| 摘要: | 隨著行動通訊的飛速發展，對頻譜效率的需求也迅速增長，傳統的正交多重存取 (Orthogonal multiple access, OMA)已經無法滿足現今用戶的需求，為了滿足對行動通訊服務的需求，非正交多重存取被認為是第五代行動通訊中的關鍵多重存取技術之一。在正交多重存取中，一個用戶只能分配一個正交資源，不論是在時域、頻域或碼域，而非正交多重存取 (Non-orthogonal multiple access, NOMA)可以將一個資源分配給多個用戶，也因為出色的頻譜效率和巨量的連接性，它也引起了相當大的關注。
目前NOMA主要的接收機設計是連續干擾消除 (Successive interference cancellation, SIC)為主，通過消除干擾訊號的分量，使用戶端能夠從疊加的發射信號中分離出自己需要的信號，也因此合理分配訊號的功率對NOMA來說尤為重要，所以如果信號的功率分配太過接近，就會造成錯誤率增加。因此，本文將介紹另一種接收器設計，其中在發送端使用聯合調變 (Joint detection, JD)的方式，將來自不同用戶的位元通過格雷映射在一個符號中共同調變，並在接收器藉由聯合偵測來處理訊號。本文將比較兩種接收機設計，並引入即時功率分配 (Real time power allocation, RTPA)演算法，以改善兩種接收機設計的錯誤率，最後再比較RTPA下的兩種接收機設計。模擬結果表明，聯合檢測的錯誤率明顯優於SIC，而在引入RTPA算法後，聯合檢測仍能維持較好的錯誤率。
;With the rapid development of mobile communications, the demand for spectrum efficiency has grown fast, and the traditional orthogonal multiple access (OMA) has been unable to satisfy the requirements of user. In order to fulfill the requirements for mobile services, non-orthogonal multiple access (NOMA) are considered as a key technology for fifth generation mobile communication. In OMA, one user can be assigned a single orthogonal resource, either in time, frequency or code domain, while NOMA can allocate one resource to multiple users. It also received considerable attention due to its superior spectral efficiency and massive connectivity.
In present, the main receiver design of NOMA is successive interference cancellation (SIC). It enables user to separate its own desired signal from superposed transmitted signal by canceling out the interference signal. So, it is especially important to make reasonable power allocation of signal for NOMA. If power allocation of signal is too close, the error rate will be increased. Therefore, we will introduce another receiver design, where joint modulation scheme is used at the transmitted side. The bits from different users are jointly modulated in one symbol with Gray mapping. And the Joint detection is used at the receiver to process information.
This paper will compare the two method, and introduce real-time power allocation (RTPA) algorithm to improve the bit error rate of two receiver design. Finally, compare two receiver design under RTPA algorithm. Simulation show that joint detection is better than SIC in bit error rate, and after introduce RTPA algorithm, joint detection still better. |
