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CN110943767B - Precoding design method based on channel part reciprocity in FDD large-scale MIMO system - Google Patents

Precoding design method based on channel part reciprocity in FDD large-scale MIMO system Download PDF

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CN110943767B
CN110943767B CN201911087539.4A CN201911087539A CN110943767B CN 110943767 B CN110943767 B CN 110943767B CN 201911087539 A CN201911087539 A CN 201911087539A CN 110943767 B CN110943767 B CN 110943767B
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user
precoding
base station
channel
design method
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王海泉
高丹蓓
陈跃
叶杭
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Hangzhou Dianzi University
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0456—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting

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Abstract

The invention belongs to the technical field of wireless communication, in particular to a precoding design method based on channel part reciprocity in a single-user large-scale MIMO system, which is applied to the single-user large-scale MIMO system under Frequency Division Duplex (FDD), and comprises the following steps: designing a reference frame and selecting a proper reference vector; designing a pilot frequency sequence and processing a received signal; selecting a code word and feeding back an index of the code word; precoding and transmitting information are designed. Compared with the precoding design method based on DFT, the precoding design method based on the channel part reciprocity has better system performance and can realize higher channel utilization rate, and the provided CSI feedback process can greatly reduce system training and feedback overhead so as to improve the system performance. And by optimizing the parameters
Figure DDA0002265889300000011
Figure DDA0002265889300000012
And the value of R can further improve the performance.

Description

Precoding design method based on channel part reciprocity in FDD large-scale MIMO system
Technical Field
The invention belongs to the technical field of wireless communication, and particularly relates to a precoding design method based on channel part reciprocity in an FDD large-scale MIMO system.
Background
In a large-scale MIMO system, a large-scale antenna array of a Base Station (BS) is utilized, the system can obtain extremely high spatial resolution and spatial division multiplexing gain, a plurality of users can be simultaneously served under the condition of not causing serious interference, and the frequency spectrum efficiency and the transmission rate of the system are greatly improved. However, these advantages all depend on the availability of Channel State Information (CSI), and therefore how to accurately acquire CSI in a real system is crucial to the system performance.
For a Frequency Division Duplex (FDD) massive MIMO system, a large amount of time-frequency overhead is required to acquire downlink CSI. In a practical massive MIMO system, since the training amount and the feedback overhead are proportional to the number of BS antennas, it is too much consumed and impractical to adopt the conventional linear channel estimation methods such as Least Square (LS) algorithm and Linear Minimum Mean Square Error (LMMSE) algorithm to acquire CSI. In order to better control system resources, the reciprocity of time delay and angle between uplink channel and downlink channel frequency bands in the FDD system can be used to reduce feedback overhead. Under the condition of acquiring the CSI, the interference can be eliminated by adopting the precoding technology, and the performance of a downlink can be further improved. Therefore, on the basis of channel part reciprocity, the problem of acquiring and feeding back the CSI is researched, and a precoding technology is combined to design a scheme that the problem of accurately acquiring the downlink CSI in the FDD large-scale MIMO system can be solved through a small amount of training and feedback overhead.
Disclosure of Invention
Based on the above disadvantages in the prior art, the present invention provides a precoding design method based on channel part reciprocity in an FDD massive MIMO system, comprising the following steps:
s1, determining the acquired parameter values by knowing a precoding codebook, and designing a reference frame according to the parameter values; selecting a suitable reference vector according to the reference frame;
s2, designing a pilot sequence according to the reference vector, sending the pilot sequence to a user, and processing a received signal of the user by using an MMSE estimation method;
s3, selecting a code word corresponding to the processed parameter in the precoding codebook, and feeding back an index corresponding to the code word to the base station;
s4, the base station constructs a precoding and transmits information to the user using the precoding.
As one preferable scheme of the invention, the massive MIMO system comprises a single-antenna user and a base station, and the base station is provided with MtRoot antenna, LcAnd (4) clustering.
As one of the preferable embodiments of the present invention, step S1 specifically includes:
s1.1, according to the parameters
Figure BDA0002265889280000021
And
Figure BDA0002265889280000022
value of (2) construct a frame of reference
Figure BDA0002265889280000023
The reference vector is formed by dimension MaX 1 of
Figure BDA0002265889280000024
A reference vector qaiComposition, defined as follows:
Figure BDA0002265889280000025
reference frame
Figure BDA0002265889280000026
Wherein
Figure BDA0002265889280000027
S1.2, calculating
Figure BDA0002265889280000028
i＝1,2,…,NrSelecting the reference vector q corresponding to the largest former R value1,q2,…,qRAnd is denoted as Q.
As one of the preferable embodiments of the present invention, step S2 specifically includes:
the channel is established based on the 3GPP TR 36.873V 12.7.0 standard, the time correlation item is not considered, the transmitting antenna field mode and the receiving antenna field mode among the antennas are respectively equal, and the antenna array is a uniform planar array;
s2.1: performing singular value decomposition on Q;
Q＝UDVH
wherein
Figure BDA0002265889280000029
D＝diag(λ1,λ2,…,λR) And λ1≥λ2≥…≥λR；
S2.2: taking singular value vector u corresponding to first K maximum singular values of Q1,u2,…,uKCombined into UKAs a pilot sequence;
s2.3: will UKAnd sending the signal to the user through a downlink channel, wherein the signal received by the user side is as follows:
Figure BDA0002265889280000031
wherein
Figure BDA0002265889280000032
In order to be a downlink channel, the channel is,
Figure BDA0002265889280000033
is noise.
S2.4: processing the received signal by using an MMSE estimation method, and estimating to obtain giIt can be expressed as:
Figure BDA0002265889280000034
and for gK＝[g1 g2 … gK]Normalized to g0。
As one of the preferable embodiments of the present invention, step S3 specifically includes:
precoding codebook
Figure BDA0002265889280000035
To find g in0Code word of
Figure BDA0002265889280000036
Corresponding index
Figure BDA0002265889280000037
And feeding back the index to the base station, the index being defined by:
Figure BDA0002265889280000038
as one of the preferable embodiments of the present invention, step S4 specifically includes:
base station construction precoding
Figure BDA0002265889280000039
And sending information s to the user by using the precoding, wherein the receiving signal of the user is represented as:
Figure BDA00022658892800000310
compared with the prior art, the invention has the beneficial effects that:
compared with the traditional precoding design method, the precoding design method based on the channel part reciprocity does not need estimation, can realize higher channel utilization rate, and can greatly reduce the system training and feedback overhead in the CSI feedback process so as to improve the system performance. And by optimizing the parameters
Figure BDA00022658892800000311
Figure BDA00022658892800000312
And the value of R can further enhance performance.
Drawings
Fig. 1 is a simulation diagram of the number of base station antennas with respect to the channel utilization under different feedback numbers K according to the method of the embodiment of the present invention.
Fig. 2 is a simulation diagram of the feedback number K value with respect to the channel utilization rate under different antenna numbers according to the method of the embodiment of the present invention.
Detailed Description
The technical solution of the present invention will be further explained below.
The precoding design method based on the reciprocity of the channel parts in the embodiment of the invention is improved aiming at the defects of the existing precoding design method. The precoding design method based on the channel part reciprocity is applied to a precoding design method of a single-user large-scale MIMO system under FDD, and provides a CSI feedback process.
The specific application case is as follows:
suppose that there are 1 user, 1 base station and the number of base station antennas is 32, the value of K is 10, and the parameter is used
Figure BDA0002265889280000041
R ═ 64 is an example. The following table shows general parameters of the system, and precoding design is performed according to the system parameters in table 1.
TABLE 1 System parameter selection
Figure BDA0002265889280000042
Figure BDA0002265889280000051
S1, designing a reference frame and selecting a proper reference vector
Assuming that a single-user massive MIMO system includes one single-antenna user, one base station equipped with 32 antennas, 19 clusters are considered. It is assumed that the channel is a channel established based on the 3GPP TR 36.873V 12.7.0(2017-12) standard and that the transmit antenna field pattern and the receive antenna field pattern between the antennas are equal, respectively, regardless of the time-dependent term. Assuming that the precoding codebook is known at both the base station and the user
Figure BDA0002265889280000052
In the case of (2), setting parameters
Figure BDA0002265889280000053
R＝16。
S1.1: according to the obtained parameters
Figure BDA0002265889280000054
And
Figure BDA0002265889280000055
value of (2) construct a frame of reference
Figure BDA0002265889280000056
The reference vector is 16 reference vectors q of dimensions 8 × 1vi32 reference vectors q with a sum dimension of 4 × 1hiComposition, defined as follows:
Figure BDA0002265889280000057
reference frame
Figure BDA0002265889280000058
Wherein N isr＝16×32，Mv＝8，Mh＝4，Bv＝4，Bh＝5。
S1.2: based on the constructed reference frame, 64 suitable reference vectors are selected by calculation
Figure BDA0002265889280000059
i is 1,2, …,512, and the reference vector q corresponding to the first 64 largest values is selected1,q2,...,q64And is denoted as Q.
S2, designing pilot sequence and processing received signal
Assuming that the channel is a channel established based on the 3GPP TR 36.873V 12.7.0(2017-12) standard and that the transmit antenna field pattern and the receive antenna field pattern between the antennas are equal, respectively, regardless of the time correlation terms, the antenna array is a Uniform Planar Array (UPA).
S2.1: performing Singular Value Decomposition (SVD) on Q;
Q＝UDVH
wherein
Figure BDA0002265889280000061
D＝diag(λ1,λ2,…,λ64) And λ1≥λ2≥…≥λ64。
S2.2: taking singular value vector u corresponding to the first 10 maximum singular values of Q1,u2,...,u10Combined into UKAs a pilot sequence;
s2.3: will UKAnd sending the signal to the user through a downlink channel, wherein the signal received by the user side is as follows:
Figure BDA0002265889280000062
wherein
Figure BDA0002265889280000063
In order to be a downlink channel, the channel is,
Figure BDA0002265889280000064
is noise.
S2.4: processing the received signal by using an MMSE estimation method, and estimating to obtain giIt can be expressed as:
Figure BDA0002265889280000065
and for g10＝[g1 g2 … g10]Normalized to g0；
S3, selecting code word and feeding back its index
Precoding codebook
Figure BDA0002265889280000066
To find g in0Corresponding code word
Figure BDA0002265889280000067
And the index corresponding to the code word
Figure BDA0002265889280000068
Fed back to the base station, the index is defined by:
Figure BDA0002265889280000069
s4, designing precoding and sending information
Base station construction precoding
Figure BDA00022658892800000610
And using the precoding to send information s to the user, the user can estimate the downlink channel h according to the received signaldlThe received signal may be expressed as:
Figure BDA00022658892800000611
s5, channel utilization analysis
In order to analyze the performance of the precoding design method under the condition of the known steering matrix based on the channel partial reciprocity, which is provided by the invention, the channel utilization rate eta is defined as follows:
Figure BDA0002265889280000071
as shown in fig. 1, under the above-mentioned exemplary conditions, the respective parameters
Figure BDA0002265889280000072
And the relationship between the number of the base station antennas and the channel utilization rate can be seen from a simulation chart of the number of the base station antennas relative to the system channel utilization rate under the values of the R and the values of the different feedback numbers K. The precoding design method based on DFT is a channel utilization rate curve based on DFT method under different feedback numbers K, and the method provided by the invention is a channel utilization rate curve adopting the method provided by the invention under different values of K. As can be seen from FIG. 1, the reverseThe channel utilization increases with an increase in the feed K. Under the above exemplary conditions, the channel utilization may reach about 93%. And when K is 12, the channel utilization rate can reach more than 83% under the condition that the number of base station antennas is within 128. The method provided by the invention can achieve higher channel utilization rate under the condition of low feedback multi-antenna number, and has better system performance compared with a precoding design method based on DFT.
As shown in FIG. 2, under the above exemplary conditions, the number of antennas of different base stations is in the respective parameters
Figure BDA0002265889280000073
And under the value of R, the value of the feedback number K is a simulation diagram about the utilization rate of the system channel, and the relationship between the feedback number K and the channel utilization rate can be seen. The precoding design method based on DFT is a channel utilization rate curve based on the DFT method under different base station antenna numbers, and the method provided by the invention is a channel utilization rate curve adopting the method provided by the invention under different base station antenna numbers. As can be seen from fig. 2, the channel utilization increases as the number of base station antennas decreases. When the feedback number K is 20, the channel utilization rate of the system is more than 90% under the condition that the number of base station antennas is within 128. The method provided by the invention can achieve higher channel utilization rate under the condition of low feedback multi-antenna number, has better system performance compared with a precoding design method based on DFT, can achieve higher channel utilization rate, and can greatly reduce system training and feedback overhead in the CSI feedback process so as to improve the system performance. And by optimizing the parameters
Figure BDA0002265889280000074
And the value of R can further improve the performance.
It should be noted that the above embodiments can be freely combined as necessary. The foregoing has outlined rather broadly the preferred embodiments and principles of the present invention and it will be appreciated that those skilled in the art may devise variations of the present invention that are within the spirit and scope of the appended claims.

Claims (3)

  1. A precoding design method based on channel part reciprocity in an FDD massive MIMO system is characterized by comprising the following steps:
    s1, determining the acquired parameter values by knowing a precoding codebook, and designing a reference frame according to the parameter values; selecting a suitable reference vector according to the reference frame;
    s2, designing a pilot sequence according to the reference vector, sending the pilot sequence to a user, and processing a received signal of the user by using an MMSE estimation method;
    s3, selecting a code word corresponding to the processed parameter in the precoding codebook, and feeding back an index corresponding to the code word to the base station;
    s4, the base station constructs pre-coding and sends information to the user by using the pre-coding;
    the massive MIMO system comprises a single-antenna user, a base station, and a base station equipped with MtRoot antenna, LcClustering;
    step S1 specifically includes:
    s1.1, according to the parameters
    Figure FDA0003245193610000011
    And
    Figure FDA0003245193610000012
    value of (2) construct a frame of reference
    Figure FDA0003245193610000013
    The reference vector is formed by dimension MaX 1 of
    Figure FDA0003245193610000014
    A reference vector qaiComposition, defined as follows:
    Figure FDA0003245193610000015
    reference frame
    Figure FDA0003245193610000016
    Wherein
    Figure FDA0003245193610000017
    S1.2, calculating
    Figure FDA0003245193610000018
    Selecting the reference vector q corresponding to the maximum front R value1,q2,...,qRIs marked as Q;
    step S2 specifically includes:
    the channel is established based on the 3GPP TR 36.873V 12.7.0 standard, the time correlation item is not considered, the transmitting antenna field mode and the receiving antenna field mode among the antennas are respectively equal, and the antenna array is a uniform planar array;
    s2.1: performing singular value decomposition on Q;
    Q＝UDVH
    wherein
    Figure FDA0003245193610000021
    D＝diag(λ1,λ2,…,λR) And λ1≥λ2≥…≥λR；
    S2.2: taking singular value vector u corresponding to first K maximum singular values of Q1,u2,...,uKCombined into UKAs a pilot sequence;
    s2.3: will UKAnd sending the signal to the user through a downlink channel, wherein the signal received by the user side is as follows:
    Figure FDA0003245193610000022
    wherein
    Figure FDA0003245193610000023
    In order to be a downlink channel, the channel is,
    Figure FDA0003245193610000024
    is noise;
    s2.4: processing the received signal by using an MMSE estimation method, and estimating to obtain giIt can be expressed as:
    Figure FDA0003245193610000025
    and for gK＝[g1 g2 … gK]Normalized to g0。
  2. 2. The method according to claim 1, wherein step S3 is specifically:
    precoding codebook
    Figure FDA0003245193610000026
    To find g in0Code word of
    Figure FDA0003245193610000027
    Corresponding index
    Figure FDA0003245193610000028
    And feeding back the index to the base station, the index being defined by:
    Figure FDA0003245193610000029
  3. 3. the method according to claim 2, wherein step S4 is specifically:
    base station construction precoding
    Figure FDA00032451936100000210
    And sends information s to the user using this precodingThe received signal of the user at this time is represented as:
    Figure FDA00032451936100000211
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