Holographic Multiple-Input, Multiple-Output Systems: Their Channel Estimation and Performance

Holographic multiple-input multiple-output (HMIMO) systems constitute a promising technology in support of next-generation wireless communications, thus paving the way for a smart programmable radio environment. However, despite their significant potentials, further fundamental issues remain to be addressed, such as the acquisition of accurate channel information. Indeed, the conventional angular-domain channel representation is no longer adequate for characterizing the sparsity inherent in HMIMO channels.