Positioning Performance of the Indoor Networks of Range-based Reference Stations

Objectives: In the indoor positioning, the layout of network comprised of many reference stations with ranging function, plays a crucial role to the positioning performance. In order to reveal the particular relationship between the positioning performance and the network layout of reference stations, a variety of layout conditions were investigated in light of the dilution of precision (DOP) comprehensively. Methods: In conditions of different shapes, sizes, heights and scales, a variety of network-layout schemes were designed and tests of positioning performance were completed. We designed circular network, square network, linear network and solid circular network, then the influences of different shapes on positioning performances were explored. We tested the circular networks with radiuses of 5m, 10m and 20m, so the influences of different sizes on positioning performances were revealed. We assessed the circular networks with heights of 3m, 6m, 9m and 12m, and the influences of different heights on positioning performances were investigated. We tested the circular networks with 4, 6, 8 and 12 stations, and the influences of different scales on positioning performance were provided. Results: The results show that:1) The positioning dilution of precision (PDOP) in the circle network is better than that of the square network, while the linear network is not suitable for three-dimensional positioning. 2) When the radius of the circular network increases by 2 times, means of PDOP decrease by 2 times. 3) When the height of the network increases by 2 times, and means of the vertical dilution of precision (VDOP) and the horizonal dilution of precision (HDOP) reduce by 1/3 times. 4) When the number of reference stations in the circular network increases by 2 times, and means of PDOP reduce by 1/3 times. 5) When the height of the network is about half the radius of the service area, HDOP and VDOP reach to an equilibrium. 6) When more than 6 reference stations are uniformly deployed over the boundary of service area, the HDOP and VDOP are lower than 1. Conclusions: This study provides the principles and characteristics of positioning performances with different indoor network layouts. The results will contribute to identify the optimal positioning areas, and predict the network positioning performance. Thereby, it is beneficial to guiding the design of indoor positioning systems, such as supporting the deployments of the shape, height, number and radius of reference stations.