In rectangularly-pulsed orthogonal frequency division multiplexing (OFDM) systems, constant-amplitude (CA) sequences are desirable to construct preamble/pilot waveforms to facilitate system parameter identification (SPI). Orthogonal CA sequences are generally preferred in various SPI applications like random-access channel identification. However, the number of conventional orthogonal CA sequences (e.g., Zadoff-Chu sequences) that can be adopted in cellular communication without causing sequence identification ambiguity is insufficient. Such insufficiency causes heavy performance degradation for SPI requiring a large number of identification sequences. Moreover, rectangularly-pulsed OFDM preamble/pilot waveforms carrying conventional CA sequences suffer from large power spectral sidelobes and thus exhibit low spectral compactness. This paper is thus motivated to develop several order-I CA sequence families which contain more orthogonal CA sequences while endowing the corresponding OFDM preamble/pilot waveforms with fast-decaying spectral sidelobes. Since more orthogonal sequences are provided, the developed order-I CA sequence families can enhance the performance characteristics in SPI requiring a large number of identification sequences over multipath channels exhibiting short-delay channel profiles, while composing spectrally compact OFDM preamble/pilot waveforms.

翻译：在矩形脉冲正交频分复用（OFDM）系统中，恒幅（CA）序列被用于构建前导/导频波形以辅助系统参数识别（SPI）。在各种SPI应用（如随机接入信道识别）中，正交CA序列通常是首选。然而，传统正交CA序列（例如Zadoff-Chu序列）在蜂窝通信中可采用的数目不足，容易导致序列识别歧义。这种不足会导致需要大量识别序列的SPI性能严重下降。此外，携带传统CA序列的矩形脉冲OFDM前导/导频波形存在较大的功率谱旁瓣，因此频谱紧凑性较低。为此，本文开发了多个I阶CA序列族，这些序列族不仅包含更多正交CA序列，还能使对应的OFDM前导/导频波形具有快速衰减的频谱旁瓣。由于提供了更多正交序列，所开发的I阶CA序列族可在短时延信道轮廓的多径环境下，增强需要大量识别序列的SPI性能，同时构成频谱紧凑的OFDM前导/导频波形。