  We provide a novel framework to study subspace codes for non-coherent
communications in wireless networks. To this end, an analog operator channel is
defined with inputs and outputs being subspaces of $\mathbb{C}^n$. Then a
certain distance is defined to capture the performance of subspace codes in
terms of their capability to recover from interference and rank-deficiency of
the network. We also study the robustness of the proposed model with respect to
an additive noise. Furthermore, we propose a new approach to construct subspace
codes in the analog domain, also regarded as Grassmann codes, by leveraging
polynomial evaluations over finite fields together with characters associated
to finite fields that map their elements to the unit circle in the complex
plane. The constructed codes, referred to as character-polynomial (CP) codes,
are shown to perform better comparing to other existing constructions of
Grassmann codes in terms of the trade-off between the rate and the normalized
minimum distance, for a wide range of values for $n$.
