This is an excellent article from NetWorkWorld that points to some the challenges with how hard it is to get unified communications to work within the enterprise. I have also included the NIST Link Budget Calculator. This article points more and why the FMC market and perhaps both why W-Fi and/or cellular should remain separate infrastructures.
On the technical side, there are some other issues. For example most DAS type systems were designed for 850MHz/1900MHz, and/or 800Mhz, with a signal strength of -85dBm. 802.11b/g at 2.4GHz (2400MHz), was not much of stretch due to the link budget and slight shift in frequency. When voice (802.11b/g, then the requirement was and is to provide a much stronger signal strength, (-65dBm). This could/can become potentially the threshold due to the link budget. Adding 802.11a (5.0GHz), adds several challenges to the link budget and then the question is how 802.11n with MIMO will operate. What ever the case regarding the technical caveats, a "link budget" calculation has to be made for every design as well as creating the "predictive model". Meeting the link budget requirements and the cost of combining or separating the designs may determine if it makes sense for an enterprise combined cellular/WiFi FMC model, or separate out both in discrete environments of which may be more the intended model.
Download NetworkWorld%2012%2008%2008
http://www.antd.nist.gov/wahn_home.shtml
