802.11ac vs 802.11n : Differences and Comparison
♠ Demo Video:
♠ Here we will split the discussion in three sections.
♦ a. Differences between 11n and 11ac.
♦ b. Removed feature in 11ac from 11n.
♦ c. Same features in 11n and 11ac.
♦ a. Differences between 11n and 11ac:
| Number | 802.11n | 802.11ac |
| 1. | Channel width: 20 and 40MHz | Channel width: 20,40,80 and160 or 80+80 MHz |
| 2. | MCS0 to MCS76 | Introduced MCS8 and MCS9 |
| 3. | Supports till 64QAM. | Supports till 256QAM (MCS8,9). |
| 4. | Max A-MSDU size is 7935bytes. | Max A-MSDU size is 11KB (11426bytes). |
| 5. | Max A-MPDU size is 65535bytes. | Max A-MPDU size is (1048576bytes) 1MB. |
| 6. | Max MPDU size is 7935bytes. | Max MPDU size is 11454bytes. |
| 7. | No concept of Multi user MIMO. | Supports Down link MU-MIMO. |
| 8. | Data packet can be sent without A-MPDU. Like Data+Normal ACK. | Even single frame has to be sent as A-MPDU. |
| 9. | No GCMP security support. | New optional encryptions method “Galois Counter Mode Protocol” is added. |
| 10. | No dynamic bandwidth signaling mechanism in 11n. | Dynamic bandwidth signaling is there in 11ac. |
| 11. | 11n offers data rate for each MCS value. | 11ac does not offer data rate for some MCS index like no data rate is mentioned for MCS9 HT20 SGI/LGI. |
| 12. | Can operate in 2.4GHz band. | Only operates in 5GHz band. |
| 13. | Supports upto 4 spatial streams. | Supports upto 8 spatial streams. |
| 14. | Maximum data rate is 600Mbps [As 4×4: point 13.] | Maximum data rate is 6933.3Mbps [As 8×8: point 13.] |
| 15. | MPDU pad bits are appended to each MPDU within A-MPDU. See below structure of A-MPDU. [MPDU delimiter][MPDU1][Pad] [MPDU delimiter][MPDU2][Pad] | MPDU pad bits are appended to last of A-MPDU sub frame. See below structure of A-MPDU. [MPDU delimiter][MPDU1][MPDU delimiter][MPDU2][Pad] |
| 16. | New powersave introduced a. PSMP b. SMPS | New powersave introduced a. VHT TXOP |
| 17. | Supports implicit beamforming. | Does not support implicit beamforming. |
| 18. | 11n has backward compatibility to support DSSS/CCK. | As 11ac works in 5GHz only so no need to support DSSS/CCK. |
♦ Interesting Note regarding point 4 and 6:
| Point 6 is 2 bits field in VHT | Relation with HT |
| Set to 0 for 3895 octets | Maximum A-MSDU Length in HT Capabilities set to 3839 |
| Set to 1 for 7991 octets | Maximum A-MSDU Length in HT Capabilities set to 7935 |
| Set to 2 for 11 454 octets | Maximum A-MSDU Length in HT Capabilities set to 7935 |
| Value 3 is reserved. | NA |
♦ b. Removed feature in 11ac from 11n:
| Number | 802.11n | 802.11ac |
| 1. | Pure 802.11n device may use RIFS (Reduced Inter Frame Space) feature. | RIFS is removed. |
| 2. | Support two types of beamforming: explicit or implicit. | Implicit was removed. |
| 3. | 11n support green field for pure 11n mode. | Supports “Legacy VHT preamble”. There is nothing called “pure 11ac mode”. |
| 4. | Supports Green Field mode. | Does not support Green Field mode. |
♦ c. Same features in 11n and 11ac:
| Number | 802.11n | 802.11ac |
| 1. | A-MPDU, A-MSDU and A-MSDU inside A-MPDU aggregation. | All three aggregations are there but use of A-MSDU inside A-MPDU is seen widely here. |
| 2. | Block Acknowledgement. | No change in BA. |
| 3. | Can work in 5GHz band. | Only works in 5GHz band. |
| 4. | Support explicit and implicit beamforming. | Only supports NDP (Null Data Packet) explicit beamforming. |
| 5. | Short guard Interval and Long guard interval. | Support same SGI(400ns) and LGI(800ns) |
| 6. | Max MSDU size 2304bytes. | MSDU size is always same. |
| 7. | Supports Orthogonal Frequency Division Modulation technique. | Uses same OFDM. |
♠ These are the points we found for 11ac vs 11n. If you have any more points please let us know in comment section.
♥♥If you have any doubts or query please let me know in comment section or send mail at feedback@wifisharks.com.♥♥
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Sandy
Hi Bamdeb ,
Thanks for the reply
Sandy
Hi Bamdeb ,
Is there any chance to send A-MSDU and A-MPDU both at the same in any transmission ?
Bamdeb
Hi Sandy,
If i understand your correctly. Here is one answer.
Its possible to send A-MSDU inside an A-MPDU. If you have 11ac throughput capture you may see this .Check any data packet from that throughput capture. This is actually A-MPDU.
But it’s is not mandatory to send A-MSDU inside A-MPDU in 11ac.
If i understand your correctly in another way. Here is the 2nd answer.
It’s not possible to use A-MPDU and A-MSUD mechanism both at same time between two wireless devices in one transmission. They have to agree any one method or no aggregation .