2 research outputs found
Performance of Hierarchical Sparse Detectors for Massive MTC
Recently, a new class of so-called \emph{hierarchical thresholding
algorithms} was introduced to optimally exploit the sparsity structure in joint
user activity and channel detection problems. In this paper, we take a closer
look at the user detection performance of such algorithms under noise and
relate its performance to the classical block correlation detector with
orthogonal signatures. More specifically, we derive a lower bound for the
diversity order which, under suitable choice of the signatures, equals that of
the block correlation detector. Surprisingly, in specific parameter settings
non-orthogonal pilots, i.e. pilots where (cyclically) shifted versions
interfere with each other, outperform the block correlation detector.
Altogether, we show that, in wide parameter regimes, the hierarchical
thresholding detectors behave like the classical correlator with improved
detection performance but operate with much less required pilot subcarriers. We
provide mathematically rigorous and easy to handle formulas for numerical
evaluations and system design. Finally, we evaluate our findings with numerical
examples and show that, in a practical parameter setting, a classical pilot
channel can accommodate up to three advanced pilot channels with the same
performance.Comment: 15 pages, 12 figure
Compressed Sensing Channel Estimation for OFDM with non-Gaussian Multipath Gains
This paper analyzes the impact of non-Gaussian multipath component (MPC)
amplitude distributions on the performance of Compressed Sensing (CS) channel
estimators for OFDM systems. The number of dominant MPCs that any CS algorithm
needs to estimate in order to accurately represent the channel is
characterized. This number relates to a Compressibility Index (CI) of the
channel that depends on the fourth moment of the MPC amplitude distribution. A
connection between the Mean Squared Error (MSE) of any CS estimation algorithm
and the MPC amplitude distribution fourth moment is revealed that shows a
smaller number of MPCs is needed to well-estimate channels when these
components have large fourth moment amplitude gains. The analytical results are
validated via simulations for channels with lognormal MPCs such as the NYU
mmWave channel model. These simulations show that when the MPC amplitude
distribution has a high fourth moment, the well known CS algorithm of
Orthogonal Matching Pursuit performs almost identically to the Basis Pursuit
De-Noising algorithm with a much lower computational cost.Comment: Published in IEEE Transactions on Wireless Communications. arXiv
admin note: text overlap with arXiv:1812.0723