發(fā)布時間：2018-04-28 17:35

  本文選題：5G + 稀疏碼分多址接入�。� 參考：《電子科技大學(xué)》2017年碩士論文

【摘要】：近年來,移動智能終端的普及、移動互聯(lián)網(wǎng)、新業(yè)務(wù)的蓬勃發(fā)展促使移動通信系統(tǒng)需要提供滿足用戶需求的服務(wù)�，F(xiàn)有的通信系統(tǒng)已不能滿足海量用戶低延遲、高速率的通信需求,因此稀疏碼分多址接入(Sparse Code Multiple Access,SCMA)被提出。它使海量用戶以過載的方式復(fù)用頻譜資源,同時SCMA用戶可以采用Grant-free機制降低通信延遲,因此SCMA成為一項第五代移動通信系統(tǒng)(The 5th Generation,5G)中具有巨大應(yīng)用前景的多用戶多址方式�，F(xiàn)有關(guān)于SCMA的研究主要集中在碼本設(shè)計、低復(fù)雜度接收機設(shè)計上,而關(guān)于它的傳輸技術(shù)研究相對較少。通信系統(tǒng)的傳輸技術(shù)如能效優(yōu)化設(shè)計、混合自動重傳請求(Hybrid Automatic Repeat Request,HARQ)技術(shù)影響系統(tǒng)的吞吐量、能效、接收可靠性等,因此研究系統(tǒng)的傳輸技術(shù)具有重要意義。鑒于SCMA對未來通信網(wǎng)絡(luò)的重要研究意義及SCMA傳輸技術(shù)研究的不足,本文主要對SCMA系統(tǒng)的能效優(yōu)化設(shè)計、HARQ技術(shù)進行研究。首先,本文對SCMA系統(tǒng)的能效優(yōu)化設(shè)計進行了研究。提出了兩種能效優(yōu)化模型,第一個優(yōu)化問題的目標函數(shù)為系統(tǒng)所有用戶的能效和最優(yōu),第二個優(yōu)化問題的目標函數(shù)為使系統(tǒng)最差鏈路的用戶能效最優(yōu),兩個能效優(yōu)化問題均保證了SCMA用戶的最小傳輸速率要求。根據(jù)所提的兩個能效優(yōu)化問題,設(shè)計了兩種算法,其基本思想為參量優(yōu)化迭代。首先引入?yún)⒘?將分數(shù)目標函數(shù)形式轉(zhuǎn)為含有參量的凹函數(shù),用庫恩塔克條件(Karush-Kuhn-Tucker,KKT)求解得到能效最優(yōu)的用戶功率分配方案后,更新參量,繼續(xù)求解優(yōu)化問題,直至優(yōu)化解滿足收斂條件。仿真結(jié)果表明,設(shè)計的兩種能效優(yōu)化算法分別解決了給定模型下的能效優(yōu)化問題,具有較好的收斂性。此外,對比兩種能效優(yōu)化算法,可知能效最優(yōu)不能保證傳輸速率最優(yōu)。隨后,本文對SCMA系統(tǒng)的可靠性提升進行了研究。根據(jù)傳統(tǒng)消息傳遞算法(Message Passing Algorithms,MPA)檢測器的譯碼特點,提出了一種部分碼字信息已知的MPA譯碼器(Part Information based MPA,PI-MPA),定性分析了它相比傳統(tǒng)MPA提高譯碼準確性的原理�；赑I-MPA構(gòu)造了一種高可靠性的SCMA-HARQ系統(tǒng),通過分析正確重傳碼字數(shù)目對系統(tǒng)吞吐量和重傳延遲的影響,本文設(shè)計了一種基于用戶QoS分組的部分正確碼字動態(tài)重傳算法機制。將所有用戶分為兩組,只從QoS較低的那組選擇可利用冗余重傳用戶進行重傳,且執(zhí)行冗余重傳的用戶數(shù)目根據(jù)當前傳輸錯誤的用戶數(shù)目自適應(yīng)確定。仿真結(jié)果表明,本文提出的基于PI-MPA的高可靠SCMA-HARQ系統(tǒng)相比傳統(tǒng)的SCMA-HARQ系統(tǒng)具有很小的重傳延遲性能損失,但可靠性和吞吐性能明顯增強。
[Abstract]:In recent years, with the popularity of mobile intelligent terminals, the rapid development of mobile Internet and new services, mobile communication systems need to provide services to meet the needs of users. The existing communication systems can no longer meet the low delay and high speed communication requirements of mass users, so sparse CDMA access (parse Code Multiple access) is proposed. It enables mass users to reuse spectrum resources in an overload manner, and SCMA users can use Grant-free mechanism to reduce communication delay. Therefore, SCMA has become a multiuser multiple access mode with great application prospects in the 5th Generation 5G (the fifth generation mobile communication system). The current research on SCMA is mainly focused on codebook design, low complexity receiver design, but less research on its transmission technology. The transmission technology of communication system, such as energy efficiency optimization design, hybrid automatic retransmission request hybrid Automatic Repeat request HARQ technology, affects the throughput, energy efficiency and receiving reliability of the system, so it is of great significance to study the transmission technology of the system. In view of the importance of SCMA to the future communication network and the shortage of SCMA transmission technology, this paper mainly studies the energy efficiency optimization design of SCMA system and HARQ technology. Firstly, the energy efficiency optimization design of SCMA system is studied. Two energy efficiency optimization models are proposed. The objective function of the first optimization problem is the energy efficiency and optimization of all users of the system, and the objective function of the second optimization problem is to optimize the energy efficiency of the users of the worst link of the system. The two energy efficiency optimization problems ensure the minimum transmission rate requirement of SCMA users. According to the two energy efficiency optimization problems proposed, two algorithms are designed, whose basic idea is parametric optimization iteration. First, the parameter is introduced, the form of fractional objective function is transformed into a concave function with parameters, and the Karush-Kuhn-Tuckern KKT condition is used to solve the optimal user power allocation scheme for energy efficiency, then the parameters are updated and the optimization problem is solved. Until the optimal solution satisfies the convergence condition. The simulation results show that the proposed two energy efficiency optimization algorithms can solve the energy efficiency optimization problem under a given model and have good convergence. In addition, compared with the two energy efficiency optimization algorithms, the energy efficiency optimization can not guarantee the optimal transmission rate. Then, this paper studies the reliability enhancement of SCMA system. According to the decoding characteristics of the traditional message Passing algorithm (MPA) detector, a part Information based MPA-PI-MPAA decoder with known part of codeword information is proposed. The principle of improving the decoding accuracy compared with the traditional MPA is analyzed qualitatively. A high reliability SCMA-HARQ system is constructed based on PI-MPA. By analyzing the influence of the number of correct retransmitted codewords on system throughput and retransmission delay, a partial correct codeword dynamic retransmission algorithm based on user QoS packet is designed in this paper. All users are divided into two groups, and the number of users performing redundant retransmission can be determined adaptively according to the number of users whose current transmission error is based on the number of users who can use redundant retransmission users only from the group with lower QoS. The simulation results show that the proposed high reliability SCMA-HARQ system based on PI-MPA has less performance loss of retransmission delay than the traditional SCMA-HARQ system, but the reliability and throughput performance is obviously enhanced.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN929.5

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