Abstract: A method is described of handing over calls between two relay stations, respectively a current relay station and a target relay station in the same cell of a digital cellular mobile radio system, the cell being associated with a base transceiver station comprising a plurality of relay stations including the current and target relay stations and geographically distributed within the cell. Each relay station comprises at least one antenna connected to at least one transmit/receive device. Each relay station has a plurality of traffic channels and a plurality of associated signaling channels. A call being set up for a mobile station is allocated, from the channels of the current relay station, at least one current traffic channel and at least one current associated signaling channel. The plurality of relay stations shares at least one particular traffic channel, constituting a shared traffic channel, which is reserved at least partly for handover.

Abstract: A system for synchronizing base transceiver stations includes a reference base transceiver station and a subordinate base transceiver station. Each base transceiver station has a clocks with the same frequency but any relative phase, and a timing reference. The reference base transceiver station imposes its own timing reference on each subordinate base transceiver station to compensate the phase difference between the two stations. The timing reference is imposed by having a mobile station listen to the reference base transceiver station and the subordinate base transceiver station, deducing a time shift D1 between the two base transceiver stations from the perspective of the mobile, determining a propagation time difference D2 between the mobile and the reference base transceiver station and the subordinate base transceiver station upon the occurrence of a handover that involves the reference base transceiver station.

Abstract: In a TDMA type cellular mobile radio system frequencies are shared between cells of the same re-use pattern and frequency hopping is used so that the frequency used at any time in one of the cells of a re-use pattern is different from those used at the same time in the other cells of that pattern. A base transceiver station of this system commands the sending of one of the frequencies shared in this way during a part of the time division multiple access frame and commands the stopping of all sending during the other part of the frame.

Abstract: In a combined time-division multiple access and frequency-division multiple access multilayer cellular mobile radio network comprising macrocells and microcells, each macrocell being associated with at least one control frequency and at least one traffic frequency and each microcell being associated with at least one control frequency, a method of optimizing frequency use when adding any microcell base station defining a given microcell that is part of a coverage area of a given macrocell includes the step of allocating to said microcell a control frequency identical to a traffic frequency used in a macrocell immediately adjacent said given macrocell.

Abstract: A cell level change control device for cellular mobile radio networks with more than one level of cells includes means for comparing the value of a parameter representative of the speed of a mobile station with a threshold in order to decide if it is necessary to command a cell level change when the mobile station is served by a lower level cell contained in a higher level cell or when a mobile station is served by a higher level cell and it is determined that the lower level cell contained in that higher level cell constitutes the best cell. The device determines the load of the higher level cell and varies the threshold in accordance with the load.