5G系統(tǒng)中非正交多址接入技術(shù)的研究
發(fā)布時間：2018-10-22 07:18
【摘要】：第五代移動通信(5G)不僅要實現(xiàn)數(shù)據(jù)流量的爆發(fā)式增長,還要解決大規(guī)模連接和低延遲等問題。為了應(yīng)對這些挑戰(zhàn),NOMA(Non-Orthogonal Multiple Access)可以利用功率域自由度,提高頻譜利用率,成為5G的關(guān)鍵技術(shù)之一。NOMA允許多用戶以不同發(fā)射功率共享頻譜資源,并采用串行干擾消除接收機(jī)實現(xiàn)多用戶檢測。但是,一方面由于NOMA僅根據(jù)信號與干擾加噪聲比這個特征區(qū)分不同用戶的信號,接收機(jī)的性能嚴(yán)重依賴疊加傳輸?shù)挠脩暨x擇和功率分配方案。另一方面,波束成形技術(shù)可以抑制干擾并提高數(shù)據(jù)速率,但受信道狀態(tài)信息(Channel State Information,CSI)估計誤差的影響,NOMA的波束成形設(shè)計穩(wěn)定性較差。針對NOMA接收機(jī)性能嚴(yán)重依賴用戶匹配和功率分配方案的問題,本文研究了多載波NOMA系統(tǒng)中用戶分組和功率分配算法。具體的,在總發(fā)射功率的約束下,研究多載波NOMA下行鏈路的加權(quán)和速率性能的最優(yōu)化問題。由于子載波分配的組合特性,本文分兩步解決所建立的非線性規(guī)劃問題。首先,提出用戶動態(tài)分組方案。通過最大化所有匹配用戶的信道增益差異,所提方案可以提高系統(tǒng)吞吐量。然后,本文采用WMMSE算法來解決非凸的功率分配問題,以低復(fù)雜度的迭代優(yōu)化可獲得局部最優(yōu)解,通過仿真驗證了該算法的收斂性和有效性。針對NOMA波束成形下系統(tǒng)性能穩(wěn)定性受CSI估計誤差影響的問題,本文研究單載波NOMA中多輸入單輸出信道下的穩(wěn)健波束成形設(shè)計。具體的,考慮兩種類型的CSI誤差:二階有界CSI誤差和二階無界CSI誤差。在橢圓區(qū)域限制的有界CSI誤差模型中,本文提出發(fā)射功率約束下的用戶無中斷譯碼的目標(biāo)速率最大化問題。為了解決這個問題,首先將其分解為一系列求功耗最小的優(yōu)化問題。利用凸優(yōu)化理論,可以得到穩(wěn)定的波束成形向量,在存在CSI誤差時仍獲得較高的速率性能。在二階無界CSI誤差模型中,本文研究滿足用戶中斷概率的服務(wù)質(zhì)量下最小化發(fā)送功率的優(yōu)化問題。中斷概率的約束使原問題難以處理,本文通過解決這個問題,獲得可以滿足中斷概率要求的穩(wěn)健波束成形向量。仿真結(jié)果驗證了所提算法的穩(wěn)健性和有效性。
[Abstract]:The fifth generation mobile communication (5G) is not only to achieve explosive growth of data traffic, but also to solve the problems of large-scale connection and low latency. In order to meet these challenges, NOMA (Non-Orthogonal Multiple Access) can make use of the degree of freedom in power domain to improve spectral efficiency and become one of the key technologies of 5G. NOMA allows multiple users to share spectrum resources with different transmit power. And the serial interference cancellation receiver is used to realize multi-user detection. But on the one hand the performance of the receiver depends heavily on the superimposed transmission user selection and power allocation scheme because the NOMA only distinguishes the signals of different users according to the characteristic of the ratio of signal to interference plus noise. On the other hand, beamforming technology can suppress interference and improve data rate, but the stability of NOMA beamforming design is poor due to the estimation error of channel state information (Channel State Information,CSI). In order to solve the problem that the performance of NOMA receiver depends heavily on user matching and power allocation scheme, this paper studies the user packet and power allocation algorithm in multicarrier NOMA system. Specifically, under the constraint of total transmit power, the weighting and rate performance optimization of multicarrier NOMA downlink is studied. Due to the combination of subcarriers, the nonlinear programming problem is solved in two steps. First, a user dynamic grouping scheme is proposed. By maximizing the channel gain difference of all matched users, the proposed scheme can improve the system throughput. Then, WMMSE algorithm is used to solve the non-convex power allocation problem. The local optimal solution can be obtained by low complexity iterative optimization. The convergence and effectiveness of the algorithm are verified by simulation. Aiming at the problem that the performance stability of NOMA beamforming system is affected by the CSI estimation error, the robust beamforming design in single-carrier NOMA with multiple input and single output channels is studied in this paper. Specifically, two types of CSI errors are considered: second order bounded CSI error and second order unbounded CSI error. In the bounded CSI error model with elliptic domain constraints, this paper presents the target rate maximization problem of user uninterrupted decoding under transmit power constraints. In order to solve this problem, it is first decomposed into a series of optimization problems with minimum power consumption. By using convex optimization theory, stable beamforming vector can be obtained, and high rate performance can be obtained with CSI error. In the second order unbounded CSI error model, this paper studies the optimization problem of minimizing transmission power with the quality of service satisfying the outage probability of the user. The constraint of outage probability makes the original problem difficult to deal with. By solving this problem, a robust beamforming vector which can satisfy the requirement of interrupt probability is obtained. Simulation results verify the robustness and effectiveness of the proposed algorithm.
【學(xué)位授予單位】：中國礦業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN929.5
本文編號：2286478
[Abstract]:The fifth generation mobile communication (5G) is not only to achieve explosive growth of data traffic, but also to solve the problems of large-scale connection and low latency. In order to meet these challenges, NOMA (Non-Orthogonal Multiple Access) can make use of the degree of freedom in power domain to improve spectral efficiency and become one of the key technologies of 5G. NOMA allows multiple users to share spectrum resources with different transmit power. And the serial interference cancellation receiver is used to realize multi-user detection. But on the one hand the performance of the receiver depends heavily on the superimposed transmission user selection and power allocation scheme because the NOMA only distinguishes the signals of different users according to the characteristic of the ratio of signal to interference plus noise. On the other hand, beamforming technology can suppress interference and improve data rate, but the stability of NOMA beamforming design is poor due to the estimation error of channel state information (Channel State Information,CSI). In order to solve the problem that the performance of NOMA receiver depends heavily on user matching and power allocation scheme, this paper studies the user packet and power allocation algorithm in multicarrier NOMA system. Specifically, under the constraint of total transmit power, the weighting and rate performance optimization of multicarrier NOMA downlink is studied. Due to the combination of subcarriers, the nonlinear programming problem is solved in two steps. First, a user dynamic grouping scheme is proposed. By maximizing the channel gain difference of all matched users, the proposed scheme can improve the system throughput. Then, WMMSE algorithm is used to solve the non-convex power allocation problem. The local optimal solution can be obtained by low complexity iterative optimization. The convergence and effectiveness of the algorithm are verified by simulation. Aiming at the problem that the performance stability of NOMA beamforming system is affected by the CSI estimation error, the robust beamforming design in single-carrier NOMA with multiple input and single output channels is studied in this paper. Specifically, two types of CSI errors are considered: second order bounded CSI error and second order unbounded CSI error. In the bounded CSI error model with elliptic domain constraints, this paper presents the target rate maximization problem of user uninterrupted decoding under transmit power constraints. In order to solve this problem, it is first decomposed into a series of optimization problems with minimum power consumption. By using convex optimization theory, stable beamforming vector can be obtained, and high rate performance can be obtained with CSI error. In the second order unbounded CSI error model, this paper studies the optimization problem of minimizing transmission power with the quality of service satisfying the outage probability of the user. The constraint of outage probability makes the original problem difficult to deal with. By solving this problem, a robust beamforming vector which can satisfy the requirement of interrupt probability is obtained. Simulation results verify the robustness and effectiveness of the proposed algorithm.
【學(xué)位授予單位】：中國礦業(yè)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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