
While I have written many blogs about Distributed Antenna Systems, this is one area where I do want to focus on…the right design versus cost....what does this actually mean? There has been tremendous marketing hype about some sort of design providing the ultimate solution for combining the WLAN with a DAS. (as I said in previous blogs...really again?) While some customers have gone down this path initially, it is like jumping out of a plane with a parachute…there is no going back....once you make this decision. (But in this case..you are now at 28,000 ft and you forget your oxygen). However many in the past years many have made the decision to bite the bullet and decouple the WLAN from the DAS that they have installed..the pain became too high. The reality is a coaxial distribution system was never designed to propagate 802.11 signals in an elegant fashion. Add to this the fast pace of the 802.11 standard in evolution essentially means that the coaxial infrastructure is future proofed…by “rip and replace”..certainly not cost effective when you consider the costs of the installation of a discrete WLAN architecture.
So why do I say this…let’s take closer look. As in my previous blogs, the whole concept of a DAS is to propagate cellular/PCS/ and public safety signals where diversity is not required. Signals generally extend from 700-1900MHz. Add WLAN 802.11b/g (at 2400MHz), at a signal strength of -85dBm, this is not much of a stretch to deal with the link budget. However if later you decide to add voice over IP, the signal strength has to be much stronger…around -62dBm. Still you can engineer the design…it takes a fair amount of work. However when adding 802.11a (5.0GHz), remember this came out after 802.11g, so now the entire DAS has to be entirely “re-engineered” and amplification has to be added (additional multiple points of failure). Now folks look to 802.11n and MIMO. It cannot be supported by earlier DAS/WLAN designs, and the entire coaxial infrastructure essentially is a rip/replace/re-design. With 802.11ac around the corner..well you guessed it. So one has to ask themselves…how really “future proof is this “concept” of a WLAN on a DAS and at what CAPEX/OPEX costs as well as a TCO? Whether coaxial cable used in DAS for WLAN, or Ethernet the architectures will never be able to support the bandwidth requirements of LTE or 802.11ac….only optical will. I have heard some that make the suggestion...go after the..fill in the blanks. My goal is to do the best for the healthcare industry...now and in the years ahead.
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