JP4538963B2 - OFDM receiver using diversity adaptive array - Google Patents

Description

【００９９】
ここで、ｉ_maxは１ＯＦＤＭシンボル内のパイロット・シンボル総数であり、ｐ_tx（ｉ）は送信パイロット・シンボル系列であり、ｐ_rx（ｉ）は受信パイロット・シンボル系列である。また、ノルムは、図９に示したように、送信パイロット・シンボルと受信パイロット・シンボルとの距離に相当する。
【０１００】
ノルムの積分結果n_sum［θ₁, θ₂］がダンプされると、あらかじめ設定された閾値との比較、あるいは最急降下法といった収束アルゴリズムを用いて到来波の到来角推定を行う。その結果、到来角推定の判定条件を満たした場合は該当する到来角θ1, θ2を推定結果として更新する。
【０１０１】
図８のリファレンス信号の更新[ａ−４]では、各時刻でダンプされたn_sum［θ₁, θ₂］であるノルム１〜４についてそれぞれ到来角推定を行っており、そのうちノルム１とノルム３について到来角推定の判定条件を満たしたことを示している。この場合、該当する到来角はＤＯＡ１とＤＯＡ３に更新されている。一方、ノルム２については、到来角推定の判定条件を満たさなかったことから前回設定された到来角ＤＯＡ１を用いることを示している。
【０１０２】
到来角が更新された場合、更新された次のタイミングの相関検出実行区間からその値が使用される。図８の[ａ−４]においては、更新されたＤＯＡ１とＤＯＡ３はそれぞれ時刻Ｔ_c（２）並びにＴ_c（４）から使用される。
【０１０３】
リファレンス信号は、設定された到来角ＤＯＡと図８の[ａ−２]で示した１ＯＦＤＭシンボル遅延信号のガード・インターバル区間について生成される。すなわち図７ではＴ_c（ｎ）〜Ｔ_d（ｎ）の区間のＧ_n’について行われる。
【０１０４】
また、リファレンス信号は次のように求めることができる。すなわち、到来波ベクトルをs＝［s₁，s₂］とし、１ＯＦＤＭシンボル遅延した複素ディジタル信号で構成される信号ベクトルをx（ｔ−Ｔ_s）＝［ｘ₁，ｘ₂］、到来波の到来角θ₁, θ₂で表されるステアリング行列をＡとして雑音の影響はないと仮定すると、以下の式が成り立つ。
【０１０５】
【数２】

【０１０６】
また、リファレンス信号をｒ_ref＝ｓ₁とすると、ｓ₁は次式で与えられる。
【０１０７】
【数３】

【０１０８】
このように到来角θ₁, θ₂が決定されると、１ＯＦＤＭシンボル遅延信号を用いてリファレンス信号ｒ_refを計算することができる。
【０１０９】
アダプティブアレー信号処理は相関検出実行区間毎に入力するリファレンス信号を用いて行われる。ここでは、受信信号に対する最適ウエイトＷ_optを計算して重み係数Ｗ₁とＷ₂の更新を行う。例えば、図８においてＴ_d（２）で決定された到来角ＤＯＡ１に対応するリファレンス信号ｒ_refを用いたアダプティブアレー信号処理は、[ａ−５]の区間Ｃ２で行われる。最適ウエイトＷ_optは、複素ディジタル信号で構成される信号ベクトルxから求まる相関行列Ｒ_xx＝Ｅ［ｘ（ｔ）ｘ^H（ｔ）］の逆行列Ｒ_xx ^-1と相関ベクトルｒ_co＝Ｅ［x（ｔ）ｒ_ref ^*（ｔ）］について、それぞれ相関検出実行区間にわたって積分し、１区間分の積分を行った後、すなわちＴ_d（ｎ）のタイミングで次式に従って計算される。
【０１１０】
【数４】

【０１１１】
最適ウエイトＷ_optはアダプティブアレー信号処理が実行されている間は相関検出実行区間Ｔ_c（ｎ）〜 Ｔ_d（ｎ）毎に重み係数の計算が行われ時刻Ｔ_d（ｎ）で更新され、それ以降の重み係数として用いられ複素ディジタル信号に対する重み計算が行われる。このようにして一度更新された最適ウエイトは、次に値が更新されるまで保持される。
【０１１２】
最適ウエイトＷ_optは、アダプティブアレー信号処理が実行されている間は相関検出実行区間Ｔ_c（ｎ）〜 Ｔ_d（ｎ）毎に重み係数の計算が行われ、時刻Ｔ_d（ｎ）で更新され、それ以降の重み係数として用いられ複素ディジタル信号に対する重み計算が行われる。このようにして一度更新された最適ウエイトは、次に値が更新されるまで保持される。
【０１１３】
次に、ダイバーシティ・アダプティブアレー信号処理の動作モードを設定するための処理手順について、図１０に示したフローチャートを参照しながら説明する。ここでは、電源投入時、スリープ・モード直後や同期外れ後の信号の再同期を行う場合を受信開始として、ダイバーシティあるいはアダプティブアレー信号処理といった動作モードの設定と切り替え手順について示している。
【０１１４】
まず、ステップＳ１において、相関検出部２１３は、相関検出を実行して、相関検出情報を未検出として出力する。また、リファレンス信号生成部２１５は、動作を行わず、到来波情報を未検出として出力する。また、ダイバーシティ・アダプティブアレー信号処理部２１６は、各受信系統の複素ディジタル１〜２についてそれぞれ電力測定を行うとともに両者を大小比較して、大きい方をパス選択信号とする。また、動作モードをダイバーシティとして、パス選択情報とともにダイバーシティ・アダプティブアレー制御情報として出力する。
【０１１５】
次いで、ステップＳ２では、同期獲得できたか否かを判別する。同期を獲得できなかった場合は、上述のステップＳ１に復帰する。また、同期獲得できた場合には、後続のステップＳ３に進む。
【０１１６】
ステップＳ３では、相関検出部２１３は、相関検出した初期同期タイミングを基に、ＦＦＴウィンドウ・タイミング情報と相関信号のピーク本数やピーク電力を相関検出情報として出力する。また、リファレンス信号生成制御部５０８は、この相関検出情報を基に、伝搬路環境を推定する。
【０１１７】
次いで、ステップＳ４では、推定された伝搬路がマルチパス環境か否かを判定する。
【０１１８】
伝搬路がマルチパス環境ではないと判定された場合には、ステップＳ５に進ム。この場合、リファレンス信号生成部２１５は、リファレンス信号生成を行い、伝搬路がマルチパス環境でないことを到来波情報として出力する。また、ダイバーシティ・アダプティブアレー信号処理部２１６は、各受信系統からの複素ディジタル信号１〜２についてそれぞれ電力測定を行うとともに両者を大小比較して、大きい方をパス選択情報とする。また、動作モードをダイバーシティとして、パス選択情報とともにダイバーシティ・アダプティブアレー制御情報として出力する。
【０１１９】
他方、伝搬路がマルチパス環境であると判定された場合には、ステップＳ６に進む。この場合、リファレンス信号生成部２１５は、リファレンス信号生成を行い、伝搬路がマルチパス環境であることを到来波情報として出力する。また、ダイバーシティ・アダプティブアレー信号処理部２１６は、動作モードをアダプティブアレーとして信号処理を行い、この動作モードをダイバーシティ・アダプティブアレー情報として出力する。
【０１２０】
次いで、ステップＳ７では、相関検出部２１３は、相関検出した相関信号のピーク本数やピーク電力を相関検出情報として出力する。また、リファレンス信号生成部２１５は、動作モードに拘わらず、ノルム計算部５０２でノルムの計算を行う。また、リファレンス信号生成制御部５００８は、ノルムの計算結果と相関検出情報を基に、伝搬路環境を推定する。
【０１２１】
本明細書では、受信アンテナを２本持つ場合を例にとって説明したが、さらに、３本以上の受信アンテナを用いた場合でも、上述したような２本の受信アンテナによる受信系を受信アンテナ個分に拡張して実現することができる。すなわち、図２に示す受信アンテナ、ＲＦ部、ディジタル変換部、バッファ、重み計算部を受信アンテナに相当する数だけ備え、リファレンス信号生成部とアダプティブアレー処理部では受信アンテナ数分の最適ウエイト設定に必要な計算を行えるようにすれば、同様に本発明の作用効果を相することが可能である。アンテナ数を増やすことで、ダイバーシティ受信はフェージングによる落ち込み区間を受信する確率の低減が図れる。また、アダプティブアレー信号処理は最適ウエイト計算の処理量は増大するが、到来波方向推定可能な到来波数が増加することから分解能の向上を図ることができる。
【０１２２】
［追補］
以上、特定の実施例を参照しながら、本発明について詳解してきた。しかしながら、本発明の要旨を逸脱しない範囲で当業者が該実施例の修正や代用を成し得ることは自明である。すなわち、例示という形態で本発明を開示してきたのであり、限定的に解釈されるべきではない。本発明の要旨を判断するためには、冒頭に記載した特許請求の範囲の欄を参酌すべきである。
【０１２３】
【発明の効果】
以上詳記したように、本発明によれば、装置ブロック構成を変えないで、効率的に到来波分布から伝搬路推定できるようにし、伝搬路環境がマルチパスの場合はアダプティブ信号処理を行い、他の伝搬環境の場合は選択ダイバーシティを切り替えて行なえるようにしたダイバーシティ・アダプティブアレーを用いた、優れたＯＦＤＭ受信装置を提供することができる。
【０１２４】
本発明に係るダイバーシティ・アダプティブアレーを用いたＯＦＤＭ受信装置によれば、ダイバーシティとアダプティブアレー信号処理を共通のブロック構成により実現することができ、装置構成を簡素化することができる。
【０１２５】
また、本発明に係るダイバーシティ・アダプティブアレーを用いたＯＦＤＭ受信装置によれば、伝搬路状況に応じてダイバーシティとアダプティブアレー信号処理を切り替えて行うことができ、マルチパスによる劣化の問題を解消することができる。
【図面の簡単な説明】
【図１】ＯＦＤＭ信号を送信するＯＦＤＭ送信装置の一例の概略構成を示した図である。
【図２】本発明の１つの実施形態に係るダイバーシティ・アダプティブアレーを用いたＯＦＤＭ受信装置２００の構成を概略的に示した図である。
【図３】本発明の１つの実施携帯に係るダイバーシティ・アダプティブアレーを用いたＯＦＤＭ受信装置２００の構成要素であるダイバーシティ・アダプティブアレー信号処理部２１６の概略的な構成を示した図である。
【図４】本発明の１つの実施形態に係るダイバーシティ・アダプティブアレーを用いたＯＦＤＭ受信装置２００の構成要素である積分ダンプ部の概略的な構成を示した図である。
【図５】本発明の１つの実施形態に係るダイバーシティ・アダプティブアレーを用いたＯＦＤＭ受信装置２００の構成要素であるリファレンス信号生成部２１５の概略的な構成を示した図である。
【図６】本発明の１つの実施形態に係るダイバーシティ・アダプティブアレーを用いたＯＦＤＭ受信装置２００の構成要素である選択合成部２１１の概略的な構成を示した図である。
【図７】本発明の１つの実施形態に係るアダプティブアレーを用いたＯＦＤＭ受信装置２００における電力測定タイミング例を示した図である。
【図８】本発明の１つの実施形態に係るアダプティブアレーを用いたＯＦＤＭ受信装置２００におけるアダプティブアレー信号処理タイミング例を示した図である。
【図９】本発明の１つの実施形態に係るアダプティブアレーを用いたＯＦＤＭ受信装置２００におけるノルムのイメージを示した図である。
【図１０】本発明の１つの実施形態に係るアダプティブアレーを用いたＯＦＤＭ受信装置におけるダイバーシティ・アダプティブアレー信号処理の動作モードの設定手順を示したフローチャートである。
【符号の説明】
１００…ＯＦＤＭ信号送信装置
１０１…変調部，１０２…パイロット・シンボル挿入部
１０３…シリアル／パラレル変換部，１０４…ＩＦＦＴ部
１０５…ガード区間挿入部，１０６…アナログ変換部
１０７…ＲＦ部，１０８…送信アンテナ
１０９…送信制御部
２０１，２０２…受信アンテナ
２０３，２０４…ＲＦ部
２０５，２０６…ディジタル変換部
２０７，２０８…バッファ
２０９，２１０…重み計算部
２１１…選択合成部、２１２…ＦＦＴ部
２１３…相関検出部、２１４…復調部
２１５…リファレンス信号生成部
２１６…ダイバーシティ・アダプティブアレー信号処理部
３０１…ベクトル生成部、３０２…相関行列計算部
３０３…積分ダンプ部、３０４…逆行列計算部
３０５…相関ベクトル計算部、３０６…積分ダンプ部
３０７…重み決定部、３０８…電力測定部
３０９…比較部
３１０…ダイバーシティ・アダプティブアレー信号処理制御部
４０１…セレクタ、４０２…ゲイン部
４０３…遅延部、４０４…加算部、４０５…記憶部
５０１…パイロット信号生成部、５０２…ノルム計算部
５０３…積分ダンプ部、５０４…比較部
５０５…ＤＯＡ設定部、５０６…遅延部
５０７…リファレンス信号計算部
５０８…リファレンス信号生成部
６０１…加算部、６０２…選択部
６０３…セレクタ、６０４…選択合成部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an OFDM (Orthogonal Frequency Division Multiplexing) type receiving apparatus in which the frequency of each carrier is set so that each carrier is orthogonal to each other within a symbol interval, and in particular, correlation between signals. The present invention relates to an OFDM receiver that performs diversity reception using signals received by a plurality of antennas arranged so as to be small.
[0002]
More particularly, the present invention relates to an OFDM receiving apparatus that is configured to be small by performing selective diversity reception that selectively uses a received signal having the strongest signal power among a plurality of received signals. The present invention relates to an OFDM receiving apparatus using a diversity adaptive array that performs adaptive array signal processing for removing interference waves when the environment is multipath, and can switch the selected diversity when the propagation environment is other.
[0003]
[Prior art]
In recent years, the spread and demand of mobile communications such as mobile phones and vehicle-mounted phones have been remarkably progressing. Now everyone is using mobile communication devices and being recognized as a necessity in social life.
[0004]
When wireless transmission is performed in a mobile propagation environment, deterioration of transmission quality due to fading and multipath becomes a particular problem.
[0005]
The “OFDM (Orthogonal Frequency Division Multiplexing) system” is expected as a technique for realizing high speed and high quality wireless transmission. The OFDM scheme is a type of multicarrier transmission scheme, and the frequency of each carrier is set so that the carriers are orthogonal to each other within a symbol interval. An example of information transmission is to perform serial-to-parallel conversion of data sent serially for each symbol period slower than the information transmission rate, and to assign a plurality of data to each carrier for modulation for each carrier. By performing inverse FFT on the carrier, it is converted into a signal on the time axis and transmitted while maintaining the orthogonality of each carrier on the frequency axis. For example, if each carrier performs BPSK (Binary Phase Shift Keying) modulation and serial / parallel conversion is performed at a symbol period of 1/256 of the information transmission rate, the total number of carriers becomes 256, and inverse FFT is performed on 256 carriers. Demodulation is the reverse operation, that is, FFT is performed to convert the time-axis signal into a frequency-axis signal, and demodulation corresponding to each modulation method is performed for each carrier, and parallel / serial conversion is performed on the original serial signal. This is done by reproducing the sent information. It has been experimentally confirmed that the OFDM transmission system has good transmission characteristics even when there is a delayed wave.
[0006]
Transmission by the OFDM scheme has a characteristic that anti-fading characteristics are strong against multipath fading and selective fading with a large delay time difference of incoming waves, because the period of one symbol is longer than the single carrier transmission scheme having the same transmission capacity. . However, when the delay time of the disturbing wave with respect to the main wave exceeds a guard interval in a multipath composed of a plurality of incoming waves, or when the power ratio (D / U) between the main wave and the disturbing wave is large, the demodulated signal There is also a problem that the error rate of the demodulated signal deteriorates even for flat fading with a small difference in delay time of incoming waves.
[0007]
In order to solve the deterioration due to multipath, adaptive array signal processing for removing interference waves is effective. On the other hand, in order to solve the deterioration due to flat fading, diversity reception using signals received by a plurality of antennas arranged so as to reduce the correlation between signals is effective. The main methods include selection diversity for selecting the received signal having the strongest signal power among the plurality of received signals, maximum ratio combining diversity for demodulating each of the plurality of received signals and performing maximum ratio combining.
[0008]
In comparison with the device scale, the former selection diversity requires only one reception system after selecting a received signal, but the latter maximum ratio combining diversity increases because a plurality of reception systems until demodulation are required. Further, when compared with the diversity gain, the former selection diversity is deteriorated by about 2 dB as compared with the latter maximum ratio combining diversity. For this reason, when performing diversity reception, it is necessary to determine whether the former or the latter is better in terms of the desired device scale and diversity gain.
[0009]
[Problems to be solved by the invention]
An object of the present invention is to provide an excellent OFDM receiving apparatus that is configured in a small size by performing selective diversity reception that selectively uses a received signal having the strongest signal power among a plurality of received signals. .
[0010]
A further object of the present invention is to make it possible to efficiently estimate the propagation path from the incoming wave distribution without changing the apparatus block configuration. When the propagation path environment is multipath, adaptive signal processing is performed. In this case, it is an object to provide an excellent OFDM receiving apparatus using a diversity adaptive array that can be switched by selecting diversity.
[0011]
[Means and Actions for Solving the Problems]
The present invention has been made in consideration of the above-mentioned problems. The first aspect of the present invention is to propagate an OFDM (orthogonal frequency division division) signal including pilot symbols received by a plurality of antennas based on the arrival wave distribution. Propagation path estimation means for estimating the path;
Based on the propagation path estimation result, a propagation path environment is determined. When the propagation path environment is multipath, adaptive signal processing is performed. Signal processing means for performing signal processing by switching; and
An OFDM receiver using a diversity adaptive array.
[0012]
According to the OFDM receiver using the diversity adaptive array according to the first aspect of the present invention, the operation mode is dynamically switched based on the propagation path environment, and the adaptive signal is used when the propagation path environment is multipath. In the case of other propagation path environments, signal processing can be performed by switching a receiving apparatus having a block with a common selection diversity.
[0013]
A second aspect of the present invention is an OFDM receiver using selective diversity that selectively uses a plurality of OFDM (Orthogonal Frequency Division Division) received signals,
A receiving antenna, an RF unit for downconverting a signal received via the receiving antenna from an RF frequency band to a baseband signal, and digital conversion for converting the downconverted baseband signal into a complex digital signal by A / D conversion A plurality of receiving systems each including a part,
A weight calculator for weighting the complex digital signal when performing adaptive signal processing;
When performing diversity, one is selected from complex digital signals from each receiving system, and when performing adaptive signal processing, a selection combining unit that adds each complex digital signal weighted by the weight calculation unit;
An FFT unit that generates a received symbol of a parallel carrier by performing a Fourier transform of one period of an OFDM symbol on a complex digital signal output from the selection combining unit according to a predetermined FFT window timing;
Correlation detection is performed on the complex digital signal output from the selection / synthesis unit using the guard interval signal, and correlation detection information including FFT window timing information, number of correlation signal peaks, peak power, etc. is output. And
A demodulator that demodulates received symbols of parallel carriers corresponding to each receiving system;
The pilot symbol is extracted from the received symbols for each of the OFDM subcarriers for several parallel carriers output by the FFT unit, the propagation path is estimated, and the arrival angle of the incoming wave based on the pilot symbol is estimated, A reference signal generator that generates a reference signal corresponding to an incoming wave with strong signal power and a complex digital signal from each receiving system are each measured for power and compared in magnitude to find the complex digital signal with the highest power. A diversity adaptive array signal processing unit that calculates an optimum weighting factor for a received signal in each receiving system based on the reference signal and the extracted complex digital signal;
An OFDM receiver using a diversity adaptive array.
[0014]
Here, when performing adaptive signal processing, the weight calculation unit weights and adds the complex digital signal from each reception system using the optimum weight coefficient calculated by the diversity adaptive array signal processing unit. Then, the addition result is output as a composite complex digital signal to the correlation detection unit and the FFT unit. The correlation detection unit performs correlation detection using a repetitive pattern of the guard interval section, generates correlation detection information including FFT window timing information, the number of peaks of the correlation signal, peak power, and the like, and the FFT The window timing information is output to the FFT unit, and the correlation detection information is output to the reference signal generation unit. The FFT unit performs a Fourier transform for each OFDM symbol according to the FFT window timing information to generate a reception symbol of a parallel carrier, and outputs the received symbol to the demodulation unit and the reference signal generation unit. The demodulator demodulates each received symbol of the parallel carrier. The reference signal generator extracts a pilot symbol from a plurality of received symbols of the parallel carrier, generates the same sequence as the pilot symbol sequence at the time of transmission, and calculates a norm for each received symbol based on the difference between the two. Calculate and estimate the arrival angle of the incoming wave based on the integrated norm integral value, generate a reference signal based on the estimated value and the complex digital signal, and send it to the diversity adaptive array signal processing unit. Output. The diversity adaptive array signal processing unit calculates a weighting factor based on the complex digital signal and the reference signal for each guard interval section, and outputs the weighting factor to the weight calculating unit.
[0015]
On the other hand, when performing diversity, the diversity adaptive array signal processing unit performs power measurement on each of the complex digital signals from each receiving system and compares them to determine the complex digital signal having the highest power. It outputs to the said selection synthetic | combination part as path selection information. The selection / combination unit selects only one complex digital signal according to path selection information for the complex digital signal not weighted by the weight calculation unit. Then, FFT, demodulation, and correlation detection are performed on the complex digital signal.
[0016]
Therefore, according to the OFDM receiver using the diversity adaptive array according to the second aspect of the present invention, both diversity and adaptive array signal processing can be realized by a common block configuration, thus saving the scale of the device. can do.
[0017]
In addition, the reference signal generation unit is based on the correlation detection information input from the correlation detection unit, the power measurement information input from the diversity adaptive array signal processing unit, and the norm integral value for each received symbol, based on the OFDM symbol unit To determine a propagation path parameter consisting of the number of arrival waves, arrival wave power, time variation of power fluctuation, etc., estimate the propagation path condition based on the propagation path parameter, and perform either adaptive array signal processing or diversity according to the estimation result Therefore, it is possible to switch between diversity and adaptive array signal processing in accordance with the propagation path condition.
[0018]
In addition, when the reference signal generation unit switches the operation mode to diversity and determines that synchronization is not established from the correlation detection information input from the correlation detection unit, each reference signal generation unit receives each reception at a preset integration cycle or timing. While measuring the power of the complex digital signal from the system and comparing the magnitude of each power measurement result, the larger value is selected and output to the correlation detection unit to perform correlation detection, while synchronization is acquired. Since estimation of the propagation path condition is started later and the operation mode is switched to adaptive array signal processing or diversity, the efficiency of signal processing up to acquisition of synchronization can be improved.
[0019]
Further, the reference signal generation unit, when the operation mode is diversity, the correlation detection information input from the correlation detection unit, the power measurement information input from the diversity adaptive array signal processing unit, and the norm integral value for each received symbol Based on the above, the power measurement period and measurement timing are determined, and whenever these change, the power of the complex digital signal is measured whenever necessary, so the diversity power measurement is performed according to the condition of the propagation path. Can be done.
[0020]
Further, when the operation mode is changed, the reference signal generation unit continuously performs signal processing in the operation mode before the change until the boundary of the OFDM symbol immediately after that, and outputs a demodulated symbol of the parallel carrier. Since the operation is performed in the changed operation mode after the boundary, the OFDM symbol can be demodulated without interruption of the data series even when the operation mode is switched.
[0021]
Other objects, features, and advantages of the present invention will become apparent from a more detailed description based on embodiments of the present invention described later and the accompanying drawings.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0023]
Before describing an OFDM receiver using a diversity adaptive array according to the present invention, a schematic configuration of an example of an OFDM transmitter that transmits an OFDM signal will be described with reference to FIG.
[0024]
As shown in FIG. 1, an OFDM signal transmission apparatus 100 includes a modulation unit 101, a pilot symbol insertion unit 102, a serial / parallel conversion unit 103, an IFFT unit 104, a guard interval insertion unit 105, and an analog conversion unit. 106, an RF unit 107, a transmission antenna 108, and a transmission control unit 109.
[0025]
When receiving transmission data, modulation section 101 performs modulation according to the modulation information and timing supplied from transmission control section 109, and outputs modulation symbols serially.
[0026]
Pilot symbol insertion section 102 inserts a known data sequence into the modulation symbol sequence as a pilot symbol according to the pilot symbol insertion pattern and timing input from transmission control section 109.
[0027]
The serial / parallel converter 103 converts serial data into parallel data corresponding to the number of parallel carriers according to the number and timing of parallel carriers input from the transmission controller 109.
[0028]
The IFFT unit 104 performs an inverse Fourier transform for the FFT size according to the FFT size and timing input from the transmission control unit 109.
[0029]
The guard interval insertion unit 105 inserts guard signals such as a guard interval and a guard band according to the guard interval size, guard band size, and timing input from the transmission control unit 109.
[0030]
The digital transmission signal with the guard signal inserted is subjected to quadrature modulation and A / D conversion by the analog conversion unit 106, up-converted by the transmission RF unit 107, and transmitted from the transmission antenna 108.
[0031]
An OFDM receiver using a diversity adaptive array according to the present invention can receive, for example, an OFDM signal transmitted from the OFDM transmitter 100 described above. In the following, an OFDM receiver to which the diversity adaptive array according to the present invention is applied, and the apparatus configuration and its operating characteristics when two receive antennas of the OFDM receiver are used will be described with reference to the drawings. .
[0032]
FIG. 2 schematically shows a configuration of an OFDM receiving apparatus 200 using a diversity adaptive array according to one embodiment of the present invention.
[0033]
The OFDM receiving apparatus 200 using the present diversity adaptive array shown in the figure has two receiving antennas, and adopts a ULA configuration in which each is separated by a half wavelength of the carrier frequency. Therefore, when the incoming wave is a plane wave, the incoming angle θ₁, Θ₂The two incoming waves can be separated. In addition, selection diversity using two antennas can be performed.
[0034]
In FIG. 2, reference numerals 201 and 202 are receiving antennas. The signals received by the receiving antennas are down-converted from the RF frequency band to the baseband signal by the RF units 203 and 204, respectively.
[0035]
The digital conversion units 205 and 206 convert the analog baseband signals down-converted by the RF units 203 and 204 into complex digital signals using an A / D converter and a quadrature detector, and output the complex digital signals.
[0036]
The buffers 207 and 208 temporarily store the complex digital signals output from the digital conversion units 205 and 206, respectively, and output them at appropriate timing.
[0037]
The weight calculators 209 and 210 do not process the complex digital signals input from the buffers 207 and 208 when performing diversity. On the other hand, when performing adaptive array signal processing, a weighting factor W set by a diversity and adaptive array signal processing unit 216 (described later).₁, W₂And a complex multiplication of each complex digital signal and output the result.
[0038]
The selection combining unit 211 selects a complex digital signal determined to be optimal from the above-described two reception systems according to diversity adaptive array information sent from the diversity adaptive array signal processing unit 216 (described later) during diversity, When adaptive array signal processing is performed, the weighted complex digital signals input from the weight calculation units 209 and 210 are added.
[0039]
The FFT unit 212 performs Fourier transform on the selectively synthesized complex digital signal input from the selection synthesis unit 211 and outputs received symbols for the number of parallel carriers.
[0040]
The correlation detection unit 213 performs correlation detection on the selectively synthesized complex digital signal input from the selection synthesis unit 211, and outputs FFT window timing information and a correlation detection result.
[0041]
Demodulation section 214 demodulates the received symbols for the number of parallel carriers input from FFT section 212 and outputs demodulated data.
[0042]
The reference signal generation unit 215 extracts pilot symbols from the reception symbols for the number of parallel carriers input from the FFT unit 212, and estimates an arrival angle (DOA: Direction Of Array) of the arrival wave based on the pilot symbols. Then, a reference signal serving as a reference for adaptive array signal processing is generated.
[0043]
Diversity / adaptive array signal processing section 216 operates based on correlation detection information sent from correlation detection section 213 and arrival wave detection information input from reference signal generation section 215. More specifically, when diversity is performed, the power of each of the complex digital signals input from the buffers 207 and 208 is measured for a predetermined period, compared, and the path with the larger power selected is selected. Information. When adaptive array signal processing is performed, an optimum weight coefficient for each received signal from each antenna 201, 202 is calculated from the reference signal and the complex digital signal, and each optimum weight coefficient W is calculated.₁, W₂In addition, control information such as the above path selection information, diversity, or adaptive array signal information is output as adaptive array control information.
[0044]
The operation characteristics of the OFDM receiver using the diversity adaptive array configured as described above will be described below.
[0045]
Signals received by the reception antennas 201 and 202 are converted into baseband signals by the RF units 203 and 204, and then output to the digital conversion units 205 and 206.
[0046]
The digital conversion units 205 and 206 generate baseband complex digital signals corresponding to the reception antennas 201 and 202 by the A / D converter and the quadrature detection unit, and output them to the buffers 207 and 208, respectively.
[0047]
The baseband complex digital signals stored in the buffers 207 and 208 are input to the weight calculation units 209 and 210, the reference signal generation unit 215, and the diversity and adaptive array signal processing unit 216 according to the respective output timings.
[0048]
When performing the diversity, the weight calculation units 209 and 210 do not process the complex digital signals input from the buffers 207 and 208, respectively. When adaptive array signal processing is performed, the respective weighting factors W calculated by the diversity adaptive array signal processing unit 216 for each of the complex digital signals 1 and 2 input from the respective buffers 207 and 208 are used.₁, W₂Are output as complex digital signals 1 ′ and 2 ′.
[0049]
In the case of performing diversity according to the diversity / adaptive array information sent from the diversity / adaptive array selection unit 216, the selection / combination unit 211 uses the diversity / adaptive array signal processing unit 216 based on the power measurement results of the complex digital signals 1-2. One of the complex digital signals 1 ′ or 2 ′ determined to have a large received power is selected. Further, when adaptive array signal processing is performed, the baseband complex digital signals 1 ′ and 2 ′ input from the respective weight calculation units 209 and 210 are added and output as a selectively synthesized complex digital signal.
[0050]
The complex digital signal thus selected and synthesized is subjected to Fourier transform each time one OFDM symbol period is input by the FFT unit 212 to generate reception symbols for the number of parallel carriers, and the demodulation unit 214 and the reference signal generation unit 215. Is output. The demodulator 214 performs demodulation for each carrier and outputs demodulated data.
[0051]
Further, the complex digital signal that has been selected and synthesized is subjected to correlation detection by using a repetitive pattern of the guard interval section in the correlation detection unit 213, and FFT window timing information, the number of correlation signal peaks, the peak power, etc. Correlation detection information is generated. The former FFT window timing information is input to the FFT unit 212, and the latter correlation detection information is input to the reference signal generation unit 215.
[0052]
After the synchronization is established and the FFT starts to operate normally, the reference signal generation unit 215 extracts pilot symbols from the received symbols for the number of parallel carriers, and the pilot symbol sequence inserted by the transmission apparatus The same series is generated, the norm is calculated based on the difference between the two, and integration is performed for the norm of one OFDM symbol. Based on the norm calculation result and the correlation detection information sent from the correlation detection unit 213, propagation path estimation is performed such as whether or not the propagation path is a multipath environment. As a result of propagation path estimation, when it is determined that the environment is a multipath environment, an arrival angle (DOA: Direction Of Array) of an incoming wave is estimated for each OFDM symbol based on the integral value, and the estimated value and each A reference signal corresponding to an incoming wave having the strongest power is generated based on a signal obtained by delaying the complex digital signal input from the buffers 207 and 208 by one OFDM symbol period. On the other hand, if it is determined that the environment is not a multipath environment, the above-described DOA estimation and reference signal generation are not performed.
[0053]
Incoming wave information such as the reference signal and the above-described propagation path estimation result and reference signal generation status is output to the diversity and adaptive array signal processing unit 216.
[0054]
Diversity / adaptive array signal processing section 216 performs integral dumping of power for each complex digital signal input from buffers 207 and 208 for a predetermined period. When it is determined as a flat fading environment based on the arrival wave information input from the reference signal generation unit 215 and the power measurement result, the power measurement result is compared, and the received power from the above two receiving systems is compared. The comparison information, such as selecting the larger one, is determined. If the multipath environment is determined, a correlation matrix R for a portion corresponding to the guard interval section of the complex digital signal is obtained._xxAnd its inverse R_xx ^-1On the basis of the reference signal and the complex digital signal input from the reference signal generation unit 215_coAnd the inverse matrix R_xx ^-1And correlation matrix R_xxOptimal weight W by taking the product of_optCalculate The optimum weight is the weighting factor W₁, W₂Is output to each of the weight calculation units 209 and 210 and updated for each guard interval section.
[0055]
The signal processing by the diversity adaptive array according to the present embodiment is performed by the diversity adaptive array signal processing unit 216, the integral dump unit 303, and the reference, which are schematically shown in FIGS. 3, 4, 5, and 6. This is realized by a cooperative operation in each function module of the signal generation unit 215 and the selection synthesis unit 211. Hereinafter, a schematic configuration and operation characteristics of each functional module will be described with reference to the drawings.
[0056]
FIG. 3 is a block diagram showing a schematic configuration of the diversity / adaptive array signal processing unit 216.
[0057]
In the figure, reference numeral 301 denotes a vector generation unit that converts the complex digital signals 1 and 2 input from the buffers 207 and 208 into vector types.
[0058]
Reference numeral 302 is a correlation matrix R from a vector-type complex digital signal input from the vector generation unit 301._xxIs a correlation matrix calculation unit.
[0059]
Reference numeral 303 is a correlation matrix R._xxIs an integration dump unit that performs integral dumping according to the gain, the number of integrations, integration, and dump timing sent from the diversity adaptive array signal control unit 310.
[0060]
Reference numeral 304 is a correlation matrix R sent from the integral dump unit 303._xxTo its inverse R_xx ^-1Is an inverse matrix calculation unit.
[0061]
Reference numeral 305 is a correlation vector r based on the vector-type complex digital signal and the reference signal input from the diversity adaptive array signal processing unit 216._coIs a correlation vector calculation unit.
[0062]
Reference numeral 306 indicates the correlation vector r._co Is an integration dump unit that performs an integral dump according to the gain, the number of integrations, the integration, and the dump timing sent from the adaptive array signal control unit 310.
[0063]
Reference numeral 307 indicates the optimum weight W corresponding to the received signal received by each receiving antenna 201, 202._optIs a weight determination unit for calculating.
[0064]
Reference numeral 308 denotes a power measurement unit that measures the power of the vector-type complex digital signal input from the vector generation unit 301 at each power measurement period transmitted from the diversity adaptive array signal processing unit 310.
[0065]
Reference numeral 309, when performing diversity, compares the power measurement results of vector-type complex digital signals, selects the receiving antenna 201 or 202 having the higher power, and uses the result as the path selection information. As a comparison unit that outputs to the diversity adaptive array signal processing control unit 310.
[0066]
The diversity adaptive array signal processing control unit 310 controls the coefficient and operation timing of each block based on the incoming wave detection information input from the reference signal generation unit 215, and controls the above path selection information and power measurement result. Information is output to other functional modules as diversity / adaptive array control information.
[0067]
FIG. 4 shows a schematic configuration of the integral dump units 303 and 306 in FIG. Reference numeral 401 in the figure is a selector that selects 0 in the case of reset or dump timing sent as a control signal, and selects data input from the gain unit 402 in other cases.
[0068]
The gain unit 402 amplifies the data input from the delay unit 403 with the gain setting value sent by the control signal. The delay unit 403 stores data input from the adder unit 404.
[0069]
The adder 404 adds the data sent from the selector 401 and the input data sent from the outside.
[0070]
The storage unit 405 latches the data sent from the adding unit 404 according to the dump timing sent as the control signal, and outputs a dump value.
[0071]
FIG. 5 shows a schematic configuration of the reference signal generation unit 215 shown in FIG. The reference number 501 in the figure is the same sequence p as the pilot symbol sequence generated by the pilot symbol insertion unit 102 of the OFDM transmitter (see FIG. 1)._txIs a pilot signal generator for generating
[0072]
Reference numeral 502 denotes a transmission pilot symbol sequence p generated by pilot signal generation section 501._txAnd the received pilot symbol sequence p extracted from the received symbols input from the FFT unit 212_rxIt is a norm calculation part which calculates the norm of.
[0073]
Reference numeral 503 denotes an integration dump unit that performs integral dumping according to a gain, the number of integrations, integration, and dump timing sent from a reference signal generation control unit 509 (described later).
[0074]
Reference numeral 504 denotes a comparison unit that compares the norm integration result input from the integration dump unit 503 with the arrival wave direction determination threshold value sent from the reference signal generation control unit 509.
[0075]
The reference number 505 is based on the comparison result in the comparison unit 504, and the incoming wave direction DOA [θ₁, Θ₂] Is a direction-of-arrival setting unit that sets a value of
[0076]
Reference numeral 506 is a delay unit that stores the complex digital signals 1 and 2 input from the buffers 207 and 208 and outputs them according to the timing sent from the reference signal generation control unit 509.
[0077]
The reference number 507 is the arrival wave direction DOA [θ [θ] input from the arrival direction setting unit 505 described above.₁, Θ₂] And a reference signal calculation unit that generates a reference signal based on the complex digital signals 1 and 2 sent from the delay unit 506.
[0078]
Reference numeral 508 denotes a reference signal generation control unit, and diversity adaptive array information such as correlation detection information input from the correlation detection unit 213 and power measurement result of the complex digital signal input from the diversity adaptive array signal processing unit 216, Based on the propagation path information such as whether or not a multipath environment is obtained from the norm calculation value input to the norm production unit 502 shell, the coefficient and operation timing of each block is controlled, or the arrival direction estimation presence / absence and estimation accuracy are received. Outputs information such as wave detection information.
[0079]
FIG. 6 shows a schematic configuration of the selection / synthesis unit 211. In the figure, reference numeral 601 denotes an adding unit that adds the complex digital signals 1 ′ and 2 ′ input from the respective weight calculation units 209 and 210 when adaptive array signal processing is performed.
[0080]
Reference numeral 602 is a selection for selecting one of the above-described complex digital signals 1 ′ and 2 ′ based on a selection signal sent from the selection / synthesis control unit 604 when diversity is performed. Part.
[0081]
Reference numeral 603 outputs a signal added by the adder 601 when adaptive array signal processing is performed, and outputs a signal selected by the selector 602 when diversity is performed. It is a selector to do.
[0082]
Next, the operation characteristics of the diversity adaptive array signal processing unit 216 and the reference signal generation unit 215 configured as described above will be described.
[0083]
FIG. 7 shows an example of diversity signal processing timing when diversity is performed. FIG. 8 shows an example of signal processing timing by an adaptive array when adaptive array signal processing is performed.
[0084]
In the following description, the configuration of the OFDM signal in the present embodiment is the OFDM symbol D as shown by the complex digital signal in FIGS._nAnd guard interval G, which is a sample of the latter half of the OFDM symbol copied by the guard interval_nEach with G_n, D_n(Where n = 1, 2,..., N). Where T_gIs the guard interval length [sec], and T_sIs one period [sec] of the OFDM symbol. In these timing examples, there is no clock error between transmission and reception and no frequency offset.
[0085]
Diversity signal processing is performed when the operation mode is diversity. The example of power measurement timing shown in FIGS. 7A to 7D is the selection diversity performed using the power measurement unit 308 and the comparison unit 309 in the diversity adaptive array signal processing unit 216 shown in FIG. It shows about the process of obtaining the path selection information.
[0086]
FIG. 7A shows the power measurement timing at the time of initial synchronization. Since the correct FFT window is not detected at the time of initial synchronization, the integration period and integration timing are represented by T in FIG._d(1) to T_dAs shown in (2), power measurement and comparison are performed using a predetermined initial value, and path selection information in selection diversity performed using the power measurement unit 308 and the comparison unit 309 is obtained. Based on this path selection information, the selector 602 selects the received signal having the larger power measurement result from the complex digital signal 1 ′ or 2 ′, and the selector 603 selects and synthesizes the complex signal. Output a digital signal.
[0087]
When the synchronization acquisition is successful, the synchronization detection information is output from the correlation detection unit 213 to the reference signal generation unit 215. As a result, the power measurement timing is represented by T in FIG._d(3) to T_dAs shown in (5), it is changed so as to coincide with the boundary of the FFT window. Thereafter, power measurement is performed from the top of the FFT window. The power measurement timing of the power measurement unit 308 in this process is as indicated by c1 to c5 in FIG.
[0088]
FIG. 7B shows the power measurement timing when the FFT size is changed. Here, it is assumed that power measurement is performed for the OFDM signal period, and that the FFT size switching timing is known.
[0089]
In the example shown in FIG._d(N) to T_dThe signal transmitted in the OFDM signal period 1 corresponding to the interval (n + 1) is twice the FFT size T_d(N + 2) to T_dThis shows that switching to the OFDM signal period 2 having (n + 4) is performed. More specifically, T_d(0) to T_d(1) and T_d(1) to T_d(2) corresponds to the OFDM symbol before FFT size switching, and T_d(2) to T_d(4) and T_d(4) to T_d(6) corresponds to the OFDM symbol after switching.
[0090]
The power measurement timing is the beginning of the next OFDM signal period from which the FFT size switching information is obtained, that is, T in FIG._d(2) From then on, power measurement that has been performed in the OFDM signal period 1 until then is performed in the section of the OFDM signal period 2. The power measurement timing in this process is as indicated by c1 to c4 in FIG.
[0091]
FIG. 7C shows the power measurement timing for removing the guard interval. If a long guard interval is set, such as 1/4 of the OFDM signal period, or if the transmission quality varies greatly, it is more accurate to remove the power in the guard interval section outside the FFT window from the integration range. Power measurements can be made. In the example shown in FIG. 7C, the power measurement is switched from the cycle including the guard interval to the cycle in which the guard interval portion is removed.
[0092]
In the complex digital signal shown in FIG._d(0) to T_dIn the section shown in (2), power measurement including a guard interval is performed, and T_d(2) to T_dIn the section shown in (5), power measurement is performed excluding the guard interval. In the example shown in the figure, a reset signal is set in a portion corresponding to the guard interval. The power measurement timing in this process is as shown by c1 to c4 in FIG.
[0093]
FIG. 7D shows an example of power measurement timing using transmission quality information in a flat fading environment. The power measurement in this case shows a process of switching the power measurement period at an arbitrary timing in the case shown in FIG. 7C, and is effective in a flat fading environment without frequency distortion. In the complex digital signal shown in FIG._d(0) to T_dIn the section shown in (2), power measurement is performed in one OFDM signal period, followed by T_d(2) to T_dIn the section shown in (5), power measurement is performed in half the OFDM signal period. This corresponds to a case where the Doppler frequency is changed from small to large in flat fading. The integration cycle timing of the integration dump unit in this process is as indicated by c1 to c9 in FIG.
[0094]
On the other hand, the adaptive array signal processing is executed when the operation mode is an adaptive array.
[0095]
When the complex digital signal [a-1] is received, a 1 OFDM symbol delayed signal like [a-2] is generated by the delay unit. When [a-1] and [a-2] are correlated, T_c(N) to T_dSince both have the same pattern in the section (n), correlation detection can be performed. In the correlation detection unit 213, this section T_c(N) to T_dCorrelation detection is performed using (n) as a correlation detection execution section, and correlation detection information such as FFT window timing information, the number of correlation signal peaks, and the peak power is obtained.
[0096]
The norm integral [a-3] is the interval T_d(N-1) to T_d(N) at time T_dThe integral value is dumped at (n). In the example shown in FIG. 8, the norm is calculated every time, but the norm is calculated after initial synchronization is acquired according to the information from the correlation detection unit 213, or the situation such as multipath detection and fluctuation of the arrival angle of the incoming wave is observed. It is not necessary to always calculate the norm because it is performed when
[0097]
Assuming two-wave multipath, each angle of arrival is θ₁, Θ₂The integrated value n_sum [θ₁, θ₂] Is given by the following equation.
[0098]
[Expression 1]

[0099]
Where i_maxIs the total number of pilot symbols in one OFDM symbol, p_tx(I) is a transmission pilot symbol sequence, p_rx(I) is a received pilot symbol sequence. Further, as shown in FIG. 9, the norm corresponds to the distance between the transmission pilot symbol and the reception pilot symbol.
[0100]
Norm integration result n_sum [θ₁, θ₂] Is dumped, the angle of arrival of the incoming wave is estimated using a convergence algorithm such as comparison with a preset threshold value or steepest descent method. As a result, when the arrival angle estimation determination condition is satisfied, the corresponding arrival angles θ1 and θ2 are updated as the estimation result.
[0101]
In the update [a-4] of the reference signal in FIG. 8, n_sum [θ that is dumped at each time₁, θ₂], The arrival angles are estimated for the norms 1 to 4, and the determination conditions for the arrival angle estimation are satisfied for the norm 1 and the norm 3. In this case, the corresponding arrival angles are updated to DOA1 and DOA3. On the other hand, the norm 2 indicates that the previously set arrival angle DOA1 is used because the determination condition for the arrival angle estimation is not satisfied.
[0102]
When the arrival angle is updated, the value is used from the updated correlation detection execution section at the next timing. In [a-4] in FIG. 8, the updated DOA1 and DOA3 are each at time T._c(2) and T_cUsed from (4).
[0103]
The reference signal is generated for the set arrival angle DOA and the guard interval section of the 1 OFDM symbol delayed signal indicated by [a-2] in FIG. That is, in FIG._c(N) to T_dG in section (n)_nFor '.
[0104]
The reference signal can be obtained as follows. That is, the incoming wave vector is expressed as s = [s₁, S₂], A signal vector composed of a complex digital signal delayed by 1 OFDM symbol is represented by x (t−T_s) = [X₁, X₂], Angle of arrival θ₁, θ₂Assuming that the steering matrix represented by A is A and there is no influence of noise, the following equation is established.
[0105]
[Expression 2]

[0106]
The reference signal is r_ref= S₁S₁Is given by:
[0107]
[Equation 3]

[0108]
Thus the angle of arrival θ₁, θ₂Is determined, the reference signal r is used using one OFDM symbol delayed signal._refCan be calculated.
[0109]
The adaptive array signal processing is performed using a reference signal input for each correlation detection execution section. Here, the optimum weight W for the received signal_optTo calculate the weighting factor W₁And W₂Update. For example, in FIG._dReference signal r corresponding to angle of arrival DOA1 determined in (2)_refThe adaptive array signal processing using is performed in the section C2 of [a-5]. Optimal weight W_optIs a correlation matrix R obtained from a signal vector x composed of complex digital signals._xx= E [x (t) x^HInverse matrix R of (t)]_xx ^-1And the correlation vector r_co= E [x (t) r_ref ^*(T)] is integrated over the correlation detection execution interval, and after integration for one interval, that is, T_dIt is calculated according to the following equation at the timing (n).
[0110]
[Expression 4]

[0111]
Optimal weight W_optIs the correlation detection execution interval T while the adaptive array signal processing is being executed._c(N) to T_dThe weighting factor is calculated every (n) and the time T_dUpdated at (n) and used as a weighting factor thereafter, weight calculation is performed on the complex digital signal. The optimum weight updated once in this way is held until the value is updated next time.
[0112]
Optimal weight W_optIs the correlation detection execution interval T while the adaptive array signal processing is being executed._c(N) to T_dA weighting factor is calculated every (n) and time T_dUpdated at (n) and used as a weighting factor thereafter, weight calculation is performed on the complex digital signal. The optimum weight updated once in this way is held until the value is updated next time.
[0113]
Next, a processing procedure for setting the operation mode of the diversity adaptive array signal processing will be described with reference to the flowchart shown in FIG. Here, the procedure for setting and switching the operation mode such as diversity or adaptive array signal processing is shown with the start of reception when the signal is resynchronized immediately after sleep mode or after loss of synchronization when the power is turned on.
[0114]
First, in step S1, the correlation detection unit 213 executes correlation detection and outputs correlation detection information as undetected. Further, the reference signal generation unit 215 performs no operation and outputs the incoming wave information as undetected. Also, the diversity / adaptive array signal processing unit 216 performs power measurement on each of the complex digitals 1 and 2 of each reception system, compares the magnitudes thereof, and sets the larger one as a path selection signal. In addition, the operation mode is set as diversity, and is output as diversity adaptive array control information together with path selection information.
[0115]
Next, in step S2, it is determined whether or not synchronization has been acquired. If synchronization cannot be obtained, the process returns to step S1 described above. If synchronization can be acquired, the process proceeds to the subsequent step S3.
[0116]
In step S3, the correlation detection unit 213 outputs FFT window timing information, the number of peaks of the correlation signal and the peak power as correlation detection information based on the detected initial synchronization timing. Also, the reference signal generation control unit 508 estimates the propagation path environment based on this correlation detection information.
[0117]
Next, in step S4, it is determined whether or not the estimated propagation path is a multipath environment.
[0118]
If it is determined that the propagation path is not a multipath environment, the process proceeds to step S5. In this case, the reference signal generation unit 215 generates a reference signal and outputs that the propagation path is not a multipath environment as arrival wave information. Also, the diversity / adaptive array signal processing unit 216 performs power measurement on each of the complex digital signals 1 and 2 from each reception system, compares the both, and sets the larger one as path selection information. In addition, the operation mode is set as diversity, and is output as diversity adaptive array control information together with path selection information.
[0119]
On the other hand, if it is determined that the propagation path is a multipath environment, the process proceeds to step S6. In this case, the reference signal generation unit 215 generates a reference signal and outputs as arrival wave information that the propagation path is a multipath environment. Further, the diversity / adaptive array signal processing unit 216 performs signal processing using the operation mode as an adaptive array, and outputs the operation mode as diversity / adaptive array information.
[0120]
Next, in step S7, the correlation detection unit 213 outputs the number of peaks and the peak power of the correlation signal detected as correlation as correlation detection information. In addition, the reference signal generation unit 215 performs norm calculation in the norm calculation unit 502 regardless of the operation mode. Further, the reference signal generation control unit 5008 estimates the propagation path environment based on the norm calculation result and the correlation detection information.
[0121]
In this specification, the case where there are two reception antennas has been described as an example. However, even when three or more reception antennas are used, the reception system using two reception antennas as described above is provided for the number of reception antennas. It can be realized by extending to That is, the reception antennas, RF units, digital conversion units, buffers, and weight calculation units shown in FIG. 2 are provided in a number corresponding to the reception antennas, and the reference signal generation unit and the adaptive array processing unit set optimum weights for the number of reception antennas. If necessary calculations can be performed, it is possible to combine the effects of the present invention. By increasing the number of antennas, diversity reception can reduce the probability of receiving a fall section due to fading. Although adaptive array signal processing increases the amount of processing for optimum weight calculation, the number of incoming waves that can be estimated for the direction of incoming waves increases, so that the resolution can be improved.
[0122]
[Supplement]
The present invention has been described in detail above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications and substitutions of the embodiments without departing from the gist of the present invention. In other words, the present invention has been disclosed in the form of exemplification, and should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims section described at the beginning should be considered.
[0123]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to efficiently estimate the propagation path from the incoming wave distribution without changing the apparatus block configuration, and when the propagation path environment is multipath, adaptive signal processing is performed. In other propagation environments, it is possible to provide an excellent OFDM receiver using a diversity adaptive array that can be switched by selecting diversity.
[0124]
According to the OFDM receiving apparatus using a diversity adaptive array according to the present invention, diversity and adaptive array signal processing can be realized by a common block configuration, and the apparatus configuration can be simplified.
[0125]
Further, according to the OFDM receiver using the diversity adaptive array according to the present invention, it is possible to switch between diversity and adaptive array signal processing according to the propagation path situation, and to solve the problem of degradation due to multipath. Can do.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a schematic configuration of an example of an OFDM transmission apparatus that transmits an OFDM signal.
FIG. 2 is a diagram schematically showing a configuration of an OFDM receiving apparatus 200 using a diversity adaptive array according to an embodiment of the present invention.
FIG. 3 is a diagram showing a schematic configuration of a diversity adaptive array signal processing unit 216 that is a component of an OFDM receiving apparatus 200 using a diversity adaptive array according to one embodiment of the present invention.
FIG. 4 is a diagram illustrating a schematic configuration of an integral dump unit that is a component of an OFDM receiver 200 using a diversity adaptive array according to an embodiment of the present invention.
FIG. 5 is a diagram illustrating a schematic configuration of a reference signal generation unit 215 that is a constituent element of an OFDM receiving apparatus 200 using a diversity adaptive array according to an embodiment of the present invention.
FIG. 6 is a diagram illustrating a schematic configuration of a selection combining unit 211 that is a component of the OFDM receiving apparatus 200 using a diversity adaptive array according to an embodiment of the present invention.
FIG. 7 is a diagram illustrating an example of power measurement timing in the OFDM receiver 200 using an adaptive array according to an embodiment of the present invention.
FIG. 8 is a diagram illustrating an example of adaptive array signal processing timing in the OFDM receiver 200 using an adaptive array according to an embodiment of the present invention.
FIG. 9 is a diagram showing an image of a norm in OFDM receiving apparatus 200 using an adaptive array according to one embodiment of the present invention.
FIG. 10 is a flowchart showing a procedure for setting an operation mode of diversity adaptive array signal processing in an OFDM receiver using an adaptive array according to an embodiment of the present invention.
[Explanation of symbols]
100: OFDM signal transmitting apparatus
101: Modulation unit, 102: Pilot symbol insertion unit
103: Serial / parallel converter, 104 ... IFFT unit
105: guard section insertion section, 106: analog conversion section
107: RF unit, 108: Transmitting antenna
109: Transmission control unit
201, 202 ... receiving antenna
203, 204 ... RF section
205, 206 ... Digital conversion unit
207, 208 ... buffer
209, 210 ... Weight calculation unit
211... Selection / synthesis unit, 212... FFT unit
213 ... correlation detection unit, 214 ... demodulation unit
215: Reference signal generator
216: Diversity adaptive array signal processing unit
301: Vector generation unit 302: Correlation matrix calculation unit
303 ... Integral dump unit, 304 ... Inverse matrix calculation unit
305 ... correlation vector calculation unit, 306 ... integration dump unit
307 ... Weight determination unit, 308 ... Power measurement unit
309: Comparison unit
310 ... Diversity adaptive array signal processing control unit
401: selector, 402: gain section
403 ... Delay unit, 404 ... Adder unit, 405 ... Storage unit
501 ... Pilot signal generation unit, 502 ... Norm calculation unit
503 ... Integral dump unit, 504 ... Comparison unit
505 ... DOA setting unit, 506 ... delay unit
507 ... Reference signal calculator
508 ... Reference signal generator
601 ... Adding unit, 602 ... Selecting unit
603... Selector, 604.

Claims (7)

An OFDM receiver using selective diversity that selectively uses a plurality of OFDM (Orthogonal Frequency Division Division) received signals,
A receiving antenna, an RF unit for downconverting a signal received via the receiving antenna from an RF frequency band to a baseband signal, and digital conversion for converting the downconverted baseband signal into a complex digital signal by A / D conversion A plurality of receiving systems each including a part,
A weight calculator for weighting the complex digital signal when performing adaptive signal processing;
When performing diversity, one is selected from the complex digital signals from each reception system, and when performing adaptive signal processing, a selection combining unit that adds each complex digital signal weighted by the weight calculation unit;
An FFT unit that generates a received symbol of a parallel carrier by performing a Fourier transform of one period of an OFDM symbol on a complex digital signal output from the selection combining unit according to a predetermined FFT window timing;
Correlation calculation is performed on the complex digital signal output by the selection / synthesis unit using the signal in the guard interval portion, and correlation detection information including at least one of FFT window timing information, the number of peaks of the correlation signal, and peak power is obtained. An output correlation detector;
A demodulator that demodulates received symbols of parallel carriers corresponding to each receiving system;
The pilot symbol is extracted from the received symbols for each of the OFDM subcarriers corresponding to several parallel carriers output by the FFT unit, the propagation path is estimated, and the arrival angle of the incoming wave based on the pilot symbol is estimated, A reference signal generation unit for generating a reference signal corresponding to an incoming wave having strong signal power;
A diversity adaptive array signal processing unit for calculating an optimum weighting factor for a received signal in each receiving system from the reference signal and a complex digital signal from each receiving system;
An OFDM receiver using a diversity adaptive array, comprising: When performing adaptive signal processing,
The weight calculation unit weights and adds the complex digital signal from each receiving system with the optimum weight coefficient calculated by the diversity and adaptive array signal processing unit, and the addition result is used as the composite complex digital signal. Output to the detection unit and the FFT unit;
The correlation detection unit performs correlation detection using a repetitive pattern of the guard interval section, generates correlation detection information including FFT window timing information, the number of peaks of the correlation signal, peak power, and the like. Output timing information to the FFT unit, and output the correlation detection information to the reference signal generation unit,
The FFT unit performs a Fourier transform for each OFDM symbol according to the FFT window timing information to generate parallel carrier reception symbols, and outputs the received symbols to the demodulation unit and the reference signal generation unit,
The demodulator performs demodulation for each received symbol of the parallel carrier,
The reference signal generator extracts pilot symbols from a plurality of received symbols of the parallel carrier, generates the same sequence as the pilot symbol sequence at the time of transmission, and calculates a norm for each received symbol based on the difference between the two. The arrival angle of the incoming wave is estimated based on the norm integral value obtained by integrating each, and a reference signal is generated based on the estimated value and the complex digital signal, and is output to the diversity adaptive array signal processing unit. ,
The diversity adaptive array signal processing unit calculates a weighting factor based on the complex digital signal and the reference signal for each guard interval section and outputs the weighting factor to the weight calculating unit.
It OFDM receiver using a diversity adaptive array according to claim 1 you characterized. When performing diversity,
The diversity / adaptive array signal processing unit performs power measurement on each of the complex digital signals from each receiving system and compares them to determine a complex digital signal having the highest power and to select and combine the signal as path selection information. Output to
The selection combining unit selects only one complex digital signal according to path selection information for the complex digital signal not weighted by the weight calculation unit,
FFT, demodulation, and correlation detection are performed on the selected complex digital signal.
The OFDM receiving apparatus using the diversity adaptive array according to claim 1. The reference signal generation unit arrives in OFDM symbol units based on correlation detection information input from the correlation detection unit, power measurement information input from the diversity adaptive array signal processing unit, and a norm integral value for each received symbol. Obtain propagation path parameters consisting of wave number, incoming wave power, time variation of power fluctuation, etc., estimate propagation path conditions based on the propagation path parameters, and perform either adaptive array signal processing or diversity according to the estimation result Determine the operating mode,
The OFDM receiving apparatus using the diversity adaptive array according to claim 1. The reference signal generator is
When the operation mode is switched to diversity and it is determined that the synchronization is not obtained from the correlation detection information input from the correlation detection unit, the power measurement of the complex digital signal from each receiving system is performed at a preset integration period and timing. The power measurement results are compared with each other, the larger value is selected and output to the correlation detection unit to perform correlation detection,
Start estimation of propagation path conditions after synchronization is acquired and switch operation mode to adaptive array signal processing or diversity,
The OFDM receiving apparatus using the diversity adaptive array according to claim 1. When the operation mode is diversity, the reference signal generation unit includes correlation detection information input from the correlation detection unit, power measurement information input from the diversity adaptive array signal processing unit, and a norm integral value for each received symbol. Based on this, determine the power measurement period and measurement timing, and whenever they change, change the power whenever necessary to measure the power of the complex digital signal.
The OFDM receiving apparatus using the diversity adaptive array according to claim 1. When the operation mode is changed, the reference signal generation unit continuously performs signal processing in the operation mode before the change until the boundary of the OFDM symbol immediately after that, and outputs a demodulated symbol of the parallel carrier. Works in the changed mode of operation,
The OFDM receiving apparatus using the diversity adaptive array according to claim 1.

Images