By Claus Lassen, HFC Networks; Steve Condra, Teleste Intercept; Arttu Purmonen, Teleste Corporation; Pekka Hilke, Teleste Corporation; Niko Suo-Heikki, Teleste Corporation; Henri Aittomaa, Teleste Corporation
The cable industry plans to leverage Data Over Cable Service Interface Specification (DOCSIS) 4.0 technology over hybrid fiber-coaxial (HFC) networks to meet the demands of future bandwidth-intensive applications. While it remains uncertain which new split frequencies cable operators will deploy in their networks, there is consensus that the upstream frequency band will expand (Ciarla, 2023; Segura, 2022). However, this extended upstream introduces new challenges. Among these challenges, upstream ingress (Ciarla, 2023; Hranac et al., 2022; Segura, 2022; Topazi, 2022), and common path distortion (CPD) stand out as significant issues (Heiler et al., 2022). While these problems have long been recognized, it is crucial for cable operators to continually evolve their strategies for managing them, particularly during the transition to high-split networks and the deployment of distributed access architecture (DAA) (Segura, 2022). Insights from various articles clearly show that addressing upstream ingress and CPD requires proactive measures, such as the deployment of proactive network maintenance (PNM) technology, which plays a crucial role in detecting and resolving these issues (Ciarla, 2023; Hranac et al., 2022; Volpe, 2019; Walsh, 2020; Wolcott, 2019). In response to the evolving landscape of cable networks, cable operators are striving to optimize workforce efficiency, improve subscriber experiences, and ensure reliable network performance through the adoption of innovative technologies and proactive maintenance practices (Volpe, 2019; Wolcott, 2019). Norlys, a leading Danish cable multiple-system operator (MSO), has been at the forefront, pioneering large scale high-split upgrades across its entire cable network infrastructure while concurrently rolling out DAA in Denmark. This case study elucidates the upstream challenges Norlys encountered and the solutions they employed. We then extrapolate these learnings to a North American context. This comprehensive approach is aimed at helping North American cable operators maintain high network uptime for the benefit of their subscribers and preempt issues before they negatively impact the customer experience. In the context of cable networks, a 'high-split' configuration refers to the utilization of frequencies below 204 MHz for the upstream (return path) and frequencies above 258 MHz for the downstream (forward path). This shift in frequency allocation presents both new challenges and opportunities for cable operators. Moreover, the adoption of DAA, which involves implementing remote PHY devices (RPDs) or remote MAC PHY devices (RMDs) in place of traditional fiber nodes, further transforms the network infrastructure. This paper is structured as follows: first, we define and categorize ingress and CPD; second, we delve into Norlys' experiences and the problems caused by ingress and CPD; third, drawing on the Norlys’ case study, we establish foundational premises to frame the subsequent discussion in a North American context; fourth, we examine the requirements for tackling upstream ingress and CPD issues in North American high-split cable networks. We conclude by outlining the limitations of the paper and discussing future developments that could assist cable operators in managing ingress and CPD in their networks more efficiently.