We propose the use of a lower or upper triangular sub-base matrix to replace the identity matrix in the source-check-channel-variable linking protomatrix of a double-protograph low-density parity-check joint-source-channel code (DP-LDPC JSCC). The elements along the diagonal of the proposed lower or upper triangular sub-base matrix are assigned as "1" and the other non-zero elements can take any non-negative integral values. Compared with the traditional DP-LDPC JSCC designs, the new designs show a theoretical channel threshold improvement of up to 0.41 dB and a simulated source symbol error rate improvement of up to 0.5 dB at an error rate of 1e-6.

翻译：我们提出使用下三角或上三角子基矩阵替代双原图低密度奇偶校验联合信源信道编码（DP-LDPC JSCC）中信源校验信道变量连接原矩阵中的单位矩阵。所提出的下三角或上三角子基矩阵的对角线元素赋值为"1"，其他非零元素可取任意非负整数值。与传统DP-LDPC JSCC设计相比，新设计在理论上可实现高达0.41 dB的信道阈值改善，且在1e-6误码率条件下，信源符号误码率仿真改善可达0.5 dB。