tailieunhanh - Advanced Trends in Wireless Communications Part 9

Tham khảo tài liệu 'advanced trends in wireless communications part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 270 Advanced Trends in Wireless Communications environment Tadakamadla 2006 . These objects induce a signal reflections problem and in a RSSI measurement this reflected signal can add to the received and measured signal without system knowledge. If target node is in the middle of two metallic objects this could be a serious problem because target node can communicate but signal reflections make target node estimate other position than the correct position. To improve a good distribution some distance from nodes to this metallic objects are sufficient to decrease the signal reflection errors. The weather conditions like temperature relative humidity and pressure in indoors environment could influence the final result in the localization system. Equation 1a shows that the RSSI measurement has a relationship with the RF propagation parameters A dBm and nAi i 1 . n . These parameters change with these weather conditions and have different values as the signal attenuation in the atmosphere is not the same for all conditions. So if RF propagation parameters are different RSSI measurement changes for the same position. To prevent this error target node has to know the accurate RF propagation parameters. The implemented framework in this study has a function that estimates the signal propagation parameters without the measurement of temperature relative humidity and pressure. This function implements a mathematical process to estimate the RF propagation parameters but this process also depends on the RSSI measurements. So the measurement of temperature relative humidity and pressure with this process could help to find better accurate RF propagation parameters. In addition weather conditions also influence electronic components such as integrated circuits and batteries. Experimental results show meanwhile that if temperature and humidity do not change more than 10 then RSSI measurements are not changed by these conditions. In fact in indoors industrial environments .