A Sub-meter Accurate Positioning using 5G Double-difference Carrier Phase Measurements

Alternative positioning techniques, such as those using ambient signals-of-opportunity, have been increasingly developed for global navigation satellite system (GNSS)-challenging urban and indoor environments. For instance, cellular long-term evolution (LTE) network supports a variety of positioning methods based on signal measurements such as received signal strength or time-of-arrival (TOA). Carrier phase measurement extracted from LTE signals has also received substantial attention due to its potential high ranging accuracy. This paper presents a closed-loop (CL) carrier phase tracking architecture for positioning in LTE networks with robustness to the channel fading effects. The pilot cell-specific reference signal (CRS) is exploited for generating the channel estimation results, which are inputs for the carrier phase discriminator to measure the carrier phase error. The undesired bias corrupting the phase discriminator output for multipath channels is analytically derived. Then, the state-space model of LTE carrier signal tracking in light of the specific CRS time-frequency domain pattern is established and the state estimator gain matrix is derived based on the proportional integral filter deign. Simulation assessment of the proposed carrier phase tracking architecture is performed in a single path Rician fading channel under different Rician factors and signal powers. The impact of loop parameters, e.g., loop bandwidth and updating interval, is investigated. Real collected LTE data in a multipath fading channel is also used to comparatively analyze the performances of the existing open-loop and proposed CL carrier tracking methods combined with three LTE signal TOA estimators. The proposed algorithm in conjunction with the multipath estimating delay lock loop is shown to provide accurate and robust carrier phase measurements against multipath fading effects compared to other considered tracking schemes.

In this contribution, a novel opto-acoustic indoor navigation system for linear distance measurement is presented. The novelty consists in the simultaneous use of envelope time-of-flight (ETF) and carrier phase (CPH) measurements. In particular, we establish a two-channel link consisting of an ultrasound and infrared channel, the latter using a carrier frequency equal to the ultrasound frequency. In order to render the system extendible for multiple transmitters and receivers, code-division-multiple-access using Gold codes is employed, as all ultrasound and infrared signals share the same carrier frequency. This is also beneficial for multipath scattering suppression. The time difference between the carrier phase of the received ultrasound and infrared signals offers a high resolution but ambiguous distance signal. On the other hand, correlation of the received signals yields a coarse but unique distance signal. Experimental results show that a measurement resolution in the submillimeter range is feasible.

This study analyzes the performance of positioning techniques based on configuration changes of 5G New Radio (NR) signals. In 5G networks, a terminal’s position is determined from the Time of Arrival (TOA) of Positioning Reference Signals (PRS) transmitted by base stations. We propose an algorithm that improves TOA accuracy under low sampling-rate constraints and implement 5G PRS for positioning in a software-defined modem. We also examine how flexible time–frequency resource allocation of PRS affects TOA estimation accuracy and discuss optimal PRS configurations for a given signal environment. With the proposed configuration, the terminal can achieve sub-sample TOA accuracy, reaching approximately 0.3 samples.

In order to solve the problem of an uncertain initial state and big errors for hypersonic glide vehicle (HGV) tracking, a hybrid model algorithm is proposed by combining a single model algorithm with a multiple model algorithm. To develop the tracking algorithm with the Cubature Kalman filter, in every model filter the process equation is established based on the HGV aerodynamic model and the measurement equation is established based on the radar measurement principle. The proposed hybrid model algorithm is developed by using the multiple model algorithm in the initial tracking stage and using the single model algorithm in the stable tracking stage, and they are divided by a proposed parameter. The former can avoid divergence and reduce the errors caused by the uncertain initial state. The latter can track the HGV at higher accuracy. The simulation indicates that the proposed hybrid model has high speed accuracy in the whole tracking stage and high position accuracy in the stable tracking stage. The average position root mean square error (RMSE) using the hybrid model algorithm is almost the same as that using the single model algorithm but the average speed RMSE using the single model algorithm is about 30% greater than that using the hybrid model algorithm. In a system for defending the HGV, the speed accuracy has more effect on the trajectory prediction as time goes on. Thus, the hybrid model algorithm is an engineering algorithm for HGVs with high accuracy. In future research, the hybrid model algorithm will be studied for general maneuvering target tracking.

Global Navigation Satellite System raw measurements from Android smart devices make accurate positioning possible with advanced techniques, e.g., precise point positioning (PPP). To achieve the sub-meter-level positioning accuracy with low-cost smart devices, the PPP algorithm developed for geodetic receivers is adapted and an approach named Smart-PPP is proposed in this contribution. In Smart-PPP, the uncombined PPP model is applied for the unified processing of single- and dual-frequency measurements from tracked satellites. The receiver clock terms are parameterized independently for the code and carrier phase measurements of each tracking signal for handling the inconsistency between the code and carrier phases measured by smart devices. The ionospheric pseudo-observations are adopted to provide absolute constraints on the estimation of slant ionospheric delays and to strengthen the uncombined PPP model. A modified stochastic model is employed to weight code and carrier phase measurements by considering the high correlation between the measurement errors and the signal strengths for smart devices. Additionally, an application software based on the Android platform is developed for realizing Smart-PPP in smart devices. The positioning performance of Smart-PPP is validated in both static and kinematic cases. Results show that the positioning errors of Smart-PPP solutions can converge to below 1.0 m within a few minutes in static mode and the converged solutions can achieve an accuracy of about 0.2 m of root mean square (RMS) both for the east, north and up components. For the kinematic test, the RMS values of Smart-PPP positioning errors are 0.65, 0.54 and 1.09 m in the east, north and up components, respectively. Static and kinematic tests both show that the Smart-PPP solutions outperform the internal results provided by the experimental smart devices.

GPS time transfer is usually carried out with C/A code measurements using the common-view technique. An uncertainty of a few nanoseconds can be obtained for an integration time of about 1000 seconds when ionospheric measurements and precise orbits are used. This limits the capability of frequency comparison to the level of 3 parts in 10/sup 14/ for an integration time of one day. Recently new frequency standards have been developed that claim an accuracy at or below 1/spl times/10/sup -14/. For existing time transfer techniques it is a challenge to compare their frequency over a sufficiently short interval. Previous studies have already shown the potential of carrier-phase and P-code measurements from geodetic GPS receivers. This paper draws up tentative uncertainty budgets for clock frequency comparisons using phase and code measurements from commercially available dual-frequency and multi-channel GPS receivers. Although the level of noise involved in carrier phase measurements is two or three orders of magnitude lower than that of code measurements in the short term, other error sources such as tropospheric delay of GPS signals, multipath propagation and the phase ambiguity problem lead to a limitation in the accuracy of frequency transfer at the 10/sup -15/ level over an averaging time of one day. Carrier phase measurements, however, provide an improvement over the performance expected from code measurements for all averaging times smaller than one day.

Positioning and tracking inside buildings using wireless location methods has recently received considerable attention. One method is the estimation of the time of arrival of satellite or terrestrial-based radio frequency signals in order to produce ranges from the transmitter to the receiver. This paper investigates the effect of walls made of various construction materials on the penetration of ranging signals. In the tests conducted, a GPS pseudo-satellite transmits a pseudorandom noise code at a carrier frequency of 1.57542 GHz. After penetrating walls made of plywood, gyprock and cinder blocks, the signal is received by a GPS receiver which measures the carrier phase and the pseudorange between the transmitter and receiver using code correlation. Compared to measurements obtained with no walls present, the effect on the measurements is determined. The results indicate that the carrier phase measurement is superior to the pseudorange in terms of noise, stability, and the magnitude of the effect of the walls on the range obtained. Ranges based on the carrier phase only change by a few centimeters. Given that the integer number of cycles of the phase can be determined and phase lock is maintained, the carrier phase measurement shows considerable promise for indoor ranging.

A framework for positioning with carrier phase differential (CD) - low Earth orbit (LEO) (CD-LEO) measurements is developed. This framework utilizes a base and a rover and enables navigation with the Orbcomm LEO constellation without requiring prior knowledge of the rover’s position. The effect of ionospheric and tropospheric delays on the carrier phase and CD-LEO measurements are discussed. The residual ionospheric and tropospheric delays are studied as a function of the baseline. Moreover, the position dilution of precision (PDOP) is studied for the Orbcomm constellation, and it is found that a less than unity PDOP may be achieved for 8-minute wait times. Experimental results show a receiver positioning itself exclusively with CD-LEO measurements from two Orbcomm satellites with a position error of 11.93 m.

This paper proposed heave estimation using time-differenced GPS carrier phase measurement and compensated barometer measurement with applying error model. The carrier phase measurement makes a precise of the altitude more than code measurement because carrier phase based pseudo range has mm error. But integer ambiguity resolution problem must be solved when carrier phase measurement is used. Time-Differenced(TD) carrier phase measurements can be used to find a relative altitude using single GPS without an integer ambiguity resolution since a time-invariant. Integer ambiguity is removed by TD operation. Barometer error model estimated using Gauss-Morkov process. Output is result of kalman filter using barometer and carrier phase measurement. Performance of implemented system was evaluated through the experiments at various scenarios including static test in rural and urban areas.

One 6-channel and two 12-channel single frequency GPS receivers observing C/A (course/acquisition) code and carrier phase were tested to determine positional point accuracies under conifer and deciduous tree canopies. Positional accuracies were determined for 38 subcanopy sites by differential processing of C/A code observations only and combined use of C/A code and carrier phase. Observation periods of 2.5-30 min were evaluated. Mean positional accuracy ranged from 1.17 to 3.70 m for the 12-channel receivers based on 2.5-30 min of observation of C/A code. Mean accuracy ranged from 0.79 to 2.25 m for combined use of C/A code and carrier phase. The accuracy was 7.34 m with 30 min of C/A code observations with the 6-channel receiver. With combined use of C/A code and carrier phase the mean accuracy of the 6-channel receiver increased to 0.98-2.44 m. The accuracy increased with decreasing basal area and improving geometric satellite distribution. The mean accuracy was significantly higher for the 12-channel receivers than for the 6-channel receiver and significantly higher by combined use of C/A code and carrier phase than use of C/A code only.

In this paper we show that the judicious use of all the information available from C/A code can provide results better than the reported accuracy of P code with much lower cost. This performance however, is limited to low-dynamic, low-jamming environments which are typical of civilian applications. The elegance of P-code is primarily manifested in high dynamic vehicles (jets and missiles) and in jamming environments. Results are provided in stationary and low-dynamic cases based on code-phase, carrier-phase, doppler, and integrated doppler measurements from TRIMBLE 4000 receivers. In particular, it is shown that the relative or differential accuracy of better than 10 centimeters can be achieved in low-dynamic applications. Position fixes are obtained every second. after a short time of initial calibration and tracking. The improved accuracy is based on aiding the code phase measurements with integrated doppler. Each one second position fix. which is provided in both polar and cartisian coordinates is based on a complete and independent set of measured data, with no hypothetical modeling, interpolation, or extrapolation. INDEX TERMS: GLOBAL POSITIONING SYSTEM, GPS DOPPLER PROCESSING. TRIMBLE 4000A LOCATOR. INTRODUCTION Even a brief survey of the growing body of GPS literature, leaves little doubt that GPS will indeed replace all existing positioning and timing systems in the near future. The attractiveness of GPS is not only due to its technical superiority, but also to economic considerations. It is interesting to observe that, even in this early stage of the GPS program, production of low cost GPS receivers is a reality. Today C/A code GPS receivers can be manufactured, in large volumes, at a lower cost than LORAN receivers [1]. Of the two classes of GPS signals, C/A and P code, only C/A code will be available for civilian applications [2]. This restriction might lead one to conclude that the precision positioning and timing capabilities of GPS will not be available to civilian users. This is a false conclusion. Judicious use of all the information available from C/A code can provide results equivalent to P code, with much lower cost. In this paper we prove this claim by providing results based on code phase, doppler, integrated doppler and carrier phase measurements from TRIMBLE C/A code receivers. It is our belief that even if P code was available for civilian applications it adds very little, if any, to the precision that is available from C/A code. The elegance of P code is mostly manifested in military applications such as in high dynamic vehicles (jets and missiles) and in jamming environments. In this paper we distinguish between four levels of accuracy that can be obtained from the C/A code system:LEVEL A: Accuracy of about 10 meters,LEVEL B: Accuracy of about 1 meter,LEVEL C: Accuracy of about 10 centimeters,LEVEL D: Accuracy of about 1 centimeter, Each one of these accuracy levels can be achieved with a different type of C/A code information processing, and with a different operational requirement.

Carrier phase-based ionospheric observables using PPP models

A new TWSTFT modem was developed for both time and frequency transfer. The code and carrier phase measurements become available by it. We evaluated the performance in a common-clock and non common-clock measurements. The results encourage us to widely spread the use of the new modem.

The expected positioning accuracies of civil users utilizing modernized GPS and Galileo are derived using the error analysis in this paper. Since, in general, the performance of DLL, PLL and FLL is proportional to chip lengths and wavelengths, the positioning accuracies from various measurements of modernized GPS and Galileo are derived as function of chip length and wavelength. These results are compared with that from GPS Ll measurement. In absolute positioning, compared to GPS C/A code only case, more than 17 times performance improvement is expected when all civil code signals of modernized GPS and Galileo (L1, L2, L5, E1, E5A and E5B) are used. In relative positioning, compared to GPS L1 carrier phase only case, more than 2 times performance improvement is expected when all civil signals of modernized GPS and Calileo are used. Furthermore, the relationship between GDOP and RGDOP in single frequency case is expanded to general case where multiple frequencies and both code and carrier phase measurements are used.

In order to use a stand‐alone global navigation satellite system (GNSS) receiver to determine the stable instantaneous velocity, a new hybrid GNSS velocimetry approach combining carrier phase and Doppler measurements is proposed. This is a data fusion problem. The problem is expressed as a state‐space model, in which the deviation between the average velocity determined by the time difference carrier phase approach and the instantaneous velocity is represented by the uncertainty of the state model. In kinematic applications, this uncertainty is often variant and hard to be known in advance, a predefined process noise level of the state model is often not sufficiently accurate in the whole working time. Here, an adaptive Kalman filtering approach is employed to fix this problem. To verify the proposed approach, one static experiment and two dynamic experiments with different sampling intervals are performed, separately. All results demonstrate the validity and stability of the proposed approach.