Spectrum-efficient distributed collaborative beamforming in the presence of local scattering and interference

In this paper, a minimum variance distortionless response (MVDR) collaborative beamformer (CB) is considered to achieve a dual-hop communication from a far-field source surrounded by several interfering transmitters to a receiver, through a wireless network comprised of K independent terminals. Whereas the previous works assumed a model of plane wavefronts, here, a local scattering in the source and interferences vicinities is considered, thereby broadening the range of applications in real-world environments. It is shown that the required bandwidth allocation to the MVDR CB implementation linearly increases with K and becomes prohibitive in some applications where the number of terminals is typically large. Aiming to improve the system´s spectrum efficiency, a novel distributed collaborative beamformer (DCB) whose implementation does not require any bandwidth allocation and, further, that well-approximates its MVDR CB counterpart is then proposed. The performance of the proposed technique is analyzed and its net advantages against the scattering-free DCB technique, which is designed without taking into account the presence of local scattering in the source and interferences vicinities, are proved.