Method for pre-correcting frequency offset of radio frequency in MIMO (Multiple Input Multiple Output) wireless communication system

Abstract

The invention discloses a method for pre-correcting frequency offset of radio frequency in an MIMO (Multiple Input Multiple Output) wireless communication system. A digital PLL (Phase-Locked Loop) is configured in each remote radio frequency unit, and each digital PLL calculates the frequency offset value between an output signal of a reference crystal oscillator of the present remote radio frequency unit and a reference source and generates a compensation signal, thereby pre-correcting the frequency offset of the radio frequency. The invention has the beneficial effects of solving the problem that the frequency offsets of all RRHs (Remote Radio Heads) are different because a same-source radio frequency local oscillator reference source can not be adopted among multiple RRHs due to the space separation, being capable of guaranteeing the consistency of the frequency offset of radio frequencies of multiple transmission paths of the MIMO system, simplifying the complexity of system reception frequency offset estimation and correction realization, improving the accuracy of frequency offset estimation and realization, and improving the transmission performance of the MIMO system.

Description

technical field [0001] The invention relates to the field of radio communication, in particular to a method for pre-correcting radio frequency offset in a multi-transmit and multi-receive wireless communication system. Background technique [0002] Multiple Transmit Multiple Receive Antenna (hereinafter referred to as MIMO) technology is a major breakthrough in antenna technology in the field of wireless communication, because theoretically it can double the system capacity and spectrum efficiency without increasing time and frequency resources. In order to improve transmission capacity or improve transmission reliability, MIMO has two forms, namely space diversity and space multiplexing. Space multiplexing technology uses the space multiplexing gain provided by MIMO channel to greatly improve channel capacity; space diversity uses MIMO channel The space diversity gain provided can improve channel reliability and reduce channel bit error rate. However, in a system deployed ...

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Problems solved by technology

[0005] The frequency synthesizer in the transmitter and receiver of each RRH can use a separate or unified reference crystal oscillator as a reference source for frequency synthesis, and generate the local oscillator signal required for frequency conversion through frequency synthesis, even if a unified reference crystal oscillator is used The reference crystal oscillator also cannot guarantee the frequency synchronization of the frequency synthesizer output signal between multiple RRHs

The RF reference oscillator of the RRH generally uses a high-stability crystal oscillator, and its receiving and transmitting frequency synthesizers cannot be like the CPRI module, which can unify the frequency synthesizers of multiple RRHs to a certain reference source of the indoor unit. A prominent problem of the MIMO system deployed by RRH is the RF frequency offset between RRHs, which will bring great inconvenience to the received signal processing of the MIMO system

[0006] In the signal processing process of the MIMO system, in order to ensure a good reception effect, frequency offset correction is required to eliminate the frequency difference between the transmitting and receiving frequency synthesizers. In the single-transmit and single-receive system, frequency offset correction can be solved very well. And the technology is quite mature, but there are frequency offsets between multiple transmitters and multiple receivers in the received signal in the MIMO system, and these frequency offsets are superimposed and cannot be separated, which greatly improves the MIMO system. Complexity of frequency offset correction processing

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