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802.11ac vs 802.11n : Differences and Comparison


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Categories : 802.11ac , WLAN

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:

Number802.11n802.11ac
1.Channel width: 20 and 40MHzChannel width: 20,40,80 and160 or 80+80 MHz
2.MCS0 to MCS76Introduced 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. SMPSNew 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 VHTRelation with HT
Set to 0 for 3895 octetsMaximum A-MSDU Length in HT Capabilities set to 3839
Set to 1 for 7991 octetsMaximum A-MSDU Length in HT Capabilities set to 7935
Set to 2 for 11 454 octetsMaximum A-MSDU Length in HT Capabilities set to 7935
Value 3 is reserved.NA

b. Removed feature in 11ac from 11n:

Number802.11n802.11ac
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:

Number802.11n802.11ac
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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