Alrabadi, Osama3; Tsakalaki, Elpiniki1; Huang, Howard4; Pedersen, Gert Frølund2
1 Department of Electronic Systems, The Faculty of Engineering and Science (ENG), Aalborg University, VBN2 Antennas, propagation and radio networking, The Faculty of Engineering and Science (ENG), Aalborg University, VBN3 The Faculty of Engineering and Science (TECH), Aalborg University, VBN4 Alcatel-Lucent
The paper sheds light on the beamforming (BF) performance of large (potentially unconstrained in size) as well as dense (but physically constrained in size) antenna arrays when equipped with arbitrarily many elements. Two operational modes are investigated: Single-layer BF and multi-layer BF. In the first mode, a realistic BF criterion namely the average BF gain is revisited and employed to understand the far-field and the near-field effects on the BF performance of large-scale antennas above a clutter. The diminishing throughput returns in a single-layer BF mode versus the number of antennas necessitate multi-layering. In the multi-layer BF mode, the RF coverage is divided into a number of directive non-overlapping sector-beams in a deterministic manner within a multi-user multi-input multi-output (MIMO) system. The optimal number of layers that maximizes the user's sum-rate given a constrained antenna array is found as a compromise between the multiplexing gain (associated with the number of sector-beams) and the inter-beam interference, represented by the side lobe level (SLL).
I E E E Journal on Selected Areas in Communications, 2013, Vol 31, Issue 2, p. 314-325
Beamforming; Capacity; Clustering channels; EM Coupling; High Order Sectorization; Large Arrays; MIMO