1 research outputs found
Impact of Backward Crosstalk in 2x2 MIMO Transmitters on NMSE and Spectral Efficiency
We consider backward crosstalk in 2 x 2 transmitters, which is caused by
crosstalk from the outputs of the transmitter to the inputs or by the
combination of output crosstalk and impedance mismatch. We analyze its impact
via feedback networks together with third-order power amplifier
non-linearities. We utilize the Bussgang decomposition to express the distorted
output signals of the transmitter as a linear transformation of the input plus
uncorrelated distortion. The normalized mean-square errors (NMSEs) between the
distorted and desired amplified signals are expressed analytically and the
optimal closed-form power back-off that minimizes the worst NMSE of the two
branches is derived. In the second part of the paper, an achievable spectral
efficiency (SE) is presented for the communication from this ``dirty''
transmitter to another single-antenna receiver. The SE-maximizing precoder is
optimally found by exploiting the hardware characteristics. Furthermore, the
optimal power back-off is analyzed for two sub-optimal precoders, which either
do not exploit any hardware knowledge or only partial knowledge. The simulation
results show that the performance of these sub-optimal precoders is
close-to-optimal. We also discuss how the analysis in this paper can be
extended to transmitters with an arbitrary number of antenna branches.Comment: 15 pages, 11 figures, To appear in IEEE Transactions on
Communication