I am learning this paper in which page11 says
The most well-known, in medical image analysis, of these novel CNN architectures is U-net, published by Ronneberger et al. (2015) (section 2.4.3). The two main architectural novelties in U-net are the combination of an equal amount of upsampling and downsampling lay- ers. Although learned upsampling layers have been pro- posed before, U-net combines them with so-called skip connections between opposing convolution and decon- volution layers. This which concatenate features from the contracting and expanding paths. From a training perspective this means that entire images/scans can be processed by U-net in one forward pass, resulting in a segmentation map directly.
This which concatenate features from the contracting and expanding paths
seems to mean
This (combination) concatenate features from the contracting and expanding paths
it seems that the word "which" does not play a import role in the sentence.
is the sentence a informative expression?