An air-fuel ratio control apparatus of an internal combustion engine according to the present invention is provided with oxygen storage amount estimating means, downstream exhaust air-fuel ratio detecting means, maximum oxygen storage amount estimating means, and air-fuel ratio target setting means. The method takes into account the idea of limiting the number of new cells while reducing target costs and respecting design constraints. Rather, the state of each document accessor is maintained using the bitmaps, and an efficient cyclic array based data structure is used to track the document access-count state. A mesh network includes a plurality of biodegradable devices and one or more edge collection devices.