The co-channel interference pmtection ratio is a particularly important parameter within cellular systems. Not only does the p t e c t i o n ratio influence their spectral emciency, but also sums up dl techniques which can improve the signal quality at the receiver output and accounb for all hazanlous conditions which can impair the signal quality. This paper is a serious attempt to q u e for and outline a 'standnrd' and systematic subjective test and a set of 'standnrd' pmceduns by which the p t e c t i o n ratio for vmious systems can be evaluated 1 Intmduction Cellular systems are interference limited and the protection ratio plays a particularly important role in assessing their spectral efficiency. Moreover, the protection ratio sums up all factors which CM influence the quality of the signal at the receiver output and accounts for all hazardous conditions which cause the signal quality to deteriorate. Despite of the importance of the protection ratio, there is still a dearth of published information of a practical character on actual protection ratios measured under realistic conditions. In particular, modern digital systems are usually specified with objective protection ratio figures rather than the more desired subjectively measured ones. Furthermore, the methods by which some protection ratio figures are obtained can vary considerably. It is necessary, therefore, to agree upon a standad systematic method together with standad procedures by which the protection ratio can be evaluated. Such a standard method should account for all propagation effects on the radio signal and allow for any technique which is believed to enhance the performancdefficiency of any particular system to be included. Most importantly, the siandanj test will ensure uniform and perhaps more accurate protection ratio figures.This paper starts with the definition and mathematical interpretation of the protection ratio. The relationship between the spectral efficiency and the protection ratio is also shown. Various methods by which the protection ratio may be evaluated are discussed and the advantages and disadvantages of each method are presented. The paper concludes with some suggestions and recommendations for the subjective evaluation of the protection ratio within cellular systems.
Definition and Mathematical Representation of the Pmtection RatioThe World Administrative Radio Conference, Geneva, 1979, defined the protection ratio as "/he ntininttim vdt4e ojihc wantedio-tmivanicd signal miio, itstidly cxpmsscd in decibels. ai ihc mccivcr inpiti dcicmiimJ tinder spccijicd concliiions such /ha/ a spccificd qtcaliry is achicvcd ai ihe mccivcr otriytii" [I]. This may have different values depending on the' type of modulation technique used and the quality of service required. The above definition of protection ratio appears to be a comprehensive one. However, in cellular systems, it is necessary to have a standard set of conditions under which the protection ratio is assessed as well as a standard voice quality. Furthermore, to ensure ...
