【摘要】：作為協(xié)作中繼技術(shù)之一的雙向中繼由于可以顯著地提高無線通信網(wǎng)絡(luò)中的頻譜效率而得到極大的關(guān)注,但現(xiàn)有的大部分研究都集中在雙向中繼的物理層,且部分基于統(tǒng)計時延保障的跨層功率分配僅考慮單向中繼信道。目前涉及雙向中繼的跨層優(yōu)化研究較少,雙向中繼傳輸對于上層帶來的影響也未被充分挖掘。本文針對上述問題,利用可以在數(shù)據(jù)鏈路層和物理層間交換信息的QoS(Qua1ity of Service)指數(shù)來表征統(tǒng)計時延需求,在保障數(shù)據(jù)鏈路層統(tǒng)計時延需求的前提下,優(yōu)化功率的分配使得雙向中繼系統(tǒng)的性能最優(yōu)。論文首先概述了雙向中繼通信系統(tǒng)的基本模型和物理層網(wǎng)絡(luò)編碼的基本概念,簡述中繼傳輸協(xié)議中應(yīng)用最為廣泛的兩類:放大轉(zhuǎn)發(fā)協(xié)議(Amp1ify-and-Forward)和譯碼轉(zhuǎn)發(fā)協(xié)議(Decode-and-Forward)。然后利用有效容量理論得到一種基于時延QoS保障的跨層雙向中繼系統(tǒng)模型,建立了上層數(shù)據(jù)鏈路層與物理層之間的聯(lián)系,把尋找最優(yōu)化傳輸方案問題建模為求解系統(tǒng)有效容量加權(quán)和最大值的問題。并且可以證明該問題是一個凸優(yōu)化問題,存在唯一的最優(yōu)解。論文接著對基于AF協(xié)議的雙向中繼系統(tǒng)進行最優(yōu)跨層功率分配的求解。首先分別求得不同時隙下雙向中繼的可達速度域,再將不同速率代入有效容量加權(quán)和最大化問題中,通過拉格朗日乘子法針對不同的場景(例如兩時隙的固定增益或放大增益雙向中繼系統(tǒng)、三時隙的固定增益或放大增益雙向中繼系統(tǒng))下的不同最大化問題進行求解,給出最優(yōu)功率分配因子的算法,最終得到最優(yōu)的功率分配方案。仿真結(jié)果表明對于放大轉(zhuǎn)發(fā)雙向中繼系統(tǒng),論文給出的最優(yōu)功率分配方案與等功率分配方案、直接傳輸方案相比能顯著地提高系統(tǒng)性能。論文最后對基于DF協(xié)議的雙向中繼系統(tǒng)最優(yōu)跨層功率分配進行了分析討論。由于在兩時隙雙向中繼中存在誰先譯碼用戶節(jié)點信息的問題,所以在基于等時隙分配的情況下,給出了兩時隙協(xié)議中MAC階段連續(xù)譯碼的最優(yōu)信道狀態(tài)區(qū)域劃分準(zhǔn)則,并以此準(zhǔn)則確定用戶節(jié)點譯碼的先后順序和不同劃分區(qū)域下的最大速率表達式。利用次梯度法更新λ至最優(yōu)值和拉格朗日乘子法求偏導(dǎo)數(shù),分別得到三時隙與兩時隙的最優(yōu)功率分配因子算法和最優(yōu)功率分配方案。仿真結(jié)果表明在低信噪比情況下兩時隙控制協(xié)議更有優(yōu)勢,在高信噪比情況下三時隙控制協(xié)議更有優(yōu)勢。
[Abstract]:As one of the cooperative relay technologies, bidirectional relay has attracted much attention because it can significantly improve the spectrum efficiency in wireless communication networks. However, most of the existing researches are focused on the physical layer of bidirectional relay. And the cross-layer power allocation based on statistical delay guarantee only considers unidirectional relay channel. At present, there are few researches on cross-layer optimization of bidirectional relay, and the influence of bidirectional relay transmission on upper layer is not fully exploited. In order to solve the above problems, QoS (Qua1ity of Service) exponent), which can exchange information between the data link layer and the physical layer, is used to represent the demand of statistical delay. Optimal power allocation makes the performance of bidirectional relay system optimal. Firstly, the basic model of bidirectional relay communication system and the basic concept of physical layer network coding are summarized. The two most widely used relaying protocols are amplified forwarding protocol (Amp1ify-and-Forward) and decoded forwarding protocol (Decode-and-Forward). Based on the effective capacity theory, a cross-layer two-way relay system model based on delay QoS is proposed, and the relationship between the upper layer data link layer and the physical layer is established. The problem of finding an optimal transmission scheme is modeled as the problem of solving the weighted and maximum effective capacity of the system. It can be proved that the problem is a convex optimization problem with unique optimal solution. Then, the optimal cross-layer power allocation is solved for the bidirectional relay system based on AF protocol. First, the reachable speed domain of two-way relay in different time slots is obtained, and then the different rates are substituted into the effective capacity weighting and maximization problem. The Lagrange multiplier method is used to solve different maximization problems in different scenarios such as bidirectional relay system with fixed gain or amplification gain with two slots and bidirectional relay system with fixed gain or amplification gain with three slots. The algorithm of the optimal power allocation factor is given, and the optimal power allocation scheme is obtained. The simulation results show that the proposed optimal power allocation scheme can significantly improve the system performance compared with the equal power allocation scheme for amplifying and forwarding bidirectional relay systems. Finally, the optimal cross-layer power allocation of bidirectional relay system based on DF protocol is analyzed and discussed. Because of the problem of who first decodes the user node information in two-slot bidirectional relay, the optimal channel state region partition criterion for MAC phase continuous decoding in two-slot protocol is given based on equal time slot allocation. The order of decoding and the maximum rate expression under different partition regions are determined by this criterion. The sub-gradient method is used to update the 位 to optimal value and Lagrange multiplier method to obtain the partial derivative. The optimal power allocation factor algorithm and the optimal power allocation scheme for the three time slots and two time slots are obtained respectively. The simulation results show that the two-slot control protocol is more advantageous in the case of low signal-to-noise ratio, and the three-slot control protocol is more advantageous in the case of high signal-to-noise ratio.
【學(xué)位授予單位】：安徽大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN92

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