A method and system for a wireless communication system for a moving vehicle having a plurality of carriages is disclosed. The system comprises at least one internal network onboard said vehicle and at least one router, connected to the internal network and to at least one exterior mobile network, wherein the internal network comprises a plurality of network switches, connected together by cables, wherein the network switches are Power over Ethernet (PoE) switches. In at least one of the network switches it is determined if an input power received from a power supply is below a minimum power level. In case it has been determined that the input power level is below the minimum power level, power is received as Power over Ethernet from at least one of the other network switches, and the switch continues at least part of the network switch operation also when powered by the at least one other network switch.