标题： 水下声学通信的自适应多用户MCDM 显示英文标题

标题： Adaptive Multiuser MCDM for Underwater Acoustic Communications

摘要： 线性调频信号因其对多径的鲁棒性和优异的相关特性，在雷达和水下声学（UW-A）通信系统中得到了广泛利用。 我们提出了一种多用户多载波线性调频划分复用（MU-MCDM）系统，该系统在频率子载波中使用正交线性调频扩频技术以支持多用户应用。 此外，为了实现MCDM系统的连续和离散化，开发了正交线性调频变换（OCT）和离散正交线性调频变换（DOCT）。 此外，我们设计了一个最大似然（ML）接收机，能够完成同步、信道估计和符号检测。 MU-MCDM系统考虑了前导码长度、子载波数量、导频比例、保护间隔以及多用户接入场景等因素，以适应时变的UW-A信道。 仿真研究评估了误比特率（BER）性能和自适应传输。 因此，我们在仿真中展示了MCDM调制系统能够自适应地提升UW-A通信性能并支持多个用户。 此外，MCDM架构可以应用于更高阶调制方式，以在UW-A信道中提供更高的传输速率。 显示英文摘要

摘要： Chirp signals have been exploited extensively in radar and underwater acoustic (UW-A) communication systems for their robustness to multipath and superior correlation properties. We present a multiuser multicarrier chirp-division multiplexing (MU-MCDM) system which orthogonal chirp spread spectrum are utilized in frequency subcarriers for multiuser applications. Furthermore, orthogonal chirp transform (OCT) and discrete orthogonal chirp transform (DOCT) are developed for continuous and discrete implementations of MCDM systems. In addition, we design a maximum likelihood (ML) receiver capable of synchronization, channel estimation, and symbol detection. MU-MCDM systems consider factors, including preamble length, number of subcarriers, portion of pilots, guard period, and multiuser access scenarios to adapt time-variant UW-A channels. The bit-error-rate (BER) performance and adaptive transmission are evaluated in simulation studies. Therefore, we have demonstrated MCDM modulation systems in simulations that they improve performance of UW-A communications adaptively and support multiple users. Moreover, MCDM architectures can be applied in higher order modulations for providing higher transmission rates in UW-A channels.