Abstract
This paper presents a novel audio indoor localization system. In the proposed system, four speakers placed at known positions transmit chirp signals according to the time-division multiple access (TDMA) plus frequency-division multiple access (FDMA) transmission scheme. A smartphone receives the signal via a built-in microphone and calculates the time differences of arrival (TDOAs). Using TDOA measurements, the position is estimated by the shrinking-circle method. In particular, to reduce the positioning error in moving conditions, a TDOA correction method based on Doppler shifts is proposed. The performance of the proposed system was evaluated in real-world experiments using a 10.971 m × 5.684 m positioning area. The results of the static-target positioning experiment showed that the TDMA+FDMA transmission scheme has more advantages in improving the update rate of the positioning system than the TDMA-only transmission scheme. The results of the moving-target positioning experiment under three different speeds demonstrated that the positioning errors were reduced by about 10 cm when the Doppler-shift-based TDOA correction method was adopted. This research provides a possible framework for the realization of a TDOA-chirp-based acoustic indoor positioning system with high positioning accuracy and update rate.
Highlights
With the development of intelligent information processing technology and smartphones, location-based services (LBS) have attracted increased attention
The synchronous node was set to control the the speakers to emit chirp signals according to the time-division multiple access (TDMA)+frequency-division multiple access (FDMA) or the TDMA transmission speakers to emit chirp signals according to the TDMA+FDMA or the TDMA transmission schemes
12b, parameter the positioning decreased upon shortening the positioning period in the TDMA-only scheme
Summary
With the development of intelligent information processing technology and smartphones, location-based services (LBS) have attracted increased attention. The key for LBS is seamless indoor and outdoor navigation for users. Ultra Wideband (UWB), ultrasound, WiFi, etc., have been used successfully to realize indoor positioning in many systems. The cost of UWB-based systems is relatively high, and smartphone sensors often cannot meet the bandwidth required by the system [1,2]. Ultrasound-based systems cannot be implemented on smartphones because the signal frequency band often is outside the acceptance range of the mobile phone microphone [3,4,5,6,7]. WiFi and Bluetooth-based systems are easy to set up due to the wide application of WiFi and Bluetooth, the positioning accuracy of both these systems can only reach the meter level [2,8], which cannot satisfy the needs of high-precision indoor positioning
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