DAS (Distributed Antenna Systems), were designed with the role of propagating cellular, PCS, and public safety signals in a holistic environment. With the design intent of this; they have performed very well. While I was never an advocate of distributing WIFI (802.11a/b/g (now N)), on a DAS, it could be done in a limited fashion,simply because of the proximity of 2400MHz (original DAS design, i.e. to 850/1900MHz, etc, and the signal level of -85dBm would be adequate.) Link budget calculations held out (it is all a matter of physics..www.google.com for link budget) for 802.11b. When voice over IP came around, this again placed constraints, such as roaming, -65dBm signal strength and the need for zero tolerance of latency for voice quality, (need at least 180 msecs latency even while roaming))to ensure the SLA. (Service Leval Agreement) Now with 802.11a (5.0GHz) this totally changes the dynamics for the link budget, "costs go way up for redundant architecture". Rendudant means two perhaps side by side coaxial passive designs. With the advent of and now with 802.11n from a technology and financial perspective to such as MIMO on a single point non-diversity antenna simply this convergence of 802.11b/g/a/n does not perhaps make technical and financial sense. Even though designs of WIFI over DAS place the AP(s) in the IDF, you still will need active components (booster/ampliers), for 802.11n in the ceiling. Each enterprise needs to do their internal technical and financial analysis to determine the the best CAPEX, OPEX, and TCO. Again, I point out (as the right business model) the needs are present for a discrete WLAN to do its job, and for the DAS to be deployed in the traditional fashion. Both systems and designs will then operate in the most optimal condition (for what they were intended), and at the best price point. However, some point out that this may be incorrect or misleading or take issue with my opinion. However, marketing is separated from technical reality. Enclosed is from the "public domain" Cisco Systems web site. www.cisco.com Go to section 2-35, of Wireless Considerations for Healthcare. It talks about DAS considerations and the WLAN. By the way, very well written piece from Cisco.
