Ensigma Whisper Wi-Fi power consumption

Wi-Fi today is a ubiquitous connectivity technology and is one of the pillars one which Internet of Things (IoT) connectivity rests. The problem, however, is that Wi-Fi has traditionally been a power hungry technology. Imagination’s Ensigma Whisper low-power Wi-Fi IP has been architected from the ground-up to provide an ultra-low power solution that’s ideal for IoT and other battery operated devices. In this post, we share some actual power measurements performed on a customer chip that uses the Whisper Wi-Fi core. Measuring the power consumption enables us to determine the battery life of the end product.

Test setup description

Our measurements were carried out using a Techtronix TDS 784D Oscilloscope and Techtronix TCP202 current probe. For low-current measurements, we used a digital multimeter (Metrix MX56).  The current measurements for connected standby mode were conducted by connecting the Device under Test (DUT) to a TP-Link AC750 router. All current measurements were carried out on Channel 1 for channel bandwidth of 20MHz in Mixed Mode (802.11 b/g/n) with no encryption enabled. The set-up measures both active (transmit and receive) and inactive (sleep mode) power consumption.

Figure 1: Test setup and measuring instruments

Figure 1: Test setup and measuring instruments

Power domains

The Whisper Radio Processing Unit (RPU) has multiple power domains for each of the functional blocks. It also has a sleep controller, which provides power to each power domain at the latest possible time and cuts off power at the earliest possible time. The power domains are comprised of the following power rails: 3.3V for the power amplifier (PA), 1.6V for the RF and 1.1V digital blocks. We carried out the power measurements for each of the power domains.

Figure 2: Power domains in Whisper Radio Processing Unit (RPU)

Figure 2: Power domains in Whisper Radio Processing Unit (RPU)

Figure 3: Sleep controller in Whisper Radio Processing Unit (RPU)Figure 3: Sleep controller in Whisper Radio Processing Unit (RPU)

Power Amplifier (PA) power consumption at 3.3V

The power consumption of the PA is measured both at the highest output power (lowest data rate) and at lowest output power (higher data rate) as depicted in the below photos.  As you can see, the current measured is 98mA at a transmit output power of 10.5dBm.  Correspondingly, the current measured at 17.5dBm is 136mA. The PA is the predominant source of power consumption in the transmit path, and the Whisper architecture focuses on power reduction for each component in the transmit chain including the PA.

Figure 4: Transmission of an 802.11n MCS7 signal @ 10.5 dBmFigure 4: Transmission of an 802.11n MCS7 signal @ 10.5 dBm

 

Figure 5: Transmission of an 802.11b 1 Mbps signal @ 17.5 dBmFigure 5: Transmission of an 802.11b 1 Mbps signal @ 17.5 dBm

RF Power Consumption at 1.8V

The RF power consumption is measured for both the transmit and receive paths and is depicted in the below photos. As you can see, the current measured is 29mA in the receive path and 59mA in the transmit path. The receive power consumption is a key parameter for the connected standby power consumption, and the Whisper core’s power consumption in the receive path has been specifically optimized for this use case.

Figure 6: Reception of an 802.11n MCS7 signalFigure 6: Reception of an 802.11n MCS7 signal

Figure 7: Transmission of an 802.11n MCS7 signalFigure 7: Transmission of an 802.11n MCS7 signal

Power consumption at 1.1V

The digital power consumption is measured for both the transmit and receive path and is depicted in the below photos. In this mode, the receive current is 16mA and the transmit current is 13mA. The digital power consumption is optimised through a combination of innovative algorithms and power gating mechanisms in the baseband.

Figure 8: Reception and transmission of an 802.11n MCS7 signal

Summary of current consumption

A key power consumption metric for IoT devices is the receive power consumption. As can be seen in the table below, the Whisper core’s receive power consumption in active mode is 64mW. Based on the extensive data mining conducted on similarly featured devices, it is fair to state that the power consumption of Whisper’s receive power is far better – by 50% in most cases.

Table 1: Summary of power consumption

Application energy consumption calculation example:

Consider an intermittently connected device such as the smoke alarm sensor. The devices awaken at regular intervals to communicate with the server (access point). There are two predominant states: a static power consumption state (sleep state) and an active power consumption state (during which the various sub-blocks of the RF transceiver are powered and the device receives data).

This connected standby state of this scenario is captured in the measurement:

power consumption = 29mA*33ms + 0.5mA*(304-33)ms = 1.1mC

During a one-hour interval, if the device wakes up at two-minute intervals (30 times in one hour), the total power consumption = 1.1 *30 = 33mAs.

For a battery capacity of 1000mAH, the lifetime = (1000 mAh/33(mAs))/24 hours = 12.45 years.

Table 1: Summary of power consumption

Conclusion

As our tests prove, Ensigma Whisper low-power Wi-Fi IP consumes roughly half the power consumption of similarly featured devices, offering a compelling solution for IoT applications where low cost, low power consumption and robust performance are key drivers.

Interested in our unique Ensigma communications technology? Then subscribe to our blog and follow us on Twitter @ImaginationTech for more news on Imagination’s Ensigma wireless communications.

Search by Tag

Search for posts by tag.

Search by Author

Search for posts by one of our authors.

Featured posts
Popular posts

Blog Contact

If you have any enquiries regarding any of our blog posts, please contact:

United Kingdom

benny.har-even@imgtec.com
Tel: +44 (0)1923 260 511

Related blog articles

British Engineering Excellence Award

PowerVR Vision & AI design team collect another award

We’re delighted that the design team for our PowerVR Series2NX Neural Network Accelerator (NNA) has been honoured with a prestigious British Engineering Excellence Award (BEEA). The BEEAs were established in 2009 to demonstrate the high calibre of engineering design and innovation in the

Series8XT AR/VR Banner

Imagination Technologies: the ray tracing pioneers

After a period out of the spotlight, ray tracing technology has recently come back into focus, taking up a lot of column inches in the tech press. The primary reason is because graphics cards for the PC gaming market have

Amazon Fire Stick 4K pic

Amazon Lights up its Fire TV Stick 4K with PowerVR

Amazon, the internet shopping giant, announced earlier this week the latest version of its media streaming device, the Fire TV Stick 4K. First released in 2016, the Fire TV stick brings catch-up streaming services to any TV with an HDMI

Stay up-to-date with Imagination

Sign up to receive the latest news and product updates from Imagination straight to your inbox.

  • This field is for validation purposes and should be left unchanged.
>
Contact Us

Contact Us