The Future of Low-Power IoT

In our previous article, “Choosing the Right Wireless Communication Protocol”, we created a performance chart to compare the different communication protocols across three dimensions: data rate, power consumption and range. Let’s add InnoPhase IoT’s low-power WiFi to the chart and see how it compares to these existing solutions:

The Talaria TWO module features an 802.11 b/g/n WiFi modem and as such takes advantage of all the features of the technology. As you can see in the chart above, this means it has a higher data rate (of up to 65Mbps) and longer range than other standards such as Bluetooth, Zigbee or Z-Wave.

Furthermore, with WiFi routers present in almost any household and office space these days, the Talaria TWO module can make use of readily available infrastructure and does not need specialized gateways (aka extra investments). As a result, both deployment time and cost are reduced.

When it comes to power consumption while transmitting data, the existing solutions on the market, tend to have an advantage over WiFi. Bluetooth modules consume 50mA on average, for example, ZigBee about 75mA, and Z-Wave about 23mA. WiFi, on the other hand, consumes about 150mA. Talaria TWO module, however, can compete with the non-WiFi standards thanks to its ultra-low power consumption and an arsenal of power saving tools.

In the next section we will look at how the Talaria TWO compares to other WiFi modules and how it can revolutionize the battery powered IoT industry.

The Talaria TWO module features data rates and communication ranges that are typically expected from a WiFi module. As mentioned already, its selling point, however, is the extremely low power consumption.

To compare InnoPhase IoT’s technology with other low-power WiFi technologies, we’ve prepared another chart—one that synthetizes laboratory tests on a real-life application: smart locks.

Smart locks are a great option since the WiFi portion of the application can represent up to 75% of the total system consumption, and may only operate for 6 months on 4 AA batteries. In order to make this comparison work, we performed three measurements to evaluate the consumption of the application:
●        WiFi Idle Connected - application is IDLE, but maintaining connection to the AP
●        WiFi Message Rx - receive open/close messages from the cloud
●        WiFi Message Tx - post the status of the lock to the cloud

Assuming the device sends and receives an average of 10 messages a day and estimating that each message takes 100 ms to transmit or receive, we can calculate that the device spends a total of 86,398 seconds in Idle Connected. The numbers suggest that for an application like this, the Tx and Rx power consumption is negligible compared to the Idle state consumption. As a result, it is very important that the module be able to minimize the power it draws in the Idle Connected state. Please see Table 1 below.

The WiFi standard also provides two mechanisms for saving power:
1.        WiFi Multimedia (WMM) Power Save: this mechanism allows the access point (AP) to buffer downlink frames, allowing the associated devices to sleep between packets. Thus, depending on the application and its tolerance to delay, the power saved can be considerable.
2.        Delivery Traffic Indication Message (DTIM) Intervals: WiFi access points send out a beacon every 100 ms. The standard allows the AP to only send broadcast or multicast data every ‘n’ beacons, therefore enabling the client to sleep through multiple beacons. The power saving on the module comes from the fact that it spends most of its time idling in sleep, waking up regularly for the beacon frames. The module wakes up every n x 100ms and then goes back to sleep. Depending on the application and how critical the latency is, the power consumption reduction when idling can be dramatic.

At the same time, another way of reducing power consumption is to clock the module at a lower frequency. Reducing the clock proportionally reduces the power consumption. While this power optimization is not as significant as the previously mentioned options, it is still employed in extreme low power applications at the expense of performance.

Having a power saver mode that is lower than its competitors, the Talaria TWO module has the best overall power consumption. That translates into a lower consumption per day of operation.

What makes things more interesting is the fact that the Talaria TWO and Competitor 1 both offer the ability to increase the DTIM interval. This means that instead of waking up for each beacon frame (every 100ms) it instead wakes up every ‘n’ beacons. The power consumption is reduced at the cost of latency.

As illustrated in Table 2, by increasing the latency of the application to ~1sec, the power consumption was reduced almost tenfold, proving that for particular IoT battery-based applications Talaria TWO is a viable solution.

The benefits for the end user are enormous. The Talaria TWO module offers about 4X the battery lifetime of existing Smart Lock products, increasing usability to about 2 years. As can be seen in Table 2, Talaria TWO based solutions would last 59% longer than the closest competitor.

With the continuous evolution of the IoT industry, there has been an increase in demand for battery powered IoT devices. Obviously, in order to be viable, these devices need to run longer on a single charge. The biggest challenge the IoT industry faces right now is the fact that the WiFi communication module consumes the majority of the power in the system.

As shown by our comparison, with its lower power consumption both in IDLE and in Rx/Tx, the Talaria TWO consumed less power than the competitors we researched. However, one of the most important features is its ability to change the DTIM interval. By setting the DTIM to 10 we increased the latency of our lock’s response to one second, with power consumption reduced almost ten-fold. This makes Talaria TWO module very attractive for IoT applications that are WiFi enabled but spend a lot of time idling.