上鏈LTE單載波頻分多址技術之研究

Abstract

現行第三代合作夥伴計劃(3GPP)長期演進技術(LTE)中，使用正交頻分多址(OFDMA)於下行鏈路以及使用單載波頻分多址(SC-FDMA)於上行鏈路。單載波頻分多址是正交頻分多址的一種改進形式，它是一種在高數據速率傳輸下很有效率的技術。在我們的研究中，我們分析了長期演進技術上行鏈路的數據調變、子載波分配的方法、降低峰均功率比(PAPR)的技術和系統層面的資源塊(resource block)分配。我們觀察到，在集中式單載波頻分多址(Localized SC-FDMA, LFDMA)的峰均功率比性能比正交頻分多址稍微好一點，但遠不如交錯的分布式單載波頻分多址(Interleaved SC-FDMA, IFDMA)，所以我們設計了一個反饋搜索選擇性映射擾碼(Feedback-searching selective mapping)和符號替代方法(Symbol-replaced method)來降低集中式單載波頻分多址的峰均功率比。模擬結果比較了這兩種方法和基本的選擇性映射擾碼再降低峰均功率比上的表現。最後，我們提出了一個誤碼率增強貪婪式演算法(BER-enhanced greedy method)，在某些假設條件下資源塊可以被分配更有效率。模擬結果表示，此方法誤碼率(BER)的性能有很好的提升。

The current standard in 3rd Generation partnership project (3GPP) Long-Term Evolution (LTE) uses orthogonal FDMA (OFDMA) for downlink and single carrier FDMA (SC-FDMA) for uplink. SC-FDMA is a modified form of OFDMA, and it is a promising technique for high data rate transmission. In our research, we analyze the LTE uplink in the data modulations, subcarrier mapping schemes, techniques for PAPR reduction and resource allocations. We observe that the PAPR performance in localized SC-FDMA (LFDMA) is slightly better than OFDMA, but much worse than interleaved SC-FDMA (IFDMA), so we design feedback searching selective mapping and symbol-replaced methods that reduce the PAPR of LFDMA signals. The numerical results reveal their performance in reducing PAPR compared with basic SLM. Finally we propose a BER-enhanced greedy method, which assigns the resource blocks more efficiently under certain assumptions. The simulation results show that the proposed method has a great performance improvement in bit error rate (BER).