A method for estimating in-phase/quadrature unbalance in ofdm system and its module

Abstract

The invention discloses an estimation method and module for in-phase / quadrature-phase (IQ) imbalance in an OFDM (Orthogonal Frequency Division Multiplexing) system. The estimation method comprises the following steps: S1, performing frequency offset compensation on received time domain signals; S2, after removing cyclic prefixes, transforming two different pilot symbols adjacent on time to a frequency domain; S3, extracting subcarriers occupied by the pilot symbols according to the system bandwidth; S4, for the two pilot symbols, obtaining received signals of two pilot signals on each subcarrier; and S5, removing coupling of IQ imbalance parameters and channels, and solving an IQ imbalance estimation value. The method and the module are wide in application and low in requirement for the processing time sequence of a receiver, conform to the demands of most practical application scenes, and are simple in algorithm and small in calculation quantity.

Description

technical field [0001] The invention relates to a method and module for estimating in-phase / quadrature-phase (In-phase / Quadrature-phase, referred to as IQ) imbalance in an OFDM (orthogonal frequency division multiplexing) system, which belongs to wireless communication technology field. Background technique [0002] In common OFDM communication systems (such as 802.11a / g / n / ac series and LTE, etc.), in order to improve spectrum utilization efficiency, high-order modulation or MIMO technology is generally used. These complex transmission schemes require the receiver to be able to achieve a relatively high signal-to-noise ratio (SNR). However, the transceiver is limited by the production cost and may need to use relatively low-priced devices. Its non-ideal IQ imbalance characteristics will lead to a decrease in the signal-to-noise ratio at the receiving end and seriously affect the receiving performance. In order to improve the receiving performance, it is necessary to accura...

AI Technical Summary

Problems solved by technology

This method has the following shortcomings: the demodulation of the data symbols needs to be completed first, and then the IQ imbalance can be estimated, so it has requirements for the timing of the specific implementation, and the complexity is high; the channel estimation on the data symbols is generally performed by the channel on the pilot The interpolation of the channel estimation, itself contains IQ imbalance and interpolation error, resulting in the accuracy of IQ imbalance estimation is not as good as the direct use of symmetric pilot signals; if the data symbol demodulation error occurs, it will directly lead to errors in IQ imbalance estimation

This method has the following shortcomings: different down-mixing methods need to be used in the initial stage of receiving OFDM signals, and the additional frequency offset added in the down-mixing depends on the specific pilot design, and the implementation complexity is high; assuming IQ imbalance It is a static value, which cannot realize real-time estimation of IQ imbalance; in the actual environment, IQ imbalance is also affected by time-varying factors such as temperature and voltage, so the practicability of this method is questionable

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