Paul Fortier

Multidimensional signal sets through the shell construction for parallel channels

The authors derive a procedure to send r bits on M parallel channels. A decomposition of the best constellation in Z/sup M/+(1/2, . . ., 1/2) is given in terms of the cross-products of lower dimensional shells of points. The proposed scheme can be used with good known coset codes to provide an alternate method of coded modulation. The results indicate that one can get good shaping gains for low encoder complexity. The method is also generalized for channels with unequal gains. The authors also find a significant performance advantage at fixed shaping gain, in certain cases, with respect to the recent Voronoi constellations in terms of peak-to-average power and constellation expansion. >

Information Theory and Applications II

Funding sources: NSF, DARPA Acknowledgements: Imre Csiszár, Chunxuan Ye, Sirin Nitinawarat, Himanshu Tyagi, Shun Watanabe, Ankur Srivastava •Multiuser information and coding theory. •Reliable communication over uncertain channels. •Information theoretic security. •Optical communication theory. •Communication networks. •Information theory and statistics. •Algorithm design for sampling rate distortion. •Function computation over networks. •Interactive communication for secrecy and privacy.

Performance analysis of a COFDM/FM in-band digital audio broadcasting system

In this paper, we present a performance analysis of a coded orthogonal frequency division multiplexing DAB system that is power multiplexed over a commercial FM station. We model the mobile channel with a time-frequency scattering function. Results show that the performance of the FM demodulator is crucial, since the level of the residual FM signal has a strong influence on the BER performance of the COFDM system. As with other mobile communication systems, the use of interleaving greatly enhances the performances.

Systematic design of pipelined recursive filters

Systematic design of pipelined recursive filters is presented. The procedure is based on a multiplication algorithm which generates the result with most significant digit first. Since the latency of such a multiplier is low, a reduced number of pipelining delays may be introduced in the reduction loop, resulting in a high sampling rate. The implementation obtained exhibits minimum hardware and ensures minimum latency. It is shown that its flexibility allows, on one hand, the ability to choose freely the number system radix and, on the other hand, the interleaving of two multiplier arrays into one. This is illustrated by the realization of a second-order all-pole filter, operating in a radix-4 representation and using only one array to perform two multiplications. In this way, long interconnections are avoided and denser and more regular layout is achieved. It turns out that the design procedure can also be applied successfully to various types of realization where multiplications are required. >

New cross-correlation results for multi-rate CDMA

Support of multiple data services can be accomplished via code division multiple access (CDMA) with a constant chip rate, but variable data rates. We present exact equations for the cross-correlation of codes in a multiple-data rate system, and thus equations for the multiple access interference (MAI) and bit error rate (BER). Previous analysis has found the EER using the mean of the MAI assuming codes are truly random sequences. We show that Gold and Kasami sequences have a cross-correlation with a distribution closely approximated by a Gaussian one, and present confidence intervals to quantify the performance under the random code assumption.

A new faster and simpler systolic structure for IIR filters

A bit-level systolic array architecture is presented for implementing infinite impulse response (IIR) filters. The topology is regular and modular, which makes the VLSI design easier. This realization has simpler hardware and a faster iteration period in comparison with a previous realization. In this case, the single coefficient of a one-pole filter covers the entire range of stability without increasing the array delay. Conventional full adders, multiplexers, and latches are the only type of base cell to be used in the array.<<ETX>>

Mechanical Vibration Analysis Using an Optical Sensor

A laser-based contactless displacement measurement system developed at the National Optics Institute is used for data acquisition to analyze the mechanical vibrations exhibited by vibrating structures and machines. The analysis of these vibrations requires a number of signal processing operations which include the determination of the system conditions through a classification of various observed vibration signatures and the detection of changes in the vibration signature in order to identify possible trends. This information is also combined with the physical characteristics and contextual data (operating mode, etc.) of the system under surveillance to allow the evaluation of certain characteristics like fatigue, abnormal stress, life span, etc., resulting in a high level classification of mechanical behaviours and structural faults according to the type of application. The aim of this paper is to introduce the problem, the instrumentation, and the requirements in terms of statistical signal processing.

Optimal detection of QAM in a man-made noise environment

It is known that in the personal communication systems environment, additive noise is not Gaussian. Experimental studies show that this type of noise obeys the class A Middleton man-made noise statistics. The influence of such noise is very severe on the probability error rate for a matched filter detector. To improve the detection performance, a non-linear detector should be used. This structure is based on the maximum likelihood approach which exploits multiple samples of the incoming signal. The improvement has been established by Spaulding and Middleton (1977) for the binary case. This paper generalizes this approach to M-ary signal detection, namely M-QAM, which is the most popular scheme in practice.

A study of turbo codes for multilevel modulations in Gaussian and mobile channels

In this paper, we present simulation results for a system combining turbo codes and multilevel modulation. This scheme is shown to be an excellent solution when it comes to transmission over bandlimited channels. Its performance in mobile radio channels can be improved using OFDM.

Influence of phase error on M-QAM demodulation in a non-Gaussian environment

This paper considers the influence of a deterministic phase error for coherent M-QAM demodulators in a non-Gaussian environment; the latter is modeled as a combination of a white Gaussian process and a filtered Poisson process whose enveloped amplitude obeys the Rayleigh distribution. General results show that when approaching the critical limit, the symbol error rate quickly reaches a plateau having a relatively large width.