Multiplex communications – Duplex – Convertible to half duplex
Patent
1995-09-12
1997-02-04
Olms, Douglas W.
Multiplex communications
Duplex
Convertible to half duplex
370350, 370431, H04L 516
Patent
active
056006365
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method for digital semi-duplex transmission between subscriber stations and a base station in a radio system.
BACKGROUND OF THE INVENTION
The invention is concerned with semi-duplex FDMA mobile radio system comprising mobile exchanges, base stations and mobile radios and having a cellular configuration, each cell having one or more radio channels.
In semi-duplex FDMA mobile radio systems, it is usually impossible to interrupt a mobile radio during its transmitting permission and transmit signalling to the mobile radio as the mobile radio is not able to receive signalling during its transmission. This problem is solved in the same applicant's parallel application Method for digital semi-duplex transmission (FI 934230) by interrupting the transmission of the mobile radio at predetermined intervals and listening to reverse signalling transmitted by the base station. Reversing the direction of the radio parts of a semi-duplex mobile radio from transmission to reception before receiving and again from reception to transmission after signalling requires certain guard periods on both sides of the reverse signalling. Due to the regular frame structure of information to be transmitted, such guard periods are often used repeatedly, even though none of the transceivers is transmitting speech or data, that is, even when no reverse information is being transmitted. In practice, this means that the frame structure all the time contains idle time.
DISCLOSURE OF THE INVENTION
The object of the present invention is to dispense with the problem caused by the fact that unlike full-duplex FDMA and TDMA mobile radio systems, a semi-duplex FDMA mobile radio system does not allow a mobile radio to receive during its transmission. A radio station, such as a base station, having the permission to receive is not able to transmit any kind of information to a subscriber station having the permission to transmit. A base station having the permission to receive cannot interrupt the transmission of a subscriber station having the permission to transmit.
An object of the invention is to solve the above-described problem, i.e. how to interrupt the transmission of a semi-duplex mobile radio having the transmitting permission and to transmit reverse signalling to this subscriber station without interrupting or interfering with the speech or data transmission of the subscriber station having the transmitting permission. Another object of the invention is to solve the problem associated with the wasting of the signalling capacity of the base station, which is caused by the guard periods required for solving the above-described problem, as the subscriber station having the transmitting permission is not able to transmit or receive during the guard periods.
This new method for digital semi-duplex transmission between transceivers is achieved by a method according to the invention, which is characterized in that it comprises the following steps: a selected number of speech or data blocks are transmitted during a time period shorter than the original total duration of the speech or data blocks from a subscriber station having the permission to transmit to a base station having the permission to receive; the base station having the receiving permission utilizes the original total duration of the blocks reduced by the actual transmission period of the blocks and by a first and a second guard period for transmitting reverse information and time synchronization information to the subscriber station having the transmitting permission; and the base station having the receiving permission transmits information during at least one of said guard periods to at least one subscriber station which does not have the transmitting permission.
The idea of the invention can be presented in the following way. As speech or data information to be transmitted consists of blocks of fixed duration, a selected number of successive blocks are gathered up and transmitted over the radio path during a period of time sh
REFERENCES:
patent: 4630257 (1986-12-01), White
patent: 4949335 (1990-08-01), Moore
patent: 5025442 (1991-06-01), Lynk et al.
patent: 5095540 (1992-03-01), Reed
patent: 5249304 (1993-09-01), Mulford
patent: 5319635 (1994-06-01), Reed et al.
Finnish Patent Application No. 934230, of Makelainen, filed Sep. 27, 1993.
Heiskari Mika
Lehmusto Mika
Makelainen Kimmo
Nokia Telecommunications Oy
Olms Douglas W.
Patel Ajit
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