The lack of technologies like cognitive radio aren't preventing mesh networks. If you're talking the useful bands for data transmission (ie, VHF and up but most

The lack of technologies like cognitive radio aren't preventing mesh networks. If you're talking the useful bands for data transmission (ie, VHF and up but mostly very up) then the only thing that matters is height above terrain. Unfortunately except for exceptional situations (coastal mountains or megacity roofs) that height and getting power up there costs a lot of money. That's why neighborhood and city mesh networks don't work. And it's why cell networks do.