Fixed-Beam MIMO Scheme

In the current study we show that even being conceptually different approaches the traditional fixed-beam scheme can be combined with the MIMO approach. This offers increased spectral efficiency due to the beamforming gain which improves the SINR at the receiver and enables control of the interference in the transmitter. In the proposed scheme different parallel data streams are transmitted from different beams and signals at the receiver are first transformed to orthogonal beam space. MIMO processing is applied in the beam domain. Monte-Carlo simulations on channel capacity show that the beam domain approach can offer significant performance improvement. The gain in outage capacity depends on the SNR level and ranges from 7 bit/s/Hz up to 15 bit/s/Hz in radio channels with large angular dispersion. Both the antenna and the beam domain MIMO approaches perform best in spatially rich scattering environment