Portable radio telephone system

Claim 1

In a portable radio telephone system for use in a given area which is divided into a plurality of large areas, each of said large areas being further divided into a plurality of small cellular areas, wherein the same radio frequency channels are repeated for each of said large areas, while respective ones of said radio frequency channels are allocated to said respective small cellular areas in each large area, a system for effecting radio communication by means of a portable radio telephone set by use of selected ones of said allocated frequency channels, comprising: a plurality of antennas provided in a local area disposed inside one of said small cellular areas for transmitting and receiving radio waves; a portable radio telephone set; a private branch exchange disposed within said local area; and a transmission/reception circuit connecting said antennas to said private branch exchange; wherein radio communication is carried out inside said local area by said portable radio telephone set by use of radio waves of one of said allocated frequency channels of a non-adjacent small cellular area which is different from the frequency channel allocated to the small cellular area in which said local area is disposed and the power of said radio waves used by said portable radio telephone set in said local area is larger than the power of radio waves of the same frequency radiated from small cellular areas other than said small cellular area in which said local area is disposed.