Mobile telephony system intended for indoor and outdoor subscriber use

Claim 1

A mobile telephony system with a plurality of cells intended for indoor and outdoor subscriber use, and comprising an external part-system for outdoor use which includes external base stations of relatively high signal strength and connected directly to a mobile switching centre, and an internal part-system for indoor use and having internal base stations of relatively low signal strength which are connected to the mobile switching centre, wherein the two part-systems have traffic channels essentially for call transmissions and control channels essentially for assignment and change of the traffic channels; at least one of the traffic channels of the internal part-system has the same frequency as the traffic channels assigned to the base station of the external part-system cell in which the internal part-system is located; the inner part-system has adaptive channel assignment; an internal identification word which is unique to the internal part-system is transmitted from the internal base stations on the control channels in the internal part-system; an outer identification word which is unique to the external part-system is transmitted from the external base stations on the control channels in the external part-system; a mobile station detects a signal quality for the control channel of the internal part-system on which the internal identification word is transmitted; the mobile station transmits an internal identification signal to the internal base stations when the detected signal quality exceeds a desired quality measurement; and wherein the mobile station transmits an external identification signal to the external base stations when the detected signal quality is beneath the desired quality measurement.