TWI680653B - Multi-cell coordination system and channel calibration method thereof - Google Patents

Abstract

The invention provides a multi-base station coordination system and a channel correction method thereof. This system includes a reference device, a base station, and a server. The reference device receives a beam-coded downlink reference signal from a base station via a pointing beam. The base station receives the beam-coded uplink reference signal from the reference device via the pointing beam. The server receives uplink channel information and downlink channel information. The uplink channel information is generated based on the uplink reference signal, and the downlink channel information is generated based on the downlink reference signal. The server obtains the channel correction coefficient according to the uplink channel information and the downlink channel information. This channel correction coefficient is used to estimate the downstream channel. This can solve the problems of the existing coordination system and can be applied to multi-beam base stations.

Description

Multi-base station coordination system and channel correction method

The invention relates to a multi-base station coordination technology, and in particular to a multi-base station coordination system and a channel correction method thereof.

Compared with the traditional Fourth Generation (4G) Long Term Evolution (LTE) system, more antenna numbers will be applied to the fifth generation (5G) New Radio (NR) system in the future To improve transmission efficiency. In theory and practical applications, multi-antenna systems have been proven to use technologies such as Precoding and / or Beamforming, while allowing multiple User Equipment (UE) to access wireless resources, thereby Increase spectrum use efficiency. In addition, recent studies have pointed out that if the number of antennas carried by the base station is more than four times the number of users, the spectrum utilization efficiency will grow linearly with the number of users.

However, due to physical limitations, it is difficult for a general base station to mount a massive antenna. Therefore, related studies have proposed that, by coordinating multiple base stations, Data transmission to user equipments together can achieve performance equivalent to a huge number of antennas. Such an architecture is called a Multi-Cell Coordination (MCC) system. In the MCC system, all base stations are controlled by a Coordination Server, and this Coordination Server can select the best transmission mode according to the user's situation. Because the clock source of each base station in the MCC system is independent, there may be Carrier Frequency Offset (CFO) between the base stations, and it is the largest compared with the massive antenna system Point of difference. In addition, other imperfect factors (for example, sampling clock offset (SCO) caused by CFO, timing offset due to transmission delay, and downstream linear phases of the CFO caused by the opposite linear phase , Time-varying effects of RF response, etc.) will also cause inaccurate channel estimation, and after precoding, Inter-Cell Interference (ICI) and Inter-User Interference (Inter-User Interference, IUI), thereby reducing system capacity. It can be known that the existing MCC system still needs to be improved.

In view of this, the present invention provides a multi-base station coordination system and a channel correction method thereof, which can solve the problems of the existing MCC system and can be applied to the multi-beam technology.

The multi-base station coordination system according to the embodiment of the present invention includes at least but not limited to a reference device, a base station, and a server. The base station includes at least one antenna, and these antennas provide a directional beam. The base station performs first precoding on the downlink reference signal to be transmitted via the pointing beam, and the first precoding is based on the beam coding. Reference equipment The receiver receives a downlink reference signal from the base station via a directional beam. The reference device performs a second precoding on the uplink reference signal to be transmitted via the directional beam, and the second precoding is based on the beam coding. The base station receives the uplink reference signal from the reference device via the pointing beam. The server receives the uplink channel information from the base station and the downlink channel information from the reference device. The uplink channel information is generated based on the uplink reference signal and the second precoding, and the downlink channel information is generated based on the downlink reference signal and the first precoding. The server obtains the channel correction coefficient according to the uplink channel information and the downlink channel information. This channel correction coefficient is used to estimate the downstream channel.

On the other hand, the channel correction method according to the embodiment of the present invention includes at least but not limited to the following steps. The base station performs first precoding on the downlink reference signal to be transmitted through the pointing beam, and the first precoding is based on the beam coding. The reference device receives the downlink reference signal from the base station through the directional beam through the reference device. The reference device is used to perform a second precoding on the uplink reference signal to be transmitted through the directional beam, and the second precoding is based on the beam coding. A directional beam is provided through a base station to receive an uplink reference signal from a reference device. Receive the uplink channel information from the base station and the downlink channel information from the reference device through the server. The uplink channel information is generated based on the uplink reference signal and the second precoding, and the downlink channel information is generated based on the downlink reference signal and the first precoding. The channel correction coefficient is obtained by the server according to the uplink channel information and the downlink channel information, and this channel correction coefficient is used to estimate the downlink channel.

Based on the above, the multi-base station coordination system and the channel correction method in the embodiments of the present invention are adapted to different beam technologies in the future 5G NR system, aiming at different beams. Corresponding channels provide corresponding channel correction coefficients. In addition, the reference device solves the problems of synchronization between base stations, time-varying effects of RF response, frequency selective attenuation channels, and downlink channel status information acquisition, thereby achieving the performance of a huge number of antenna systems.

In order to make the above features and advantages of the present invention more comprehensible, embodiments are hereinafter described in detail with reference to the accompanying drawings.

1‧‧‧Multi-base station coordination system

BS1 ~ BSj‧‧‧Base Station

RA1 ~ RAr‧‧‧Reference device

CS‧‧‧Server

UE1 ~ UEm, UEu‧‧‧user equipment

b1 ~ bh‧‧‧ pointing beam

UL_RS_R1, UL_RS_R2, UL_RS_R3, UL_RS_U1‧‧‧ uplink reference signal

DL_RS_R1, DL_RS_R2, DL_RS_R3, DL_RS_U1‧‧‧ downlink reference signal

S210 ~ S260, S410 ~ S430, S510 ~ S520, S610 ~ S630‧‧‧Steps

P _{BS, ( b, n ) , p} , P _{UE, ( r, k ) , p} ‧‧‧ precoding

α _{b, n} , β _{r, k} , α _{r, k} , β _{b, n} ‧‧‧ RF response

g _{( b, n ) → ( r, k )} , g _{( r, k ) → ( b, n )} ‧‧‧airway

、θ _r,k 、

‧‧‧初始相位 θ _{b, n} ,

, Θ _{r, k} ,

‧‧‧ initial phase

ε _b , η _r ‧‧‧ carrier frequency

t, T ₀ ‧‧‧ time

FIG. 1 is a schematic diagram of a multi-base station coordination system according to an embodiment of the present invention.

FIG. 2 is a flowchart of a channel correction method according to an embodiment of the present invention.

3 is a transmission model between a base station and a reference device according to an embodiment of the present invention.

FIG. 4 is a flowchart of carrier frequency offset estimation according to an embodiment of the present invention.

FIG. 5 is a flowchart of coefficient normalization according to an embodiment of the present invention.

FIG. 6 is a flowchart of estimating an equivalent downlink channel according to an embodiment of the present invention.

FIG. 1 is a schematic diagram of a multi-base station coordination system 1 according to an embodiment of the present invention. Please refer to FIG. 1. This multi-base station coordination system 1 includes at least but not limited to one or more base stations BS1 ~ BSj, one or more reference devices RA1 ~ RAr, a server CS, and one or more uses User equipment UE1 ~ UEn. j, r, n are positive integers.

The base stations BS1 ~ BSj may have various implementation modes, such as (but not limited to) Home Evolved Node B (HeNB), eNB, Advanced Base Station (ABS), base transceiver System (Base Transceiver System; BTS), repeater (relay), repeater (repeater), and / or satellite-based communication base station. In this embodiment, each of the base stations BS1 to BSj has one or more antennas, and these antennas can provide multiple directional beams b1 to bh, which are directed to a specific direction. For example, the base station BSb (b is a positive integer between 1 and j) uses beam sweeping technology to sequentially use different directional beams b1 to bh to transmit wireless signals. h and j are positive integers.

The reference devices RA1 ~ RAr may have various implementations, such as (but not limited to) a mobile device, a personal computer, or an idle base station. The so-called idle base station refers to a base station judged by the server CS that the current service is not provided or the load is below a certain threshold. The server CS may also schedule the base stations BS1 ~ BSj, and in turn use any idlers in the base stations BS1 ~ BSj as reference devices RA1 ~ RAr. In this embodiment, each of the reference devices RA1 to RAr has one or more antennas. r is a positive integer.

The server CS can be various types of computing devices such as servers, computer hosts, and workstations. In this embodiment, the server CS is wired or wirelessly connected to the base stations BS1 to BSj and the reference devices RA1 to RAr.

The user equipment UE1 ~ UEm may have multiple implementations, such as including (but not limited to) a mobile station, an advanced mobile station (AMS), a telephone device, a customer premise equipment (CPE), and no Line sensors and more. The user equipment UE1 ~ UEm can be served by any one of the base stations BS1 ~ BSj. m is a positive integer.

It should be noted that the base stations BS1 to BSj and the reference devices RA1 to RAr in this embodiment may use a Global Positioning System (GPS) signal for time synchronization. The base stations BS1 to BSj, the reference devices RA1 to RAr, and the user equipment UE1 to UEm have independent clock sources. That is, each device has its own carrier frequency. For example, the carrier frequency of the base station BSb is ε _b and the carrier frequency of the reference device RAr is η _r . In addition, the base stations BS1 to BSj, the reference devices RA1 to RAr, and the user equipment UE1 to UEm can support fourth-generation (4G), fifth-generation (5G), or later generation mobile communication technologies, which are not limited in the present invention.

In order to facilitate the understanding of the operation flow of the embodiments of the present invention, the following describes in detail the operation flow of the multi-base station coordination system 1 in the embodiments of the present invention with many embodiments. In the following, the method according to the embodiment of the present invention will be described with each device in the multi-base station coordination system 1. Each process of the method in the embodiment of the present invention can be adjusted according to the implementation situation, and is not limited to this. In addition, for the convenience of description, one or more of base stations BS1 ~ BSj, reference devices RA1 ~ RAr, and user equipment UE1 ~ UEm will be selected as examples, and the operation of other devices of the same type can be referred to. The corresponding description will not be repeated.

FIG. 2 is a flowchart of a channel correction method according to an embodiment of the present invention. Referring to FIG. 1 and FIG. 2, the base station BSb performs first precoding on the downlink reference signal DL_RS_R2 to be transmitted via the pointing beam bp (p is a positive integer between 1 and h) (step S210). Specifically, the base station BSb can pass through several different pointing carriers b1 ~ bh send different or same downlink signals. In order to identify and / or improve transmission efficiency, the base station BSb performs first precoding based on beam coding on all or part of the downlink signals directed to the carriers b1 to bh. This beam coding may be based on a beam codebook (for example, Precoding Matrix Indicators (PMI)), or other precoding matrix. That is, the downlink signals directed to the carriers b1 to bh are pre-coded through code words, coefficients, or weights in the pre-coding matrix. It should be noted that, in this embodiment, the directional beam bp is used as an example description, and the rest of the description of the directional beam will not be repeated.

The reference device RAr receives the downlink reference signal DL_RS_R2 from the base station BSb via the pointing beam bp (step S220). Specifically, after the base station BSb transmits the downlink reference signal DL_RS_R2 at time t (using a Time Division Duplexing (TDD) system as an example), the reference device RAr may be assigned or decide to receive the signal via the pointing beam bp.

(b,n)→(r,k)代表透過第b基地台(即，基地台BSb)的第n根天線傳送，並透過第r參考裝置(即，參考裝置RAr)的第k天線接收；P _BS,(b,n),p 是基地台BSb針對第p波束(即，指向波束bp)的第一預編碼；β _r,k 是參考裝置RAr在第k根天線接收端的射頻響應；α _b,n 是基地台BSb在第n根天線傳送端的射頻響應；g _{(b,n)→(r,k)}為空中(Over-The-Air)通道(若具有互易性(reciprocity)則g _{(b,n)→(r,k)}亦可視為g _{(r,k)→(b,n)})；θ _b,n 是基地台BSb在第n根天線傳送端的初始相位；

是參考裝置RAr在第k根天線接收端的初始相位；ε _b 為基地台BSb的載波頻率；η _r 是參考裝置RAr的載波頻率；

是估測到的載波頻率偏移。參考裝置RAr接著可將針對指向波束bp所估測的下行通道資訊傳送給伺服器CS。 Please refer to FIG. 3, which is a link model between a base station BSb and a reference device RAr according to an embodiment of the present invention. It is assumed that the n-th antenna of the base station BSb provides a pointing beam bp, and the k-th antenna of the reference device RAr receives a signal via the pointing beam bp. The downlink reference signal DL_RS_R2 (from the base station BSb to the reference device RAr, that is, via the downlink) is a training signal known to both the base station BSb and the reference device RAr. The reference device RAr can estimate the downlink channel information of the pointing beam bp based on the downlink reference signal DL_RS_R2. The mathematical expression of this downlink channel is as follows:

( b, n ) → ( r, k ) represents transmitting through the n-th antenna of the b-th base station (ie, base station BSb), and receiving through the k-th antenna of the r-th reference device (ie, reference device RAr); P _{BS, ( b, n ) , p} is the first precoding of the base station BSb for the p- _th beam (ie, the pointing beam bp); β _{r, k} is the radio frequency response of the reference device RAr at the receiving end of the k-th antenna; α _{b, n} is the radio frequency response of the base station BSb at the n-th antenna transmitting end; g _{( b, n ) → ( r, k )} is the Over-The-Air channel (if reciprocity is available, g _{( b, n ) → ( r, k )} can also be regarded as g _{( r, k ) → ( b, n )} ); θ _{b, n} is the initial phase of the base station BSb at the n-th antenna transmitting end;

Is the initial phase of the reference device RAr at the receiving end of the kth antenna; ε _b is the carrier frequency of the base station BSb; η _r is the carrier frequency of the reference device RAr;

Is the estimated carrier frequency offset. The reference device RAr may then transmit the downlink channel information estimated for the pointing beam bp to the server CS.

可事先估測或是預 設的。以下將說明如何估測載波頻率偏移

。圖4是依據本發明一實施例之載波頻率偏移估測的流程圖。請參照圖1及圖4，以下將以基地台BSb,BSj、及參考裝置RAr作為範例說明。參考裝置RAr分別對基地台BSb,BSj發送上行參考訊號UL_RS_R2,UL_RS_R3(步驟S410)。基地台BSb,BSj分別基於上行參考訊號UL_RS_R2,UL_RS_R3得出兩組對應的上行通道資訊(步驟S420)。而伺服器CS基於這些上行通道資訊得出兩基地台BSb,BSj的(相對)載波頻率偏移(步驟S430)。換句而言，本發明實施例是透過兩基地台BSb,BSj在載波頻率偏移上的差異來作為相對載波頻率偏 移。藉此，基地台BSb即可基於針對自身的載波頻率偏移得出如表示式(1)所示的下行通道資訊。需說明的是，所有基地台BS1~BSj都可基於圖4之實施例得出其對應相對載波頻率偏移，以下將不再贅述。此外，參考裝置RAr尚需要再經過時間D後發送上行參考訊號UL_RS_R2,UL_RS_R3，而伺服器CS會藉由兩時間點之間的通道變化量來得出載波頻率偏移。 It is worth noting that the aforementioned carrier frequency offset

Can be estimated in advance or preset. The following explains how to estimate the carrier frequency offset

. FIG. 4 is a flowchart of carrier frequency offset estimation according to an embodiment of the present invention. Please refer to FIG. 1 and FIG. 4, the following will take the base stations BSb, BSj, and the reference device RAr as examples. The reference device RAr sends uplink reference signals UL_RS_R2, UL_RS_R3 to the base stations BSb and BSj, respectively (step S410). The base stations BSb and BSj respectively obtain two sets of corresponding uplink channel information based on the uplink reference signals UL_RS_R2 and UL_RS_R3 (step S420). The server CS obtains the (relative) carrier frequency offsets of the two base stations BSb and BSj based on the uplink channel information (step S430). In other words, in the embodiment of the present invention, the difference in carrier frequency offset between the two base stations BSb and BSj is taken as the relative carrier frequency offset. With this, the base station BSb can obtain the downlink channel information as shown in Expression (1) based on the carrier frequency offset for itself. It should be noted that all the base stations BS1 to BSj can obtain their corresponding relative carrier frequency offsets based on the embodiment of FIG. 4, which will not be described in detail below. In addition, the reference device RAr still needs to send the uplink reference signals UL_RS_R2, UL_RS_R3 after the time D has passed, and the server CS will obtain the carrier frequency offset by the channel change amount between the two time points.

(r,k)→(b,n)代表透過參考裝置RAr的第k天線傳送，並透過基地台BSb的第n根天線接收；P _RA,(r,k),p 是參考裝置RAr針對指向波束bp的第二預編碼；β _b,n 是基地台BSb在第n根天線接收端的射頻響應；α _r,k 是參考裝置RAr在第k根天線傳送端的射頻響應； g _{(r,k)→(b,n)}為空中通道(若具有互易性則g _{(r,k)→(b,n)}亦可視為g _{(b,n)→(r,k)})；

是基地台BSb在第n根天線接收端的初始相位；θ _r,k 是參考裝置RAr在第k根天線傳送端的初始相位；ε _b 為基地台BSb的載波頻率；η _r 是參考裝置RAr的載波頻率；

是估測到的載波頻率偏移(可參考圖4之實施例估測而得)。基地台BSb接著可將針對指向波束bp所估測的上行通道資訊傳送給伺服器CS。 Please return to FIG. 2, the reference device RAr performs second precoding on the uplink reference signal UL_RS_R2 to be transmitted via the pointing beam bp based on the beam coding (step S230). In this embodiment, the second precoding may refer to the description of the first precoding, and may use the same or different precoding matrices. Next, the reference device RAr transmits an uplink reference signal UL_RS_R2 at time t + T ₀ , so that the base station BSb provides a pointing beam bp to receive the uplink reference signal UL_RS_R2 from the reference device RAr (step S240). The uplink reference signal UL_RS_R2 (from the reference device RAr to the base station BSb, that is, via the uplink) is a training signal known to both the base station BSb and the reference device RAr. The base station BSb can estimate the uplink channel information of the pointing beam bp based on this uplink reference signal UL_RS_R2. The mathematical expression of this uplink channel is as follows:

( r, k ) → ( b, n ) represents transmitting through the k-th antenna of the reference device RAr and receiving through the n-th antenna of the base station BSb; P _{RA, ( r, k ) , p} is the reference device RAr for pointing The second precoding of the beam bp; β _{b, n} is the RF response of the base station BSb at the receiving end of the nth antenna; α _{r, k} is the RF response of the reference device RAr at the transmitting end of the kth antenna; g _{( r, k ) → ( b, n )} is the air channel (if there is reciprocity, g _{( r, k ) → ( b, n )} can also be regarded as g _{( b, n ) → ( r, k )} );

Is the initial phase of the base station BSb at the receiving end of the nth antenna; θ _{r, k} is the initial phase of the reference device RAr at the transmitting end of the kth antenna; ε _b is the carrier frequency of the base station BSb; η _r is the carrier of the reference device RAr frequency;

Is the estimated carrier frequency offset (can be estimated by referring to the embodiment of FIG. 4). The base station BSb can then transmit the uplink channel information estimated for the pointing beam bp to the server CS.

Please return to FIG. 2. The server CS can then receive the uplink channel information from the base station BSb (for example, mathematical expression (2)) and the downlink channel information from the reference device RAr (for example, mathematical expression (1)) (Step S250), the server CS obtains a channel correction coefficient based on the uplink channel information and the downlink channel information (step S260).

其中，通道校正係數c _{(b,n)→(r,k)}(t+T ₀)的時變相位是由

造成。 Specifically, the server CS uses the ratio of the uplink channel information and the downlink channel information corresponding to different time points as the correction coefficient:

Among them, the time-varying phase of the channel correction coefficient c _{( b, n ) → ( r, k )} ( t + T ₀ ) is

Cause.

c _{(1,1)→(r,1)}(t+T ₀)是第二通道校正係數，(1,1)→(r,1)代表透過第1基地台(即，基地台BS1)的第1根天線傳送，並透過參考裝置RAr的第1天線接收；P _BS,(1,1),1是基地台BSb針對第1波束(即，指向波束b1)的第一預編碼；β _r,1是參考裝置RAr在第1根天線接收端的射頻響應；α_1,1是基地台BS1在第1根天線傳送端的射頻響應；

是基地台BSb在第n根天線傳送端的初始相位及基地台BS1在第1根天線傳送端的初始相位的差異跟BS1在第1根天線接收端的初始相位及基地台BSb在第n根天線傳送端的初始相位的差異的總合(即，

)及參考裝置RAr在第k根天線接收端的初始相位的差異；ε₁為基地台BS1的載波頻率；

是估測到的載波頻率偏移；P _RA,(r,1),1是參考裝置RAr針對指向波束b1的第二預編碼；β_1,1是基地台BS1在第1根天線接收端的射頻響應；α _r,1是參考裝置RAr在第1根天線傳送 端的射頻響應。 FIG. 5 is a flowchart of coefficient normalization according to an embodiment of the present invention. Please refer to FIG. 1 and FIG. 5, the server CS can obtain the second channel based on the uplink channel information and the downlink channel information (assuming that the first antenna is used) between the base station BS1 and the reference device RAr and through another pointing beam b1. Channel correction coefficient (step S510). For the generation method of the second channel correction coefficient, refer to the foregoing description in FIG. 2, that is, the reference device RAr estimates the downlink channel information for the pointing beam b1 based on the downlink reference signal RL_RS_R1 from the base station BS1, and the base station BS1 is based on the reference device from the reference device. The uplink reference signal UL_RS_R1 of RAr estimates the uplink channel information for the pointing beam b1, and the server CS then obtains the second channel correction coefficient c _{(1 , 1) → ( r, 1 )} ( t + T ₀ ). The server CS then normalizes the channel correction coefficient obtained in step S260 according to the second channel correction coefficient (step S520):

c _{(1 , 1) → ( r, 1)} ( t + T ₀ ) is the second channel correction coefficient, and (1,1) → ( r, 1) represents the signal passing through the first base station (ie, base station BS1). The first antenna transmits and is received through the first antenna of the reference device RAr; P _{BS, (1 , 1) , 1} is the first precoding of the base station BSb for the first beam (ie, the pointing beam b1); β _{r , 1} is the radio frequency response of the reference device RAr at the receiving end of the first antenna; α _{1 , 1} is the radio frequency response of the base station BS1 at the transmitting end of the first antenna;

The difference between the initial phase of the base station BSb at the n-th antenna transmitting end and the initial phase of the base station BS1 at the first antenna transmitting end is different from the initial phase of BS1 at the receiving end of the first antenna and the base station BSb at the n-th antenna transmitting end. The sum of the differences in the initial phases (i.e.,

) And the initial phase difference between the reference device RAr at the receiving end of the kth antenna; ε ₁ is the carrier frequency of the base station BS1;

Is the estimated carrier frequency offset; P _{RA, ( r, 1) , 1} is the second precoding of the reference device RAr for the pointing beam b1; β _{1 , 1} is the radio frequency of the base station BS1 at the receiving end of the first antenna Response; α _{r, 1} is the radio frequency response of the reference device RAr at the transmitting end of the first antenna.

It should be noted that the base station BS1, the first antenna, and the directional beam b1 are taken as an example. However, in other embodiments, the server CS may also select other base stations, other antennas, and / or other directional beams. Any combination is used as the normalization benchmark. It should be emphasized again that the foregoing only refers to the n-th antenna and the directional beam bp of the base station BSb and the k-th antenna of the reference device RAr as illustrations, and to other base stations, other antennas, other directional beams and other reference devices For the combined channel correction coefficients, please refer to the foregoing description, and will not be repeated here.

η _u 為第u使用者設備(即，使用者設備UEu)的載波頻率，

(t+T ₀)為藉由參考裝置RA1~RAr與基地台BS1~BSj計算出的通道校正係數。換句而言，伺服器CS是利用參考裝置 RA1~RAr與基地台BS1~BSj計算出的通道校正係數來計算使用者設備UEu的下行通道資訊。 It is worth noting that the aforementioned channel correction coefficient can be used to estimate the downlink channel between the base station BSb and the user equipment UE1 ~ UEm, which will be described later. FIG. 6 is a flowchart of estimating an equivalent downlink channel according to an embodiment of the present invention. Referring to FIGS. 1 and 6, at time t + T ₁ , the user equipment UEu (u is a positive integer between 1 and m) transmits the uplink reference signal UL_RS_U1 to the base station BSb via the pointing beam bp1 (step S610). The base station BSb can estimate the (equivalent) downlink via the pointing beam bp according to the uplink reference signal UL_RS_U1 and the (normalized) channel correction coefficient c ' _{( b, n ) → ( r , k )} ( t + T ₀ ). Channel (step S620):

η _u is the carrier frequency of the u-th user equipment (ie, user equipment UEu),

( t + T ₀ ) is the channel correction coefficient calculated by the reference devices RA1 ~ RAr and the base stations BS1 ~ BSj. In other words, the server CS uses the channel correction coefficients calculated by the reference devices RA1 ~ RAr and the base stations BS1 ~ BSj to calculate the downlink channel information of the user equipment UEu.

h _BS1→UE1代表基地台BS1到使用者設備UE1的通道向量(其餘依此類推)，

(t+T ₁)為通道校正係數的矩陣， H ^CFO (t+T ₁)為載波頻率偏移的矩陣。 In addition, the downlink channel matrix for the pointing beam bp can be expressed as:

h _{BS 1 → UE 1} represents the channel vector from the base station BS1 to the user equipment UE1 (the rest can be deduced by analogy),

( t + T ₁ ) is a matrix of channel correction coefficients, and H ^CFO ( t + T ₁ ) is a matrix of carrier frequency offset.

The base station BSb may then perform third precoding on the signal sent to the user equipment UEu according to the estimated downlink channel (step S630). The third precoding is based on, for example, Zero forcing, Minimum Mean-Square Error (MMSE), or other equalization algorithms. At time t + T ₂ , the base station BSb can serve the user equipment UEu with the downlink signal generated by the third precoding. It should be noted that the transmission behavior between the base station BSb and the user equipment UEu is taken as an example here. For other combinations of the base station and the user equipment, reference may be made to the foregoing description, and details are not described herein.

In summary, the multi-base station coordination system and channel correction method of the embodiments of the present invention use a reference device to resolve time-varying effects of synchronization and radio frequency response between base stations. Problems such as response, frequency selective attenuation channel, and downlink channel status information. In addition, the embodiments of the present invention further consider the application of multi-beam transmission, so that it can be applied to communication systems of 5G or later generations.

Although the present invention has been disclosed as above with the examples, it is not intended to limit the present invention. Any person with ordinary knowledge in the technical field can make some modifications and retouching without departing from the spirit and scope of the present invention. The protection scope of the present invention shall be determined by the scope of the attached patent application.

Claims (10)

A multi-base station coordination system includes: a base station including at least one antenna, wherein the at least one antenna provides a directional beam, the base station performs a first precoding on a next-line reference signal to be transmitted via the directional beam; Wherein the first precoding is based on a beam coding and a reference device, wherein the reference device receives the downlink reference signal from the base station via the pointing beam, and the reference device responds to an uplink to be transmitted via the pointing beam. The reference signal performs a second precoding, wherein the second precoding is based on the beam coding, and the base station receives the uplink reference signal from the reference device via the pointing beam; and a server receives the base signal from the base station. The uplink channel information and the downlink channel information from the reference device, wherein the uplink channel information is generated based on the uplink reference signal and the second precoding, and the downlink channel information is based on the downlink reference signal and the first Generated by precoding, the server obtains information based on the uplink channel information and the downlink channel information A channel correction factor, wherein the channel correction coefficients for estimating a downlink channel. The multi-base station coordination system according to item 1 of the patent application scope further includes: a user equipment transmitting a second uplink reference signal via the pointing beam, and the base station according to the second uplink reference signal and the channel The correction coefficient estimates the downlink channel via the pointing beam, and the base station performs a third precoding on the signal sent to the user equipment according to the estimated downlink channel. The multi-base station coordination system described in item 1 of the scope of patent application, further includes: a second base station, and the reference device sends a third uplink reference signal to the base station and the second base station, respectively, and the base station And the second base station respectively obtain two second uplink channel information based on the third uplink reference signal, and the server obtains a carrier frequency offset based on the second second uplink channel, where the base station is based on the The carrier frequency offset and the uplink reference signal obtain the uplink channel information, and the reference device obtains the downlink channel information based on the carrier frequency offset and the downlink reference signal. The multi-base station coordination system according to item 1 of the patent application scope further includes: a third base station, and the server is based on the third base station and the reference device via a second pointing beam. The three uplink channel information and the second downlink channel information obtain a second channel correction coefficient, and the server normalizes the channel correction coefficient according to the second channel correction coefficient. The multi-base station coordination system according to item 1 of the patent application scope, wherein the downlink channel information and the uplink channel information are more related to the initial phase of the transmitting end and the receiving end, the carrier frequency offset, and the base station and the reference The carrier frequency of the device. A channel correction method includes: performing a first precoding on a next-line reference signal to be transmitted through a directional beam through a base station, wherein the first precoding is based on the beam coding; and passing the directional beam through a reference device Receiving the downlink reference signal from the base station; performing a second precoding on an uplink reference signal to be transmitted via the pointing beam through the reference device, wherein the second precoding is based on a beam coding; through a base station Providing the directional beam to receive the uplink reference signal from the reference device; receiving uplink channel information from the base station and downlink channel information from the reference device through a server, wherein the uplink channel information is based on the uplink reference The signal and the second precoding are generated, and the downlink channel information is generated based on the downlink reference signal and the first precoding; and a channel correction is obtained by the server according to the uplink channel information and the downlink channel information Coefficient, where the channel correction coefficient is used to estimate the row channel. The channel correction method according to item 6 of the patent application scope, wherein after the step of deriving the channel correction coefficient, the method further includes: transmitting a second uplink reference signal through the directional beam through a user equipment; The second uplink reference signal and the channel correction coefficient estimate the downlink channel via the pointing beam; and a third precoding is performed on the signal sent to the user equipment through the base station and according to the estimated downlink channel . The channel correction method according to item 6 of the patent application scope, wherein before the step of receiving the downlink reference signal from the base station, the method further includes: sending a first to the base station and a second base station through the reference device, respectively. Three uplink reference signals; obtaining two second uplink channel information based on the third uplink reference signal through the base station and the second base station; and obtaining a carrier frequency offset based on the two second uplink channels through the server Shift, wherein the uplink channel information is derived based on the carrier frequency offset and the uplink reference signal, and the downlink channel information is derived based on the carrier frequency offset and the downlink reference signal. The channel correction method according to item 6 of the patent application scope, wherein after the step of obtaining the channel correction coefficient, the method further includes: passing the server through a third base station and the reference device through a second pointing The third uplink channel information and the second downlink channel information of the beam obtain a second channel correction coefficient; and the server normalizes the channel correction coefficient according to the second channel correction coefficient. The channel correction method according to item 6 of the scope of patent application, wherein the downlink channel information and the uplink channel information are more related to the initial phase of the transmitter and receiver, the carrier frequency offset, and the base station and the reference device. Carrier frequency.