【摘要】：協(xié)作通信技術(shù)由于能夠抵抗信道衰落的影響,提供分集增益,因此成為無(wú)線通信領(lǐng)域研究的熱點(diǎn)。為了能夠有效地提升系統(tǒng)性能和降低資源消耗,協(xié)作中繼的選擇、中繼協(xié)作的方式和引入中繼的時(shí)機(jī)等問(wèn)題已經(jīng)成為重要的研究?jī)?nèi)容。本文將深入研究協(xié)作通信系統(tǒng)中的中繼選擇及其優(yōu)化問(wèn)題。首先,對(duì)協(xié)作通信的研究背景、研究現(xiàn)狀以及實(shí)際應(yīng)用做了簡(jiǎn)單的介紹。其次簡(jiǎn)要分析和歸納了典型的中繼轉(zhuǎn)發(fā)策略和中繼選擇方案的優(yōu)缺點(diǎn)。最后對(duì)中繼選擇方案及其優(yōu)化問(wèn)題展開(kāi)研究。本文的主要內(nèi)容和創(chuàng)新點(diǎn)如下:(1)為了提高中繼選擇方案的靈活性和降低系統(tǒng)開(kāi)銷,引入自動(dòng)請(qǐng)求重傳技術(shù),結(jié)合混合譯碼放大轉(zhuǎn)發(fā)(HDAF)中繼策略,提出了一種基于接收信噪比最大化的改進(jìn)HDAF單中繼選擇方案。通過(guò)目的節(jié)點(diǎn)發(fā)送的三種反饋信息來(lái)決定信息傳輸?shù)姆绞�。信息傳輸方式包�?直接傳輸、源節(jié)點(diǎn)重傳和引入中繼。通過(guò)理論和仿真分析得出:改進(jìn)HDAF的中繼選擇方案不僅能夠有效地降低中斷概率,而且大大提高了頻譜效率,從而提高了信息傳輸?shù)目煽啃院挽`活性。在中斷概率為-210時(shí),與基于HDAF的中繼選擇方案相比,改進(jìn)方案能夠獲得1dB的信噪比增益。另外,隨著候選中繼個(gè)數(shù)的增加,中斷概率性能的改善更加明顯。(2)為了降低能量消耗以及方案運(yùn)算復(fù)雜度,以誤碼率最小化為目標(biāo),提出了一種在HDAF中繼策略下的最優(yōu)中繼集合的快速選擇方案。首先,采用矩量母函數(shù)原理推導(dǎo)得出基于放大轉(zhuǎn)發(fā)(AF)、譯碼轉(zhuǎn)發(fā)(DF)和HDAF中繼策略的多中繼系統(tǒng)的誤碼率近似表達(dá)式。然后以此為中繼選擇的依據(jù),巧妙地定義了HDAF等效信道增益,快速選擇出最優(yōu)中繼集合。接著,針對(duì)選擇單個(gè)最優(yōu)中繼的情況,為使誤碼率達(dá)到實(shí)際的需求值,求解了最優(yōu)功率分配問(wèn)題。結(jié)果表明:首先,誤碼率性能能夠得到有效的提升;其次,與窮舉算法相比,誤碼率性能相近但運(yùn)算復(fù)雜度大大降低;最后,最優(yōu)功率分配能夠降低系統(tǒng)總功耗。在相同誤碼率限定值下,與AF、DF方案相比,所提方案能夠降低1dB-1.5dB的總功率消耗。此外,與等功率分配相比,所提方案能夠節(jié)約0.2dB左右的總功率,從而在降低誤碼率和系統(tǒng)總功耗的問(wèn)題上達(dá)到折中,使中繼選擇更具有實(shí)際意義。
[Abstract]:Cooperative communication technology has become a hotspot in wireless communication field because it can resist the influence of channel fading and provide diversity gain. In order to effectively improve system performance and reduce resource consumption, the selection of cooperative relay, the mode of relay cooperation and the timing of introducing relay have become important research contents. This paper will study the relay selection and its optimization in cooperative communication systems. Firstly, the research background, research status and practical application of cooperative communication are briefly introduced. Secondly, the advantages and disadvantages of typical relay forwarding strategies and relay selection schemes are briefly analyzed and summarized. Finally, the relay selection scheme and its optimization are studied. The main contents and innovations of this paper are as follows: (1) in order to improve the flexibility of relay selection scheme and reduce system overhead, automatic request retransmission technology is introduced, combined with hybrid decoding, amplifying and forwarding (HDAF) relay strategy. In this paper, an improved HDAF single relay selection scheme based on maximization of reception signal-to-noise ratio (SNR) is proposed. The mode of information transmission is determined by three kinds of feedback information sent by the destination node. The modes of information transmission include direct transmission, retransmission of source node and introduction of relay. Through theoretical and simulation analysis, it is concluded that the improved relay selection scheme of HDAF can not only effectively reduce the interrupt probability, but also greatly improve the spectral efficiency, thus improving the reliability and flexibility of information transmission. When the outage probability is -210, compared with the relay selection scheme based on HDAF, the improved scheme can obtain the SNR gain of 1dB. In addition, with the increase of the number of candidate relays, the improvement of outage probability performance is more obvious. (2) in order to reduce the energy consumption and the computational complexity of the scheme, the goal is to minimize the bit error rate (BER). A fast selection scheme for optimal relay set under HDAF relay strategy is proposed. Firstly, an approximate expression of BER for multi-relay systems based on amplifying and forwarding (AF), decoding and forwarding (DF) and HDAF relay strategies is derived by using the principle of mother moment function. Based on this, the equivalent channel gain of HDAF is defined skillfully, and the optimal relay set is quickly selected. Then, the optimal power allocation problem is solved for the case of selecting a single optimal relay in order to make the BER reach the actual requirement value. The results show that: first, the BER performance can be effectively improved; secondly, compared with exhaustive algorithm, the BER performance is similar but the computational complexity is greatly reduced; finally, the optimal power allocation can reduce the total power consumption of the system. Under the same BER limit, compared with the AF,DF scheme, the proposed scheme can reduce the total power consumption of 1dB-1.5dB. In addition, compared with the equal-power allocation, the proposed scheme can save the total power of the 0.2dB, thus achieving a compromise between reducing the bit error rate and the total power consumption of the system, and making the relay selection more meaningful.
【學(xué)位授予單位】：杭州電子科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN914

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