1. 11ac 80MHz Transmission Flow
Month Year
Month Year
doc.: IEEE yy/xxxxr0
doc.: IEEE yy/xxxxr0
11ac 80MHz Transmission Flow
Date:
Authors:
Slide 1
Sudhir Srinivasa et al.
Page 1
John Doe, Some Company
John Doe, Some Company

2. Introduction Core features of 11ac Basic PHY
Month Year
doc.: IEEE yy/xxxxr0
Introduction
Core features of 11ac Basic PHY
Higher bandwidth (at least 80MHz)
Higher order constellations (256QAM)
Possible data and pilot tone mappings for both 80MHz and higher bandwidths have been discussed in [1, 2].
This presentation will discuss the 80MHz MIMO-OFDM transmission flow in Data field for BCC encoding, including:
Padding
Multiple encoders
Encoder and stream parsing
Interleaver design
Sudhir Srinivasa et al.
John Doe, Some Company

3. Preliminaries
We assume that PPDU duration is signaled in number of symbols in the SIG field [3].
MAC/PHY Padding is required to ensure that the coded bits fit inside an integer number of OFDM symbols
Some details about MAC and PHY padding has been presented in previous meetings [3]
The following slides describe the 80MHz MIMO-OFDM transmitter flow in detail.
Sudhir Srinivasa et al.

4. Transmitter Block Diagram for 11ac
PHY padding
Sudhir Srinivasa et al.

5. Propose maximum rate per BCC encoder to be 600 Mbps.
Reasons for 600Mbps/BCC
300 Mbps was a limitation 5 years ago, state-of-the-art CMOS technology allows higher rate per decoder.
It is an easy extension by doubling the clock of 300Mbps 11n BCC decoder, which is the reason 600Mbps was derived.
Sudhir Srinivasa et al.

6. Padding
Padding bits are added to ensure that the coded bits fit inside an integer number of OFDM symbols. This is done as follows (details refer to [3]) :
MAC adds required 4-byte null sub-frames and 0-3 bytes of final MAC pad to fill the frame to the last byte
PHY adds the remaining 0-7 padding bits to the end of the OFDM symbol.
PHY padding before encoder parser.
(Service bits + MAC payload + MAC/PHY padding bits) are passed to the scrambler.
Add 0-7
PHY padding bits
Encoder
Parser
Add Tail, Encoding &
Puncturing
Stream
AMPDU
(with MAC pad)
Scrambler
Sudhir Srinivasa et al.

7. Encoder Parser
With multiple encoders, scrambled data bits are distributed evenly among all the encoders, exactly like the encoder parser in 11n
Every consecutive block of NES bits divided among the NES encoders in a round robin fashion, i.e., one bit assigned per encoder in one cycle (identical to 11n).
The overall number of bits after padding should be divided to equal number of bits allocated to each encoder.
6 tail bits are added at each BCC encoder
Note that padding bits are scrambled, but the tail bits are not.
Encoded bits are punctured based on the coding rate
Add 0-7
PHY padding bits
Encoder
Parser
Add Tail, Encoding &
Puncturing
Stream
AMPDU
(with MAC pad)
Scrambler
Sudhir Srinivasa et al.

8. Stream Parser
The same stream parsing as 11n: Consecutive blocks of  s (num of bits on each constellation axis) bits are assigned to different spatial streams in a round robin fashion. If multiple encoders per user are present, the output of each encoder is used alternately in a round robin cycle, i.e., at the beginning S=NSSs bits from the output of first encoder are fed into all spatial streams, and then S bits from the output of the next encoder are used and so on.
Add Tail, Encoding &
Puncturing
Encoder
Parser
Stream
Parser
AMPDU
(with MAC pad)
Add 0-7
PHY padding bits
Scrambler
Sudhir Srinivasa et al.

9. Frequency Interleaver for 80MHz
Same interleaver structure as 11n, i.e. 3 permutations (characterized by three parameters NROW, NCOL and NROT)
NROW/NCOL Chosen as a good tradeoff for all constellations from BPSK through 256QAM
Simulations (backup slides) show that a good choice for these parameters in 80MHz (234 data tones [1]) is
NCOL = 26, NROW = 9 * NBPSCS, where NBPSCS is the number of coded bits per subcarrier per stream.
We also propose to define NROT as below:
When Nss <=4: NROT = floor(234/4)=58, so cyclic shift [0, 2 NROT*NBPSCS, NROT*NBPSCS, 3 NROT*NBPSCS]) for Nss=1,2,3,4 respectively.
When Nss >4: the stream cyclic rotation rule is TBD.
Sudhir Srinivasa et al.

10. Other Blocks Constellation Mapper as in 11n. STBC TBD.
Add 256QAM mapper.
STBC TBD.
Per-Stream CSD Values TBD.
IDFT Tone Allocation Refer to [1]:
5/6 Guard Tones, 3 DC tones, and 8 Pilot Tones
Overall 234 Data Tones
Sudhir Srinivasa et al.

11. Conclusions
80MHz MIMO-OFDM Tx Flow is given, with emphasis on: PHY padding, BCC encoder parser, interleaver.
Summarizing our proposed parameters:
0~7 bit PHY padding, and padding before encoder parser.
Up to 600Mbps per BCC encoder
Encoder Parser with 1 bit round-robin, equal number of bits per encoder.
Same stream parser as in 11n
Interleaver: NCOL=26; for Nss<=4, NROT= 58 and [ ]* NROT cyclic permutation is applied for each stream, as in 11n.
Tone Allocation see [1] (234 data, 3 DCs, 5/6 guards, 8 pilots).
TBD items:
Interleaver stream permutation for Nss>4
STBC
Per-Stream CSD values.
Sudhir Srinivasa et al.

12. References [1] 11-10-0370-00-00, 80MHz Tone Allocation
Month Year
doc.: IEEE yy/xxxxr0
References
[1] , 80MHz Tone Allocation
[2] , 160MHz PHY Transmission
[3] , VHT Frame Padding
Sudhir Srinivasa et al.
John Doe, Some Company

13. Simulation Results 1 Month Year doc.: IEEE 802.11-yy/xxxxr0
Sudhir Srinivasa et al.
John Doe, Some Company

14. Simulation Results 2 Month Year doc.: IEEE 802.11-yy/xxxxr0
Sudhir Srinivasa et al.
John Doe, Some Company

15. Simulation Results 3 Month Year doc.: IEEE 802.11-yy/xxxxr0
Sudhir Srinivasa et al.
John Doe, Some Company

16. Sudhir Srinivasa et al.

17. Sudhir Srinivasa et al.

18. Sudhir Srinivasa et al.

19. Sudhir Srinivasa et al.