Optimization Tip #1:  Afraid of voice overages?  Avoiding them can be expensive!

It is much more common that we encounter companies running their voice pool buffers too high than too low.  Since the cost of overshooting a voice pool can be expensive, most wireless administrators aim for safer than needed buffer levels motivated by their fear of overage charges.  However, your smartest strategy is one that aims to experience an occasional overage bump.  The cost of carrying too many minutes in your voice pool means the carrier profits from your underutilization.  A rule of thumb is that for every 10% excess buffer you carry it will increase your voice pool costs by 4%.  If you are carrying a typical 50% buffer, you are paying 20% more on those voice minutes than you should.  Most strategies, including those advocated by carriers, are formulated by identifying seasonal  high water marks, then adding a small buffer and running on autopilot at that level throughout the year.  While this may represent a low effort tactic it is not the lowest cost approach.

Sizing your pool buffer is a bit of an art but it is a mistake to avoid overage at all cost.  The chart below shows actual usage data for a typical fluctuating usage pattern of 4,000 voice devices.  There are three cases displayed that reflect three different pool buffer strategies.  The lowest cost answer may not be the case you would intuitively select.

It turns out that Case 1 above is the most expensive annual scenario.  The Case 1 overage strategy yields overpayments in every month of the year. It turns out in this example averaging roughly 1M pool minutes a month, both Case 2 and 3 are less costly than Case 1.  Even Case 3 with a couple of annual overage months is less expensive than Case 1 by $16,173 annually. Case 2, the best choice, is $22,994 less expensive than Case 1.  A smart buffering strategy as demonstrated here can save 15% or more annually on the voice access fee costs.