Volume 25, Issue 2, June 2014

Comparison of the Upper Bounds of the Link Efficiency of Selective-Repeat ARQ in Burst Error Channels Considering Unreliable Acknowledgements [Full Text]

K. D. R. Jagath Kumara

Abstract—Recent research on high efficiency data links includes a variety of hybrid-ARQ protocols, which almost always rely on the principles of selective-repeat ARQ (SR-ARQ) protocol. In evaluating the efficiency of such protocols, it is often assumed that the acknowledgement channel is perfect and therefore the acknowledgements, positive or negative, are not lost. However, this paper illustrates the inaccuracy caused by making this assumption. It compares the upper bound of the efficiency that would result if the acknowledgements are reliable to that if the acknowledgements are unreliable considering burst error channels, in particular. For this purpose, the paper first uses a statistical model of a burst error channel to derive the frame error probability and the corresponding efficiency theoretically. It also generates such bursty bit sequences, according to the model, in the computer and estimates the quantities of interest for validation. This paper then simulates a data transmission scheme over a multipath Rayleigh fading channel and estimates the parameters of the burst model in order to evaluate the same. In most cases, it makes comparisons to random error channels. 

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An Efficient 12b 30MS/s Pipelined SAR ADC in 180nm CMOS [Full Text]

L. Bagheriye, S. Toofan and KH. Dabbagh Sadeghipour

Abstract— This paper describes the design of a 12-b 30MS/s analog to digital converter (ADC) in a 0.18μm CMOS technology. The converter pipelines a first stage 5b MDAC with a second stage 8b SAR ADC. Using SAR ADC in the first stage's sub-ADC, instead of FLASH type, frees the ADC from an extra front-end sample-and-hold and uses only one comparator in first stage, resulting a power efficient ADC architecture. To improve SNR, comparator with a rail-to-rail common-mode input range is used in each stages. This ADC consumes only 10 mW and achieves an SNDR of 64.86 dB, resulting in a figure of merit (FOM) of 186 fJ/Conversion-step. 

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All Optical Signal Processing of Optical Fiber Raman Amplifiers in Advanced Photonic Communications Engineering [Full Text]

Ahmed Nabih Zaki Rashed, Ibrahim M. El-Dokany, Abd El–Naser A. Mohamed, and Sarah El-Tahan

Abstract— This paper has presented the transmission systems with employing Raman amplifier technology have to put up with much higher level of design complexities, when compared to conventional transmission lines with doped fiber optical amplifier. Even for the construction of a fundamental, basic building block a unit of a fiber Raman amplifier (FRA), the designer have to struggle with the problems associated with the interactions between pump/signal waves mediated by Raman process, have to wander within the vast degrees of freedom given the choice of pumping directions/ratios, and have to contemplate with the wavelength dependent fiber loss/noise figure profiles in different fiber cable medias such as true wave reach fiber, freelight, and single mode fiber (SMF). 

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A Proposal for Advanced Flow based charging in PCC architecture [Full Text]

Abstract - This work depicts a proposal of possible and feasible method for reduction of prepaid credit control and update requests in real time, within the „Policy and Charging Control“ (PCC) architecture. Consideration is relating to IMS (IP Multimedia Subsystem) environment, on condition where QoS can be dynamic changed and different feasible service configurations affect the charging process.