Messy Networks for the Internet of Things
Warning: this post gets a bit technical. It’s for the LPWA geeks.
You probably know I’m a big fan of new low-power wide-area networks for the Internet of Things. And most people know about two major benefits of these networks: years of battery life and miles of wireless range. (I talk about why that combination matters here.)
But there’s a third, equally important benefit of these new IoT networks. It’s discussed less frequently, maybe because it’s about the networks rather than the devices. Maybe because it’s harder to understand.
It’s this: New IoT networks are designed for unplanned, ad-hoc, network deployments. And messy networks are awesome for IoT.
Cell phone networks aren’t messy. They’re carefully planned, with minimal overlap, to maximize the efficiency of the network. Network engineers shoot for this type of tower plan:
For a phone network, the handoff is all-important. Handoffs happen when one cell tower transfers a phone’s connection to another tower. Handoffs have to work right every time, at 60 miles an hour, without interrupting your conversation with grandma.
Seamless handoffs take hard science. They made cell phone networks possible. And they require that each tower know to which other towers it’s adjacent, so it can coordinate handoffs with those towers.
New IoT networks don’t do handoffs. They don’t need to, because they don’t carry phone calls. They send messages.
Once you’ve eliminated handoffs, your cell towers (or “gateways” or “access points”) don’t need to be very intelligent. They don’t coordinate with adjacent towers, they just forward packets from devices to the cloud and back.
That means you can move the network logic to a “network server” in the cloud. That network server understands the network holistically and dynamically, and handle “messy” network architectures.
This is where it gets interesting.
With dumb towers and network management in the cloud, overlapping cells add no real complexity to the network. A cell phone only connects to one tower at a time (except during handoff), but on a new IoT network, a packet transmitted by a sensor might be received by several different towers. And that’s just fine. The network server just de-duplicates the redundant packets. It also decides which tower to use to send messages back to the device.
This flexible (but I’ll call it messy) architecture is really useful for network deployments.
First, it lets carriers build for coverage first, and add capacity later, with a macro/micro-tower approach. They start with one radio on a high tower to cover a city, then drop in more towers where they need more capacity, without any real planning up front. LTE networks do something similar with cell-splitting, but it’s much more complex and requires real network coordination. With IoT networks, you just drop in another tower and the network server figures it out.
Second, you can build reliability through redundancy. Instead of putting one cell tower in a location, you might put in four, so if one goes down, you have 3 backups for fail-over. While this might seem more expensive, it actually allows you to use cheaper tower sites, cheaper power supplies, and cheaper backhaul. If you save an order of magnitude in cost per tower site, a redundant network might be both more-reliable and cheaper to build.
Dumber towers and redundancy make the tower equipment far less expensive. Equipment on an LTE tower might cost $50,000. On a new IoT network it’s more like $1,000–5,000, and coming down quickly.
Finally, hybrid networks that combine user-deployed equipment and carrier-deployed equipment are easy to build. This is the messiest network of all, where carriers allow customers to place their own towers or gateways wherever they want them. This would quickly break a cell phone network, but a modern IoT network can sort it all out in the cloud.
Customer-deployed gateways solve for a major weakness of existing 3G and LTE networks: they don’t really have coverage everywhere. Say you need to connect a vending machine in the basement, or a moisture sensor on a rural farm — chances are, you won’t have cellular coverage there. But if your IoT network carrier lets you place your own low-cost micro-tower (imagine a wi-fi router on steroids), you can always get coverage wherever you need it.
This flexibility in approach makes building IoT networks far cheaper than traditional cellular networks. It empowers customers to get coverage where they need it, while saving carriers backhaul costs. And it allows for much-cheaper initial rollout of networks. All by eschewing handoffs and putting network logic in the cloud.
I think messy, hybrid, unplanned cellular networks for IoT have a bright future. What do you think?
Daniel is co-founder of Beep Networks, a maker of location-aware sensors and systems for low-power wide-area networks.