<p>A method of deriving an indicator of the signal quality in an in-service packet-based network at least having means to detect errors in packets and means to determine the overall amount of network traffic received. The method comprises the steps of: obtaining a value of the number of packets received having errors therein; obtaining a value of the overall amount of the network traffic received; calculating the indicator of signal quality (eBER) using the ratio of the number of packets received having errors therein to the overall amount of network traffic received.</p>
