By Jennifer Andreoli-Fang, PhD, CableLabs; John T. Chapman & Tong Liu, PhD, Cisco; Damian Poltz, Shaw Communications
One of the next big frontiers for the cable operators is to transition into becoming mobile operators and doing so in a cost-effective way that reutilizes their main assets – the hybrid-fiber coax (HFC) plant.
Native DOCSIS technology provides a good starting point for cable operators to get into (backhaul, midhaul, and fronthaul) xhaul for mobile, but may not be enough to support the ultimate latency and timing requirements needed for future mobile traffic. The cable industry needs readily deployable technologies to take the DOCSIS network from a merely cost-effective xhaul network to a great high performance solution, all without expensive upgrades and without moving to a higher cost fiber-only solution.
Low Latency Xhaul (LLX) is a part of a group of technologies that facilitate xhaul over DOCSIS. LLX is key to significantly reducing the upstream latency that mobile traffic may experience while traversing the DOCSIS link. Other companion technologies that are part of this technology suite are precision timing and synchronization, predictive granting, and centralized or distributed hierarchical QoS.
This paper starts with a baseline case of transporting mobile traffic over native DOCSIS technologies. It will then introduce four key technology areas that improve the performance and the cost of xhaul over DOCSIS networks. These technologies are:
- LLX, which utilizes the bandwidth report (BWR) message,
- DOCSIS distributed hierarchical QoS,
- DOCSIS predictive scheduling (DPS), and
- DOCSIS Time Protocol (DTP) for timing and synchronization.
Tradeoffs between performance and implementation complexity will be discussed.
The paper includes key results from a recent LLX trial conducted jointly with Shaw, Cisco, and Sercomm, and CableLabs. The results demonstrated that LLX provides the latency performance for DOCSIS that is virtually indistinguishable from fiber, thereby enabling a host of low latency 5G applications such as ultra-reliable low-latency communication (URLLC), mobile gaming, and videoconferencing, at a fraction of the cost of fiber installations.
It is our hope that operators can use this paper as a high-level guideline to determine the right technologies for their xhaul needs.