Discovery signalling in a device-to-device communication system

摘要

A first device receives a device-to-device D2D discovery signal which indicates that a second device which sent it does not have a cellular connection and/or is requesting relay to a network broader than a D2D network. In response, the first device engages in a search to find a cellular access node and reports its search results via D2D signalling. In non-limiting embodiments the indication can be explicit or may be implicit in the signal coding; the discovery signals of all devices are sent in periodic discovery signal intervals (204A-F) and any indication in a first discovery signal interval (204C) that a device needs a cellular connection triggers a common search by all the D2D devices in a second common search interval (208D) which is previous to the next discovery signal interval (204D) after the first (204C). The search results are reported in that next discovery signal interval (204D).