A cellular radio communication system operating in accordance with a time division multiple access protocol assigns different fractional loading factors to different time slots. As a result, as well as because of the effects of local propagation conditions, different time slots will have different interference levels. A mobile station in a worst-case propagation environment (such as near the edge of a cell or when subject to severe shadowing fading) can be assigned a time slot having a low interference level, while a mobile station in a good propagation environment can be assigned a time slot having a higher interference level.