Components > Advanced Semiconductors Blog

What does DOCSIS 3.1 mean for GaAs?

by Eric Higham | 11月 27, 2013

I had the opportunity to attend SCTE’s CableTec Expo 2013 in Atlanta last month.  In a completely unsolicited plug, if you have a chance to go to Atlanta…go! There are many great restaurants, like Legal Sea Foods and Ruth’s Chris Steakhouse, an excellent aquarium, Centennial Olympic Park and an arena within walking distance of the Georgia World Congress Center. However, I either was attending the Expo or busy in very productive sessions and meetings during my stay…so many of the sights of Atlanta will have to wait until next time! J

Among the things that kept me busy were a very packed trade show floor and the promise of DOCSIS 3.1. GaAs component manufacturers are very excited about the prospects for the next version of the DOCSIS specification. The benefit of this new specification from a performance standpoint is speed. The thought is DOCSIS 3.1 will enable 10 Gbps downstream transmission and 1 Gbps upstream transmission. The component industry is very interested because the specification allows for increasing the upper end of the frequency band to 1.2 GHz and changing the upper end of the return path frequency to 200 MHz. In addition to the increase in spectrum, these increased speeds are enabled by using OFDM in the physical layer, LDPC forward error correction schemes and modulation schemes up to 16384-QAM! This is all very good for GaAs components, because imagine the linearity required for the 16384-QAM, or even 4096-QAM modulation I/Q diagrams. This quick evolution to much higher performance requirements and the roughly $67B operators have spent on CapEx from 2008 – 2012 have the components industry very excited, perhaps picturing a wholesale upgrade of the cable ‘plant”.

Undoubtedly, operators are considering the $67B in CapEx investment, as well. In the sessions I attended, the common themes were “backward compatibility”, “efficiency” and “extending useful life”. It appears that the Google Fiber project that is rolling out 1 Gbps networks to consumers in the US has had a substantial impact on the cable industry. One speaker mentioned the “take rate” of 1 Gbps services is less than 1% and the largest take rate is in the 18 – 20 Gbps range, well within what DOCSIS 3.0 is currently providing, but several speakers mentioned the seriousness of the Google Fiber threat to the cable industry.

The clear message was that DOCSIS 3.1 had to be backward compatible with DOCSIS 3.0 and that the technology has to work with existing spits and plants with no need for upgrades. The other clear message is that a very important differentiator for DOCSIS 3.1 is spectrum efficiency. One speaker mentioned that the new spec will be 50% more efficient and this translates to cost savings or more offerings (and more revenue) at the same cost for the operators.

The timing that is being discussed has silicon (ASICs, FPGA, etc. for the processing portion) developed in 2015 with products available in 2015. The common consensus seemed to be that cable modems at the premises and cable modem terminations systems (CMTS) in the headend would be the first functions to incorporate the DOCSIS 3.1 specification. In this scenario, the infrastructure would be unchanged. The evolution seems to take into account that DOCSIS 3.0 is still in its infancy and operators are just starting to realize revenue on their investment. It appears that as more capacity is needed and more services are offered, an increasing amount of CapEx will shift from 3.0-compatible networks to 3.1-compatible networks and it will be more of a gradual evolution rather than a dramatic revolution.

While it doesn’t appear that DOCSIS 3.1 will be responsible for a lot of holiday presents for the compound semiconductor industry this year, it is clear that change is in the air. Higher frequencies, higher linearity and lower distortion are all very good for the GaAs industry. In the short-term, it appears system designs will be evolving toward higher frequency, higher linearity requirements, without the benefit of high volumes.  Over time, as the services and capacity requirements increase, the volume will likely pick up as more networks upgrade to DOCSIS 3.1.


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