NICT Successfully Conducted the Proof Test On Smart Meter Radio Devices That Enables Low-Power Operations

- Automatic and autonomous control, meter-reading and monitoring via radio communications under both ordinal and emergency situations -

March 17, 2011

National Institute of Information and Communications Technology (hereinafter called NICT, President: Hideo Miyahara) has developed smart meter radio devices compliant to the smart utility networks　(hereinafter SUN) standard draft that enables automatic and autonomous control, meter-reading and monitoring, and is under standardization process in IEEE 802 committee, and has successfully conducted the proof test where metering data on gas meters are automatically and surely collected. The developed radio device can automatically construct data collecting topology with multi-hop transmission capability linking up with other devices after it is turned on. Moreover, the radio device realizes radio communication scheme (specifying PHY and MAC technologies) that enables several year continuous low-power operations driven by batteries thereby provides steady performances under emergency situations as well as ordinal situations.

Background

Control scheme on electricity/ gas/ water meters that can provide environmentally harmonized life style by reducing energy consumption at homes has been considered as one of the most significant technologies. Especially, research and development on the fusion of radio communication and meter implementation technologies that effectively and surely realizes automatic and autonomous control, data reading and monitoring on each meter at homes under emergency situations has become a further significant topic. This system is named as Smart Utility Networks (SUN) and a global research and development on SUN system is eagerly conducted. NICT has also been engaged in such research and development on SUN, has proposed PHY and MAC specifications as a SUN standard proposal that is under standardization in IEEE 802 committee and has successfully let the proposal included in the latest draft. However, NICT and other organizations have not conducted the proof test for such specifications for realization.

New Achievements

The developed radio device is surely compliant to the radio specifications in the current IEEE 802 standard draft where NICT had contributed. One of the remarkable points of the device is low-power multi-hop transmission management capability that automatically and autonomously constructs data collection/circulation topology among meters when they are turned on, in which any pair of communicating devices synchronize with each other in the very short periods for data listening/ receiving and transmitting thereby achieve one hundredth lower power consumption than the conventional case without synchronization. Such a low-power performance confirms the possibility of long-lived battery-powered operations for several years without battery replacement.

Future Plans

The standardization in IEEE 802 committee is to be completed in the end of 2011. With those achievements NICT is going to provide safe and relieved society by ICT, with also contributing to Japanese regulatory modification for radio facilities.

Terminology and Interpretations

Smart Utility Networks (SUN):

Smart utility networks is a radio communication system that realizes effective reading and collection of meter data with the gas/ electricity/ water meters equipping radio devices and their radio communication capabilities. How to guarantee the required service area considering the radio wave degradations and how to achieve low-power operations from the maintaining point of view are considered as major technical challenges for SUN. In the future, SUN is expected to effectively works not only for meter data collection but also for energy consumption management based on such collected data.

IEEE 802 committee:

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 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 are required in order to realize SUN. 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. (IEEE 802 committee web site: http://www.ieee802.org/, IEEE 802.15WG web site including anchors to other related TGs: http://www.ieee802.org/15/)

Multi-hop transmission:

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.

PHY and MAC:

PHY and MAC both mean concepts that express subdivided communication functions by assuming hieratical layers.
PHY 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: MAC layer provides addressing and channel access control that enable several terminals or network nodes to communicate within a multi-point network, which are represented by the MAC addresses peculiar to communication devices or by the time divided access scheme; TDMA.

Supplementary Information

Figure 1: SUN system image.

[Outline of the assumed system]

Fig. 1 shows a system image of SUN. In this image, 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 Fig. 1, 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.

Figure 2: A developed radio device for the smart meter.

[A developed radio device for the smart meter]

1. Radio device specifications
Fig. 2 shows a 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 listening/ receiving state of devices. In contrast, the sleep period indicates sleeping state of the devices except for the case the devices 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.

Figure 3:Access control in the developed device

Table 1 Specifications of the developed device
Size	20cm×17cm×7.5cm
Frequency band	953.0 MHz
Transmission power	10 mW
Modulation scheme	Filtered-2/4FSK
Data rate	50, 100, 200kbps
PHY payload length	0~2047octets(1 octet = 8 bits)
Access control scheme	Contention access in the active period
Routing scheme	Routing to the root in the tree shaped topology

2. Proof test on the developed radio device

Fig. 4 shows a visual interface that depicts the performances of the developed devices in the proof test. In the test, five radio devices including one collection/ control station successfully constructed the data collection topology for SUN. Moreover, four devices besides the collection/ control station are connected to gas meters respectively, and the collection performances of meter data from each of the four meters are surely confirmed. In the proof test, direct transmission between two devices apart from each other by at least 150m is observed. Thus, it confirmed that at least 300m radius SUN service area is feasible, assuming multi-hop transmission with only one relaying as in the proof test.