Rethinking Uplink Hybrid Processing: When Is Pure Analog Processing Suggested?

Abstract

In this correspondence, we analytically characterize the benefit of digital processing in uplink massive multiple-input multiple-output (MIMO) with sub-connected hybrid architecture. By assuming that the number of radio frequency (RF) chains is equal to that of users, we characterize achievable rates of both pure analog detection and hybrid detection under the i.i.d. Rayleigh fading channel model. From the derived expressions, we discover that the analog processing can outperform the hybrid processing using the maximal ratio combining (MRC) or zero-forcing (ZF) criterion in cases under some engineering assumptions. Performance comparison of the schemes are presented under tests with various numbers of users and numbers of antennas at the base station. Index TermsAnalog processing, hybrid processing, massive MIMO.

Analog Versus Hybrid Precoding for Multiuser Massive MIMO With Quantized CSI Feedback

“…Based on the minimum Euclidean distance criterion, a common way of analog precoder design in the sub-connected structure follows [9] [10]…”

“…Note that this result coincides with the result in [9, Eq. 15] except for that the signal term and the interference term calculated in [9] have an additional factor of 1 N if we let…”

“…Specifically in [9], the authors found that pure analog processing could surpass the hybrid processing with maximal-ratio combination (MRC) or ZF in an uplink channel under the assumption of perfect channel state information (CSI). For the downlink channel, however, this compromise is still unclear.…”