This paper analyzes faster-than-Nyquist (FTN) signaling within a consistent framework based on a fixed time-bandwidth product (TBP), resolving potential ambiguities present in finite blocklength analysis. A key feature of FTN is its ability to increase the number of transmitted symbols in a given time and frequency resource, which can lower the rate penalties inherent in short packet communications. We derive tight bounds on the maximum channel coding rate (MCCR) and demonstrate that FTN's rate gains over Nyquist signaling can be higher in the finite TBP regime than in the asymptotic case. Performance is benchmarked against the theoretical optimum of transmitting prolate spheroidal wave functions, showing that a well-designed FTN system can closely approach this limit. We present practical design criteria, including the optimal time-acceleration factor for maximizing signaling dimensions, an optimized pulse shape that meets strict out-of-band constraints, and a turbo-equalization-based coding scheme that performs near the derived MCCR bounds. These findings establish FTN as a practical and near-optimal technique for enhancing the rate and reliability of latency-constrained communications.

翻译：本文在固定时宽带宽积（TBP）的一致框架下分析超奈奎斯特（FTN）信号传输，解决了有限码长分析中可能存在的模糊性。FTN的一个关键特性是能够在给定的时间和频率资源中增加传输符号数量，从而降低短包通信固有的速率损失。我们推导了最大信道编码速率（MCCR）的紧致界，并证明在有限TBP条件下，FTN相对于奈奎斯特信号传输的速率增益可能高于渐近情况。通过以传输扁球面波函数这一理论最优方案为基准进行性能评估，表明设计良好的FTN系统能够逼近该极限。我们提出了实用的设计准则，包括最大化信号维度的最优时间加速因子、满足严格带外约束的优化脉冲波形，以及性能接近MCCR界的基于Turbo均衡的编码方案。这些发现确立了FTN作为一种实用且接近最优的技术，可用于提升时延受限通信的速率与可靠性。