By James Medlock, Akleza, Inc.; Robin Lavoie, Cogeco Communications; Bernie Cadieux, Electroline Equipment Inc.; Frédérick Plante, Electroline Equipment Inc.
Locating return path noise sources in a hybrid fiber coax (HFC) plant continues to be a challenge for cable operators. Traditional techniques that utilize various methods to segment the return path in the hopes of identifying the leg contributing to the noise can be both time consuming and have a negative impact on subscribers due to network disruptions.
Society of Cable Telecommunications Engineers (SCTE) 279 [1] defines a standard for a new smart amplifier and SCTE 283 [2] defines an associated information model that provides monitoring and control functions. One feature defined in the standards is an upstream ingress switch. This is typically a threestate switch on each upstream input port, allowing the port to be configured as “on” (no extra attenuation), “off” (large attenuation added), or “-x dB” (specified attenuation added). By leveraging this feature, a remote application can temporarily adjust the attenuation of an upstream port while monitoring the return signal to determine if there is any change to observed ingress. By systematically traversing the network, it is possible to isolate the source of ingress to a specific amplifier leg.
The concept of an upstream ingress switch adjusting attenuation is not new to the industry and more commonly has been referred to as a “wink” switch. While in North America wink switches are not commonly deployed, there are some operators in Canada and Europe that have deployed wink switch functionality through standalone devices installed in the HFC network, or as add-on devices integrated into legacy amplifiers. These environments provide examples of how an end-to-end solution can operate once smart amplifiers are deployed and the function is more widely available. Additionally, some remote physical layer devices (RPDs) also support temporary ingress attenuation on each return port, providing yet another isolation point.
In this paper we will discuss leveraging the integration of proactive network maintenance (PNM)upstream triggered spectrum capture (UTSC), automated impairment detection, HFC plant topology data, and ingress switching to localize ingress noise events. We will discuss the challenges of implementing such a solution when considering intermittent and short-lived noise bursts, HFC plant topology discoveries, and the impact on cable modems related to available transmit headroom. Finally, we will look at the status of each component required to implement an end-to-end solution and any alternative solutions available using existing equipment.