Wifi-7 (802.11be) was ratified last year and we have now started seeing vendors shipping APs based on these new standards. In this post lets discuss what is new with Wifi-7 and compare it to how it its an improvement over Wifi-6e.

With Wifi-7 we see these new advanced features:

• 320 Mhz channel width: With Wifi-7 the new 6Ghz band can now support channel widths between 20Mhz and 320Mhz.
  
  
• 4096 QAM Modulation: The new 4K QAM allows for a theoretical 20% increase of transmission rates over Wifi-6 1024 QAM modulation.
  
  
• Multi-Link Operation (MLO): MLO allows devices to both transmit and receive data at the same time using multiple links to increase throughput and reliability.
  
  
• Multiple RUs to a single Station: Allows for multiple RUs created using OFDMA to be used for a single station, providing flexible resource scheduling.

So lets step through each of these features and compare them with the Wifi-6 standard.

Increased channel width

With Wifi-7 we now have a new channel width on the 6Ghz spectrum, 320Mhz! For those who need a quick refresher; each of the wireless spectrums (2.4Ghz, 5Ghz, and 6Ghz) is split up into 20Mhz width smaller channels. We assigned access points to different channels to breakup the RF space so that clients talking to one AP don’t interfere with clients talking to another AP.

By increasing the channel width from 20Mhz we combine channels together, reducing the overall number of channels available for APs to use, but gain more bandwidth. The Wifi-6 standards defined the 6Ghz channel widths as 20, 40, 80, and 160Mhz. Wifi-7 now adds a 5th width of 320Mhz allowing for even greater bandwidth on the 6Ghz spectrum.

My guess to the reason why we don’t see this new width on the 5Ghz spectrum is that 320Mhz is almost the entire width of the spectrum. The 5Ghz spectrum is too small and there would only ever be a single channel for APs to fight over.

New QAM Modulation

With Wifi-7 we get a new modulation; 4096-QAM. A modulation is an encoding scheme that defines how we represent data. The most basic modulation is a simple sine wave, the high point representing a 1 and low point representing a 0. In this modulation there are 2 states. Using Quadrature Amplitude Modulation (QAM), we can create more than 2 states by varying the different amplitude and phase of the radio signal. With 4096-QAM there are 4096 possible states. And while our first example was only able to send 1 bit of data per state, with 4096 QAM we can represent 12 bits per state.

To compare Wifi-6 and Wifi-7; Wifi-6 had a maximum QAM modulation of 1028 states (1028-QAM); which allowed for each state to represent a maximum of 10 bits per state. So with 4096-QAM we see a 20% increase in the data transmission rate.

Multi-Link Operation (MLO)

In the past iterations of the Wifi standards each client was only able to connect to a single wireless radio spectrum (2.4Ghz, 5Ghz, or 6Ghz) at any one time. With Multi-link Operation (MLO) compatible clients will be able to connect to all 3 spectrums at the same time. The client and AP can use all available links to send and receive data at the same time.

There are two main modes with MLO; Simultaneous Transmit and Receive Operation (STR), and Non-simultaneous Transmit and Receive Operation (NSTR). As the names describe STR allows for asynchronous transmission and receiving of data on each link, so while data is sending on the 5Ghz, data can be received on the 2.4 or 6Ghz links. With NSTR, all links can either send or receive at a time, they are synchronous. NSTR performs in a half-duplex nature but allows for higher throughput as data is transmitted across all links, while STR is more full-duplex allowing for a reduction in delay as both the AP and client can send and receive at the same time.

MLO is new to Wifi-7 and does not exist on any of the previous standards.

OFDMA optimizations

The last two points both have to do with Orthogonal Frequency-Division Multiple Access (OFDMA) optimizations. With Wifi-6 we got OFDMA, which further separates each of the RF channels into smaller Resource Units (RU), also called subcarriers. These RUs are about 2Mhz wide and are comprise of the following:

• Data subcarriers used to carry data information and form the majority of the subcarrier’s assignment
  
  
• Pilot subcarriers used for phase tracking for channel estimation
  
  
• DC subcarriers at the center frequency of the channel
  
  
• Guard band/Null subcarriers used at the band edges to protect from interference from neighboring RUs

Wifi-6 APs with multiple clients can assign difference clients to different RUs allowing for simultaneous transmission of data for each client. The Wifi-6 standard only allows a single client to get assigned to a single RU. With Multiple RUs (MRU) Wifi-7 now allows for a single client to receive multiple RU subcarriers to use for upload and download transmission. The Access Point can now assign unused RUs to clients for increased bandwidth and allows the client to choose clearer subchannels and theoretically reduces latency by up to 25% from the standard single RU of OFDMA defined in Wifi-6.

Wifi-7 takes the work done with Wifi-6 and continues to optimize on it. With a new wider channel width, 4096-QAM, MLO, and Multiple RUs its no wonder that Wifi-7 is known as the Extremely High Throughput (EHT) standard.

With any new Wifi standard your experience varies depending on which of the new features both the AP and client are capable and which features are enabled in the configuration. Because of this, Wifi-7 APs are backwards compatible with older standards, allowing you to future proof your wireless infrastructure without needing to replace all your clients.

If you are interested in Wifi7 please contact us at Sales@lookingpoint.com and we will reach out to you with further information.