises a first 5G User Equipment (17 - 19) having a first modem (20 1) configured for connection to the first 5G Core Network either, via a modem of a second 5G User Equipment (6"), over said second 5G User Equipment (6") connected to the 5G Radio Access or via a first Non-3GPP Interworking Function, N3IWF, gateway of the first 5G Core Network, and having a second modem (20 2) configured for connection to the second network (N 2), and hosting a first User Plane Function, UPF, which controls the use of said modems (20 k), wherein the second gateway comprises a set of at least two N3IWF gateways (24 k) for connection to said set of at least two networks (N k) and hosting a second UPF which controls the use of said at least two N3IWF gateways (24 k), and in that the first and second UPF (21, 22) are configured to perform a 5G Access Traffic, Steering, Switching and Splitting, ATSSS, function selecting one or more of said networks (N k) for communication between the first and the second terminal (A i, B j). a first gateway configured for connection to the first terminal (A i) on the one hand and to a set of at least two parallel wireless networks (N k) on the other hand, a first of said networks (N 1) including a 5G Radio Access and a second of said networks (N 2) being a non-5G network, and a second gateway configured for connection to said set of networks (N k) on the one hand and the second terminal (B j) on the other hand, which second gateway comprises a second 5G Core Network having a second Authentication Server Function, AUSF,, a second Unified Data Management, UDM,, a second Access and Mobility Management Function, AMF,, a second Network Exposure Function, NEF,, a second Policy Control Function, PCF,, and a second Session Management Function, SMF,, characterized in that the first gateway is configured for connection to a first of said networks (N 1) which is a 5G network comprised of a first 5G Core Network having a first Authentication Server Function, AUSF,, a first Unified Data Management, UDM,, a first Access and Mobility Management Function, AMF,, a first Network Exposure Function, NEF,, a first Policy Control Function, PCF,, and a first Session Management Function, SMF,, and of said 5G Radio Access, wherein the first gateway comprises a first 5G User Equipment (17 - 19) having a first modem (20 1) configured for connection to the first 5G Core Network either, via a modem of a second 5G User Equipment (6"), over said second 5G User Equipment (6") connected to the 5G Radio Access or via a first Non-3GPP Interworking Function, N3IWF, gateway of the first 5G Core Network, and having a second modem (20 2) configured for connection to the second network (N 2), and hosting a first User Plane Function, UPF, which controls the use of said modems (20 k), wherein the second gateway comprises a set of at least two N3IWF gateways (24 k) for connection to said set of at least two networks (N k) and hosting a second UPF which controls the use of said at least two N3IWF gateways (24 k), and in that the first and second UPF (21, 22) are configured to perform a 5G Access Traffic, Steering, Switching and Splitting, ATSSS, function selecting one or more of said networks (N k) for communication between the first and the second terminal (A i, B j).