Superior Upstream Weblog Sequence Introduction
Within the Superior Upstream weblog sequence we’ll discover how cable operators have historically managed upstream bandwidth capability planning, how market dynamics and technical innovation are driving modifications, and the place issues are possible headed within the coming years. On this entry we’ll talk about the “Extra Hz” strategy – or the way to make extra spectrum out there so as to add upstream carriers.
Extra Hz Introduction
Again within the early days of two-way crops, the best answer to rising upstream capability was to easily add one other provider or two. Quick ahead to at present, and in a lot of the 42MHz world and among the 65Mhz world, there isn’t a such factor as vacant spectrum for including carriers. Through the early days of the pandemic when upstream capability was probably the most scarce, operators had been including 3.2MHz and even 1.6 MHz carriers proper towards the diplexer and deeper into the junk band to squeeze out a number of further Mbps. This was clearly not a fascinating and even ample answer, so consideration turned to mid-split and excessive break up architectures.
What’s a Mid-Break up, What’s a Excessive-Break up?
The DOCSIS 3.0 specification calls out an upstream frequency vary of as much as 85MHz, which is now outlined because the Mid-Break up. Some operators appeared into the fee/effort required to implement this, however few went past the pilot section because the profit simply wasn’t definitely worth the effort. Pre-2020, the upstream merely wasn’t the sore tooth demanding consideration. DOCSIS 3.1 launched the idea of a 204MHz upstream, or the Excessive-Break up. This strategy is extra disruptive for causes mentioned under, however because it provides 5x extra usable spectrum vs 42MHz plant implementing it will possibly truly defer the necessity for upstream-driven node splits for a few years. Additionally it is required to ship 1Gbps upstream speeds which can be on many operators service providing roadmaps. Like all the things in life, the advantages of elevated spectrum out there for carriers doesn’t come with out prices and challenges.
Mid-Break up/Excessive-Break up Challenges
- CPE Compatibility – Solely CPE with 204Mhz diplexer are able to making the most of the prolonged spectrum. Activating 204MHz doesn’t require that each one CPE (together with legacy STB’s) get replaced nevertheless assuming that the downstream is vacated as much as 258MHz.
- Downstream Spectrum Loss – As acknowledged above, spectrum as much as 258MHz have to be vacated to accommodate the 204MHz upstream plus guard band. Operators with 860MHz or 1GHz plant can normally accommodate this by means of analog reclamation and/or elevated video compression, however 750MHz and under crops might have downstream expansions to keep up capability.
- Actives and Diplex Filters – That is the elephant within the room, each lively have to be touched in addition to some passives to put in 204MHz-capable gear and diplexers. There are a number of approaches to getting this executed with minimal buyer disruption, however particulars are past the scope of a weblog.
- FM Interference – FM interference is very troublesome within the downstream at present as FM alerts are at all times within the air, and may be fairly robust close to transmission websites. Some operators merely vacate the downstream spectrum round highly effective native stations to get round this. With excessive break up networks the FM band strikes to the upstream, the place one leak can take out the whole upstream vs only a handful properties as is frequent on the downstream. Conceding helpful upstream spectrum is a a lot much less enticing possibility, and extreme energy from FM interference can tax the upstream laser energy price range.
- Sign Leakage – Many operators monitor downstream sign leakage each to seek out shielding weaknesses that may permit ingress into the plant and in some international locations to satisfy governmental mandates for aeronautical band purity. With high-split architectures the aero band strikes from the downstream to the upstream, forcing modifications in how leakage detection is finished. Many various strategies are being proposed, with detection of OFDMA Upstream Knowledge Profile (OUDP) take a look at bursts that DOCSIS 3.1 CPE are already able to transmitting within the upstream being the main candidate. Trendy FPGA-based sign leakage detectors are basically highly-sensitive software program outlined radios, so transitioning to detecting completely different leakage signatures needs to be attainable.
- Return Path Monitoring/Ingress Troubleshooting – Ingress is worst on the low finish of the return spectrum, however operators should make it possible for return path monitoring gear and discipline meters are 204MHz-capable to see the whole upstream. That is particularly essential within the FM band.
- OFDMA Required for Excessive Break up – DOCSIS 3.1 solely specifies OFDMA assist above 85MHz, so there isn’t a profit to excessive break up architectures except accompanied by OFDMA. See HERE for extra particulars on OFDMA
Whew – that’s plenty of challenges, however for a lot of networks increasing the upstream spectrum out there by means of mid/excessive splits mixed with one or each of the opposite main choices makes nice monetary and operational sense. Whether or not used as a stop-gap to defer node splits whereas DAA options proceed to mature, deployed as a path to 1Gbps providers, or some other cause mid/excessive splits will most actually play a task within the superior upstream plans for a lot of operators across the globe.
Wish to study extra? Take heed to the Broadband Lounge Podcast Sequence or go to the VIAVI Superior Upstream Web page for extra data.
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