本文選題：快時(shí)變信道 + 自適應(yīng)調(diào)制編碼�。� 參考：《杭州電子科技大學(xué)》2017年碩士論文

【摘要】：高速鐵路環(huán)境作為高速移動(dòng)典型的應(yīng)用場(chǎng)景之一,相對(duì)低速情況下需要更穩(wěn)定可靠的通信系統(tǒng)支撐。高移動(dòng)性加劇了無(wú)線信道時(shí)變程度,在如此惡劣的信道環(huán)境下,提供穩(wěn)定可靠的高數(shù)據(jù)傳輸速率的用戶(hù)體驗(yàn)成為一項(xiàng)需要深入研究的課題。本文圍繞高速移動(dòng)環(huán)境及高鐵場(chǎng)景下,對(duì)自適應(yīng)調(diào)制編碼(Adaptive Modulation and Coding,AMC)中信道質(zhì)量指示(Channel Quality Index,CQI)自適應(yīng)調(diào)整算法和頻率同步進(jìn)行研究,具體完成的工作如下:首先,介紹移動(dòng)通信的發(fā)展以及高速鐵路專(zhuān)用通信系統(tǒng)演進(jìn)方向,分析高速移動(dòng)環(huán)境下通信系統(tǒng)面臨的問(wèn)題以及國(guó)內(nèi)外有關(guān)高移動(dòng)環(huán)境下的研究熱點(diǎn)。其次,介紹無(wú)線信道的傳播特性和高速環(huán)境下的衰落信道,并對(duì)高鐵環(huán)境的信道特點(diǎn)進(jìn)行闡述以及現(xiàn)有的高鐵場(chǎng)景信道模型。此外,介紹幾種高速鐵路無(wú)線接入網(wǎng)絡(luò)覆蓋方案,如單個(gè)基帶處理單元(Base Band Unite,BBU)+多個(gè)射頻遠(yuǎn)端單元RRU(Remote Radio Unite,RRU)的覆蓋方式。然后,根據(jù)標(biāo)準(zhǔn)中15種調(diào)制編碼方式以及對(duì)應(yīng)的碼率在加性高斯白噪聲(Additive White Gaussian Noise,AWGN)信道下仿真獲得目標(biāo)誤塊率對(duì)應(yīng)的信噪比,建立CQI切換的閾值表,同時(shí)引入有效信噪比映射,用單個(gè)信噪比值代表多狀態(tài)信道以降低復(fù)雜度。針對(duì)CQI固定上報(bào)周期的問(wèn)題,本文提出一種適用于高速移動(dòng)環(huán)境下AMC系統(tǒng)中CQI自適應(yīng)調(diào)整算法和方案,其通過(guò)統(tǒng)計(jì)幀內(nèi)相鄰符號(hào)上的信噪比差值來(lái)評(píng)估當(dāng)前信道變化程度,并利用評(píng)估結(jié)果來(lái)預(yù)測(cè)未來(lái)信噪比變化程度。接著基于CQI的量化顆粒度來(lái)計(jì)算CQI反饋周期自適應(yīng)調(diào)整量,使CQI反饋負(fù)載和吞吐量性均能獲得相對(duì)較好的性能。最后通過(guò)計(jì)算機(jī)仿真驗(yàn)證了本文提出方案的可行性和有效性。最后,在高速移動(dòng)環(huán)境下對(duì)頻率同步算法性能的影響進(jìn)行分析。針對(duì)多普勒頻偏和晶振頻偏同時(shí)存在的情況下,采用一種正交角域子空間算法,將接收信號(hào)投影到各個(gè)子空間,并對(duì)各子空間內(nèi)的等效多普勒頻偏進(jìn)行估計(jì),獲得多普勒頻偏和晶振頻偏的混合頻偏,然后利用估計(jì)的混合頻偏對(duì)各子空間內(nèi)的接收信號(hào)補(bǔ)償,達(dá)到頻率同步的效果。仿真結(jié)果表明,未對(duì)估計(jì)值進(jìn)行自回歸(Autoregressive,AR)濾波能獲得較好的誤碼率性能,這是由于多普勒頻偏呈現(xiàn)快速時(shí)變,造成濾波無(wú)法提高估計(jì)值的精度,還增加估計(jì)噪聲。此外,該算法在大部分采樣位置上能夠有效降低誤比特?cái)?shù),僅在到達(dá)角快變情況下特別是在某些特殊場(chǎng)景如到達(dá)區(qū)域(Arrival Area,AA)和切換區(qū)域呈現(xiàn)較高的誤比特?cái)?shù)。
[Abstract]:As one of the typical application scenarios of high-speed movement, high-speed railway environment needs more stable and reliable communication system support than at low speed. High mobility intensifies the time-varying degree of wireless channel. In such a bad channel environment, providing a stable and reliable user experience with high data transmission rate has become a subject that needs further study. In this paper, the adaptive Modulation and coding algorithm and frequency synchronization of CITIC channel quality indication channel Quality index (CQI) are studied in high speed mobile environment and high-speed railway scene. The detailed work is as follows: first of all, This paper introduces the development of mobile communication and the evolution direction of high-speed railway special communication system, analyzes the problems faced by the communication system in high-speed mobile environment and the research hot spots at home and abroad on the high mobile environment. Secondly, the propagation characteristics of wireless channel and fading channel in high-speed environment are introduced, and the channel characteristics of high-speed rail environment and the existing high-speed rail scene channel model are described. In addition, several high-speed railway wireless access network coverage schemes, such as a single baseband processing unit (Base Band Unite BBU), multiple radio frequency remote units (RRU(Remote Radio Unite RRU), are introduced. Then, according to the 15 modulation coding schemes and the corresponding bit rates in the standard, the SNR corresponding to the target block error rate is obtained by simulation under the additive White Gaussian noise channel, and the threshold table of CQI handoff is established, and the effective signal-to-noise ratio mapping is introduced. The multistate channel is represented by a single signal-to-noise ratio (SNR) value to reduce the complexity. In order to solve the problem of fixed reporting period of CQI, this paper presents an adaptive CQI adjustment algorithm and scheme for AMC systems in high-speed mobile environment, which evaluates the current channel variation by counting the SNR difference between adjacent symbols in the frame. The evaluation results are used to predict the variation of signal-to-noise ratio in the future. Then, based on the quantitative particle size of CQI, the adaptive adjustment of CQI feedback cycle is calculated, so that the feedback load and throughput of CQI can achieve relatively good performance. Finally, the feasibility and effectiveness of the proposed scheme are verified by computer simulation. Finally, the influence of frequency synchronization algorithm in high speed mobile environment is analyzed. In view of the existence of Doppler frequency offset and crystal oscillator frequency offset simultaneously, an orthogonal corner domain subspace algorithm is used to project the received signal to each subspace, and the equivalent Doppler frequency offset in each subspace is estimated. The mixed frequency offset of Doppler frequency offset and crystal oscillator frequency offset is obtained, and the received signals in each subspace are compensated by the estimated mixed frequency offset to achieve the effect of frequency synchronization. The simulation results show that the error rate performance can be obtained without autoregressive ARF filter, which is due to the fast time-varying Doppler frequency offset, which can not improve the estimation accuracy and increase the estimation noise. In addition, the algorithm can effectively reduce the number of error bits in most sampling locations, only in the case of fast angle of arrival, especially in some special scenarios such as arrival area (AAA) and handoff region.
【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(lèi)號(hào)】：TN92

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