10.26.3.1 General 
Transmissions of HT PPDUs, referred to as HT transmissions, are protected if there are other STAs present that cannot interpret HT transmissions correctly. The HT Protection and Nongreenfield HT STAs Present fields in the HT Operation element within Beacon and Probe Response frames are used to indicate the protection requirements for HT transmissions.
HT PPDUの送信はHT送信が正しく解釈できないほかのSTAがいるときでも守られる。
Beacon, Probe Response?フレームのHT Operation element?の HTのProtectionとNongreenfield HT STAs PresentフィールドをHT送信を守る要求を示すのに使用する。
The HT Protection field may be set to no protection mode only if the following are true:
HT Protectionフィールドは下記が真のときにのみno protection modeがセットされる。
— All STAs detected (by any means) in the primary or the secondary channel are HT STAs, and
— All STAs that are known by the transmitting STA to be a member of this BSS are either
— 20/40 MHz HT STAs in a 20/40 MHz BSS, or
— 20 MHz HT STAs in a 20 MHz BSS.
The HT Protection field may be set to nonmember protection mode only if the following are true:
HT Protectionフィールドは下記が真の時のみnonmember protectionがセットされる
— A non-HT STA is detected (by any means) in either the primary or the secondary channel or in both the primary and secondary channels, that is not known by the transmitting STA to be a member of this BSS, and
— All STAs that are known by the transmitting STA to be a member of this BSS are HT STAs.
- non-HT STAがチャネルのprimary/secondaryの両方で発見された時。チャネルはこのBSSのメンバーに対して送信するSTAによって知られないもの
- このBSSメンバーに送信するSTAによって知られるすべてのSTAがHT STAである
The HT Protection field may be set to 20 MHz protection mode only if the following are true:
下記が真の時、HT Protection fieldが20MHz protection modeになる
— All STAs detected (by any means) in the primary channel and all STAs detected (by any means) in
the secondary channel are HT STAs and all STAs that are members of this BSS are HT STAs, and
— This BSS is a 20/40 MHz BSS, and
— There is at least one 20 MHz HT STA associated with this BSS.
- primary/secondary channelのすべてのSTAがHT STAであり、BSSの全STAがHT STAである
- このBSSは20/40 MHz BSSである
- このBSSに接続する20 MHz HT STAが最低1台存在する
The HT Protection field is set to non-HT mixed mode otherwise.
上記を満たさない場合、HT Protection fieldはnon-HT mixed modeになる。
これらのルールはいつでも適用される。
NOTE—The rules stated above allow an HT AP to select non-HT mixed mode at any time.
In an IBSS, the HT Protection field is reserved, but an HT STA shall protect HT transmissions as though the HT Protection field were equal to non-HT mixed mode. A STA that is a member of an IBSS shall protect HTgreenfield format PPDUs and RIFS sequences, adhering to the same requirements as described in the line of Table 10-13 labeled “Use_Protection = 0 or ERP element is not present (HT Protection field equal to non-HT mixed mode).”
IBSSでの話
| Condition | Requirements |
| Use_Protection = 0 or ERP element is not present (HT Protection field equal to non-HT mixed mode) | The protection requirements for HT transmissions using HTgreenfield format are specified in 10.26.3.1. The protection requirements for HT transmissions using RIFS within the HT transmission burst are specified in 10.26.3.3. The protection mechanism for other transmissions not already described above is based on one of the sequences defined in Table 10-14. |
In an MBSS, the HT Protection field and the Nongreenfield HT STAs Present field are determined as described in 10.26.3.5.
MBSSでの話
In an IBSS and an MBSS, the RIFS Mode field of the HT Operation element is reserved, but an HT STA shall operate as though this field were equal to 1.
IBSSとMBSSでの話
During the 40 MHz phase of PCO operation, a PCO active STA may act as though the HT Protection field were equal to no protection mode, regardless of the actual value of the HT Protection field transmitted by the AP.
PC0操作の40 MHzの間、PC0が有効なSTAはHT Protection フィールドがno protection modeと等しいものとしてふるまう。ただしAPによって送信されるHT Protection フィールドの値は考えない。
When the HT Protection field is equal to no protection mode or 20 MHz protection mode and the Nongreenfield HT STAs Present field is equal to 0, no protection is required since all HT STAs in the BSS are capable of decoding HT-mixed format and HT-greenfield format transmissions.
HT Protection フィールドのはno protection モードか20 MHz protection modeで、Nongreenfield HT STA Present フィールドが0のとき、no protection ではHT-mixed フォーマットとHT-green fieldフォーマットで送ることができる。
When the HT Protection field is equal to no protection mode or 20 MHz protection mode and the Nongreenfield HT STAs Present field is equal to 1, HT transmissions that use the HT-greenfield format shall be protected. This protection may be established by transmitting a PPDU with the TXVECTOR FORMAT parameter set to HT_MF or any of the methods described in Table 10-14.
HT Protection フィールドがno protectionモードか20 MHz protectionモードでNongreenfield HT STA Presentフィールドが1のとき、HT-greenfieldフォーマットは守られる必要がある。TXVECTOR FORMATパラメータをHT_MFにするか、下記表のいずれかの手段で送信される。
| HT protection mechanism |
| Control frames such as RTS/CTS or CTS-to-self prior to the HT transmissions: - 20 MHz transmissions use the rates defined in Clause 17 or Clause 18 - 40 MHz transmissions use non-HT duplicate frames defined in Clause 19 |
| L-SIG TXOP protection |
| As the first PPDU in the TXOP, send one of: - a non-HT PPDU containing a frame that requires an immediate response - an HT-mixed format at PPDU containing a frame that requires an immediate response in a non-HT PPDU |
| PPDUs after the first PPDU exchange may be HT-greenfield format PPDUs and/or be separated by RIFS. |
When the HT Protection field is equal to nonmember protection mode and the Use_Protection field in the ERP element is equal to 0, HT transmissions should be protected. When the HT Protection field is equal to nonmember protection mode, the Use_Protection field in the ERP element is equal to 0, and the Nongreenfield HT STAs Present field is equal to 1, HT transmissions using HT-greenfield format shall be protected. When the HT Protection field is equal to nonmember protection mode and the Use_Protection field in the ERP element is equal to 1, HT transmissions shall be protected according to the requirements described in Table 10-13.
HT Protectionフィールドがnonmember protectionモードでERPエレメントのUse_Protectionフィールドが0のとき、HT送信は守られる必要がある。HT Protectionフィールドがnonmember protection モードでERPエレメントが0、Nongreenfield HT STAs Presentフィールドが1のとき、HT-greenfieldフォーマット送信は守られる必要がある。HT Protectionフィールドがnonmember protectionモードで、ERPエレメントのUse_Protectionフィールドが1のとき、表10-13に従って守られる必要がある。
When the HT Protection field is equal to non-HT mixed mode, HT transmissions shall be protected. The type of protection required depends on the type of transmission as well as the type of the non-HT STAs that are present in the BSS. Protection requirements that apply when the HT Protection field is equal to non-HT mixed mode are described in Table 10-13.
HT Protectionフィールドがnon-HT mixed モードのとき、HT送信は守られる必要がある。BSSに存在するnon-HT STAsの種別が送信種別に依存する。その種別について表10-13参照。
If the transmission requires protection and the Use_Protection field within the ERP element is equal to 0 or the ERP element is not present in the Beacon, HT transmissions shall be protected using one of the mechanisms identified in Table 10-14.
NOTE—Rules for rate selection for the HT protection mechanisms listed in Table 10-14 are described in 10.7.
BeaconのERPエレメントのUse_Protectionフィールドが0かERPelementが存在しない、またprotectionを要求した送信の場合、HT送信は表10-14を用いて守られる必要がある。
表10-14は10.7?参照。
If the HT Protection field is equal to no protection mode and the Secondary Channel Offset field is equal to SCA or SCB, a STA may transmit a 40 MHz HT PPDU (TXVECTOR parameter CH_BANDWIDTH set to HT_CBW40) to initiate a TXOP provided that the restrictions specified in 10.7 are obeyed. When the HT Protection field is not equal to no protection mode or the Secondary Channel Offset field is equal to SCN, a STA shall not transmit a 40 MHz HT PPDU (TXVECTOR parameter CH_BANDWIDTH set to HT_CBW40) to initiate a TXOP.
HT Protectionフィールドがno protectionモードでSecondary Channel OffsetフィールドがSCA, SCBいずれかの場合、STAは10.7?記述の制限によりTXOPを初期化し40 MHz HT PPDUを送信する。これはTXVECTGORパラメータのCH_BANDWIDTHをHT_CBW40にする。
HT Protectionフィールドがno protection モードでない場合やSecondary Channel OffsetフィールドがSCNの場合は、STAは40 MHz HT PPDUでTXOPを初期化できない。
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