ATIS - 0300221
Operations, Administration, Maintenance, and Provisioning (OAM&P) – In-Service, Non Intrusive Measurement Device (INMD) – Voice Service Measurements
|Publication Date:||1 October 1995|
This American National Standard provides specifications for transmission measurement devices utilized to measure various parameters of importance to voice service transmission maintenance of telecommunications networks. This standard is limited to measurement devices that provide measurements on an in-service, nonintrusive basis. The device is commonly identified as an in-service, nonintrusive measurement device (INMD). These measurement devices are utilized primarily for the measurement of voicegrade analog parameters such as speech level, noise level, echo path loss and echo path delay. In addition, they also may be utilized to measure parameters associated with digital transmission systems, the transmission performance of which impact the quality of voicegrade channels being transported. This standard specifies interface, measurement range and accuracy requirements for measuring voicegrade transmission parameters as well as descriptions of optional functions associated with these parameters. Descriptions of measurement algorithms that have been verified to meet the accuracy requirements of this standard for the measurement of speech level, noise and echo path delay are included in an annex. The algorithm for echo path loss is currently under study. Algorithms, other than those in the attached annex, are under investigation and will be added as additional annexes when tests are completed to ensure that they meet the required measurement accuracy. This standard does not require any device to measure all parameters, or any particular subset of the parameters specified. Nor does the standard specify the algorithm for selecting the circuits to measure the protocol by which a network element could convey information to the INMD or thresholding algorithms. These issues, as well as criteria for the detection and verification of circuit conditions relating to traffic types and voiceband data performance parameters, are expected to be addressed in future standards.
This document is intended for use as the standard for maintenance application to detect network anomalies affecting transmission performance on voice services on an in-service basis.
The INMD is used as a stand-alone device or can be used as part of a network element. They may be deployed at selected switch and facility nodes in telecommunications networks to (a) measure the in-service performance parameters of voicegrade services and (b) locate and analyze network anomalies. For measurements on a switched network, analysis of network anomalies is convenient when connection information such as calling and called address digits, circuit assignments involved, etc. are known along with the measured performance. Recording of this information does not constitute intrusion of privacy, since speech intelligence is not monitored. Other optional functions may be added to make the INMD more useful. The INMD can only be used at a four-wire point. In order to study troubles on two-wire subscriber lines, the INMD must be connected to four-wire trunks on the network element, (that connects to the subscriber lines under study). In order to isolate a problem to a particular subscriber line, some means of conveying connection information from the network element to the INMD must be employed. For facility access, the INMD monitors the MF or DTMF signaling; however, in cases such as signaling system seven, where switch access is used, a new standard will be required to define the switch interface protocol. The INMD measures transmission on the path-including the customer-provided equipment, to the point of INMD measurement access. In this way the INMD can detect transmission anomalies on the built-up connection. These anomalies can be caused by the customer environment, loop, switches and trunks, including anomalies at interfaces between these network elements. In particular, the INMD can detect anomalies not otherwise detectable by many traditional out-of-service tests. Some of these otherwise difficult-to-detect anomalies are:
- intermittent fading;
- acoustical feedback;
- room noise;
- defective customer equipment;
- intermittent leakage on metallic circuits;
- intermittent noise;
- design violations;
- pair gain system problems;
- digital switch level and echo control problems;
- echo problems at the loop-to-trunk interface;
- tones and announcement level control problems; and
- switch translation problems that cause violations in network loss plans.
Although the INMD is able to detect these anomalies, it should be noted that the INMD cannot specifically distinguish between things, like room noise and noisy cable or between acoustical feedback and echo problems. Similarly, the INMD cannot distinguish between a trouble on a trunk, a switch, the terminating subscriber pair, or the subscriber equipment. Network anomalies detected by the INMD may be subsequently isolated to the affecting network element by applicable out-of-service tests or facility performance monitoring. As an alternative to routine testing of network elements for proactive detection of network anomalies, the INMD is effective when used for call sampling. In this way, there is no need to maintain large routine testing databases. For postactive detection, the INMD is most effective when used as a portable device for detecting intermittent problems. Standalone, facility access INMD systems complete with proprietary interfaces to data collection and analysis software currently exist and are being used by service providers.