Pre-coding method and system in MIMO system with multiple users

Abstract

The embodiment of the invention discloses a precoding method which comprises the steps that: a first codebook and a second codebook are arranged at a base station and a user terminal, the second codebook is a set of unitary matrices generated by vectors in the first codebook and by making use of channel matrices, vectors that ensure that the user terminal obtains the maximum coding gain are respectively selected for every user terminal in the first codebook and corresponding CQI values are calculated; the base station determines the user terminal to be precoded and chooses a unitary matrix from the second codebook according to the vectors in the first codebook and corresponding CQI values corresponding to the user terminal to be precoded or chooses a unitary matrix from the second codebook and determines the user terminal to be precoded according to vectors in the first codebook and the corresponding CQI values corresponding to every user terminal; the unitary matrices or submatrices thereof are used as precoding matrices to carry out precoding towards the user terminal to be precoded. The embodiment of the invention also discloses a precoding system, and failure of matching amonga plurality of user terminals can be avoided by the method and the system of the invention.

Description

technical field [0001] The invention relates to the communication field, in particular to a precoding method and system in a multi-user terminal MIMO system. Background technique [0002] With the deepening of multi-antenna technology research, Multiple-Input Multiple-Output (MIMO) technology has been extended from a point-to-point single-user terminal system to a point-to-multipoint multi-user terminal MIMO system, that is, some antennas are To distinguish different user terminals, used to transmit different data, to obtain spatial multiplexing gain, to obtain a higher transmission rate, thereby expanding the channel capacity area of ​​​​multi-user terminals; and for some antennas with the same code, used to transmit the same data to obtain diversity gain and effectively resist fading, thereby improving bit error performance. [0003] In a multi-user terminal MIMO system, in order to avoid the multi-user terminal Co-Channel Interference (CCI) introduced when multiple user ...

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Problems solved by technology

[0006] This FFT codebook-based precoding method can achieve better performance in the case of full feedback. In full feedback, each user terminal needs to feed back multiple CQI values. At this time, the amount of feedback is large. In the case of limited capacity , it is not easy to apply in practice

In the case of non-full feedback, for example, in the case of low feedback amount, if each user terminal can only feed back a small amount of CQI values, the base station cannot select the most suitable precoding vector to precode the transmitting antenna, so the precoding performance poor

[0007] In addition, when precoding once, the selected precoding vectors should belong to the same precoding matrix, and for the precoding method based on the FFT codebook, the user terminal selects the precoding vector and sends it to the base station Feedback, the precoding vector is a certain vector in a certain precoding matrix in the first codebook, and in the case of non-full feedback, the precoding vectors selected by multiple user terminals often do not belong to the same precoding matrix, so When the base station schedules user terminals, these user terminals cannot be precoded at the same time, or it is called pairing failure

[0008] It can be seen that the current precoding method in the multi-user terminal MIMO system has the problem of pairing failure between multiple user terminals

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