0 7 4 0 7 4 5 9 / 0 3 / $ 1 7 . 0 0 © 2 0 0 3 I E E E complement the waterfall model, others appear to contradict its main principles. Furthermore, the performance dimensions that each practice seeks to optimize often differ. Unfortunately, these potential conflicts are difficult to resolve because the data presented to support most models is anecdotal and biased toward reporting only successfu...

In this paper, a method to design regular (2, dc)-LDPC codes over GF(q) with both good waterfall and error floor properties is presented, based on the algebraic properties of their binary image. First, the algebraic properties of rows of the parity check matrix H associated with a code are characterized and optimized to improve the waterfall. Then the algebraic properties of cycles and stopping...

A new general concatenated code structure, containing both parallel and serially concatenated codes as special cases, is presented. The structure provides a unified framework for the analysis of concatenated codes and offers new degrees of freedom for code design. Performance analysis based on bounds on the error probability in the error floor region and suggestions for suitable design criteria...

We propose an analysis tool of the finite-length iterative turbo decoding algorithm. The proposed tool is a generalized EXIT chart based on the mutual information transfer characteristics of the extrinsic information in the iterative turbo decoding algorithm. The proposed tool can describe the probabilistic convergence behavior of the iterative decoding algorithm. By using this tool, we obtain ...

Agile methodology is an approach used for the development of a project which helps to respond to the unpredictability of building software through incremental, iterative work cadences. These methodologies are used to deal with the situations where the waterfall model fails. The biggest drawback of waterfall model is that it assumes that every requirement of the project can be identified before ...

In this paper, a method to design regular (2, dc)LDPC codes over GF(q) with both good waterfall and error floor properties is presented, based on the algebraic properties of their binary image. First, the algebraic properties of rows of the parity check matrix H associated with a code are characterized and optimized to improve the waterfall. Then the algebraic properties of cycles and stopping ...

A finite length analysis is introduced for irregular repetition slotted ALOHA (IRSA) that enables to accurately estimate its performance in the moderate-to-high packet loss probability regime, i.e., in the so-called waterfall region. The analysis is tailored to the collision channel model, which enables mapping the description of the successive interference cancellation process onto the iterati...

A fundamental problem in evolutionary ecology research is to explain how different species coexist in natural ecosystems. This question is directly related with species trophic competition. However, competition theory, based on the classical logistic Lotka-Volterra equations, leads to erroneous conclusions about species coexistence. The reason for this is incorrectly interpreted interspecific i...

Computer R apid change in information technology brings with it a frequent need to undo the effects of previous culture change efforts. This process, while often challenging and frustrating, offers numerous rewards for success. Organizations can change from slow, reactive, adversarial, separated software and systems engineering processes to unified, concurrent processes. These processes better ...

In this paper we look at a number of approaches for modeling the system acquisition process. Beginning with the waterfall model of Winston Royce, we continue with derivation that includes more intricate and detailed waterfall models with feedback, including the “V” and spiral models. In addition we look at several acquisition strategies. In reviewing the various models we discuss our view that ...