多徑信道下OFDM系統(tǒng)中的兩種線性載波間干擾抑制技術(shù)
Two linear intercarrier interference cancellation techniques in ofdm systems over multipath channels
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摘要: 載波間干擾(ICI)是影響正交頻分復(fù)用(OFDM)系統(tǒng)性能的重要因素。該文研究了不同延遲線長(zhǎng)度L下的頻域RAKE(F-RAKE)和頻域均衡(F-FIR)兩種線性ICI抑制技術(shù)。假設(shè)接收端已知信道信息,F-FIR采用最小均方誤差(MMSE)準(zhǔn)則。結(jié)果表明L=3時(shí),F-RAKE比標(biāo)準(zhǔn)接收機(jī)的載干比(CIR)高2～5dB,而F-FIR則高出2～7dB;隨著L的增加,兩種接收機(jī)所能獲得的CIR增益逐漸降低。從計(jì)算復(fù)雜度來(lái)看,F-FIR的計(jì)算量是F-PAKE的L倍,工程中可以通過(guò)選取不同延遲線長(zhǎng)度和接收機(jī)結(jié)構(gòu)來(lái)達(dá)到計(jì)算復(fù)雜度和性能的折衷。
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關(guān)鍵詞:
- 頻域RAKE; 頻域均衡; OFDM; 載波間干擾
Abstract: InterCarrier Interference (ICI) is an important, factor degrading the performance of Orthogonal Frequency Division Multiplexing (OFDM) systems. Two linear ICI cancellation techniques, Frequency RAKE (F-RAKE) and frequency equalization (F-FIR), with different length of delay-line, L, are studied in this paper. Assuming that the channel information is known in the receiver and MMSE criterion is adopted for F-FIR, results show that F-RAKE has about 2~5dB Carrier-Interference-Ratio (CIR) achievement than standard receiver in case of L=3. Meanwhile, F-FIR has about 2~7 dB CIR achievement. And the CIR performance gains of the two schemes decrease with increment of L. Also, the computational complexity of F-FIR is L times than that of F-RAKE. Thus, the tradeoff between complexity and performance in the engineering can be reached by selecting the length of delay-line and receiver scheme. -
Y. Li, L. J. Cimini, Jr., Bounds on the interchannel interference of OFDM in time-varying impairments, IEEE Trans. on Commun., 2001, 49(3), 401-404.[2]J. Armstrong, Analysis of new and existing methods of reducing intercarrier interference due to carrier frequency offset in OFDM, IEEE Trans. on Commun., 1999, 47(3), 365-369.[3]C. Muschalik, Improving an OFDM reception using an adaptive Nyquist windowing, IEEE Trans.on Consumer Electronics, 1996, 42(3), 259-269.[4]Y. Zhao, S. G. Haggman, Intercarrier interference self-cancellation scheme for OFDM mobile communication systems, IEEE Trans. on Commun. 2001, 49(7), 1185-1191.[5]Y. Zhao, S. G. Haggman, Sensitivity to Doppler shift and carrier frequency error in OFDM systems - The consequences and solutions, in Proc. IEEE Vehicular Technology Conference,Atlanta, USA. 1996, 1564-1568.[6]S. Haykin, Adatpive Filter Theory, 3rd edition, USA, Prentice Hall, 1996, chapter 8. -
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