ISSN : 1796-2021
Volume : 4    Issue : 2    Date : March 2009

Radio Frequency Signature Correlation Based Speed Estimation for Indoor Positioning
Mostafa Afgani, Sinan Sinanović, Karim Khashaba, and Harald Haas
Page(s): 96-107
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Dead reckoning represents a class of methods for relative position estimation based on a
previously determined absolute reference position. The estimate is formulated from a combination
of the known speed, time and heading information with the known reference position. One of the
main obstacles to effective positioning of pedestrians via dead reckoning is the lack of accurate
speed estimation algorithms. Existing methods are either complex or provide results that are
unsatisfactory at the low velocities associated with pedestrians. In contrast, the two algorithms
proposed in this paper are relatively simple to implement and provide accurate results at low
velocities. In the first algorithm, a one-dimensional and unidirectional two-antenna solution is
described where the speed can be easily estimated from a knowledge of the fixed inter-antenna
distance and the time it takes for the trailing antenna to sense the same channel conditions (radio
frequency (RF) signature) previously observed at the leading antenna. Computer simulations show
that, with typical estimation errors of less than 2.67% around average pedestrian speeds, the
approach is indeed effective and accurate. A by-product of the algorithm is an environment specific
spatial correlation function which is used in the second algorithm to provide even better estimates.
With the improvements offered by the latter algorithm, relative errors of merely around 0.15% on
average are achievable. This improvement in performance over the first algorithm comes at the cost
of slightly higher computational complexity. When subsequently used for user displacement
estimation, a relatively small error of 24.5cm is observed after a duration of 60s.

Index Terms
speed estimation, pedestrian dead reckoning, spatial correlation, radio frequency signature