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DSP - DECT-ULE

2013-05-06  Semiconductor ICs   DSP GROUP

The new Standard for Home and Building Automation!

DECT - The firm foundation
The DECT (Digital Enhanced Cordless Telecommunications) Standard was developed as a standard for cordless telephones, and is widely applied in Europe and other countries worldwide. While DECT was originally only intended for the transmission of speech, with CAT-iq (Cordless Advanced Technology – internet und quality) an extension has been created which also supports the transmission of data, and therefore allows for Internet integration.

DECT has its own protected frequency band reserved in Europe, of 1880–1900MHz (in the USA, Japan, and many other countries frequency bands are used which deviate slightly from this). DECT offers space for 10 carrier frequencies spaced at intervals of 1728MHz. Each band is modulated with a physical bit rate of 1152Mbps in the GFSK process, and supports access to 12 duplex channels in the time division multiplex process.

Thanks to the reservation of its own protected frequency band, by contrast with other standards such as ZigBee, Bluetooth, and WLAN, all of which have to share an open 2,4 GHz frequency band, DECT holds a special position. Interference and the associated transmission distortions can therefore be excluded with a DECT network.

DECT - Ultra Low Energy
What could be more natural than to want to make use of the excellent physical transmission properties of DECT for the configuration and controlling of sensors and actuators in the sector of home and building automation and security. Against this background, a ULE (Ultra Low Energy) Alliance has been formed by the DECT Forum, in order to forge ahead with the further development of the existing DECT Standard. On the one hand, compatibility is to be maintained with existing DECT networks, while on the other the new Standard has been designed to be entirely suitable for the special technical requirements in these application areas.

With DECT-ULE a new standard has been created which has taken over the physical layer specification of DECT, but has undergone a number of changes on the MAC level, which make for substantially better performance with regard to low power and reaction time. To achieve this, the performance time for time and frequency synchronizations has been drastically cut when a connection is being setup. This means that the MAC layer can, for example, set up a connection, send check and/or control data, and shut down the connection again, all within 50ms. In addition, the protocol has been functionally extended by a Sleep Mode, which allows for a rapid and efficient change between the sleep periods and radio transmissions. A smoke alarm, for example, which must send a “Stay Alive“ message to the central unit every 7 minutes, if fitted with a CR123 battery (1500mAh), can be operated for about 18 years.

ULE can also provide the encoding of data and its authentication on the basis of the AES (Advanced Encryption Standard).

Market researchers see the greatest advantage, however, in the compatibility with the traditional DECT Standard, which has proved its worth millions of times over, since, for the system installation of DECT-ULE products, all that is required is a firmware update of the existing base station, enabling the potential for up to 2000 DECT-ULE participants to be configured and administered.

This means that millions of installed base stations all over the world have the best possible preconditions for implementing a DECT-ULE network rapidly and cost-effectively. This may be one of the most important reasons as to why IMS Research foresees a massive rise in the market share in the years ahead. Plans are for more than 50 million DECT-ULE products to be sold annually, as from 2015. 

Advantages of DECT-ULE at a glance
=> A protected frequency band (1.9 GHz) guarantees that DECT-ULE products installed today will still be working reliably many years from now. Technologies which operate on free frequency bands such as 2.4 GHz or 868 MHz cannot make such a guarantee. If new equipment units using the free frequency bands are installed in the house, they may interfere with existing sensors and actuators. Not so in the protected DECT band!
=> Long range (at least 30 meters in buildings and 300 meters in the open air), combined with high security thanks to the very latest encoding technologies and signatures.
=> Thanks to the star topology, installation is extremely easy, exactly as with DECT.
=> Very short latency, which makes real-time communication possible.
=> Very low current consumption
=> Integration in home gateways, which makes for easy access to the Internet. In Germany alone DECT is to be found in more than 5 million home gateways.
=> Approx. 200 million DECT chips are already being sold every year. These synergy effects can be used to allow DECT-ULE products to be offered at a very attractive price.

Applications
Its special properties make DECT-ULE the ideal radio standard for sensors and actuators, such as for use in smoke, movement, and temperature detectors, or in ventilation, air conditioning, and heating systems. As well as these applications, DECT-ULE also allows many other applications to be addressed, and makes different business models possible. These range from closed systems for the security services, solutions marketed and installed by electricians, and components which are available from retail outlets, all of which can be integrated seamlessly into existing infrastructures.

Here are some of the most important applications at a glance:

Home and building automation
• Intelligent plugs
• Lighting controls and dimmers                                  
• Roller blinds and window controls
• Control systems for air-conditioning, ventilation, and heating

Security
• Movement detectors
• Glass breakage detection
• Window and door monitoring
• Access control
• Smoke detectors
• Water and gas detectors

Remote Healthcare
• Patient monitoring
• Healthcare monitoring

Energy management
• Metering
• Remote (Cloud) Energy Management

The DECT-ULE Network

The Concentrator:
For setting up a home network with DECT-ULE, a base station is required, which represents the concentrator for the various different nodes in the system (sensors and actuators). In the simplest case, the concentrator can be a home gateway with an integrated DECT chip, which either already supports ULE or can be upgraded to ULE by means of a software update. It is anticipated that in the near future more and more home gateways will be made ULE-capable by a software update. Another option is to use a dedicated concentrator, which either possesses local management functions or is connected to the Internet by Wifi, telephone line, or Ethernet. Also available are USB dongles, which have implemented a DECT-ULE concentrator. In principle it is also possible for regular DECT telephones to be extended by DECT-ULE, and for both functions to be integrated in one base station.

For all the application situations referred to here by way of example, the DSP Group can offer the appropriate System on Chip (SoC) solutions. These range from simple SoCs with real-time operating systems through to complex solutions based on Linux and, in addition to DECT and DECT-ULE function performance, also contain a complete telephone solution with up to 8 channels for VoIP.

The lower end is covered by the DCX81 family, which can function as concentrator for DECT-ULE units, and at the same time offers the complete speech function capacity (GAP/CAT-iq 1.0/2.0/2.1). Other features are, for example, an integrated USB interface, line interface, UART, SPI and 2x AD/DA converters. The DCX81 is an extremely cost-optimized chip, the code of which is formed from an external Quad SPI Flash, and therefore also offers software update function performance. The use of the DCX81 millions of times over in regular DECT telephones offers the customer an extremely stable and market-tested and proven platform, covering a wide range of applications.

The Network Nodes:
For sensors and actuators the DSP Group offers, with the DHX91, a chip which is optimized when it comes to current-saving applications and fast reaction times. As well as the regular DECT and DECT ULE functions which have been tested in a range of different interoperability events with other DECT ULE manufacturers, a sensor/actuator (SA) facilities unit has been integrated. This special function allows for the integration of sensor and actuator technology applications on one chip, without the need for an additional MCU.

Some of the special functions of the SA unit can be described here, by way of examples. All these functions are also available to users in sleep mode. In this mode the SA unit can carry out measurements and control functions autonomously, without processor intervention, with very low current consumption, and wake up the processor within 10ms if an event requires this (Diagram 1).

Sensor Conditioning Module:
The Sensor Conditioning Module (SCM) is an analog configurable circuit which is integrated into the SA, and which, with two amplifiers and two comparators, can carry out the most widely differing sensor applications. The SCM is optimized for extremely low current consumption

(~ 3uA).  Here is a representation of the complete SCM with all its components (Diagram 2):

An example application of the SCM as a passive infrared sensor (PIR)
A PIR sensor reacts to temperature changes by making use of pyroelectricity on its receiver surface. If an object moves in the area being monitored, the heat difference between the object and its surroundings is converted into voltage.

The two amplifiers wired in series, AMP1 and AMP2, have a filtering and amplifying function. The output signal is measured by two comparators against two reference voltages, which define the threshold value. The frequency range for movement recognition moves between 0.1 Hz to 10 Hz, and the signal amplification lies between 60dB and 70dB (Diagram 3).

An example of an application for a smoke alarm:
An LED and a photodiode in the interior of a smoke alarm convert light into voltage. Since there is no direct line of sight between the LED and the photodiode, under normal circumstances the photodiode will not produce any voltage. If smoke penetrates into the smoke alarm, the light from the LED is reflected onto the photodiode, and a voltage is produced (Diagram 4).

Detection takes place in two phases:
• In the first phase the LED is off, and therefore AMP1_P, ANA_IN1 and AMP1_OUT are short-circuited. This causes C1 and C2 to discharge.
• In the second phase the LED is switched on briefly. If any smoke present leads to reflections, then, in the proportion of the two capacitors C1 and C2, the input voltage is amplified by AMP1. The threshold value for recognition is set by the voltage VREF1.

But, in addition to the SCM, the SA unit has other functions to offer. For example, the counter units can be used to count pulses, and, when reaching a pre-configured number of events, it wakes up the system. An important point to note is the integrated “Debounce” module, which only forwards “genuine” events to the counter. In a similar way, periodic events can also be used to wake up the system. It is even possible for events over a defined period to be counted, and for the system only to be woken up when a defined number of events have taken place in the selected time period. PWN signals can also be generated, which are even available in the sleep mode (Diagram 5).

The examples described here represent only a small selection from the possibilities which the SA unit has to offer. All the functions can be varied and configured in wide ranges, which allows for an almost limitless number of applications to be realized.

Software:
DSP Group sees itself as a system provider, and not simply as a chip manufacturer. All the integrated circuits are offered with an extensive software package. These contain the operating system (embedded or Linux), DECT Stack, DECT-ULE Stack, audio functions such as Codecs and echo suppressors, as well as extensive example applications.

About DSP Group

With a market share of 70%, the DSP Group is the market leader in the DECT sector, and the leading the standardization for DECT-ULE in the DECT Forum, the ULE Alliance, and ETSI. Applications for home automation have been independently developed by DSP Group, and continue further development towards cost reduction and lower power. DSP Group provides complete solutions includiong protocol software.  DECT-ULE reference implementations for different ranges of applications in home automation are available, and can be adapted by the customer. With partners from industry, complex solutions can be provided as well. As a leading semiconductor manufacturer, DSP Group offers a broad product portfolio covering IC’s, Protocol Stack and applications, and HW and SW reference designs as a “one-stop shop“.

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Diagram 1: Block circuit diagram: DHX91 (the SA unit is formed from the blocks surrounded by the red frame)
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Diagram 2: Block circuit diagram of the SCM: Sensor Conditioning Module
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Diagram 3: Example of a circuit: PIR (Passive Infrared Sensor)
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Diagram 4: Example of a circuit: Smoke alarm
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Diagram 5: Block circuit diagram: Counter Compare Unit
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Diagram 5: Block circuit diagram: Counter Compare Unit

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