JP2004343562A - Multi-carrier tdd communication system and communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce peak power at each transmission antenna without deteriorating the error-ratio characteristics of a communication partner, in communication using two or more carriers, to which transmission diversity is applied, simultaneously. <P>SOLUTION: A receiving level measuring unit 201 and a receiving level measuring unit 202 measure a receiving level of each carrier received by a transceiver antenna 101 and a transceiver antenna 102. A receiving level magnitude comparing unit 203 selects an antenna with maximum receiving level for each carrier.A counter 204 calculates the total number of selected carriers for each antenna based on the selected result. A sub-carrier polarity reversible unit 206 selects each carrier based on the total number so that the total number of carriers selected for each antenna at the time of transmission may not exceed a previously set threshold value S. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００３１】
表１に、大小比較部２０５の入力信号に対する出力信号の対応を示す。表１において、カウンタ２０４から入力された「サブキャリア総数信号」をｍとし、しきい値をＳとすると、ｍ＞Ｓとなる場合には、その差（ｍ−Ｓ）を「極性反転回数信号」として出力し、ｍ≦Ｓとなる場合には、「極性反転回数信号」として０を出力する。この「極性反転回数信号」は、サブキャリア極性反転部２０６に入力される。ここで、ブランチ１の「サブキャリア総数信号」は“３０”であり、３０＞２６となるため、出力結果である「極性反転回数信号」は、ブランチ１については“４”となる。一方、ブランチ２の「サブキャリア総数信号」は“２２”であり、２２＜２６となるため、出力結果である「極性反転回数信号」は、ブランチ２については“０”となる。
【００３２】
サブキャリア極性反転部２０６では、大小比較部２０５からの「極性反転回数信号」に基づいて、極性反転処理（あるサブキャリアについて選択されたブランチを変更する処理）を行うブランチ及びサブキャリア数が決定される。各ブランチの「極性反転回数信号」の値は、ブランチ１では”４”であり、ブランチ２では”０”であるため、ブランチ１が選択された”３０”個のサブキャリアのうち、”４”個のサブキャリアについて極性反転が行われる。ブランチ２については、「極性反転回数信号」が”０”であるため、極性反転は行われない。
【００３３】
ブランチ１において極性反転の対象となるサブキャリアは、ブランチ１が選択されているサブキャリアのうち、サブキャリア番号が若い番号を優先的に反転させる。図１２に反転の様子を示す。ブランチ１が選択されている若いサブキャリア番号となるサブキャリア＃１〜＃４に対して極性反転が行われており、その結果、サブキャリア＃１〜＃４ではブランチ２が選択される。この極性反転処理結果は、送信用の「ブランチ選択信号」としてサブキャリア選出部３０３に入力される。
このように、基地局装置は、受信時の各ブランチのサブキャリアにおける受信レベルに基づいて、送信時の送信すべきサブキャリアを選択した結果、ある特定のブランチにおいてサブキャリアが集中して選択される場合には、その特定のブランチ内のサブキャリアの一部を上記特定のブランチ以外のブランチを用いて送信を行うことができる。従って、通常の送信ダイバーシチを行うＯＦＤＭ通信装置と比較して、各ブランチにおけるピーク電力を低減することができる。
【００３４】
次に、本発明の第２の実施の形態による通信技術について図面を参照して説明を行う。上記第１の実施の形態の形態による通信技術においては、図２に示すサブキャリア極性反転部２０６において、極性反転対象となるサブキャリアを受信状況と関係なく選択するため、送信ダイバーシチを行う一般的なＯＦＤＭ通信装置よりも通信相手となる端末の受信特性が劣化するという問題が挙げられる。すなわち、上記第１の実施の形態においては、極性反転対象となるサブキャリアの選択が任意であるのに対して、第２の実施の形態による通信技術では、受信状況を考慮したサブキャリア選択を行う点に特徴がある。本実施の形態による通信技術に関して、図９を参照しつつ説明を行う。尚、基地局装置の受信状況は図１１に示す状況であると仮定して説明する。
【００３５】
図９に示すように、受信レベル測定部４０１では、復調部１０３内のＦＦＴ回路からの各サブキャリアについての受信レベルが測定される。その測定値が、受信レベル大小比較部４０２に入力される。また、受信レベル測定部４１１では、復調部１０４内のＦＦＴ回路からの各サブキャリアについての受信レベルが測定される。その測定値は、受信レベル大小比較部４０２に入力される。受信レベル大小比較部４０２では、受信レベル測定部４０１と受信レベル測定部４１１とからの入力値に基づいて、サブキャリア毎に受信レベルの比較が行われる。この比較結果は、「ブランチ選択信号」として、サブキャリア合成部１０５と、カウンタ４０３と、ソート回路４０５と、サブキャリア極性反転部４０７と、に入力される。ここで、基地局装置の受信状況が図１１の上図に示す状態である場合には、各サブキャリアの「ブランチ選択信号」は図１１の下図のようになる。
【００３６】
また、受信レベル大小比較部４０２では、受信レベル測定部４０１及び受信レベル測定部４１１の測定結果に基づいて、サブキャリア毎にブランチ１の受信レベルからブランチ２の受信レベルを引いたサブキャリアの受信レベルの差が算出される。この算出結果は、「受信レベル差信号」としてソート回路４０５に入力される。カウンタ４０３では、受信レベル大小比較部４０２からの「ブランチ選択信号」に基づいて、ブランチ１が選択されたサブキャリアの総数が算出される。この算出結果は、「サブキャリア総数信号」として比較部４０４及び極性反転決定部４０６に入力される。図１１の場合には、各ブランチの「サブキャリア総数信号」は“３０”となる。
【００３７】
比較部４０４では、カウンタ４０３からの「サブキャリア総数信号」と、予め設定されたしきい値Ｓとの差をそれぞれ算出することにより、各ブランチにおいて極性反転を行うサブキャリア数を示す「極性反転回数信号」を生成する。生成された「極性反転回数信号」は、極性反転決定部４０６に入力される。前述のしきい値Ｓは、各ブランチにおいて送信すべきサブキャリアの最大数を示している。図１１の場合には、「極性反転回数信号」は“４”となる。ソート回路４０５では、受信レベル大小比較部４０２からの各キャリアの「受信レベル差信号」に基づいて、受信レベルの大きいサブキャリアから順に並べ替え処理が行われる。また、そのとき「受信レベル差信号」の大きいサブキャリアのサブキャリア番号を順に出力した「ソートサブキャリア番号信号」が生成される。この結果、「ソートサブキャリア番号信号」は、極性反転決定部４０６に入力される。図１１の受信レベルである場合には、ソート回路４０５において並び替え処理された「受信レベル差信号」は、図１３で示されるようになる。
【００３８】
極性反転決定部４０６では、比較部４０４からの「極性反転回数信号」が正の値となるブランチを、サブキャリアの極性反転処理を行うブランチと決定する。さらに、「極性反転回数信号」の値により極性反転処理を行うサブキャリア数が決定される。ここで、「サブキャリア総数信号」をｍ、「極性反転回数信号」をｎ、しきい値をＳとする。サブキャリアの極性反転処理を行うブランチがブランチ１の場合、つまりｍ≧Ｓの場合には、ブランチ１の内でブランチ間の受信レベル差が小さいものからｎ個までのサブキャリアを極性反転対象となるサブキャリアとして選択する。これは、「ソートサブキャリア番号信号」のソート番号Ｓからｍに対応するサブキャリア番号のサブキャリアが極性反転対象となることと等価である。
【００３９】
サブキャリアの極性反転処理を行うブランチがブランチ２の場合、つまりｍ＜Ｓの場合には、ブランチ２内でブランチ間の受信レベル差が小さいものからｎ個までのサブキャリアを極性反転対象となるサブキャリアとして選択する。これは、「ソートサブキャリア番号信号」のソート番号ｍからＳに対応するサブキャリア番号のサブキャリアが極性反転対象となることと等価である。以上の処理により、極性反転対象となるサブキャリア番号が決定し、この結果は、「極性反転番号信号」としてサブキャリア極性反転部４０７に入力される。
【００４０】
サブキャリア極性反転部４０７では、受信レベル大小比較部からの「ブランチ選択信号」に対して極性反転処理が行われる。その際、極性反転決定部４０６からの「極性反転番号信号」に示されるサブキャリア番号のサブキャリアに対して極性反転処理が行われる。
【００４１】
以上の処理によって極性反転が行われた「ブランチ選択信号」が送信用のブランチ選択信号として、サブキャリア選出部４０８に出力される。図１１に示す例では、「極性反転回数信号」よりブランチ１のサブキャリアのうち、４つのサブキャリアについて極性反転が行われる。さらに、「サブキャリア番号信号」よりブランチ１が選択されたサブキャリア番号＃３０、＃２９、＃２８および＃２７のサブキャリアについて極性反転が行われる。その結果、「ブランチ選択信号」は、図１４に示すようになる。
【００４２】
以上に説明したように、本実施の形態による基地局装置は、ある特定のブランチにおいてサブキャリアが集中して選択される場合には、その特定のブランチ内において、他のブランチとの間の受信レベル差の小さいサブキャリアを、その特定ブランチ以外のブランチを用いて送信する。従って、通信相手となる端末の受信特性を劣化させることなく各送信ブランチにおけるピーク電力を低減できることができるという利点がある。
【００４３】
次に、本発明の第３の実施の形態による通信技術について図面を参照しつつ説明を行う。上記第２の実施の形態による通信技術を用いた場合には、図９に示すソート回路４０５において、「受信レベル差信号」の並び替えを行う処理が必要となる。この処理はアナログ値の並び替え処理を含むため、ブランチ数の増加又は使用されるサブキャリア数の増加に伴い、回路規模が増大する。
【００４４】
本実施の形態による通信技術では、極性反転処理を行う際に、「受信レベル差信号」を用いずに「ブランチ選択信号」のみを参照して並び替えの処理を行う点に特徴がある。以下に、「ブランチ選択信号」のみを用い、受信状況を考慮した極性反転処理の原理について図１１を参照しつつ説明を行う。基地局装置での受信状況が図１１の上図に示される場合に、サブキャリア番号＃３０とサブキャリア番号＃３１との間においてブランチ１とブランチ２との受信レベルが逆転していることがわかる。このように、選択されるブランチが切り替わるサブキャリア番号＃３０のサブキャリアとサブキャリア番号＃３１のサブキャリアでは、他のサブキャリアよりも両ブランチ間の受信レベル差が小さい。本実施の形態による通信技術においては、上記のように、選択されるブランチが切り替わるサブキャリアは、ブランチ間の受信レベル差が小さくなる点に着目し、「ブランチ選択信号」のサブキャリア極性反転時には、選択されるブランチが切り替わるサブキャリアに対して優先的に極性反転を行うことにより、「ブランチ選択信号」のみを用い、受信状況を考慮した各サブキャリアのブランチ選択が実現できる。
【００４５】
図１０は、本実施の形態に係るＯＦＤＭ通信装置のブロック図である。ここで、図１０に示されるＯＦＤＭ通信装置を基地局装置に搭載した場合について説明する。但し、各ブランチの選択可能なサブキャリアの最大数を示すしきい値Ｓは、全サブキャリア数５２の半数のＳ＝２６の場合を説明する。図１０に示すように、受信レベル測定部２０１では、復調部１０３より入力されたブランチ１における各サブキャリアについての受信レベルが測定される。その測定値は、受信レベル大小比較部２０３に入力される。また、受信レベル測定部２０２では、復調部１０４より入力されたブランチ２における各サブキャリアについての受信レベルが測定される。その測定値も受信レベル大小比較部２０３に入力される。受信レベル大小比較部２０３では、受信レベル測定部２０１及び受信レベル測定部２０２からの測定値に基づいて、サブキャリア毎に受信レベルの比較が行われる。この比較結果は、「ブランチ選択信号」として出力され、サブキャリア合成部１０５およびサブキャリア極性反転部５０３に対して出力される。
【００４６】
本実施の形態における「ブランチ選択信号」は、サブキャリア毎にブランチ１とブランチ２とのサブキャリアの受信レベルを比較し、ブランチ１のサブキャリアの受信レベルが大きい場合には“１”とし、逆に、ブランチ２のサブキャリアの受信レベルが大きい場合には“０”とするブランチの選択を示す信号である。ここで、送信用のブランチ選択信号の生成が行われるサブキャリア極性反転部５０４の回路構成図を図１９に示し、その動作について図１５に示されるフローチャート図を参照して説明する。
【００４７】
図１９において、符号１００１、１００４、１００５、１００７、１００８および１０１０はＸＮＯＲゲート回路を示し、符号１００２、１００９、１０１３、１０１４及び１１１６は、ＡＮＤゲート回路を示し、符号１００３、１００６および１０１１はＤフリップフロップ回路を、符号１０１２はインバータ回路を、符号１０１５はＯＲゲート回路を表す。図１０に示す受信レベル大小比較部２０３から入力された「ブランチ選択信号」は、図１９に示す記憶装置９０１およびカウンタ９０２に入力される。記憶装置９０１は、「ブランチ選択信号」を記憶するための５２×１ビットのメモリ領域を所有しており、５２のサブキャリアについての「ブランチ選択信号」は、例えば、このメモリ領域のアドレス１から順にアドレス５２まで記憶される（図１５のフローチャート図のステップ７０１参照）。
【００４８】
次に、記憶装置９０１のアドレス１から順に回路１１０８に対して「ブランチ選択信号」の値が出力される。但し、記憶装置９０１から値を読み出す場合には、アドレス１から順に必ずアドレス５２まで読み出され、記憶装置９０１は５３クロック周期で動作する。また、記憶装置９０１では、回路１１０８に「ブランチ選択信号」を出力するとともに、回路１１０９からの極性反転処理が行われた「ブランチ選択信号」が入力される。この入力された「ブランチ選択信号」により各サブキャリアの極性がアップデートされる。但し、記憶装置９０１において回路１１０９からの値を記憶する場合には、図２０に示される信号（Ｓ５）が“１”となるクロックタイミングにおいてのみ回路１１０９からの値が記憶される。言い換えれば、２番目のクロックよりアドレス１の値のアップデートが開始され、５３番目のクロックにおいてアドレス５２までのアップデートが完了することを示している。最後に、記憶装置９０１における５３クロック周期の動作は、５３番目のクロックにおいて比較部９０７からの信号Ｓ４の値を参照し、信号Ｓ４が“０”であるときに動作が終了する。
【００４９】
カウンタ９０２では、入力された「ブランチ選択信号」に基づいて、ブランチ１が選択されたサブキャリアの総数ｍがカウントされる（ステップ７０２）。この出力結果ｍは「サブキャリア総数信号」として、減算器９０３及び比較部１０６に入力される。減算器９０３では、カウンタ９０２より入力された「サブキャリア総数信号」ｍとしきい値２６との差ｈを算出する。本実施の形態では、しきい値を２６としているため、ｈ＝ｍ−２６となる（ステップ７０５）。このｈは、絶対値算出部９０４及び符号判定部９０５に入力される。絶対値算出部９０４では、減算器９０３より入力されたｈの絶対値ｉが算出される（ステップ７０５）。この絶対値ｉは、必要となる極性反転の回数を示しており、「極性反転回数信号」として比較部９０７に入力される。符号判定部９０５では、減算器９０３からのｈの符号が正か負かの判定が行われる。この判定結果として、ｈ≧０の場合には“０”、ｈ＜０の場合には“１”とする符号を示す信号Ｓ１が生成され（ステップ７１１）、回路１００１に入力される。ここで、信号Ｓ１は、「ブランチ選択信号」の各サブキャリアにおける極性“０”及び極性“１”の総数のいずれが多いかを示す信号であり、極性“０”が多い場合（ｈ＜０。Ｓ１＝１）には、極性“０”を極性“１”にする極性反転処理を行うことを示し、極性“１”が多い場合（ｈ≧０、Ｓ１＝０）には極性“１”を極性”０”にする極性反転処理を行うことを示している。
【００５０】
比較部１１０６では、カウンタ９０２からの「サブキャリア総数信号」ｍが“０”又は“５２”となる場合には、“１”が出力され、その他の場合には“０”が出力される。この出力結果Ｓ２は、回路１１１１に入力される。ここで、ｍ＝０またはｍ＝５２の時には、選択されるブランチが切り替わるサブキャリアが存在しないため、極性反転処理を行うことができない。このような場合においても極性反転処理を行うことができるように、極性反転処理を行う回路１１０８にブランチの切り替わりの有無を伝達する信号である（ステップ７０３）。
【００５１】
回路１１０８は、カウンタ１１１０、回路１１１１、回路１１１２、回路１１１３および回路１１１４より成る。回路１１０８では、入力信号として記憶装置９０１からの「ブランチ選択信号」、符号判定部９０５からの信号Ｓ１及び比較部１１０６からの信号Ｓ２が入力される。入力された信号Ｓ１および信号Ｓ２に応じて、「ブランチ選択信号」の極性反転が行われる。以下に、その動作原理を示す。
【００５２】
回路１１１１では、入力された「ブランチ選択信号」のサブキャリア番号＃ｊ＋１の極性と１クロック前のサブキャリア番号＃ｊの極性とが比較され、極性が異なる場合には極性反転を行う信号”１”、極性が等しい場合には極性反転を行わない信号“０”が出力される（ステップ７０７）。この出力結果は、カウンタ１１１０および回路１１１４に入力される。カウンタ１１１０では、回路１１１１より入力された信号に基づいて回路１１０８において極性反転が必要と判断された回数がカウントされる。
【００５３】
但し、図１８に示される入力信号Ｓ６が“１”となるクロックタイミングにおいてのみ極性反転回数のカウントが実行される（ステップ７１５）。このカウントされた結果Ｓ３は、比較部９０７に入力される。
【００５４】
回路１１１４では、入力された信号Ｓ６に従って極性反転処理を実行できるタイミングが決定される。信号Ｓ６は、図１８に示すように、クロックタイミング第１番目と第５３番目において“０”となっているため、これら２つのクロックタイミングにおいては回路１１１１より入力された信号の値に関わらず、極性反転処理が行われないように制御する信号が生成される。この出力結果は、回路１１１２および回路１１１３に出力される。
【００５５】
回路１１１２および回路１１１３では、回路１１１４より入力された信号が“０”の場合には極性反転処理が行われず、“１”の場合にサブキャリア番号＃ｊ又は＃ｊ＋１の極性反転処理が行われる。この時、サブキャリア番号＃ｊと＃ｊ＋１の極性は異なるものとなっているため、サブキャリア番号＃ｊと＃ｊ＋１のいずれかの極性が反転処理される。その基準は、「ブランチ選択信号」の内で“０”および“１”のいずれの極性が多いかを示す、符号判定部からの信号Ｓ１である（ステップ７１２）。信号Ｓ１が“０”の場合、つまり「ブランチ選択信号」の極性“１”が多い場合には、サブキャリア番号＃ｊ及び＃ｊ＋１の極性のうち、極性が“１”のサブキャリアに対して極性反転処理が行われる（ステップ７１３）。逆に、信号Ｓ１が“１”の場合、つまり「ブランチ選択信号」の極性“０”が多い場合には、サブキャリア番号＃ｊ及び＃ｊ＋１の極性のうち、極性が“０”のサブキャリアに対して極性反転処理が行われる（ステップ７１４）。この結果、極性反転処理が行われた「ブランチ選択信号」が出力され、回路１１０９に入力される。
【００５６】
比較部９０７では、絶対値算出部９０４からの「極性反転回数信号」ｉとカウンタ１１１０からの信号Ｓ３との比較が行われる。Ｓ３の値をｋとすると、ｉ−ｋ＞０の場合には、比較部９０７は“１”を出力し、ｉ−ｋ≦０の場合には比較部９０７は“０”を出力する。この出力結果は、信号Ｓ４として回路１１０９及び記憶装置１１１５に入力される。また、信号Ｓ４は極性反転処理の要否を示しており、Ｓ４＝“１”の場合には極性反転処理が必要であることを示し、Ｓ４＝“０”の場合には極性反転処理が必要でないことを示している。
【００５７】
回路１１０９では、比較部９０７からの極性反転処理の有無を示す信号Ｓ４に基づいて、出力として極性反転処理を行った「ブランチ選択信号」又は極性反転処理を行わない「ブランチ選択信号」のいずれを出力するのかが決定される。Ｓ４＝１の場合、極性反転処理を行った「ブランチ選択信号」が出力され、Ｓ４＝０の場合、極性反転処理を行わない「ブランチ選択信号」が出力される。この出力結果は、記憶装置９０１および記憶装置１１１５に入力される。
【００５８】
記憶装置１１１５では、回路１１０９からの「ブランチ選択信号」を記憶するための５２×１ビットのメモリを所有しており、図２０に示される入力信号Ｓ５が“１”となるクロックタイミングにおいてのみメモリに記憶される。また、記憶装置１１１５では、信号Ｓ５により第２番目のクロックよりアドレス１から順に「ブランチ選択信号」が記憶され、第５３番目のクロックにおいてアドレス５２まで記憶される。記憶装置１１１５における動作の終了は、記憶装置９０１と同様であり、５３番目のクロックにおいて比較部９０７からの信号Ｓ４の値を参照し、Ｓ４が“０”であるときに動作が終了する（ステップ７１６）。
【００５９】
このように、本実施の形態による基地局装置は、通信相手となる端末の受信特性を劣化させることなく、各ブランチのピーク電力を抑える送信ダイバーシチを行うことができる。また、回路構成が非常に単純であり、少ない回路規模で装置を実現できるという利点がある。
【００６０】
次に、本発明の第４の実施の形態による通信技術について図面を参照しつつ説明を行う。本発明の第３の実施の形態による通信技術では、各ブランチのピーク電力を最も最小化できる総サブキャリア数５２の半数である２６を各ブランチの選択可能なサブキャリアの最大数を示すしきい値として用いたが、本実施の形態では、「最大サブキャリア数」を任意に選択できる。
【００６１】
本実施の形態によるＯＦＤＭ通信装置は、第３の実施形態のＯＦＤＭ通信装置と同様の構成を有しており、図１０においてサブキャリア極性反転部５０４の回路構成のみが変わる。図２１に本実施の形態によるサブキャリア極性反転部の回路構成を示し、図２２に動作の流れを示すフローチャート図を示す。本実施の形態による装置が第３の実施の形態による装置と異なるのは、図１９において絶対値算出部９０４の出力結果であるｉと、符号判定部９０５の出力信号Ｓ１および比較部１１０６の出力信号Ｓ２の算出方法とである。以下に、ｉと信号Ｓ１及びＳ２の算出手順を示す。
【００６２】
カウンタ１３０１では、図１０に示される受信レベル大小比較部２０３より入力された「ブランチ選択信号」に基づいて、ブランチ１が選択されたサブキャリアの総数ｍ１およびブランチ２が選択されたサブキャリアの総数ｍ２がカウントされる（図２２：ステップ７０２ａ）。この出力結果ｍ１は、減算器１３０２及び比較部１４０５に入力され、ｍ２は減算器１３０３に入力される。減算器１３０２では、カウンタ１３０１からのｍ１と「最大サブキャリア数」ａとの差ｈ１が算出される（ステップ７０５）。このｈ１（＝ｍ１−１）は、大小比較部１３０４に入力される。減算器１３０３では、カウンタ１３０１からのｍ２と「最大サブキャリア数」ａとの差ｈ２が算出される（ステップ７０５）。このｈ２（＝ｍ２−ａ）は、大小比較部２０３（図１０）に入力される。図１０に示す大小比較部２０３では、減算器１３０２からの信号ｈ１と減算器１３０３からの信号ｈ２との大小を比較し、大きい方の信号を出力する。この出力結果は、「極性反転回数信号」ｉとして比較部１２０４に入力される。また、大小比較部２０３（図１０）では、ｈ１≧ｈ２の場合にＳ１＝０、Ｈ１＜ｈ２の場合にＳ１＝１とする信号Ｓ１が生成される。この信号Ｓ１は、回路１３０８に入力される。
【００６３】
比較部１４０５では、カウンタ１３０１からの信号ｍ１の値が“０”または“５２”となる場合には“１”が出力され、その他の場合には“０”が出力される（ステップ７０３）。この出力結果Ｓ２は、回路１３１１に入力される。以上の処理が第３の実施の形態と異なる処理であり、その他の処理は第３の実施の形態と同様の処理を行う。このように、図２１に示す回路構成を用いることにより、各ブランチにおいて設定された最大のサブキャリア数を超えないようにサブキャリア数を選択でき、各ブランチにおけるピーク電力を抑えることが可能となる。
【００６４】
また、本実施の形態においては回路構成が非常に単純なものとなっており、少ない回路規模で装置化が可能である。
以上、本発明に関して実施の形態に沿って説明を行ったが、本発明はこれらの例に限定されるものではなく、種々の変形が可能であるのは言うまでもない。
【００６５】
【発明の効果】
本発明により、送信ダイバーシチを適用する複数の搬送波を同時に用いて通信を行う通信システムにおいて、通信相手の誤り率特性を劣化させることなく、各送信アンテナにおけるピーク電力を低減する通信装置を提供することが可能となる。また、通信相手の誤り率を劣化させることなく、各送信アンテナにおけるピーク電力を低減する通信装置を提供することが可能となる。
【図面の簡単な説明】
【図１】一般的な通信装置の構成例を示すブロック図である。
【図２】本発明の第１の実施の形態による通信装置の構成例を示す図である。
【図３】本発明の第１の実施の形態による通信装置のブランチ１の各サブキャリアの受信レベルの一例を示す図である（横軸は周波数）。
【図４】本発明の第１の実施の形態による通信装置のブランチ２の各サブキャリアの受信レベルの一例を示す図である（横軸は周波数）。
【図５】本発明の第１の実施の形態による通信装置の合成後の各サブキャリアの受信レベルを示す図である（横軸は周波数）。
【図６】本発明の第１の実施の形態による通信装置のブランチ１の各サブキャリアの送信レベルを示す図である（横軸は周波数）。
【図７】本発明の第１の実施の形態による通信装置のブランチ２の各サブキャリアの送信レベルを示す図である（横軸は周波数）。
【図８】本発明の第１の実施の形態による通信相手の端末装置での各サブキャリアの受信レベルを示す図である（横軸は周波数）。
【図９】本発明の第２の実施の形態による通信装置の構成例を示す図である。
【図１０】本発明の第３の実施の形態による通信装置の構成例を示す図である。
【図１１】ブランチ数が２であり、サブキャリア総数が５２である場合における各サブキャリアの受信レベルの一例を示す図である。
【図１２】本発明の第１の実施の形態による通信技術を適用した後の「ブランチ選択信号」の例を示す図である（横軸は周波数）。
【図１３】本発明の第２の実施の形態における各サブキャリアについて１ブランチ間の受信レベル差を大きい順に並べ替えた「受信レベル差信号」を示す図である（横軸は周波数）。
【図１４】本発明の第２の実施の形態による通信装置の「ブランチ選択信号」の例を示す図である（横軸は周波数）。
【図１５】本発明の第３の実施の形態による通信装置における各ブランチについて送信時に選択されるサブキャリアを決定する処理の流れを示すフローチャート図である。
【図１６】図１の復調部１０３および復調部１０４、図２の復調部１０３および復調部１０４、図９の復調部１０３および復調部１０４、および図１０の復調部１０３および復調部１０４の詳細な装置構成図
【図１７】図１、図２、図９及び図１０の２つの変調部のそれぞれの内部の構成例を示す図である。
【図１８】信号Ｓ６の波形例を示す図である。
【図１９】本発明の第３の実施の形態による通信装置における図１０のサブキャリア極性反転部２０４の回路構成例を示す図である。
【図２０】信号Ｓ５の波形例を示す図である。
【図２１】本発明の第４の実施の形態による通信装置における図１０のサブキャリア極性反転部２０４の回路構成例を示す図である。
【図２２】本発明の第４の実施の形態による通信装置の各ブランチについて送信時に選択されるサブキャリアを決定する処理の流れを示すフローチャート図である。
【符号の説明】
１０１、１０２…送受信アンテナ、１０３、１０４…復調装置、１０５…サブキャリア合成部、１０６…デマッピング部、１０７…Ｐ／Ｓ変調部、２０１、２０２…受信レベル測定部、２０３…受信レベル[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a communication technique for performing communication using a time division duplex (TDD) scheme as a duplex scheme in a multicarrier communication system using transmission diversity.
[0002]
[Prior art]
In a wireless communication system using a TDD system as a duplex system, communication is performed using the same frequency for transmission and reception. Therefore, the base station device selects and branches a branch having the highest level of a signal received from a terminal. Thus, transmission diversity can be easily realized. This is based on the principle that, if the same frequency is used for transmission and reception, the propagation path during transmission and reception becomes equal, so that when transmission is performed from the branch where the received signal level is maximum, the reception power of the terminal is also maximum. In particular, in a multi-carrier wireless communication system, information data is divided, and multi-carrier transmission for transmitting each divided information data on a plurality of carriers is used. Therefore, transmission diversity of each carrier which is a component of the multi-carrier is used. Application is possible, and application of transmission diversity to a multi-carrier wireless communication system is considered to be very effective.
[0003]
Hereinafter, an operation principle and a configuration example of a conventional multi-carrier wireless communication apparatus that performs transmission diversity will be described with reference to FIG. The wireless communication device shown in FIG. 1 assumes that an OFDM (Orthogonal Frequency Division Multiplexing) wireless communication system is used as a multicarrier wireless communication system, and the OFDM wireless communication device shown in FIG. 1 is applied to a base station device. Will be described. However, as shown in FIG. 1, the number of antenna branches used in the base station apparatus is set to 2, and the number of subcarriers used is set to 6. A transmission signal transmitted by radio from a terminal device that is a communication partner of the base station device is transmitted and received by a transmission / reception antenna 101 (hereinafter, referred to as “branch 1”) and a transmission / reception antenna 102 (hereinafter, referred to as “branch 1”) in the base station device shown in FIG. , "Branch 2"). The received signals received in branch 1 and branch 2 are input to demodulation sections 103 and 104, respectively.
[0004]
As illustrated in FIG. 16, the demodulation units 103 and 104 include a down converter 1, an A / D (Analog / Digital) converter 2, and an FFT (Fast Fourier Transform) circuit 3. In the demodulation unit 103, since the signal received in the branch 1 is an RF (Radio Frequency) band signal, the down converter 1 converts the signal into a BB (Base Band) band time-series signal. This time-series signal is an analog signal, and the input analog signal is converted into a digital signal in the A / D converter 2 in order to perform digital signal processing. The FFT circuit 3 performs an FFT process on the received signal converted into a digital signal from the A / D converter 2. Here, the FFT processing means to demodulate an OFDM modulated signal, and is a process of separating each subcarrier information signal from an OFDM modulated signal having a plurality of multiplexed carrier components (subcarriers). By the FFT processing, each subcarrier information signal of the reception signal received in branch 1 is input to subcarrier synthesis section 105 and reception level measurement section 201. Similarly, in demodulation section 104, the received signal received in branch 2 is separated into signal components of each subcarrier, and each subcarrier information signal is input to subcarrier synthesis section 105 and reception level measurement section 202.
[0005]
The reception level measurement section 201 measures the reception level of each subcarrier in the branch 1, and the measured value is input to the reception level magnitude comparison section 203. Similarly, reception level measurement section 202 measures the reception level of each subcarrier in branch 2, and the measured value is input to reception level magnitude comparison section 203. The reception level comparison section 203 compares the reception levels for each subcarrier based on the measurement values from the reception level measurement section 201 and the reception level measurement section 202. Here, in both transmission and reception, it is desirable to perform demodulation and modulation by selecting a subcarrier having the highest reception level as much as possible, so that a branch having a high reception level is selected for each subcarrier. This selection result is input as a “branch selection signal” to subcarrier combining section 105 and subcarrier selecting section 303.
[0006]
The above operation will be described with reference to FIGS. However, the subcarriers in FIG. 3 (similarly in FIGS. 4 to 9) are schematic diagrams for easily explaining the operation principle of the base station apparatus, and are the same as the subcarrier arrangement itself that is actually orthogonalized. Is different. The horizontal axis f is frequency. When the reception levels of the branch 1 and the branch 2 are as shown in FIGS. 3 and 4, respectively, the branch having the higher reception level is selected for each subcarrier in the reception level magnitude comparison unit 203. Branch 1 is selected for the divided subcarriers # 1, # 3, # 4, # 5, and # 6, and branch 2 is selected for subcarrier # 2.
[0007]
The subcarrier combining section 105 performs selective combining reception for selecting and combining branches for each subcarrier based on the “branch selection signal” from the reception level magnitude comparing section 203. FIG. 5 shows the reception levels of the reception signals selectively combined in subcarrier combining section 105 when the reception levels in branch 1 and branch 2 are as shown in FIGS. 3 and 4, respectively. As shown in FIG. 5, it can be seen that the reception level can be improved by performing selective combining using a plurality of branches as compared with the case of receiving using only a single branch (for example, branch 2 shown in FIG. 4).
[0008]
The received signal selectively combined by the subcarrier combining unit 105 is subjected to demapping processing by a demapping circuit 106, and received by a P / S (Parallel / Serial) converter 107 to receive a plurality of sequences transmitted by six subcarriers The signal is parallel-to-serial converted to obtain a received data sequence.
[0009]
The transmission data sequence is subjected to serial / parallel conversion by a serial / parallel (S / P) converter 305, and becomes a data sequence transmitted to each subcarrier. This parallel data sequence is subjected to a mapping process in a mapping circuit 304, and is input to a subcarrier selection unit 303. The subcarrier selection unit 303 is a circuit that determines which of the branches 1 and 2 is to be used to transmit a transmission signal for each subcarrier. An antenna branch used for transmission is determined for each subcarrier based on the “selection signal”.
[0010]
Here, a “branch selection signal” from the reception level magnitude comparison unit 203 at the time of reception is used as a branch selection signal used at the time of transmission. This is because when transmission is performed in the base station apparatus using the “branch selection signal” at the time of reception, it is considered that the reception power at the terminal that is the communication partner is maximized. For example, when the reception levels in the branch 1 and the branch 2 at the time of reception are as shown in FIGS. 3 and 4, respectively, the sub-level transmitted in the branch 1 using the “branch selection signal” at the time of reception. The carriers are # 1, # 3, # 4, # 5 and # 6 (see FIG. 6), and the subcarrier transmitted in branch 2 is # 2 (see FIG. 7). As a result, the reception level at the terminal is as shown in FIG. 8, and it is understood that the "branch selection signal" at the time of reception may be used at the time of transmission.
[0011]
Subcarrier selection section 303 determines a branch to be used for transmission for each subcarrier based on the “branch selection signal” from reception level magnitude comparison section 203. The subcarrier information signals used for branch 1 and branch 2 determined by subcarrier selection section 303 are input to modulation section 301 and modulation section 302, respectively. As shown in FIG. 17, the modulation units 301 and 302 include an up-converter 4, a D / A converter 5, and an IFFT (Inverse Fast Fourier Transform) circuit 6.
[0012]
In modulation section 301, the subcarrier information signal for branch 1 from subcarrier selection section 303 is input to IFFT circuit 6 shown in FIG. The IFFT circuit 6 performs OFDM modulation on the input subcarrier information signal for branch 1 by performing IFFT processing. The OFDM-modulated transmission signal is input to a D / A (Digital / Analog) converter 5. In the D / A converter 5, the input transmission signal, which is a digital value, is converted into an analog signal, frequency-converted into an RF band signal in the up-converter 4, and transmitted using the transmission / reception antenna 101.
[0013]
Similarly, in modulation section 302, the subcarrier information signal for branch 2 from subcarrier selection section 303 is subjected to OFDM modulation, analog signal conversion, and frequency conversion, and transmitted using transmission / reception antenna 102. As described above, when transmission diversity is applied in the base station apparatus, when each branch at the time of reception has the reception levels shown in FIGS. 3 and 4, the branch having the maximum reception level in each subcarrier is selected. By selecting the subcarrier to be transmitted in each branch as shown in FIG. 6 and FIG. 7 using the selection information at the time of transmission, the reception level of the terminal as the communication partner becomes as shown in FIG. The reception quality can be improved without performing the processing.
[0014]
For example, in an apparatus that has a first level detection unit and a second level detection unit and detects the reception level of a signal transmitted by each carrier for the first branch and the second branch, the reception level is the maximum in all branches. There is a device having a counter for calculating the total number of carrier waves, and a selector for selecting a transmission branch for transmitting each carrier based on each total number (for example, see Patent Document 1).
[0015]
[Patent Document 1]
JP 2001-94530 A
[0016]
[Problems to be solved by the invention]
However, in a multicarrier wireless communication apparatus that performs transmission diversity, the number of subcarriers used for transmission in each branch changes depending on the reception situation, and thus the number of subcarriers selected in a specific branch may be biased. This will be described with reference to FIGS. Here, the number of branches is 2, and the number of all subcarriers is 6. FIG. 3 and FIG. 4 show the reception levels of the respective subcarriers in branch 1 and branch 2, respectively, and # 1 to # 6 indicate the subcarrier numbers. In this case, when the reception levels of the subcarriers of the branch 1 and the branch 2 are compared, the reception level of the branch 2 is higher for the subcarrier # 2, and the reception of the branch 1 is higher for the other subcarriers. It can be seen that the level increases.
[0017]
Therefore, when subcarriers at the time of transmission are selected based on the reception result and transmission diversity is performed, the subcarriers transmitted in branch 1 and branch 2 are as shown in FIGS. It can be seen that the subcarriers are biased toward the subcarriers. As described above, when the number of subcarriers selected in a specific branch is biased, the total number of subcarriers increases, so that the peak power at the specific antenna increases.
[0018]
The present invention is directed to a transmission diversity system that can reduce the peak power in all branches by reducing the bias in the number of subcarriers selected in each branch without impairing the reception characteristics of a terminal that is a communication partner. It is an object of the present invention to provide a multi-carrier wireless communication device that performs the following.
[0019]
[Means for Solving the Problems]
According to one aspect of the present invention, in a wireless communication system of a time division duplex communication system using a multicarrier signal having a number of carrier waves M (M is a natural number of 2 or more), K (K is M ≧ K) A communication device provided with (a certain natural number) shared transmission / reception antennas, a carrier reception level measuring means for measuring a reception level of each received signal for each carrier in each of the shared transmission / reception antennas used for reception; An antenna-specific carrier allocation determining means for allocating a shared transmission / reception antenna for each carrier as a shared transmission / reception antenna at the time of transmission, wherein the maximum value of the number of carriers assignable to each shared transmission / reception antenna used at the time of transmission is represented by S _k (S _k Is M-1 ≧ S _k Provided is a communication apparatus having: a carrier assignment determination unit for each antenna that determines an assignment within a range of a carrier assignment number limit limited to a natural number of ≧ M / N1).
[0020]
In the communication device, within the limit of the number of carriers that can be allocated for the antenna, in order to perform the allocation of the carrier wave so as not to exceed the maximum allowable value when transmitting using a high reception level antenna for each carrier, It is possible to correct the bias in the assignment of the number of carriers for each antenna, which varies according to the reception state, while maintaining the transmission characteristics.
[0021]
In the determination of the carrier assignment for each antenna, it is preferable to determine the assignment in such a direction as to reduce the bias of the number of carriers assigned to each of the transmission / reception shared antennas when each carrier component of the multicarrier signal is frequency-divided and transmitted. For example, if the threshold value S is a minimum natural number equal to or greater than M / N2, the bias can be corrected.
[0022]
Regarding carriers that are excessively allocated in the carrier over-allocation antenna, the first reception level of each carrier in the carrier over-allocation antenna measured by the carrier reception level measuring unit, and the carrier over-allocation in the carrier additionally allocable antenna Carrier reception level difference calculation means for calculating a difference between the second reception level of a carrier corresponding to each carrier allocated from the antenna, and a reception level difference of each carrier measured by the carrier reception level difference calculation means A carrier assignment change priority assigning means for assigning a priority as a candidate for assignment change of a carrier at the time of transmission in the ascending order of the reception level difference of each carrier with respect to the carrier additional assignable antenna. Provided, carrier over-allocated antenna Of dude each assigned carrier, preferably determined based on the carrier to change the assigned antenna to the priority.
[0023]
By determining the priority of the carrier allocation change in the order of smaller reception level difference, it is possible to reduce the peak power at each transmitting antenna while preventing the transmission characteristics from deteriorating. Further, the S _k Is automatically changed in a direction in which the deviation of the number of carrier waves for each antenna decreases in accordance with the reception condition, the deviation can be reduced at any time according to the reception condition.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the embodiment of the present invention, an OFDM wireless communication system is assumed as a multicarrier wireless communication system, and the number of antenna branches used in the OFDM wireless communication system is set to two and the number of subcarriers is set to 52.
[0025]
First, an OFDM communication device according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a block diagram illustrating a configuration example of the OFDM communication device according to the first embodiment of the present invention. In the first embodiment, a case will be described where the OFDM communication apparatus shown in FIG. 2 is mounted on a base station apparatus. Further, in the first embodiment of the present invention, an operation in the case where the reception levels at the branches 1 and 2 are as shown in the upper diagram of FIG. 11 will be described. As shown in FIG. 2, the difference between the OFDM communication apparatus according to the present embodiment and the general OFDM communication apparatus shown in FIG. 1 is a method of determining a “branch selection signal” for transmission. Hereinafter, a method of determining the “branch selection signal” according to the present embodiment will be described in detail focusing on differences from FIG.
[0026]
As shown in FIG. 2, reception level measurement section 201 measures the reception level of each subcarrier from demodulation section 103 received in branch 1. The measured value is input to the reception level comparison section 203. Similarly, reception level measurement section 202 measures the reception level of each subcarrier from demodulation section 104 received in branch 2. The measured value is also input to the reception level comparison section 203.
[0027]
The reception level comparison section 203 compares the reception levels for each subcarrier based on the measurement values from the reception level measurement section 201 and the reception level measurement section 202. The result of this comparison is output as a “branch selection signal”, input to the subcarrier combining section 105 as a branch selection signal for reception, and used by the counter 204 and the subcarrier polarity inversion section 206 to determine a branch selection signal for transmission. Is input to
[0028]
Here, the “branch selection signal” is, for example, a comparison between the reception levels of the subcarriers of the branch 1 and the branch 2 for each subcarrier, and “1” when the reception level of the subcarrier of the branch 1 is high, Conversely, when the reception level of the subcarrier of the branch 2 is high, the signal is set to “0”, so that it is determined which branch is to be selected. When the reception level of each subcarrier in the branch 1 and the branch 2 is in the state shown in FIG. 11, the “branch selection signal” is as shown in the lower diagram of FIG. 11 (“111... 1100... 00”). . The counter 204 calculates the total number of subcarriers selected for each branch from the “branch selection signal” from the reception level comparison section 203. This calculation result is input to the magnitude comparison unit 205 as a “subcarrier total number signal”. The input “branch selection signal” is shown in the lower diagram of FIG. 11. In the example shown in FIG. 11, the “subcarrier total number signal” of branch 1 is “30”, and the “subcarrier total number signal” of branch 2 is “30”. Becomes “22”.
[0029]
The magnitude comparison unit 205 compares the magnitude of the “subcarrier total number signal” for each branch from the counter 204 with a preset threshold value S. Here, the threshold value S indicates the maximum value of the total number of subcarriers to be transmitted in each branch, and can be changed according to various environments. In the present embodiment, an example in which this threshold value is set to S = 26 will be described.
[0030]
[Table 1]

[0031]
Table 1 shows the correspondence of the output signal to the input signal of the magnitude comparison unit 205. In Table 1, assuming that the “subcarrier total number signal” input from the counter 204 is m and the threshold is S, if m> S, the difference (m−S) is represented by the “polarity inversion number signal , And if m ≦ S, 0 is output as the “polarity inversion number signal”. This “polarity inversion number signal” is input to the subcarrier polarity inversion unit 206. Here, the “subcarrier total number signal” of the branch 1 is “30”, and 30> 26. Therefore, the “polarity inversion number signal” which is the output result is “4” for the branch 1. On the other hand, since the “subcarrier total number signal” of the branch 2 is “22” and 22 <26, the “polarity inversion number signal” which is the output result is “0” for the branch 2.
[0032]
The subcarrier polarity reversing unit 206 determines the number of branches and the number of subcarriers for performing the polarity reversal process (the process of changing the branch selected for a certain subcarrier) based on the “polarity reversal number signal” from the magnitude comparison unit 205. Is done. The value of the “polarity inversion number signal” of each branch is “4” in the branch 1 and “0” in the branch 2, and thus “4” of the “30” subcarriers in which the branch 1 is selected. Polarity inversion is performed for "subcarriers". As for the branch 2, since the “polarity inversion number signal” is “0”, the polarity inversion is not performed.
[0033]
As a subcarrier to be subjected to the polarity inversion in the branch 1, a number having a smaller subcarrier number is preferentially inverted among subcarriers in which the branch 1 is selected. FIG. 12 shows the state of inversion. The polarity inversion is performed on the subcarriers # 1 to # 4 having the younger subcarrier numbers for which the branch 1 is selected, and as a result, the branch 2 is selected for the subcarriers # 1 to # 4. The result of the polarity inversion processing is input to the subcarrier selection unit 303 as a “branch selection signal” for transmission.
As described above, the base station apparatus selects a subcarrier to be transmitted at the time of transmission based on the reception level of the subcarrier of each branch at the time of reception, and as a result, the subcarriers are concentrated and selected at a specific branch. In this case, a part of the subcarriers in the specific branch can be transmitted using a branch other than the specific branch. Therefore, the peak power in each branch can be reduced as compared with an OFDM communication apparatus that performs normal transmission diversity.
[0034]
Next, a communication technique according to a second embodiment of the present invention will be described with reference to the drawings. In the communication technique according to the first embodiment, the transmission diversity is generally performed in the subcarrier polarity inversion unit 206 shown in FIG. There is a problem that the receiving characteristic of a terminal serving as a communication partner deteriorates more than a simple OFDM communication device. That is, in the above-described first embodiment, the selection of the subcarrier whose polarity is to be inverted is arbitrary, whereas in the communication technique according to the second embodiment, the subcarrier selection in consideration of the reception situation is performed. There is a characteristic in that it is performed. The communication technology according to the present embodiment will be described with reference to FIG. Note that the description will be given on the assumption that the reception situation of the base station apparatus is the situation shown in FIG.
[0035]
As shown in FIG. 9, reception level measurement section 401 measures the reception level of each subcarrier from the FFT circuit in demodulation section 103. The measured value is input to the reception level comparison section 402. Further, reception level measurement section 411 measures the reception level of each subcarrier from the FFT circuit in demodulation section 104. The measured value is input to the reception level comparison section 402. The reception level comparison section 402 compares the reception levels for each subcarrier based on the input values from the reception level measurement section 401 and the reception level measurement section 411. The comparison result is input as a “branch selection signal” to the subcarrier combining unit 105, the counter 403, the sort circuit 405, and the subcarrier polarity inverting unit 407. Here, when the reception state of the base station apparatus is in the state shown in the upper diagram of FIG. 11, the “branch selection signal” of each subcarrier is as shown in the lower diagram of FIG.
[0036]
In addition, the reception level comparison section 402 receives a subcarrier obtained by subtracting the reception level of the branch 2 from the reception level of the branch 1 for each subcarrier based on the measurement results of the reception level measurement section 401 and the reception level measurement section 411. A level difference is calculated. This calculation result is input to the sorting circuit 405 as a “reception level difference signal”. The counter 403 calculates the total number of subcarriers in which the branch 1 has been selected based on the “branch selection signal” from the reception level magnitude comparison section 402. This calculation result is input to the comparison unit 404 and the polarity inversion determination unit 406 as a “subcarrier total number signal”. In the case of FIG. 11, the “subcarrier total number signal” of each branch is “30”.
[0037]
The comparison unit 404 calculates a difference between the “subcarrier total number signal” from the counter 403 and a preset threshold value S, respectively, and thereby “polarity inversion” indicating the number of subcarriers for which polarity inversion is performed in each branch. A number signal is generated. The generated “polarity inversion number signal” is input to the polarity inversion determining unit 406. The threshold value S indicates the maximum number of subcarriers to be transmitted in each branch. In the case of FIG. 11, the “polarity inversion number signal” is “4”. In the sorting circuit 405, based on the “reception level difference signal” of each carrier from the reception level comparison section 402, the rearrangement processing is performed in order from the subcarrier having the highest reception level. At that time, a "sort subcarrier number signal" is generated in which the subcarrier numbers of the subcarriers having the larger "reception level difference signal" are sequentially output. As a result, the “sort subcarrier number signal” is input to the polarity inversion determining unit 406. In the case of the reception level of FIG. 11, the “reception level difference signal” rearranged by the sorting circuit 405 is as shown in FIG.
[0038]
The polarity inversion determination unit 406 determines a branch in which the “polarity inversion number signal” from the comparison unit 404 has a positive value as a branch for performing the subcarrier polarity inversion processing. Further, the number of subcarriers for performing the polarity inversion processing is determined by the value of the “polarity inversion number signal”. Here, the “subcarrier total number signal” is m, the “polarity inversion number signal” is n, and the threshold value is S. When the branch on which the polarity inversion processing of the subcarriers is performed is the branch 1, that is, when m ≧ S, the subcarriers having the small reception level difference between the branches in the branch 1 and the n subcarriers are set as the polarity inversion targets. Selected as a subcarrier. This is equivalent to the fact that the subcarriers of the subcarrier numbers corresponding to the sort numbers S to m of the “sort subcarrier number signal” are subject to polarity inversion.
[0039]
When the branch on which the subcarrier polarity inversion processing is performed is the branch 2, that is, when m <S, the polarity inversion is performed for n subcarriers from the branch having the smallest reception level difference between the branches in the branch 2 to n. Select as subcarrier. This is equivalent to the fact that the subcarriers of the subcarrier numbers corresponding to S from the sort numbers m to S of the “sort subcarrier number signal” are to be subjected to polarity inversion. By the above processing, the subcarrier number to be the polarity inversion target is determined, and the result is input to the subcarrier polarity inversion unit 407 as “polarity inversion number signal”.
[0040]
The subcarrier polarity inversion unit 407 performs a polarity inversion process on the “branch selection signal” from the reception level magnitude comparison unit. At this time, the polarity inversion processing is performed on the subcarrier of the subcarrier number indicated by the “polarity inversion number signal” from the polarity inversion determining unit 406.
[0041]
The “branch selection signal” whose polarity has been inverted by the above processing is output to the subcarrier selection unit 408 as a branch selection signal for transmission. In the example illustrated in FIG. 11, the polarity inversion is performed on four subcarriers among the subcarriers of branch 1 based on the “polarity inversion number signal”. Further, the polarity inversion is performed on the subcarriers of subcarrier numbers # 30, # 29, # 28 and # 27 from which the branch 1 is selected from the "subcarrier number signal". As a result, the “branch selection signal” becomes as shown in FIG.
[0042]
As described above, the base station apparatus according to the present embodiment, when subcarriers are collectively selected in a specific branch, within the specific branch, reception between other branches A subcarrier having a small level difference is transmitted using a branch other than the specific branch. Therefore, there is an advantage that the peak power in each transmission branch can be reduced without deteriorating the reception characteristics of the terminal as the communication partner.
[0043]
Next, a communication technique according to a third embodiment of the present invention will be described with reference to the drawings. When the communication technique according to the second embodiment is used, the sorting circuit 405 shown in FIG. 9 needs to perform processing for rearranging the “reception level difference signal”. Since this processing includes the rearrangement processing of analog values, the circuit scale increases as the number of branches or the number of used subcarriers increases.
[0044]
The communication technique according to the present embodiment is characterized in that when performing the polarity inversion processing, the rearrangement processing is performed by referring only to the “branch selection signal” without using the “reception level difference signal”. Hereinafter, the principle of the polarity inversion processing in consideration of the reception state using only the “branch selection signal” will be described with reference to FIG. When the reception situation in the base station apparatus is shown in the upper diagram of FIG. 11, the reception levels of branch 1 and branch 2 are reversed between subcarrier number # 30 and subcarrier number # 31. Understand. Thus, the reception level difference between the sub-carriers of sub-carrier number # 30 and sub-carrier number # 31 at which the selected branch is switched is smaller than that of the other sub-carriers. In the communication technology according to the present embodiment, as described above, the subcarriers on which the selected branch is switched focus on the point that the reception level difference between the branches becomes smaller, and when the subcarrier polarity of the “branch selection signal” is inverted, By preferentially inverting the polarity of the subcarrier whose selected branch is switched, it is possible to use only the “branch selection signal” and realize the branch selection of each subcarrier in consideration of the reception situation.
[0045]
FIG. 10 is a block diagram of the OFDM communication apparatus according to the present embodiment. Here, a case where the OFDM communication apparatus shown in FIG. 10 is mounted on a base station apparatus will be described. However, the threshold value S indicating the maximum number of selectable subcarriers in each branch will be described in the case where S = 26, which is a half of the total number 52 of subcarriers. As shown in FIG. 10, reception level measurement section 201 measures the reception level of each subcarrier in branch 1 input from demodulation section 103. The measured value is input to the reception level comparison section 203. Further, reception level measurement section 202 measures the reception level of each subcarrier in branch 2 input from demodulation section 104. The measured value is also input to the reception level comparison section 203. The reception level comparison section 203 compares the reception levels for each subcarrier based on the measurement values from the reception level measurement section 201 and the reception level measurement section 202. This comparison result is output as a “branch selection signal” and output to the subcarrier combining section 105 and the subcarrier polarity inverting section 503.
[0046]
The “branch selection signal” in the present embodiment compares the reception level of the subcarriers of branch 1 and branch 2 for each subcarrier, and sets “1” when the reception level of the subcarrier of branch 1 is high, Conversely, when the reception level of the subcarrier of the branch 2 is high, the signal is a signal indicating selection of a branch to be set to “0”. Here, FIG. 19 shows a circuit configuration diagram of the subcarrier polarity inverting section 504 in which a transmission branch selection signal is generated, and its operation will be described with reference to a flowchart shown in FIG.
[0047]
In FIG. 19, reference numerals 1001, 1004, 1005, 1007, 1008, and 1010 indicate XNOR gate circuits, reference numerals 1002, 1009, 1013, 1014, and 1116 indicate AND gate circuits, and reference numerals 1003, 1006, and 1011 indicate D flip-flops. Reference numeral 1012 denotes an inverter circuit, and reference numeral 1015 denotes an OR gate circuit. The “branch selection signal” input from the reception level comparison unit 203 illustrated in FIG. 10 is input to the storage device 901 and the counter 902 illustrated in FIG. The storage device 901 has a 52 × 1 bit memory area for storing the “branch select signal”, and the “branch select signal” for 52 subcarriers is, for example, from address 1 of this memory area. The addresses are sequentially stored up to the address 52 (see step 701 in the flowchart of FIG. 15).
[0048]
Next, the value of the “branch selection signal” is output to the circuit 1108 in order from address 1 of the storage device 901. However, when reading a value from the storage device 901, the value is always read from address 1 to address 52, and the storage device 901 operates at 53 clock cycles. In the storage device 901, the “branch selection signal” is output to the circuit 1108, and the “branch selection signal” subjected to the polarity inversion processing is input from the circuit 1109. The polarity of each subcarrier is updated by the input “branch selection signal”. However, when the value from the circuit 1109 is stored in the storage device 901, the value from the circuit 1109 is stored only at the clock timing when the signal (S5) shown in FIG. 20 becomes “1”. In other words, the update of the value of the address 1 is started from the second clock, and the update up to the address 52 is completed in the 53rd clock. Finally, the operation of the storage device 901 in the 53 clock cycle refers to the value of the signal S4 from the comparison unit 907 at the 53rd clock, and ends when the signal S4 is “0”.
[0049]
The counter 902 counts the total number m of subcarriers from which the branch 1 has been selected based on the input “branch selection signal” (step 702). This output result m is input to the subtractor 903 and the comparison unit 106 as a “subcarrier total number signal”. The subtractor 903 calculates a difference h between the “subcarrier total number signal” m input from the counter 902 and the threshold 26. In the present embodiment, since the threshold value is 26, h = m−26 (step 705). This h is input to the absolute value calculation unit 904 and the sign determination unit 905. The absolute value calculator 904 calculates the absolute value i of h input from the subtractor 903 (step 705). This absolute value i indicates the required number of polarity inversions, and is input to the comparison unit 907 as a “polarity inversion number signal”. The sign determination unit 905 determines whether the sign of h from the subtractor 903 is positive or negative. As a result of the determination, a signal S1 indicating a code of “0” when h ≧ 0 and “1” when h <0 is generated (step 711) and input to the circuit 1001. Here, the signal S1 is a signal indicating which of the total number of the polarity “0” and the polarity “1” in each subcarrier of the “branch selection signal” is larger, and when the polarity “0” is larger (h <0). S1 = 1) indicates that the polarity inversion processing is performed to change the polarity “0” to the polarity “1”, and when the polarity “1” is large (h ≧ 0, S1 = 0), the polarity “1” Indicates that a polarity inversion process is performed to change the polarity to “0”.
[0050]
The comparing section 1106 outputs “1” when the “subcarrier total number signal” m from the counter 902 is “0” or “52”, and outputs “0” otherwise. The output result S2 is input to the circuit 1111. Here, when m = 0 or m = 52, there is no subcarrier whose branch to be selected is switched, so that the polarity inversion processing cannot be performed. In this case, the signal is transmitted to the circuit 1108 which performs the polarity inversion processing so as to perform the polarity inversion processing in such a case (step 703).
[0051]
The circuit 1108 includes a counter 1110, a circuit 1111, a circuit 1112, a circuit 1113, and a circuit 1114. The circuit 1108 receives a “branch selection signal” from the storage device 901, the signal S 1 from the sign determination unit 905, and the signal S 2 from the comparison unit 1106 as input signals. The polarity of the “branch selection signal” is inverted according to the input signals S1 and S2. The principle of operation will be described below.
[0052]
In the circuit 1111, the polarity of the subcarrier number # j + 1 of the input “branch selection signal” is compared with the polarity of the subcarrier number #j one clock before. If the polarities are the same, a signal "0" for not performing the polarity inversion is output (step 707). This output result is input to counter 1110 and circuit 1114. The counter 1110 counts the number of times that the circuit 1108 determines that polarity inversion is necessary based on the signal input from the circuit 1111.
[0053]
However, the count of the number of polarity inversions is performed only at the clock timing when the input signal S6 shown in FIG. 18 becomes "1" (step 715). The counted result S3 is input to the comparing unit 907.
[0054]
The circuit 1114 determines a timing at which the polarity inversion processing can be performed according to the input signal S6. As shown in FIG. 18, the signal S6 is “0” at the first and 53rd clock timings, and therefore, at these two clock timings, regardless of the value of the signal input from the circuit 1111. A signal for controlling not to perform the polarity inversion processing is generated. This output result is output to circuits 1112 and 1113.
[0055]
In the circuits 1112 and 1113, when the signal input from the circuit 1114 is "0", the polarity inversion processing is not performed, and when the signal is "1", the polarity inversion processing of the subcarrier number #j or # j + 1 is performed. . At this time, since the polarities of the subcarrier numbers #j and # j + 1 are different, the polarity of one of the subcarrier numbers #j and # j + 1 is inverted. The criterion is a signal S1 from the sign determination unit that indicates which polarity of “0” or “1” in the “branch selection signal” is larger (step 712). When the signal S1 is “0”, that is, when the “branch selection signal” has a large number of polarities “1”, the subcarrier having a polarity “1” among the polarities of the subcarrier numbers #j and # j + 1 A polarity inversion process is performed (step 713). Conversely, when the signal S1 is “1”, that is, when the polarity of the “branch selection signal” has many “0”, the subcarrier having the polarity “0” among the polarities of the subcarrier numbers #j and # j + 1 Is subjected to a polarity reversal process (step 714). As a result, a “branch selection signal” on which the polarity inversion processing has been performed is output and input to the circuit 1109.
[0056]
The comparison unit 907 compares the “polarity inversion number signal” i from the absolute value calculation unit 904 with the signal S3 from the counter 1110. Assuming that the value of S3 is k, the comparison unit 907 outputs “1” when i−k> 0, and outputs “0” when i−k ≦ 0. This output result is input to the circuit 1109 and the storage device 1115 as a signal S4. The signal S4 indicates whether or not the polarity inversion processing is necessary. When S4 = “1”, it indicates that the polarity inversion processing is required. When S4 = “0”, the polarity inversion processing is required. It is not.
[0057]
In the circuit 1109, based on the signal S4 indicating the presence / absence of the polarity inversion processing from the comparison unit 907, either of the “branch selection signal” subjected to the polarity inversion processing or the “branch selection signal” not subjected to the polarity inversion processing as an output It is determined whether to output. When S4 = 1, a "branch selection signal" subjected to the polarity inversion processing is output, and when S4 = 0, a "branch selection signal" not subjected to the polarity inversion processing is output. This output result is input to the storage device 901 and the storage device 1115.
[0058]
The storage device 1115 has a 52 × 1 bit memory for storing the “branch selection signal” from the circuit 1109, and only at the clock timing when the input signal S5 shown in FIG. 20 becomes “1”. Is stored in Further, in the storage device 1115, the “branch selection signal” is stored in order from the second clock by the signal S5 from the address 1 and is stored up to the address 52 in the 53rd clock. The end of the operation in the storage device 1115 is the same as that of the storage device 901, referring to the value of the signal S4 from the comparison unit 907 at the 53rd clock, and ending the operation when S4 is “0” (step 716).
[0059]
As described above, the base station apparatus according to the present embodiment can perform transmission diversity that suppresses the peak power of each branch without deteriorating the reception characteristics of the terminal as the communication partner. Further, there is an advantage that the circuit configuration is very simple and the device can be realized with a small circuit scale.
[0060]
Next, a communication technique according to a fourth embodiment of the present invention will be described with reference to the drawings. In the communication technology according to the third embodiment of the present invention, 26, which is half of the total number 52 of subcarriers that can minimize the peak power of each branch, is a threshold indicating the maximum number of selectable subcarriers of each branch. Although used as a value, in the present embodiment, “the maximum number of subcarriers” can be arbitrarily selected.
[0061]
The OFDM communication apparatus according to the present embodiment has a configuration similar to that of the OFDM communication apparatus according to the third embodiment, and only the circuit configuration of the subcarrier polarity inversion unit 504 changes in FIG. FIG. 21 shows the circuit configuration of the subcarrier polarity inverting unit according to the present embodiment, and FIG. 22 is a flowchart showing the operation flow. The difference between the device according to the present embodiment and the device according to the third embodiment is that i is the output result of the absolute value calculation unit 904 in FIG. 19, the output signal S1 of the sign determination unit 905 and the output of the comparison unit 1106. And a method for calculating the signal S2. The procedure for calculating i and the signals S1 and S2 will be described below.
[0062]
In counter 1301, based on the “branch selection signal” input from reception level magnitude comparing section 203 shown in FIG. 10, total number m1 of subcarriers in which branch 1 is selected and total number of subcarriers in which branch 2 is selected m2 is counted (FIG. 22: step 702a). The output result m1 is input to the subtractor 1302 and the comparing unit 1405, and m2 is input to the subtractor 1303. The subtractor 1302 calculates a difference h1 between m1 from the counter 1301 and the “maximum number of subcarriers” a (step 705). This h1 (= m1-1) is input to the magnitude comparison unit 1304. The subtractor 1303 calculates a difference h2 between m2 from the counter 1301 and the “maximum number of subcarriers” a (step 705). This h2 (= m2-a) is input to the magnitude comparison unit 203 (FIG. 10). The magnitude comparing section 203 shown in FIG. 10 compares the magnitude of the signal h1 from the subtractor 1302 with the magnitude of the signal h2 from the subtractor 1303, and outputs the larger signal. This output result is input to the comparison unit 1204 as a “polarity inversion number signal” i. In addition, the magnitude comparison unit 203 (FIG. 10) generates a signal S1 that sets S1 = 0 when h1 ≧ h2 and sets S1 = 1 when H1 <h2. This signal S1 is input to the circuit 1308.
[0063]
The comparator 1405 outputs “1” when the value of the signal m1 from the counter 1301 is “0” or “52”, and outputs “0” otherwise (step 703). This output result S2 is input to the circuit 1311. The above processing is different from that of the third embodiment, and the other processing is the same as that of the third embodiment. As described above, by using the circuit configuration shown in FIG. 21, the number of subcarriers can be selected so as not to exceed the maximum number of subcarriers set in each branch, and the peak power in each branch can be suppressed. .
[0064]
Further, in this embodiment, the circuit configuration is very simple, and the device can be implemented with a small circuit scale.
As described above, the present invention has been described in accordance with the embodiments. However, it is needless to say that the present invention is not limited to these examples, and various modifications are possible.
[0065]
【The invention's effect】
According to the present invention, there is provided a communication device that reduces peak power at each transmission antenna without deteriorating error rate characteristics of a communication partner in a communication system that performs communication by simultaneously using a plurality of carriers to which transmission diversity is applied. Becomes possible. Further, it is possible to provide a communication device that reduces the peak power at each transmission antenna without deteriorating the error rate of the communication partner.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration example of a general communication device.
FIG. 2 is a diagram illustrating a configuration example of a communication device according to the first embodiment of the present invention.
FIG. 3 is a diagram illustrating an example of a reception level of each subcarrier of a branch 1 of the communication device according to the first embodiment of the present invention (the horizontal axis is frequency).
FIG. 4 is a diagram illustrating an example of a reception level of each subcarrier of a branch 2 of the communication device according to the first embodiment of the present invention (the horizontal axis is frequency).
FIG. 5 is a diagram showing a reception level of each subcarrier after combining of the communication device according to the first embodiment of the present invention (the horizontal axis is frequency).
FIG. 6 is a diagram showing a transmission level of each subcarrier of branch 1 of the communication device according to the first embodiment of the present invention (the horizontal axis is frequency).
FIG. 7 is a diagram illustrating a transmission level of each subcarrier of branch 2 of the communication device according to the first embodiment of the present invention (the horizontal axis is frequency).
FIG. 8 is a diagram illustrating a reception level of each subcarrier in a terminal device of a communication partner according to the first embodiment of the present invention (the horizontal axis is frequency).
FIG. 9 is a diagram illustrating a configuration example of a communication device according to a second embodiment of the present invention.
FIG. 10 is a diagram illustrating a configuration example of a communication device according to a third embodiment of the present invention.
FIG. 11 is a diagram illustrating an example of the reception level of each subcarrier when the number of branches is 2 and the total number of subcarriers is 52.
FIG. 12 is a diagram illustrating an example of a “branch selection signal” after application of the communication technique according to the first embodiment of the present invention (the horizontal axis is frequency).
FIG. 13 is a diagram illustrating a “reception level difference signal” in which reception level differences between one branch are rearranged in descending order for each subcarrier according to the second embodiment of the present invention (the horizontal axis is frequency).
FIG. 14 is a diagram illustrating an example of a “branch selection signal” of the communication device according to the second embodiment of the present invention (the horizontal axis represents frequency).
FIG. 15 is a flowchart illustrating a flow of a process of determining a subcarrier selected at the time of transmission for each branch in the communication device according to the third embodiment of the present invention.
16 shows details of demodulation sections 103 and 104 in FIG. 1, demodulation sections 103 and 104 in FIG. 2, demodulation sections 103 and 104 in FIG. 9, and demodulation sections 103 and 104 in FIG. Device configuration diagram
FIG. 17 is a diagram showing an example of the internal configuration of each of the two modulators shown in FIGS. 1, 2, 9 and 10;
FIG. 18 is a diagram illustrating a waveform example of a signal S6.
FIG. 19 is a diagram illustrating a circuit configuration example of a subcarrier polarity inversion unit 204 in FIG. 10 in a communication device according to a third embodiment of the present invention.
FIG. 20 is a diagram illustrating a waveform example of a signal S5.
FIG. 21 is a diagram illustrating a circuit configuration example of a subcarrier polarity inversion unit 204 in FIG. 10 in a communication device according to a fourth embodiment of the present invention.
FIG. 22 is a flowchart illustrating a flow of a process of determining a subcarrier selected at the time of transmission for each branch of the communication device according to the fourth embodiment of the present invention.
[Explanation of symbols]
101, 102: transmission / reception antennas, 103, 104: demodulation device, 105: subcarrier synthesis unit, 106: demapping unit, 107: P / S modulation unit, 201, 202: reception level measurement unit, 203: reception level

Claims (11)

A wireless communication system of a time division duplex communication system using a multi-carrier signal having a number of carrier waves M (M is a natural number of 2 or more) is provided with K (K is a natural number satisfying M ≧ K) shared transmission / reception antennas. Communication device,
Carrier reception level measuring means for measuring the reception level of each carrier of the received signal in each of the transmission and reception shared antenna used for reception,
The highest shared reception / transmission antenna, the antenna-specific carrier assignment determination means for allocating each carrier as a shared transmission / reception antenna during transmission, and the maximum value of the number of carriers that can be assigned to each shared transmission / reception antenna used during transmission. A communication apparatus comprising: an antenna-based carrier assignment determination unit that determines assignment within a carrier assignment number limit limited to S _k (S _k is a natural number that satisfies M−1 ≧ S _k ≧ M / N1). Further, an antenna-specific carrier number counting means for counting the antenna-specific carrier number C _k assigned to each of the transceiving antenna,
Wherein said antenna by subcarriers number C _k is compared with the S _k, classifying the transceiving antenna, and carrier excess allocation antenna comprising a C _k> S _k, in the carrier added assignable antenna comprising a C k _{<S k} Means to
C _k of said transceiving antenna is, S out of the carriers assigned to the carrier excessively allocated antenna so as to satisfy the condition _k ≧ C _k, the carrier to determine the carrier to change the assignment of carriers to the carrier additional assignable antenna Assignment change determining means;
2. The communication apparatus according to claim 1, further comprising: a carrier assignment adjusting unit that changes the assignment of the carrier to the antenna capable of additionally assigning the carrier, the carrier whose change is determined by the carrier assignment change determining unit. The antenna-based carrier allocation determination is characterized in that, in the case where each carrier component of the multicarrier signal is frequency-divided and transmitted, the allocation is determined in a direction to reduce the bias of the number of carriers allocated to each of the transmission / reception shared antennas. The communication device according to claim 1, wherein For over-allocated carriers at the carrier over-allocated antenna,
The first reception level of each carrier in the carrier over-allocated antenna measured by the carrier reception level measuring means, and the first reception level of the carrier corresponding to each carrier allocated from the carrier over-allocated antenna in the carrier additional allocable antenna. A carrier reception level difference calculating means for calculating a difference between the reception level and the second reception level;
Based on the reception level difference of each carrier measured by the carrier reception level difference calculation means, the carrier allocation at the time of transmission is performed in the order of smaller reception level difference of each carrier to the additional carrier assignable antenna. Comprising a carrier assignment change priority assigning means for assigning a priority as a change candidate,
The communication apparatus according to claim 2, wherein, of the respective carriers assigned by the carrier over-assignment antennas, a carrier for which the assigned antenna is changed is determined based on the priority. For over-allocated carriers at the carrier over-allocated antenna,
3. The communication apparatus according to claim 2, wherein, when an antenna to which a carrier in an adjacent frequency domain is assigned is an antenna that can additionally assign a carrier, the antenna assignment is preferentially changed. The communication apparatus according to any one of claims 1, characterized in that it has a storage device for storing S _k for each transceiving antenna to 5. Further, the communication device according to the S _k, in claim 6, characterized in that the number of carriers deviation for each antenna has means for automatically changing the direction of smaller depending on the reception conditions. A wireless communication system of a time division duplex communication system using a multi-carrier signal having a number of carrier waves M (M is a natural number of 2 or more) is provided with K (K is a natural number satisfying M ≧ K) shared transmission / reception antennas. A communication method using a communication device,
Measuring a reception level for each carrier of a reception signal in each of the transmission / reception shared antennas used for reception,
This is a step of allocating a shared antenna having the highest reception level to each carrier as a shared antenna for transmission and reception at the time of transmission, and assigning the maximum value of the number of carriers that can be assigned to each shared antenna used for transmission at S _{k (S k} is a natural number of _{M-1 ≧ S k ≧ M} / N1) communication method and a antenna-specific carrier assignment determining step of determining the allocation within the scope of a carrier quota limitations limited to. A wireless communication system of a time division duplex communication system using a multi-carrier signal having a number of carrier waves M (M is a natural number of 2 or more) is provided with K (K is a natural number satisfying M ≧ K) shared transmission / reception antennas. Communication device,
A first transmitting and receiving antenna;
A second transmitting / receiving antenna;
A first reception level measurement unit that measures a reception level of a signal for each carrier received from the first transmitting / receiving antenna;
A second reception level measurement unit that measures a reception level of a signal for each carrier received from the second transmission / reception antenna;
A reception level comparison unit that compares a first reception level measured by the first reception level measurement unit and a second reception level measured by the second reception level measurement unit for each carrier;
A communication having a transmission antenna determining unit that determines which of the first transmitting and receiving antennas and the second transmitting and receiving antennas to use to transmit each carrier based on the comparison by the reception level comparing unit. apparatus. Furthermore, a sorting circuit is provided which sorts each subcarrier on the basis of the magnitude of the reception level based on the reception level difference of the subcarriers calculated by the reception level comparison unit, and transmits based on the sorting result. The communication device according to claim 8, wherein a subcarrier group for changing an antenna is determined. A wireless communication system of a time division duplex communication system using a multi-carrier signal having a number of carrier waves M (M is a natural number of 2 or more) is provided with K (K is a natural number satisfying M ≧ K) shared transmission / reception antennas. Communication device,
Carrier reception level measuring means for measuring the reception level of each carrier of the received signal in each of the transmission and reception shared antenna used for reception,
A communication apparatus comprising: an antenna-specific carrier assignment determination unit that assigns a shared transmission / reception antenna having the highest reception level as a shared transmission / reception antenna at the time of transmission for each carrier.

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