This paper discusses a novel communication system, devoted to networking of electrical appliances. The proposed solution relies on a “proxy” approach: bidirectional point-to point communication (called ULP: Ultra-Low cost Power-line) is established on the power-supply wire, between the appliance and the outlet. Here a transceiver embeds both network management functions and ULP communication, acting as a proxy between the appliance and the home network. The proposed approach provides several advantages: i) communication costs at the appliance side are kept at a minimum and, ii) appliance hardware and software are virtually independent from the actual networking protocol, managed by the external proxy device. In order to make the application of ULP communication straightforward, transceiver physical layer have been implemented in a dedicated peripheral for a general-purpose microcontroller. Test of the peripheral has been carried out by exploiting a development tool based on a μC-FPGA mixed architecture, where programmable device is directly connected to the microprocessor bus. This solution closely emulates the perspective microcontroller architecture, and allows for extensive testing of the device under realistic operating conditions. ULP communication has been fully characterized, attaining a BER figure well below 10−6.

1. 11.1-5
Electrical Appliances Networking: an Ultra-Low Cost
Solution based on Power-Line Communication
A. Ricci , Student Member, IEEE, V. Aisa , I. De Munari , V. Cascio and P. Ciampolini
Dept. of Information Engineering, University of Parma. Parma, Italy. E-mail: andrea.ricci@nemo.unipr.it
Indesit Company S.p.A., Fabriano, Italy
Abstract--This paper discusses a novel communication system,
devoted to networking of electrical appliances. The proposed
Communication node micro-
solution relies on a “proxy” approach: bidirectional point-to- (e.g. ZigBee, WiFi, PLC, ...) controller
AFE CPU
point communication (called ULP: Ultra-Low cost Power-line) is micro- ULP ULP
AFE peripheral
established on the power-supply wire, between the appliance and controller
the outlet. Here a transceiver embeds both network management
functions and ULP communication, acting as a proxy between
Smart
the appliance and the home network. The proposed approach Adapter
provides several advantages: i) communication costs at the
appliance side are kept at a minimum and, ii) appliance Ultra Low-Cost
Digital Appliances
hardware and software are virtually independent from the actual Power-line
networking protocol, managed by the external proxy device. In
order to make the application of ULP communication
straightforward, transceiver physical layer have been Home Network Service / Control
(e.g. RF) Device
implemented in a dedicated peripheral for a general-purpose
microcontroller. Test of the peripheral has been carried out by
exploiting a development tool based on a µC-FPGA mixed Fig. 1. Network Structure, based on a “proxy” approach.
architecture, where programmable device is directly connected
to the microprocessor bus. This solution closely emulates the
transceiver (referred as “Smart Adapter”) embeds both
perspective microcontroller architecture, and allows for network management functions and ULP communication,
extensive testing of the device under realistic operating acting as a proxy between the appliance and the home
conditions. ULP communication has been fully characterized, network. By this approach, several advantages may be
attaining a BER figure well below 10−6. attained: i) communication costs at the appliance side are
negligible and, ii) appliance hardware and software are
I. INTRODUCTION virtually independent of the actual home networking protocol.
Nowadays, modern household appliances embed digital General-purpose adapters can be designed, sharing design and
controllers to manage many tasks: low-cost digital cores manufacturing costs on larger production volumes.
control electrical load and collect information from sensor Part of this work was carried out in the framework of The
signals. Therefore, technology scaling and electronic cost European Application Home Alliance (TEAHA) project [6].
decrease directly foster functionality increase of modern TEAHA’s objective is to develop an open, secure,
digital appliances. Among most interesting features, network interoperable, and seamless global home platform. ULP based
connectivity is expected to be widely implemented in the next network structure represent a fully TEAHA compliant
future. Networking will allow for remote control, smart power solution for low-cost electrical appliances networking.
management and, mostly important, it will enable remote The rest of the paper is organized as follows: Sect. II more
maintenance or servicing, SW upgrades and early fault specifically describes the network structure whereas Sect. III
diagnostics. Connectivity will hence improve functionality, deals with the prototypal implementation. Sect. IV reports
reliability and performance of appliances. Several network experimental results, and conclusions are eventually drawn in
devices and protocols have been proposed to this purpose Sect. V.
(e.g., LON [1], Konnex [2], etc.); however, no agreement on a
universally recognized home-networking “standard” has been II. ULP COMMUNICATION BASICS
reached yet. Furthermore, the cost of standard communication A detailed description of ULP communication goes beyond
nodes is unsuited compared to the extremely tight economic the scope of this abstract, and can be found elsewhere [4], [5].
constraints typical of electrical appliance market [3], Here, we shall limit ourselves to basic principles.
preventing most solutions from being effectively exploited for Downstream communication (i.e. from digital appliance to
low-cost “white goods” networking. To overcome this the smart adapter) relies on the OOK modulation [9] of the
problem, a solution has been proposed in [4], [5], based on a instantaneous appliance power consumption. Data encoding is
“proxy” approach (Fig. 1): bidirectional narrow-band (up to performed activating, during a carefully controlled period, a
200 bit/s) point-to-point communication (called ULP: small triac which drives an appliance load. At the proxy side,
Ultra-Low cost Power-line) is established on the power- data coming from the appliance are decoded by measuring the
supply wire, between appliance and the outlet. Here a mean power absorbed during each cycle of the supply voltage.

2. Upstream communication, instead, is based on precise have then carried out a VLSI implementation. We have
perturbations of the power supply waveform. The smart implemented the architecture by means of a complete
adapter generates low-amplitude glitches (about 20V), standard-cell synthesis process, exploiting UMC 0.18 µm
synchronized with the zero-crossing signal. To this purpose, a commercial technology. The synthesized layout allowed for
couple of zener diodes are connected in series with appliance estimating area consumption, as well as parasitics. Post-layout
power supply. Data are encoded according to a PPM scheme simulations were carried out to evaluate power consumption
[9]: measurements demonstrate that transmitting a nibble per figures. Table I reports detailed results of the analysis. Actual
period without exceeding noise limits set by regional chip implementation is being carried out at Renesas.
standardization committees (e.g. CENELEC in Europe) is
possible. At the appliance side, an inexpensive analog front- IV. EXPERIMENTAL RESULTS
end (AFE), made by a first order BPF and two Schmitt- Field tests has been carried out by exploiting the FPGA
triggers, couples the power section to digital circuitry. peripheral implementation. Different appliance loads (lamps,
Decoding task in the digital domain just require elementary capacitive power-supply filters and electrical engines) were
binary counters. Data redundancy and a simple error- connected to the power-line following several different time
correction scheme are exploited to improve communication. sequences (e.g., different operating cycles of a washing
machine), in order to simulate noise of the actual operating
III. PROTOTYPES IMPLEMENTATION environment. We collected statistical data during repeated
ULP implementation at the appliance could be easily communication sessions (107 information bits for each load
carried out by programming a microcontroller. However, state). Table II reports experimental error bit rate of physical
software resources are often critical in the management of layer, evaluated under different operating environments. At
low-cost electrical appliances (white goods in particular). data-link layer, thanks to error-correcting (ARQ) software
Hence, In cooperation with Renesas Corporation, we procedures, analysis indicates a BER figure well below 10-6,
investigated the adoption of an hardware solution, based on which is more than adequate to the specific purpose.
the integration of ULP physical layer within the
microcontroller architecture as a dedicated peripheral. The
TABLE II
impact on silicon area of the microcontroller would be almost EXPERIMENTAL BIT ERROR RATE
negligible, and software code of ULP data-link layer would Load Physical Layer BER
result extremely simple, thus leading to a cost-effective
Capacitive Filter 3.75E-6
solution. We have hence designed a digital architecture Lamp 4.37E-6
implementing the ULP management functionalities. Electric Motor (light routine) 5.62E-6
First, we have investigated the feasibility of the proposed Electric Motor (medium routine) 6.25E-6
approach. We made reference the Renesas H8 microcontroller
family [7], widely adopted for appliance control. A first V. CONCLUSIONS
physical implementation of the ULP peripheral has been In this paper we introduced a communication system, aimed
carried out on a FPGA device, and tested on the Renesas at networking digital household appliances. Appliance
development system based on the E6000 emulation board [8]. connectivity is achieved, in a fashion independent of the
A VHDL description of the ULP unit has been used to actual home-networking protocol, by transferring higher-level
configure an Altera FLEX10K device, embedded into the communication tasks to an external “proxy” device.
microcontroller emulator. The emulator directly accesses Narrow-band communication can thus implemented in digital
internal bus signals, allowing for testing the peripheral against appliances at extremely low cost: the additional expenses due
the same bus interface and protocol of the actual to ULP communication devices can be roughly estimated in
microcontroller. Next, we exploited such a prototype to the order of some tens of cents. The proposed architecture is
functionally validate the ULP communication principle, and to therefore a cost-effective solution, suitable for providing basic
investigate the transmission performances of the protocol, as network capabilities to digital appliances.
TABLE I REFERENCES
RESULTS OF VLSI PERIPHERAL SYNTHESIS AND SIMULATION
[1] Echelon Corporation, LonTalk Protocol Specification, version 3.0. 1994.
Cell Area [µm2] Pdyn [µW] @ Vdd=1.8V Pleakage [nW] @ Vdd=1.8V [2] Konnex Association, KNX Standard. 2001.
28008 [3] V. Aisa, et al., International Appliance Manufacturing, 2004, pp. 85-91.
active mode: 97.72
(equivalent to [4] A. Ricci, et al., in Proc. 2006 ISPLC, pp. 239-244.
2894 NAND2 subactive mode: 87.28 138.98 [5] A. Ricci, et al., in Proc. 2005 ISPLC, pp. 300-304.
gates) standby mode: 26.19 [6] “Teaha web site,” http://www.teaha.org.
[7] Renesas Tech. Co., H8/3687 Group HW Manual, rev. 3.0
[8] Renesas Tech. Co., H8/300H Series E6000 Emulator, User’s Manual
reported in Sect. IV below. [9] A. B. Carlson, Communication Systems. 3rd Edition, McGraw-Hill.
To preventively evaluate the impact of peripheral
integration into existing microcontroller architectures, we