JP5402385B2 - Subchannel selection method and apparatus and receiver using the apparatus - Google Patents

Description

  The present invention relates to adaptive transmission in an OFDM system, and more particularly to a calculation / selection method for acquiring an optimal subchannel when a closed-loop OFDM system performs adaptive transmission.

  With the increasing demand for higher bit rates in wireless communications, multi-carrier transmission technology has emerged, and multi-carrier transmission technology can be realized by OFDM (Orthogonal Frequency Division Multiplexing). it can. OFDM uses cyclic prefix to effectively eliminate multipath fading in wireless communications, and provides flat attenuation characteristics for a single subchannel, effectively eliminating interference between symbols. be able to. For example, OFDM is a wideband such as digital audio broadcasting (DAB), high-definition television broadcasting (HDTV), wireless local network standard (WLAN) based on IEEE802.11a, and wireless metro network standard (WMAN) based on IEEE802.16. Many wireless communication systems are applied.

  OFDMA (Orthogonal Frequency Division Multiple Access) is a multiple access technique often used in OFDM systems, where the entire band is divided into multiple subchannels and each subchannel has multiple subchannels. The carrier is included and the subchannel is the smallest resource allocation unit. OFDMA contributes to improving the spectral efficiency of the system and allows flexible allocation of resources to different users and traffic. For example, adaptive modulation and coding (AMC) techniques can be applied to OFDMA systems. In the AMC technique, parameters such as an optimal modulation and coding method and transmission power can be selected in accordance with an instantaneous change of a radio channel, so that data throughput in the link can be improved.

  AMC changes the modulation and coding method according to changes in channel information, but even if a subchannel with a good channel environment is selected and data is transmitted on the assumption that the modulation and coding method is not changed. Alternatively, the modulation / coding method and the corresponding resource allocation region (subchannel) may be changed simultaneously. AMC mainly has the following advantages: it enables users located in advantageous locations to obtain higher data rates, thereby improving the average cell throughput and reducing the user's channel environment. In this case, by selecting and transmitting a low data rate, the average throughput is lowered, but it is strong against interference, has good error correction performance, and can improve reliability when transmitting data.

  FIG. 1 is a block diagram conceptually showing a closed-loop OFDM system according to the prior art. As shown in FIG. 1, the closed-loop OFDM system includes a transmitter 100, a receiver 103, a channel estimation device 104, and a subchannel selection device 105. The receiver 103 receives a transmission signal mixed with noise 102 transmitted from the transmitter 100 via the channel 101. Channel estimation apparatus 104 estimates a channel from the pilot symbol sequence of the received transmission signal, that is, estimates the gain of each subcarrier of each subchannel. Next, subchannel selection apparatus 105 calculates the effective S / N ratio of each subchannel from the estimated gain of the subcarrier, and then selects the subchannel with the best S / N ratio. The number (subchannel number) is returned to the transmitter 100. The transmitter 100 transmits and transmits data based on the received reply information.

  It should be noted here that, for the sake of explanation, in FIG. 1 above, the channel estimator 104 and the subchannel selector 105 are shown as separate units from the receiver 103. Generally, it is configured as a part of 103.

  In a general AMC system, the transmitter transmits a known pilot symbol or learning sequence, and the channel estimation device 104 estimates and measures the channel based on the received pilot symbol or learning sequence.

  Next, the operation of the subchannel selection device 105 will be described.

  In the prior art, when the subchannel selection device 105 selects a subchannel, it is mainly performed based on a parameter such as an effective S / N ratio or an effective SINR. In the following description, the effective S / N ratio or the effective SINR is collectively referred to as an effective S / N ratio and is expressed by ESINR.

  The effective S / N ratio of the subchannel is calculated from the S / N ratio (or channel gain) of the subcarriers in all subcarriers included in this subchannel, and the additive white Gaussian noise channel (AWGN ) Reflects the equivalent S / N ratio of subcarriers. The higher the effective S / N ratio, the better the channel environment for this subchannel.

ここで、γはS/N比、チャネル利得ｈは複素で、σ²はノイズパワーである。一般の通信システムでは、1回の受信操作中において、ベースバンドデータのノイズパワーは一定の数値であり、そのため、S/N比とチャネル利得のノルム（norm）とは正比例関係を有する。 The relationship between the subcarrier S / N ratio and the channel gain is shown as follows.

Here, γ is the S / N ratio, the channel gain h is complex, and σ ² is the noise power. In a general communication system, the noise power of baseband data is a constant value during one reception operation, and therefore, the S / N ratio and the channel gain norm have a direct proportional relationship.

ここで、βは変調方法に関する係数、

はi番目のサブキャリアのS/N比で、Nはこのサブチャネルにおけるサブキャリア数である。チャネル推定装置104はサブキャリア利得の集合{h_i}を出力したため、サブチャネル選択装置105は式（1）、（2）により現在のサブチャネルの有効S/N比を算出できる。 EESM (Exponential Effective SINR Mapping) and RBIR (Received Bit Information Rate) are methods for calculating the effective S / N ratio of subchannels based on the S / N ratio of each subcarrier. Information rate) method. EESM mainly uses the exponential function approach shown in the following equation (2) by mapping SINRs in a plurality of carriers to effective values by β values.

Where β is a coefficient related to the modulation method,

Is the S / N ratio of the i-th subcarrier, and N is the number of subcarriers in this subchannel. Since channel estimation apparatus 104 outputs a set {h _i } of subcarrier gains, subchannel selection apparatus 105 can calculate the effective S / N ratio of the current subchannel using equations (1) and (2).

ここで、

とm(i)はそれぞれi番目のサブキャリアのシンボル相互情報とビット数を示し、有効S/N比は、相互情報と対応付けられたテーブルから調べて得られるものである。 The RBIR method statistically calculates bit mutual information to calculate an effective S / N ratio.

here,

And m (i) indicate symbol mutual information and the number of bits of the i-th subcarrier, respectively, and the effective S / N ratio is obtained by examining from a table associated with the mutual information.

  Based on the channel gain of each subcarrier output from the channel estimation device 104, the subchannel selection device 105 calculates the effective S / N ratio of all the subchannels according to the equation (2) or (3), The subchannel with the largest effective S / N ratio is selected as the subchannel to be returned. Subchannel selection apparatus 105 selects a subchannel, and then transmits the subchannel number to transmitter 100.

  The following is a list of documents cited in the present disclosure, the contents of which are incorporated herein by reference, and are described in detail in the present disclosure.

  The closed-loop OFDM system selects a subchannel for transmitting data based on channel information and selects a modulation / coding method corresponding to the subchannel. In the prior art, when selecting a subchannel, the receiving side calculates the effective S / N ratio of each subchannel based on the result of channel estimation, selects the subchannel with the largest effective S / N ratio, and the information. To the sender. Accordingly, the processing becomes complicated, and the processing capability of the processing apparatus is highly required. Since AMC requires high channel measurement accuracy and a short time lag to ensure its performance, a simple and quick subchannel selection method is necessary for closed-loop OFDM systems.

US Patent Application Publication No. 2008 / 0043610A1 US Patent Application Publication No. 2006 / 0246916A1 US Patent Application Publication No. 2006 / 0083210A1 US Patent Application Publication No. 2005 / 0180354A1

IEEE P802.16e / D12. Draft IEEE standard for local and metropolitan area networks−Part 16: Air interface for fixed and mobile broadband wireless access systems. 2005 Draft IEEE 802.16m “evaluation methodology document,” IEEE. C802.16m−07 / 080r2, June, 2007

  Therefore, the present invention has been made in view of the above-described prior art, and is a subchannel applied to an OFDM system that can increase the speed when selecting a subchannel or can request a low processing capacity of hardware. A selection method and apparatus are provided.

  In order to achieve the above object, the present application provides the following inventions.

According to one embodiment, a subchannel selection apparatus that selects an appropriate subchannel from a plurality of subchannels having one or more subcarriers,
Worst subcarrier for determining S / N ratio of each subcarrier based on channel gain of each subcarrier of each of the plurality of subchannels, and determining worst subcarrier in each of the plurality of subchannels based on S / N ratio A determination means;
Based on the S / N ratio of the worst subcarrier in each subchannel determined by the worst subcarrier deciding unit, the S / N ratio of the worst subcarriers is highest, that is, the best worst subcarrier is determined. Comparing and selecting means for selecting a subchannel corresponding to the best worst subcarrier.

According to another embodiment, a subchannel selection method for selecting an appropriate subchannel from a plurality of subchannels having one or more subcarriers is as follows:
Worst subcarrier for determining S / N ratio of each subcarrier based on channel gain of each subcarrier of each of the plurality of subchannels, and determining worst subcarrier in each of the plurality of subchannels based on S / N ratio A decision step;
Based on the S / N ratio of the worst subcarrier in each subchannel determined in the worst subcarrier determination step, the worst S / N ratio among the worst subcarriers is determined, that is, the best worst subcarrier is determined. A comparison and selection step of selecting a subchannel corresponding to the best worst subcarrier.

  A receiver according to another embodiment has the above subchannel selection apparatus.

  The disclosed subchannel selection apparatus and subchannel selection method can increase the speed when selecting a subchannel or require a low processing capacity of hardware.

The drawings illustrate a preferred embodiment of the invention, form part of the specification, and are used to explain the embodiment in more detail in conjunction with the text description.
1 is a block diagram conceptually showing a closed-loop OFDM system according to the prior art. It is a figure which shows notionally subcarrier distribution and the structure of a subchannel in an OFDM system. It is a graph which shows distribution of the channel gain in an OFDM system. 1 is a block diagram conceptually illustrating an OFDM system to which a subchannel selection method and apparatus according to an embodiment can be applied. It is a block diagram which shows the structure of subchannel selection apparatus 105 'by one Embodiment. It is a block diagram which shows the structure of subchannel selection apparatus 105 'by another embodiment. It is a block diagram which shows the structure of subchannel selection apparatus 105 'by further another embodiment. It is a block diagram which shows the structure of subchannel selection apparatus 105 'by further another embodiment. 3 is a flowchart of a subchannel selection method according to an embodiment. 7 is a flowchart of a subchannel selection method according to another embodiment. 6 is a flowchart of a subchannel selection method according to still another embodiment.

  Hereinafter, a subchannel selection apparatus and method according to embodiments will be described with reference to the drawings.

  The present disclosure provides a simplified subchannel selection method that can obtain results similar to those of other algorithms by simply calculating and comparing channel gains of subcarriers.

  In the case of a single antenna system, the S / N ratio of the smallest subcarrier of each subchannel is compared, and the subchannel having the largest S / N ratio of the smallest subcarrier is selected and returned to the transmission side.

  In the case of a single transmission multi-reception (SIMO) system, after combining channel gains with a receiving antenna, a selection method similar to that for a single antenna is used.

  In the case of a multi-transmission single reception (MISO) system, a similar selection method is used after channel gain is combined in the transmission antenna.

  In the case of a multi-transmission multi-reception (MIMO) system, the selection of subchannels is determined by different transmission modes. In the transmission diversity mode, a selection method similar to MISO is used, while in the spatial division multiplexing modulation mode, each subcarrier is selected. A plurality of mixed channels are converted into several equivalent parallel channels, and after combining channel gains for each subcarrier, a selection method similar to that for a single antenna is used.

  Compared with a general effective S / N ratio calculation and subcarrier selection method, the selection method according to the present disclosure has a small calculation complexity and is easy to implement.

  In the following description, a closed-loop OFDM system is taken as an example, and a method and apparatus according to embodiments are described with reference to the drawings.

  The above and further aspects and features of the invention will become more apparent with reference to the following description and drawings. In the foregoing description and drawings, specific embodiments have been disclosed and specified in detail. It should be understood that the invention is not limited thereby in scope. Many changes, modifications and equivalents within the spirit and spirit of the appended claims are encompassed by the present invention.

  Many aspects of the invention can be better understood with reference to the following drawings. Elements in the drawings are not drawn to scale, but are only made to illustrate embodiments. Elements and components described in one drawing or embodiment of the disclosure may be combined with elements and components described in one or more other drawings or embodiments. Moreover, in the drawings, like numerals indicate corresponding elements in the several drawings, and may indicate corresponding elements described in one or more embodiments. Furthermore, for the sake of brevity of description and simplification of the drawing, the drawings do not show other elements that should be present that are well known to those skilled in the art.

  First, an embodiment of a subchannel selection method and apparatus will be described.

  FIG. 2 conceptually shows a subcarrier distribution and subchannel configuration in an OFDM system. As shown in FIG. 2, the frequency band of the entire channel is divided into a data part, a pilot symbol part, and a dummy carrier part. The data part and the pilot symbol part are divided into three subchannel allocation methods, ie, all subchannel allocation (FUSC), some subchannel allocation (PUSC), and adaptive modulation and coding (AMC), according to different transmission modes. Divided.

  FIG. 3 shows subchannel distribution and subcarrier gain according to the AMC method. Here, the abscissa represents the frequency, that is, the band position of the subcarrier, and the ordinate represents the width value of the channel gain corresponding to the subcarrier. FIG. 3 shows a total of 10 subchannels, each subchannel comprising 3 physically adjacent subcarriers. Subcarriers belonging to different subchannels are indicated by different types of lines.

  As can be seen from FIG. 3, since the change in channel gain of adjacent subcarriers is small, the subchannel code error rate is mainly determined by the subcarrier having the worst channel gain, and the transmission capacity of the subchannel is also determined accordingly. It is decided. Therefore, as a basis for selection, the S / N ratio in the subcarrier having the smallest channel gain of each subchannel can be used instead of the effective S / N ratio.

  FIG. 4 is a block diagram conceptually showing an OFDM system to which a subchannel selection method and apparatus according to an embodiment can be applied.

  Comparing FIG. 4 with FIG. 1, the OFDM system shown in FIG. 4 is different from the OFDM system shown in FIG. 1 in that a sub-channel selection device 105 ′ is used instead of the sub-channel selection device 105 shown in FIG. Recognize. The functions of other devices may be the same as those in the prior art, or may be realized by any technique known to those skilled in the art from now on. Detailed description is omitted here. Hereinafter, the sub-channel selection device 105 'will be described in detail.

  FIG. 5 is a block diagram showing a configuration of the subchannel selection device 105 'according to an embodiment.

  As shown in FIG. 5, the subchannel selection device 105 ′ according to an embodiment includes worst subcarrier determination means 51 and comparison selection means 52. Worst subcarrier determining means 51 determines the subcarrier having the worst S / N ratio of each subchannel, that is, the worst subcarrier, based on each subcarrier gain of each subchannel from channel estimation apparatus 104. Based on the S / N ratio of the worst subcarrier in each subchannel determined by the worst subcarrier determination means 51, the comparison / selection means 52 is the worst subcarrier having the highest subcarrier S / N ratio, that is, the best worst subcarrier. Select a career. The subchannel in which this subcarrier is located is selected as a subchannel to send back.

Assume that the total number of subchannels is G, and that each subchannel includes K subcarriers. First, of the m-th subchannel, the subcarrier having the worst (smallest) S / N ratio is determined, and the value γ _m of the S / N ratio is shown as follows.

を得られる。チャネル利得h_m,iはチャネル推定装置104から取得されるものである。 Here, γ _{m, i} represents the S / N ratio of the i-th subcarrier in the m-th subchannel, and as shown in the equation (1), from the channel gain hm _{, i}

Can be obtained. The channel gain hm _{, i} is acquired from the channel estimation device 104.

Next, compare the values of gamma _m for all subchannels, and returns to the sender by selecting the largest sub-channel value of gamma _m is. This process can be shown as follows.

ここで、γ_optは選択されたサブチャネルにおける最悪サブキャリアのS/N比を示す。

Here, γ _opt represents the S / N ratio of the worst subcarrier in the selected subchannel.

  The subchannel selection apparatus according to the above embodiment is applied to a single antenna system. In a single antenna system, this method can be applied to avoid the weighted average operation and obtain a result with a simple comparison. Therefore, the degree of complexity is very small, and it is applied when the mobile station selects a subchannel. Is done. When other parameters such as channel information are returned at the same time in the AMC method, the channel information (CQI) of all subchannels must be statistically analyzed in the normal subchannel selection method. Only the channel information (CQI) of the subchannel needs to be calculated.

  FIG. 6 is a block diagram showing a configuration of a subchannel selection device 105 'according to another embodiment.

  As shown in FIG. 6, the subchannel selection apparatus 105 ′ according to another embodiment includes worst subcarrier determination means 51, comparison selection means 52, and gain synthesis means 53.

ここで、

は各分岐路の出力信号を、yは合成された出力信号を、α_iは異なる分岐路の重み付け係数をそれぞれ示す。異なる合成方法は、重み付け係数の演算方法が異なる。選択的合成方法では、S/N比が最も大きい（高い）信号を合成器の出力y=y_mとして選択し、そのうち、m番目の分岐路はS/N比が

であって最も大きい。均等利得合成方法では、各分岐路の重み付け係数は等しく、

である。一方、最大比率合成方法では、各分岐路の重み付け係数はそれぞれのチャネル利得の幅値に比例する、即ち

となっている。最大比率合成方法は最適な合成方法であり、平均出力が最も大きいS/N比を得られるので、最も多く適用されている。しかしながら、異なる合成方法はシステムの受信性能に影響を与えるだけであり、本明細書の選択方法の有効性に影響を与えない。 6 is applied to a single transmission multiple reception (SIMO) system and a multiple transmission single reception (MISO) system. A single transmission multiple reception (SIMO) system is a system that transmits from a single antenna and receives from multiple antennas. In the case of a single transmission multiple reception (SIMO) system, first, the gain combining means 53 combines the gains of homologous subcarriers from different antennas (the gain of each subcarrier of each receiving antenna is output from the channel estimation device 104). The combining method is determined by the receiving side. As a combining method applied to a plurality of receiving antennas, there are a selective combining method, a maximum ratio combining method, and an equal gain combining method. In the case of a single transmission multi-reception system having Nr reception antennas, the output of the combiner is expressed by the following equation.

here,

Indicates an output signal of each branch path, y indicates a synthesized output signal, and α _i indicates a weighting coefficient of a different branch path. Different combining methods differ in the method of calculating weighting coefficients. In the selective synthesis method, the signal with the highest (high) S / N ratio is selected as the output y = y _m of the synthesizer, of which the mth branch has the S / N ratio.

And the biggest. In the equal gain combining method, the weighting coefficient of each branch path is equal,

It is. On the other hand, in the maximum ratio combining method, the weighting coefficient of each branch path is proportional to the width value of each channel gain, that is,

It has become. The maximum ratio synthesis method is the optimum synthesis method, and is most frequently applied because it can obtain an S / N ratio with the highest average output. However, different combining methods only affect the reception performance of the system and do not affect the effectiveness of the selection method herein.

  The gain combining shown in Expression (5) is performed for each subcarrier of different receiving antennas. After combining, the plurality of receiving antennas become one equivalent antenna, so that the subchannel can be selected in the same manner as in the single antenna system. That is, worst subcarrier determining means 51 determines the worst subcarrier of each subchannel based on the combined subcarrier gain of each subchannel. The comparison / selection means 52 determines the subcarrier S / N ratio of the worst subcarrier of each subchannel determined by the worst subcarrier determination means 51, selects the best worst subcarrier, and returns the corresponding subchannel. As the subchannel to be selected.

ここで、Nrは受信アンテナの数であり、h_m,i,jはｊ番目の受信アンテナにおけるm番目のサブチャネルのi番目のサブキャリアのチャネル利得であり、チャネル推定装置104から出力される。次に、得られたγ_m,iについて、式（4）に基づきサブチャネルを選択する。 For example, in the maximum ratio synthesis method, γ _{m, i} in equation (4) is expressed as follows.

Here, Nr is the number of receiving antennas, hm _{, i, j} is the channel gain of the i-th subcarrier of the m-th subchannel in the j-th receiving antenna, and is output from the channel estimation device 104. . Next, for the obtained γ _{m, i} , a subchannel is selected based on Equation (4).

ここで、式（7）中の

は、ｊ番目の受信アンテナにおけるm番目のサブチャネルのi番目のサブキャリアのS/N比である。 In the selective combining method or the equal gain combining method, the calculation method of γ _{m, i} is different, but the subsequent selection method is the same as the maximum ratio combining method. Here, equations for calculating γ _{m, i} are shown as follows.

Where in equation (7)

Is the S / N ratio of the i-th subcarrier of the m-th subchannel at the j-th receiving antenna.

ここで、N_tは送信アンテナの数を、h_m,i,jはn番目の送信アンテナにおけるm番目のサブチャネルのi番目のサブキャリアのチャネル利得をそれぞれ示す。そして、式（4）に基づきサブチャネルを選択する。 A multi-transmission single reception (MISO) system is a system that transmits from multiple antennas and receives with a single antenna. MISO systems generally use transmit diversity technology, and the factor that affects the receive performance of transmit diversity is the 2-norm of the channel matrix, so first the channel gain of each subcarrier between transmit antennas. And then use a selection method similar to the single antenna system. An arithmetic expression for combining the gains of the MISO transmitting antennas is as follows.

Here, N _t represents the number of transmission antennas, and _{hm, i, j} represents the channel gain of the i-th subcarrier of the m-th subchannel in the n-th transmission antenna. And a subchannel is selected based on Formula (4).

ここで、h_m,i,n,jはn番目の送信アンテナとｊ番目の受信アンテナとの間におけるm番目のサブチャネルのi番目のサブキャリアのチャネル利得を、N_tは送信アンテナの数を、Nrは受信アンテナの数をそれぞれ示す。以降の選択方法は式（4）と同様である。 In the case of a multi-transmission multi-reception (MIMO) system, the selection criteria for subchannels are determined by the data format on the transmission side, and MIMO systems generally have two types: space-time coding (STC) and space division multiplexing (SM). Use the method. In the space-time coding method, the selection method is the same as the transmission diversity of MISO, and the difference is that a statistical dimension of receiving antenna is added. In this case, the calculation formula for combining the gains is as follows.

Here, hm _{, i, n, j} is the channel gain of the i-th subcarrier of the m-th subchannel between the n-th transmit antenna and the j-th receive antenna, and N _t is the number of transmit antennas. Nr indicates the number of receiving antennas. Subsequent selection methods are the same as in equation (4).

ここで、Ｈはチャネルマトリックスであり、チャネル推定装置104から出力され、UとVはそれぞれNr×NrとN_t×N_tのユニタリマトリックスであり、Dは対角行列であり、その対角線における0以上の要素はmin(Nr,N_t)個を上回らない。特異値を分解するアルゴリズムは、行列理論の典型的なアルゴリズムであり、特定のHに対して、分解されたD行列の非ゼロ対角線要素は変わらない。非ゼロ対角線要素それぞれは送信側及び受信側の一つの等価的な並行分岐路を代表して、並行分岐路同士は互いに干渉しない。それら並行チャネルはそのサブキャリアの伝送能力を反映している。次に、利得合成手段53は、サブキャリア毎に分岐路の利得を合成し、即ち、一つのサブキャリアに対応する全ての分岐路の利得を合成し、合成された利得をそのサブキャリアの利得とする。サブキャリアのS/N比は次のように算出され、あるサブキャリアにL個の等価的な並行分岐路があり、各並行分岐路の利得（D行列の非ゼロ対角線要素）を

とすると、そのS/N比は次のように示す。

A MIMO system based on the spatial division multiplexing modulation method shows a subchannel selection device 105 ′ in FIG. FIG. 7 is a block diagram showing a configuration of a subchannel selection device 105 ′ according to still another embodiment. As shown in FIG. 7, for each subcarrier, the branch path separating means 54 of the sub-channel selector 105 ', first Nr × N _t each element h _i of the MIMO channel matrix H (a matrix _{of, j} is the i-th The channel gain between the first transmit antenna and the jth receive antenna) is converted into several equivalent parallel branches. The parallel branch means that the mixed channel between a plurality of transmission antennas and a plurality of reception antennas is equivalently indicated by several parallel and individual branch paths, and each branch path includes a transmission antenna and a reception antenna. Since there is a one-to-one correspondence between the two, there is no interference. This corresponds to an increase in some branches compared to the single transmission single reception system, and the capacity can be improved. An equivalent parallel branch can be realized by decomposing the singular values of the matrix (SVD).

Here, H is a channel matrix and is output from the channel estimation device 104, U and V are unitary matrices of Nr × Nr and N _t × N _t , respectively, D is a diagonal matrix, and 0 in the diagonal line The above elements do not exceed min (Nr, N _t ). The algorithm for decomposing singular values is a typical algorithm in matrix theory, and for a specific H, the nonzero diagonal elements of the decomposed D matrix do not change. Each non-zero diagonal element represents one equivalent parallel branch on the transmitting side and the receiving side, and the parallel branches do not interfere with each other. These parallel channels reflect the transmission capability of the subcarrier. Next, the gain combining means 53 combines the gains of the branch paths for each subcarrier, that is, combines the gains of all the branch paths corresponding to one subcarrier, and combines the combined gains with the gains of the subcarriers. And The S / N ratio of the subcarrier is calculated as follows. There are L equivalent parallel branches in a subcarrier, and the gain of each parallel branch (nonzero diagonal element of D matrix)

Then, the S / N ratio is shown as follows.

As the i-th subcarrier of the m-th subchannel, γ _{m, i} which is the S / N ratio of the subcarrier calculated by the equation (12) corresponding thereto is obtained, and then the worst subcarrier determining means 51 The worst subcarrier is determined. The method for this is the same as in equation (4), and the subsequent processing is also the same.

  FIG. 8 is a block diagram showing a configuration of a subchannel selection device 105 'according to still another embodiment.

  As shown in FIG. 8, the subchannel selection apparatus further includes CQI calculation means 55 that calculates the CQI of the selected subchannel (calculates only the CQI of the selected subchannel). The calculated CQI is returned to the transmitter side. For calculating CQI, any method known to those skilled in the art, such as the EESM or RBIR method described above, can be used.

  FIG. 9 is a flowchart of a subchannel selection method according to an embodiment.

  As shown in FIG. 9, in the subchannel selection method according to an embodiment, when a channel gain is input, first, in step 901, the worst subcarrier is determined, that is, the channel of each subcarrier in each of a plurality of subchannels. The S / N ratio of each subcarrier is determined based on the gain, and the worst subcarrier of each of the plurality of subchannels is determined based on the S / N ratio. This step can be realized by, for example, the worst subcarrier determination means described above. Next, in step 902, comparison / selection is performed. Specifically, based on the S / N ratio of the worst subcarrier in each subchannel determined in the worst subcarrier determination step, the worst worst subcarrier among the worst subcarriers is determined, and this best worst subcarrier is determined. Select the subchannel corresponding to. This step can be realized by the comparison and selection means described above.

  FIG. 10 is a flowchart of a subchannel selection method according to another embodiment.

  As shown in FIG. 10, compared with the method shown in FIG. 9, the subchannel selection method according to another embodiment adds a gain combining step 903. In step 903, in the case of the SIMO system, the subcarrier gain is combined with the homologous subcarriers received by the plurality of antennas. On the other hand, in the case of the MISO system, subcarrier gains are combined with homologous subcarriers transmitted from a plurality of antennas.

  The receiving side of the SIMO system can apply a gain combining method such as selective combining, maximum ratio combining, and equal gain combining.

  In step 901, the worst subcarrier of each subchannel is determined for the subcarriers of each subchannel combined in the gain combining step.

  FIG. 11 is a flowchart of a subchannel selection method according to still another embodiment.

  As shown in FIG. 11, as compared with the method shown in FIG. 9, the subchannel selection method according to another embodiment adds a branch path decomposition step 904 and a gain synthesis step 903. In a branch path decomposition step 904, the gain of each subcarrier transmitted from a plurality of antennas and received by a plurality of receiving antennas is converted into one or more equivalent parallel branch path gains. In the gain combining step 903, the gain of each parallel branch decomposed in the branch decomposition step is combined for each subcarrier.

  In step 901, the worst subcarrier of each subchannel is determined for the subcarriers of each subchannel combined in the gain combining step.

  The branch path decomposition step 904 and the gain synthesis step 903 can be realized by, for example, the branch path decomposition means 54 and the gain synthesis means 53 described above.

  It should be noted that the above-mentioned worst subcarrier determining means 51, comparison / selecting means 52, gain synthesizing means 53, branch path decomposing means 54, etc. are logic units or intelligent units (for example, microprocessors, programmable logic devices, etc.). This can be realized by executing a computer program. Correspondingly, steps 901 to 904 described above can also be realized by executing a computer program by an intelligent unit or a logic unit. These computer programs and media storing these computer programs, such as CDs, VCDs, DVDs, floppy disks, flash memories, hard disks, etc. are all included within the scope of the present invention.

  According to the above description, since the method according to the present disclosure uses only linear operation, it has a remarkable advantage that the processing on the mobile station side can be simplified by avoiding the complicated weighted averaging method.

  The present disclosure can also provide a computer program that, when executed by a logic unit, causes the logic unit to implement the subchannel selection device, the subchannel selection method, or each step.

  The present disclosure also provides a computer program storage medium that stores the computer program. The computer program storage medium may be any storage medium known to those skilled in the art, such as flash memory, hard disk, floppy disk, CD, VCD, DVD, MO, and the like.

  Features described and / or disclosed with respect to one embodiment may be applied to one or more other embodiments in a similar or similar form, may be combined with features of other embodiments, or otherwise. The features of the embodiment may be substituted.

  As used herein, the term “comprising”, as used herein, means the presence of a feature, integral, step or part, but one or more other features, integrals, steps. It does not exclude the presence or addition of parts.

Claims (5)

A subchannel selection device for selecting a subchannel from a plurality of subchannels having one or more subcarriers,
Worst subcarrier for determining S / N ratio of each subcarrier based on channel gain of each subcarrier of each of the plurality of subchannels, and determining worst subcarrier in each of the plurality of subchannels based on S / N ratio A determination means;
Based on the S / N ratio of the worst subcarrier in each subchannel determined by the worst subcarrier determining means, the worst S / N ratio among the worst subcarriers is determined, that is, the best worst subcarrier is determined. Comparison and selection means for selecting a subchannel corresponding to the best worst subcarrier;
Branch path decomposition means for converting the gain of each subcarrier transmitted from the plurality of antennas and received by the plurality of reception antennas into the gain of one or more equivalent parallel branches;
For each subcarrier, gain combining means for combining the gain of each parallel branch decomposed by the branch path decomposition means;
With
The worst subcarrier determining means determines the worst subcarrier in each subchannel for the subcarriers of each subchannel combined by the gain combining means.   The branch path decomposition means uses the singular value decomposition method to calculate the one or more equivalent parallel branches from a matrix composed of gains of subcarriers transmitted from the plurality of antennas and received by the plurality of reception antennas. The subchannel selection apparatus according to claim 1, wherein a gain of the path is acquired.   The subchannel selection apparatus according to claim 1 or 2, further comprising CQI calculation means for calculating channel information of the selected subchannel. A subchannel selection method for selecting an appropriate subchannel from a plurality of subchannels having one or more subcarriers,
Worst subcarrier for determining S / N ratio of each subcarrier based on channel gain of each subcarrier of each of the plurality of subchannels, and determining worst subcarrier in each of the plurality of subchannels based on S / N ratio A decision step;
Based on the S / N ratio of the worst subcarrier in each subchannel determined in the worst subcarrier determination step, the worst S / N ratio among the worst subcarriers is determined, that is, the best worst subcarrier is determined. A comparison and selection step of selecting a subchannel corresponding to the best worst subcarrier;
A branch path decomposition step for converting the gain of each subcarrier transmitted from the plurality of antennas and received by the plurality of receiving antennas into one or more equivalent parallel branch gains;
For each subcarrier, a gain combining step of combining the gain of each parallel branch decomposed by the branch path decomposition means;
With
The worst subcarrier determination step determines a worst subcarrier in each subchannel for the subcarriers of each subchannel combined in the gain combining step. A receiver comprising the subchannel selection device according to claim 1.

Images