SimpleWeight Calculation Methods for MillimeterWave Band Massive Antenna Array in Direct Wave Dominant Environment

摘要

We propose two simple weight calculation methods (primarymethod and enhanced method), that estimate approximated phaseplane from a few antenna phase and calculate weights of all antenna elements,for wireless backhaul systems that utilize millimeter wave bandmassive antenna arrays. Such systems are expected to be used instead ofoptical fiber for connecting many small cell base stations (SCBSs) to thecore network, and supporting the rapid deployment of SCBSs. However,beamforming with massive antenna arrays requires many analog-digitalconverters (ADCs) and incurs the issue of implementation complexity. Theproposed methods overcome the problem by reducing the number of ADCs.Computer simulations clarify the appropriate layout and the number ofADCs connected to antenna elements; the effectiveness of the proposedmethods is confirmed by evaluations with measured channel state information(CSI) in propagation experiments on a wireless backhaul system.Experimental verifications on the case of calculating the weight of 200 elementsfrom the phases of just 9 elements show that the array gain degradationfrom ideal (the case in which the phases of all elements are used estimation)with both methods is less than 0.4 dB in the direct wave dominantenvironment. In addition, the enhanced method holds the array gain degradationto under 0.8 dB in an environment existing reflected waves. Theseresults show that the proposed methods can attain high accuracy beamformingwhile reducing ADC number.