High reuse efficiency of radio resources in urban microcellular systems

A new microcell configuration scheme in urban areas is proposed in order to increase the reuse efficiency of radio resources. Multiple directional-bea m antennas lined up along a street form a cigar-shaped cell. Antennas are l ocated at intersection and are directed along the intersecting streets. Two antennas facing each other Form a microzone and, therefore, a cigar-shaped cell consists of multiple microzones in a line. Each microzone is protecte d against cochannel interference from neighboring microzones by confinement of transmitted signals to a microzone using down-tilting of antenna beams. Therefore, a radio channel which is occupied in one microzone can be used in adjacent microzones. An increase in system rapacity is achieved by the h igh reuse efficiency of radio resources. The proposed system increases syst em capacity up to 560% with a call blocking probability of 1% when compared with a conventional system. In addition, a macrodiversity scheme using two antennas in a microzone improves call quality on reverse link.