Steven Leussink and René Kohlmann at Dialog Semiconductor explore wireless standards for home automation, energy, care and security devices and how DECT is enabling the creation of low-power, long-range, interoperable devices that operates on scalable and interference-free plug-and-play networks
Exceptional changes are underway in the home networking market and a wide range of home systems. Everything from thermostats, light switches, door locks and smoke detectors will become networked. Born from a collective desire to better control our environment and cut our consumption, this shift is widely predicted to bring significant market growth opportunities. In the UK, over £2.4 billion is expected to be spent on home energy management devices. However, such devices will have to work with existing home networks and interoperability between devices from different manufacturers is essential for commercial success.
According to IMS Research, over 600-million households worldwide have home networks installed with computers, media players, smart TV’s, printers, network-attached storage (NAS), Internet gateways and a growing number of accessories such as mice, headsets and keyboards. Like the home computing networks they join, which are standardised on WiFi, Ethernet and USB, these new home-automation, energy management, care and security (HAECS) networks must standardise to adopt an interoperable technology that gives whole home coverage and long battery life. Furthermore, this standard must be reliable, secure, scalable and simple to set up. This standard is Digital Enhanced Cordless Telecommunications (DECT).
DECT – An evolving technology with a strong history
Building upon a communication standard is imperative for wide-scale adoption. It ensures interoperability and increases consumer confidence, leading to a greater number of nodes per network, and creating value for both the end user and service aggregator.
Launched in 1987, DECT is an open ETSI standard for flexible digital radio access in cordless communication in residential, business and public environments. It employs several advanced techniques that enable highly efficient use of the radio spectrum. As a result, it delivers high voice quality, raw data rates up to 1 Mbps, secure communication and a very low risk of interference.
Over time this technology has evolved, with the CAT-iq (Cordless Advanced Technology –Internet and quality) enhancement of the DECT standard offering wideband voice quality and enabling the integration of cordless telephony and Internet services. It also allows DECT phones to be used for VoIP and other Internet based applications such as audio streaming as well as guaranteeing interoperability between vendors of gateway and handset devices. Supported by leading telecom operators, DECT technology and its CAT-iq incarnation have already been integrated into many home gateways and integrated access devices (IADs), which eliminate the need for separate modem, router and telephone base stations and enable triple play service offerings.
IMS Research predicts DECT / CAT-iq IADs (including cable, xDSL and fiber) will reach 35 percent worldwide penetration, leading to 25M devices by 2015. One reason that DECT has been overlooked for HAECS applications until now is the perception that its power consumption is too high for “fix-and-forget” nodes. However, the latest DECT products include an ultra-low energy mode, a new development ratified by the ETSI and known as ULE. This enables sensor-actuator nodes to operate autonomously for 5-10 years on a standard AAA battery pack. Fully compatible with both previous DECT and CAT-iq generations, ULE offers the same voice quality, reliability, secure communication and plug-and-play installation as the extensive installed base of systems using this technology.
With the CAT-iq and ULE developments, DECT is a perfect match with HAECS applications. Factor in its strong consumer acceptance, wide installed base and connectivity to the Internet and it is clear why DECT ULE ticks more of the boxes than any of the current networking options.
Range
Any home network technology must be capable of reliably transmitting over a distance of the size of a typical house. When discussing the range of an RF technology, it’s common to think in terms of the link budget (the path loss that can be bridged between transmitter and receiver). To cover most homes, a minimum link budget of around 115 dB is required. The link budgets for the various HAECS options depend on use case choices such as data rate, transmission frequency, transmitter power, etc. The table below shows the use case choices and best case link budgets for various technologies.
With its link budget of 123 dB, DECT clearly meets the range requirements for a home network and gives consumers the freedom to move around and install nodes anywhere in their homes even in non-ideal places like cellar or wall-sockets.
Interference, transmission reliability and data throughput
Interference between radio signals reduces the probability of information reaching its desired destination. Even if interference problems don’t prevent transmission, they significantly reduce the technology’s range and autonomy in the home. Many home networking technologies operate in the popular sub-GHz or 2.4 GHz Industry / Science / Medicine (ISM) band because it offers unrestricted geographic use. However, these bands are very crowded and are dominated by a large installed base of Wi-Fi, Bluetooth and a long string of proprietary devices.
This represents a big challenge to newcomers in the 2.4 GHz band, like Zigbee or RF4CE but also to the many proprietary sub GHz band solutions. Service providers using these bands will need to invest in extra installation support to ensure working systems and quality of service. For IAD manufacturers, the prospect of integrating multiple radio solutions operating in the same frequency band is not appealing. Co-existence measures exist, but deploying them successfully without a certification body remains very challenging.
DECT on the other hand operates in a 20 MHz wide band centred around 1.9 GHz. This band is licensed in over 100 countries worldwide, reducing interference issues from other sources. Uniquely, although this band is licensed and reserved there are no royalty fees. In addition, DECT’s proven Dynamic Channel Selection / Allocation (DCS / DCA) capability ensures each transmission uses the best available radio channel. As a result, a very large number of DECT systems can coexist in the same band sustaining high-quality and robust communication.
Interoperability
The HAECS market is a very fragmented one, with many individual players each supporting few elements of the HAECS residential network. Interoperability is essential to reach critical mass and also to offer value to the consumer.
The DECT standard supports Generic Access Profile (GAP) to guarantee interoperability between manufacturers of base stations and handsets. This has evolved with CAT-iq to support further interoperability, such as wideband codec negotiation. To help maintain this key benefit, the ULE alliance, (http://www.ulealliance.org/) an interest group of service providers, manufacturers, and chip vendors, hold interoperability test events for ULE devices. These activities safeguard the integration of ULE devices into legacy DECT systems and also guarantee interoperability between manufacturers of ULE devices.
Cost
Zigbee, Bluetooth and DECT all have similar hardware and software requirements. For example, the Zigbee software stack is around 100 Kbytes while DECT stacks range from 60-80 Kbytes depending on functionality – so memory costs are similar for both technologies. This means that the maturity of the technology and the volume of manufacturing are the main price differentiators. The 300 million DECT chips sold each year represent a healthy multi-vendor market guaranteeing low component pricing and wide availability.
Today’s single-chip DECT SoCs are priced well below the ZigBee SoCs $2-3 range, and often feature a wide range of HW & SW resources such as voice coding and data converters to differentiate applications. Overall sharing the DECT functionality can reduce system costs for the consumer further, this includes existing IADs too.
Voice and security
Although voice applications are not directly linked to HAECS segment, there are several security and home-care applications where voice links are paramount. DECT was originally designed for cordless telephony, so naturally offers high-quality voice links both inside and outside the home. DECT nowadays supports AES-128 encrypted links, including authentication algorithms and has a proven track record with respect to its link integrity.
ULE maintains that same high voice quality as well as the security mechanisms for voice transmissions used in the millions of installed DECT systems, offering HAECS networks that are as robust against eavesdropping as today’s cordless phones.
Ease of installation, configuration and maintenance
ULE is as easy to install, configure and run as its ancestor the cordless phone. Automatic frequency planning based on a distributed algorithm (dynamic channel allocation) executed by all devices, allows all sensors/actuators to access the complete DECT spectrum simplifying the configuration compared to other solutions. Furthermore, updating firmware over the air (via the ETSI DECT standard Software Upgrade Over The Air (SUOTA)) makes ULE networks future proof and gives service providers further leverage to deploy new products within existing configurations.
Steven Leussink, Senior System Architect at Dialog Semiconductor and René Kohlmann, Senior Director Low energy Wireless and VoIP Business Development at Dialog Semiconductor
Dialog Semiconductor
