Managing upstream bandwidth is a critical issue for cable operators today, yet it still carries quite a bit of confusion. Now that DOCSIS 3.0 is widely deployed, there are questions about whether analog return paths are sufficient for upstream traffic, or whether operators should be migrating to digital returns. Not surprisingly, the situation is a nuanced one. Certainly digital returns can create greater operational simplicity, and they have the potential to provide higher performance. However, performance rarely measures higher in actual deployments, and quite often, going digital doesn’t make economic sense. Worse, it’s quite possible that digital returns will have to be replaced at some point in the future when upstream spectrum is extended up to 85 MHz.
There are several considerations for operators looking at their DOCSIS return paths:
- Quality – Run an NPR (noise-to-power ratio) test to determine actual performance levels. (Instead of relying exclusively on BER tests)
- Ongoing OpEx – At what point will you recoup capital costs from increases in operational efficiency?
- Interoperability – If you’re adding new return path equipment, how flexible and open is it for interoperating with equipment from other vendors?
- Future-Proof – Will your return path equipment support frequencies up to 85 MHz?
- Other Upstream Solutions – Have you implemented other solutions for improving upstream bandwidth such as S-CDMA?
Often the primary obstacle to adding more channels and upgrading to higher modulations is an operator’s existing return path quality and alignment. Before DOCSIS 3.0 was widely deployed, these variables were less significant and could often go unnoticed. Now that the problems are more obvious, MSOs are looking for solutions. Migrating to a digital return path is a great move in some cases, but laser technology improvements have made analog returns an equally viable solution. Whether an operator chooses to go digital or not should depend on a careful examination of several factors.