CTS 050: Introduction To DAS with Josh Gerst

Josh Gerst and I talk about an introduction to DAS, distributed antenna systems.

Welcome back Josh Gerst, Vice President of Engineering at RF Connect. He originally came on the show back in episode 27 and he’s back to talk more about DAS.

DAS stands for Distributed Antenna System where you take RF from one location and convert it to light over fiber so it could be distributed throughout a facility.

There are many moving parts to consider in a DAS. Some systems use CAT6 cabling and there are traditional DAS systems which use hybrid fiber coax. The hybrid fiber coax method takes multiple RF sources which could be multiple frequency bands. The headend would be used for RF consolidation.

Another system is a multi-sector DAS which is used for capacity. These systems often have 3 sectors where each sector is independent and each sector has different scrambling codes.

Without getting too far into the weeds and keeping this as an introduction to DAS we talk about stadium deployments. Usually multiple sectors are used in these environments due to capacity reasons. A sector may serve 1 or 10 remote units of 20W or 40W. That’s far from an introduction to DAS but it gives you insight into how this can scale.

One thing you cannot overlook with DAS is public safety. E911 is configured for sectors in a tower. Generally phones will log in their GPS on the tower which is then reported to assisted GPS. Public safety generally uses lower frequencies because of the penetration into buildings so we wont typically see it on the Wi-Fi frequencies.

For more of an introduction to DAS, check out RF Connect online and view a couple of videos found online here and here.

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About the Author
Rowell, CWNE #210, is a network engineer in Higher-Ed. He enjoys working with wireless networking technologies and loves to share and engage with the community. You can connect with him on Twitter, LinkedIn, and Facebook.

2 comments on CTS 050: Introduction To DAS with Josh Gerst

  1. Pete Mitchell says:

    I take some issue with Josh Gerst’s assertion that 600MHz spectrum being auctioned will certainly be a part of future DAS deployments. Josh correctly points out the superior propagation of 600, and it’s for that very reason such spectrum is best utilized in rural areas. In dense urban or stadium environments, higher frequency is as good, even better some argue, than low-band. Comments Rowell, Josh?

    1. Josh Gerst says:

      Hi Pete,

      Your analysis is certainly correct, but as we saw with the 700 Band (which has similar propagation characteristics to the 600 Band) the carriers will end up rolling out LTE (or 5G) on the band across the entire country. It is just too valuable not to use the spectrum everywhere. It will often be put on a DAS for continuity of LTE channels within a market not requiring hard handoffs, as well as making carrier aggregation possible with the higher throughput that allows. You are also right that it is not a given though what the winners will do with that spectrum. The auction isn’t complete yet, we don’t know who will end up winning what, but we do know that that spectrum will be nationwide, and we have it on our radar that it may be necessary to add it to new DAS systems going in now.

      Hope this helps and a great comment!

      Regards,
      Josh

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