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World's first Small-sized, Low-power “Smart Meter Radio Device” compliant with IEEE 802.15.4g/4e standards for Japan’s new 920 MHz band allocation

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April 5, 2012

The National Institute of Information and Communications Technology (NICT, President: Dr. Hideo Miyahara) has developed the world's first “smart meter radio device” compliant to the finalized IEEE 802.15.4g/4e standards in IEEE 802 committee. The developed radio device supports both PHY (newly defining 920 MHz band allocation in Japan) and MAC (finalizing low-energy protocols assuming several-year operation with only battery) specifications in the final drafts for those standards. The radio device also realized highly integrated MAC circuit, newly developed small-sized and low-power PHY circuit, and is equipped with flexible interface modules suitable for a variety of external meters and sensors. Furthermore, this radio device has obtained technical standards conformity certification for 920 MHz, which enables practical operation of the device in every region of Japan.

Background

Recently, reducing excessive energy consumption by controlling meters of electricity, gas and water in homes and buildings has been of great importance to environmentally-friendly technologies. NICT has conducted research and development on the smart meter system with radio communication technologies that effectively and surely realizes automatic and autonomous control, data reading and monitoring on each meter. Such NICT’s efforts have been reflected on standardization activities in IEEE 802 committee and been successfully adopted in IEEE 802.15.4g/4e drafts.

In Japan, “950 MHz band” allocation for RFID system was originally considered to be suitable for the allocation of smart meter utilities. However, MIC (Ministry of Internal affairs and Communications, Japan) officially announced “920 MHz band” allocation for smart meter usage in Jan. 2012 for the benefit of the international cooperation and competitiveness. Accordingly, NICT, domestic users and manufacturer companies have submitted a unified proposal for clear and effective 920 MHz utilization to IEEE 802.15.4g/4e task groups. As a result, those task groups have finalized IEEE 802.15.4g/4e drafts (to be finalized as standards in Mar. 2012) defining such “920 MHz band” allocation. Although significance of standardization and realization of the smart meter system is confirmed with the establishment of "Wi-SUN alliance" in Jan. 2012, any radio device compliant to such finalized IEEE 802.15.4g/4e standards has not been developed yet.

New Achievements
The developed radio device for the smart meter
The developed radio device for the smart meter

This time, NICT has developed a radio device surely compliant to the radio specifications in the finalized IEEE 802 standards where NICT's proposals to IEEE 802.15.4g/4e task groups are well included, and it further supports operations in newly allocated “920 MHz band” in Japan. Moreover, the radio device reduces its size to one-third and its power consumption to one-tenth compared with the one previously developed by NICT, thanks to its highly integrated MAC circuit and small-sized and low-power PHY circuit. Also, this radio device has obtained technical standards conformity certification for 920 MHz, which enables practical operation across the country.

One of the remarkable points is low-power multi-hop transmission management capability that automatically and autonomously constructs data collection/circulation topology among meters when they are turned on. Then, any pair of communicating devices synchronizes with each other by employing intermittent and short periods for data receiving/standing by and transmitting each of which is less than one-hundredth shorter than the remaining periods for sleeping. Therefore, these devices can achieve low-power performance implying possibility of long-lived battery-powered operations for several years without battery replacement. Moreover, these devices have flexible interface modules suitable for a variety of external meters and sensors.

Future Prospects

The standardization in IEEE 802 committee is to be completed in Mar. 2012. NICT is going to create a safe and relieved society by ICT, with the standardization basements by way of Wi-SUN alliance. NICT is also seeking an opportunity of this device’s technology transfer.

Outline of the assumed system

(a) Gas / Electricity / Water meter application
(a) Gas / Electricity / Water meter application

(b) Dosimeter application
(b) Dosimeter application

Fig. 1 Usage image of smart meter radio system

Fig. 1 shows a system image of SUN.

In Fig. 1(a), a radio device equipping gas/ electricity/ water meter is allocated to each home and transmits the timely data read on the meter. Such meter data are collected to the collection/ control station in a SUN service area that is equivalent to an apartment building or a portion of residential area with several houses. As in the figure, multi-hop transmission among radio devices guarantees the required communication range and eliminates radio blind spots caused by obstacles. The collected data by SUN can be relayed in the wide area networks (WAN) and further collected in the collection/ control station in the WAN.

On the other hand, Fig. 1(b) shows an application image where the smart meters as dosimeters or climate sensors have conducted monitored data collection by exploiting radio links among meters. In this case, multi-hop transmission capability is effectively utilized in order to conduct operations of distributed meters in multi-point, and low-power performance capability enables continuous and long-term monitoring.

The developed radio device for the smart meter

Fig. 2 The developed radio device for the smart meter

Fig. 2 The developed radio device for the smart meter

Table 1 Specifications of the developed device

Size 84 mm×70 mm×20 mm (excluding antenna)
Frequency band 926.3 ~ 927.9 MHz
Modulation scheme Filtered-2FSK
Data rate 50, 100, 200 kbps
PHY payload length 0 ~ 2047 octets (1 octet = 8 bits)
Access control scheme Contention access in the active period
Routing scheme Routing to the root in the tree shaped topology

Fig. 3 Access control in the developed device

Fig. 3 Access control in the developed device

Fig. 2 shows the developed radio device for the smart meter and Table 1 shows its specifications.

Fig. 3 shows a concept of access control employed in the developed radio device. The beacon signal is usually turned off in order to avoid excessive power consumption owing to periodical transmission and it is transmitted only when requested. There are two types of periods; the active period and the sleep period as in Fig. 3. Only the active period includes receiving or standing by state of the device. In contrast, the sleep period indicates sleeping state of the device except for the case the device continuously receive a data frame from the last active period as in Fig. 3, which can decrease the average power consumption by exploiting the existence of sleep period. The developed radio device automatically and autonomously constructs a tree topology as in Fig. 3 after turned-on, then conducts an effective collection of data relaying as depicted in Fig. 3.

Glossary

IEEE 802 committee is a committee engaged in standardization for communication systems such as LAN in IEEE (Institute of Electrical and Electronic Engineers) that is a non-profit professional association dedicated to advancing technological innovation related to electricity. In the committee, a working group (WG) named IEEE 802.15 deals with the standardization for wireless personal area networks (WPAN). This WG accommodates several task groups (TGs) as depicted below, each of which is organized according to its goal.

IEEE 802.15.4: IEEE 802.15.4 is a TG that has standardized the PHY and MAC specifications for low-rate wireless personal area networks. In the IEEE 802.15.4 standard, PHY specifications define 20 kbps, 40 kbps and 250 kbps data transmissions on 868 MHz, 902 MHz and 2.4 GHz frequency bands respectively. Moreover, MAC specifications define a concept of a device group named PAN and access control schemes such as TDMA or CSMA held in the PAN.
IEEE 802.15.4g: IEEE 802.15.4g is a TG that is standardizing the necessary PHY amendments in the existing IEEE 802.15.4 standard that is required in order to realize SUN (smart utility networks). The latest version of the draft defines additional modulation schemes and frequency bands, and expanded data payload.
IEEE 802.15.4e: IEEE 802.15.4e is a TG that is standardizing the accompanying MAC modifications with any of PHY amendments in the existing IEEE 802.15.4 standard as for IEEE 802.15.4g. The latest version of the draft defines intermittent data exchange functions with low-power consumption as one of the typical modifications related to SUN.


PHY (PHYsical) layer means a concept that expresses subdivided communication functions by assuming hieratical layers as well as MAC layer. PHY layer defines the electrical and physical specifications for devices. In particular, it defines the relationship between a device and a transmission medium, such as a copper or optical cable and connector types for the cables.

MAC (Medium Access Control) layer means a concept that expresses subdivided communication functions by assuming hieratical layers as well as PHY layer. MAC layer provides addressing and channel access control that enable several terminals or network nodes to communicate within a multi-point network, which is represented by the MAC addresses peculiar to communication devices or by the time divided access scheme; TDMA.

A certification for a radio device referred in "Enforcement Ordinance of the Radio Law" by MIC, which certifies the device to conform to the technical standards regulated by Radio Law. With this certification, a radio device can be practically used in every region of Japan.

An organization that supports certification and promotion for smart meter radio communications by assuming IEEE 802.15.4g standards adoption for low-power smart meter radio systems. Wi-SUN alliance is established on Jan. 24th, 2012. NICT is a promoter member of Wi-SUN alliance.

Please refer to the press release below:

Press release:

"NICT Successfully Conducted the Proof Test On Smart Meter Radio Devices That Enables Low-Power Operations,"
http://www.nict.go.jp/en/press/2011/03/17-1.html (Mar. 17th, 2011)

Multi-hop transmission means a transmission that includes more than one relaying by other radio device(s) than transmitter and receiver devices, which is different from the direct transmission between devices. The reachable range of the multi-hop transmission can be proportionally expanded to the number of relaying. Moreover, the multi-hop transmission enables the same reachable range as a direct transmission with lower transmission power for each device than that for the direct transmission. Furthermore, the multi-hop transmission can also provide relaying route avoiding obstacles for radio waves thereby eliminates radio blind spots.

Technical Contact

Hiroshi HARADA, Fumihide KOJIMA

Smart Wireless Laboratory
Wireless Network Research Institute
Tel: +81-46-847-5074, +81-46-847-5084
E-mail:
E-mail:

Media Contact

Sachiko HIROTA

Public Relations Department
Tel: +81-42-327-6923
E-mail: