With the 72 uplink channels we have in the USA, and the limitation of current gateways to 8 channels, we have some frequency planning to do. The 72 uplink channels are divided into 8 sub-bands, each containing eight 125kHz wide channels and one 500kHz wide channel. The question is, as we deploy gateways (eventually blanketing metropolitan areas or even whole states), how do we want to assign gateways to sub-bands?
We could put all gateways on one sub-band (say #7). The principle advantage of the single sub-band plan is redundancy/localization: multiple adjacent gateways can pick up the same signal, providing redundancy in case of interference / loss, and allowing poor-man's localization using RSSI (and, eventually, localization via DToF ?).
Another plan would involve a "cellular" assignment of sub-bands, where adjacent gateways listen on distinct sub-bands. This makes better use of spectrum (unless you figure that more retransmissions may be required due to lack of redundancy).
My opinion is that we should stick to a single sub-band plan for USA until we hit capacity issues, and only then (re)assign gateways to a secondary sub-band.