Generalized cell planning technique applied for 4x12 frequency-reuse

The clover-leaf cell configuration method is widely used in wireless industry for radio network planning. However, for 4x12 frequency reuse in GSM system, the clover-leaf cell configuration has a unique challenge due to the fact that the antenna main beams of the nearest co-channel cells lie on the same axis. This increases co-channel interference and reduces coverage area. For conventional cell configuration with 4x12 frequency reuse, the base station is placed in the center of a hexagon, the problem of adjacent co-channel cells transmitting along the same antenna axis does not exit, however, it has the drawback of dead coverage spots and requires use of wide-beam antenna to compensate. This paper proposes a generic cell configuration scheme using antenna orientation rotation technique. It is demonstrated that the clover-leaf cell configuration is a special case of this generic cell planning method, with antenna orientation rotation of 30 degree for all sectors. Applying the generic cell configuration scheme, a novel cell configuration scheme. Alternate row antenna rotation (ARAR), for 4x12 GSM frequency reuse is proposed. In ARAR scheme, half of the antenna orientations are rotated by 60 degrees. With the use of antenna orientation rotation in ARAR, the cell edge coverage is mutual enhanced by adjacent sectors thus no dead spot exists and narrow-beam antenna can be used. The ARAR method combines the benefits of both conventional and clover-leaf cell configurations, it improves the C/I ratio at weak coverage link by 2.5 dB.