The linear-eigenvalue-growth conjecture for the Hermitian-Toeplitz matrix T

Let NN be the system dimension, let β^\hat{\beta} and η^\hat{\eta} be the receiver parameters, and let Ψ(τ^A^)\boldsymbol{\Psi}(\hat{\boldsymbol{\tau}}_{\hat{\mathcal{A}}}) be the matrix formed from the selected delay estimates. Define the Hermitian-Toeplitz matrix

T=β^1η^Ψ(τ^A^)ΨH(τ^A^).\mathbf{T}=\hat{\beta}^{-1}\hat{\eta}\,\boldsymbol{\Psi}(\hat{\boldsymbol{\tau}}_{\hat{\mathcal{A}}})\boldsymbol{\Psi}^{\mathrm{H}}(\hat{\boldsymbol{\tau}}_{\hat{\mathcal{A}}}).

Linear-eigenvalue-growth conjecture. There exists an upper bound on the largest eigenvalue of T\mathbf{T} that grows linearly with NN:

λmax(T)=O(N).\lambda_{\max}(\mathbf{T})=\mathcal{O}(N).

The conjecture is introduced to justify an iterative conjugate-gradient method whose iteration count, and hence computational complexity, depends on the eigenvalue behavior of T\mathbf{T}. The source gives no resolution, so the conjecture remains open.

Sources & referencesView supporting material

Primary source

Thomas L. Hansen, Peter B. Jørgensen, Mihai-Alin Badiu and Bernard H. Fleury, “An Iterative Receiver for OFDM With Sparsity-Based Parametric Channel Estimation”, arXiv:1507.02954 (2018).

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