We apply the strategy of , where multiple convolutional layers can be used for information combination.
for the k-th layer, transformed inputs are obtained by linear transformation for each channel: where W k,e and b e (e ∈ {self, up, down}) are model parameters, and h k−1,e j (e ∈ {self, left, right, down}) is the hidden state of last layer for node e(j).