Channel estimating method in MIMO-OFDM system

Abstract

Present invention discloses semi-blind channel estimation method in MIMO -OFDM system. It contains replacing original OFDM circulate prefixion to training sign to estimate channel. Transmitted-data is divided into training sign and data transmission OFDM sign, wherein training sign constituting fine self-correlation and poor cross-correlation sequence for substituting circulate prefixion, resisting ISI and ICI and establishing channel estimated initial parameter, data transmission OFDM sign composed of data sign channel estimate algorithm adopting Wiener's algorithm. Said invention has higher frequency spectrum efficiency and data-signalling rate and lower operating complexity.

Description

Technical field: [0001] The invention belongs to the field of wireless broadband communication, and particularly relates to channel estimation in MIMO-OFDM system. Background technique: [0002] There are many kinds of digital wireless communication systems in the world at present, mainly including GSM system, IS-136 TDMA system and IS-95 CDMA system. However, for high-speed data services, the symbol width of the information flow is relatively short, and the wireless channel has delay extension, so there will be serious inter-symbol interference (ISI) between symbols, resulting in both single-carrier TDMA systems and narrowband CDMA systems. There are big flaws. In this case, the Orthogonal Frequency Division Multiplexing (OFDM) system, due to its effective resistance to ISI, maximizes the use of spectrum resources, facilitates the implementation of IDFT and DFT, supports asymmetric high-speed data transmission, and dynamically allocates bits and sub-channels. Combined wit...

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Problems solved by technology

In the non-blind channel estimation method, the channel estimation scheme of optimal training sequence or decision feedback (see literature [Y.(G.) Li, Simplified channel estimation for OFDM systems with multiple transmit antennas, IEEE Trans, 2002, 1(1) : 67-75]) it requires a large amount of calculations and requires strong receiver processing capabilities. In fast fading applications, frequent transmission of training sequences is required, resulting in a large loss of spectral efficiency; channel estimation methods based on pilot subcarriers are widely used, but The loss of spectrum resources caused by pilot insertion is inevitable (see [K.Lee and D.B.Williamos, Pilot-Symbol-Assisted channel estimation for Space-Time Coded OFDM systems, EURASIP Journal on Applied Signal Processing 2002(5): 507 -516])

In contrast, blind channel estimation avoids the use of pilot training sequences and improves the information transmission rate, but the computational complexity of blind channel estimation algorithms based on methods such as subspace is very large, which is not conducive to real-time estimation, and there will be phase ambiguity, etc. problem, the practical value is not high (see [Jx Du, Ye(G)Li, MIMO-OFDM channel estimation based on subspace tracking, 2003(2): 1084-1088] and [H.Blcskei, et al., Blind channel identification and equalization in OFDM-Based multiantenna systems, IEEE Trans On Signal Processing, 2002, 1(50): 96-109]); the method of channel estimation using OFDM cyclic prefix is ​​a novel blind channel estimation method, and its spectrum utilization High, but in the case of low signal-to-noise ratio, the calculation convergence speed is slow (see literature [Xw Wang, K.J.Ray Liu, Performance analysis for adaptive channel estimation exploiting cyclic prefix in multicarrier modulation systems, IEEEtrans, 2003, 51(1): 94-105])

The semi-blind channel estimation method is between the non-blind and blind methods, that is, sending part of the training sequence, which combines the advantages of the above two estimation methods, but its performance is still inferior to non-blind channel estimation and tracking for fast fading time-varying channels. blind channel estimation method

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