Significant inter-symbol interference (ISI) challenges the achievement of reliable, high data-rate molecular communication via diffusion. In this paper, a hybrid modulation based on pulse position and concentration is proposed to mitigate ISI. By exploiting the time dimension, molecular concentration and position modulation (MCPM) increases the achievable data rate over conventional concentration and position-based modulations. In addition, unlike multi-molecule schemes, this hybrid scheme employs a single-molecule type and simplifies transceiver implementations. In the paper, the optimal sequence detector of the proposed modulation is provided as well as a reduced complexity detector (two-stage, position-concentration detector, TPCD). A tractable cost function based on the TPCD detector is proposed and employed to optimize the design of the hybrid modulation scheme. In addition, the approximate probability of error for the MCPM-TPCD system is derived and is shown to be tight with respect to simulated performance. Numerically, MCPM is shown to offer improved performance over standard concentration and pulse position-based schemes in the low transmission power and high bit-rate regime. Furthermore, MCPM offers increased robustness against synchronization errors.

中文翻译：

---

分子通信的浓度-时间混合调制方案

显着的符号间干扰 (ISI) 挑战了通过扩散实现可靠、高数据速率的分子通信。在本文中，提出了一种基于脉冲位置和浓度的混合调制来减轻 ISI。通过利用时间维度，分子浓度和位置调制 (MCPM) 比传统的浓度和基于位置的调制提高了可实现的数据速率。此外，与多分子方案不同，这种混合方案采用单分子类型并简化了收发器的实现。在本文中，提供了所提出调制的最佳序列检测器以及降低复杂度的检测器（两级位置集中检测器，TPCD）。提出并采用了一种基于 TPCD 检测器的易处理成本函数来优化混合调制方案的设计。此外，推导出了 MCPM-TPCD 系统的近似错误概率，并且显示出与模拟性能相关的紧密度。在数字上，MCPM 显示出在低传输功率和高比特率机制下提供优于标准集中和基于脉冲位置的方案的改进性能。此外，MCPM 提供了针对同步错误的增强鲁棒性。MCPM 被证明在低传输功率和高比特率机制下提供比标准集中和基于脉冲位置的方案更好的性能。此外，MCPM 提供了针对同步错误的增强鲁棒性。MCPM 被证明在低传输功率和高比特率机制下提供比标准集中和基于脉冲位置的方案更好的性能。此外，MCPM 提供了针对同步错误的增强鲁棒性。