Pilot distribution method for mitigating pilot pollution based on massive MIMO system

Abstract

The invention relates to a pilot distribution method for mitigating pilot pollution based on a massive MIMO system and belongs to the technical field of mobile communication. According to the method, users with good channel environments are distinguished by utilization of anti-pilot pollution factors; the users satisfying conditions and the users of adjacent cells multiplex the same pilot; completely orthogonal pilots are independently distributed to edge users with poor channel environments; and the pilot pollution is avoided. Moreover, the maximum value and minimum value of a threshold value are derived; a suitable threshold value can be obtained between the maximum value and minimum value according to the lengths of the pilots and the practical experience of the users in the practical environments; harms resulting from the pilot pollution are reduced; and the system efficiency is enabled to be optimized.

Description

technical field [0001] The invention belongs to the technical field of mobile communication, and relates to a pilot allocation method based on reducing pilot pollution in a massive MIMO system. Background technique [0002] MIMO technology is one of the key technologies of 4G. In 2010, based on this, Marzetta of Bell Labs proposed that a large number of antennas be installed on the base station side, thus forming a massive MIMO (Massive MIMO) wireless communication system. Massive MIMO has attracted widespread attention for its high energy efficiency and frequency efficiency, making it a key technology for future "5G" communications. The achievable rate in a MIMO system largely depends on the state information of the channel. In massive MIMO, the reciprocity of the TDD system is usually used to obtain the state information of the channel. Because terminal users are often constantly moving in mobile communication systems, the length of channel coherence time is limited. Due ...

AI Technical Summary

Problems solved by technology

The length of channel coherence time is limited, which limits the length of mutually orthogonal pilot sequences, and cannot guarantee that the pilot sequences of terminals in adjacent cells are all orthogonal, so pilots need to be multiplexed

However, the target base station cannot identify the pilot signals multiplexed by the terminal users in this cell and other interfering cells, which affects the estimation of the uplink channel by the target base station, resulting in the destruction of the downlink precoding matrix information, which seriously affects the spectrum efficiency of the system, resulting in "Pilot Pollution"

The pilot pollution problem seriously affects the efficiency of the massive MIMO system and becomes the bottleneck restricting the massive MIMO system

[0003] In response to the above problems, a channel estimation scheme based on eigenvalue decomposition was proposed: this scheme mainly uses the orthogonality between the covariance matrix of the signal received at the base station and the channel vector to estimate the channel state information in the system communication process, so It can effectively improve the accuracy of channel estimation and has a certain resistance to pilot pollution; however, this algorithm takes into account that in an ideal situation, the number of antennas of the base station in the system and the amount of received data tend to be infinite, if If the conditions are not met, the estimated effect will be greatly affected

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