Method and apparatus for bidirectional communication between measuring devices and a data collector
To optimally receive smart meter control messages transmitted by a concentrator, in a meter having a transceiver for bidirectional data interchange, despite its minimal resources, a current modulation reference frequency which is subject to drift is shifted by the instantaneous frequency difference between the current transmitter-side reference frequency and the current transceiver-side reference frequency in the concentrator. Therefore, the current reference frequencies correspond in the downlink without having to intervene in the meter. This frequency difference in the concentrator is obtained by comparing the current receiver-side demodulation reference frequency with the current transmitter-side reference frequency, and the current transceiver-side reference frequency, on the other hand, from messages from the transmitter of the concentrator and from the transceiver of the meter which are received using the receiver of the concentrator. A frequency-measuring comparator only needs to be connected upstream and downstream of the demodulator in the concentrator for this purpose.
1. A method for bidirectional communication between a data collector having a transmitter and a receiver, on the one hand, and measuring devices having transceivers, on the other hand, by means of a reference frequency, the transceivers, the receiver and the transmitter each having an oscillator with oscillator frequencies being subject to drift and from which the reference frequency to be modulated or demodulated is derived, which comprises the step of:
shifting a current transmitter-side reference frequency by an instantaneous frequency difference between the current transmitter-side reference frequency and a current transceiver-side reference frequency derived from at least one data message from the data collector in order to continuously compensate for drifting of the reference frequencies and to transmit messages in a narrowband downlink connection from the data collector to one of the measuring devices being a meter.
2. The method according to claim 1 , which further comprises comparing a receiver-side reference frequency with both the current transmitter-side reference frequency and with the current transceiver-side reference frequency in the data collector and the instantaneous frequency difference is formed from derived differences.
3. The method according to claim 1 , which further comprises:
measuring the current transmitter-side reference frequency in a calibration message emitted by the transmitter of the data collector in the receiver of the data collector; and
measuring the current transceiver-side reference frequency in a data message emitted by the meter in the receiver of the data collector.
4. The method according to claim 1 , which further comprises measuring the current transmitter-side reference frequency in a calibration message emitted by the transmitter of the data collector and the current transceiver-side reference frequency in a calibration message emitted by the meter in the receiver of the data collector.
5. A system for bidirectional communication, the system comprising:
at least one measuring device having a transceiver;
a data collector having a transmitter and a receiver for a bidirectional interchange of modulated messages with said at least one measuring device;
said transceiver, said transmitter and said receiver each having an oscillator for deriving reference frequencies which are subject to drift;
said data collector further containing:
at least one comparator to which a current receiver-side reference frequency f 16 , a currently received transmitter-side reference frequency f 17 , and a currently received transceiver-side reference frequency f 13 are applied; and
a subtractor, connected downstream of said comparator, and determining a frequency difference Δf=f 17 −f 13 between two frequency differences (f 17 −f 16 ) and (f 13 −f 16 ), which shifts the transmitter-side reference frequency f 17 by the frequency difference Δf onto the transceiver-side reference frequency f 13 .
6. The device according to claim 5 , wherein:
said data collector further has conditioners, including a transmitter-side conditioner, for deriving the reference frequencies from oscillator frequencies; and
said subtractor is connected to said transmitter-side conditioner.
7. The device according to claim 5 , wherein:
said data collector further has a demodulator with inputs; and
said comparator is a frequency-measuring comparator connected to said inputs of said demodulator for demodulation of the receiver-side reference frequency f 16 or of the transceiver-side reference frequency f 13 .
8. The device according to claim 5 , wherein said oscillators are crystal-stabilized.
9. A system for bidirectional communication, the system comprising:
at least one measuring device having a transceiver and an oscillator outputting a transceiver-side reference frequency being subject to drift;
a data collector having a transmitter and a receiver for a bidirectional interchange of modulated messages with said at least one measuring device, said transmitter having an oscillator outputting a transmitter-side reference frequency being subject to drift, said receiver having an oscillator outputting a receiver-side reference frequency being subject to drift;
said data collector programmed to:
shift the transmitter-side reference frequency by an instantaneous frequency difference between the transmitter-side reference frequency and the transceiver-side reference frequency derived from at least one data message from said data collector in order to continuously compensate for drifting of the reference frequencies; and
transmit messages in a narrowband downlink connection from said data collector to said measuring device being a meter.