实现水下并发随机接入的速率-并发度平衡
Achieving Rate-Concurrency Balance for Underwater Concurrent Random Access
AI总结：
该研究针对水下声学网络的速率-并发度权衡问题，提出结合EZCDM波形与跨层链路自适应框架的跨层并发随机接入系统，可将冲突转化为可解码流，实现BER和吞吐量增益。
AI中文摘要：
水下声学网络面临着基本的速率-并发度权衡：高速率波形（如OFDM、OTFS）专为点对点链路设计，依赖正交MAC协议（如TDMA）避免冲突，牺牲了并发度；相反，抗冲突波形（如CDMA、ZCMod）支持无协调接入，但因扩频或稀疏索引调制而存在固有限速率。我们提出了\textbf{\textbackslash system}，一种跨层并发随机接入系统，它结合了两个新组件：（i）\textbf{EZCDM}，一种等距ZC划分复用波形，将ZC根的多个循环移位激活为并行子信道，具有可调的速率-鲁棒性权衡，以及一种符号内差分接收机，无需显式CIR估计即可消除共享多径信道响应；（ii）\textbf{跨层链路自适应（LA）框架}，具有信标帧随机接入、用户特定闭环功率控制、以及感知重叠和CIR的公共-MS选择。基于信道迹和信号迹的物理层实验结合PHY在环网络仿真表明，\textbackslash system通过将传统上破坏性的冲突转换为可解码的并发流，相较于传统波形和MAC协议实现了显著的BER和吞吐量增益。
英文摘要：
Underwater acoustic networks face a fundamental rate--concurrency tradeoff: high-rate waveforms (e.g., OFDM, OTFS) are designed for point-to-point links and rely on orthogonal MAC protocols (e.g., TDMA) to avoid collisions, sacrificing concurrency; conversely, collision-resilient waveforms (e.g., CDMA, ZCMod) support uncoordinated access but are inherently rate-limited by spreading or sparse index modulation. We present \system, a cross-layer concurrent random-access system that combines two new components: (i) \textbf{EZCDM}, an equidistant ZC division-multiplexing waveform that activates multiple cyclic shifts of a ZC root as parallel sub-channels with a tunable rate--robustness tradeoff, and an intra-symbol differential receiver that eliminates the shared multipath channel response without explicit CIR estimation; and (ii) a \textbf{cross-layer link adaptation (LA) framework} featuring beacon-framed random access, user-specific closed-loop power control, and overlap- and CIR-aware common-MS selection. Channel-trace- and signal-trace-driven physical-layer experiments combined with PHY-in-the-loop network simulations demonstrate that \system\ achieves significant BER and throughput gains over conventional waveforms and MAC protocols by converting traditionally destructive collisions into decodable concurrent streams.
