Multiple Parameter Estimation With Quantized Channel Output

We present a general problem formulation for optimal parameter estimation based on quantized observations, with application to antenna array communication and processing (channel estimation, time-of-arrival (TOA) and direction-of-arrival (DOA) estimation). The work is of interest in the case when low resolution A/D-converters (ADCs) have to be used to enable higher sampling rate and to simplify the hardware. An Expectation-Maximization (EM) based algorithm is proposed for solving this problem in a general setting. Besides, we derive the Cramer-Rao Bound (CRB) and discuss the effects of quantization and the optimal choice of the ADC characteristic. Numerical and analytical analysis reveals that reliable estimation may still be possible even when the quantization is very coarse.Comment: 9 pages, 9 figures, International ITG Workshop on Smart Antennas - WSA 2010, Bremen, German

Simulation of Multi-element Antenna Systems for Navigation Applications

The application of user terminals with multiple antenna inputs for use with the global satellite navigation systems like GPS and Galileo becomes more and more attraction in last years. Multiple antennas may be spread over the user platform and provide signals required for the platform attitude estimation or may be arranged in an antenna array to be used together with array processing algorithms for improving signal reception, e.g. for multipath and interference mitigation. In order to generate signals for testing of receivers with multiple antenna inputs and corresponding receiver algorithms in a laboratory environment a unique HW signal simulation tool for wavefront simulation has been developed. The signals for a number of antenna elements in a flexible user defined geometry are first generated as digital signals in baseband and then mixed up to individual RF-outputs. The paper describes the principle function of the system and addresses some calibration issues. Measurement set-ups and results of data processing with simulated signals for different applications are shown and discussed

Evaluation of GPS L5 and Galileo E1 and E5a Performance for Future Multi Frequency and Multi Constellation GBAS

In this paper, we show a performance analysis of different signals from the new Galileo satellites in the E1 and E5a frequency bands as well as GPS L5 signals in DLR’s experimental Ground Based Augmentation System (GBAS). We show results of noise and multipath evaluations of the available Galileo satellites and compare their performance to the currently used GPS L1 and the new GPS L5 signals which were presented in a recent paper. The results show that the raw noise and multipath level of Galileo signals is smaller than of GPS. Even after smoothing, Galileo signals perform somewhat better than GPS and are less sensitive to the smoothing time constant. Another issue to be considered in a future multi frequency system is inter-frequency bias. These biases differ between satellites and depend on satellite and receiver hardware, but they can be determined a priori. With known receiver and antenna configurations, it is possible to correct for these biases and avoid errors introduced by different hardware in the airborne receiver and GBAS ground system. A residual uncertainty associated with the bias correction has to be taken into account. This can be modelled as part of σ_(pr\_gnd)

Effect of Multipath on Code-Tracking Error Jitter of a Delay Locked Loop

It is very well known that multipath propagation is a major source of error for code and carrier phase measurement performed by a GNSS receiver. The presence of multiple reflections confounds the receiver and the estimation of the time delay will carry a bias dependant on the propagation channel. While this issue has been addressed in a certain number of works, there is another aspect that does not seem to have been investigated: the tracking error jitter alteration. Indeed in assessing the performance of an estimator, the mean value of the estimation error is as important as the variance, which indicates how the error is statistically distributed around its mean value. The variance of the tracking error in the single path scenario has been determined in a single path scenario, but in a multipath environment these results are no more valid. The objective of this work is to investigate the effect of multipath on the tracking error variance, adding a useful tool in the evaluation of performance of GNSS receiver. Analytical results will be presented for a static multipath scenario, and multipath mitigation techniques, as the Narrow Correlator and the Double Delta Correlator, thought with the intention of reducing the multipath bias, will be analysed and compared from this new perspective

Staggered Interplex

In this paper we present a modification of the interplex scheme, which allows to increase the power efficiency. The proposed method consists in introducing a constant time offset for each signal component, in order to maximise the power at the output of the receive matched filter. With the chosen high power amplifier (HPA) setup, this technique improves the receive power efficiency by 2-3% without any change in the transmitter/receiver hardware

Systematic Approach to Optimum Chip Pulse Shape Design

In this work we establish a systematic approach to design optimum chip pulse shapes for DS-CDMA systems which are absolutely bandlimited, whose energy is mainly concentrated in one chip duration, and thatminimize the Cramer-Rao lower bound for the time-delay. The proposed methodology makes it possible to formulate the problem of designing optimum chip pulse shapes in terms of achieving a trade-off between synchronization accuracy and acquisition and tracking robustness as an optimization problem. This methodology is based on the prolate spheroidal wave functions (PSWF), which enable to transform the primal variational problem into the dual, tractable parametric optimization problem. This work shows the interesting capabilities of the presented signal design approach for DS-CDMA systems. Two design examples for signal design are shown for global navigation satellite systems (GNSS) considering different requirements and constraints

Evolution of Interplex Scheme with Variable Signal Constellation

In this paper we present a modification of a multiplexing scheme for DS-CDMA signals, known as interplex scheme. The interplex allows to map several binary DS-CDMA signals onto a constant envelope signal, resulting in a signal that can be efficiently amplified. In order to obtain a constant envelope constellation, some additional power is transmitted that is not used for data transmission. This so called inter-modulation (IM) power can be too much compared to the useful power or the High Power Amplifier (HPA) non-linearities are not so severe to demand a perfectly constant envelope signal. The basic idea of this work is to adapt the interplex signal to the HPA at hand

GNSS Signal Design Approach Considering Receiver Performance

In this work we establish a systematic approach to design optimum chip pulse shapes for DS-CDMA systems which are absolutely band-limited, whose energy is mainly concentrated in one chip duration, and that minimize the Cramer-Rao lower bound for the time-delay. The proposed methodology makes it possible to formulate the problem of designing optimum chip pulse shapes in terms of achieving a trade-off between synchronization accuracy and acquisition and tracking robustness as an optimization problem. Additionally, spectral separation to non-interoperable signals in the same band is considered. This methodology is based on the prolate spheroidal wave functions (PSWF), which enable to transform the primal variational problem into the dual, tractable parametric optimization problem. This work shows the interesting capabilities of the presented signal design approach for DS-CDMA systems. This methodology is further developed according to the needs of Galileo-2 signal design

Spreading Code Design for a MC-CDMA Based GNSS Pilot Signal

MC-CDMA can represent an alternative to classical DS-CDMA for the design of GNSS ranging signals. A first requirement MC-CDMA signals must fulfill is that their generation on a satellite payload be feasible. It is well known, indeed, that multicarrier signals have a high Peak-to-Average-Power-Ratio (PAPR) and GNSS signals, as well as other signals used in satellite communications, must have PAPR values much lower than values usually considered acceptable in other applications. Therefore, maintaining the PAPR of a MC-CDMA ranging signal within acceptable limits is a fundamental issue in any signal GNSS signal design using a multicarrier technique. The main contribution of this work is to propose a way of designing a MC-CDMA pilot signal based on Huffman codes. Such approach allows to shape the autocorrelation (or equivalently the power spectrum) of the pilot signal according to the specific needs of a GNSS service, guaranteeing arbitrary small PAPR values in all cases