In view of the problems that the encoding complexity of quasi-cyclic low-density parity-check (QC-LDPC) codes is high and the minimum distance is not large enough which leads to the degradation of the error-correction performance, the new irregular type-II QC-LDPC codes based on perfect cyclic difference sets (CDSs) are constructed. The parity check matrices of these type-II QC-LDPC codes consist of the zero matrices with weight of 0, the circulant permutation matrices (CPMs) with weight of 1 and the circulant matrices with weight of 2 (W2CMs). The introduction of W2CMs in parity check matrices makes it possible to achieve the larger minimum distance which can improve the error- correction performance of the codes. The Tanner graphs of these codes have no girth-4, thus they have the excellent decoding convergence characteristics. In addition, because the parity check matrices have the quasi-dual diagonal structure, the fast encoding algorithm can reduce the encoding complexity effectively. Simulation results show that the new type-II QC-LDPC codes can achieve a more excellent error-correction performance and have no error floor phenomenon over the additive white Gaussian noise (AWGN) channel with sum-product algorithm (SPA) iterative decoding.

现有车载网中根据地理位置信息贪婪转发并利用路侧单元辅助的路由算法存在大量的冗余Beacon消息, 节点在贪婪转发时容易陷入局部最大, 偏离原有路径。针对这些问题, 提出一种高效的路由和消息聚合机制, 该机制采用控制包的聚合及数据包与控制包的消息聚合机制来减少控制包的发送, 并对节点利用贪婪转发时陷入局部最大和偏离原有路径进行有效处理。仿真实验结果表明, 路由和消息聚合机制能有效地提高消息发送的成功率, 降低消息的平均端到端时延, 减少网络的控制包开销。

文章针对切换时延不为零的光交换调度提出了一种新算法——2近似启发算法。算法由两部分组成：选择匹配和决策权重。其中，选择匹配是确定光交叉阵列的切换次数，由贪心算法完成；决策权重是决定各个配置的持续时长，它是通过选择一个值以使剩下的业务矩阵的开销估计最优。2近似启发算法的近似因子为2，时间复杂度为O(N2logN)。仿真表明这种调度算法更接近最优调度，比DOUBLE[1]和ADJUST[2]算法更能自适应传送来的不同业务模式。