Channel estimation method for orthogonal frequency division multiplexing (OFDM) system under interference environment

Abstract

The invention discloses a channel estimation method for an orthogonal frequency division multiplexing (OFDM) system under an interference environment. A column singular matrix is multiplied by a corresponding orthogonal projection matrix to obtain a zero matrix so that the vector obtained in the step (5) is equivalent to T=QIp, wherein the element Ip (k) in the vector Ip is a result of dividing an interference signal and noise by a local pilot signal. Because the orthogonal projection matrix is a linear matrix, the statistical property of each element T (k) of the vector T is the same as that of the element Ip (k), the variance estimation value obtained in the step (5) is the sum of the interference signal variance and the noise variance, and optimal estimation of channel time domain impulse response is obtained by using the step (7). The method has low calculation complexity, and the estimated performance of the method is approximate to the ideal channel estimated performance in the absence of interference signals; and meanwhile, aiming at block pilot patterns and uniformly-spaced comb pilot patterns, the method is insensitive to the power of the interference signal, only needs one OFDM symbol, and has good instantaneity.

Description

technical field [0001] The invention belongs to the technical field of mobile communication, and in particular relates to a channel estimation method for an Orthogonal Frequency Division Multiplexing (OFDM, Orthogonal Frequency Division Multiplexing) system. Background technique [0002] Orthogonal frequency division multiplexing is a special multi-carrier modulation method. It divides a broadband channel into multiple orthogonal narrowband flat fading sub-channels, and converts high-speed data signals into parallel low-speed sub-data streams for transmission on each sub-channel, which is beneficial to overcome the frequency selective fading of wireless channels. In order to obtain the best transmission performance, channel estimation needs to be performed at the receiving end to obtain channel state information. [0003] The channel estimation in the present invention is based on a pilot-aided time-domain channel estimation method, which is suitable for placing comb-shaped...

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Problems solved by technology

[0008] Among them, method (i) can converge well under reasonable initial estimation conditions, and the estimation performance is close to the ideal channel estimation without interference signal, but this method needs to be based on the variance of interference signal and noise variance The current estimation sequence updates the time-domain impulse response estimate of the WLS channel. The update process involves matrix multiplication and inversion operations, which has high complexity. At the same time, this method is sensitive to the performance of the initial channel estimation

Method (ii) has low complexity. In an OFDM system based on a specific block pilot pattern, that is, in this pilot pattern, two consecutive pilot symbols are required. When the interference power is large, its performance is better. When When the interference power is small, the performance deteriorates because the position of the interference signal cannot be detected well

In an OFDM system based on a comb-shaped pilot pattern, when the number of interfered pilot subcarriers is greater than 1 and the interference is continuous, the performance of this method deteriorates. At the same time, the real-time performance of this method is poor. Before channel estimation, at least receiving Two or more OFDM symbols

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