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The WiFi community is waging a technology and PR battle to make its technology as ubiquitous in connected ‘things’ as it is in PCs and smartphones. It scores in many areas, notably user acceptance and ease of use, but for battery-fuelled devices, it loses out to Bluetooth Low Energy (BLE) and others on power consumption.
Chip vendors such as Redpine, Texas Instruments and others are pushing down the power ratings, but China’s Rockchip claims to have outdone them all with its RKi6000 system-on-chip, unveiled at last week’s Computex show in Taiwan. This claims to drive WiFi power consumption down close to BLE levels, with 20mA Rx/Tx power and stunning energy efficiency of 6nJ (nanojoules) per bit. These figures, if they translate into real world performance, compare with 59mA for the next best low power WiFi performer (according to Anandtech’s comparisons), the TI CC3200, and 64mA for the Qualcomm QCA4004.
More importantly, they stack up against chips using the WPAN standards, which have traditionally beaten WiFi hands-down on power consumption. For instance, spec sheet comparisons show that TI’s CC2540 BLE chip and its CC2520 ZigBee offering claim Rx power of 19.6mA and 18.5mA respectively, with energy efficiency of 58.8nJ/bit and 222nJ/bit.
The Rockchip product, like other ultra-low power WiFi chips, achieves its ratings partly by reviving the legacy 802.11b standard, which runs at a peak of 11Mbps, rather than the current WiFi generation’s gigabit-plus speeds. However, most connected devices do not require high data rates, and 11Mbps is far faster than BLE, ZigBee or Thread manage.
For categories like wearables, industrial automation and home appliances (where those are not mains-based), WiFi has the advantage of simplicity, both for the end user and the installer. For the latter, it uses connections supported in standard infrastructure. For the former, connecting new gadgets is simpler than Bluetooth pairing and there are more options, such as connecting multiple in-car devices over the wide interface, or creating ad hoc networks using WiFi Direct.
However, for some consumer applications, there are issues of introducing slow gadgets onto a network which also has higher performing WiFi devices in play, as 11b can slow down the entire system.
WiFi Alliance CEO Edgar Figueroa has made the IoT a centrepiece of his public pronouncements this year. He argues that the combination of high performance WiFi (for mains-powered items) and revived 802.11b can cover most of the range of IoT applications. A consumer study commissioned by the Alliance earlier this year found that more than half of respondents already had a “non-traditional” device (home automation product or wearable, mainly) connected by WiFi, and 91% said they would be more likely to purchase a smart device if it had WiFi.
Rockchip will be hoping to help turn survey results into real markets with its latest offering, and of course, there is the important presence of Intel lurking – the US firm has a hugely strategic alliance with Rockchip to customize and manufacture LTE SoCs in China, and will need to extend its mobile and embedded platforms to include more integrated WiFi in future.
As well as using 802.11b, Rockchip claims to be using other techniques to reduce power consumption. These include a patented technology to receive and transmit data continuously, plus the ability to connect to WiFi without waking up the main control processor. These are particularly useful in applications which need to remain online but have long standby times (WiFi is actually highly efficient when transmitting, but falls down, in power consumption terms, when it is in standby).
Rockchip also boasts Adaptive Dynamic Power Control Technology – this adjusts power configuration automatically according to the working mode and the application’s requirements for data rate and QoS. All these claims can be tested from the third quarter of this year, when the RKi6000 starts sampling.