CiteULike: dcastro's tracking

Limiter effect on cycle slip performance of synchronization loops

P Hasan — 2008-07-23T23:54:11-00:00

Communications, IEEE Transactions on, Vol. 44, No. 5. (1996), pp. 562-565.

A formula suitable for numerical evaluation is derived for the mean cycle slip time of a first-order loop with state-dependent spectral density of the loop noise. The formula is applied to a synchronizer with sinusoidal type limiter phase detector. The accuracy of the asymptotic expression due to Moeneclaey (1985) is evaluated. Better cycle slip performance of the considered synchronizer compared to that with multiplier phase detector is reported at the loop signal-to-noise ratio (SNR) α>2

Decision-directed coherent delay-lock tracking loop for DS-spread-spectrum signals

R de Gaudenzi — 2008-07-23T23:54:14-00:00

Communications, IEEE Transactions on, Vol. 39, No. 5. (1991), pp. 758-765.

The authors present a nonconventional joint data demodulation-pseudo-noise (PN) code tracking scheme for direct sequence (DS) spread-spectrum (SS) signals which solves problems of component imbalance and sensitivity with hardware simplicity and no performance degradation. An integrate-and-dump Costas loop is used for carrier recovery and data demodulation of the SS signal. Both data and carrier are then used to derive the baseband error signal of the code tracking loop. Moreover, a single passband correlator is used to perform the early-late correlation, leading to a hardware complexity equivalent to that of the tau-dither scheme, but without its loss in performance. Results of a thorough theoretical analysis of the system in an additive Gaussian noise (AWGN) environment are reported. They provide performance curves in terms of steady-state jitter and mean time to first lock loss. A superior jitter performance for low values of <e1>E</e1>b/ <e1>N</e1>0 with respect to a traditional noncoherent delay lock loop (DLL) is shown, along with the potential gain of Manchester coding upon the more usual NRZ format

Monte Carlo sampling based in-home location tracking with minimal RF infrastructure requirements

GV Zdruba — 2008-07-23T23:20:05-00:00

Global Telecommunications Conference, 2004. GLOBECOM '04. IEEE, Vol. 6 (2004), pp. 3624-3629 Vol.6.

The paper describes research towards a system for locating users in a home environment requiring only a minimal wireless infrastructure. The only sensor reading used for the location estimation is the radiofrequency received signal strength indication (RSSI) measured by an RF interface (e.g., Wi-Fi). Location estimates are computed using Bayesian filtering on sample sets derived by Monte Carlo sampling. Wireless signal strength maps for the filter are obtained by a two-step parametric and measurement driven ray-tracing approach to account for absorption and reflection characteristics of various obstacles. Our trace driven simulations indicate that RSSI readings from a single access point in an indoor environment are sufficient to derive good location estimates of users.

Frequency acquisition and tracking for mobile LEO satellite communications

Yu Su — 2008-07-23T22:23:01-00:00

Vehicular Technology Conference, 1997 IEEE 47th, Vol. 3 (1997), pp. 1738-1742 vol.3.

A class of recursive frequency acquisition and tracking algorithms for use in high dynamic mobile low Earth orbit (LEO) satellite communication systems is proposed. The underlying principle of these algorithms is to apply the least-squares method to the reconstructed phase trajectories to estimate and predict the received frequency variations (Doppler frequency, Doppler rate, etc.). We consider both additive white Gaussian noise (AWGN) and Rician fading channels and analyze the corresponding mean squared errors (MSE). The numerical performance of the proposed algorithms demonstrates that the new frequency tracking algorithms not only has rapid acquisition times but also gives smaller tracking jitters

Frequency acquisition and tracking in high dynamic environments

Yu Su — 2008-07-23T22:23:20-00:00

Vehicular Technology, IEEE Transactions on, Vol. 49, No. 6. (2000), pp. 2419-2429.

This paper presents mean squared error (MSE) analysis of two classes of frequency acquisition and tracking algorithms. Additive white Gaussian noise as well as Rician fading channels are considered. The class of batch-processing algorithms is an extension of earlier least squares proposals used in more benign (lower dynamic) environments. These algorithms try to fit the phase trajectory of the down-converted samples of a received signal. Such a trajectory will depend on the histories of both the signal and the local frequency variations when the local frequency is updated recursively. We propose a method to solve this difficulty and present both first-order and second-order recursive algorithms. Numerical results demonstrate that the MSE performance predicted by our analysis is consistent with that estimated by computer simulation and that the proposed algorithms not only provide rapid acquisition times but also give small tracking jitters

Channel tracking for RAKE receivers in closely spaced multipath environments

G Fock — 2008-05-20T12:01:59-00:00

Selected Areas in Communications, IEEE Journal on, Vol. 19, No. 12. (2001), pp. 2420-2431.

This paper deals with the problem of channel tracking for RAKE receivers in propagation environments characterized by closely spaced multipath components. After outlining why conventional single-path channel tracking algorithms fail in such scenarios, several new estimation algorithms are developed that are tailored to channels with closely spaced multipaths. This is achieved by removing or minimizing self-interference caused by multipath components. Other interfering users are treated as noise. Both timing tracking and phasor tracking and their interaction are covered in this paper. The derived algorithms are benchmarked against perfect channel knowledge on one hand and conventional tracking algorithms on the other hand, both in a UMTS test scenario. In moderate scenarios, the use of these new algorithms leads to performance improvements of up to 2 dB, in terms of signal-to-noise ratio (SNR) at moderate bit error rates, and even manages to track the channel in conditions where conventional tracking algorithms fail completely

PN Code Tracking Using Noncommensurate Sampling

KJ Quirk — 2008-06-27T11:08:15-00:00

Communications, IEEE Transactions on, Vol. 54, No. 7. (2006), pp. 1349-1349.

The use of a noninteger symbol to sample time ratio, noncommensurate sampling, in pseudonoise (PN) code-tracking loops is investigated. A noncoherent PN code-tracking loop using noncommensurate sampling and single-bit quantization is presented. An analysis method is developed to characterize the system and determine the steady-state error variance of the timing estimate. The performance of an equivalent analog code-tracking loop is derived and compared with the digital loop to investigate the degradation incurred through sampling and quantization.

Pedestrian tracking with shoe-mounted inertial sensors

E Foxlin — 2008-06-15T13:49:46-00:00

Computer Graphics and Applications, IEEE, Vol. 25, No. 6. (2005), pp. 38-46.

A navigation system that tracks the location of a person on foot is useful for finding and rescuing firefighters or other emergency first responders, or for location-aware computing, personal navigation assistance, mobile 3D audio, and mixed or augmented reality applications. One of the main obstacles to the real-world deployment of location-sensitive wearable computing, including mixed reality (MR), is that current position-tracking technologies require an instrumented, marked, or premapped environment. At InterSense, we've developed a system called NavShoe, which uses a new approach to position tracking based on inertial sensing. Our wireless inertial sensor is small enough to easily tuck into the shoelaces, and sufficiently low power to run all day on a small battery. Although it can't be used alone for precise registration of close-range objects, in outdoor applications augmenting distant objects, a user would barely notice the NavShoe's meter-level error combined with any error in the head's assumed location relative to the foot. NavShoe can greatly reduce the database search space for computer vision, making it much simpler and more robust. The NavShoe device provides not only robust approximate position, but also an extremely accurate orientation tracker on the foot.

Effects of channel distortion on code tracking error in DS spread spectrum systems

C Caini — 2008-06-15T13:40:41-00:00

Spread Spectrum Techniques and Applications Proceedings, 1996., IEEE 4th International Symposium on, Vol. 3 (1996), pp. 1012-1016 vol.3.

The delay locked loop tracking circuit of a typical direct sequence spread spectrum system has been analysed to find an analytical expression of the tracking error bias due to the presence of linear channel distortions, independently of their origin (for instance, due to band limitations and/or multipath propagation). Moreover, the influence of the tracking error on system performance, in terms of variation of received energy per bit at the input of the data demodulator, has been determined. A real multipath indoor transmission channel with band limitations due to transmitter and receiver filters has been considered as an application example of the formulas described. In this context, both multipath components with delays shorter and longer than the chip time have been examined, and results have been compared with those achievable considering an ideal synchronisation on the first path

Comparative Evaluation of Carrier Frequency Offset Tracking Schemes for WiMAX OFDM Systems

J Gonzalez-Bayon — 2008-06-11T20:27:10-00:00

Signal Processing and Information Technology, 2007 IEEE International Symposium on (2007), pp. 479-484.

Tracking of the carrier frequency offset (CFO) is a crucial issue in the implementation of OFDM systems. Several tracking schemes have been proposed for the 802.11a (WiFi) or DVB-T standards, but almost no frequency tracking studies are available for the more recent 802.16-2004 (WiMAX) wireless communication standard. This work adapts two known tracking techniques, a classic pilot-based scheme and a decision-directed scheme based on two tracking loops, to the WiMAX standard. In addition, two new tracking techniques aimed at, either improving performance or reducing the required computational resources at no performance loss, are also presented: an alternative pilot-based scheme and a decision-directed approach based on a single tracking loop. A comparative evaluation of all these schemes for the WiMAX standard is presented for the first time for both Gaussian and Rayleigh channels. Results show that decision-directed schemes behave better with both types of channels for a target raw BER of 10-4. In fact, the classic pilot-based scheme provides very poor BER performance and it is clearly surpassed by the proposed pilot-based approach. Among the preferred decision-directed techniques, it is shown that the new proposed scheme requires less than half of the computational resources that the double loop scheme and obtains almost the same performance in realistic conditions.

Pilot-based channel estimation for OFDM systems by tracking the delay-subspace

O Simeone — 2008-06-09T19:36:32-00:00

Wireless Communications, IEEE Transactions on, Vol. 3, No. 1. (2004), pp. 315-325.

In orthogonal frequency division multiplexing (OFDM) systems over fast-varying fading channels, channel estimation and tracking is generally carried out by transmitting known pilot symbols in given positions of the frequency-time grid. The traditional approach consists of two steps. First, the least-squares (LS) estimate is obtained over the pilot subcarriers. Then, this preliminary estimate is interpolated/smoothed over the entire frequency-time grid. In this paper, we propose to add an intermediate step, whose purpose is to increase the accuracy of the estimate over the pilot subcarriers. The presented techniques are based on the observation that the wireless radio channel can be parametrized as a combination of paths, each characterized by a delay and a complex amplitude. The amplitudes show fast temporal variations due to the mobility of terminals while the delays (and their associated delay-subspace) are almost constant over a large number of OFDM symbols. We propose to track the delay-subspace by a subspace tracking algorithm and the amplitudes by the least mean square algorithm (or modifications of the latter). The approach can be extended to multiple input multiple output OFDM or multicarrier code-division multiple-access systems. Analytical results and simulations prove the relevant benefits of the novel structure.

A Novel Unambiguous Multipath Mitigation Scheme for BOC(kn, n) Tracking in GNSS

Sanghun Kim — 2008-06-03T18:59:27-00:00

Applications and the Internet Workshops, 2007. SAINT Workshops 2007. International Symposium on (2007), pp. 57-57.

Binary offset carrier (BOC) signal tracking is one of the challenging problems in future global navigation satellite systems (GNSS) including Galileo and global positioning system (GPS), because false lock could be generated in the tracking procedure due to multiple side-peaks in BOC autocorrelation. Multipath mitigation is another challenging problem in GNSS systems, because the presence of multi-path signals gives a range error. Recently, a novel tracking scheme for the BOC signal was proposed by Garin [8]. However, it can not completely resolve the ambiguity problem due to the false lock and has not enough multipath mitigation performance. Moreover, Garin¿s scheme is applicable to only BOC(n, n). In this paper, we propose a novel unambiguous multipath mitigation scheme. The proposed scheme is applicable to various BOC signals (i.e., BOC(kn, n)) and does not incur false lock point in the tracking procedure. In addition, the proposed scheme has appropriate multipath mitigation performance than traditional and Garin¿s schemes.

Extended tracking range delay-locked loop

A Wilde — 2008-06-02T07:14:33-00:00

Communications, 1995. ICC '95 Seattle, 'Gateway to Globalization', 1995 IEEE International Conference on, Vol. 2 (1995), pp. 1051-1054 vol.2.

In spread spectrum systems PN-code tracking is a crucial performance aspect. The delay-locked loop (DLL) is an appropriate device to guarantee fine synchronization. In this paper, a modified extended tracking range DLL is proposed. In the design of a DLL there is a tradeoff between tracking jitter and tracking range. The loop noise in an extended tracking range DLL is normally increased since more correlators are used. The jitter performance is improved by selecting the two strongest extended DLL branches. This modifies the extended DLL detector S-curve only slightly while reducing the noise power in the loop considerably

A noncoherent tracking loop with diversity and multipath interference cancellation for direct-sequence spread-spectrum systems

Wern-Ho Sheen — 2008-06-02T06:46:07-00:00

Communications, IEEE Transactions on, Vol. 46, No. 11. (1998), pp. 1516-1524.

A noncoherent tracking loop with diversity reception and multipath interference cancellation is proposed for direct-sequence spread-spectrum systems on frequency-selective multipath fading channels. The basic idea of the loop is to reproduce the multipath interference and remove it from the received signal, and then a path diversity is embedded in the loop to improve the loop performance. The tracking error performance of the loop is evaluated by linear analyses and computer simulations. Numerical results show that the proposed tracking loop outperforms the traditional delay locked loop and performs very well under all considered fading conditions

Joint Carrier Phase and Symbol Timing Recovery for PAM Systems

M Meyers — 2008-05-22T09:29:29-00:00

Communications, IEEE Transactions on [legacy, pre - 1988], Vol. 28, No. 8. (1980), pp. 1121-1129.

The detection of pulse amplitude modulation (PAM) carrier signals requires accurate symbol timing and carrier phase references. In most cases, it is desired to estimate these parameters directly from measurements on the received data signal. This paper adds to and unifies the theory of maximum likelihood [ML] estimation as applied to PAM timing and phase recovery. Several different estimation strategies are considered. Data-aided [DA] estimators are found which assume the transmitted data symbols are known at the receiver. Nondata-aided [NDA] estimators are found which require only knowledge of the statistics of the transmitted data symbols. Structures for estimation of symbol timing, carrier phase, and joint estimation of timing and phase are presented. The estimators are evaluated on the basis of their error variances. Relatively simple approximate expressions for these error variances are presented. These expressions allow the comparison of the effects of excess bandwidth, different modulation schemes, DA versus NDA recovery, and joint estimation versus estimation of only one parameter. A practical implementation of the ML estimator, termed a pseudo-maximum likelihood (PML) estimator, is proposed and analyzed. The performance of the PML estimator is shown to include a noise-independent, data-dependent jitter which dominates in many cases of practical interest.

Two novel automatic frequency tracking loops

S Anguirre — 2008-05-22T09:27:04-00:00

Aerospace and Electronic Systems, IEEE Transactions on, Vol. 25, No. 5. (1989), pp. 749-760.

Two automatic-frequency-control loops are introduced and analyzed in detail. The algorithms are generalizations of the well-known cross-product automatic-frequency-control loop with improved performance. The first estimator uses running overlapping discrete Fourier transforms (DFTs) to create a discriminator curve proportional to the frequency estimation error, whereas the second one preprocesses the received data and then uses an extended Kalman filter to estimate the input frequency. The algorithms are tested by computer simulations in a low carrier-to-noise-ratio (CNR) and highly dynamic environment. The algorithms are suboptimum tracking schemes with a larger frequency error variance compared to an optimum strategy, but they offer simplicity of mechanization and a CNR with a very low operating threshold

A Second-Order Frequency-Aided Digital Phase-Locked Loop for Doppler Rate Tracking

C Chie — 2008-05-22T09:26:06-00:00

Communications, IEEE Transactions on [legacy, pre - 1988], Vol. 28, No. 8. (1980), pp. 1431-1436.

A second-order digital phase-locked loop (DPLL) has a finite lock range which is a function of the frequency of the incoming signal to be tracked. For this reason, it is not capable of tracking an input with Doppler rate for an indefinite period of time. In this correspondence, an analytical expression for the hold-in time is derived. In addition, an all-digital scheme to alleviate this problem is proposed based on the information obtained from estimating the input signal frequency.

The Generalized Delay-Locked Loop

A Wilde — 2008-05-22T09:10:51-00:00

Wireless Personal Communications, Vol. 8, No. 2. (1998), pp. 113-130.

The delay-locked loop (DLL) is a synchronization device that is widely used for PN-code tracking in spread spectrum systems. The error detector characteristic (S-curve) of the DLL has a major impact on the performance. Using more than two correlators will extend the tracking range of the S-curve. The Generalized DLL (GenDLL) theory provides a concept to analyze a large class of DLL configurations including the classical DLL. The focus of the performance criteria is on tracking jitter and the mean time to lose lock (MTLL). It is shown that the MTLL can be considerably improved by using extended S-curves. However, the tracking jitter is increased by additional correlators. The tradeoff between the two criteria is explained. With the GenDLL theory loop configurations can be designed having both low tracking jitter and high loop robustness against loss of lock.

The performance of the all-digital data transition tracking loop using nonlinear analysis

A Mileant — 2008-05-22T08:58:49-00:00

Communications, IEEE Transactions on, Vol. 43, No. 234. (1995), pp. 1202-1215.

This paper describes the performance of the all digital data transition tracking loop (DTTL) with coherent and noncoherent sampling using nonlinear theory. The effects of few samples per symbol and of non-commensurate sampling and symbol rates are addressed and analyzed for perfectly square pulses as well as filtered pulses. Their impact on the probability density and variance of the phase error are quantified through computer simulations. It is shown that the performance of the all-digital DTTL approaches its analog counterpart when the sampling and symbol rates are noncommensurate (i.e., the number of samples per symbol is irrational). The phase error variance for an even number of samples per symbol is also shown to degrade compared to an odd number of samples per symbol

Performance analysis of digital delay lock loops in the presence of Doppler shift

Nan-Yang Yen — 2008-05-21T12:54:49-00:00

Communications, IEEE Transactions on, Vol. 44, No. 6. (1996), pp. 668-674.

This paper considers discrete time analyses of digital delay lock loops (DDLL), and presents the results of an investigation concerning the performance degradation due to Doppler. The performance measures evaluated include the steady-state timing error probability density function (PDF) and the mean time to lose lock. The linear approximations are also provided and compared to the numerical results and simulations. The delay lock loop is a well-known technique to track the pseudo-noise (PN) codes for spread spectrum systems. Under a severe Doppler environment, such as in the low Earth orbit (LEO) satellite communication, it will be difficult to track the PN code for the first-order loop. Since the digital systems are more compact, lower cost, and more stable than their analog counterparts, we focus our attention on the digital first and second order code tracking loops that suffer from severe Doppler

Performance analysis of digital delay lock loops in the presence of Doppler shift

Szu-Lin Su — 2008-05-21T12:54:47-00:00

Communications, 1995. ICC '95 Seattle, 'Gateway to Globalization', 1995 IEEE International Conference on, Vol. 3 (1995), pp. 1896-1900 vol.3.

The delay lock loop is a well-developed technique to track the pseudo-noise codes for spread-spectrum systems. In previous papers the first-order loop was analyzed in the absence of Doppler shift. However, under severe Doppler environment, such as low-earth-orbit (LEO) satellite communication, the tracking of PN code will be difficult for the first-order loop. This paper considers discrete time analyses of first- and second-order digital delay lock loops (DDLL), and presents the results of an investigation concerning the performance degradation due to Doppler. The performance measures evaluated include the steady-state timing error probability density function (pdf) and the mean time to lose lock. The measures are characterized in terms of the Doppler shift and the loop signal-to-noise ratio. Moreover, approximate expressions for the steady-state timing error probability density and the mean time to lose lock are also presented for the first- and second-order digital delay lock loops. The analyses are confirmed by numerical results and simulation

Optimum Performance of Suppressed Carrier Receivers with Costas Loop Tracking

M Simon — 2008-05-21T12:54:41-00:00

Communications, IEEE Transactions on [legacy, pre - 1988], Vol. 25, No. 2. (1977), pp. 215-227.

The performance of suppressed carrier receivers with Costas loop tracking is optimized by proper choice of loop arm filter bandwidth. In particular, it is shown that for a variety of passive arm filter types, there exists, for a given data rate and data signal-signal-to-noise ratio, an optimum filter bandwidth in the sense of minimizing the loop's squaring loss. For the linear theory case, this is equivalent to minimizing the loop's tracking jitter. When symbol synchronization is known, it is shown that by replacing the passive arm filters with active filters, i.e., integrate-and-dump circuits, one can acheive an improvement in carrier-to-noise ratio of as much as 4 to 6 dB depending on the passive arm filter type used for comparison and the value of data signal-to-noise ratio.

Analysis and Optimization of Correlative Code-Tracking Loops in Spread-Spectrum Systems

A Polydoros — 2008-05-21T12:54:39-00:00

Communications, IEEE Transactions on [legacy, pre - 1988], Vol. 33, No. 1. (1985), pp. 30-43.

The purpose of this paper is to apply the renewal theory approach for analyzing aperiodic finite<tex>S</tex>-curve code-tracking loops developed by Meyr [9] to the case of a noncoherent, arbitrary offset, early-late, delay-locked loop ("noncoherent δ-DLL"). The exact (renewal) approach is compared to the approximate (periodic-extension) approach of using the periodic<tex>S</tex>-curve or phase-locked loop theory, as well as to the linear theory developed herein for the aforementioned codetracking loop. Finally, loop optimization with respect to the offset δ is carried out according to certain performance criteria. The results indicate that, for low SNR, the exact and approximate theories could deviate significantly while, for high SNR, all three theories yield identical performance, as expected. Furthermore, it is shown that the optimal δ for both low and high SNR could differ from the commonly accepted choice<tex>delta = 1/2</tex>.

Acquisition and Tracking

2008-05-21T09:32:52-00:00

Phase-Locked Loops for Wireless Communications (2002), pp. 113-137.

Optimal GPS-Tracking Even in Case of Line-of-Sight Loss

Karl Kaindl — 2008-05-19T19:30:24-00:00

ION GPS/GNSS 2003 (2003)

Effects of gain and phase imbalance on sum-difference code tracking loop's performance in spread spectrum systems

Jeich Mar — 2008-05-15T17:46:37-00:00

Universal Personal Communications Record, 1997. Conference Record., 1997 IEEE 6th International Conference on, Vol. 2 (1997), pp. 371-375 vol.2.

The nonlinear renewal process approach (RPA) is applied to analyze the noncoherent sum-difference loop (SDL) with gain and phase imbalance for spread spectrum systems. In the analysis, the code acquisition boundary is equal to the branch offset, 0<δ&les;1. The results indicate that under phase imbalance, when δ&ges;0.5 and with gain balance, the values of the DC bias of the SDL are small and will not change with the loop signal-to-noise ratio (SNR); when δ<0.5 and with a low loop SNR, the DC bias becomes larger which will result in the SDL loss of lock. A larger branch offset may result in a higher mean-time-to-lose-lock (MTLL) for the SDL with gain and phase imbalance; however, the RMS tracking error has not obviously changed with the increasing branch offset. Furthermore, it is shown that in case where the early and late branch of the SDL can not be implemented with equal gain, one can get better performance results by putting the arm with smaller gain in the late branch of the SDL

Modified tracking loop for DS spread spectrum systems

F Nouvel — 2008-05-15T17:46:36-00:00

Electronics Letters, Vol. 29, No. 21. (1993), pp. 1827-1828.

A nonconventional pseudo-noise (PN) code tracking loop for direct sequence (DS) spread spectrum systems is presented. It solves problems of component imbalance while maintaining hardware simplicity

A Modified PN Code Tracking Loop: Its Performance Analysis and Comparative Evaluation

R Yost — 2008-05-15T17:46:35-00:00

Communications, IEEE Transactions on [legacy, pre - 1988], Vol. 30, No. 5. (1982), pp. 1027-1036.

A modified noncoherent PN code tracking loop (MCTL) has been previously presented by the authors [3]. The loop was shown to have the hardware simplicity of the tau-dither loop and a tracking performance superior to the traditional delay-locked code tracking loop (TCTL). Further work conducted herein expands on these previous results by considering the band-limiting effects of the bandpass arm filters on the performance of the MCTL. It will be shown that an even greater improvement in tracking performance is experienced by the MCTL over the TCTL when such effects are included. Furthermore, it was mentioned in [3] that a specific<tex>S/N</tex>existed below which the MCTL acquisition behavior was superior to the TCTL and above which its behavior was inferior. The bandlimiting effects will be shown to have a more deleterious effect on the TCTL and, as such, the crossover<tex>S/N</tex>will increase, thus enhancing the comparable capabilities in favor of the MCTL. This paper also discusses the implementation sensitivities to hardware gain and phase imbalance by expanding on the noise-free work in [3] to include the noisy case.

A new tracking loop for direct sequence spread spectrum systems on frequency-selective fading channels

Wern-Ho Sheen — 2008-05-15T17:35:11-00:00

Communications, IEEE Transactions on, Vol. 43, No. 12. (1995), pp. 3063-3072.

A new tracking loop is proposed for direct-sequence spread-spectrum signaling on a frequency-selective fading channel. By exploiting the inherent multipath diversity of the channel, the new tracking loop overwhelmingly outperforms a traditional noncoherent delay-locked loop (DLL) for all cases under consideration. Linear and nonlinear (based on the renewal process approach) methods are employed to analyze the new tracking loop with perfect channel estimation. Although the analytical methods are developed under the guise of a slowly time-varying channel, the analytical and simulation results show close agreement for channels with a code Doppler shift βD as large as 0.117598 (Doppler shift fD=83 Hz). Consequently, the analytical methods, especially those based on linear methods, can be easily employed to characterize the new tracking loop. The performance degradation caused by imperfect channel estimation is determined by computer simulations. Over a range of signal-to-noise-ratios (SNRs) of practical interest, the simulation results show a degradation of about 2 dB and 1 dB for βD=0.0117598 (fD=8.3 Hz) and βD =0.117598 (fD=83 Hz), respectively

Frequency offset tracking in OFDM based on multicarrier PLL

MR Dacca — 2008-05-13T10:45:38-00:00

MILCOM 2000. 21st Century Military Communications Conference Proceedings, Vol. 2 (2000), pp. 912-916 vol.2.

A novel algorithm for frequency offset tracking in orthogonal frequency-division multiplexing (OFDM) is proposed. The algorithm is based on decision-feedback and assumes differential reception. It makes it possible to track the frequency shift of an OFDM signal transmitted over a frequency dispersive channel. The channel is assumed to be time invariant for each OFDM sub-carrier. The processing is performed in the base band part and does not require any processing in the RF stage. A novel multicarrier phase locked loop (MPLL) for frequency shift tracking is described. The MPLL explores some unique features of the OFDM. A low-complexity real-time algorithm is obtained. It is shown that a receiver based on the suggested algorithm works well even for a relatively low signal to noise ratio (SNR) and its performance closely approaches that of differential detection without a frequency offset. We show that the proposed frequency offset compensation may be used in a tracking mode in OFDM receivers and may be implemented for high frequency (HF) communication, digital audio broadcasting, underwater acoustic communications or digital subscriber lines

Anti multipath cellular radio location for DS/CDMA systems using a novel EKF subchip RAKE tracking loop

E Fishler — 2008-05-09T15:42:49-00:00

Military Communications Conference Proceedings, 1999. MILCOM 1999. IEEE, Vol. 2 (1999), pp. 1328-1332 vol.2.

This paper discusses an improved method for localization in a DS-CDMA based cellular-phone communication link. This method suggests an optimization for code synchronization, which allows for TDOA (time difference of arrival) estimations to be solved for the position of a mobile phone. It is known that the time delay of a received DS signal, derived from the classical DLL, may express severe timing errors due to multipath effects. A new anti multipath multi-tracking extended Kalman filter loop is shown to achieve far better results especially in the environment of specular multipath. Specifically, this new loop minimizes the errors due to multipath components by letting the EKF decide upon the best weights of its sub-chip processing branches, resulting in a RAKE-like tracking loop. This loop tracks not only the line of sight path, but also the other multipath components as well as their power and phase. It is shown that the implementation of this technique converges to the classical non-coherent code tracking DLL structure when no multipath is assumed, but results in a new and efficient tracking loop structure in the more realistic fading channel case. The application of this technique to the EIA IS-95 system is considered, where accurate location estimations as well as power management utilities are treated

Real-time acquisition and tracking for GPS receivers

A Alaqeeli — 2008-05-07T06:24:49-00:00

Circuits and Systems, 2003. ISCAS '03. Proceedings of the 2003 International Symposium on, Vol. 4 (2003), pp. IV-500-IV-503 vol.4.

Current GPS receivers spend much time in base-band processing, performing acquisition and tracking. This is due to the large number of required operations in the software-based signal processing. This paper presents a novel signal acquisition and tracking method that reduces the number of operations, simplifies hardware implementation and decreases the acquisition time. The implementation of this method in an FPGA provides very fast processing of incoming GPS samples that satisfies real-time requirements.

A modified phase error detector for frequency tracking in SISO/MIMO-OFDM systems

Steve Hsu — 2008-03-11T10:13:17-00:00

Vehicular Technology Conference, 2005. VTC-2005-Fall. 2005 IEEE 62nd, Vol. 3 (2005), pp. 1471-1474.

Carrier frequency acquisition and tracking for OFDM systems

M Luise — 2008-02-25T15:37:35-00:00

Communications, IEEE Transactions on, Vol. 44, No. 11. (1996), pp. 1590-1598.

We present and analyze a technique for fast acquisition and accurate tracking of the carrier frequency in orthogonal frequency division multiplexing (OFDM) receivers. The scheme is based on a data-aided frequency estimation algorithm. The presence of known symbol sequences periodically inserted in the OFDM frame allows the data demodulator to rapidly lock onto the carrier frequency during the acquisition phase, even in the presence of frequency offsets up to a few tenths of the overall signaling rate. Once acquisition is over, the circuit switches to a decision-directed mode to perform fine frequency tracking for reliable data demodulation. The algorithm performance is analyzed in terms of width of the lock-in frequency range and of lock-in probability in the acquisition mode, and of mean-square frequency estimation error in the tracking mode. Since OFDM is known to be extremely sensitive to carrier frequency errors, the impact of the carrier frequency synchronizer on the receiver error rate is also investigated

Design of an adaptive antenna array for tracking the source of maximum power and its application to CDMA mobile communications

Seungwon Choi — 2008-02-24T13:43:24-00:00

Antennas and Propagation, IEEE Transactions on, Vol. 45, No. 9. (1997), pp. 1393-1404.

This paper presents an alternative method of adaptive beamforming. Under an assumption that the desired signal is large enough compared to each of interfering signals at the receiver, which is preconditionally achieved in code division multiple access (CDMA) mobile communications by the chip correlator, the proposed technique provides for a suboptimal beam pattern that increases the signal-to-noise/signal-to-interference ratio (SNR/SIR) and eventually increases the capacity of the communication channel. The main advantages of the new technique are: (1) the procedure requires neither reference signals nor a training period; (2) the signal intercoherency does not affect the performance or complexity of the entire procedure; and (3) the total amount of computation is tremendously reduced compared to that of most conventional beamforming techniques such that the suboptimal beam pattern is produced at every snapshot on a real-time basis. In fact, the total computational load for generating a new set of weights including the update of an N-by-N autocovariance matrix is O(3N2+12N). It can further be reduced down to O(11N) by approximating the matrix with the instantaneous signal vector

PN acquisition and tracking performance in DS/CDMA systems with symbol-length spreading sequences

WR Braun — 2008-02-18T15:43:53-00:00

Communications, IEEE Transactions on, Vol. 45, No. 12. (1997), pp. 1595-1601.

Direct sequence spread spectrum code-division multiple-access (DS/CDMA) is receiving increasing attention for cellular communications systems. When the users are synchronized and special symbol-length sequences, such as Gold codes, are used, the mutual interference can be substantially reduced relative to a system with very long or purely random spreading sequences. It is shown that this approach degrades the performance of the code phase acquisition and tracking, however. This effect prevents the system from acquiring and tracking long before the data detection is affected by the multiuser interference

The effect on tracking loop performance when using the efficient search method for fast fine frequency acquisition

Young Cho — 2008-02-14T16:24:22-00:00

Control, Automation and Systems, 2007. ICCAS '07. International Conference on (2007), pp. 517-522.

When implementing real-time software based GNSS receiver, the accurate and fast signal acquisition and tracking method is more necessary than the hardware based receiver owing to lots of computation time. Generally, in the software based GNSS receiver, parallel code phase signal acquisition method using FFT has been used. But it has the defect of the limited frequency resolution according to input data’s length. Considering the carrier frequency resolution must be about tens of Hz in order to perform the tracking loop correctly, the fine frequency acquisition method to minimize the computation time should be necessary to overcome this limitation. Also the examination whether the method will enhance the tracking loop’s performance and cause the reduction of computation time should be necessary. To evaluate these necessities, in this paper, the efficient search method for fine frequency acquisition will be suggested and tested. Furthermore, the effect on signal tracking loop, when the result of signal acquisition obtained by the suggested method is applied, will be analyzed.

Digital Code Tracking Loops Over Frequency-Selective Fading Channels

TM Wu — 2008-02-09T00:59:42-00:00

Communications, 2007. ICC '07. IEEE International Conference on (2007), pp. 5246-5251.

A robust PN code tracking algorithm for frequency selective Rayleigh-fading channels

M El-Tarhuni — 2008-02-09T00:47:47-00:00

Wireless Communications, IEEE Transactions on, Vol. 3, No. 4. (2004), pp. 1018-1023.

In this letter, we propose a new tracking scheme that is robust against multipath fading for pseudonoise (PN) code tracking in direct-sequence-spread spectrum systems. The proposed scheme employs an adaptive filter whose taps are adapted using a block least-mean square algorithm and it results in minimizing the effect of multipath interference on the tracking performance. We show that the mean-squared tracking error performance of the proposed scheme is not affected by the presence of closely spaced paths (e.g., one to three chips), unlike that of conventional delay locked loops. We also show that the tap-weight distribution of the filter provides accurate estimates of the multipath delays. For example, at E/sub b//N/sub 0/=5 dB, 98% of the time the path estimates lie within one sample (1/5 of a chip) from the actual delays. Furthermore, simulation results suggest that multipath delays over a wide range of terminal speeds can be tracked successfully. The proposed scheme is well suited for wideband code-division multiple-access systems where a large number of closely-spaced multipath components need to be tracked and used in RAKE combining.

Numerical simulation of GNSS code tracking loops using Euler-Maruyama method

JL Garrison — 2008-02-03T22:58:07-00:00

Electronics Letters, Vol. 41, No. 15. (2005), pp. 868-869.

The Euler-Maruyama (EM) method for the numerical integration of stochastic differential equations is applied to simulate tracking loops for Global Navigation Satellite System (GNSS) signals. Use of a large step size and two-point pseudorandom numbers allow for computationally efficient simulation of statistics such as the mean time to lose lock (MTLL). To demonstrate this method, non-coherent delay-lock loops are simulated using the EM method. The MTLL computed from an ensemble of 50 sample paths is compared to a numerical integration of the Fokker-Planck equation. The dependence of computational time and error on step size is evaluated.

What is the price paid for superimposed training in OFDM?

Ning Chen — 2007-11-28T11:36:26-00:00

Acoustics, Speech, and Signal Processing, 2004. Proceedings. (ICASSP '04). IEEE International Conference on, Vol. 4 (2004), pp. iv-421-iv-424 vol.4.

Orthogonal frequency division multiplexing (OFDM) transmission with superimposed training is considered in this paper. The superimposed training scheme is promoted for its high bandwidth efficiency, low computational complexity, and possibly improved power amplifier (PA) efficiency. Channel equalization is also straightforward thanks to the OFDM structure. By analyzing the peak-to-average power ratio (PAR) of the superimposed OFDM signal and utilizing a peak power constraint, we demonstrate that it is possible to lose a little in the information signal power, but gain a lot in the power that is devoted to channel sounding.

Multi-input multi-output fading channel tracking and equalization using Kalman estimation

C Komninakis — 2007-11-28T10:36:58-00:00

Signal Processing, IEEE Transactions on [see also Acoustics, Speech, and Signal Processing, IEEE Transactions on], Vol. 50, No. 5. (2002), pp. 1065-1076.

This paper addresses the problem of channel tracking and equalization for multi-input multi-output (MIMO) time-varying frequency-selective channels. These channels model the effects of inter-symbol interference (ISI), co-channel interference (CCI), and noise. A low-order autoregressive model approximates the MIMO channel variation and facilitates tracking via a Kalman filter. Hard decisions to aid Kalman tracking come from a MIMO finite-length minimum-mean-squared-error decision-feedback equalizer (MMSE-DFE), which performs the equalization task. Since the optimum DFE for a wide range of channels produces decisions with a delay Δ > 0, the Kalman filter tracks the channel with a delay. A channel prediction module bridges the time gap between the channel estimates produced by the Kalman filter and those needed for the DFE adaptation. The proposed algorithm offers good tracking behavior for multiuser fading ISI channels at the expense of higher complexity than conventional adaptive algorithms. Applications include synchronous multiuser detection of independent transmitters, as well as coordinated transmission through many transmitter/receiver antennas, for increased data rate

Neural networks based approach for fine tracking in satellite navigation systems

M Musso — 2007-11-22T15:28:00-00:00

Recent Advances in Space Technologies, 2005. RAST 2005. Proceedings of 2nd International Conference on (2005), pp. 369-373.

In this paper a novel method to solve the fine synchronization problem in GLASS receivers is presented. In fact the extended evolution of GLASS-based applications will imply the growth of fast and precise navigation systems. The aim of this study is to found an alternative solution to the classical non-coherent delay lock loop. In particular, the proposed method, based on self organizing map (SOM) a particular type of neural networks, allows to improve the performances in multipath channel.

RADAR: an in-building RF-based user location and tracking system

P Bahl — 2005-07-16T07:32:08-00:00

INFOCOM 2000. Nineteenth Annual Joint Conference of the IEEE Computer and Communications Societies. Proceedings. IEEE, Vol. 2 (2000), pp. 775-784 vol.2.

The proliferation of mobile computing devices and local-area wireless networks has fostered a growing interest in location-aware systems and services. In this paper we present RADAR, a radio-frequency (RF)-based system for locating and tracking users inside buildings. RADAR operates by recording and processing signal strength information at multiple base stations positioned to provide overlapping coverage in the area of interest. It combines empirical measurements with signal propagation modeling to determine user location and thereby enable location-aware services and applications. We present experimental results that demonstrate the ability of RADAR to estimate user location with a high degree of accuracy

GRANADA validation of optimized Multiple Gate Delay structures for Galileo SinBOC(1,1) signal tracking

Xuan Hu — 2007-11-14T19:19:57-00:00

Telecommunications, 2007. ITST '07. 7th International Conference on ITS (2007), pp. 1-5.

Multipath is an issue of paramount importance in the GNSS context, and the dominant error source for the Delay Lock Loop (DLL) used for code tracking. This paper introduces an optimized Multiple Gate Delay (MGD) code tracking implementation in the modified GRANADA Bit-true Software Receiver Simulator. Then the tracking performance of the optimized MGD structure is presented via GRANADA simulation results. This tracking performance is also compared with the tracking performance of High Resolution Correlator (HRC) and of the narrow correlator or narrow Early-Minus-Late (nEML) structures. The tracking performance criteria include Multipath Error Envelopes (MEEs) and Root Mean Square Error (RMSE) for both multipath static channels and fading channels. It is shown that the optimized MGD structure has a better performance than nEML and HRC in the multipath channels, and that the GRANADA Bit-true Software Receiver Simulator is a useful tool for testing the performance.

A DS/SS predictive PN code tracking loop using a Kalman filter

Takashi Shono — 2007-11-14T17:47:46-00:00

Electronics and Communications in Japan (Part I: Communications), Vol. 83, No. 12. (2000), pp. 71-83.

We present a new code tracking loop, which is stable and has high capability of tracking, for DS/SS communication systems between aircraft and ground base stations. The proposed loop uses delay estimators combining the modified code tracking loop (MCTL) with the Kalman filter, which is usually used to track the position of an aircraft, but is used to estimate the propagation delay of the spreading sequence in our loop. We call the proposed loop the predictive PN code tracking loop (PCTL). The estimated delay-controlled device transforms the propagation delay obtained by the Kalman filter to the adaptive signal and inputs it to the MCTL discretely through the operational circuit. The PCTL can revise the degradation in the tracking performance of the MCTL under the constraint of Doppler effects and the channel noise. The tracking performance of the PCTL is investigated and compared with that of the MCTL by computer simulations. It is shown that our proposed system has a higher code tracking performance than the MCTL from the viewpoint of tracking jitter. © 2000 Scripta Technica, Electron Comm Jpn Pt 1, 83(12): 71-83, 2000

Multipath Limitations on Low-Angle Radar Tracking

AV Mrstik — 2007-10-30T10:53:51-00:00

Aerospace and Electronic Systems, IEEE Transactions on, Vol. AES-14, No. 1. (1978), pp. 85-102.

This paper investigates the problem of tracking targets at a low elevation angle in the presence of specular and diffuse multipath. Quantitative estimates are derived of the elevation angles, and hence, range, at which targets of specified height can be accurately tracked. A parametric approach is followed in which the long-standing uncertainty of how terrain forward-scatters at low grazing angles is recognized at the outset. Particular attention is given to the effects of target motion which permit rejection of multipath components falling outside the radar tracker's passband. The results are presented in a form which can be readily applied to a spectrum of radar trackers with differing requirements. The limited experimental ental data on the specular and diffuse scattering parameters for several generic types of terrain are applied to estimate the significance of multipath under different situations and to indicate specific areas in which additional experimental data are critically needed.

Tracking low elevation targets in the presence of multipath propagation

Y Bar-Shalom — 2007-10-30T10:52:19-00:00

Aerospace and Electronic Systems, IEEE Transactions on, Vol. 30, No. 3. (1994), pp. 973-979.

A tracking algorithm based on a measurement model of the multipath propagation effects on the elevation angle measurements is presented. This algorithm does not depend on the specific signal processing and the prevailing environmental conditions. The results of simulations based on several scenarios are presented. The signal processing model used to generate the elevation measurements of a low-flying target with multipath effects is also described. This mode incorporates a spherical Earth and finite target range in the geometry of reflection. The algorithm clearly indicates when the measurements are degraded, in which case it automatically increases the variance of the altitude estimate

A tutorial on particle filters for online nonlinear/non-Gaussian Bayesian tracking

MS Arulampalam — 2005-12-09T09:18:13-00:00

Signal Processing, IEEE Transactions on [see also Acoustics, Speech, and Signal Processing, IEEE Transactions on], Vol. 50, No. 2. (2002), pp. 174-188.

Increasingly, for many application areas, it is becoming important to include elements of nonlinearity and non-Gaussianity in order to model accurately the underlying dynamics of a physical system. Moreover, it is typically crucial to process data on-line as it arrives, both from the point of view of storage costs as well as for rapid adaptation to changing signal characteristics. In this paper, we review both optimal and suboptimal Bayesian algorithms for nonlinear/non-Gaussian tracking problems, with a focus on particle filters. Particle filters are sequential Monte Carlo methods based on point mass (or "particle") representations of probability densities, which can be applied to any state-space model and which generalize the traditional Kalman filtering methods. Several variants of the particle filter such as SIR, ASIR, and RPF are introduced within a generic framework of the sequential importance sampling (SIS) algorithm. These are discussed and compared with the standard EKF through an illustrative example