U.S. Philips Corporation

Detemobil Deutsche Telekom Mobilnet Gmbh

Alfons Eizenhofer

Christoph Grauel

Reinhold Mertens

Michael Sollner

Georg Von Harten

Process and apparatus for locating mobile stations

Cellular mobile radio systems provide full-duplex communication between base stations and mobile stations and with the fixed public service network. Also known are trunked mobile radio systems wherein a group of mobile users can exchange information with each other in the half-duplex mode over a common channel, only one user transmitting to the others at any time. It has been proposed to provide mobile radio sets which are especially adapted to be switched for use in either of such systems. The present invention avoids the need for specific adaptation of a mobile radio set for that purpose. Instead, it enables a cellular mobile radio system to be selectively converted into a trunked mobile radio system by providing for the base station to couple an up-link radio channel of any mobile user to down-link radio channels of a selected group of mobile users. One or more such user groups can be formed, only one radio channel being used for each group.

Cellular radio communication system which is selectively convertible

In a communication system having at least a central arrangement and a plurality of mutually independent subscriber stations, a subscriber station, after transmitting a request for access, expects an authorization for access to be granted by the central arrangement. For this purpose it is proposed that the subscriber station repects its request for access once it has established that a further subscriber station, which transmitted its request for access at a later instant, recesses and authorization for access.

Communication system

A cellular digital radio transmission system wherein messages are transmitted from a base station to a plurality of mobile stations assigned to it by time-division multiplexing of time slots in respective TDM time frames, each mobile station being assigned by the base station to a respective time slot constituting a channel for receiving and transmitting information. In order to fully utilize the channel capacity of the TDM time frames for users having different bandwidth requirements the base station divides each TDM time frame into time slots of different durations, whereby a mobile station can be assigned by the base station to a time slot of a duration corresponding to the bandwidth required by such mobile station.

Digital radio transmission system with variable duration of the time

Method of digital radio transmission between a base station and a plurality of mobile stations. A time division multiplexed signal frame is generated, including a plurality of time slots which repeat each frame interval. A beginning number of the time slots form a signalling channel with the remaining following time slots forming a plurality of channels which receive data to be sent. The signalling channels include a common organizational connection for each channel of the frame. Additionally, one of the remaining plurality of channels includes an organizational channel for identifying a larger number of channels than those included in the individual frame. The technique permits a combination of time division multiplexing, spectral multiplexing and carrier frequency multiplexing.

Digital radio transmission system with a connection-accompanying

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.

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Altdorf, Germany

Alfons Eizenhofer