# Analysis of AMI Communication Methods in Various Field Environments
## 3 Wireless Communications for AMI
### Wireless Communication Methods  
Wi-SUN, which is the physical layer of IEEE 802.15.4 g, and ZigBee protocol, which is based on IEEE 802.15.4-2003, can be used as wireless communication methods for AMI applications. Before conducting experiments for practical field environments, we first evaluate the performance of wireless modems in a laboratory and line of sight (LOS) environments.  
Figure 8: Simplified short-distance model for the received power \(P_{R}(d)\).  
For Wi-SUN, we use two types of modems as shown in Figure 9. Wi-SUN Modem 1 (Nuritelecom Co. Ltd., Seoul, Korea) of Figure 9(a) contains CC1200 RFIC and CC1190 front-end IC of Texas Instruments. This modem is currently used to collect data from smart meters of AMI. Wi-SUN Modem 2 (Automan Co. Ltd., Gunpo-si, Korea) of Figure 9(b) contains Si4463 RFIC of Silicon Labs and SE2435L front-end IC of Skyworks. This modem can be used for more specific experiments by constructing a Wi-SUN test system as shown in Figure 10. Both modems can transmit RF signals of output powers from 25 mW (14 dBm) to 200 mW (23 dBm) by setting registers in firmware programs. Wi-SUN Modem 2 can select using an external LNA (low-noise amplifier) to increase the receiver sensitivity gain up to 16 dB. However, for practical field environment experiments, this external LNA is not used. Features of the employed Wi-SUN modems are summarized as follows.  
* Transmitter and receiver frequency band: 920.5-923.5 MHz
* Channels and their spacing: 14 channels of 200 kHz
* Receiver bandwidth: 100 kHz (can be changed)
* Data transmission rate and packet size: 50 kbps at 128 bytes
* Receiver sensitivity: \(<\)\(-\)107 dBm at PER \(<\) 10% without external LNA
* Transmitter power: 25-200 mW (14-23 dBm)  
The receiver sensitivity can be evaluated by connecting a fixed attenuator (8493B, \(-\)20 dB) and two-step attenuators (8494B; \(0--\)11 dB with 1 dB step and 8496B; \(0--\)110 dB with 10 dB step) as shown in Figure 10(a). The transmitter power of the modem can be calibrated by using a spectrum analyzer or a power meter through a fixed attenuator (8493B, \(-\)20 dB) as shown in Figure 10(b). For field environment experiments, the received power as well as transmitter power should be calibrated by using appropriate test systems as shown in Figure 10. A wireless modem, which is based on 2.4 GHz-ZigBee protocol, is also considered for the AMI communication. The employed ZigBee modem (CNU Global Co. Ltd.) is shown in Figure 11 and also currently used to collect data from smart meters of AMI. The right module of Figure 11 is a smart meter for low voltages and the left module is a ZigBee modem for transmitting the measured electrical energy.  
Figure 10: Test system for the wireless smart utility network (Wi-SUN) measurement at line of sight (LOS) based on Wi-SUN Modem 2. (**a**) Measurement of the receiver sensitivity and an Receiver Signal Strength Indication (RSSI) calibration. Fixed and step attenuators (8493B, 8494B, and 8496B of Keysight) are placed between test systems that are respectively used as master and slave parts. (**b**) Transmitter power calibration with a spectrum analyzer.  
Figure 9: Wi-SUN modems for the Wi-SUN measurement. (**a**) Wi-SUN Modem 1 (Nuritelecom Co. Ltd.). (b) Wi-SUN Modem 2 (Automan Co. Ltd.).