Mar 28, 2014
Panasonic Develops Industry-First*1 Multi-Mode Wireless Communication Technology for Sensor Networks
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The new M2M communication technology enables devices to be connected wirelessly to a network regardless of operation frequencies and wireless standards while supporting up to three different wireless modes.
Osaka, Japan - Panasonic Corporation today announced that it has developed a new wireless communication technology for M2M (Machine-to-Machine) sensor networks[1], where devices communicate with each other in an autonomous way without human intervention.
This technology is based on a single chip of LSI that can simultaneously detect multiple wireless communication standards, which differ from one country to another or in the target applications. Multiple communication modes are integrated by sharing the software of same functions and reducing the amount of signal processing in microcomputer. As a result, engineers can design and develop wireless modules that are small but can operate for an extended period of time. The newly-developed technology makes it easier to connect disparate devices and helps accelerate the spread of wireless sensor networks[2], contributing to achieving a society with a safe, secure, convenient and comfortable living environment.
Currently, different modes of wireless communication are used in different countries and regions for connecting devices to sensor networks. The new multi-mode wireless communication technology integrates multiple receiver circuits required for each individual wireless mode into a single one, enabling devices to be connected easily and stably each other regardless of operation frequencies and wireless standards. With a smaller area, the same as the receiving part of conventional single-mode wireless chip, multi-mode wireless LSI can support up to three different wireless modes at a time. The new LSI helps create a small and power-saving wireless module that will continue to operate for around 20 years on the battery.*2
The new technology has the following features.
- Ability to be used in various devices and/or machines, independent of wireless standards and operation frequencies.
- Reduction in the receiver power consumption of the whole module by 55% (compared with Panasonic's existing products) that enables 20-year battery operation*2.
- A small multi-mode wireless LSI having the same size as a conventional single-mode one, enabling downsizing of wireless modules.
This multi-mode wireless communication technology includes the following technologies.
- Multi-mode technology that reduces both power consumption and memory capacity requirement based on frequency detection by hardware and unified control by common software for multiple wireless operation modes.
- Receiver power reducing technology that enables 20-year battery operation while supporting multiple wireless modes, which is achieved by intelligently controlling voltage supplies and generating high rate internal clocks from low rate clocks to minimize circuit current.
- Wireless LSI miniaturizing technology which reduces the size of coils in oscillator circuits and eliminates filters used in analog-to-digital converters.
Panasonic holds 26 Japanese patents and 19 overseas patents (including pending) related to this technology.
Development of this technology was supported in part by the "Research and Development for Expansion of Radio Spectrum Resources" program of The Ministry of Internal Affairs and Communications, Japan. A field test starts today at The ICT Incubation Laboratory in Research Center for Advanced Science and Technology, the University of Tokyo.
Notes:
*1: As of March 28, 2014, according to Panasonic data.
*2: When used in a smart meter or HEMS child device and receives and transmits information every 30 seconds using a 1200mAh industrial-use lithium-ion battery.
More on the Technology
1. Multi-mode technology that reduces both power consumption and memory capacity requirement based on frequency detection by hardware and unified control by common software for multiple wireless operation modes.
In wireless sensor networks, FSK[3] modulation is normally used. Conventional FSK demodulators, such as Arctan demodulators[4], detect the operation frequency by monitoring received signals in time domain and then demodulate based on the detected frequency. In order to receive multi-mode signals of different frequencies or based on different standards, a receiver needs to eliminate noise in accordance with bandwidth of each mode, thus a dedicated wireless LSI is required for each wireless mode.
Panasonic developed technologies to detect all frequency components simultaneously within multiple modes by employing Short-time DFT[5], which can also determine the data rate with respect to each mode by hardware and then demodulates by achieving an optimum control to the data rate. In addition, instead of switching among multiple software control modules each corresponding to one transfer rate, a unified software module for all modes is newly implemented. These technologies enable a single LSI to support multiple wireless modes.
2. Receiver power reducing technology that enables 20-year battery operation while supporting multiple wireless modes, which is achieved by intelligently controlling voltage supplies to minimize circuit current, and by generating high rate internal clocks from low rate clocks.
In conventional wireless receivers, a constant voltage is used for every circuit to guarantee a whole stable operation regardless of operation frequencies or temperatures. However, to maintain such a constant voltage a strong enough supply voltage has to be supplied all the time. This causes waste when a lower power supply is sufficient.
Panasonic developed an intelligent power supply technology which controls a voltage dynamically for a circuit according to its frequency, temperature and process variations. The dynamic control minimizes current consumption of a circuit. As an example, for the high frequency oscillator circuit which consumes the most of current, it reduces by 70% compared to our previous design.
Also a high SNR[6] is required for an analog-to-digital converter (ADC)[7] to process received signals. Conventionally this is realized by a high rate sampling circuit which picks out pulses from a 100MHz clock. But such a circuit consumes much power.
Panasonic developed a technology to generate high rate sampling pulses from a low rate clock by using its rising edge effectively. Furthermore, Panasonic developed a SAR-ADC[8] which can realize a high SNR equivalent to that generated by a conventional ΔΣ ADC[9], but with lower power consumption. Compared to our previous design it has been reduced by 60%.
3. Wireless LSI miniaturizing technology which reduces the size of coils in oscillator circuits and eliminates filters used in analog-to-digital converters.
Conventional oscillator circuits require large coils to minimize the increase of circuit current due to transistor performance variations. The newly developed intelligent power supply control technology compensates for the transistor variations and enables use of twice the oscillation frequency. This makes a small-sized oscillator circuit to be realized, which has a smaller coil and a divide-by-two circuit both with low current consumption. In addition, instead of conventional analog-to-digital converters of the ΔΣ ADC that have been necessary to achieve required performance, a SAR-ADC is adopted in the new technology which makes a compact filter-less analog-to-digital converter possible.
Technical Terms:
- [1] M2M (Machine to Machine) sensor network
- A network where devices in it communicate with each other without human intervention. The devices may send information, make control and provide services to each other automatically.
- [2] Wireless sensor network
- A wireless system where various sensor data are transmitted through wireless communications. The sensor data may include temperature, humidity, brightness and power consumption at home.
- [3] FSK
- Frequency Shift Keying. The most common protocol of digital modulation.
- [4] Arctan demodulation
- One scheme of FSK demodulation, which detects a phase shift by calculating the arctangent of a signal. "Arctan" is abbreviated expression of arctangent.
- [5] Short-time DFT
- Short-time Discrete Fourier Transform, which can be used for a simple FSK demodulation.
- [6] SNR
- Signal to Noise Ratio, which represents the ratio of a signal power to a noise power.
- [7] ADC
- Analog to Digital Converter, a circuit that converts analog signals to digital signals.
- [8] SAR-ADC
- Successive Approximation Register - Analog to Digital Converter, an ADC which converts an incoming signal one bit by one bit through using a binary search algorithm.
- [9] ΔΣ ADC
- Delta-Sigma Analog to Digital Converter, which integrates the difference between consecutive data and detects its error precisely to realize precise ADC.
A prototype module employing Panasonic's new multi-mode wireless communication technology
Panasonic Corporation is a worldwide leader in the development and engineering of electronic technologies and solutions for customers in residential, non-residential, mobility and personal applications. Since its founding in 1918, the company has expanded globally and now operates over 500 consolidated companies worldwide, recording consolidated net sales of 7.30 trillion yen for the year ended March 31, 2013. Committed to pursuing new value through innovation across divisional lines, the company strives to create a better life and a better world for its customers. For more information about Panasonic, please visit the company's website at http://panasonic.net/.
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