Thank you for a nice article... The “energy per bit” is any day a better indicator of power efficiency than other metrics and this has been raised in other areas like design of high speed motherboards for 100Gb/s ethernet.
One issue that doesn't seem to have been addressed above with respect to power efficiency in a M2M context is the issue of multipath fading...
As we unveil EE Times’ 2015 Silicon 60 list, journalist & Silicon 60 researcher Peter Clarke hosts a conversation on startups in the electronics industry. Panelists Dan Armbrust (investment firm Silicon Catalyst), Andrew Kau (venture capital firm Walden International), and Stan Boland (successful serial entrepreneur, former CEO of Neul, Icera) join in the live debate.