“We are trying to solve the problems of making highly configurable distributed systems that move as fast on the edge as you do these days in the cloud,” said Rob Chandhok, a former senior software executive at Qualcomm who joined Helium as president and COO in December. “If you can reach end nodes with software easily and quickly it’s a competitive advantage,” he said.
The code runs on an RTOS on a Freescale K64F12 applications processor embedded in each node. The nodes sit on a star network, communicating through an access point which acts as a bridge and does not contain a processor.
The nodes should run for more than a year on two AA batteries. Chandhok pooh-poohs talk of IoT nodes that run for a decade on a button cell. “The question is what’s your goal, won’t your applications change in ten years,” he asked.
The Helium network is based on the 802.15.4 physical-layer chip supplied by Atmel, but Helium uses its own media-access control and software stack rather than 6LoWPAN or Zigbee. The net lets nodes dynamically switch between 900 MHz and 2.4 GHz frequency bands, it supports hardware-based root-of-trust security with an Atmel chip and rather than use mesh networking it pumps up radio power and sensitivity to boost distance.
The Helium net “is good about getting on and off the network quickly…others have long negotiation phases,” said Chandhok, declining to give specific numbers.
The network can be configured to use only the 900 MHz or 2.4 GHz bands. Alternatively nodes can listen for interference and negotiate with access points about which band to use at any given time. Nodes can be moved but do not support operation while mobile.
“I don't know of anyone else switching between bands, it would be completely proprietary and therefore limit the end devices that could talk to their network,” said Geoff Mulligan, chair of the LoRa Alliance that supports a rival IoT network. “I would be surprised if they get the world to accept this non-standard band hopping,” he added.
Separately, Helium chose not to use mesh networking, an increasingly popular approach to expand reach and reliability of an IoT network. Instead it uses more powerful power amps on its transmitters and more sensitive low noise amps on its receivers to have a reach that spans several floors inside a building or two or three block outdoors in a city, said Chandhok, again declining to provide specifics.
“A group of us in the company have a lot of experience in Zigbee and other mesh networks and never saw the benefit in real-world apps,” said Chandhok, citing the battery drain from waking up nodes to relay messages and larger software stack required for meshing. “Meshing is not bad but in general our coverage is better without it,” he said.
Others have adopted a similar approach of using better power amps and LNAs as an alternative to meshing. Alternatively, some mesh implementations synchronize communications among nodes to implement meshing in ways that can use less power than point-to-point connections.
The Helium node includes an RF module, a sensor module and a main board.