Digital Enhanced Cordless Telecommunications usually known by the acronym DECT is a standard primarily used for cordless phone systems. Since 1992, it is used primarily in home and small office systems, but also in many PBX systems for medium and large businesses. It is available in over 110 countries worldwide and operating in some 600 million installations. Its medium access scheme is based on a combination of time and of frequency multiple access (TDMA and FDMA) as well as time division duplex (TDD) in an allocated frequency spectrum without coexistence issues, which allows very good voice quality. It is well known for its good range capabilities based on its RF characteristics.
In 2011, the development of a low power variant (DECT ULE, ultra-low energy) was initiated to take advantage of the existing data channels for DECT to address markets such as home automation, security and climate control. The low energy variant enables battery powered mobile devices in the home to be connected through a single control unit. Recently, IETF also developed a standard to describe how IPv6 is transported over DECT ULE.
However, with the advent of Internet of Things (IoT) applications, DECT requires an evolution to provide the relevant features in a data driven, packet oriented way of communication.. There are mainly four features, which need enhancements and which shall be addressed within this project. These features will give the project partners a unique winning margin against the competitors without compromising the interoperability of the standard:
• Already with the ULE standard, only the mobile devices are energy efficient and can operate for several months or even years from a single battery using extensive sleeping (low power) times in a synchronous or in an asynchronous mode. However, all receiver stations, be it base stations or repeaters, need to be always-on and therefore are always mains-powered. Currently, there exists an eco- or non-emission-mode (NEMO), where the base station stops the pilot signals when there is no call. This mode is mainly targeted towards the reduction of RF radiation and has only minor impact on the required energy budget.
• Also, sleeping modes are not well supported in the current products, i.e. from DSP Group. Even if the given DHX91 DECT Ultra Low Energy (ULE) chipset was introduced quite recently in 2013 and even if it boasts a current consumption below 1 µA in hibernation mode, it is not well suited for Wake-On-Radio-(WOR)-operation, which is mainly due to the legacy partitioning of the two chip solution. Today in hibernation mode, only the analog die is active and the digital IC is switched off completely. However, the digital die contains the synchronization and the burst mode processor (BMP), which would be relevant to synchronize and to receive the DECT dummy bearer and paging signals.
Currently the ICs can be switched off only completely. No partial hibernation modes are supported, which would be required to support real ULE applications.
Besides, also the peak current consumption is significantly too high, which makes the design of a ultra-low energy system with long-lifetime batteries (with high internal resistance) quite complicated.
• The integration of Internet Protocol is currently limited to star networks only. Amongst other reasons, this is also due to missing availability of battery-powered receivers, which could be used as routers for mesh-based networking. This would overcome the range limitations of conventional DECT applications, which are good enough for single household topologies, but currently cannot support larger installations, which might be required for integrated IoT applications.
• Also, there are no application profiles, which include the meshed IP-over-ULE functionality together with the WOR features.
Therefore, the planned project focuses on the development of ultra-low energy receivers, using some kind of wake-on-radio (WOR) receivers. With this extension, it also would be possible to extend the IPv6-mode to mesh networking and to enhanced application profiles.