Impact of Echo Canceller Taps Quantization on Repeater Stability

The most relevant impairment experienced by on-channel repeaters (OCRs) is the presence of a coupling-channel between the transmitting and receiving antennas, that generates unwanted echoes. Echoes critically influence the overall system behavior, with harmful effects on the signal quality and, above all, pose a threat on the system integrity. Echo cancellers are usually adopted, therefore, to remove unwanted coupling contributions. In this paper we investigate the OCR stability problems arising from the joint effect of echo estimation errors and the quantization of the echo-cancelling filter taps. The probability of OCR instability is analytically derived and some performances figures are provided varying the quantization level and the channel model in realistic scenarios.