vn_update_sum

sionna.phy.fec.ldpc.vn_update_sum(msg_c2v: torch.Tensor, mask: torch.Tensor, llr_ch: torch.Tensor, llr_clipping: float | None = None) → Tuple[torch.Tensor, torch.Tensor]

Variable node update function implementing the sum update.

This function implements the (extrinsic) variable node update function. It takes the sum over all incoming messages msg excluding the intrinsic (= outgoing) message itself.

Additionally, the channel LLR llr_ch is considered in each variable node.

Parameters:

• msg_c2v (torch.Tensor) – Tensor of shape [batch_size, num_nodes, max_degree] representing c2v messages.

• mask (torch.Tensor) – Tensor of shape [num_nodes, max_degree] indicating valid edges.

• llr_ch (torch.Tensor) – Tensor of shape [batch_size, num_nodes] containing the channel LLRs.

• llr_clipping (float | None) – Clipping value used for internal processing. If None, no internal clipping is applied.