發(fā)布時間：2018-06-13 01:34

  本文選題：F-OFDM + OFDM　； 參考：《西南交通大學(xué)》2017年碩士論文

【摘要】：隨著IMT-2020(5G)推進組對未來通信需求的明確,多種應(yīng)用場景和業(yè)務(wù)需求給物理層波形的設(shè)計帶來了新的挑戰(zhàn)。2015年,華為在正交頻分復(fù)用(OFDM)技術(shù)的基礎(chǔ)上提出了基于子帶濾波的正交頻分復(fù)用(Filtered-OFDM,F-OFDM)技術(shù),其通過子帶濾波降低頻譜帶外泄露,各子帶根據(jù)具體的業(yè)務(wù)需求靈活配置波形參數(shù),從而實現(xiàn)了靈活自適應(yīng)的空口技術(shù)。F-OFDM作為一種新興的多載波技術(shù),對頻偏造成的載波間干擾(Inter-Carrier Interference,ICI)較為敏感。因此,有必要在當前F-OFDM研究現(xiàn)狀的基礎(chǔ)上,利用OFDM頻偏估計算法來實現(xiàn)F-OFDM系統(tǒng)的頻偏估計,以降低頻偏對系統(tǒng)性能的影響。首先,本文系統(tǒng)地分析了無線信道的小尺度衰落特性以及頻偏對OFDM系統(tǒng)的影響,并深入研究了現(xiàn)有的OFDM頻偏估計算法,從理論推導(dǎo)和MATLAB仿真兩個方面對不同算法的估計性能進行了驗證分析。其次,根據(jù)不同子帶的F-OFDM符號能夠在時域共存而在頻域分離,對子帶資源分配和子載波映射進行了研究,并通過MATLAB仿真比較了不同子載波間隔和不同帶寬對子帶性能的影響,結(jié)果表明子載波間隔越大,多普勒頻移對子帶性能的影響越小。另外,驗證了濾波操作能夠有效地降低子帶頻譜帶外泄露,從而使不同子帶設(shè)置極低的保護間隔就能很好的抑制相鄰子帶間的干擾。最后,結(jié)合OFDM頻偏估計算法與F-OFDM的系統(tǒng)特性,分析比較了 CP相關(guān)性算法、改進的CP算法、Moose算法和Classen算法在不同子帶的估計精度。通過仿真分析可得:當子帶的子載波間隔較大時,多普勒頻移對子帶性能的影響較小,且每個F-OFDM符號中插入的CP采樣點較多,因此,子載波間隔較大的子帶適合利用基于CP的頻偏估計算法。當子帶的子載波間隔較小時,多普勒頻移對子帶性能影響較大,并且子帶的符號長度較長以及插入的導(dǎo)頻序列較多,因此,子載波間隔較小的子帶適合利用估計精度較高的數(shù)據(jù)輔助頻偏估計算法。此外,在系統(tǒng)帶寬與采樣率保持一致的前提下,仿真比較了雙子帶F-OFDM系統(tǒng)與OFDM系統(tǒng)利用同一算法進行頻偏補償后的誤碼率。由于子帶能夠靈活設(shè)置波形參數(shù)以及頻偏算法無法徹底消除頻偏引起的ICI,使得F-OFDM系統(tǒng)的誤碼率要低于子載波間隔較小的OFDM系統(tǒng)的誤碼率,高于子載波間隔較大的OFDM系統(tǒng)的誤碼率,體現(xiàn)了 F-OFDM系統(tǒng)通過靈活配置波形參數(shù)能夠有效的降低無線信道對系統(tǒng)性能的影響。
[Abstract]:With the IMT-2020 5G) propulsion team defining future communications requirements, multiple application scenarios and business requirements pose new challenges to the design of physical layer waveforms. Based on orthogonal Frequency Division Multiplexing (OFDM) technology, Huawei proposes a sub-band filter based orthogonal Frequency Division Multiplexing (OFDM) technique, which can reduce the leakage of spectrum out of band by subband filter, and configure waveform parameters flexibly according to specific business requirements. As a new multi-carrier technology, F-OFDM is sensitive to Inter-Carrier interference (ICI) caused by frequency offset. Therefore, it is necessary to use OFDM frequency offset estimation algorithm to realize the frequency offset estimation of F-OFDM system on the basis of the current research status of F-OFDM, so as to reduce the influence of frequency offset on the performance of F-OFDM system. Firstly, the small scale fading characteristics of wireless channel and the influence of frequency offset on OFDM system are systematically analyzed, and the existing OFDM frequency offset estimation algorithms are deeply studied. The estimation performance of different algorithms is verified and analyzed in terms of theoretical derivation and MATLAB simulation. Secondly, according to the F-OFDM symbols of different subbands can coexist in time domain and separate in frequency domain, the sub-band resource allocation and sub-carrier mapping are studied, and the effects of different sub-carrier spacing and different bandwidth on sub-band performance are compared by MATLAB simulation. The results show that the larger the subcarrier spacing, the smaller the influence of Doppler shift on subband performance. In addition, it is proved that the filtering operation can effectively reduce the out-of-band leakage of the sub-band spectrum, so that the interference between adjacent sub-bands can be suppressed very well by setting very low protection interval of different sub-bands. Finally, combining the characteristics of OFDM frequency offset estimation algorithm and F-OFDM system, the estimation accuracy of CP correlation algorithm, improved CP algorithm moose algorithm and Classen algorithm in different sub-bands are analyzed and compared. The simulation results show that the Doppler frequency shift has little effect on the performance of the sub-band when the sub-carrier spacing of the sub-band is large, and there are more CP sampling points inserted in each F-OFDM symbol. The frequency offset estimation algorithm based on CP is suitable for subbands with large subcarrier spacing. When the subcarrier spacing of the subband is small, the Doppler frequency shift has a great influence on the performance of the subband, and the symbol length of the sub-band is longer and the pilot sequence is more inserted. The subbands with small subcarrier spacing are suitable to use the data-aided frequency offset estimation algorithm with higher estimation accuracy. In addition, on the premise that the system bandwidth is consistent with the sampling rate, the bit error rate (BER) of the dual-subband F-OFDM system is compared with that of the OFDM system using the same frequency offset compensation algorithm. Because the subband can set the waveform parameters flexibly and the frequency offset algorithm can not completely eliminate the ICI caused by the frequency offset, the bit error rate of the F-OFDM system is lower than that of the OFDM system with small sub-carrier spacing. The BER of OFDM system is higher than that of OFDM system with large sub-carrier spacing, which shows that F-OFDM system can effectively reduce the influence of wireless channel on system performance by configuring waveform parameters flexibly.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN929.53

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本文編號：2012037