Multiplex communications – Wide area network – Packet switching
Patent
1993-12-10
1995-05-23
Olms, Douglas W.
Multiplex communications
Wide area network
Packet switching
H04J 316
Patent
active
054187877
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a signalling method for a radio system, comprising a plurality of fixed radio stations, and at least one remote radio station, the system comprising at least one frequency channel serving as a time-shared control channel common to a plurality of fixed radio stations for transmitting messages.
BACKGROUND OF THE INVENTION
In certain mobile radio systems, a plurality of fixed radio stations or base stations share a common radio channel called a time-shared control channel, and transmit sequentially on this channel. This type of system is used when there is a lack of radio channels, and the traffic density is low. In such mobile radio systems, each mobile radio responds only to the control signal burst transmitted on the time-shared control channel by the base station to which the mobile radio is currently registered, and signals back to the system (to the exchange) only via this particular base station during the reception of the control signal burst. However, if the control signal of the base station is no longer of sufficient level when received at the mobile radio, the mobile radio selects a new base station on the basis of the control signal levels received from the other base stations, and registers to the selected base station. In this type of system, the utilization of a time-shared control channel unavoidably leads to a situation where the time required to set up calls between the mobile radios and the network is statistically longer than in a system in which each base station has a dedicated control channel (which is not time-shared). This is because the base station may have more messages to be transmitted and received than what it is capable of handling during its transmission time slots on the time-shared control channel.
SUMMARY OF THE INVENTION
The object of the invention is to provide a signalling method which alleviates the above-mentioned problem in a radio system utilizing a time-shared control channel.
This is achieved by a signalling method for a radio system described in the foregoing Background section, which method according to the invention is characterized in that the fixed radio station having queuing messages transmits the messages in the transmission time slot of the fixed radio station on the time-shared control channel in the following order: a) the remaining messages of unfinished call set-up transactions initiated in the preceding transmission time slot of the fixed radio station, b) messages critical to the call set-up transaction and requiring an acknowledgement from the remote station, and c) messages requiring no acknowledgement from the remote station.
The basic idea of the invention is to select the priority of the signalling transactions effected during the transmission time slot of the fixed radio station on the time-shared control channel so that any unfinished call set-up transactions initiated in the previous transmission time slot are always completed first at the beginning of the transmission time slot. Data messages and announce messages associated with the channel management are transmitted at the end of the transmission time slot if the transmission time slot has not yet expired. The priority method according to the invention allows the call set-up time to be minimized within the limits of the assigned time slot even at high traffic load.
The signalling method according to the invention is particularly advantageous in a system where the length of a transmission time slot of a base station can be varied in accordance with the amount of signalling passing through the base station. The transmission time slot may also be extended due to repeated transmission caused by a transfer error and when an (immediate) acknowledgement to a transmitted message is required from a mobile radio. The decision on the length of the transmission time slot is preferably made during the respective time slot. The length of the transmission time slot is controlled by a time slot extension algorithm having a probability function which
REFERENCES:
patent: 5020132 (1991-05-01), Nazarenk et al.
patent: 5229995 (1993-07-01), Strawczynski et al.
patent: 5239545 (1993-08-01), Buchholz
Harjula Arto
Sarja Jorma
Tiuraniemi Riitta
Nokia Telecommunications Oy
Olms Douglas W.
Patel Ajit
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