Implementing indoor positioning system via ZigBee devices

A wireless indoor positioning system is developed with the ZigBee technology. ZigBee devices with chipset reference designs or design-in modules are used for hardware implementation. Using Jennic´s JN5121 and Texas Instrument´s CC2430 system-on-chip modules for 2.4 GHz IEEE 802.15.4 and ZigBee, we developed the indoor positioning system testbed. Channel measurements via the testbed verified the log-normal indoor channel propagation model and were used to calculate the model parameters. We proposed an effective cooperative localization algorithm that is tailored to the ZigBee profile. It uses the ZigBee link quality indicator, which is directly related to the received signal strength, to acquire the pair-wise distances between the nodes in the network. In order to yield positioning accuracy, the algorithm combines the multidimensional scaling with the maximum likelihood estimation, and overcomes their inherent drawbacks.