All the hype around the Internet of Things (IoT) has led to speculation that there will be billions of devices added to networks over the coming years. Fundamentally, it seems that little attention has been paid to the overall radio environment when making these predictions. Governments licence the spectrum to make money but fundamentally, to help prevent interference. Whatever the protocol, as the airwaves become more crowded, the affect is to shorten the effective range of the communications. This is why licencing of the radio waves is about both the maximum power of transmission and also the duty cycle, how many times can you transmit in a given period.
The vast majority of the communications networks today are focusing on the higher ends of the spectrum because they need increased bandwidth for richer formats of communication that use higher data rates. Then there are a group of networks around the 868-900Mhz range which are generally focused on sending smaller packets, less often. These networks generally limit both the size of the communications and the number of communications in any given period. The design compromise is that this means they are only really suitable for fixed assets and sending tiny amounts of data.
There is a very important point about network congestion that is often missed. If the network generates a control channel, then the difference in power consumption for a device looking for a control channel in an area of high interference as opposed to clear air is around 300% in terms of power usage. You could equally say this means it takes three times as long, as radios generally use the same amount of power to listen as to transmit and therefore power and time are interchangeable to a degree. The effect that is perhaps more subtle and often overlooked is the time impact on the network overall. Everything is taking longer. In highly congested areas, the communications therefore run slower or to put it another way, the communications are limited to the loudest devices, or in other words, the closest devices.
When you consider that that the maximum power on the 868MHz in Europe in the licence free ISM bands is 500mW, or half a watt, think about the impact this has on other users trying to do low power 868MHz solutions. There is a real danger of being drowned out.