JP2004260423A - Diversity receiver and its method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diversity receiver and its method capable of preventing the occurrence of following failures by maintaining the accuracy of transmission line estimation even when an error is caused in data after hard decision. <P>SOLUTION: The diversity receiver comprises FFT parts (11, 12), transmission line estimation parts (51, 52) for inputting post-FFT data in each subcarrier of a symbol and remapping post data of the same symbol and amplitude/phase correction parts (21, 22) for inputting a transmission line estimation value of each subcarrier and an output signal of each subcarrier which is outputted from the FFT part in each branch. The diversity receiver comprises also a selective synthesis part (9) for selecting an optimum output signal out of signals outputted from the amplitude/phase correction part (21, 22) of each branch, a hard decision part (3) for performing the hard decision of the signal outputted from the selective synthesis part (9) and a remapping part (4) for remapping the signal outputted from the hard decision part (3) and inputting the remapped signal to the transmission line estimation part (51, 52) of each branch. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００５２】
前述した本発明の種々の実施形態によれば、本発明の技術思想及び見地の範囲の種々の変更、修正及び省略は、当業者によれば容易に行うことができる。特に、前述した実施形態においては、ブランチ数が２の場合であるが、ブランチ数はいくつであってもよい。また、前述した実施形態においては、ＯＦＤＭ方式の移動体通信に用いられる受信装置について説明したが、送信フレーム内で振幅・位相補正後の硬判定結果をレプリカとして伝搬路推定値を逐次更新を行い、かつ最大比合成ダイバーシチを行う受信装置であれば、本発明を適用できる。即ち、前述の説明はあくまで例であって、何ら制約しようとするものではない。本発明は、特許請求の範囲及びその均等物として限定するものにのみ制約される。
【００５３】
【発明の効果】
本発明によれば、プリアンブル信号から推定した伝搬路推定値を初期値とし、それ以降復調したＯＦＤＭデータシンボルの硬判定をレプリカとして伝搬路推定値を更新していく方法にダイバーシチ受信を適用する。ダイバーシチ受信装置によれば、従来技術で伝搬路推定値の追従に失敗するような場合であっても、伝搬路推定精度を維持することで追従の失敗を防ぎ、伝送効率を低下させることなく、伝搬路推定を行い、かつ最大比合成ダイバーシチ受信が可能となる。
【００５４】
ここで、伝搬路推定は、サブキャリア毎に伝送品質の良いブランチを１つ選択し、そのブランチの硬判定をレプリカとして伝搬路推定を行う。一方、復調は、サブキャリア毎に最大比合成を行った結果に対し行う。これにより、伝搬路推定値の精度を高めることができる。
【００５５】
図６は、本発明におけるビット誤り率のグラフである。尚、図６のグラフは、最大ドップラー周波数ｆ_Ｄが２００ＭＨｚの場合のものであり、以下の構成要因の下で得られたものである。
【００５６】
変調方式：ＱＰＳＫ、同期検波
情報伝送速度：２４Ｍｂｉｔ／ｓ
ＦＦＴポイント数：６４
有効シンボル周期：３．２μｓ
ＯＦＤＭシンボル周期：４．０μｓ
フレーム周期：２ｍｓ
伝搬路モデル：２波等電力モデル
ブランチ数：２（最大比合成）
【００５７】
図６によれば、図１のダイバーシチを用いていない従来の構成と、図２のダイバーシチ構成と、図７のダイバーシチ構成とを比較している。これによれば、図２のダイバーシチ構成が、ＢＥＲ特性が最も良いことが明らかである。これは、レプリカとして利用する硬判定結果に誤りが生じると、伝搬路歪み補正後の位相誤差が増幅されることから、より信頼度の高い合成前の硬判定結果をレプリカとして選択する方が、伝搬路に精度良く追従できるためであると考えられる。
【００５８】
本発明によれば、受信情報サブキャリアの硬判定結果をレプリカとして伝搬路推定値をフレーム内で更新する方法について、ダイバーシチ受信を適用した。その結果、最大比合成前における信頼度の高いブランチの硬判定結果をレプリカとして全ブランチの伝搬路推定値を更新することにより、ＢＥＲ特性が改善でき、より高品質で安定した通信サービスを提供することが可能となる。
【図面の簡単な説明】
【図１】従来の伝搬路推定を行うＯＦＤＭ受信装置の構成図である。
【図２】本発明のダイバーシチ受信装置における第１の実施形態の構成図である。
【図３】本発明のダイバーシチ受信装置における第２の実施形態の構成図である。
【図４】本発明のダイバーシチ受信装置における第３の実施形態の構成図である。
【図５】本発明のダイバーシチ受信装置における第４の実施形態の構成図である。
【図６】本発明におけるビット誤り率のグラフである。
【図７】伝搬路推定に用いる硬判定を最大比合成結果から得るダイバーシチ構成の構成図である。
【符号の説明】
１、１１、１２ ＦＦＴ部
２、２１、２２ 振幅・位相補正部
３、３１、３２ 硬判定部
４ 再マッピング部
５、５１、５２ 伝搬路推定部
６ 復調部
７ 硬判定結果選択部
８ 最大比合成部
９ 選択合成部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a diversity receiving apparatus and method. In particular, the present invention relates to a mobile communication system that is included in an OFDM receiving apparatus that involves channel estimation.
[0002]
[Prior art]
A transmission frame received by the diversity receiving apparatus according to the present invention is composed of a known OFDM preamble signal at the head and a subsequent OFDM data symbol sequence. As a system adopting such a transmission frame configuration, for example, there is MMAC HiSWANA (ARIB STD-T70) or the like. 2. Description of the Related Art Conventionally, a scheme has been proposed in which a receiving apparatus sequentially estimates propagation path characteristics using information symbols subjected to amplitude / phase fluctuation compensation (for example, see Non-Patent Document 1).
[0003]
FIG. 1 is a configuration diagram of a conventional OFDM receiver for performing propagation path estimation.
[0004]
According to FIG. 1, the demodulation processing unit of the OFDM receiving apparatus includes an FFT (Fast Fourier Transform: fast Fourier transform) unit 1, a propagation path estimation unit 5, an amplitude / phase correction unit 2, a demodulation unit 6, It has a hard decision unit 3 and a remapping unit 4.
[0005]
The FFT unit 1 converts a received signal having a time waveform into a signal for each subcarrier on the frequency axis. The converted signal is output to the amplitude / phase correction unit 2 and the propagation path estimation unit 5.
[0006]
The propagation path estimating unit 5 estimates the propagation path for each subcarrier by dividing the post-FFT data for each subcarrier of the symbol from the FFT unit 1 by the remapped data for the same symbol. The channel estimation value for each subcarrier is input to the amplitude / phase correction unit 2.
[0007]
The amplitude / phase correction unit 2 corrects the amplitude and phase of each subcarrier based on the channel estimation value of each subcarrier from the channel estimation unit 5 and the output signal of each subcarrier from the FFT unit 1. I do. The channel estimation value is obtained for a symbol before the symbol. Further, the amplitude and phase of the data symbol at the head of the frame are corrected using the propagation path estimation value obtained from the preamble signal arranged before the data symbol. The corrected signal is input to the hard decision section 3.
[0008]
Hard decision section 3 makes a hard decision on the corrected signal, and outputs a hard decision result signal to remapping section 4. Remapping section 4 maps the hard decision result signal again, and outputs the re-mapped data to propagation path estimation section 5.
[0009]
As described above, the channel estimation value obtained using the preamble signal is used as an initial value, and the channel estimation value is successively updated with the subsequent data symbols, so that the channel variation in the frame that occurs during high-speed movement can be reduced. It is possible to follow.
[0010]
[Non-patent document 1]
Ryuhei Funada, Hiroshi Harada, Yoshihide Kamio, Shoji Shinoda, Masayuki Fujise "A Study on Amplitude-Phase Fluctuation Compensation Method for OFDM Packet Wireless Transmission System in High-Speed Fading Environment", IEICE Tech. −05)
[0011]
[Problems to be solved by the invention]
However, in the above-described conventional apparatus and method, in the process of updating the channel estimation value in the frame, if an error occurs in the data after the hard decision due to fast channel fluctuation, the channel estimation is performed using the result. Large errors occur in the values. Since this error affects subsequent demodulation in the transmission frame, there has been a problem that bit errors in demodulated data occur up to the end of the transmission frame.
[0012]
Therefore, the present invention is intended to prevent the failure of following by maintaining the accuracy of the channel estimation even when it is difficult to accurately update the channel estimation value as described above, and to reduce the transmission efficiency. It is an object of the present invention to provide a diversity receiving apparatus and method.
[0013]
[Means for Solving the Problems]
The present invention includes a receiving unit that receives a time signal for each of a plurality of branches, receives a transmission frame having a known preamble signal and a data symbol, and estimates a subcarrier in the preamble signal and the data symbol. The present invention relates to a diversity receiving apparatus and method used for the method.
[0014]
According to the diversity receiver of the present invention,
For each branch,
FFT means for converting the received time signal into a signal for each subcarrier on the frequency axis;
Channel estimation means for estimating the propagation path for each subcarrier by dividing the post-FFT data for each subcarrier of the symbol output from the FFT means by the post-remapping data for the same symbol;
Amplitude / phase correction means for correcting the amplitude and phase of each subcarrier based on the channel estimation value for each subcarrier output from the channel estimation means and the output signal for each subcarrier output from the FFT means; And further,
An output signal for each subcarrier from the FFT means and an amplitude / phase corrected signal from the amplitude / phase correction means for each branch are input, and after the amplitude / phase correction corresponding to the output signal having the largest received power of the carrier. Selection synthesis means for selecting a signal,
Hard decision means for hard-deciding the signal output from the selection synthesis means,
Re-mapping means for re-mapping the signal output from the hard decision means, and inputting the re-mapped data to the channel estimation means for each branch.
It is characterized by having.
[0015]
According to the diversity receiver of the present invention,
For each branch,
FFT means for converting the received time signal into a signal for each subcarrier on the frequency axis;
Channel estimation means for estimating the propagation path for each subcarrier by dividing the post-FFT data for each subcarrier of the symbol output from the FFT means by the post-remapping data for the same symbol;
Amplitude / phase correction means for correcting the amplitude and phase of each subcarrier based on the channel estimation value for each subcarrier output from the channel estimation means and the output signal for each subcarrier output from the FFT means; And further,
The propagation path estimation value for each subcarrier output from the propagation path estimation means and the amplitude / phase corrected signal from the amplitude / phase correction means for each branch are input, and the propagation path estimation value with the smallest phase value is input. Selection synthesis means for selecting a corresponding amplitude / phase corrected signal,
Hard decision means for hard-deciding the signal output from the selection synthesis means,
Re-mapping means for re-mapping the signal output from the hard decision means, and inputting the re-mapped data to the channel estimation means for each branch.
It is characterized by having.
[0016]
According to the diversity receiver of the present invention,
For each branch,
FFT means for converting the received time signal into a signal for each subcarrier on the frequency axis;
Channel estimation means for estimating the propagation path for each subcarrier by dividing the post-FFT data for each subcarrier of the symbol output from the FFT means by the post-remapping data for the same symbol;
Amplitude / phase correction means for correcting the amplitude and phase of each subcarrier based on the channel estimation value for each subcarrier output from the channel estimation means and the output signal for each subcarrier output from the FFT means; ,
Hard decision means for hard-deciding the signal output from the amplitude / phase correction means,
Hard decision which inputs an output signal for each subcarrier from the FFT means and a hard decision result signal from the hard decision means for each branch, and selects a hard decision result signal corresponding to an output signal having the largest received power of a carrier wave. Means for selecting results;
Re-mapping means for re-mapping the signal output from the hard decision result selecting means, and inputting the re-mapped data to the propagation path estimating means for each branch.
It is characterized by having.
[0017]
Furthermore, according to the diversity receiving apparatus of the present invention,
For each branch,
FFT means for converting the received time signal into a signal for each subcarrier on the frequency axis;
Channel estimation means for estimating the propagation path for each subcarrier by dividing the post-FFT data for each subcarrier of the symbol output from the FFT means by the post-remapping data for the same symbol;
Amplitude / phase correction means for correcting the amplitude and phase of each subcarrier based on the channel estimation value for each subcarrier output from the channel estimation means and the output signal for each subcarrier output from the FFT means; ,
Hard decision means for hard-deciding the signal output from the amplitude / phase correction means,
The channel estimation value for each subcarrier output from the channel estimation unit and the hard decision result signal from the hard decision unit for each branch are input, and the hard decision corresponding to the channel estimation value with the smallest phase value is input. A hard decision result selecting means for selecting a result signal,
Re-mapping means for re-mapping the signal output from the hard decision result selecting means, and inputting the re-mapped data to the propagation path estimating means for each branch.
It is characterized by having.
[0018]
According to another embodiment of the diversity receiver of the present invention,
A maximum ratio combining means for combining a plurality of output signals from the amplitude / phase correcting means for each branch with a maximum ratio combining for each subcarrier;
Demodulating means for demodulating the signal output from the maximum ratio combining means;
It is also preferred to further have
[0019]
According to another embodiment of the diversity receiving apparatus of the present invention,
It is also preferable that the propagation path estimating means estimates the propagation path using the known preamble signal as a replica for the preamble signal and using the data symbol output from the remapping means as a replica for the data symbol.
[0020]
Further, according to another embodiment of the diversity receiver of the present invention,
It is also preferable that the propagation path estimating means outputs a weighted average of a plurality of estimated values before and after in time.
[0021]
An OFDM receiving apparatus according to the present invention includes the diversity receiving apparatus described above.
[0022]
According to the diversity receiving method of the present invention,
For each branch,
An FFT step of converting the received time signal into a signal for each subcarrier on the frequency axis;
A channel estimation step of estimating a propagation path for each subcarrier by dividing the post-FFT data for each subcarrier of the symbol output from the FFT step by data after remapping of the same symbol;
An amplitude / phase correction step of correcting the amplitude and phase of each subcarrier based on the channel estimation value of each subcarrier output from the channel estimation step and the output signal of each subcarrier output from the FFT step; And further,
An output signal for each subcarrier from the FFT step and an amplitude / phase corrected signal from the amplitude / phase correction step for each branch are input, and after the amplitude / phase correction corresponding to the output signal having the largest received power of the carrier. A selection synthesis step for selecting a signal;
A hard-decision step for hard-deciding a signal output from the selective combining step;
Re-mapping the signal output from the hard decision step, and inputting the re-mapped data to the channel estimation step for each branch; and
It is characterized by having.
[0023]
According to the diversity receiving method of the present invention,
For each branch,
An FFT step of converting the received time signal into a signal for each subcarrier on the frequency axis;
A channel estimation step of estimating a propagation path for each subcarrier by dividing the post-FFT data for each subcarrier of the symbol output from the FFT step by data after remapping of the same symbol;
An amplitude / phase correction step of correcting the amplitude and phase of each subcarrier based on the channel estimation value of each subcarrier output from the channel estimation step and the output signal of each subcarrier output from the FFT step; And further,
The propagation path estimation value for each subcarrier output from the propagation path estimation step and the amplitude / phase corrected signal from the amplitude / phase correction step for each branch are input, and the propagation path estimation value with the smallest phase value is input. A selection synthesis step of selecting a corresponding amplitude / phase corrected signal,
A hard-decision step for hard-deciding a signal output from the selective combining step;
Re-mapping the signal output from the hard decision step, and inputting the re-mapped data to the channel estimation step for each branch; and
It is characterized by having.
[0024]
According to the diversity receiving method of the present invention,
For each branch,
An FFT step of converting the received time signal into a signal for each subcarrier on the frequency axis;
A channel estimation step of estimating a propagation path for each subcarrier by dividing the post-FFT data for each subcarrier of the symbol output from the FFT step by data after remapping of the same symbol;
An amplitude / phase correction step of correcting the amplitude and phase of each subcarrier based on the channel estimation value of each subcarrier output from the channel estimation step and the output signal of each subcarrier output from the FFT step; ,
A hard decision step of hard-deciding the signal output from the amplitude / phase correction step,
Hard decision which inputs an output signal for each subcarrier from the FFT step and a hard decision result signal from the hard decision step for each branch, and selects a hard decision result signal corresponding to the output signal having the largest received power of the carrier wave A result selection step;
Re-mapping the signal output from the hard decision result selection step, and inputting the re-mapped data to the channel estimation step for each branch;
It is characterized by having.
[0025]
Furthermore, according to the diversity receiving method of the present invention,
For each branch,
An FFT step of converting the received time signal into a signal for each subcarrier on the frequency axis;
A channel estimation step of estimating a propagation path for each subcarrier by dividing the post-FFT data for each subcarrier of the symbol output from the FFT step by data after remapping of the same symbol;
An amplitude / phase correction step of correcting the amplitude and phase of each subcarrier based on the channel estimation value of each subcarrier output from the channel estimation step and the output signal of each subcarrier output from the FFT step; ,
A hard decision step of hard-deciding the signal output from the amplitude / phase correction step,
The channel estimation value for each subcarrier output from the channel estimation step and the hard decision result signal from the hard decision step for each branch are input, and the hard decision corresponding to the channel estimation value with the smallest phase value is input. A hard decision result selecting step of selecting a result signal, and a remapping step of re-mapping the signal output from the hard decision result selecting step and inputting the re-mapped data to a channel estimation step for each branch.
It is characterized by having.
[0026]
According to another embodiment of the diversity receiving method of the present invention,
A maximum ratio combining step of combining a plurality of output signals from the amplitude / phase correction step for each branch with a maximum ratio for each subcarrier;
A demodulation step of demodulating the signal output from the maximum ratio combining step;
It is also preferred to further have
[0027]
According to another embodiment of the diversity receiving method of the present invention,
In the propagation path estimation step, it is also preferable that the propagation path is estimated using a known preamble signal as a replica for the preamble signal and a data symbol output from the remapping step as a replica for the data symbol.
[0028]
Further, according to another embodiment of the diversity receiving method of the present invention,
It is also preferable that the channel estimation step outputs a weighted average value of a plurality of estimated values before and after the time.
[0029]
According to the OFDM receiving method of the present invention, the diversity receiving method is provided.
[0030]
That is, when the present invention applies the diversity reception to a method of updating the propagation path estimation value using the propagation path estimation value estimated from the preamble signal as an initial value and thereafter making the hard decision of the OFDM data symbol demodulated as a replica, Propagation path estimation selects a branch for each subcarrier and uses the hard decision of that branch, while demodulation uses the result of performing maximum ratio combining for each subcarrier to improve the propagation path estimation accuracy and diversity reception. The effect is to improve the transmission characteristics.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0032]
FIG. 2 is a configuration diagram of the first embodiment of the diversity receiver according to the present invention.
[0033]
According to FIG. 2, for each branch for diversity reception, the FFT unit 1 (11 and 12), the propagation path estimation unit 5 (51 and 52), and the amplitude / phase correction unit 2 (21 and 22) in FIG. ). Output data from the amplitude / phase correction units 21 and 22 are input to the maximum ratio combining unit 8. The maximum ratio combining unit 8 combines the plurality of output data from the amplitude / phase correction units 21 and 22 for each branch with the maximum ratio for each subcarrier. The synthesized signal is subjected to final demodulation processing such as demapping and error correction decoding by the demodulation unit 6 and output.
[0034]
The signals output from the amplitude / phase correction units 21 and 22 for each branch are further input to the selection synthesis unit 9. The selecting / combining unit 9 selects, for each subcarrier, an output signal of a branch having the largest carrier received power for all branches. Here, the received power of the carrier is calculated using the signals from the FFT units 11 and 12. As a result, it is possible to update the propagation path estimation using the output signal of the branch having good transmission quality, and to reduce the probability of the estimation value being out of tracking.
[0035]
The output signal selected by the selection / synthesis unit 9 is input to the hard decision unit 3. The signal hard-decided by the hard decision unit 3 is input to the remapping unit 4. The remapping unit 4 maps the hard-decided signal again, and inputs the re-mapped data to the channel estimation units 51 and 52 for each branch.
[0036]
FIG. 3 is a configuration diagram of a second embodiment of the diversity receiver according to the present invention.
[0037]
Hereinafter, FIG. 3 will be described only with respect to differences from FIG. According to FIG. 3, the selection / synthesis unit 9 inputs the channel estimation values output from the channel estimation units 51 and 52. The selection / synthesis unit 9 determines a branch having the smallest phase of the propagation path estimation value as a branch having good transmission quality for all subcarriers, and outputs an amplitude / phase corrected signal of the branch. As a result, it is possible to perform propagation path estimation using hard decision of a branch having good transmission quality, and it is possible to reduce the probability of occurrence of deviation from tracking of an estimated value.
[0038]
FIG. 4 is a configuration diagram of a third embodiment of the diversity receiver according to the present invention.
[0039]
Hereinafter, FIG. 4 will be described only with respect to differences from FIG. According to FIG. 4, each branch further includes hard decision units 31 and 32. The received data output from the amplitude / phase correction units 21 and 22 are input to hard decision units 31 and 32, respectively. The hard decision result signals hard-decided by the hard decision units 31 and 32 are input to the hard decision result selection unit 7, respectively.
[0040]
The hard decision result selection unit 7 selects and outputs a hard decision result signal of a branch having the highest received power of a carrier for all branches for each subcarrier. As a result, it is possible to update the propagation path estimation by using the hard decision of the branch having good transmission quality, and to reduce the probability of the estimation value being out of tracking.
[0041]
The remapping unit 4 maps the hard decision result signal for each subcarrier output from the hard decision result selection unit 7 again, and outputs the result to the propagation path estimation units 51 and 52 of all branches.
[0042]
The processing of the channel estimation units 51 and 52 differs between the preamble signal portion and the data symbol portion of the transmission frame.
[0043]
The operation of the propagation path estimating units 51 and 52 in the preamble signal part of the transmission frame is based on the known transmission preambles that the reception preamble signals for each subcarrier extracted by the FFT processing are stored in the propagation path estimation units 51 and 52. Each of the signals is divided to obtain an estimated value of the propagation path. Here, when the time width of the preamble signal is larger than the time width of the FFT window, a propagation path estimation value is obtained from a plurality of FFT-processed preamble signals, and an averaging process is performed for each subcarrier to improve noise immunity. Can also be increased.
[0044]
On the other hand, the operation of the propagation path estimation units 51 and 52 in the data symbol part of the transmission frame is as follows. First, the channel estimation value obtained from the preamble signal arranged at the head of the frame is set as an initial value Hdata (0, k) of the estimation value. k represents a subcarrier number. Next, let the estimated value obtained from the n-th data symbol be Hdata (n, k). At this time, the amplitude and phase correction units 21 and 22 correct the amplitude and phase of the n-th data symbol using Hdata (n-1, k), which is an estimated value based on the post-remapped data of one symbol before. The hard decision is performed by the hard decision units 31 and 32, the hard decision result is selected by the hard decision result selection unit 7, and the remapping is performed by the remapping unit 4. By dividing each time, an estimated value Hdata (n, k) is obtained.
[0045]
As a result, the channel estimation units 51 and 52 perform the channel estimation using the channel estimation value estimated from the preamble signal as an initial value and the hard decision of the data symbol as a replica thereafter until the end of the transmission frame.
[0046]
As described above, when diversity reception is applied to a method of updating a propagation path estimation value using a propagation path estimation value estimated from a preamble signal as an initial value and thereafter making a hard decision of a demodulated OFDM data symbol as a replica to update the propagation path estimation value. In channel estimation, one branch having good transmission quality is selected for each subcarrier, and channel estimation is performed using hard decision of the branch.
[0047]
Here, the reason for adopting such a method is as follows. In other words, the hard decision result used for updating the propagation path estimation value is such that once an error occurs, it influences the propagation path estimation result up to the end of the frame. This is because the selective combining in which the instantaneous CNR is low in a burst time is less likely to affect the propagation path estimation result, and as a result, the propagation path estimation accuracy is considered to be improved. On the other hand, demodulation is performed on the result of performing maximum ratio combining for each subcarrier. This is because the maximum ratio combining that maximizes the average CNR is most advantageous in demodulation. In this way, by using selective combining for hard decisions used for channel estimation and using maximum ratio combining for demodulation, it is possible to achieve improved channel estimation accuracy and improved transmission characteristics due to the diversity reception effect. it can.
[0048]
FIG. 5 is a configuration diagram of a fourth embodiment of the diversity receiver according to the present invention.
[0049]
According to FIG. 5, compared with FIG. 4, the hard decision result selection unit 7 inputs the channel estimation values output from the channel estimation units 51 and 52. The hard decision result selection unit 7 determines a branch having the smallest phase of the channel estimation value as a branch having good transmission quality for all subcarriers, and selects and outputs a hard decision result of the branch. As a result, it is possible to update the propagation path estimation by using the hard decision of the branch having good transmission quality, and to reduce the probability of the estimation value being out of tracking.
[0050]
It is also effective to apply the averaging process in the time direction of the channel estimation value to the above-described method of updating the channel estimation value. That is, instead of setting the channel estimation value used for the correction of the amplitude and phase of the n-th data symbol to Hdata (n-1, k), a weighted average value given by the following equation is used. Noise immunity and immunity to rapid channel fluctuations can be increased.
[0051]
(Equation 1)

[0052]
According to the various embodiments of the present invention described above, various changes, modifications, and omissions of the scope of the technical idea and viewpoint of the present invention can be easily performed by those skilled in the art. In particular, in the above embodiment, the number of branches is two, but the number of branches may be any number. Further, in the above-described embodiment, the receiver used for the mobile communication of the OFDM system has been described. However, the channel estimation value is sequentially updated using the hard decision result after the amplitude / phase correction in the transmission frame as a replica. The present invention can be applied to any receiving apparatus that performs maximum ratio combining diversity. That is, the above description is merely an example, and is not intended to be limiting. The invention is limited only as defined by the following claims and equivalents thereof.
[0053]
【The invention's effect】
According to the present invention, diversity reception is applied to a method in which a propagation path estimation value estimated from a preamble signal is used as an initial value, and thereafter, a hard path decision of a demodulated OFDM data symbol is used as a replica to update the propagation path estimation value. According to the diversity receiving apparatus, even in the case where the tracking of the channel estimation value fails in the related art, the tracking failure is prevented by maintaining the channel estimation accuracy, without lowering the transmission efficiency. Propagation path estimation is performed, and maximum ratio combining diversity reception becomes possible.
[0054]
Here, in channel estimation, one branch having good transmission quality is selected for each subcarrier, and channel estimation is performed using the hard decision of the branch as a replica. On the other hand, demodulation is performed on the result of performing maximum ratio combining for each subcarrier. Thereby, the accuracy of the channel estimation value can be improved.
[0055]
FIG. 6 is a graph of the bit error rate in the present invention. The graph of FIG. 6 shows the maximum Doppler frequency f _D At a frequency of 200 MHz, which was obtained under the following constituent factors.
[0056]
Modulation method: QPSK, synchronous detection
Information transmission speed: 24 Mbit / s
FFT points: 64
Effective symbol period: 3.2 μs
OFDM symbol period: 4.0 μs
Frame cycle: 2ms
Propagation channel model: Two-wave equal power model
Number of branches: 2 (maximum ratio combining)
[0057]
According to FIG. 6, the conventional configuration not using the diversity of FIG. 1 is compared with the diversity configuration of FIG. 2 and the diversity configuration of FIG. According to this, it is clear that the diversity configuration of FIG. 2 has the best BER characteristics. This is because if an error occurs in the hard decision result used as a replica, the phase error after propagation path distortion correction is amplified, so that it is better to select a hard decision result before combining with higher reliability as a replica, This is considered to be because it is possible to accurately follow the propagation path.
[0058]
According to the present invention, diversity reception is applied to a method for updating a channel estimation value in a frame using a hard decision result of a received information subcarrier as a replica. As a result, by updating the propagation path estimation values of all branches using the hard decision result of the branch with high reliability before the maximum ratio combining as a replica, the BER characteristics can be improved, and a higher quality and stable communication service can be provided. It becomes possible.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a conventional OFDM receiving apparatus that performs channel estimation.
FIG. 2 is a configuration diagram of a first embodiment of the diversity receiver according to the present invention.
FIG. 3 is a configuration diagram of a second embodiment of the diversity receiver according to the present invention.
FIG. 4 is a configuration diagram of a third embodiment of the diversity receiver according to the present invention.
FIG. 5 is a configuration diagram of a fourth embodiment of the diversity receiver according to the present invention.
FIG. 6 is a graph of a bit error rate in the present invention.
FIG. 7 is a configuration diagram of a diversity configuration that obtains hard decisions used for propagation path estimation from a maximum ratio combination result.
[Explanation of symbols]
1, 11, 12 FFT section
2, 21, 22 Amplitude / phase correction unit
3, 31, 32 Hard decision section
4 Remapping unit
5, 51, 52 Channel estimation unit
6 Demodulation unit
7 Hard decision result selector
8 Maximum ratio synthesis section
9 Selective synthesis unit

Claims (16)

Diversity reception comprising receiving means for receiving a time signal for each of a plurality of branches, receiving a transmission frame having a known preamble signal and a data symbol, and using subcarriers in the preamble signal and the data symbol for propagation path estimation A device,
For each of the branches,
FFT means for converting the received time signal into a signal for each subcarrier on a frequency axis;
Channel estimation means for estimating the propagation path for each subcarrier by comparing the post-FFT data for each subcarrier of the symbol output from the FFT means with the data after remapping of the same symbol;
Amplitude / phase correction for correcting the amplitude and phase for each subcarrier based on the channel estimation value for each subcarrier output from the channel estimation means and the output signal for each subcarrier output from the FFT means. Means, and
An output signal for each subcarrier from the FFT means and an amplitude / phase corrected signal from the amplitude / phase correction means for each branch are input, and the amplitude / phase signal corresponding to the output signal having the largest received power of the carrier is input. Selection combining means for selecting a signal after phase correction,
Hard decision means for hard-deciding the signal output from the selective combining means,
Re-mapping means for re-mapping the signal output from the hard decision means and inputting the re-mapped data to the propagation path estimating means for each of the branches. Diversity reception comprising receiving means for receiving a time signal for each of a plurality of branches, receiving a transmission frame having a known preamble signal and a data symbol, and using subcarriers in the preamble signal and the data symbol for propagation path estimation A device,
For each of the branches,
FFT means for converting the received time signal into a signal for each subcarrier on a frequency axis;
Channel estimation means for estimating the propagation path for each subcarrier by comparing the post-FFT data for each subcarrier of the symbol output from the FFT means with the data after remapping of the same symbol;
Amplitude / phase correction for correcting the amplitude and phase for each subcarrier based on the channel estimation value for each subcarrier output from the channel estimation means and the output signal for each subcarrier output from the FFT means. Means, and
The channel estimation unit outputs the channel estimation value for each subcarrier output from the channel estimation unit and the amplitude / phase corrected signal from the amplitude / phase correction unit for each branch, and the phase value is the smallest. Selection synthesis means for selecting a signal after amplitude / phase correction corresponding to the estimated value,
Hard decision means for hard-deciding the signal output from the selective combining means,
Re-mapping means for re-mapping the signal output from the hard decision means and inputting the re-mapped data to the propagation path estimating means for each of the branches. Diversity reception comprising receiving means for receiving a time signal for each of a plurality of branches, receiving a transmission frame having a known preamble signal and a data symbol, and using subcarriers in the preamble signal and the data symbol for propagation path estimation A device,
For each of the branches,
FFT means for converting the received time signal into a signal for each subcarrier on a frequency axis;
Channel estimation means for estimating the propagation path for each subcarrier by comparing the post-FFT data for each subcarrier of the symbol output from the FFT means with the data after remapping of the same symbol;
Amplitude / phase correction for correcting the amplitude and phase for each subcarrier based on the channel estimation value for each subcarrier output from the channel estimation means and the output signal for each subcarrier output from the FFT means. Means,
A hard-decision unit for hard-deciding a signal output from the amplitude / phase correction unit,
An output signal for each subcarrier from the FFT means and a hard decision result signal from the hard decision means for each branch are input, and a hard decision result signal corresponding to an output signal having the largest received power of a carrier is selected. Means for selecting a hard decision result,
Re-mapping means for re-mapping the signal output from the hard decision result selecting means and inputting the re-mapped data to the propagation path estimating means for each branch. Diversity reception comprising receiving means for receiving a time signal for each of a plurality of branches, receiving a transmission frame having a known preamble signal and a data symbol, and using subcarriers in the preamble signal and the data symbol for propagation path estimation A device,
For each of the branches,
FFT means for converting the received time signal into a signal for each subcarrier on a frequency axis;
Channel estimation means for estimating the propagation path for each subcarrier by comparing the post-FFT data for each subcarrier of the symbol output from the FFT means with the data after remapping of the same symbol;
Amplitude / phase correction for correcting the amplitude and phase for each subcarrier based on the channel estimation value for each subcarrier output from the channel estimation means and the output signal for each subcarrier output from the FFT means. Means,
A hard-decision unit for hard-deciding a signal output from the amplitude / phase correction unit,
A propagation path estimation value for each subcarrier output from the propagation path estimation means and a hard decision result signal from the hard decision means for each branch are input, and the phase value corresponds to the smallest propagation path estimation value. A hard decision result selecting means for selecting a hard decision result signal to be re-mapped, and a re-mapping for re-mapping the signal output from the hard decision result selecting means and inputting the re-mapped data to the propagation path estimating means for each of the branches Means for receiving diversity. A plurality of output signals from the amplitude / phase correction unit for each branch, a maximum ratio combination unit for performing maximum ratio combination for each subcarrier,
The diversity receiver according to any one of claims 1 to 4, further comprising demodulation means for demodulating a signal output from the maximum ratio combining means. The propagation path estimating means estimates a propagation path for the preamble signal, using a known preamble signal as a replica and for the data symbol, using a data symbol output from the remapping means as a replica. The diversity receiver according to any one of claims 1 to 5, wherein: The diversity receiver according to any one of claims 1 to 6, wherein the propagation path estimation unit outputs a weighted average of a plurality of estimated values before and after the time. An OFDM receiving apparatus comprising the diversity receiving apparatus according to any one of claims 1 to 7. Diversity reception including a reception step of receiving a time signal for each of a plurality of branches, receiving a transmission frame having a known preamble signal and a data symbol, and using a subcarrier in the preamble signal and the data symbol for propagation path estimation The method,
For each of the branches,
An FFT step of converting the received time signal into a signal for each subcarrier on a frequency axis;
A propagation path estimation step of estimating a propagation path for each subcarrier by comparing the post-FFT data for each subcarrier of the symbol output from the FFT step with the re-mapped data for the same symbol;
Amplitude / phase correction for correcting the amplitude and phase for each subcarrier based on the channel estimation value for each subcarrier output from the channel estimation step and the output signal for each subcarrier output from the FFT step And a step,
An output signal for each subcarrier from the FFT step and an amplitude / phase corrected signal from the amplitude / phase correction step for each branch are input, and the amplitude / phase signal corresponding to the output signal having the largest received power of the carrier is input. A selection synthesis step of selecting a signal after the phase correction,
A hard decision step of hard-deciding the signal output from the selective combining step,
Remapping the signal output from the hard decision step and inputting the re-mapped data to the channel estimation step for each branch. Diversity reception including a reception step of receiving a time signal for each of a plurality of branches, receiving a transmission frame having a known preamble signal and a data symbol, and using a subcarrier in the preamble signal and the data symbol for propagation path estimation The method,
For each of the branches,
An FFT step of converting the received time signal into a signal for each subcarrier on a frequency axis;
A propagation path estimation step of estimating a propagation path for each subcarrier by comparing the post-FFT data for each subcarrier of the symbol output from the FFT step with the re-mapped data for the same symbol;
Amplitude / phase correction for correcting the amplitude and phase for each subcarrier based on the channel estimation value for each subcarrier output from the channel estimation step and the output signal for each subcarrier output from the FFT step And a step,
The channel estimation unit outputs the channel estimation value for each sub-carrier output from the channel estimation step and the amplitude / phase corrected signal from the amplitude / phase correction step for each branch, and the phase value is the smallest. A selection synthesis step of selecting a signal after amplitude / phase correction corresponding to the estimated value,
A hard decision step of hard-deciding the signal output from the selective combining step,
Remapping the signal output from the hard decision step and inputting the re-mapped data to the channel estimation step for each branch. Diversity reception including a reception step of receiving a time signal for each of a plurality of branches, receiving a transmission frame having a known preamble signal and a data symbol, and using a subcarrier in the preamble signal and the data symbol for propagation path estimation The method,
For each of the branches,
An FFT step of converting the received time signal into a signal for each subcarrier on a frequency axis;
A propagation path estimation step of estimating a propagation path for each subcarrier by comparing the post-FFT data for each subcarrier of the symbol output from the FFT step with the re-mapped data for the same symbol;
Amplitude / phase correction for correcting the amplitude and phase for each subcarrier based on the channel estimation value for each subcarrier output from the channel estimation step and the output signal for each subcarrier output from the FFT step Steps and
A hard decision step of hard-deciding the signal output from the amplitude / phase correction step,
An output signal for each subcarrier from the FFT step and a hard decision result signal from the hard decision step for each branch are input, and a hard decision result signal corresponding to an output signal having the largest received power of a carrier is selected. And a re-mapping step of re-mapping the signal output from the hard-decision result selecting step and inputting the re-mapped data to the propagation path estimation step for each branch. Diversity reception method. Diversity reception including a reception step of receiving a time signal for each of a plurality of branches, receiving a transmission frame having a known preamble signal and a data symbol, and using a subcarrier in the preamble signal and the data symbol for propagation path estimation The method,
For each of the branches,
An FFT step of converting the received time signal into a signal for each subcarrier on a frequency axis;
A propagation path estimation step of estimating a propagation path for each subcarrier by comparing the post-FFT data for each subcarrier of the symbol output from the FFT step with the re-mapped data for the same symbol;
Amplitude / phase correction for correcting the amplitude and phase for each subcarrier based on the channel estimation value for each subcarrier output from the channel estimation step and the output signal for each subcarrier output from the FFT step Steps and
A hard decision step of hard-deciding the signal output from the amplitude / phase correction step,
The channel estimation value for each subcarrier output from the channel estimation step and the hard decision result signal from the hard decision step for each branch are input, and the phase value corresponds to the smallest channel estimation value. Hard decision result selecting step of selecting a hard decision result signal to be performed,
Remapping the signal output from the hard decision result selection step, and inputting the re-mapped data to the propagation path estimation step for each branch. A plurality of output signals from the amplitude and phase correction step for each branch, a maximum ratio combining step of maximum ratio combining for each subcarrier,
13. The diversity receiving method according to claim 9, further comprising: a demodulating step of demodulating a signal output from the maximum ratio combining step. The propagation path estimation step is to estimate a propagation path for the preamble signal, using a known preamble signal as a replica, and for the data symbol, using a data symbol output from the remapping step as a replica. The diversity receiving method according to any one of claims 9 to 13, wherein: The diversity receiving method according to any one of claims 9 to 14, wherein the propagation path estimation step outputs a weighted average of a plurality of estimated values before and after the time. An OFDM receiving method comprising the diversity receiving method according to any one of claims 9 to 15.

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