Method for controlling a subscriber station in a mobile radio sy

Details Method for controlling a subscriber station in a mobile radio sy Method for controlling a subscriber station in a mobile radio sy

1996-04-30

1998-08-04

Vo, Nguyen

Telecommunications

Carrier wave repeater or relay system

Portable or mobile repeater

455422, 455450, 455455, 455509, H04B 715

Patent

active

057909385

DESCRIPTION:

BRIEF SUMMARY
This application claims benefit of international application PCT/FI94/00492, filed Nov. 1, 1994.


FIELD OF THE INVENTION

The present invention relates to a method for controlling a subscriber station operating on a direct mode channel in a mobile radio system, this mobile radio system comprising a radio network with at least one base station and subscriber stations, and at least one subscriber database, and further, at least one repeater station, which forwards traffic between one at least one base station and the subscriber stations operating on a direct mode channel. In the method, a subscriber station is registered in a radio network via a base station; the subscriber station transmits a detachment message to the base station, and indicates that it is switching to operate on a direct mode channel.


BACKGROUND OF THE INVENTION

The invention relates to the field of mobile phone systems. A subscriber in a mobile phone system, i.e. a subscriber station, for instance a mobile phone or some other means of communication, may be registered in a radio network or system, whereby it is registered in the radio network via system and traffic channels maintained by the base stations of the radio network.
In addition to the system channels in mobile phone systems, so-called direct mode channels can also be used in connection with a mobile radio system, i.e. direct mode operation is applied. Subscriber stations using direct mode operation do not communicate directly with the radio network or its base stations. Direct mode channels are frequencies at which mobile phones or other means of communication are able to communicate directly with each other without the system.
Direct mode channels are typically used in situations where, for instance, a group of portable mobile phones are communicating with each other at such a long distance from the base station that system channels cannot be used.
Another important way of using direct mode channels is to increase the capacity when the traffic in the system increases fast in some part of the service area of the system, for instance in some point-like part.
A direct mode channel is referred to with terms direct or simplex channel, or a simplex connection. A direct mode channel is a channel which is typically not at all used by the system. It may be, for instance, a channel of the breadth of the channels of the system, for instance 12.5 kHz or 25 kHz. Among the mobile phones operating on a direct mode channel, the transmitting station has tuned its transmitter to the channel and transmits speech or data information. The other mobile phones set to direct mode operation have tuned their receivers to the same channel, whereby they are able to directly hear the transmission.
One form of a direct mode channel is a direct mode channel equipped with a repeater, which direct mode channel comprises a separate repeater station in addition to the subscriber stations, this repeater station forwarding traffic between the subscriber stations using the direct mode channel. In this case, the traffic on the direct mode channel takes place on the semiduplex principle.
Operation on a direct mode channel may take place on the analog or digital modulation principle. A mobile phone transmitting on the channel may also transmit signalling information, such as information on rights of use and priorities or on the group operating on the channel. On the direct mode channel, an encryption may be carried out or plain speech can be transmitted.
Subscriber stations using direct mode operation communicate with other subscriber stations on a direct mode channel without being in direct contact with the base stations of the radio network. The subscriber stations using direct mode operation can however communicate with the radio network via repeater stations. A repeater station is a piece of equipment comprising two radio apparatuses connected to each other. The repeater station transmits the information messages transmitted on the direct mode channel to desired network elements, for instance to the base stati

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