Simultaneous sampling rate adaptation and delay control

A method of introducing a controllable, variable delay between a first equipment and a second equipment, the method comprising:

• receiving at a rate control input of a variable rate change filter, VRCF, a rate control signal;
• sampling by the VRCF an input signal at a sampling rate controlled by the rate control signal to produce a VRCF output signal;
• and
• the VRCF having a first delay;
• storing in a first in first out, FIFO, buffer, samples of the VRCF output signal and introducing a second delay in the stored samples to produce a FIFO buffer output signal;
• adding the first and second delays to produce a total delay;
• comparing the total delay to a target delay;
• generating the rate control signal based on the comparison;
• and
• outputting the rate control signal to the VRCF rate control input, the rate control signal causing one of no change, an increase and a decrease of the sampling rate of the VRCF.

A variable delay interface configured to introduce a controllable, variable delay between a radio equipment controller and a radio equipment, the interface comprising:

• a variable rate change filter, VRCF, having a signal input, a signal output and a rate control input, the VRCF configured to:
• receive a rate control signal at the rate control inputs;
• and
• sample an input signal received at the signal input at a sampling rate controlled by a rate control signal to produce a VRCF output signal, the sampling rate being one of greater than and less than a sampling rate of the input signal;
• the VRCF having a first delay;
• a first in first out, FIFO, buffer having an input and an output, the FIFO buffer configured to store samples of the VRCF output signal received at the FIFO buffer input and introduce a delay that proportional to a sampling rate of the received samples to produce a second delay;
• and
• a delay control unit configured to generate the rate control signal, the rate control signal being based on a sum of the first and second delays and a target delay received by the delay control unit, the rate control signal causing an increase in the sampling rate of the VRCF when the sum is less than the target delay and causing a decrease in the sampling rate of the VRCF when the sum is greater than the target delay.