Abstract
This paper presents a ranging receiver architecture able to timestamp IEEE 802.11b Wireless LAN signals with sub-100 picosecond precision enabling time-based range measurements. Starting from the signal model, the performance of the proposed architecture is assessed in terms of statistical bounds when perturbed by zero-mean additive white Gaussian noise (AWGN) as well as in case of multipath propagation. Results of the proposed architecture, implemented in a Field Programmable Gate Array-(FPGA-) based prototype, are presented for different environments. For AWGN channels, the prototype system is able to attain an accuracy of 1.2 cm while the ranging accuracy degrades in dynamic multipath scenarios to about 0.6 m for 80% of the measurements due to the limited bandwidth of the signal.
Highlights
Despite the fact that Global Navigation Satellite Systems (GNSSes) cover nearly 100% of the planet, satellite-based localization is not available within buildings as the roofing and walls deteriorate the signal to a degree where an errorless decoding is no longer possible
For a simple scenario with 4 receivers, even a 1 Gbps connection to the locating unit is not sufficient. Due to these substantial drawbacks of correlation-based localization in Wireless LAN (WLAN), this paper proposes to perform Time of Arrival (ToA) estimation in each base station and to calculate the position based on the Time Difference of Arrival (TDoA) in the locating unit
The proposed Fractional Delay Ranging Receiver (FDRR) architecture has been implemented using the SMart integrated Localization Extension 3 (SMiLE 3) base station hardware, which is a revised version of our previous hardware described in [22]. It consists primarily of an RF mixer IC to convert the WLAN signal to the baseband, a dual-channel ADC/DAC, an FPGA for signal processing and message handling, and an Ethernet connection to communicate the captured ranging parameters to the locating PC calculating the positions
Summary
Despite the fact that Global Navigation Satellite Systems (GNSSes) cover nearly 100% of the planet, satellite-based localization is not available within buildings as the roofing and walls deteriorate the signal to a degree where an errorless decoding is no longer possible. Radio propagation within complex environments, typical for indoor scenarios, are challenging for high-speed wireless communication, but even tougher for any form of localization service. One major reason why indoor radio localization systems are way behind satellite navigation solutions is that the majority of all current wireless communication standards have not been designed with position determination in mind. These signals are often referred to as Signals of Opportunity (SoO). The degree of complexity depends primarily on the measurement principles ranging from Received Signal Strength (RSS) to time or angle measurements, or a combination of these. The conclusion summarizes the findings, and an outlook for further investigations is given
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