Protection against cochannel interference from neighboring cells using down-tilting of antenna beams

An antenna-beam tilting scheme is proposed in order to confine the transmitted power from the base station antenna to a cell and thereby simultaneously reusing radio resource in multiple adjoining cells. A Manhattan-style city area is considered with horizontal and vertical streets. A group of directional-beam antennas lined up along a street forms a cigar-shaped service area controlled by a processor unit named the central station. Two antennas facing each other with a distance of street block form a cell. Each cell has a radio coverage non-overlapped with another cell by confining the transmitted signal using downtilting of antenna beams. Therefore interference from neighboring cells is substantially mitigated. Controlling the angle of tilted beam according to the antenna height and the distance between antennas, we can manage to keep the signal-to-interference ratio to 12dB, which is the threshold of quality of service required in digital mobile communication systems