Telecommunications – Transmitter and receiver at separate stations
Patent
1994-11-30
1996-12-31
Faile, Andrew
Telecommunications
Transmitter and receiver at separate stations
455 541, 455 341, H04Q 700
Patent
active
055904009
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method of searching for a signalling channel in a radio system comprising a mobile exchange, base stations connected therewith, subscriber stations that are connected with the base stations and communicate with the radio system via the channels of the base station, i.e. via traffic channels and non-dedicated control channels; the method comprising the following steps: a first subscriber station registered in a first base station listens to a signalling channel of the first base station, and the radio system allocates said signalling channel to a second subscriber station for use as a traffic channel since the other channels of the first base station are busy.
BACKGROUND OF THE INVENTION
The invention concerns cellular radio systems, such as mobile phone systems and PMR systems (PMR=private mobile radio), i.e. cellular radio networks in which the area covered by the network is divided into radio cells. The subscribers roaming in the area of these radio cells communicate with the system when they are within the coverage area of the base stations located in the radio cells.
In a system like this, a subscriber station, such as a mobile phones, located in a radio cell listens or tunes the receiver unit of its radio to the frequency of a signalling channel of a base station located in the radio cell. A signalling channel is used for exchanging messages concerning the connection establishment between a subscriber station and a base station. On the basis of connection establishment, the system controller of the cellular radio network assigns the subscriber stations to actual traffic channels, in which the actual transfer of information, i.e. speech or data, takes place. Traffic between a base station and subscriber stations takes place on radio channels that are implemented such that downlink traffic (from a base station to a subscriber station) takes place at a first frequency, and uplink traffic (from a subscriber station to a base station), at a second frequency. In FDMA systems (FDMA=Frequency Division Multiplexing Access) a channel thus means a pair of channels used for one conversation. In a TDMA system (TDMA=Time Division Multiplexing Access) a channel means a carrier and its time slot.
It is typical of channels provided between base stations and subscriber stations that there is a limited number of channels available since there are few radio frequencies and/or time slots. It is thus typical of cellular radio systems that one--possibly the only--signalling channel of a base station can be converted to a traffic channel, e.g. a speech or data channel, when a traffic channel is needed for a call between a subscriber station and a base station and the actual traffic channels of the base station are busy. Typically, this kind of procedure is followed in areas where the traffic and subscriber density is low and where the number of radio channels is small; the use of a signalling channel as a traffic channel significantly improves the transmission capacity of the system. When a signalling channel that can be converted to a traffic channel (i.e. a non-dedicated control channel) is used as a traffic channel, signalling messages cannot be transmitted on said channel unless the channel has an inband signalling channel, such as an associated signalling channel, whereby it is possible to transmit short signalling messages in the middle of speech or data to the parties listening to the channel (base station and subscriber station). However, it is not possible to set up new calls on the associated signalling channel nor to transmit data messages on it since the transmission capacity of said channel is very limited. Typically all the channels of a base station can function as signalling channels or traffic channels when necessary and that if all the channels of the base station function as traffic channels at the same time, any channel that is released from use as a traffic channel can be converted to a new signalling channel for traffic between the base station and t
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Faile Andrew
Nguyen Lee
Nokia Telecommunications Oy
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