In this article what is Wi-Fi 7 as per my understanding and what all the features coming with the Standard, how to identify the devices supports Wi-Fi 7 or not, basic description about the features in Wi-Fi 7.
IEEE 802.11 be standard also known as Extremely high throughput (EHT). If the device supports Wi-Fi 7, we will see the EHT information element. For example, access point broadcasting Wi-Fi 7 SSID we will see EHT information element in Beacon as shown below
Similar information element will be seen in Association Request if client devices support Wi-Fi 7 as shown below
WI-FI 7 main features
1) Multi-Link Operation (MLO) one of the features everyone is talking about, and not all the Wi-Fi 7 User devices support as I see the feature is not mandatory. MLO has multiple flavors like EMLSR, (Enhanced Multi-link Single Radio), STR (Simultaneous Transmit & Receive, Non-STR(NSTR), MLMR (Multi-link Multi Radio) etc.
All the Wi-Fi-7 certified access points will definitely support MLO and most client support either Support MLO with EMLSR or STR.
Below is the Association request from a Mobile device supporting MLO
Note: Please refer to MLO article for detailed information Multi-Link Operation (MLO) which will be uploaded soon.
MLO helps reduces the latency. For example, one common scenario we have seen without MLO, when client connected to Access point on 5GHz suddenly disconnects (due to radar signal detection or any other interference etc.) and reconnects to the same Access point on 2.4GHz., In this scenario, client has to reauthenticate with the access point which led to drop wireless frames.
But if Using MLO, above can be avoided that is Client will maintain two wireless links (Active -Standby in EMSLR and Active -Active in STR), if one link goes off, wireless frames will be forwarded using another link.
Throughput and Bandwidth will be high and almost double if the user device has Multiple links to access point using 5 GHz & 6 GHz.
2) Preamble Puncturing is mandatory in Wi-Fi 7.
Let's assume We have four lane (Like 1,2,3 & 4) road, second lane is the damaged.
Without Preamble Puncturing, lanes 2,3, & 4 are blocked, and no traffic is allowed on lanes 2, 3, & 4 except lane 1 where traffic is allowed.
With Preamble Puncturing, only Lane 2 is blocked and only traffic is blocked on lane 2. Traffic is allowed on lanes 1, 3 & 4.
In OFDM if we are using 80 MHz bonded channel (like 36(primary),40,44 & 48) and if there is any disturbance (noise / interference) on only channel 40, wireless frames are exchanged only on primary channel which channel 36. So, your 80Mhz channel is working at 20Mhz.
with Same scenario as above, In OFDMA with the help of preamble puncturing, AP will negotiate the user device by sending preamble only on channels 36.44 & 48 (that is 60MHz) by puncturing affected channel and its associated resource units capacity.
Preamble puncturing was introduced in Wi-Fi 6 but not mandatory. Preamble puncturing supported in 80Mhz, 160MHz and 320MHz not in 20 or 40 MHz .
You can see Preamble Puncturing in the beacon under EHT operations information element. If Disabled Subchannel Bitmap Present is True, then Preamble puncturing is happening
3) 320 MHz Bandwidth is supported in 6Hz (optional). You will see major advantage in countries adopted full spectrum of 6GHz that is 1200 MHz as you will have 6 * 320 MHz overlapping channels or 3 non-overlapping channels.
One of the Major use cases I have seen to use 6GHz is for Mesh backhaul as it helps backhaul has equal or more bandwidth to facilitate 5GHz users.
We cannot use 320 MHz in 5GHz as we have only limited channels. For example, in Singapore, we have 25 Individual channels (that is each channel is 20 MHz).
320 MHz = 16 * 20 MHz and left only 8 individual channels leads 8 * 20 = 160 MHz only.
4) Large Multi-RUs (Multiple Resource Unit) & Smaller Multi-RU. In Wi-Fi 6 Single resource unit was allocated to user but in Wi-Fi 7 Multiple resource units are combined and are allocated to Single user which will increase throughput and overall performance for the user.
As we learned Preamble Puncturing is mandatory in Wi-Fi 7 it helps to have Large Multi Resource unit support.
For example: If Access point broadcasting SSID at 80MHz (36+40+44+48) and found the 20MHz (Channel 40) is noisy and Preamble Puncturing helps AP to negotiate with user for 60MHz that is allocation Large Resource unit allocation 242-tone (20MHz) + 484-tone (40 MHz) as here 20 MHz channel is punctured
MRU Options 242-tone+ 484-tone with 20 MHz Channel Punctured in 80MHz, 484-tone + 996-tone where 40 MHz Channel Punctured in 160 MHz etc.
Smaller Multi-RU or Smaller Multiple Resource unit- is the allocation of Multiple Resource units 26-tone + 52-tone or 26-tone + 106-tone. In Wi-Fi 6 User is allocated Single Resource unit and User has litter more data (101 Mbps) which cannot be accommodated for example 52-tone (assumption can accommodate only 100 Mbps) then user has to use 102-tone which is huge jump in usage Resource unit.
In Wi-Fi 7 we can go with Multiple resource unit combination for the user 26-tone+ 52-tone for same 101 Mbps data. This helps optimization of usage of Resource units and helps multiple users to have optimized access of wireless.
5) 4096 QAM - Wi-Fi 4 Supports 64 QAM (MCS 6, 7), Wi-Fi 5 supports 256 QAM (MCS 8, 9), Wi-Fi 6 Supports 1024 QAM (MCS 10, 11). Wi-Fi 7 Supports 4096 QAM (MCS 12, 13).
MCS 12 or 13 which will allow to use 4096 QAM is supported only in 5GHz / 6GHz.
Modulation and Coding Scheme (MCS) 12 & 13 which will give maximum throughput. For user device to work on MCS 12 or 13 must have very good SNR.
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