CN112134815B - Downlink channel state estimation method for non-cell millimeter wave beam space system - Google Patents
Downlink channel state estimation method for non-cell millimeter wave beam space system Download PDFInfo
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- CN112134815B CN112134815B CN202010999886.0A CN202010999886A CN112134815B CN 112134815 B CN112134815 B CN 112134815B CN 202010999886 A CN202010999886 A CN 202010999886A CN 112134815 B CN112134815 B CN 112134815B
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- H04—ELECTRIC COMMUNICATION TECHNIQUE
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- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0224—Channel estimation using sounding signals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
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- H04L25/0202—Channel estimation
- H04L25/0224—Channel estimation using sounding signals
- H04L25/0226—Channel estimation using sounding signals sounding signals per se
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- H—ELECTRICITY
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- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0224—Channel estimation using sounding signals
- H04L25/0228—Channel estimation using sounding signals with direct estimation from sounding signals
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Abstract
The invention discloses a downlink channel state estimation method of a cell-free millimeter wave beam space system, which is suitable for downlink channel state estimation of the cell-free millimeter wave beam space system. A special pilot frequency sequence codebook is designed, and a scheme for directly estimating downlink channel state information is provided based on the codebook, so that the storage capacity of the codebook and the overall time of channel estimation can be reduced. Each wireless access point in the system needs to be equipped with an antenna or antenna array capable of transmitting a millimeter wave beam and needs to know the information radiated by the millimeter wave beam. The geographical locations of all wireless access points are stored at the central processor. In addition, a single/multiple base station operating in the centimeter wave band is required. All wireless access points and base stations are connected to a central processor by optical fibers. The user has two antennas, which operate in the centimeter and millimeter wave frequency bands, respectively.
Description
Technical Field
The invention relates to the field of communication, in particular to a novel downlink channel state estimation scheme which is suitable for a non-cell millimeter wave beam space system; the scheme can more conveniently estimate the downlink channel state information of the millimeter wave beam space system without the cell, and reduce the storage capacity of the codebook and the whole time of channel estimation.
Background
A millimeter wave beam space system without a cell is a novel millimeter wave communication system, the division of the traditional cellular cell is cancelled, and the effective transmission of millimeter wave signals is ensured by utilizing the macro diversity gain and the array gain of the space. In a cell-free millimeter wave beam space system, a large number of randomly distributed wireless access points are connected to a central processor by optical fibers. And each wireless access point transmits millimeter wave beams through the array, so that ultrahigh-rate data service is provided for users.
However, in the millimeter wave beam space system without the cell, the number of the wireless access points can reach dozens or even hundreds, which brings difficulty for directly estimating the downlink channel state information. The conventional scheme is to estimate the uplink channel state information through a pilot sequence by using the reciprocity of the uplink and the downlink to obtain the downlink channel state information. However, this scheme is not applicable to a scenario where a user is equipped with a single millimeter wave antenna.
Different from the traditional method, the invention designs a special pilot frequency sequence codebook by virtue of space resources and code resources, directly estimates the downlink channel state information of the millimeter wave beam space system without the cell, and can reduce the overall time of channel estimation.
Disclosure of Invention
Therefore, in order to solve the above-mentioned deficiencies, the present invention provides a downlink channel state estimation method for a millimeter wave beam space system without a cell; the method is suitable for a non-cell millimeter wave beam space system; the scheme can more conveniently estimate the downlink channel state information of the millimeter wave beam space system without the cell, and reduce the storage capacity of the codebook and the whole time of channel estimation.
The invention is realized in this way, construct a downlink channel state estimation method of the space system of millimeter wave beam of the non-cell, characterized by that;
the method comprises the following specific steps:
step one, clustering wireless access points;
designing a special pilot frequency sequence codebook;
step three, distributing a pilot frequency sequence codebook;
step four, transmitting a pilot frequency sequence;
and step five, estimating the state information of the downlink channel.
The invention discloses a downlink channel state estimation method of a cell-free millimeter wave beam space system, which is characterized by comprising the following steps of (1) estimating the downlink channel state of the cell-free millimeter wave beam space system; the implementation process of the step one is as follows;
firstly, a wireless access point top view needs to be constructed, a Cartesian coordinate system is established by taking the geographic position of a central processor as a zero point, and all wireless access points are placed in the coordinate system according to the relative geographic position of the central processor to obtain the wireless access point top view;
then, clustering the wireless access points according to the radiation information of the millimeter wave beams; suppose that all wireless access points can form the same beam towards M directions; and (4) measuring the maximum distance of the side lobe power of the beam greater than a certain value, and recording as d. In the top view of the wireless access points, each wireless access point passes through the wireless access points and faces to the direction of (360 DEG/M) (M-1) (1 ≦ M ≦ M)Drawing a straight line, and making two parallel lines which are perpendicular to the straight line and have a distance d; the range in the parallel line is marked as the interference area of the wireless access point; dividing wireless access points with crossed interference areas into a cluster, namely a wireless access point cluster; the clusters together form a wireless access point cluster set marked as ^mThe cardinality of the set is denoted as Nm(ii) a V. ismThe cluster containing the most wireless access points is marked as the maximum cluster, and the number of the wireless access points in the maximum cluster is marked as Lm。
The invention discloses a downlink channel state estimation method of a cell-free millimeter wave beam space system, which is characterized by comprising the following steps of (1) estimating the downlink channel state of the cell-free millimeter wave beam space system; the implementation process of the second step is as follows; considering (360 deg/M) × (M-1) direction, selecting orthogonal code group (such as Walsh function orthogonal code group) as basic orthogonal code group of the direction, and requiring that its contained orthogonal code number is not less than Lm. According to ^mSelecting the orthogonal codes arranged in the front in the basic orthogonal code group to form a new orthogonal code group corresponding to the wireless access point cluster; the orthogonal code groups are classified and arranged according to the beam direction and the wireless access point cluster, and a pilot frequency sequence codebook can be obtained; because the beam, the wireless access point cluster and the orthogonal code are involved in designing the pilot sequence codebook, the codebook is named as the pilot sequence codebook based on the beam-wireless access point cluster-orthogonal code; estimating (360 DEG/M) × (M-1) direction downlink channel state information by using the codebook, the number of required orthogonal codes is proportional to Lm(ii) a In general LmThe method is small, and the number of orthogonal codes needing to be stored can be reduced; in addition, the time taken to transmit the orthogonal codes can be reduced, thereby reducing the overall time for channel estimation.
The invention discloses a downlink channel state estimation method of a cell-free millimeter wave beam space system, which is characterized by comprising the following steps of (1) estimating the downlink channel state of the cell-free millimeter wave beam space system; the implementation process of the third step is as follows; the base station working in the centimeter wave frequency band adopts a time division multiplexing working mode, and the central processor sends the designed pilot frequency sequence codebook to all users needing service through the central processor; after receiving the pilot frequency sequence codebook, the user uses centimeter wave signals to feed back information to the central processor and switches to the millimeter wave frequency band.
The invention discloses a downlink channel state estimation method of a cell-free millimeter wave beam space system, which is characterized by comprising the following steps of (1) estimating the downlink channel state of the cell-free millimeter wave beam space system; the implementation process of the step four is as follows; after receiving the feedback information, the central processor distributes the pilot frequency sequence multiplied by the wireless access point cluster serial number to all wireless access points according to the pilot frequency sequence codebook based on the beam-wireless access point cluster-orthogonal code, and the wireless access points transmit millimeter wave beams to users.
The invention discloses a downlink channel state estimation method of a cell-free millimeter wave beam space system, which is characterized by comprising the following steps of (1) estimating the downlink channel state of the cell-free millimeter wave beam space system; the implementation process of the fifth step is as follows; after receiving the millimeter wave beam, the user estimates the downlink channel state information by adopting a traditional channel state estimation method (such as MMSE channel estimation and the like) based on pilot frequency; after all the channel state information is estimated by the user, the centimeter wave signals are fed back to the central processor. Thus, the estimation of the downlink channel state information is completed.
The invention has the following advantages: the design is suitable for the state estimation of the downlink channel of the millimeter wave beam space system without the cell. A special pilot frequency sequence codebook is designed, and a scheme for directly estimating downlink channel state information is provided based on the codebook, so that the storage capacity of the codebook and the overall time of channel estimation can be reduced. Each wireless access point in the system needs to be equipped with an antenna or antenna array capable of transmitting a millimeter wave beam and needs to know the information radiated by the millimeter wave beam. The geographical locations of all wireless access points are stored at the central processor. In addition, a single/multiple base station operating in the centimeter wave band is required. All wireless access points and base stations are connected to a central processor by optical fibers. The user has two antennas operating in the centimeter and millimeter wave frequency bands, respectively.
Drawings
FIG. 1 is a schematic diagram of a cell-free millimeter wave beam space system
FIG. 2 corresponds to an illustration of a top view of a wireless access point;
FIG. 3 is a schematic diagram of a codebook of pilot sequences based on beam-wireless access point cluster-orthogonal codes;
FIG. 4 is a flow chart of the present invention.
Detailed Description
The present invention will be described in detail with reference to fig. 1 to 4, and the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a downlink channel state estimation method of a cell-free millimeter wave beam space system through improvement. The invention directly estimates the downlink channel state information of the millimeter wave beam space system without the cell. A special pilot frequency sequence codebook is designed and obtained by comprehensively considering the spatial distribution of wireless access points, the radiation characteristics of millimeter wave beams and the characteristics of orthogonal codes, so that the storage capacity of the codebook and the overall time of channel estimation can be reduced. Based on the designed pilot frequency sequence codebook, an estimation scheme for directly estimating the downlink channel state information is provided. The implementation process is as follows;
as shown in fig. 1, the cellular-free millimeter wave beam space system has a central processor, a base station, five wireless access points (wireless access points 1#,2#,3#,4# and 5 #) and two users to be served (users 1# and 2#, respectively). A corresponding top view of the wireless access point is shown in fig. 2. Assume that the number of beam directions M =2.
On the basis of fig. 1, in conjunction with fig. 3 and flowchart 4, all steps of the embodiment are as follows:
step one, taking the geographic position of the central processor as a zero point, establishing a Cartesian coordinate system, and putting all the wireless access points into the coordinate system according to the relative geographic position of the central processor to obtain a top view of the wireless access points, as shown in FIG. 2. It is assumed that all wireless access points can form the same beam in 2 directions (0 o and 180 o). According to symmetry, the wireless access point cluster set lambda is easy to know1＝Λ2Cardinality of the set N1= N2=2, the number of wireless access points in the largest cluster is L1= L2=3;
and step two, selecting a 4-order Walsh function orthogonal code group (marked as { wi, 1 ≦ i ≦ 4 }) as a basic orthogonal code group for any one of the two directions. Due to Λ1(Λ2) The wireless access point cluster comprises 2 wireless access point clusters, wherein one wireless access point cluster comprises 2 wireless access points, and the other wireless access point cluster comprises 3 wireless access points. Thus, the new orthogonal code groups are respectively
And
the pilot sequence codebook based on the beam-wireless access point cluster-orthogonal code can be expressed in a matrix form as follows:
and step three, the base station working in the centimeter wave frequency band adopts a time division multiplexing working mode, and the central processor sends the designed pilot frequency sequence codebook W to 2 users needing service through the central processor. After receiving the pilot sequence codebook W, 2 users will feed back to the central processor by using centimeter wave signals and switch to a millimeter wave frequency band;
and step four, after receiving the feedback information, the central processor distributes the pilot frequency sequence multiplied by the wireless access point cluster serial number to all wireless access points according to a pilot frequency sequence codebook W based on the wave beam-wireless access point cluster-orthogonal code, and the wireless access points send millimeter wave beams to users. Such as: when the wireless access point 1# transmits the millimeter wave beam in the direction of 0 ° (180 °), the transmitted information is 1 × w1, when the wireless access point 3# transmits the millimeter wave beam in the direction of 0 ° (180 °), the transmitted information is 2 × w1, and when the wireless access point 5# transmits the millimeter wave beam in the direction of 0 ° (180 °), the transmitted information is 2 × w3;
and step five, after 2 users receive the millimeter wave, estimating the state information of the downlink channel by adopting an MMSE channel estimation method. After estimating all the channel state information, 2 users feed back the information to the central processor by using centimeter wave signals. Thus, the estimation of the downlink channel state information is completed.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (4)
1. A downlink channel state estimation method of a non-cell millimeter wave beam space system is characterized in that; the method comprises the following specific steps:
step one, clustering wireless access points; the implementation process is as follows;
firstly, a wireless access point top view needs to be constructed, a Cartesian coordinate system is established by taking the geographic position of a central processor as a zero point, and all wireless access points are placed in the coordinate system according to the relative geographic position of the central processor to obtain the wireless access point top view;
then, clustering the wireless access points according to the radiation information of the millimeter wave beams; assuming that all wireless access points can form the same beam towards M directions; measuring the maximum distance of the beam side lobe power larger than a certain numerical value, and recording as d; in the top view of the wireless access points, each wireless access point is crossed, a straight line is drawn towards the direction of (360 DEG/M) × (M-1) (M is more than or equal to 1 and less than or equal to M), and two parallel lines with the vertical distance d from the straight line are drawn; the range in the parallel line is marked as the interference area of the wireless access point; dividing the wireless access points with crossed interference areas into a cluster, namely a wireless access point cluster; the clusters together form a wireless access point cluster set, denoted as ΛmThe cardinality of the set is denoted as Nm(ii) a Will be ΛmThe cluster containing the most wireless access points is marked as the maximum cluster, and the wireless access in the maximum clusterThe number of access points is marked as Lm；
Designing a special pilot frequency sequence codebook; the implementation process is as follows; considering (360 deg/M) × (M-1) direction, selecting orthogonal code group as basic orthogonal code group of the direction, and requiring that the number of orthogonal codes contained in the orthogonal code group is not less than Lm(ii) a According to ΛmSelecting the orthogonal codes arranged in the front of the basic orthogonal code group to form a new orthogonal code group corresponding to the wireless access point cluster; the orthogonal code groups are classified and arranged according to the beam direction and the wireless access point cluster, and a pilot frequency sequence codebook can be obtained; because the wave beam, the wireless access point cluster and the orthogonal code are involved in designing the pilot sequence codebook, the codebook is named as the pilot sequence codebook based on the wave beam-wireless access point cluster-orthogonal code; estimating the downlink channel state information in the (360 DEG/M) × (M-1) direction by using the codebook, wherein the number of required orthogonal codes is proportional to Lm(ii) a In general LmThe method is small, and the number of orthogonal codes needing to be stored can be reduced; in addition, the time occupied by transmitting the orthogonal code can be reduced, so that the overall time of channel estimation is reduced;
step three, distributing a pilot frequency sequence codebook;
step four, transmitting a pilot frequency sequence;
and step five, estimating the state information of the downlink channel.
2. The method for estimating the downlink channel state of the cell-free millimeter wave beam space system according to claim 1, wherein the downlink channel state is estimated by using a plurality of millimeter wave beams; the implementation process of the third step is as follows; the base station working in the centimeter wave frequency band adopts a time division multiplexing working mode, and the central processor sends the designed pilot frequency sequence codebook to all users needing service through the central processor; after receiving the pilot frequency sequence codebook, the user uses centimeter wave signal to feed back information to the central processor and switches to millimeter wave frequency band.
3. The method for estimating the downlink channel state of the cell-free millimeter wave beam space system according to claim 1, wherein the downlink channel state is estimated by using a plurality of millimeter wave beams; the implementation process of the step four is as follows; after receiving the feedback information, the central processor distributes the pilot frequency sequence multiplied by the serial number of the wireless access point cluster to all the wireless access points according to the pilot frequency sequence codebook based on the wave beam wireless access point cluster-orthogonal code, and the wireless access points send millimeter wave beams to users.
4. The method for estimating the downlink channel state of the cell-free millimeter wave beam space system according to claim 1, wherein the downlink channel state is estimated by using a plurality of millimeter wave beams; the implementation process of the fifth step is as follows; after receiving millimeter wave, a user estimates downlink channel state information by adopting a traditional channel state estimation method based on pilot frequency; after estimating all channel state information, the user feeds back centimeter wave signals to the central processor; thus, the estimation of the downlink channel state information is completed.
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