Abstract: The present invention relates to a method and radio unit for assigning transmission turns to a radio unit (RU2) wishing to operate on a direct mode channel (f1). To assign the transmission turns in a controlled manner, said radio unit (RU2) monitors the quality of the traffic (101) conducted on the direct mode channel, and if the quality of the traffic (101) falls below a predetermined value, said radio unit (RU2) starts to transmit its transmission (120) on said direct mode channel.

Abstract: For establishing an expanded group call in a mobile communication system which has group call groups formed by a plurality of mobile stations, a network infrastructure which has at least one exchange, a plurality of base stations and telecommunication connections between them, and a group call database for maintaining data concerning group calls, an expanded group call set-up facility concerning a first group call group is activated in the group call database, the facility expanding the group call o concern at least one other group call group.

Abstract: The present invention relates to a method and radio system for controlling a subscriber station (MS1) operating on a direct mode channel in a radio system, said radio system comprising a radio network (SwMi) with at least one base station (BS) and subscriber stations (MS1), and further, at least one repeater station (RS), which forwards traffic between said at least one base station (BS) and the subscriber stations (MS1) operating on the direct mode channel. To control the subscriber stations operating on the direct mode channel, information on the identifiers of subscriber stations operating on the direct mode channel in the coverage area of the repeater station (RS) is maintained in said repeater station (RS).

Abstract: A method for controlling a radio unit in a radio system which has at least a first radio unit and a second radio unit in which at least one of the radio units communicates on a direct mode channel. In order either to stop the entire operation of the second radio unit or to stop it from operating on the direct mode channel, the first radio unit transmits a direct mode channel leaving request message to the second radio unit on the direct mode channel, this message commanding the second radio unit to cease from communicating on one or more direct mode channels.

Abstract: The invention relates to a method of establishing a call in a mobile communications system and to a mobile communication system comprising at least one base station, mobile stations communicating with the mobile communication system and marked at least with system addresses, mobile stations communicating on a direct mode channel and marked with direct mode addresses, and at least one repeater station which transmits traffic between said at least one base station and the mobile stations, communicating on the direct mode channel. To provide flexible call setup, the repeater station comprises a conversion table for converting between said system addresses of the mobile stations and said direct mode addresses.

Abstract: A group call method, a system controller and a subscriber station in a radio system comprising a plurality of base stations and subscriber stations. In order for a subscriber station to be able to select the group call in which it will participate from among a plurality of group calls while participating in a first group call, group call data are transmitted to the subscriber station during the first group call, by means of which data the subscriber station can engage in another ongoing group call, whereby the subscriber station continues to participate in the first group call or, if it desires, selects another group call from among the group calls whose group call data have been transmitted to the subscriber station and whose group call identifiers are simultaneously displayed on the display of the subscriber station.

Abstract: A method for activating ambiance listening in which a first, mobile radio unit transmits ambient sounds and voice to a second radio unit over a radio path. To check that the second radio unit has listening authority, the second radio unit commands the first radio unit to transmit ambient sounds and voice to the second radio unit. In response, the first radio unit checks the listening authority of the second radio unit, and, if the second radio unit has the listening authority, the first radio unit starts transmitting ambient sounds and voice to the second radio unit.

Abstract: A method for allocating control channels in a radio system having base stations and subscriber stations communicating with respective ones of the base stations on control and traffic channels. To make the control channel operation more efficient and to avoid interference, traffic channels are allocated for control channel use so as to distribute the control channel operation between a greater number of channels, the channels allocated for control channel use being indicated to the subscriber stations and control channel operation is performed on the control channels allocated in a distributed manner.

Abstract: A method for controlling a subscriber station communication on a direct mode channel in a radio system, in which at least one base station is communicating via channels, and subscriber stations. To guide a subscriber station to a desired channel at a desired moment, the radio system sends to the sub-scriber station on a direct mode channel a communication information message determining for the subscriber station the moments and the identifiers of the channels at and on which the radio system communicates with the subscriber station on the direct mode channel. The subscriber station stores the information contained in the received communication information message in its memory. The subscriber station communicating on the direct mode channel moves at the moment determined by the communication information message to the channel to be used and communicates with the radio system on that channel.

Abstract: A method for digital semi-duplex transmission. To allow transmission of information to subscribers during the transmitting permission of one of the subscribers, a selected number (N-1) of blocks are transmitted during a time period shorter than the original total duration (t) of the blocks from a subscriber (MS A) having the permission to transmit to a base station (BS) having the permission to receive; the base station (BS) having the receiving permission utilizes the original total duration (t) of the blocks reduced by the actual transmission period of the blocks and by a first and a second guard period (301, 302) for transmitting reverse information (203) and time synchronization information (202) to the subscriber having the transmitting permission; and the base station (BS) having the receiving permission transmits information during at least one of said guard periods (301, 302) to at least one subscriber (MS B) having no transmitting permission. (FIG.