Positioning Based on Signals of Opportunity

Recent Advances in Indoor Localization: A Survey on Theoretical Approaches and Applications

“…On the other hand, local positioning permits signals produced through the cooperative network. Thus, a SoOP technique can be used for the purpose of localization, such as using timing measurements to perform opportunistic positioning [41]. Many SoOPs are used for mobile localization without GPS [42][43].…”

Opportunistic Time-of-Arrival localization in fully asynchronous wireless networks

“…Only a few previous papers have addressed the problem of localization based exclusively on reception timestamps from non-synchronized clocks [21][22][23][24][25]. In particular, [21][22][23] address the quasi-synchronous scenario, i.e., they do not model clock drifts-a gross limitation for real-world implementations.…”

“…In particular, Jean and Weiss [21] as well as our previous work [22,23] have assumed semi-idealized scenarios where clock frequencies are perfectly tuned across all nodes. In other words, their clock error model considers non-zero (unknown) time offset (termed ''clock bias'' hereafter) but zero frequency offset (equivalently: ''clock drift'' or ''clock skew'').…”

“…First, advancing over [21][22][23], we consider a more realistic clock error model that includes a frequency offset (clock drift) in addition to time offset (clock bias). This makes our model much closer to real operating conditions of wireless systems composed by COTS radios, whose internal clock are unavoidably affected by a certain deviation from the nominal frequency, normally contained within a few tens of ppm.…”

“…This makes our model much closer to real operating conditions of wireless systems composed by COTS radios, whose internal clock are unavoidably affected by a certain deviation from the nominal frequency, normally contained within a few tens of ppm. Second, we propose a general low-complexity approach to localization in asynchronous systems that does not require to subtract upfront the available measurements, as done in [24,25] (and partially in [22,23]). For wellconnected topologies the system matrix is rank-deficient by one, and we provide a means to estimate the resulting pseudoranges in closed-form.…”