用於高頻譜效益正交分頻多工系統中系統參數識別之正交恆定振幅序列集

Abstract

在矩形脈衝正交分頻多工系統中，恆定振幅序列對於構建前導/領航波形以促進系統參數識別非常有用。在各種系統參數識別應用中，如隨機接入通道識別和多輸入多輸出系統中的上行通道探測，通常優先採用正交恆定振幅序列。然而，在現行的無線通訊標準中採用的傳統正交恆定振幅序列（例如Zadoff-Chu序列）數量不足。這種不足會導致需要大量識別序列的系統參數識別性能嚴重降低。此外，攜帶傳統恆定振幅序列的矩形脈衝正交分頻多工前導/領航波形會受到大的旁帶頻譜功率影響，因此具有較低的頻譜緊密度。因此，本文旨在開發幾個I階恆定振幅序列集，其中包含更多正交恆定振幅序列，同時賦予相應的正交分頻多工前導/領航波形高頻譜緊密度。由於提供了更多正交序列，所開發的I階恆定振幅序列集可以增強在呈現短延遲的多路徑通道上之系統參數識別性能特性，同時構成頻譜緊密的正交分頻多工前導/領航波形。

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 and uplink channel sounding in multiple-input multiple-output systems. However, the number of conventional orthogonal CA sequences (e.g., Zadoff-Chu sequences) that can be adopted in popular wireless communication standards 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 over multipath channels exhibiting short-delay channel profiles, while composing spectrally compact OFDM preamble/pilot waveforms.