本文選題：大規(guī)模MIMO + 分集傳輸�。� 參考：《浙江大學(xué)》2017年碩士論文

【摘要】：隨著4G進(jìn)入規(guī)模商用的階段,5G的研發(fā)也在如火如茶的展開(kāi)。作為5G中的關(guān)鍵技術(shù)之一,大規(guī)模多輸入多輸出(MIMO)技術(shù)引起了廣泛的關(guān)注。通過(guò)在基站端(BS)配備大規(guī)模天線陣列,大規(guī)模MIMO可以有效地提升系統(tǒng)的能量和頻譜效率。隨著基站天線個(gè)數(shù)的增加,小尺度衰落的影響被平均,不同用戶(hù)到基站之間的信道漸進(jìn)正交,基站端通過(guò)簡(jiǎn)單的線性處理技術(shù)就可以實(shí)現(xiàn)近似臟紙編碼的性能。雖然具有很多潛在的優(yōu)勢(shì),但大規(guī)模MIMO也依然面臨諸多挑戰(zhàn),其中之一就是硬件的復(fù)雜性和巨大開(kāi)銷(xiāo)。如何利用大規(guī)模MIMO所帶來(lái)的優(yōu)勢(shì),簡(jiǎn)化傳輸技術(shù)和降低硬件的復(fù)雜度,是我們所研究的重點(diǎn)。首先,我們考慮了用戶(hù)端配備兩根天線的大規(guī)模MIMO系統(tǒng)的上行鏈路,研究了幾種常見(jiàn)的分集傳輸方式的性能,如正交空時(shí)分組編碼(OSTBC)、最大特征值一發(fā)射波束賦型(TB)和發(fā)射天線選擇(TAS)。為了得到閉合的數(shù)學(xué)表達(dá)式,我們推導(dǎo)了可達(dá)和速率的下界,然后給出了當(dāng)基站天線個(gè)數(shù)M趨于無(wú)窮時(shí),近似的功率放大準(zhǔn)則。解析表達(dá)式表明所研究的分集傳輸方式可以實(shí)現(xiàn)和單天線用戶(hù)系統(tǒng)一樣的功率準(zhǔn)則,同時(shí)用戶(hù)端的多個(gè)天線并不能帶來(lái)明顯的性能增益。因此,為了充分利用用戶(hù)端多天線帶來(lái)的空間維度,應(yīng)當(dāng)設(shè)計(jì)更加先進(jìn)的傳輸方式。然后,考慮到大規(guī)模MIMO系統(tǒng)在實(shí)際實(shí)現(xiàn)過(guò)程中的硬件開(kāi)銷(xiāo),通過(guò)能量有效的相移器將有限的射頻(RF)鏈路和大量的基站天線連接在一起,即采用混合預(yù)編碼的方案。針對(duì)目前多播系統(tǒng)中混合預(yù)編碼研究的限制,我們提出了一種適用于任意信道(瑞利信道和毫米波信道等)的混合預(yù)編碼方案。首先采用傳統(tǒng)的半定松弛(SDR)方法求解,得到近似最佳的全數(shù)字預(yù)編碼,然后通過(guò)最小化和全數(shù)字預(yù)編碼的歐氏距離,基于交替優(yōu)化技術(shù),聯(lián)合設(shè)計(jì)數(shù)字預(yù)編碼和模擬預(yù)編碼。仿真結(jié)果表明在有限個(gè)射頻鏈路的條件下,我們所提出的混合預(yù)編碼方案的性能非常接近全數(shù)字預(yù)編碼的性能。最后,利用大規(guī)模MIMO系統(tǒng)帶來(lái)的信道硬化(即小尺度衰落的影響被平均)的特征,我們提出了一種針對(duì)上行鏈路的多用戶(hù)自適應(yīng)調(diào)制方案,僅需要用戶(hù)端緩慢變化的大尺度陰影衰落的信息,因此具有較低的復(fù)雜度。同時(shí),我們給出了平均頻譜效率(ASE)和誤比特中斷概率(BEO)的閉合表達(dá)式。和傳統(tǒng)的快速自適應(yīng)調(diào)制(FAM)相比,我們所提出的方案可以實(shí)現(xiàn)近似的性能,同時(shí)大大減小了反饋速率和開(kāi)銷(xiāo)。隨后,為了進(jìn)一步提升自適應(yīng)調(diào)制系統(tǒng)的性能,提出了聯(lián)合多用戶(hù)自適應(yīng)調(diào)制和功率控制的方案。
[Abstract]:As 4G enters the scale of commercial phase, the R & D of 5 G is also in the fire as tea. As one of the key technologies in 5 G, large-scale multi-input multi-output (Mimo) technology has attracted wide attention. Large scale MIMO can effectively improve the energy and spectral efficiency of the system by installing a large antenna array at the base station. With the increase of the number of base station antennas, the influence of small-scale fading is averaged. The channel between different users to the base station is gradually orthogonal, and the base station can achieve the performance of approximate dirty paper coding by simple linear processing technology. Although there are many potential advantages, large-scale MIMO still faces many challenges, one of which is the complexity and huge cost of hardware. How to make use of the advantages of large scale MIMO, simplify the transmission technology and reduce the complexity of hardware is the focus of our research. Firstly, we consider the uplink of a large scale MIMO system with two antennas on the client side, and study the performance of several common diversity transmission methods. For example, orthogonal space-time block coding (OSTBC), maximum eigenvalue with a transmit beam type (TB) and antenna selection (TAS). In order to obtain the closed mathematical expression, we derive the lower bound of the reachability sum rate, and then give the approximate power amplification criterion when the number of base station antennas M tends to infinity. The analytical expression shows that the proposed diversity transmission scheme can achieve the same power criterion as the single antenna user system, and that multiple antennas on the client side can not bring about significant performance gains. Therefore, in order to make full use of the spatial dimension brought by multi-antenna, more advanced transmission methods should be designed. Then, considering the hardware overhead of large-scale MIMO system, the limited RF RF link is connected with a large number of base station antennas through an energy-efficient phase shifter, that is, a hybrid precoding scheme is adopted. In view of the limitations of hybrid precoding in multicast systems, we propose a hybrid precoding scheme for arbitrary channels (Rayleigh channel, millimeter-wave channel, etc.). First, the traditional semi-definite relaxation SDR method is used to obtain the approximate optimal all-digital precoding, and then, by minimizing the Euclidean distance between all-digital precoding and all-digital precoding, combining digital precoding and analog precoding based on alternating optimization technique. Simulation results show that the performance of our hybrid precoding scheme is very close to that of full digital precoding under the condition of limited RF links. Finally, we propose a multi-user adaptive modulation scheme for uplink based on the characteristics of channel hardening (i.e. the effects of small-scale fading are averaged) brought by large-scale MIMO systems. It only needs the information of large-scale shadow fading which changes slowly at the user side, so it has low complexity. At the same time, we give the closed expressions of average spectral efficiency (ASE) and error bit interrupt probability (BER). Compared with the traditional fast adaptive modulation (Fam), the proposed scheme can achieve approximate performance and greatly reduce the feedback rate and overhead. Then, in order to further improve the performance of adaptive modulation system, a scheme of combining multi-user adaptive modulation and power control is proposed.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TN919.3
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本文編號(hào)：1968300