201234804 六、發明說明： 【發明所屬之技術領域】 本發明大體係關於MIMQ通道估計，具體而言係關於— 種在圓0系統中利用空間相關性資訊來改良通道估計之 , Μ、相關聯之導頻資訊選擇方法及使用該通道估計方法 , 之用戶設備及使用該導頻資訊選擇方法之基地台。 【先前技術】 在當前之通道估計(CE)方案中，不同發射/接收天線對 其間的通道響應獨立地進行估計。然而，實際上，此等通 道響應之間具有相關性。此種相關性被稱作空間相關性， 可用於採用與時間相關性及頻率相關性類似之方式來改良 CE效能。然而，在現有〇£方案中，僅使用通道之時間相 關性及頻率相關性資訊，而未使用空間相關性資訊。 此外，在現有導頻設計中，所有基地台使用具有相同導 頻開銷之導頻圖案。然而，對於具有不同空間相關性之基 地台’可使用具有不同導頻開鎖之導頻圖案來提高⑶之有 效性。 【發明内容】 ' 本發明之目的在於使用ΜΙΜΟ系統之空間相關性資訊來 • 改良ΜΙΜΟ通道估计（CE)之效能’並使用對應之導頻設計 方法，δ亥導頻设叶方法根據MlM〇通道之空間相關性來調 適導頻開銷》 根據本發明之一態樣，提供一種利用與基地台之間的通 道之二間相關性來改良通道估計之用戶設備，戶斤述用戶設 160897.doc 201234804 備包括1頻信號接收單元，λ用於接收導頻信號；第一 估計單元，其基於所接收到之導頻信號，估計所述通道在 所述基地台處之空間相關性；第二估計單元，其基於所接 收到之導頻信號，估計所述通道在所述用戶設備處之空間 相關性；及第三估計單元，其基於所接收到之導頻信號、 所述通道在所述基地台處之空間相關性之估計及所述通道 在所述用戶設備處之空間相關性之估計，估計所述通道之 通道響應。 根據本發明之另一態樣’提供一種利用用戶設備與基地 台之間的通道之空間相關性來改良通道估計之方法其包 括以下步驟：接收導頻信號；基於所接收到之導頻信號， 估計所述通道在所述基地台處之空間相關性；基於所接收 到之導頻信號，估計所述通道在所述用戶設備處之空間相 關性；及基於所接收到之導頻信號、所述通道在所述基地 台處之空間相關性之估計及所述通道在所述用戶設備處之 空間相關性之估計，估計所述通道之通道響應。 根據本發明之另—態樣，提供-種基地台，其包括：導 頻圖案選擇早％，其根據所述基地台之通道環境及天線配 置來，擇導頻圖案；及發信號單元，其將由所述導頻圖案 選擇早7L選擇之導頻圖案發信號通知給用戶設備。 Μ 根據本發明之另一態樣’提供一種導頻資訊選擇方法， 其包括以下步驟：根據基地台之通道環境及天線配置來選 擇導頻圖案作為導頻資訊；及將所選擇之導頻圖案發信號 通知給用戶設備。 ； 160897.doc 201234804 本發明具有以下優勢：利用相同之導頻開銷能夠獲得顯 著之CE效能增益，或極大地減小導頻開銷而不會使CE效 月έ下降，及依賴於空間相關性之導頻設計策略能夠針對具 有不同空間相關性之ΜΙΜΟ系統，適應性地選擇適當之導 頻開銷，並在所有通道條件及環境下提供導頻開銷與通道 估計精度之間的良好取捨。 【實施方式】 藉由在下文結合附圖、僅作為實例對本發明之實施例進 行描述，將使本發明之上述及其他目的、特徵及優點變得 顯而易見。 根據本發明之實施例’在進行通道估計時，採用了 _種 聯合MMSE CE方案，其利用通道之空間相關性資訊，對 所有發射/接收天線對之通道係數進行聯合估計。然而， 應注意，對通道響應之估計不限於此種MMSE CE方案， 而亦可採用基於通道之空間相關性進行之其他方法。+办 田 ιΧ» 間相關性強時’該方案能夠顯著改良CE效能，或等效地， 減小導頻開銷。此外，效能增益隨著空間相關性而増大， 即’ ΜΙΜΟ系統所具有之空間相關性愈高，其能夠使用愈 少之導頻來實現良好之CE效能。由此，進一步需要提供一 種依賴於空間相關性之導頻設計策略，該導頻設計策略針 對具有不同空間相關性之ΜΙΜΟ系統使用不同導頻開銷。 在本文之後續部分將分別詳細描述聯合MMSE CE方案 及依賴於空間相關性之導頻設計策略。 現在，參照圖1所示之方塊圖來描述本發明之基地台 I60897.doc 201234804 10。為了簡明起見’此處僅展示了一個基地台，然而，應 注意，本發明之ΜΙΜΟ系統令具有多個基地台。 〜 在Μ細系統中，Μ_通道始終具有特定之㈣相關 性，即，不同發射/接收天線對上之通道響應係相關的。 實際上，空間相關性主要由以下兩個因素來判定：通道環 境，例如建築物密集之城市、空瞻之鄉村、視距⑽s)、 非視距（no LOS)等；及天線配置，例如天線數目、間距、 極化等等。一旦安置了基地台，此兩個因素即為固定的。 然而，對於不同之基地台，此兩個因素係不同的，由此不 同基地台之空間相關性亦不相同。 广展示根據本發明實施例之基地台1〇之示意方塊圖。 :地台可包括導頻圖案選擇單元iqi及發信號單元如。 基地σ 1G之導頻圖案選擇單元lQi根據該基地台1〇之 境及天線配置來選擇導頻圖案，其中，所選擇之導 頻圖案具有不同之導 之導頻開劫。例如，在建築物密集之城市 銷^頻開銷較小’而在空曠之鄉村環境中，導頻開 中:；在視距環境中，導頻開銷較小，而在非視距環境 :間：頻開銷較大。此外，例如，導頻開銷隨著天線數： 導頻圖=增大而增大。發信號翠元1〇2將由該基地台10之 ::圖㈣擇單元101選擇之導頻圖案發信號通 5又備。當基地台與用自 < 供、社， Γ (例如)自-基地a 信時’用戶設備可能 美地、 換至另一基地台。此時，所切換至之 土也C3 1 〇之發作雜tJ。- 送至用戶設備。”早疋將由該基地台10選擇之導頻圖案發 I60897.doc 201234804 在下文中，參照圖2所示之方塊圖來描述本發明之用戶 設備20。 圖2展示根據本發明實施例之用戶設備2〇之示意方塊 圖。用戶設備20可利用與基地台1 〇之通道之空間相關性資 訊來進行通道估計。用戶設備2〇可包括導頻信號接收單元 201導頻圖案接收單元202、基地台空間相關性估計單元 203、用戶設備空間相關性估計單元204、時間相關性估計 單元205、頻率相關性估計單元206及通道響應估計單元 207 ° 導頻信號接收單元201接收導頻信號。藉由通道接收之 導頻仏號中之雜訊可為加成性白高斯雜訊（AWGN)。導頻 圖案接收單元202可接收由根據本發明之基地台1〇發送之 所選導頻圖案，以進行同步。 為了對基地台1〇及用戶設備2〇之所有發射/接收天線對 上之通道響應進行估計（例如，本文後續部分詳細說明之 聯合MMSE通道估計），進一步需要對空間相關性/時間相 關性/頻率相關性進行估計。 於二間相關性資訊對於系統而言通常係未知的，因而 應首先對此種資訊進行估計。假定基地台1G之每根天線發 射之導頻之數目相等。基於由導頻信號接收單元1接收 到之導頻化號’基地台空間相關性估計單元203及用戶設 備工間相關性估計單元2〇4分別可對基地台10處不同天線 〜間的工間相關性及用戶設備20處不同天線之間的空間相 關性進行估# 160897.doc 201234804 硬仃估计，其中，好㈣(切為基地 台H)處之第m個發射天線與用戶設備轉之第n個接收天線 之間的在第t個OFDM符號中第k個子載波上之頻域通道響 應。 接著，時間相關性估計單元2G5及頻率相關性估計單元 206可使用本領域公知之傳統方法來對通道之時^目關性 公(Δ) = Ε(//(Κ/)//㈣(々 + △，〇")值進行估計。 最後，通道響應估計單元2〇7基於所接收到之導頻信 號、所估計出之時間相關性及頻率相關性、基地台1〇處不 同天線之間的空間相關性以及用戶設備2〇處不同天線之間 的空間相關性，對ΜΙΜΟ通道之通道響應進行估計，例 如’進行如下所述之聯合MMSE估計。 較佳地，通道響應估計單元2〇7亦包括第一相關性矩陣 估計單元208、第二相關性矩陣估計單元2〇9及通道響應最 終估計單元210，為了簡明起見，此三個單元2〇8、2〇9及 210均未在圓中展示。 第一相關性矩陣估計單元208可基於所估計出之基地台 1〇處不同天線之間的空間相關性、用戶設備2〇處不同天線 之間的空間相關性、時間相關性及頻率相關性，對如以下 對聯合MMSE CE之詳細說明中詳述之相關性矩陣Λφ進行 估計，該相關性矩陣心表示資料子載波上之通道響應與導 頻子載波上之通道響應之間的相關性矩陣。 第二相關性矩陣估計單元2 〇 9可基於所估計出之基地台 160897.doc 201234804 10處不同天線之間的空間相關性、用戶設備20處不同天線 之間的空間相關性、時間相關性及頻率相關性，對如以下 對聯合MMSE CE之詳細說明中詳述之相關性矩陣進行估 計’該相關性矩陣、表示導頻子載波上之通道響應之相關 性矩陣。 通道響應最終估計單元210可基於所估計出之資料子載 波上之通道響應與導頻子載波上之通道響應之間的相關性 矩陣忍及所估計出之導頻子載波上之通道響應之相關性矩 陣 < ’對通道響應進行估計。 圖3展示根據本發明實施例之基地台所使用之導頻資π 選擇方法300之流程圖。本發明需要針對不同環境中之具 有不同天線配置之ΜΙΜΟ系統而使用具有不同開銷之導頻 圖案。為此，提出了依賴於空間相關性之導頻資訊選擇方 法。在步驟S301中，每一基地台根據對其空間相關性產生 影響之其通道環境及天線配置來選擇導頻圖案。導頻開銷 可在如以下圖5八及圖⑶所示之導頻圖案中看出。在步驟 S302中，向用戶設備發信號通知所選擇之導頻圖案。 圖4展示根據本發明實施例之用戶設備所使用之通道估 計方法400之流程圖。在步驟S4〇1中，自基地台接收導頻 信號。接著，在步驟84〇2中，基於所接收到之導頻信號， 對基地台處不同天線之間的空間相關性進行估計。在步驟 S403中，基於所接收到之導頻信號，對用戶設備處不同天 線之間的空間相關性進行估計。接著，在步驟S404中，使 用本領域公知之傳統方法來對通道之時間相關性及頻率相 160897.doc 201234804 關性進行估計。最後，在步驟咖中，基於所接收到 頻信號、所估計之時間相關性及頻率相關性、基地台處不 同天線之間的空間相關性以及用戶設備處不同天線：：的 空間相關性，對麵〇通道之通道響應進行估計，例如， 進行如下所述之聯合MMSE估計。 較佳地，可將步驟S4〇5劃分為子步驟S405」、S4〇5_2及 S405-3。為了簡明起見，在圓中未展示此等子步驟。 在子步驟S405-WS405.2中，基於所估計出之基地台處 不同天線之間的空間相關性、用戶設備處不同天線之間的 空間相關’性、時間相關性及頻率相關性，分別對如以下對 聯合MMSE CE之詳細說明中詳述的、資料子載波上之通 道響應與導頻子載波上之通道響應之間的相關性矩陣〜及 導頻子載波上之通道響應之相關性矩陣、進行估計。在子 步驟S405-3中，基於所估計出之夂及<，對通道響應進行 估計。 在下文中，首先詳細論述聯合MMSE CE方案之實現， 接著詳細論述依賴於空間相關性之導頻設計策略，從而更 清楚地理解上述各步驟之相互關係及具體計算方式。201234804 VI. Description of the Invention: [Technical Fields of the Invention] The large system of the present invention relates to the estimation of MIMQ channels, in particular to the use of spatial correlation information in the circle 0 system to improve channel estimation, 相关, associated A pilot information selection method and a user equipment using the channel estimation method, and a base station using the pilot information selection method. [Prior Art] In the current channel estimation (CE) scheme, different transmit/receive antennas independently estimate the channel response therebetween. However, in reality, there is a correlation between these channel responses. This correlation, known as spatial correlation, can be used to improve CE performance in a manner similar to time correlation and frequency correlation. However, in the existing scheme, only the time correlation and frequency correlation information of the channel are used, and the spatial correlation information is not used. Furthermore, in existing pilot designs, all base stations use pilot patterns with the same pilot overhead. However, for platforms with different spatial correlations, pilot patterns with different pilot unlocking can be used to increase the effectiveness of (3). SUMMARY OF THE INVENTION The purpose of the present invention is to improve the performance of the channel estimation (CE) using the spatial correlation information of the chirp system and to use the corresponding pilot design method, and the delta pilot method is based on the MlM channel. The spatial correlation adjusts the pilot overhead. According to an aspect of the present invention, a user equipment for improving channel estimation by using two correlations with a channel between a base station is provided, and the user is set to 160897.doc 201234804 a first frequency signal receiving unit, λ for receiving a pilot signal, and a first estimating unit that estimates a spatial correlation of the channel at the base station based on the received pilot signal; a second estimating unit Estimating a spatial correlation of the channel at the user equipment based on the received pilot signal; and a third estimating unit that is based on the received pilot signal, the channel being at the base station Estimating the channel response of the channel by estimating an estimate of the spatial correlation and an estimate of the spatial correlation of the channel at the user equipment. According to another aspect of the present invention, a method for improving channel estimation by utilizing spatial correlation of a channel between a user equipment and a base station includes the steps of: receiving a pilot signal; based on the received pilot signal, Estimating a spatial correlation of the channel at the base station; estimating a spatial correlation of the channel at the user equipment based on the received pilot signal; and based on the received pilot signal, Estimating the spatial correlation of the channel at the base station and an estimate of the spatial correlation of the channel at the user equipment, estimating the channel response of the channel. According to another aspect of the present invention, a base station is provided, comprising: a pilot pattern selection earlier, which selects a pilot pattern according to a channel environment and an antenna configuration of the base station; and a signaling unit, The pilot pattern selected by the pilot pattern selection early 7L is signaled to the user equipment. According to another aspect of the present invention, a method for selecting a pilot information is provided, which includes the steps of: selecting a pilot pattern as pilot information according to a channel environment and an antenna configuration of a base station; and selecting the selected pilot pattern Signal the user device. 160897.doc 201234804 The present invention has the advantage of achieving significant CE performance gains with the same pilot overhead, or greatly reducing pilot overhead without degrading CE efficiency, and relying on spatial correlation The pilot design strategy can adaptively select the appropriate pilot overhead for a system with different spatial correlations and provide a good trade-off between pilot overhead and channel estimation accuracy under all channel conditions and environments. The above and other objects, features and advantages of the present invention will become apparent from the embodiments of the invention. In accordance with an embodiment of the present invention, when performing channel estimation, a joint MMSE CE scheme is employed, which uses the spatial correlation information of the channel to jointly estimate the channel coefficients of all transmit/receive antenna pairs. However, it should be noted that the estimation of the channel response is not limited to such an MMSE CE scheme, but other methods based on the spatial correlation of the channels may also be employed. +Doing the field ιΧ» When the correlation is strong, the scheme can significantly improve the CE performance, or equivalently, reduce the pilot overhead. In addition, the performance gain increases with spatial correlation, that is, the higher the spatial correlation of the ΜΙΜΟ system, the less the pilot can be used to achieve good CE performance. Thus, there is a further need to provide a pilot design strategy that relies on spatial correlation, which uses different pilot overhead for systems with different spatial correlations. The joint MMSE CE scheme and the pilot design strategy relying on spatial correlation will be described in detail later in this paper. Now, the base station I60897.doc 201234804 10 of the present invention will be described with reference to the block diagram shown in FIG. For the sake of brevity, only one base station is shown here, however, it should be noted that the system of the present invention has a plurality of base stations. ~ In a thin system, the Μ_channel always has a specific (four) correlation, that is, the channel response on the different transmit/receive antenna pairs is related. In fact, spatial correlation is mainly determined by two factors: the channel environment, such as densely populated cities, open-air villages, line-of-sight (10) s), non-line-of-sight (no LOS), etc.; and antenna configurations, such as antennas. Number, spacing, polarization, etc. Once the base station is placed, these two factors are fixed. However, for different base stations, these two factors are different, and thus the spatial correlation between different base stations is also different. A schematic block diagram of a base station 1 according to an embodiment of the present invention is widely shown. The ground station may include a pilot pattern selecting unit iqi and a signaling unit such as. The pilot pattern selecting unit lQi of the base σ 1G selects a pilot pattern according to the base station 1 and the antenna configuration, wherein the selected pilot pattern has different guided pilot robbing. For example, in a densely populated city, the frequency of transmission is small. In an open rural environment, the pilot is open: in the line-of-sight environment, the pilot overhead is small, while in the non-line-of-sight environment: The frequency overhead is large. Further, for example, the pilot overhead increases as the number of antennas: pilot map = increases. The signal Cuiyuan 1〇2 will be signaled by the pilot pattern selected by the base station 101 of the base station 10 (4). When the base station is used with <supply, agency, Γ (for example) self-base a letter, the user equipment may be beautifully transferred to another base station. At this time, the soil that is switched to is also C3 1 发作. - Send to user equipment. The pilot pattern selected by the base station 10 is issued I60897.doc 201234804. Hereinafter, the user equipment 20 of the present invention will be described with reference to the block diagram shown in Fig. 2. Fig. 2 shows a user equipment 2 according to an embodiment of the present invention. A schematic block diagram of the user equipment 20 can perform channel estimation by using spatial correlation information with the channel of the base station 1. The user equipment 2 can include a pilot signal receiving unit 201, a pilot pattern receiving unit 202, and a base station space. The correlation estimating unit 203, the user equipment spatial correlation estimating unit 204, the temporal correlation estimating unit 205, the frequency correlation estimating unit 206, and the channel response estimating unit 207 ° the pilot signal receiving unit 201 receives the pilot signal. The noise in the pilot nickname may be an additive white Gaussian noise (AWGN). The pilot pattern receiving unit 202 may receive the selected pilot pattern transmitted by the base station 1 according to the present invention for synchronization. In order to estimate the channel response on all transmit/receive antenna pairs of base station 1 and user equipment 2 (for example, the subsequent part of this article details The joint MMSE channel estimation) further requires the estimation of spatial correlation/time correlation/frequency correlation. The two correlation information is usually unknown to the system, so this information should be estimated first. The number of pilots transmitted by each antenna of the base station 1G is equal. Based on the pilot number received by the pilot signal receiving unit 1 'base station spatial correlation estimating unit 203 and the user equipment inter-process correlation estimating unit 2〇 4 respectively, the inter-machine correlation between different antennas at the base station 10 and the spatial correlation between different antennas of the user equipment 20 can be estimated. #160897.doc 201234804 Hard estimate, among them, good (four) (cut to base station The frequency domain channel response on the kth subcarrier in the tth OFDM symbol between the mth transmit antenna and the nth receive antenna of the user equipment. Next, the time correlation estimation unit 2G5 and the frequency Correlation estimation unit 206 may estimate the time of the channel (Δ) = Ε (/ / (Κ /) / / (4) (々 + △, 〇 ") using conventional methods known in the art. The channel response estimating unit 2〇7 is based on the received pilot signal, the estimated time correlation and frequency correlation, the spatial correlation between different antennas at the base station 1〇, and the different antennas of the user equipment 2〇 The spatial correlation between the channels determines the channel response of the channel, for example, 'to perform the joint MMSE estimation as described below. Preferably, the channel response estimating unit 2〇7 also includes the first correlation matrix estimating unit 208, the second The correlation matrix estimation unit 2〇9 and the channel response final estimation unit 210 are not shown in the circle for the sake of brevity. The first correlation matrix estimation unit 208 can be based on the estimated spatial correlation between different antennas at the base station 1 , the spatial correlation between different antennas at the user equipment 2 , the temporal correlation, and the frequency correlation. The correlation matrix Λ φ detailed in the detailed description of the joint MMSE CE is shown below, which represents the correlation matrix between the channel response on the data subcarrier and the channel response on the pilot subcarrier. The second correlation matrix estimation unit 2 〇9 may be based on the spatial correlation between different antennas at the estimated base station 160897.doc 201234804 10, the spatial correlation between different antennas at the user equipment 20, time correlation, and The frequency correlation is estimated by correlating the correlation matrix detailed in the detailed description of the joint MMSE CE as follows, which is a correlation matrix representing the channel response on the pilot subcarriers. Channel response final estimation unit 210 may tolerate the correlation of channel responses on the estimated pilot subcarriers based on a correlation matrix between the channel response on the estimated data subcarriers and the channel response on the pilot subcarriers. The sex matrix < 'estimates the channel response. 3 shows a flow diagram of a pilot π selection method 300 used by a base station in accordance with an embodiment of the present invention. The present invention requires the use of pilot patterns with different overhead for systems with different antenna configurations in different environments. To this end, a pilot information selection method that relies on spatial correlation is proposed. In step S301, each base station selects a pilot pattern based on its channel environment and antenna configuration that affect its spatial correlation. The pilot overhead can be seen in the pilot pattern as shown in Figure 5-8 and Figure (3) below. In step S302, the selected pilot pattern is signaled to the user equipment. 4 shows a flow diagram of a channel estimation method 400 used by a user equipment in accordance with an embodiment of the present invention. In step S4〇1, a pilot signal is received from the base station. Next, in step 84〇2, the spatial correlation between different antennas at the base station is estimated based on the received pilot signals. In step S403, a spatial correlation between different antennas at the user equipment is estimated based on the received pilot signals. Next, in step S404, the time correlation of the channel and the frequency phase are estimated using conventional methods known in the art. Finally, in the step coffee, based on the received frequency signal, the estimated time correlation and frequency correlation, the spatial correlation between different antennas at the base station, and the spatial correlation of different antennas: at the user equipment, opposite The channel response of the channel is estimated, for example, by performing a joint MMSE estimation as described below. Preferably, step S4 〇 5 can be divided into sub-steps S405", S4 〇 5_2 and S405-3. For the sake of brevity, these substeps are not shown in the circle. In sub-steps S405-WS405.2, based on the estimated spatial correlation between different antennas at the base station, the spatial correlation between the different antennas at the user equipment, time correlation, and frequency correlation, respectively The correlation matrix between the channel response on the data subcarrier and the channel response on the pilot subcarrier, and the channel response on the pilot subcarrier, as detailed in the detailed description of the joint MMSE CE, as follows. And make an estimate. In sub-step S405-3, the channel response is estimated based on the estimated 夂 and <. In the following, the implementation of the joint MMSE CE scheme will be discussed in detail first, followed by a detailed discussion of the pilot design strategy relying on spatial correlation to more clearly understand the interrelationships and specific calculation methods of the above steps.
聯合MMSE CE 考慮在發射器（如本文中之基地台1 〇 1)處具有W個天線 且在接收器（如本文中之終端機丨〇2)處具有馬個天線之 MIMO-OFDM系統。圖5A及圖5B為展示針對具有〜=4個發 射天線之ΜΙΜΟ系統而使用不同開銷之導頻圖案之示意 圖。如圖所示’在由A：rf個子載波及尸個OFDM符號構成之 160897.doc •10· 201234804 指定無線資源區塊上均勻插入導頻信號。同樣如圖所示， 以正交之方式對來自不同發射天線之導頻進行多工β藉由 在導頻子載波處之樣本之間進行内插來估計資料子載波上 之通道響應。可使用時間相關性/頻率相關性/空間相關性 資訊，經由例如MMSE方案來改良内插效能。 令/為指定之無線資源區塊中自第111個發射天 線發射之導頻之數目，〜P(OT)}為其子載波索引， ^，Ρ=ι~ρ(Λ)}為其OFDM符號索引，〜/>«}為導頻之值。 在第η個接收天線處接收之導頻的有雜訊版本為：The joint MMSE CE considers a MIMO-OFDM system with W antennas at the transmitter (e.g., base station 1 〇 1) and a horse antenna at the receiver (e.g., terminal 丨〇 2 herein). 5A and 5B are schematic diagrams showing pilot patterns using different overhead for a chirp system having ~=4 transmit antennas. As shown in the figure, the pilot signal is uniformly inserted on the designated radio resource block by A:rf subcarriers and corpses of OFDM symbols. As also shown, the pilots from different transmit antennas are multiplexed in an orthogonal manner by estimating the channel response on the data subcarriers by interpolating between samples at the pilot subcarriers. Interpolation performance can be improved via, for example, an MMSE scheme using time correlation/frequency correlation/spatial correlation information. Let / be the number of pilots transmitted from the 111th transmit antenna in the specified radio resource block, ~P(OT)} is its subcarrier index, ^, Ρ=ι~ρ(Λ)} for its OFDM symbol The index, ~/>«} is the value of the pilot. The noisy version of the pilot received at the nth receive antenna is:
0 其中’ 為自第m個發射天線發射之、在第n個 接收天線處接收之導頻之有雜訊版本，丑(”，m)(it，0為第m個發 射天線與第η個接收天線之間的在第t個OFDM符號中第让個 子載波上之頻域通道響應’ /Ή").·.#,]7·為在第瓜個發射天 線處發射之導頻向量，"―5中丨1^…"^]7·為均值為〇、方差為 σ2之加成性高斯白雜訊（AWGN)，其方差可由終端機估計 獲知。將每一 4n_ra)除以對應之導頻信號，得到： y (2) 其中，产，其中^，七#—/<)，並且， 〜[々'吹·.#；^，其中。利用丑?，°來表示第m個 發射天線與第η個接收天線之間在導頻子載波處之頻域通 道響應，即： 160897.doc -11· 201234804 开广=[妒，丨丨(，·，，p]r S玄方案之目的為針對所有（„，所）對，對給定之無線資源 區塊内之所有子載波處之頻域通道響應進行估計，即： 定義 严.Wr)rf、 m P P P . 丑</=1^(’把外)7.../^’|)7'...的_1’則聯合]^]\48£〇£可實現為： ~^άρ{βρρ f pfx y (3) 其中P-E匕）/σ為導頻之信雜比（SNR)，及办且 〜=Ε(//Λ") ’其中上標11表示共軛轉置。之物 理含義為資料子載波上之通道響應與導頻子載波上之通道 響應之間的相關性矩陣，之物理含義為導頻子 載波上之通道響應之相關性矩陣。 因此，自方程式（3)可看出，為了對所有子载波處之 道響應進行估計，必須首先對未知之从、進行估叶。 下將論述對相關性矩陣~及〜之估計， S405-1 及 S405-2。 迎千艾 定義 r, (Δ) = E(H^a) (k,i+Af) (Δ)=E(// (Μ·™) (k,i)H(Mm) (k+A,i)H) rJu(n,n') = E(H{nm)(k,〇H(n'm)(k,i)H) 160897.doc •12- 201234804 其中，〃’、◊、〜及〜分別表示時間相關性、頻率相關性、 接收器側之空間相關性及發射器側之空間相關性。利用 、讣：）、„〆〇及〜(0來表示心中之第丨個元素之子載波、符 號、接收天線及發射天線之索引。由表示之、〜之第 (Gy·)元素可計算如下： (4) 類似地 ~之第（z·，y)元素可計算如下： (5) =n(tpU)-td(i))rf(kp(j)-kd(i))riix(np(j),nd(iy)rTx(m灿⑻ 由於相關性統計資料對於系統而言係未知的’因此需要 在通道估計之前對相關性統計資料進行估計。可使用如下 傳統方式來估計時域及頻域相關性。 ；,(δ)=ΙΜ^)Αο><,， 6 ⑼…;//(-1)) ! · t ♦ + ；7(〇)0 where ' is the noise version of the pilot received from the mth transmit antenna and received at the nth receive antenna, ugly (", m) (it, 0 is the mth transmit antenna and the nth The frequency domain channel response on the first subcarrier in the t-th OFDM symbol between the receiving antennas ' /Ή").·.#,]7· is the pilot vector transmitted at the first transmitting antenna, " ; ―5中丨1^..."^]7· is an additive Gaussian white noise (AWGN) with mean 〇 and variance σ2, the variance of which can be estimated by the terminal. Divide each 4n_ra) The pilot signal is obtained as: y (2) where, the production, where ^, seven #—/<), and ~[々' blowing·.#;^, where.Using ugly, ° to indicate the mth The frequency domain channel response between the transmit antenna and the nth receive antenna at the pilot subcarrier, ie: 160897.doc -11· 201234804 Kai Guang = [妒,丨丨(,·,,,p]r S Xuan The purpose of the scheme is to estimate the frequency domain channel response at all subcarriers within a given radio resource block for all pairs, ie: Definition strict. Wr) rf, m PPP . ugly </ =1^( The outer _7.../^'|)7'...the _1' is combined]^]\48£〇£ can be realized as: ~^άρ{βρρ f pfx y (3) where PE匕) /σ is the signal-to-noise ratio (SNR) of the pilot, and ~=Ε(//Λ") 'where the superscript 11 indicates the conjugate transpose. The physical meaning is the correlation matrix between the channel response on the data subcarrier and the channel response on the pilot subcarrier, and the physical meaning is the correlation matrix of the channel response on the pilot subcarrier. Therefore, as can be seen from equation (3), in order to estimate the channel response at all subcarriers, the unknown must be evaluated first. The estimation of the correlation matrix ~ and ~, S405-1 and S405-2, will be discussed below.千千艾为 r, (Δ) = E(H^a) (k,i+Af) (Δ)=E(// (Μ·TM) (k,i)H(Mm) (k+A, i)H) rJu(n,n') = E(H{nm)(k,〇H(n'm)(k,i)H) 160897.doc •12- 201234804 where 〃', ◊,~ And ~ represent time correlation, frequency correlation, spatial correlation on the receiver side, and spatial correlation on the transmitter side, respectively. Use , 讣:), 〆〇 and ~ (0 to represent the index of the subcarrier, symbol, receiving antenna and transmitting antenna of the third element in the heart. The element (Gy·) of the representation can be calculated as follows: (4) Similarly, the (z·,y) element can be calculated as follows: (5) =n(tpU)-td(i))rf(kp(j)-kd(i))riix(np(j ), nd(iy)rTx(m灿(8) Since the correlation statistics are unknown to the system', it is necessary to estimate the correlation statistics before the channel estimation. The following traditional methods can be used to estimate the time domain and the frequency domain. Relevance. ;,(δ)=ΙΜ^)Αο><,, 6 (9)...;//(-1)) ! · t ♦ + ;7(〇)
-FhDF (6) ⑺ 其中’〜=2以，心為OFDM符號之長度，/c/=v/c/c為且有速 頻率，Λ為載頻，且1光速， /+卜P^2l|，尺為〇FDM符號中子栽波之數目， l/fv^vl/Z,,〇,···,〇!· > L=\ WTmax L個元素 D = ^ll/I,---.1//.,0... ηΐ . γ_Γη/_ Ί +1 , j. 頻寬 ，、中妒為 rmax為最大延遲擴展。 根據如下之有雜訊導頻觀測結果來估 -^ _ T·"間域相關性 丨叹&對於Vm有Pw=P，則對〜及〜之估計如下， 160897.doc •13· 201234804 (8) (_V(nV”'>W)且 其中，y”)=|y(”.且 估計值卩，、6、/^及4即為上述估計步驟S4〇2、S403及 S404之結果。 基於方程式（6)至（8) ’聯合MMSE CE可實現為： (9) ^d-^dp{^pp+I/p) ^ 其中’在方程式（4)及（5)中分別代入各個估計值；，、；/、p& 及&來替換，，、◊、〜及s，導出 <及心，從而得到所有子 載波處之通道響應之估計值也。 依賴於空間相關性之導頻設計策略 所提出之聯合MMSE CE隨空間相關性之升高而增強， 此可自以下模擬結果中看出。此意味著MIM〇系統^具有 之空間相關性愈高，其需要使用之導頻信號愈少。實際 上’ ΜΙΜΟ系統之空間相關性主要由以下兩個因素來： 定：通道環境，如建築物密集之城市環境之鄉村環 境、LOS/非LOS等；及天線配置，如天線數目及間距等。 此需要針對不同環境中之具有不同天線配置之ΜΐΜΘ_ 使用具有不同開銷之導_。為此’提出了依賴於空間 相關性之導頻設計策略。 之鄉村 1極化） 依賴於空間相關性之導頻設計策略包括以下程序 •藉由針對通道環境（如建築物密集之城市環境/空瞻 環境、副非LOS)及天線配置(如天線數目、間距 之每種組合而進行模擬，判定適當之導頻開銷。 160897.doc 201234804 •母一基地台根據其環境及天線配置來選擇導頻圖案。 •每一基地台向其終端機發信號通知正在使用之導頻圖 案。 以下’使用數值結果來印證本發明之技術之優勢。 考慮在基地台處有#r=4個天線且在每一終端機處有％=2 個天線之MIMO-OFDM系統。使用3GPP空間通道模型 (SCM)。考慮具有不同空間相關性之以下兩種通道情形： •情形1 :城市小型小區，LOS，天線間距在BS及終端機 處均為0.5個波長； •情形2 :城市巨型小區，非l〇S，天線間距在BS處為4 個波長’在終端機處為〇.5個波長。 在以下方程式（10)及（11)中，針對此兩種情形在BS及終 端機處均給出藉由模擬導出之空間相關性矩陣。容易發 現’情形1具有相對較強之空間相關性，情形2之空間相關 性要弱很多。 情形1之空間相關性矩陣為： RT„~ 1 0.9597 0.8615 0.7552 0.9597 1 0.9597 0.8615 0.8615 0.9597 1 0.9597 0.7522 0.8615 0.9597 1 1 0.591" 0.591 1 (10) 情形2之空間相關性矩陣為： 1 0.39690.2272 0.1515 〇 _ 0.3969 1 0.3969 0.2272 Tx~ 0.2272 0.3969 1 0.3969 0.1515 0.2272 0.3969 1 且Λ-FhDF (6) (7) where '~=2, the heart is the length of the OFDM symbol, /c/=v/c/c is the fast frequency, Λ is the carrier frequency, and 1 speed of light, /+ Bu P^2l |, the ruler is the number of sub-carriers in the FDM symbol, l/fv^vl/Z,,〇,···,〇!· > L=\ WTmax L elements D = ^ll/I,-- -.1//.,0... ηΐ . γ_Γη/_ Ί +1 , j. The bandwidth, and the middle 妒 is rmax is the maximum delay spread. Estimate -^ _ T ·" inter-domain correlation sigh & for Pm=P for Vm, the estimates for ~ and ~ are as follows, 160897.doc •13· 201234804 (8) (_V(nV"'>W) and wherein y")=|y(". and the estimated values 卩, 6, 6, and 4 are the above-mentioned estimation steps S4〇2, S403, and S404 Results. Based on equations (6) to (8) 'joint MMSE CE can be implemented as: (9) ^d-^dp{^pp+I/p) ^ where 'substituting in equations (4) and (5) respectively The respective estimated values; , , ; / , p & and & replace, , , ◊, ~ and s, derive < and heart, thereby obtaining an estimate of the channel response at all subcarriers. Depends on spatial correlation The joint MMSE CE proposed by the pilot design strategy is enhanced with the increase of spatial correlation, which can be seen from the following simulation results. This means that the MIM〇 system^ has a higher spatial correlation, which needs to be used. The less the pilot signal is. In fact, the spatial correlation of the 'ΜΙΜΟ system is mainly due to the following two factors: Ding: channel environment, such as the rural ring of densely populated urban environment , LOS / non-LOS, etc.; and antenna configuration, such as the number and spacing of antennas, etc. This needs to be used for different antenna configurations in different environments _ using different metrics. For this reason, it is dependent on spatial correlation. Pilot design strategy. Village 1 polarization) Pilot design strategies that rely on spatial correlation include the following procedures • by targeting channel environments (eg, densely populated urban environments/airborne environments, secondary non-LOS) and antenna configurations (Estimate, such as the combination of the number of antennas and the spacing, to determine the appropriate pilot overhead. 160897.doc 201234804 • The mother-base station selects the pilot pattern according to its environment and antenna configuration. • Each base station to its terminal The machine signals the pilot pattern being used. The following 'use numerical results to demonstrate the advantages of the technique of the present invention. Consider having #r=4 antennas at the base station and %=2 antennas at each terminal MIMO-OFDM system. Use 3GPP Spatial Channel Model (SCM). Consider the following two channel scenarios with different spatial correlations: • Case 1: Urban Small Cell, LOS The antenna spacing is 0.5 wavelengths at both the BS and the terminal; • Case 2: Urban giant cell, non-l〇S, antenna spacing is 4 wavelengths at the BS' at the terminal. 55 wavelengths. In the following equations (10) and (11), the spatial correlation matrix derived by simulation is given for both cases at the BS and the terminal. It is easy to find that 'Scenario 1 has a relatively strong spatial correlation, and the situation The spatial correlation of 2 is much weaker. The spatial correlation matrix of case 1 is: RT „~ 1 0.9597 0.8615 0.7552 0.9597 1 0.9597 0.8615 0.8615 0.9597 1 0.9597 0.7522 0.8615 0.9597 1 1 0.591" 0.591 1 (10) Space for situation 2 The correlation matrix is: 1 0.39690.2272 0.1515 〇_ 0.3969 1 0.3969 0.2272 Tx~ 0.2272 0.3969 1 0.3969 0.1515 0.2272 0.3969 1 and Λ
Rx ' 1 0.0836 0.0836 1 (11) 如圖5A及圖5B所示’在模擬中使用了具有不同開銷之 兩個導頻圖案。圖6A及圖6B在兩種情形下比較了本發明 提出之聯合MMSE通道估計器與傳統之MMSE通道估計器 160897.doc 201234804 之均方誤差（MSE)。針對聯合MMSE通道估計器，使用了 以下兩個導頻圖索： 聯合MMSE-1 :使用圖5A中之導頻圖案a ; 聯合MMSE-2 :使用圖5B中之導頻圖案b，僅具有圖a中 開銷之一半開銷。 針對傳統MMSE通道估計器，始終使用圖5 A中之導頻圖 案A。自該圖中可看出，在圖6A所示之情形丨中聯合 MMSE通道估計器可實現與傳統MMSE通道估計器類似之 效能。當空間相關性高時，可顯著減小導頻開銷。當空間 相關I·生低時，如在圖6B所示之情形2中，聯合mmse及傳 、’克MMSE通道估计器具有相似之效能，且需要相似之導頻 開銷此種繞測結果指示：應根據通道之空間相關性統計 來調整導頻開銷’以便在所有環境中提供導頻開銷與通道 估什精度之間的最佳取拾。 ’然而’應理解，在不脫 ’熟習此項技術者能夠對 。本發明之範嘴僅由所附 參照上述實施例描述了本發明 離本發明之精神及範疇之情況下 本發明之實施例進行修改及變更 申請專利範圍來限定。 【圖式簡單說明】 圖1展示根據本發明實施例之基地台之示意方塊圖； 圖2展示根據本發明實施例之用戶設備之示意方塊圖； 圖3展示根據本發明實施例之基地台所使用之導頻資士 選擇方法之流程圖； 圖4展示根據本發明實施例之用戶設備所使用之通道估 160897.doc -16 · 201234804 計方法之流程圖； 圖5A及圖5B為展示針對i古 .^ ή Τ對具有~=4個發射天線之ΜΙΜΟ系 統而使用不同開銷之導頻圖案之示意圖；及 ，圖6Α及圖6Β為展示在相同之導頻開銷及減半之導頻開 銷之情況下’傳統画SE_CE與聯合M_ CE之間的比較 之示意圖。 【主要元件符號說明】 基地台 20 101 102 201 202 203 204 205 206 207 用戶設備 導頻圖案選擇單元 發信號單元 導頻信號接收單元 導頻圖案接收單元 基地台空間相關性估計單元 用戶設備空間相關性估計單元 時間相關性估計單元 頻率相關性估計單元 通道響應估計單元 160897.docRx ' 1 0.0836 0.0836 1 (11) As shown in Figs. 5A and 5B, two pilot patterns having different overheads were used in the simulation. 6A and 6B compare the mean squared error (MSE) of the combined MMSE channel estimator and the conventional MMSE channel estimator 160897.doc 201234804 proposed by the present invention in two cases. For the joint MMSE channel estimator, the following two pilot maps are used: joint MMSE-1: use pilot pattern a in Figure 5A; joint MMSE-2: use pilot pattern b in Figure 5B, with only graph One of the overheads in a. For the traditional MMSE channel estimator, the pilot pattern A in Figure 5A is always used. As can be seen from this figure, the joint MMSE channel estimator in the situation shown in Figure 6A can achieve similar performance to the traditional MMSE channel estimator. When the spatial correlation is high, the pilot overhead can be significantly reduced. When the spatial correlation I is low, as in the case 2 shown in Fig. 6B, the joint mmse and the gram- MMSE channel estimator have similar performance, and similar pilot overhead is required. The pilot overhead should be adjusted based on the spatial correlation statistics of the channels to provide optimal picking between pilot overhead and channel estimation accuracy in all environments. 'However, it should be understood that those who are familiar with this technology can do it right. The present invention is defined by the appended claims. The invention is defined by the scope of the invention and the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a schematic block diagram of a base station according to an embodiment of the present invention; FIG. 2 shows a schematic block diagram of a user equipment according to an embodiment of the present invention; FIG. 3 shows a base station used according to an embodiment of the present invention. FIG. 4 is a flow chart showing a method for estimating a channel used by a user equipment according to an embodiment of the present invention; FIG. 5A and FIG. 5B are diagrams showing an .^ 示意图 示意图 Schematic diagram of pilot patterns with different overhead for a system with ~=4 transmit antennas; and, Figure 6Α and Figure 6Β show the same pilot overhead and halved pilot overhead A schematic diagram of the comparison between the traditional painting SE_CE and the joint M_CE. [Description of main component symbols] Base station 20 101 102 201 202 203 204 205 206 207 User equipment pilot pattern selection unit Signaling unit Pilot signal receiving unit Pilot pattern receiving unit Base station spatial correlation estimation unit User equipment spatial correlation Estimation unit time correlation estimation unit frequency correlation estimation unit channel response estimation unit 160897.doc