Naïm Batani

Convolutional self doubly orthogonal codes for iterative decoding without interleaving

We present a novel turbo error control technique which circumvents both the complexity and latency shortcomings of the usual turbo codes. It differs from usual turbo coding techniques as if uses single encoder and a single decoder. The technique is based on a novel class of orthogonal threshold decodable codes called convolutional self doubly orthogonal codes (CSO/sup 2/C) which do not require interleaving.

On Extra Combinational Delays in SRAM FPGAs Due to Transient Ionizing Radiations

This paper presents a new experimental setup (to our knowledge, the first ever) and results obtained with that setup from which we report extra combinational delays in an SRAM FPGA (Virtex-5) due to transient ionizing radiations. The results, obtained by proton irradiation at the TRIUMF laboratory, show that our setup can detect extra combinatorial delays as small as 40 ps, and that delays of more than 400 ps can affect the targeted FPGA. These results strongly suggest that delay faults can potentially be induced by transient ionizing radiations.

Performance analysis of direct sequence spread spectrum system with transmitted code reference on quadrature carrier

The performance of a direct-sequence spread-spectrum system with a transmitted code reference on quadrature carrier and multiplicative despreading in the receiver is examined. The system bit-error-rate performance when the desired signal is imbedded in additive white Gaussian noise is analyzed. Analytical expressions are derived and numerical results are used to compare the system performance to that of standard direct-sequence spread-spectrum systems with a correlation receiver. The system performance is also compared to that of a binary phase shift keying spread spectrum system with transmitted code reference.<<ETX>>

Performance analysis of direct sequence spread spectrum system with transmitted code reference

The performance of a direct-sequence spread-spectrum system with a transmitted code reference and multiplicative despreading in the receiver is addressed. System bit error-rate (BER) performance when the desired signal is imbedded in additive white Gaussian noise (AWGN) is analyzed. Analytical expressions are derived, and numerical results are used to compare the system performance to standard direct-sequence spread-spectrum with a correlation receiver. The following conclusions are drawn from the analysis: (1) The bit error probability of the transmitted reference system in AWGN is much worse than that of a standard system. (2) The transmitted reference spread spectrum system does not require the use of code synchronization circuitry, but the cost of this lower complexity is reduced performance.<<ETX>>

On a complete simulation model for the design of high-speed digital radios

This paper describes a complete digital radio system model which takes into account the effects of most degradations due to channel conditions and equipment imperfections. System parameters which are taken into consideration include, but are not limited to, the following: modulator imbalance, filter frequency responses, power amplifier nonlinearities, carrier and symbol timing recovery loops, and synthesizer phase noise. The parameters for each module in the radio can be varied, and the end-to-end performance computed. Furthermore, a novel semianalytic method is developed for the purpose of speeding up the simulation leading to the calculation of the bit error rate (BER) versus E/sub b//N/sub o/ for the radio model. This novel technique, when compared with classical semianalytic methods, provides 1 dB improvement in the accuracy of the simulation results. The model accurately predicts the radio performance as measured by BER versus E/sub b//N/sub o/, dispersive fade margin, transmitted frequency spectrum, and transient acquisition responses. Simulation results for 16 QAM and OQPSK systems were compared to measurements on two physical radios. The accuracy of the simulation results was found to be within 0.1 dB in E/sub b//N/sub o/ at a BER of 10/sup -6/ without the RF portions and between 0.2 and 0.45 dB for a complete radio system.

Increasing the rate of wireless link when multiple QoS traffics are considered

This document provides a system analysis for hitless flexible data rate adapted to the received power variation with fixed spectrum. In our investigation, we are interested in digital line-of-sight (LOS) microwave links. The channel fading state, the grade of service and the adaptive modulation scheme are examined. Essentially, the flexible communication scheme consists in modifying, from one frame to the next, the modulation level used to communicate on a wireless link. The radio thus provides for significant capacity gains if traffic streams requiring different quality of service are being communicated. Most significant scenarios are considered and quantified to obtain a realistic analysis of the grades of services allocated to each traffic stream. We show as an example, that a 25 Mbit/s carrier grade link (99.9995% availability) may be modified into the sum of a 25 Mbit/s carrier grade link with a 100 Mbit/s data link of 99.9% availability.

Fuzzy learning vector quantization generation of codebooks

A modification of the learning vector quantization (LVQ) method used for the generation of codebooks is presented. It retains the simplicity of the LVQ method while eliminating the non uniform spatial distribution of the prototype vectors which could result from an inadequate choice of the input signal sequence and/or from the initial choice of the prototype vectors. The method is based upon the segmentation of the input vector space in fuzzy partitions. A fuzzy objective function is defined. An algorithm for its minimization is presented. Simulation results are given.

Simplified implementation of a soft decision threshold decoder

New fully digital hardware designs for soft-decision threshold decoders are introduced to significantly reduce the complexity and increase the coding gain as compared to previously proposed architectures. These designs are useful for high-rate self-orthogonal convolutional codes with a long constraint length. The study case considered in this paper is for a rate 23/24, constraint length 4056 code used in a typical microwave digital radio. The new decoder architecture provides a four-fold decrease in complexity and an additional 0.3 dB coding gain as compared to previous designs. The simplification of the decoding architectures is possible through the use of three techniques: a different processing of feedback, the separation of information bit and reliability bit processing and the use of partial reencoding.<<ETX>>

An efficient FPGA implementation of a pulse-shaping IIR filter

An efficient field programmable gate array (FPGA) implementation of an IIR pulse-shaping filter is presented. Several techniques have been used in order to decrease the filters processing time and the coefficients quantization effects. The filter was designed to functionally replace as closely as possible an analog one used in a medium capacity digital microwave radio. Simulation and experimental results agree closely with the theoretical predictions.

Low phase noise programmable clock generators for wireless modems

Modern digital programmable modems require very stable clock generation at the transmit side to provide a clean spectrum and to guarantee bit count integrity in the presence of prolonged signal outages. On the other hand, such modems need also to carry various traffic rates which in turn require a programmable clock. This paper covers the design performance and analysis of a high frequency, DDS driven, third order DPLL. The paper identifies the noise sources in such a design which differ from the traditional VCO driven PLL noise sources. Furthermore the analysis and hardware implementation of a low cost, low phase noise, wide range, high frequency and programmable clock generator are presented in the paper.