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Non-Orthogonal Pilot Allocation Method for Decellularized Massive MIMO Systems

A pilot allocation and large-scale technology, applied in the field of communication, can solve problems such as lack of effect, pilot pollution, and inability to guarantee the orthogonality of pilot sequences, so as to achieve the effect of improving throughput and reducing pilot pollution

Active Publication Date: 2020-04-21
BEIJING JIAOTONG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] Since the number of orthogonal pilot sequences used for channel estimation is limited, it is impossible to guarantee that the pilot sequences assigned to all users are mutually orthogonal, resulting in the obtained channel estimation being interfered with by using the same pilot user channel, that is, "Pilot Pollution"
Studies have shown that when the number of antennas on the base station tends to infinity, the influence of uncorrelated noise and fast fading on channel estimation will disappear, causing pilot pollution to become the main factor affecting communication quality in massive MIMO systems
[0004] In the prior art, the solution for pilot pollution is to randomly allocate pilot sequences first, and then use a greedy algorithm according to the actual Signal to Interference plus Noise Ratio (SINR) of the user, and compare the SINR Small users redistribute pilots to improve system throughput, but the effect of this method is still lacking. Therefore, a method that considers the possible pilot pollution and interference of all users is needed. From an overall perspective, for all Method for uniformly allocating pilot sequences to users

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  • Non-Orthogonal Pilot Allocation Method for Decellularized Massive MIMO Systems
  • Non-Orthogonal Pilot Allocation Method for Decellularized Massive MIMO Systems
  • Non-Orthogonal Pilot Allocation Method for Decellularized Massive MIMO Systems

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Embodiment 1

[0033] figure 1 It is a schematic diagram of a non-orthogonal pilot allocation method for a decellularized massive MIMO system, figure 2 It is a flow chart of a non-orthogonal pilot allocation method for a cellular massive MIMO system, referring to figure 1 and figure 2 , the method includes:

[0034] S1 obtains the channel large-scale fading coefficients from the user to each base station within a certain range, and calculates the coefficient ratio of the channel large-scale fading coefficient of the user to each base station to the sum of the channel large-scale fading coefficients of the corresponding user to all base stations.

[0035] Schematically, in the range of 1km × 1km, M base stations and K users are randomly distributed, and the minimum mean square error algorithm is used to estimate the channel of the pilot sequence transmitted by the user, and the large-scale channel from the user to each base station is obtained. fading coefficient. Number the users seque...

Embodiment 2

[0052] This embodiment 2 is to adopt the method of the present invention to carry out non-orthogonal pilot frequency allocation for decellularization massive MIMO system, specifically comprises the following steps:

[0053] Scenario parameter setting: There is a square area of ​​1km×1km, 100 base stations, 40 users, and 20 pilot sequences with a length of 20 symbols are multiplexed among the users. Here we use the commonly used large-scale fading model Hata-COST231, and the attenuation factor of shadow fading is 8dB. According to the distance between the user and the base station, the path loss is divided into three stages:

[0054]

[0055] Among them, d mk is the distance between the kth user and the mth base station, d 0 is the reference distance of the first segment, d 0 10m, d 1 is the reference distance of the second segment, d 1 is 50m,

[0056] L=46.3+33.9 log 10 (f)-13.82 log 10 (h AP )-(1.1 log 10 (f)-0.7)h UE +(1.56log 10 (f)-0.8) Among them, f is the ...

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Abstract

The invention provides a non-orthogonal pilot frequency distribution method for a decellular large-scale MIMO system. The method comprises the following steps: acquiring a channel large-scale fading coefficient from a user to each base station within a certain range, and calculating a coefficient ratio of the channel large-scale fading coefficient of the user to each base station to the sum of thechannel large-scale fading coefficients of the corresponding user to all base stations; according to the coefficient proportion, selecting that the sum of the minimum number of coefficient proportions of each user is greater than a certain scale factor, and taking the base station corresponding to the selected coefficient proportion as a base station group of the user; obtaining an undirected graph according to the base station group of each user, dyeing the undirected graph by adopting a graph theory vertex dyeing theory, and updating a dyeing result according to a judgment mechanism; and distributing the non-orthogonal pilot frequency of the system according to the obtained dyeing result. The method provided by the invention can effectively reduce the influence of the pilot pollution effect, improve the user capacity of the system, and improve the robustness of the pilot distribution result.

Description

technical field [0001] The invention relates to the field of communication technology, in particular to a method for allocating non-orthogonal pilots used in a decellularized massive MIMO system. Background technique [0002] The cell-free (cell-free) massive multiple-input multiple-output (multiple-input multiple-output MIMO) system can avoid the inter-cell interference problem that occurs in the massive MIMO communication system between cells, and realizes the optimization of channel capacity and spectrum efficiency. It has been greatly improved, which has attracted extensive attention in the field of wireless communication. In a cell-free massive MIMO system, a large number of distributed base stations provide uniform services to a small number of users at the same time, using Time Division Duplexing (TDD) operation. In the TDD communication mechanism, both uplink training and data transmission are completed within the same coherent time. Therefore, by using the recipro...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04L5/00H04B7/0413H04W24/02H04W24/08
CPCH04B7/0413H04L5/0048H04W24/02H04W24/08
Inventor 章嘉懿刘恒
Owner BEIJING JIAOTONG UNIV