第五代巨量天線徑分多重接取蜂巢式系統中使用不同領航序列進行通道估計之研究

Abstract

在未來十年，現有的通訊標準明顯已不符合未來第五代行動通訊所需。為了因應這個問題，我們研究第五代的蜂巢式系統可能的技術之一，也就是時分雙工巨量天線徑分多重(MDMA)接取蜂巢式系統。本論文研究用於第五代行動通訊系統通道估計的領航序列，我們探討正交分頻多工(OFDM)系統，在上行(UL)採用最大比值合併(MRC)，然後使用不同的領航序列結合資料序列作為我們在上行的傳送訊號，並且在基地台(BS)端估計通道。我們使用平行干擾消除(PIC)的方法，能使得位元錯誤率(BER)可以有很好地改善，並且在正交分頻多工系統的通道估計中合併領航序列及使用者資料(user data)協助通道估計，用以和原本只單純用領航序列估計通道做比較。此外，我們對於Zadoff-Chu序列做了循環位移以增加同一Zadoff-Chu序列的使用效益，此方法可以有效降低其它用使用者間的互相干擾，使得在通道估計誤差方面有著比原本Zadoff-Chu序列更好的表現。最後，我們在正交分頻多工系統中比較使用不同領航序列的情況下，每種領航序列在能容納的使用者數目上的差異性。

In next ten years, existing communication standards obviously cannot meet with the needs of future 5G mobile communications. In response to this, we research on one of the possible techniques in 5G cellular system, which is a TDD massive antenna multipath division multiple access (MDMA) system. In this thesis, channel estimation for massive antenna MDMA mobile radio communication system based on different pilot sequences are investigated. We explored Orthogonal Frequency-Division Multiplexing (OFDM) and adopt maximum ratio combining in uplink (UL). We use different pilot sequences combined with data sequence as our transmitted signal in UL and estimate channels at base station (BS). With parallel interference cancellation (PIC) method, bit error rate (BER) can be improved further. We also utilize the method of combining user data and pilot sequence together to estimate channels. Besides, we do circular shift on Zadoff-Chu sequences and find that it has better performance than traditional Zadoff-Chu sequence. Finally, for the OFDM system, we use different pilot sequences to analyze the number of users which can be served by the MDMA system.