Imagination positions itself for 802.11ah for the Internet of Things
The Whisper Radio Processing Unit (RPU) from its Ensigma division uses optimized, configurable PHY and MAC blocks to support common IoT protocols such as WiFi, Bluetooth and Zigbee with low power and low cost. It will also support the coming 802.11ah sub-GHz version of WiFi but will not support them all at the same time.
"If someone wants the fully flexible version that’s the Explorer RPU that essentially a software defined radio," said Richard Edgar, director of Communications Technology Marketing at Imagination. "When we start moving to IoT the power and size become more critical, so what we have done is moved to a more traditional chip architecture with hardwired PHY and MAC."
"We have designed the architecture for lower data rate solutions on the PHY, particularly for 802.11 for example," he said. "What you can do is optimize the modems that you put in, so if you don’t need a 64QAM modem you don’t need to put that in and that allows us to go to the lower data rate. We don’t see these going to much above 802.11n and that’s 72Mbit/s. This would typically be 24 to 36Mbit/s as a maximum but we have future looked at this for 11ah to make sure that the architecture is scaled to target the lower data rate."
"This is designed for lower power," said Chakra Parvathaneni, Senior Director of Business Development for Ensigma at Imagination. "Traditionally most WiFi chips were designed for performance with power gating but here the approach is quite different. By reducing the number of bits to process for example by not using 64QAM you don’t need 10 bits in the data path and that reduces the power. That’s quite different to how a normal modem would be designed."
"So Whisper can be configured to be full precision, or a subset which is good enough for most IoT yet still WiFi compliant. Then the power comes down by half and the area comes down by almost by half," he said.
The core is designed to use a partner MIPS processor for several of the MAC functions such as packet processing, encryption and queue management to reduce the power further. "The other thing we have done is to be able to use the MIPS processor as a mini host when you don’t need a complicated stack, especially with a headless device," said Edgar.
Imagination plans to roll out a series of Whisper RPU cores based around the architecture in Q4. "Many devices claiming to address IoT today are in fact re-purposed from other markets such as mobile or embedded, but don’t fully address the extreme low power and cost requirements that this market will demand," said Tony King-Smith, EVP of marketing at Imagination. "With new Ensigma ‘Whisper’ RPUs, customers can create a whole new generation of life-enhancing and efficiency-focused devices targeting markets as diverse as eHealth, energy, agriculture, security and many other areas."