CONCURRENCY AND COMPUTATION: PRACTICE AND EXPERIENCE Concurrency Computat.: Pract. Exper. 2006; 18:725–747 Published online 20 October 2005 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/cpe.958 Applying fuzzy logic and genetic algorithms to enhance the efficacy of the PID controller in buffer overflow elimination for better channel response timeliness over the Internet Wilfred W. K. Lin ∗ ,† , Allan K. Y. Wongand Richard S. L. Wu Department of Computing, Hong Kong Polytechnic University, Hong Kong SAR SUMMARY In this paper two novel intelligent buffer overflow controllers: the fuzzy logic controller (FLC) and the genetic algorithm controller (GAC) are proposed. In the FLC the extant algorithmic PID controller (PIDC) model, which combines the proportional (P), derivative (D) and integral (I) control elements, is augmented with fuzzy logic for higher control precision. The fuzzy logic divides the PIDC control domain into finer control regions. Every region is then defined either by a fuzzy rule or a ‘don’t care’ state. The GAC combines the PIDC model with the genetic algorithm, which manipulates the parametric values of the PIDC as genes in a chromosome. The FLC and GAC operations are based on the objective function {0,} 2 . The principle is that the controller should adaptively maintain the safety margin  around the chosen reference point (represent by the ‘0’ of {0,} 2 ) at runtime. The preliminary experimental results for the FLC and GAC prototypes indicate that they are both more effective and precise than the PIDC. After repeated timing analyses with the Intel’s VTune Performer Analyzer, it was confirmed that the FLC can better support real- time computing than the GAC because of its shorter execution time and faster convergence without any buffer overflow. Copyright c  2005 John Wiley & Sons, Ltd. KEY WORDS: fuzzy logic; genetic algorithm; PID controller; buffer overflow; Internet channel; objective function; safety margin ∗ Correspondence to: Wilfred W. K. Lin, Department of Computing, Hong Kong Polytechnic University, Hong Kong SAR. † E-mail: cswklin@comp.polyu.edu.hk Contract/grant sponsor: Department of Computing/Hong Kong Polytechnic University; contract/grant numbers: H-ZJ92, H-ZJ91 and G-T426 Copyright c  2005 John Wiley & Sons, Ltd. Received 24 September 2002 Revised 17 February 2003 Accepted 18 February 2005