正交分頻多工於符元訊號程序之子載波分配研究

OFDM symbol-based processing with subcarrier allocation

陳昱達(Yu-Ta Chen)

指導教授 ： 李彥文

國立暨南國際大學/科技學院/電機工程學系/碩士(2012年)

https://doi.org/10.6837/NCNU.2012.00158

摘要

我們將於本論文中討論關於上行的多使用者(Multiuser，MU)多重輸入多重輸出(Multiple Input Multiple Output，MIMO)在多載波系統伴隨通道編碼(Channel Coding)系統之效能，以探討空間分集(Space Diversity)和頻率分集(Frequency Diversity)對系統之影響。我們知道基於子載波訊號處理方法雖然可以得到最佳的系統效能，但亦伴隨著很高的複雜度。因此，近代有研究提出基於符元訊號處理之技術，即在傳送端/接收端分別只需要使用一個反快速傅立葉/快速傅立葉轉換，從而大幅降低複雜度。傳統基於符元訊號處理之準則主要為最大化所有子載波的訊號訊雜比總和，此方法之缺點為子載波的訊號訊雜比在衰減干擾較嚴重的情況下會產生無法平衡的現象，造成整個系統的效能下降。因此我們在基於符元訊號處理的前提之下，提出了使用最大-最小公平準則(Max-Min Fair Criterion)的方法來解決此問題，並利用其伴隨著較低複雜度的正半定放寬(Semidefinite Relaxation，SDR)來求解。在論文的第一個部份，我們於多使用者多重輸入多重輸出之正交分頻多工存取系統下並考慮傳送端已知的通道狀態資訊(Channel State Information，CSI)之情況，在傳送端進行傳輸波束成形(Beamforming)，之後再加入不同的子載波分配(Subcarrier allocation)方法以強化系統效能。在論文的第二部份，為了解決正交分頻多工存取所造成的高峰值平均功率比(Peak-to-Average Power Ratio, PAPR)，我們提出了在單載波分頻多工存取系統(Single-carrier Frequency-Division Multiple Access，SC-FDMA)中使用最大-最小準則，並同樣加入子載波分配以達到更佳的系統效能。最後我們將於不同之訊號處理準則和環境下模擬所提出之系統效能。

關鍵字

正交分頻多工存取 ； 單載波正交分頻多工存取 ； 多重輸入多重輸出 ； 多使用者 ； 上行 ； 正半定放寬 ； 最大-最小公平準則 ； 子載波分配 ； 波束成形

並列摘要

In this thesis, we discuss the performance of uplink multiuser (MU) multiple input multiple output (MIMO) multicarrier systems with channel coding. The effect of space and frequency diversities is then studied. In this aspect, it is known that subcarrier-based signal processing techniques can provide the best performance. However, the computational complexity will be prohibitively high. Therefore, symbol-based processing techniques have recently been proposed for complexity reduction. Only one inverse discrete fourier transform (IDFT)/DFT block is required at the transmitter/receiver. Conventional symbol-based processing is to maximize the sum of the signal-to-noise ratio (SNR) values achieved in all subcarriers. The disadvantage of it is that the SNR performance of different subcarriers is often not balanced in deep fading channel. This will degrade the whole system performance. Here, to solve this problem, we propose to use the max-min fair criterion for symbol-based processing. Semidefinite relaxation (SDR) is used to approximate the solution with low complexity. In the first part of the thesis, we consider the scenario in which channel state information (CSI) is known at the transmitter, and then transmit beamforming is employed for the MU-MIMO-OFDMA system. After that, we propose to use subcarrier allocation methods for such system to funther enhance the performance. In the second part of the thesis, to solve the problem of high Peak-to-Average Power Ratio (PAPR), we propose to use the max-min fair criterion for symbol-based processing in MU-MIMO-SC-FDMA(Single-carrier Frequency-Division Multiple Access，SC-FDMA) systems, and also use subcarrier allocation methods for performance improvement. Finally, simulation results are provided to show the performance of difference schemes under difference environment settings.

並列關鍵字

OFDMA ； SC-FDMA ； MIMO ； multiuser ； Uplink ； SDR ； Max-Min Fair Criterion ； Subcarrier allocation ； Beamforming

參考文獻

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