The present invention is essentially a method and system for leaving and retrieving messages at specific coordinate way points within a commercial mobile radio service provider network. Thus, the present invention provides novel cyano–methylenepiperidinophenyl oxazolidinone derivatives, processes for making the compounds, as well as antimicrobial compositions containing said derivatives as active ingredients and methods of treating bacterial infections with the said derivatives. The inventive optical fiber has a core glass composition with a germania doping concentration from 0% to 4% in weight.