Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1997-11-14
2001-07-17
Chin, Wellington (Department: 2664)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C375S222000, C455S069000
Reexamination Certificate
active
06262994
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to and is based on an arrangement for optimizing data transmission in a radio channel.
A prior art arrangement is known in the area of amateur radio (Clover process from CQDL 10/94, pp. 709-714). Given this Clover process, the number of occurring transmission errors is determined at the reception side using a known redundancy testing process CRC (Cyclic Redundancy Check). This information is transmitted to the remote station and allows the system to adapt to the radio channel by choosing the type of modulation. In addition, phase deviations and SNR (Signal-to-Noise Ratio) in the received signal are measured during existing connection at both stations. The transmitter power can be reduced to the necessary level for an error-free transmission. Standard amateure radio transmitters do not have the possibility of automatic power control of the sender, so that this power reduction has to be done manually during the Clover process.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an arrangement that is suitable for the more demanding commercial of application of data transmission.
In general terms the present invention is an arrangement for optimizing of data transmission via a bidirectional channel. Modulation types are selectable at a transmitter side of the channel. A code rate of a forward error correction and a power of a transmitter is also settable at the transmitter side. Devices at a reception side of the channel determine an error rate. A device at the transmitter side varies at least one of a size of data packets, type of modulation, code rate, and power of the transmitter as a function of the error rate that is transmitted back from the reception side, such that a predetermined error rate is achieved on the reception side.
Advantageous developments of the present invention are as follows.
When the error rate exceeds a predetermined value, the packet size is reduced and/or a switch is made to a less significant type of modulation and/or to a lower code rate and/or to a higher power automatically, at the transmitter side.
When the error rate is less than a predetermined value, the packet size is increased and/or a switch is made to a more significant type of modulation and/or to a higher code rate and/or to a lower power automatically, at the transmitter side.
In the arrangement of the present invention, the selection is made from four different setting variables at the transmitter side, each of which has influence on the quality of the data transmission. The selection is respectively made in dependence on the same measured variable at the reception side, namely on the error rate determined by the CRC Process. Given the inventive arrangement, only one measured variable has to be transmitted at the reception side back to the remote station. A simple overall structure thereby derives and miscontrols are avoided to the farthest possible extent. The four setting variables are size of the data packets comprising a plurality of frames, various more significant modulation processes, code rate of the forward error correction FEC, and output power of the transmitter.
Deterioration of the data transmission and thus a change in error rate determines which of these setting variables, proceeding from the currently selected setting, can be changed to a variable that improves the data transmission. The sequence of changing the setting variables is dependent on the respective application and it is determined in the control circuit of the transmitter side. The respective change of the setting variables ensues at the transmitter side completely automatically solely in dependence on the retransmitted error rate.
REFERENCES:
patent: 5214687 (1993-05-01), Kansakoski et al.
patent: 5450438 (1995-09-01), Landry et al.
patent: 5524122 (1996-06-01), Lepitre et al.
patent: 5550881 (1996-08-01), Sridhar et al.
Clover process from CQDL 10/94, “Vergleich von PACTOR und CLOVER für den Kurzwellenfunk”, Gerhard Scheuing, DL1GGS, pp. 709-714.
Dirschedl Werner
Greubel Gerhard
Maurer Peter
Chin Wellington
Duong Frank
Rohde & Schwarz GmbH & Co. KG
Schiff & Hardin & Waite
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