# Analysis of AMI Communication Methods in Various Field Environments
## 6 Discussions
### Discussions on the Wireless Communication  
The EPD and AR results of the five environment areas are summarized in Figure 32 and Table 3. The experimental results on Wi-SUN were obtained when the transmitter power was 23 dBm (200 mW). If we decrease the transmitter power to 14 dBm (25 mW), then the EPD values will be decreased by the multiplication factor \(10^{9/a}\) from (11). For the Overhead Residential Area as an example, the EPD value decreases to \(d_{0}=118\) m when the transmitter power is 14 dBm. The EPD results in Table 3 are calculated using \(10^{9/a}\). We can observe that the EPD values of the Overhead Commercial, Rural, and Factory Areas are similar to each other as \(d_{0}=621-978\) m. Especially for the Overhead Commercial Area, the EPD value is quite long, \(d_{0}=978\) m, which is longer than that of the LOS experiment of Figure 12b, \(d_{0}=678\) m. Hence, we can notice that the three areas have good wireless communication characteristics. However, the EPD value of the Overhead Residential Area is as low as \(d_{0}=188\) m compared to the cases of the Overhead Commercial, Rural, and Factory areas. In other words, the Overhead Residential Area usually shows worse EPD values and hence requires more wireless nodes to secure a good communication margin. We should also note that the case of the Underground Area shows the worst communication characteristics. For this area, using PLC will provide stable communication characteristics. From the results of Figure 32 and Table 3, we can conclude that the Wi-SUN modem is usually better than the ZigBee modem for AMI communication purposes. However, for the Underground Area, in which the EPD values of the Wi-SUN and ZigBee modems are similar, we can use a 2.4 GHz communication system in a hybrid from [31]. Figure 31: Graphical simulation of the received power for the HS PLC modem (Site 1-2, Overhead Residential Area). (**a**) MP at distance 33.5 m. (**b**) MP at distance 102 m.  
Figure 32: AR with respect to the equal-power distance (EPD) for the five environment areas. The Wi-SUN modem of 920 MHz provides better communication distances for all areas compared to the ZigBee case of 2.4 GHz. Using the acquired regression models of (10) for each field environment area, we can graphically simulate an RF power map depending on the field environment areas. This simulation is useful in planning wireless AMI networks for a given site. From the NDIS map of the corresponding site, we can extract node locations and building structures. Considering an obstacle attenuation of 10 dB for building structures and the regression model for the corresponding field environment area, we can plot a received power map of RSSI values in dBm according to the color bar as shown in Figure 33a,b. If we place an MP at a utility pole, which is marked at an NDIS map as white rectangles as in Figure 33a, then we can obtain the received power and SNR value from the difference between the received power and the baseline noise power for the given field environment area. The site of Figure 33 belongs to the Overhead Residential Area and the obtained regression curve is \(p=-44.4\log(d)+12.4\) (dBm) with the maximal baseline noise of \(-88.5\) dBm as shown in Figure 25a. For a single node example of Figure 33a, the red regions imply received powers from 10 dB to 20 dB and the received power at a location, which is indicated as a white rectangle, is \(-77.9\) dBm. Here, the link budget is 29.1 dB if the receiver sensitivity is \(-107\) dBm. By placing one more node as shown in Figure 33b, we can increase the link budget to 36.2 dB and enlarge the wireless coverage range. These link budgets are greater than recommended fade margins of 10 dB to 25 dB. At each position, the maximally received power can be displayed from several nodes. Hence, from the graphical simulation of Figure 33, we can determine an appropriate number of nodes and their positions in designing an AMI communication network for a given site. We can also obtain the SNR values of 10.6 dB and 23.7 dB, respectively, for Figure 33a,b.