Abstract: In a communications system with a plurality of subscriber stations independent from each other, where each subscriber station can access according to a multiple access method a joint duplex transmission channel, the probability becomes very large for simultaneous attempts to get access and thereby the probability of signal destruction becomes particularly large. In order to avoid a blockage of the service channel each subscriber station occupies the duplex transmission channel with a short access signal for initiating a transmission starting with the subscriber station. The subscriber station characterized by the position in time and/or the information contents of the signalling short designation call is thereupon invited by the central base station to provide complete identification information.

Abstract: In a communications system with a plurality of subscriber stations independent of each other, where each subscriber station can access a joint duplex transmission channel according to a multiple access method, the probability of simultaneous attempts to get access becomes very image, and thereby the probability of signal destruction is particularly increased. In order to avoid a blockage of the service channel each subscriber station occupies the duplex transmission channel with a short access signal for initiating a transmission starting from the subscriber station. The subscriber station characterized by the position in time and/or the information contents of the short access signal is thereupon invited by the central base station to emit an access signal to join practical access to the communication exchange.

Abstract: A method and apparatus for use in a digital radio transmission system comprising stationary radio stations arranged in a cellular network and to which are assigned a plurality of mobile radio stations. Transmission of digital messages from a stationary radio station to the mobile radio stations assigned to it is effected by wide-band code division multiplex modulation, and transmission of digital messages from such mobile radio stations to the stationary radio station is effected by narrow-band frequency multiplex modulation. This reduces bandwidth requirements and improves the signal-to-noise ratio for each direction of transmission.

Abstract: A digital multiplex radio transmission system wherein transmission channels between a fixed radio station and a plurality of mobile radio stations may be established by code division multiplex or frequency division multiplex, individual message channels being separated by means of different distributions of the data symbols transmitted therein. In order to synchronize the fixed station transmitter with the mobile station receivers, respective synchronizing symbols are inserted between the successive data symbols transmitted in any channel. The synchronizing symbols used in all channels are the same, and are spaced at the same time intervals in each channel. Consequently, they are received with significantly higher energy than the data symbols, permitting the multi-path profile to be measured and providing reliable synchronization.

Abstract: A cellular radio system in which the mobile radio stations in the zone of any base radio station assign themselves to the control channels allocated to that base station so as to evenly spread the volume of traffic over such control channels. The base station transmits on each control channel a channel group code signifying the range of group code numbers allocated to that particular control channel. Each mobile station stores its identifying group code number, scans the group code numbers of all control channels, and assigns itself to the control channel having a channel group code which includes its group code number. The spread of traffic over the various control channels can be changed by the base radio station simply by changing the channel group codes of the various control channels, without addressing specific commands to the mobile radio station.

Abstract: A system and process is described for spreading the volume of traffic over different control channels of a cellular radio transmission system. A base station having at least two control channels subdivides the number of mobile radio stations in a cellular area of the base station into groups, of a variable number of groups. The base stations transmit the number of groups and a group code on each control channel. The mobile stations receiving the transmitted information detect the number of groups and group code of each channel. The mobile radio stations will combine the number of groups and the received group code with the stored group number. The result of this combination determines the channel over which the mobile station control is to be assigned.