## 3 System Architecture  
EMMNet is built on a heterogeneous networking infrastructure. In the automatic electricity meter-reading field, a sensor node is usually called a data collector, and a base station or gateway in the sensor network is called a data concentrator. EMMNet involves data collection, transmission, and access phases, as shown in Figure 1. \begin{table}
\begin{tabular}{c|c|c|c|c|c|c|c|c|} \hline \hline \multirow{2}{*}{**Platforms**} & \multicolumn{2}{c|}{**Processor**} & \multicolumn{4}{c}{**RF Transceiver**} \\ \cline{2-9}  & \begin{tabular}{c} **Program** \\ **Space** \\ \end{tabular} & \begin{tabular}{c} **External** \\ **Space** \\ \end{tabular} & \begin{tabular}{c} **Current** \\ **Draw** \\ \end{tabular} & \multirow{2}{*}{**Frequency**} & \multirow{2}{*}{**Current Draw**} & \multirow{2}{*}{**Indoor**} & \multirow{2}{*}{**Tx speed**} & \multirow{2}{*}{**Cost**} \\ \cline{1-2} \cline{6-6}  & \begin{tabular}{c} **Space** \\ \end{tabular} & \begin{tabular}{c} **Space** \\ \end{tabular} & & & & & & \\ \hline MICA2 & 128 kB & 512 kB & 8 mA & 868/916 MHz & \begin{tabular}{c} S: 27 mA \\ at 5 dbm \\ R: 10 mA \\ \end{tabular} & — & 38.4 kbps & \$125 \\ \hline TelosB & 48 kB & 1,024 kB & 1.8 mA & 2,400 MHz & \begin{tabular}{c} S: — \\ R: 23 mA \\ \end{tabular} & 20–30m & 250 kbps & \$134 \\ \hline MICAZ & 128 kB & 512 kB & 8 mA & 2,400 MHz & \begin{tabular}{c} S: 17.4 mA \\ at 0 dbm \\ R: 19.7 mA \\ \end{tabular} & 20–30m & 250 kbps & \$99 \\ \hline Imote2 & 32 MB & 32 MB & 66 mA & 2,400 MHz & — & \textless{}30 m & 250 kbps & \$299 \\ \hline Tmote Sky & 48 kB & 1,024 kB & 2 mA & 2,400 MHz & 17 mA & — & 250 kbps & \$78 \\ \hline Tmote Mini & 48 kB & 1,024 kB & 2 mA & 2,400 MHz & 17 mA & \textless{}30 m & 250 kbps & — \\ \hline Btnode & 128 kB & 128 kB & 8 mA & \begin{tabular}{c} 433/868/ \\ 916 MHz \\ \end{tabular} & \begin{tabular}{c} S: 14.8 mA \\ at 0 dbm \\ R: 7.4 mA \\ \end{tabular} & 20 m & 76.8 kbps & \$120 \\ \hline EMMNet & 128 kB & 4/8 MB & \begin{tabular}{c} 8 mA/ \\ 30 uA \\ \end{tabular} & \
\begin{tabular}{c} 433/470/ \\ 868/916 MHz \\ \end{tabular} &
\begin{tabular}{c} S: 20 mA \\ at 6 dbm \\ R: 13 mA \\ \end{tabular} & 180 m & 50 kbps & \$40 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Characteristic ubiquitous sensor network platforms. To obtain average real power information the electricity meter utilizes an ADE7755, which is a high accuracy electrical energy measurement sensor. The error of an ADE7755 is less than 0.1% over a dynamic range of 500 to 1. The only analog circuitry used in an ADE7755 is in the ADCs and reference circuit. All other signal processing (e.g., multiplication and filtering) is carried out in the digital domain. This approach provides superior stability and accuracy over extremes in environmental conditions and over time. We connect electricity meters to data collectors via an RS485 bus. Electricity meters are installed in a metal chest, and data collectors are usually beside them for safety purposes. The sensor data in our system flow from the data collectors to a data concentrator over the DT protocol. Data can also be relayed via data collectors if the electricity meters are far from the data concentrator. The data concentrators transmit electricity meter data to the remote centralized server that provides data logging. The data is transmitted using the TCP/IP suite of protocols and therefore can be carried over types of many networks, including LAN, CDMA, and GPRS. We also propose a back-end client/server architecture to provide a user interface to the system and support further centralized processing for higher-level applications. The GUI visualization component has a graphical display that enables an overall view of the network to be shown. The visualization component also has a relation layer to display relationships between nodes and a node layer to draw the nodes themselves.