It may not be as important as e = mc2, but for Digital Enhanced Cordless Telephony (DECT), the implications are potentially just as dramatic. As the technological universe migrates to both voice command and control and low-power Internet of Things (IoT) devices, the once European-centric cordless phone standard may be finding its way back into the global home after having been booted out by the rise of mobile phones.

This exploration of the future of DECT started with the question as to why Alexa’s Wi-Fi-based external call quality was so poor. This was quickly followed up by the questions: What if it were an emergency? And how could any Wi-Fi-based voice-enabled IoT device be trusted to operate effectively?

This raises questions for the whole field of home health monitoring and voice-based control, for both emergencies and casual, reliable, frustration-free use. The answer may lie with the addition of yet another wireless interface to the home particularly as voice-enabled devices and control become critical for the IoT.

The whole issue started rather innocuously: Using multiple Amazon Echo Dot 2s to make room-to-room intercom calls worked well over Wi-Fi. There were a few dropped syllables, but the conversations were fairly fluid. The problem arose when asking Alexa to make external calls: The connections were horrendous. Why?

It turns out that the Echo 2’s codecs are optimized to communicate with other Echo 2s over Wi-Fi, but not with the home router. In order to make reasonable quality external calls, it’s necessary to either sign up for a virtual VoIP PBX service skill or to purchase a $34 Amazon Echo Connect that connects any Alexa device to the home phone line for better-quality voice connections.

To be sure, Wi-Fi’s quality-of-service (QoS) enhancements have made it much better at giving voice priority over video or audio streaming where a few dropped packets are acceptable. However, each adaptation adds processing overhead, and not every Wi-Fi device is up to date with the latest standards. Also, Wi-Fi hardware was designed for high-speed data, and while it can be throttled back and use various sleep modes to lower power consumption, the hardware is relatively expensive.

However, DECT was specifically designed for high-quality voice at low power, not for high-speed data (though it can be used for data). In Europe, it operates in the 1,880- to 1,900-MHz band, while in the U.S., it is assigned to the slightly higher 1,920- to 1,930-MHz band to avoid interfering with public safety and government systems. All of the handsets connect back to a base station that connects to the phoneline.

Though still widely used in the enterprise, DECT lost ground in the home, squeezed between “good-enough” voice over Wi-Fi and mobile phones. Still, one of its salient features is its low latency of 10 ms, compared to 150 to 200 ms for Wi-Fi.

Given its low power and latency, among other features, it wasn’t surprising that in 2013, the ULE Alliance was formed with the goal of using a revised form of DECT to low-power, high-quality voice command and control and ensuring that IoT devices can communicate effectively and reliably. The move was prescient: Since then, voice control using Amazon’s Alexa and Google Home has taken off along with the IoT.

The target applications are home security, energy control, home automation, and medical and fitness wearables and emergency contact assurance. To address these markets, the Alliance’s changes to DECT mainly reside above the physical layer (PHY) and include: increasing the sleep time between beaconing the base station to save battery life; increasing security from 64-bit encryption to 128-bit AES; and the development of a star topology such that nodes connect directly to the base station, now called a concentrator. Communication to the outside and to other nodes all go through the concentrator.

A characteristic feature of DECT is range, and that has been maintained per the ETSI DECT specification. ULE devices have a range of 70 to 100 m indoors and >500 m outdoors. It still supports two-way voice in all forms as well as low-resolution video. Its data rate tops out at 500 Kbits/s.

The adjustments to the network layers are based around the ULE Alliance’s Home Area Network FUNctional (HAN FUN) protocol and allow it to support IPv6 (6LoWPAN). HAN FUN is a binary protocol and covers protocol definition, device definition, and device management. Like Zigbee and Z-Wave, HAN FUN is an object-oriented approach in that it can send commands such as having detected smoke. It resides on top of ULE, which is a transport-based protocol.

The adjustments to DECT by the ULE Alliance mean that a node can last five to 10 years on a standard AAA battery, depending on its usage model.

Where is DECT-based ULE now?

The ULE Alliance came to market in 2015 with support from chipmakers such as Dialog Semiconductor and DSP Group and device makers Gigaset and Panasonic, as well as with support from Deutsche Telecom. Since then, it has been incorporated into over 50 million DECT base stations, creating a large installed base ready to use ULE for low-power IoT devices and voice control.

In January of 2018, the ULE Alliance attended CES and gave EETimes a review of the architecture (Fig. 1) and the devices available at the time from its supporters (Fig. 2).

Fig. 1: A snapshot of the ULE Alliance architecture for IoT taken at CES 2018 shows how all nodes connect through the concentrator (ULE Gateway). While typical of a home automation network, a key differentiation is low-latency, low-power, two-way voice control. Credit: EE Times
Fig. 1: A snapshot of the ULE Alliance architecture for IoT taken at CES 2018 shows how all nodes connect through the concentrator (ULE Gateway). While typical of a home automation network, a key differentiation is low-latency, low-power, two-way voice control.
Credit: EE Times

Support for DECT and now ULE is strong in Europe. The Voice of IoT DECT and IoT Summit in early February attracted the operators Orange and Deutsche Telecom, as well as Sennheiser, Bosch, DSP Group, and Dialog Semiconductor, with much of the discussion focused on how to use ULE for the smart home.

In the U.S., operators such as Ooma are using ULE, and according to the Alliance, up to 50 million gateways are deployed to date. A key feature is that, because it’s not a PHY-layer enhancement, installed DECT base stations can be updated via software to support ULE.

Standing out in a sea of wireless options for IoT

In seeing what DECT and ULE can do for low-power IoT and voice command and control, it’s still awkward to introduce another wireless interface into the home. Yet few options provide the low latency and low power for voice.

For home health care, that’s becoming a critical feature. There are options to include a pendant that can be activated with a squeeze to establish voice communication to a landline to ensure even longer life versus preset pings to the concentrator. For home security, it can perform accurate voice analysis with no dropped packets and fast response times and no echo.

What started as a simple question as to why an Amazon Echo Dot 2 by itself isn’t up to critical voice communications and IoT links has evolved into an exploration of how an adaptation of an already established technology might well do the trick and possibly get a new lease on life — globally — as a result.

— Patrick Mannion is a freelance technology journalist, and former content director for EDN and EE Times.