【摘要】：在LTE上行鏈路中,由于疊加在一起的不同用戶的信號(hào)定時(shí)偏移和頻率偏移各不相同,因此上行同步需要估計(jì)多個(gè)參數(shù),如何同時(shí)對(duì)不同用戶進(jìn)行補(bǔ)償是一個(gè)難點(diǎn)。論文首先對(duì)LTE系統(tǒng)重點(diǎn)介紹了與本論文工作相關(guān)的知識(shí),包括系統(tǒng)幀結(jié)構(gòu)、上行調(diào)制技術(shù)、上行通信信道、基帶信號(hào)處理流程,此外還介紹了LTE系統(tǒng)上行同步所用到的關(guān)鍵序列以及上行多用戶系統(tǒng)特點(diǎn)與子載波資源分配方式。其次,基于已實(shí)現(xiàn)的LTE演示系統(tǒng),針對(duì)其每個(gè)上行子幀只能傳輸一個(gè)終端數(shù)據(jù)的問題,詳細(xì)討論了基站側(cè)多用戶并發(fā)功能的改進(jìn)設(shè)計(jì),從而支持在單個(gè)上行子幀內(nèi)同時(shí)傳輸多個(gè)終端的數(shù)據(jù)。具體包括:第一,將上行調(diào)度由時(shí)分復(fù)用的輪詢調(diào)度修改成了頻分復(fù)用的子載波塊狀分配;第二,用“多路并行處理+資源解映射”而非窄帶濾波器組的方式來分離上行多用戶的數(shù)據(jù);第三,設(shè)計(jì)了適合上行多用戶系統(tǒng)的上行時(shí)頻同步方案。在時(shí)頻同步方案中,利用DMRS信號(hào)進(jìn)行上行時(shí)間提前量(TA)的估計(jì),并控制終端進(jìn)行樣點(diǎn)調(diào)整以維持上行定時(shí)同步;分別利用SRS信號(hào)和DMRS信號(hào)進(jìn)行粗頻偏估計(jì)和殘余頻偏估計(jì),并相應(yīng)在FFT前進(jìn)行頻偏補(bǔ)償,以完成上行頻率同步。在多徑仿真信道下對(duì)所實(shí)現(xiàn)同步模塊的仿真結(jié)果表明,五個(gè)用戶同時(shí)通信,定時(shí)估計(jì)算法在高斯信道下性能優(yōu)于多徑信道;聯(lián)合頻偏估計(jì)算法在高斯信道下性能與多徑信道類似。然后,本文基于GNU Radio/USRP軟硬件平臺(tái)和已有LTE演示系統(tǒng)實(shí)現(xiàn)了上述設(shè)計(jì)。第一,實(shí)現(xiàn)了上行多用戶的資源調(diào)度,可在同一子幀對(duì)多個(gè)終端的請(qǐng)求進(jìn)行調(diào)度,提高了效率和頻帶利用率。第二,實(shí)現(xiàn)了所設(shè)計(jì)的上行同步方案,包括頻偏補(bǔ)償和UE定時(shí)調(diào)整的實(shí)現(xiàn);此外,在用SRS和DMRS進(jìn)行偏差估計(jì)時(shí)分別引入了SRS互相關(guān)算法和CRC校驗(yàn),從而提高了偏差估計(jì)值的準(zhǔn)確度和有效性。第三,基于GNURadio的平臺(tái)特點(diǎn)和信號(hào)驅(qū)動(dòng)的流圖機(jī)制,搭建出完整的可支持上行多用戶時(shí)頻同步與信號(hào)處理的LTE無線通信實(shí)際系統(tǒng)。最后,在室內(nèi)無線環(huán)境下對(duì)該系統(tǒng)進(jìn)行了實(shí)測(cè)。結(jié)果表明,基站能夠同時(shí)調(diào)度兩個(gè)終端的請(qǐng)求,也能夠同時(shí)接收兩個(gè)終端所發(fā)送的視頻流;在3MHz帶寬無線環(huán)境中,使用QPSK調(diào)制方式,上行編碼碼率為0.5條件下,平均上行誤包率為1.3×10-5,播放視頻的主觀質(zhì)量清晰流暢;兩終端可以達(dá)到227.6KBytes/s的總上行速率,與理論分析基本吻合。
[Abstract]:In the LTE uplink, because the signal timing offset and frequency offset of different users superimposed together are different, uplink synchronization needs to estimate multiple parameters, so how to compensate different users at the same time is a difficulty. Firstly, the thesis introduces the knowledge of LTE system, including system frame structure, uplink modulation technology, uplink communication channel, baseband signal processing flow. In addition, the key sequences used in uplink synchronization of LTE system and the characteristics of uplink multiuser system and subcarrier resource allocation are also introduced. Secondly, based on the implemented LTE demonstration system, aiming at the problem that only one terminal data can be transmitted per uplink sub-frame, this paper discusses in detail the improved design of multi-user concurrent function on the base station side. Thus, the data of multiple terminals can be transmitted simultaneously in a single uplink subframe. Specifically including: first, the uplink scheduling is modified from the polling scheduling of time division multiplexing to subcarrier block allocation of frequency division multiplexing; second, The data of uplink multiuser is separated by "multi-channel parallel processing resource demapping" instead of narrowband filter bank. Thirdly, an uplink time-frequency synchronization scheme suitable for uplink multiuser system is designed. In the time-frequency synchronization scheme, DMRS signal is used to estimate the uplink time advance (TA), and the terminal is controlled to adjust the sample points to maintain the uplink timing synchronization, and the SRS and DMRS signals are used to estimate the coarse frequency offset and the residual frequency offset, respectively. Frequency offset compensation is carried out before FFT to achieve uplink frequency synchronization. The simulation results of the synchronization module in multipath simulation channel show that the performance of timing estimation algorithm in Gao Si channel is better than that in multipath channel. The performance of joint frequency offset estimation algorithm in Gao Si channel is similar to that in multipath channel. Then, based on GNU Radio / USRP software and hardware platform and LTE demonstration system, the above design is implemented. First, the uplink multi-user resource scheduling is realized, which can schedule the requests of multiple terminals in the same sub-frame, which improves the efficiency and frequency band efficiency. Secondly, the proposed uplink synchronization scheme is implemented, including frequency offset compensation and UE timing adjustment, in addition, SRS cross-correlation algorithm and CRC check are introduced in the estimation of deviation by SRS and DMRS, respectively. Therefore, the accuracy and validity of the deviation estimate are improved. Thirdly, based on the platform characteristics of GNURadio and the signal-driven flow graph mechanism, a complete LTE wireless communication system which can support uplink multi-user time-frequency synchronization and signal processing is built. Finally, the system is measured in indoor wireless environment. The results show that the base station can simultaneously schedule the requests of the two terminals and receive the video streams transmitted by the two terminals at the same time. In the 3MHz bandwidth wireless environment, using QPSK modulation mode, the uplink coding rate is 0.5. The average uplink packet error rate is 1.3 脳 10 ~ (-5), the subjective quality of video playing is clear and smooth, and the two terminals can achieve the total uplink rate of 227.6 KBytes / s, which is basically consistent with the theoretical analysis.
【學(xué)位授予單位】：西安電子科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類號(hào)】：TN929.5

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