Delay spread reduction effect of beam antenna and adaptively controlled beam facing access system in urban line-of-sight street microcells

The paper presents theoretical and experimental investigation results of the delay spread reduction effect of beam antennas in urban line-of-sight (LOS) street microcells. The 95% delay spread cumulative probability in a 600 m LOS cell length is reduced to 70% when the 3 dB beamwidth of the base station (BS) antenna is in the range from 80° to 140°, compared with that (420 ns) in omnidirectional antennas. An adaptively controlled beam facing access (ABFA) system in which the beam antennas are used in both the base and mobile stations is further proposed. The beam direction of the BS antenna is fixed along the street, but that of the mobile station (MS) antenna is adaptively controlled as the maximum received power is obtained. Using ABFA, the 95% delay spread cumulative probability in the 300 m LOS microcell is reduced to less than 70 ns, when the antenna beam-width lies in the range from 20° to 140° in the BS and about 80° in the MS.