tailieunhanh - Emerging Communications for Wireless Sensor Networks Part 14

Tham khảo tài liệu 'emerging communications for wireless sensor networks part 14', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Indoor Location Tracking using Received Signal Strength Indicator 253 In Fig. 18 a R1 to R3 are reference nodes in the area. A mobile node L1 is hold by a user and moving around the area. L1 collects data from all reference nodes and forwards them to a computer. The packet includes the ID of each reference nodes IDR1 IDR2 IDR3 RSSI values from each reference node RSSI1 RSSI2 RSSI 3 and the ID of the mobile node IDL1 . If the number of reference node increases the packet size would be large. This largely increases network traffic and load. In Fig. 18 b R4 to R6 are reference nodes in the area. A mobile node L2 is hold by user and moving around the area. L2 collects data from all reference nodes and perform location estimation locally. The resultant packet is then forwarded to computer. Hence the packet only includes the coordinate x y space ID SP01 and the ID of the mobile node IDL2 . If the number of reference node increases the packet size does not increase but still remains small and constant because only the estimation result is forwarded to computer. Wireless sensor network have substantial processing capability in the aggregate but not individually. For most of the low-power mobile device such as wireless sensor motes the processors or microcontrollers are limited in computational capability. For this reason indoor location estimation algorithms must be simple and ease of implementation. For ensuring light-weight processing and tool-independent programming it is necessary to consider carefully that algorithms mathematical calculations and processing are simple and programmable to any low-power mobile devices which have limitation and constraints. The main computational loads are in RSSI-distance conversion step and in trilateration step. Computation using trilateration can be simplified by carefully planning the locations of reference nodes at strategic locations and applying equations 21 to 23 . However the computation of RSSI-distance conversion is not easy