Abstract-The feasibility of centimeter-accurate carrier-phase differential GNSS (CDGNSS) positioning using a smartphone's internal GNSS antenna and GNSS chip is investigated. Precise positioning on a mass-market platform would significantly influence the world economy, ushering in a host of consumer-focused applications that have so far been hampered by the several-meter-level errors in traditional GNSS positioning. Previous work has shown that GNSS signals received through a mass-market smartphone's GNSS antenna can be processed to yield a centimeter-accurate CDGNSS position solution, but this earlier work processed all GNSS signals externally to the smartphone. The question remains whether a smartphone's internal oscillator and GNSS chip can produce observables of sufficient quality to support centimeteraccurate carrier-phase-based positioning. This paper answers the question by accessing and processing the raw code-and carrierphase observables produced by a mass-market smartphone GNSS chip-observables that have heretofore been unavailable to the research community. The phone's carrier phase measurements are shown to suffer from five anomalies compared to those from a survey-grade GNSS receiver, four of which are readily fixed in post-processing. The remaining anomaly, an error in the phase measurement that grows approximately linearly with time, currently prevents the phone's phase measurements from satisfying the conditions for CDGNSS positioning. But the phone's measurements seem otherwise fully capable of supporting cmaccurate carrier-phase differential GNSS positioning. A separate analysis of a smartphone's GNSS signal strength dependency on azimuth and elevation reveals that multipath-induced deep fading and large phase errors remain a significant challenge for centimeter-accurate smartphone positioning.

No abstract

Abstract-The phase reconstruction technique presented here combines an integer least squares technique for estimating phase ambiguities at the beginning of each TDMA phase burst with a Kalman filter and smoother for removing these ambiguities and optimally "stitching" the bursts together. A Monte-Carlo-type simulation and test environment has been developed to investigate the sensitivity of the proposed phase reconstruction technique to various system parameters, namely, carrier-to-noise ratio, receiver clock quality, TDMA transmitter clock quality, line-of-sight acceleration uncertainty, and TDMA burst structure. Simulation results indicate that successful carrier phase reconstruction is most strongly dependent on the TDMA burst period and on the combined phase random walk effect of the receiver and transmitter clocks, the propagation effects, and the range errors.

Abstract-A strategy known as Tightly-Coupled Opportunistic Navigation (TCON) is proposed for extending the penetration of GPS-assisted femtocells in weak-signal indoor environments. Standards and regulatory agencies impose strict time, frequency, and location requirements on femtocells. These can be met with GPS aiding to unparalleled time and positioning accuracies, but GPS signals are extremely weak and thus difficult to acquire indoors. The results of this paper suggest that a TCON solution fusing GPS with CDMA cellular signals offers significant sensitivity gains over state-of-the-art assisted-GPS receivers, allowing GPS-synchronized femtocells to be deployed in 90% of all residences.

No abstract