Doc.: IEEE 802.11-09/0992r18



IEEE P802.11

Wireless LANs

|Specification Framework for TGac |

|Date: 2010-09-16 |

|Author(s): |

|Name |Affiliation |Address |Phone |email |

|Robert Stacey |Intel |2111 NE 25th Ave, Hillsboro OR 97124, |503-724-0893 |robert.j.stacey@ |

| | |USA | | |

|Eldad Perahia |Intel |2111 NE 25th Ave, Hillsboro OR 97124, | |eldad.perahia@ |

| | |USA | | |

|Adrian Stephens |Intel | | |adrian.p.stephens@ |

|Assaf Kasher |Intel | | |assaf.kasher@ |

|Solomon Trainin |Intel | | |solomon.trainin@ |

|Michelle Gong |Intel | | |michelle.x.gong@ |

| Raja Banerjea |Marvell |5488 Marvell Lane, Santa Clara CA, |408.222.3713 |rajab@ |

| | |95054 | | |

|Hongyuan Zhang |Marvell |5488 Marvell Lane, Santa Clara CA, |408.222.1837 |hongyuan@ |

| | |95054 | | |

|Sudhir Srinivasa |Marvell |5488 Marvell Lane, Santa Clara CA, | |sudhirs@ |

| | |95054 | | |

|Yong Liu |Marvell |5488 Marvell Lane, Santa Clara CA, | |yongliu@ |

| | |95054 | | |

|Harish Ramamurthy |Marvell | | |harishr@harishr@marvell.co|

| | | | |m |

|Ning Zhang |Atheros |1700 Technology Drive, |408-773-5363 |Ning.Zhang@ |

| | |San Jose, CA 95110 | | |

|Youhan Kim |Atheros |1700 Technology Drive, | |Youhan,Kim@atheros,com |

| | |San Jose, CA 95110 | | |

|William McFarland |Atheros |1700 Technology Drive, | |William.McFarland@ |

| | |San Jose, CA 95110 | | |

|Kai Shi |Atheros |1700 Technology Drive, | |Kai.Shi@ |

| | |San Jose, CA 95110 | | |

|Joshua Zhao |Atheros |1700 Technology Drive, | |Joshua.Zhao@ |

| | |San Jose, CA 95110 | | |

|Qifan Chen |Atheros |1700 Technology Drive, | |Qifan.chen@ |

| | |San Jose, CA 95110 | | |

|James Cho |Atheros |1700 Technology Drive, | |James.Cho@ |

| | |San Jose, CA 95110 | | |

|Allert Van Zelst |Qualcomm |Netherlands | |allert@ |

|Richard Van Nee |Qualcomm |Netherlands | |rvannee@ |

|Santosh Abraham |Qualcomm |San Diego, USA | |sabraham@ |

|Hemanth Sampath |Qualcomm |San Diego, USA | |hsampath@ |

|Sameer Vermani |Qualcomm | | |svverman@ |

|Rolf De Vegt |Qualcomm |Santa Clara, USA | |rolfv@ |

|VK Jones |Qualcomm |Santa Clara, USA | |vkjones@ |

|Simone Merlin |Qualcomm |San Diego, USA | |smerlin@smerlin@qualcomm.|

| | | | |com |

|Lin Yang |Qualcomm |San Diego, USA | |linyang@linyang@qualcomm.|

| | | | |com |

|Vinko Erceg |Broadcom | |858 521 5885 |verceg@ |

|Joseph Lauer |BroadcomApplied | | |jlauer@ |

| |Signal Technology | | | |

|Mathew Fischer |Broadcom | | |mfischer@ |

|Tushar Moorti |BroadcomApple | | |rtm@ |

|Peiman Amini |Broadcom | | |pamini@ |

|Joonsuk Kim |Broadcom | | |joonsuk@ |

|Ron Porat |Broadcom | | |rporat@ |

|Jun Zheng |Broadcom | | |junz@ |

|Yuichi Morioka |Sony | | |yuichi.morioka@jp. |

|Ted Booth |Sony | | |ted.booth@am. |

|Yasushi Takatori |NTT | | |takatori.yasushi@lab.ntt.co.jp |

|Yusuke Asai |NTT | | |asai.yusuke@lab.ntt.co.jp |

|Ichihiko Toyoda |NTT | | |toyoda.ichihiko@lab.ntt.co.jp |

|Chiu Ngo |Samsung Electronics |75 W. Plumeria Dr. |+1-408-544-5633 |chiu.ngo@ |

| | |San Jose, CA 95131 | | |

| | |USA | | |

|Youngsoo Kim |Samsung Electronics |Mt. 14-1 Nongseo-Ri, Giheung-Eup, |+82-31-280-9614 |kimyoungsoo@kimyoungsoo@sa|

| | |Yongin-Si, Gyeonggi-Do, Korea 449-712 | | |

|Chunhui (Allan) Zhu |Samsung Electronics |75 W. Plumeria Dr. |+1-408-544-5667 |c.zhu@c.zhu@ |

| | |San Jose, CA 95131 | | |

| | |USA | | |

|Osama Aboul-Magd |Samsung Electronics | |613-599-5078 |osama@osama@ |

|Daewon Lee |LG Electronics |LG R&D Complex 533, Hogye-1dong, |+82-31-450-7897 |daewon.lee@daewon.lee@ |

| | |Dongan-Gu, Anyang-Shi, Kyungki-Do, | | |

| | |431-749, Korea | | |

|Yujin Noh |LG Electronics |LG R&D Complex 533, Hogye-1dong, |+82-31-450-7897 |yujin.noh@ |

| | |Dongan-Gu, Anyang-Shi, Kyungki-Do, | | |

| | |431-749, Korea | | |

|Yongho Seoeok |LG Electronics |LG R&D Complex 533, Hogye-1dong, |+82-31-450-1947 |yongho.soeok@ |

| | |Dongan-Gu, Anyang-Shi, Kyungki-Do, | | |

| | |431-749, Korea | | |

|Bonghoe Kim |LG Electronics |LG R&D Complex 533, Hogye-1dong, |+82-31-450-4131 |bonghoe.kim@bonghoe.kim@lge.co|

| | |Dongan-Gu, Anyang-Shi, Kyungki-Do, | |m |

| | |431-749, Korea | | |

|Minho Cheong |ETRI |161 Gajeong-dong, Yuseong-gu, Daejeon, |+82 42 860 5635 |minho@etri.re.kr |

| | |Korea | | |

|Jaewoo Park |ETRI |161 Gajeong-dong, Yuseong-gu, Daejeon, |+82 42 860 5723 |parkjw@etri.re.krparkjw@etri.re.kr |

| | |Korea | | |

|Jae Seung Lee |ETRI |161 Gajeong-dong, Yuseong-gu, Daejeon, |+82 42 860 1326 |jasonlee@etri.re.krjasonlee@etri.re.k|

| | |Korea | |r |

|Jong-Ee Oh |ETRI |161 Gajeong-dong, Yuseong-gu, Daejeon, |+82 42 860 1758 |ohjongee@etri.re.krohjongee@etri.re.k|

| | |Korea | |r |

|Jeeyon Choi |ETRI |161 Gajeong-dong, Yuseong-gu, Daejeon, |+82 42 860 5247 |jychoi@etri.re.krjychoi@etri.re.krjyc|

| | |Korea | |hoi@etri.re.kr |

|Yun Joo Kim |ETRI |161 Gajeong-dong, Yuseong-gu, Daejeon, |+82 42 860 5480 |yunjoo@etri.re.kryunjoo@etri.re.kr |

| | |Korea | | |

|Sok-kyu Lee |ETRI |161 Gajeong-dong, Yuseong-gu, Daejeon, |+82 42 860 5919 |sk-lee@etri.re.krsk-lee@etri.re.kr |

| | |Korea | | |

|Il-Gu Lee |ETRI |161 Gajeong-dong, Yuseong-gu, Daejeon, |+82 42 860 1633 |iglee@etri.re.kriglee@etri.re.kr |

| | |Korea | | |

|James Wang |MediaTek, Inc. |2860 Junction Avenue |+1-408-526-1899 |james.wang@ |

| | |San Jose, CA 95134 | | |

| | |408-526-1899 x 88363 | | |

|Alvin Hsu |MediaTek, Inc |No. 1, Dusing Rd, 1, Hsinchu Science |+886-3-567-0766 |alvin.hsu@ |

| | |Park, Hsinchu, Taiwan 300, R.O.C. | | |

|Chao-Chun Wang |MediaTek | |+1-408-526-1899 |chaochun.wang @ |

|James Yee |MediaTek | |+886-3-567-0766 |james.yee@ |

|Jianhan Liu |MediaTek | |+1-408-526-1899 |jianhan.liu@ |

|Brian Hart |Cisco Systems |170 West Tasman Drive, San Jose, CA |408-526-3346 |brianh@brianh@ |

| | |95134 | | |

|Raghuram Rangarajan |Cisco Systems |170 West Tasman Drive, San Jose, CA |408-525-8143 |ragranga@ |

| | |95134 | | |

|Reza Hedayat |Cisco Systems |2200 East President George Bush |469-255-2656 |rehedaya@rehedaya@ |

| | |Highway, Richardson, TX 75082 | | |

|Andrew Myles |Cisco Systems |201 Pacific Highway, St Leonards, NSW, |+61-2-8446-1010 |amyles@ |

| | |Australia | | |

|Lisa Ward |Rohde Shwarz | | |Lisa.Ward@rsa.rohde-schwarz |

|Peter Loc |Ralink Technology |20833 Stevens Creek Blvd, Suite 200., | |peterloc@ |

| | |Cupertino CA 95014 | | |

|Thet Htun Khine |Radrix Co., Ltd | | |thet@ |

|Leonardo Lanante Jr. |Kyushu Institute of | | | |

| |Technology | | | |

|Yuhei Nagao |Kyushu Institute of | | | |

| |Technology | | | |

|Nir Shapira |Celeno |26 Zarhin st’ |+972-54-4449370 |nir.shapira@ |

| |Communications |Raanana, Israel | | |

|Yaron Shany |Celeno |26 Zarhin st’ | |Yaron.shany@ |

| |Communications |Raanana, Israel | | |

|Liwen Chu |STMicroelectronics |2525 Augustine Drive, Santa Clara, CA |+1.408.467.8436 |Liwen.Chu@ |

| | |95054 | | |

|George Vlantis |STMicroelectronics |2525 Augustine Drive, Santa Clara, CA |+1.408.451.8109 |George.Vlantis@ |

| | |95054 | | |

|Zhendong Luo |China Academy of |No.52 Hua Yuan Bei Rd., Beijing, China |+86 10 62300171 |luozhendong@ |

| |Telecommunication | | | |

| |Research (CATR) | | | |

|Siyang Liu |CATR | |+86 10 62300175 |liusiyang@ |

|Daning Gong |CATR | |+86 10 62300156 |gongdaning@ |

|Chaoyuan Lv |China Mobile | |+86 13581868259 |lvchaoyuan@ |

|Xuetian Zhu |China Telecom | |+86 10 58552163 |zhuxuetian@ |

|Jingyu Wang |China Unicom | |+86 10 66259623 |wangjy@ |

|Bo Sun |ZTE Corporation | |+86 29 88724130 |Sun.bo1@.cn |

|Kaiying Lv |ZTE Corporation | |+86 29 88724130 |lv.kaiying@.cn |

|Edward Au |Huawei Technologies | |+1 (773) 782 6875 |edwardau@ |

|Lin Wang |Datang Mobile | |+86 10 58832000 |wanglin6@ |

|Yunzhou Li |Tsinghua University | |+86 10 62773363 |liyunzhou@tsinghua. |

|Guixia Kang |Beijing University | |+86 13911060877 |gxkang@bupt. |

| |of Posts and | | | |

| |Telecommunications | | | |

| |(BUPT) | | | |

|Gang Xie |BUPT | |+86 10 62283222 |xiegang@bupt. |

|Zhanji Wu |BUPT | |+86 10 62281058 |wuzhanji@bupt. |

|Sean Coffey |

|Total number of |Cyclic shift for transmit antenna iTX (in units of ns) |

|transmit antennas | |

|(NTX) | |

| |1 |2 |3 |

|VHT-SIG-A1 |

|0-1 |BW |2 |Set to 0 for 20 MHz, 1 for 40 MHz, 2 for 80 MHz, 3 for 160 MHz and 80+80 MHz mode |

|2 |Reserved |1 |Reserved for possible expansion of BW field. Set to 1. |

|3 |STBC |1 |Set to 1 if all streams use STBC, otherwise set to 0. When STBC bit is 1, an odd |

| | | |number of space time streams per user is not allowed. |

|4-9 |Group ID |6 |A value of all ones indicates [10/0382r2]: |

| |[10/0582r1] | |A single user transmission |

| | | |A transmission where the group membership has not yet been established |

| | | |A transmission that needs to bypass a group (e.g. broadcast) |

|10-21 |NSTS [10/0582r1] |12 |For MU: 3 bits/user with maximum of 4 users |

| | | |Set to 0 for 0 space time streams |

| | | |Set to 1 for 1 space time stream |

| | | |Set to 2 for 2 space time streams |

| | | |Set to 3 for 3 space time streams |

| | | |Set to 4 for 4 space time streams |

| | | |Otherwise: first 3 bits contain stream allocation, set to 0 for 1 space time stream, |

| | | |set to 1 for 2 space time streams, etcetera up to 8 streams. Remaining 9 bits contain |

| | | |partial AID: being the 9 LSB bits of AID. For Broadcast and multicast, these 9 bits |

| | | |are set to 0. For STA-to-AP, these 9 bits are set to a special value (TBD). |

|22-23 |Reserved |2 |All ones |

| |Total |24 | |

|VHT-SIG-A2 |

|0-1 |Short GI |2 |Set B0 to 0 for Long GI, set to 1 for Short GI |

| | | |Set B1 to 1 when Short GI and Nsym%10 == 9 |

|2-3 |Coding |2 |For SU: |

| | | |Set B2 to 0 for BCC, set to 1 for LDPC |

| | | |For MU: [10/1277r0] |

| | | |Set B2 to 0 for BCC, set to 1 for LDPC for 1st user |

| | | |If user 1 has 0 Nsts value, then B2 is reserved and set to 1 |

| | | |B3 purpose is under discussionis defined as Nldpc-ext (see 3.2.4.2.2) |

|4-7 |MCS |4 |For SU/Broadcast/Multicast: MCS index |

| | | |For MU: Reserved, set to all ones [10/1277r0] |

| | | |B4: Set to 0 for BCC, 1 for LDPC for the 2nd user |

| | | |B5: Set to 0 for BCC, 1 for LDPC for the 3rd user |

| | | |B6: Set to 0 for BCC, 1 for LDPC for the 4th user |

| | | |If user 2, 3, or 4 has 0 Nsts value, then corresponding bit is reserved and set to 1 |

| | | |B7: Reserved and set to 1 |

|8 |SU-Beamformed |1 |Set to 1 when packet is a SU-beamformed packet |

| | | |Set to 0 otherwise |

| | | |For MU: Reserved, set to 1 |

|9 |Reserved |1 |All ones |

|10-17 |CRC |8 |CRC calculated as in 11n Section 20.3.9.4.4 with C7 in B10 |

|18-23 |Tail |6 |All zeros |

| |Total |24 | |

Note that the fields are transmitted in the order shown in and LSB first.

[10/1052r0]

A Smoothing bit shall not be included in either VHT-SIG-A or VHT-SIG-B. [10/0382r2]

3.2.3.2.3 VHT-STF definition

The 20 MHz L-STF pattern in the VHT preamble is as defined in 20.3.9.3.3 of Std 802.11n-2009. [10/843r0]

The frequency domain sequence used to construct the VHT-STF in 20 MHz transmission is identical to the L-STF; in 40 MHz transmission, the VHT-STF is constructed from the 20 MHz version by duplicating, frequency shifting, and rotating the upper sub-carriers by 90°; in 80 MHz transmission, the VHT-STF is constructed from the 20 MHz version by replicating it in each 20 MHz band, frequency shifting, and applying appropriate phase rotations for each 20MHz sub-band. [10/843r0]

For a 160 MHz transmission, subcarriers in the VHT-STF symbol with indices -250 to -6 shall use the VHT-STF pattern for the 80 MHz VHT-STF, with the VHT-STF pattern for subcarrier index -122 mapping to subcarrier index -250 in the 160 MHz transmission. Furthermore, subcarriers in the VHT-STF symbol in the 160 MHz transmission with indices 6 to 250 shall also use the the VHT-STF pattern for the 80 MHz VHT-STF, with the VHT-STF pattern for subcarrier index -122 mapping to subcarrier index 6 in the 160 MHz transmission. All other subcarriers shall not be modulated. [10/843r0]

For non-contiguous transmissions using two 80 MHz frequency segments, each 80 MHz frequency segment shall use the VHT-STF pattern for the 80 MHz VHT-STF. [10/843r0]

VHT-STF sequence for 160 MHz VHT transmissions shall be constructed by repeating the VHT-STF sequence for 80 MHz VHT transmissions twice in frequency as follows

[pic]

where VHTSTF-122,122 is the VHT-STF sequence for 80 MHz VHT transmissions. The following phase rotation per 20 MHz subchannel shall be applied starting from the lowest 20 MHz subchannel in frequency: [c80 c80], where c80 is the phase rotation per 20 MHz subchannel for 80 MHz transmissions. [10/774r0]

3.2.3.2.4 VHT-LTF definition

The long training fields consists of one, two, four, six or eight VHT long training fields (VHT-LTFs) that are necessary for demodulation of the VHT-Data portion of the PPDU or for channel estimation during an NDP packet. [10/0566r2]

The VHT-LTF mapping matrix P for one, two or four VHT-LTFs shall be the same as defined in 802.11n standard specification (Section 20.3.9.4.6, Eq. (20-27)). [10/0566r2]

The VHT-LTF mapping matrix P for six VHT-LTFs is defined as follows:

[pic]

[10/0771r0]

The VHT-LTF mapping matrix P for eight VHT-LTFs is defined as follows:

[pic]

where P4x4 is defined by Equation 20-27 in Std 802.11n-2009. [10/0566r2]

The VHT-LTF symbols shall have the same number of pilot subcarriers as the data symbols. The pilot subcarrier indices of the VHT-LTF symbols shall be identical to the pilot subcarrier indices of the data symbols. The pilot values on these subcarrier indices during VHT-LTFs shall be given by the elements at the corresponding indices of the VHT-LTF sequence.

The VHT-LTF mapping matrix P shall be applied to all subcarriers in the VHT-LTF symbols except for the pilot subcarriers. Instead, a row-repetition matrix R shall be applied to all pilot subcarriers in the VHT-LTF symbols. The row-repetition matrix R has the same dimensions as the matrix P (NSTS x NLTF), with all rows of the matrix R being identical to the first row of the matrix P of the corresponding dimension. This results in all space-time streams of the pilot subcarriers in VHT-LTF symbols having the same pilot values.

For each pilot subcarrier, the same per-stream CSD and spatial mapping shall be applied across VHT-LTF and data symbols. [10/0771r0]

In a 80 MHz transmission, the VHT-LTF sequence to be transmitted (on subcarriers -122 to 122) shall be:

[pic]

The VHT-LTF sequence for 160 MHz VHT transmissions shall be constructed by repeating the VHT-LTF sequence for 80 MHz VHT transmissions twice in frequency as follows

[pic]

where VHTLTF-122,122 is the VHT-LTF sequence for 80 MHz VHT transmissions. The following phase rotation per 20 MHz subchannel shall be applied starting from the lowest 20 MHz subchannel in frequency: [c80 c80], where c80 is the phase rotation per 20 MHz subchannel for 80 MHz transmissions. [10/0774r0]

3.2.3.2.5 VHT-SIG-B definition

VHT-SIG-B shall be BPSK modulated.

VHT-SIG-B shall use long GI.

VHT-SIG-B shall consist of 26 bits for a 20 MHz PPDU, 27 bits for a 40 MHz transmission and 29 bits for a 80 MHz transmission. For the 40 MHz and 80 MHz PPDU, the VHT-SIG-B bits are repeated as shown in Figure 5Figure 3.

[pic]

Figure 54 - VHT-SIG-B in 20, 40 and 80 MHz transmissions

In a 160 MHz PPDU, the 80 MHz VHT-SIG-B is repeated twice in frequency.

R3.2.1.I: VHT-SIG-B includes the fields listed in Table 2

Table 22 - VHT-SIG-B fields

|Field |MU bit allocation |SU bit allocation |Description |

| |20 MHz |40 MHz |80 MHz |20 MHz |40 MHz |80 MHz | |

|Length |16 |17 |19 |17 |19 |21 |length of useful data in PSDU|

| | | | | | | |in units of 4 octets |

|MCS |4 |4 |4 |- |- |- | |

|Reserved |0 |0 |0 |3 |2 |2 |All ones |

|Tail |6 |6 |6 |6 |6 |6 |All zeros |

|Total # bits |26 |27 |29 |26 |27 |29 | |

NOTE –varying the Length field size with channel width and SU/MU ensures that a consistant packet duration of approximately 5.4ms (the max packet duration from L-SIG) is maintained.

Order of transmission: Length, MCS (in case of MU) / Reserved (in case of SU), Tail. Fields are transmitted LSB first. [10/1052r0]

The number of octets implied by VHT-SIG-B length shall not be more than 3 octets longer than the number of octets implied by L-SIG LENGTH and VHT MCS.

For VHT NDP, fixed bit patterns are defined for VHT-SIG-B in the 20, 21, and 23 useful VHT-SIG-B bits for 20, 40, and 80 MHz, respectively. These bit patterns are shown to have the lowest Peak-to-Average Power Ratio (PAPR) when using a four times oversampled IFFT.

The following sequences (showed LSB first) shall be used for VHT-SIG-B in VHT NDPs:

20 MHz: 0 0 0 0 0 1 1 1 0 1 0 0 0 1 0 0 0 0 1 0 (PAPR = 3.16 dB)

40 MHz: 1 0 1 0 0 1 0 1 1 0 1 0 0 0 1 0 0 0 0 1 1 (PAPR = 5.42 dB)

80 MHz: 0 1 0 1 0 0 1 1 0 0 1 0 1 1 1 1 1 1 1 0 0 1 0 (PAPR = 5.13 dB)

[10/1290r0]

3.2.4 VHT Data field

The number of OFDM symbols in the Data field shall be computed using the length field in L-SIG.

For both BCC and LDPC, all bits (including MAC and PHY pad bits) shall be encoded.

When BCC encoding is used, the Data field shall consist of the 16-bit SERVICE field, the PSDU, the PHY pad bits and the tail bits (6NES bits), in that order as shown in Figure 4. When LDPC encoding is used, the Data field shall consist of the 16-bit SERVICE field, the PSDU and the PHY pad bits. No tails bits are included when LDPC encoding is used.

[pic]

Figure 65--Data field encoding with BCC

For BCC encoding, the interleaver parameters for 20 MHz and 40 MHz 802.11ac packets will remain unchanged from 20 MHz and 40MHz 802.11n, i.e. the NCOL and NROT parameters for 20/40MHz are as in Table 20-16 from 802.11n-2009. [10/548r2]

For a SU transmission using BCC encoding, the padding flow is as follows. The MAC calculates the NSYM and NPAD using the following equations:

[pic]

The MAC then pads to the last byte boundary and indicates (using the TXVECTOR) the number of PHY pad bits to the added. After receiveing the PSDU, the PHY adds the 0-7 padding bits and then NES tail bits at each encoder. [10/820r0]

For an MU transmission using BCC encoding, the padding flow is as follows. The MAC calculates NSYM for each user separately using the following equations:

[pic]

[pic]

[pic]

For each user, based on the maximum number of symbols over all users, the MAC pads to the last byte boundary. The number of PHY padding bits added for each user is calculated as in the SU case. For each user, the encoding and stream parsing is done as in the SU case. [10/820r0]

3.2.4.1 SERVICE field

The SERVICE field is as shown in Table 3.

Table 33 - SERVICE field

|Bits |Field |Description |

|B0-B6 |Scrambler Initialization | |

|B7 |Reserved | |

|B8-B15 |CRC |CRC calculated over VHT-SIG-B (excluding tail) |

NOTE—the Reserved and CRC fields are scrambled.

The CRC calculation and insertion is illustrated in Figure 7Figure 5.

[pic]

Figure 76--VHT-SIG-B and SERVICE field relationship

The CRC is calculated over the VHT-SIG-B bits, excluding the tail bits using the CRC defined in 802.11n-2009 section 20.3.9.4.4. C7 of the CRC is mapped to B8 of the SERVICE field, C6 to B7, …, C0 to B15.

The resulting SERVICE field and PSDU shall be scrambled, as in 11n.

3.2.4.2 Coding

3.2.4.2.1 BCC coding

The draft specification shall support the following:

• The maximum data rate per BCC encoder is 600Mbps

• The number of BCC encoders for a particular combination of MCS, Nsts and BW is determined by the short GI data rate and the same number of encoders are used for the corresponding normal GI rate

• The number of BCC encoders is not limited

3.2.4.2.2 LDPC coding

The draft specification shall include the same LDPC PPDU encoding process from 802.11n (described in Section 20.3.11.6.5) for 11ac, regarding codeword length, shortening, puncturing and repetition. [10/1300r0]

The procedure for encoding and decoding the payload for an SU packet is as follows.

Number of initial payload OFDM symbols:

[pic]

Number of final payload OFDM symbols:

[pic]

[pic] flag is hosted in VHT-SIGA2.B3

At the receive side, the number of payload OFDM symbols:

[pic]

Nsym_init and Npld:

[pic]

The procedure for encoding and decoding a MU packet is as follows:

For each user in the MU packet, compute the initial number of OFDM symbols [pic]:

[pic]

Finds the initial estimate of the longest symbol length:

[pic]

For each LDPC users, go through LDPC PPDU math to find if extra OFDM symbol (or symbols) are needed:

If at least one of the LDPC users require extra OFDM symbol (or symbols), set [pic](VHT-SIGA2.B3 = 1).

Otherwise, set [pic] (VHT-SIGA2.B3 = 0).

L-SIG length is set based on the actual length of the packet:

[pic]

For each user, construct PSDU by:

• For LDPC users, add sufficient MAC padding to fill up [pic]symbols

For BCC users, add sufficient MAC padding to fill up [pic]symbols

For each LDPC user in the MU packet, encode the PSDU using LDPC PPDU process

• If[pic], LDPC PPDU encoding process adds [pic] symbols

• If [pic], LDPC PPDU encoding does not add extra symbols

For each BCC user, encode the PSDU using BCC encoder. Note that the tail bits are placed at the very end of the packet.

[10/1300r0]

3.2.4.3 Data interleaver

3.2.4.3.1 Stream parser

For BCC encoding, stream parsing done in the same way as 11n, i.e.,

- Consecutive blocks of  s(iss) bits are assigned to different spatial streams in a round robin fashion.

- If multiple encoders are present per user, the output of each encoder is used in a round robin cycle, i.e.,

o At the beginning S bits from the output of first encoder are fed into all spatial streams,

o Then S bits from the output of the next encoder are used and so on. S is a sum of s(iss) over all streams)

In case of contiguous and noncontiguous 160 MHz transmissions, even output bits of the stream parser are allocated to the lower 80 MHz and odd output bits to the upper 80 MHz for each stream. First output bit from the stream parser in each symbol is an even bit.

For 160MHz, if each BCC encoder does not generate integer blocks of S coded bits in each OFDM symbol, then apply the same stream parsing method until the last integer block (floor(NCBPS/NES/S)) of S bits at each encoder.

Assuming that at this point in each OFDM symbol each BCC has M.s (M ................
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