This is part six of a series. Read part five here.
In the previous blog I ended with a comment that the continuing shrinking in size of the aggregator will happen as we learn to improve on power efficiency and wireless communications. Surprisingly, it is not dependent on improving raw performance or driving integration.
Several years ago, a group of us were asking this very question of how to shrink a system. As I remember, our initial thought came from some work that was being done at UC Berkeley called “Smart Dust”. One of the questions we began to address was what the relationship was between performance and wireless communications. The simple version of the question became, "Is it more power efficient to compress a bit of data or to transmit a bit of data?" To our amazement, the answer to this question helped determine whether a computer system needed to have more performance or higher communications bandwidth. The intent to create smaller devices such as smart dust demanded the power dissipation of the computer be low enough to run off of body heat. It is worth a short pause for me to explain what I mean by body heat.
During that same time period I was driving the idea of lowering power dissipation in digital signal processor devices. We were moving from five volt devices to thee-volt devices. It seemed reasonable that it would be two volts next, followed by one volt and beyond. As I spoke to the IC design community, it felt like they weren’t catching my vision of the shrinking voltage that would power the devices. So, I finally suggested that the ultimate goal would be body heat. In other words, the devices would operate properly using energy scavenged from the environment. They would not need external electrical power, nor would they require a storage element (I called them energy buffers rather than batteries or capacitors).
Now back to the story of how the aggregator communicates with the rest of the IoT. If we assume the real need for body heat driven devices is at the interface to the real world, we may not need to worry about aggregators needing to run off of body heat, but they will need to communicate with devices which do run off of body heat (i.e., smart sensors) – and, if not off of body heat, at least low enough energy demand to have batter lives in the order of decades.
So, the aggregator will need to have an ultra-low power communication link with the many smart sensors (perhaps thousands) it is assigned to communicate and aggregate the data it receives into information. It is the information it will send on to the cloud for the final actions. The communications with the cloud will be done with an industry standard method. The communications with the smart sensors will most likely be proprietary rather than a standard in order to guarantee minimal power dissipation at its needed communication rate.
- What was the voltage of the first processor with which you designed? As a starting point, mine was at 10 volts.
- What was the data rate of the first modem you used? As a starting point, mine was 300 bps.
- Do you still use the word “baud” in conversation? Have you ever used it in conversation?