"cbg_reproducibility"

"Building wireless performance (BWP) metrics quantify how an indoor structureshapes the wireless channel and guide wireless-friendly architecturaldesign.  Existing metrics target interference, signal power, line-of-sightmultiple-input multiple-output (LOS-MIMO) capacity, or the time-domainroot-mean-square (RMS) delay spread, but none directly addresses thefrequency selectivity that dominates wideband signals such as Long-TermEvolution (LTE), 5G New Radio (NR), and Wi-Fi~7. We close this gap with the\\emph{Coherence Bandwidth Gain} (CBG), defined as the ratio of thebuilding-internal coherence bandwidth $\\E[\\BcI]$ to that of an equal-areaopen space $\\E[\\BcO]$. Under the 3GPP TR~38.901 lognormal RMS-delay-spreadmodel, we derive closed-form expressions for both quantities via themoment-generating function and prove that the CBG is invariant in thecorrelation-threshold constant $K$ of $\\Bc\\!=\\!1\/(K\\tau)$, making it anintrinsic property of the building. A closed-form frequency-selectiveoutage probability $\\Pout(W)$ further reveals a \\emph{frequency-dependentBWP reversal}: layout choice swings indoor outage by up to $70$~percentagepoints inside a $3$--$30$\\,MHz critical design window, while it isirrelevant for narrowband signals and insufficient for 5G\/Wi-Fi~7. Closedforms agree with Monte Carlo simulation to within $0.2\\%$, with$K$-invariance holding to machine precision."