The effect of microreflections on decision feedback equalization

In coaxial cable modems and terrestrial broadcasting, the appearance and disappearance of microreflections cause a temporary drop in SNR at the equalizer output. We describe mathematically the effect of the appearance/disappearance of a microreflection on the performance of a previously trained fractionally spaced equalizer     

N-acetyl-cysteine causes a late re-specification of the anteroposterior axis in the Xenopus embryo

N-acetyl cysteine is an agent which has been shown to interrupt signal transduction processes linking a wide range of stimuli to the activation of NF-kappa B in mammalian cells. We have investigated its effect on the early development of Xenopus embryos by injecting it into blastulae, using concentrations comparable to those effective on cultured cells. High concentrations at the late blastula or early gastrula stage suppress posterior and enhance anterior development, yielding embryos with enlarged cement glands and otherwise consisting of little except head in extreme cases. Reducing the amount of N-acetyl cysteine injected leads to progressively more posterior structures developing. Injection into one- or two-cell embryos gives similar phenotypes, but of reduced severity and the cement gland is not so enlarged. Explants of animal cap cells taken several hours after injection develop to give large amounts of cement gland material. We have examined the expression of a number of genes in the anteriorised embryos. Posterior markers and Xsna are reduced. Noggin and Goosecoid mRNA are up-regulated through the gastrula and persist at these levels until at least the late neurula stage, whereas in controls Noggin is much lower and Goosecoid is absent at these stages. The most anteriorised phenotype may be a consequence of this changed expression.     

Scattered lookahead without finding polynomial roots or solvingsimultaneous equations

In this paper, we describe a method of calculating scattered lookahead coefficients that leads to a simple closed-form expression for the scattered lookahead filters. The coefficients are then found by simple polynomial multiplication. We also give closed-form expressions for any recursive decomposition of scattered lookahead     

Market and Technology Drivers for Cellular Infrastructure Modem Development

Cellular Infrastructure seems to be a fertile ground for new and sometimes not so new architectural ideas. Start ups as well as mature companies propose variants on software defined radio, reconfigurable architectures and dedicated chip sets. However the bulk of modems today have remained a combination of digital signal processors and ASICs. The demise of the DSP has been predicted many times over the last decade and yet it remains a strong part of cellular infrastructure. So what changes are really happening? In this paper we take a methodical approach to this question by first identifying the forces that are driving the industry today, and then deducing the architecture evolution implied by these forces. We discover that software defined radio and reconfigurability do indeed play a role but perhaps not in the way many suspect.     

Trends in multicore DSP platforms

Multicore digital signal processors (DSPs) have gained significant importance in recent years due to the emergence of data-intensive applications, such as video and high-speed Internet browsing on mobile devices that demand increased computational performance but lower cost and power consumption. Multicore platforms allow manufacturers to produce smaller boards while simplifying board layout and routing, lowering power consumption and cost, and maintaining programmability.     

DSP-based architectures for mobile communications: past, presentand future

Programmable DSPs are pervasive in the wireless handset market for digital cellular telephony. We present the argument that DSPs will continue to play a dominant, and in fact increasing, role in wireless communications devices by looking at the history of DSP use in digital telephony, examining the DSP-based solution options for today's standards, and looking at future trends in low-power DSPs     

Performance analysis of closed-loop transmit diversity in thepresence of feedback delay

In this paper, a bit-error-rate (BER) analysis for closed-loop transmit diversity in a time-selective Rayleigh fading channel containing feedback delay is presented. In the absence of feedback delay, closed-loop transmit diversity always outperforms open-loop transmit for a given transmitted signal energy. This is no longer true in the presence of feedback delay. We derive closed-form expressions of the average BER for this case assuming QPSK and BPSK signaling. The results of the analysis are instrumental for comparing closed-loop with open-loop schemes under given operating conditions. In particular, we demonstrate that, for a given transmitted energy and number of transmit antennas, open-loop outperforms closed-loop at sufficiently fast channel fading. We also show that, for a given transmitted signal energy and fading rate, closed-loop outperforms open-loop for sufficiently large numbers of transmit antennas while the total average transmitted signal energy is kept constant. For some special cases, closed-form expressions for the fading rate at which the performance of open-loop is equal to closed-loop are obtained