What is Multi-RU Puncturing in WiFi 7?

As one of the highlights of WiFi 7, Multi-Resource Unit (RU) Puncturing is a significant improvement over the preamble puncturing introduced by WiFi 6. In this article, we will explain the fundamental parts of Multi-RU Puncturing, and why it’s important.

The value of Multi-RU Puncturing

Multi-RU Puncturing improves the usage of transmission channels by increasing throughput and reducing latency when multiple users are present. It enables the use of multiple resource units, while puncturing is available to avoid the congestion caused by interference and to maintain high transmission speeds.

We will break the explanation of Multi-RU Puncturing down into three parts: RU, Multi-RU, and puncturing, to reveal how MRU Puncturing is a great addition to WiFi 7.

What is an RU?

RUs (Resource Units) represent a group of small slices of wireless radio frequency, and each RU is constructed of several tones. Wider bandwidth contains more RUs and tones. RUs are designed to concurrently support multiple users in heavy traffic and to enable the free distribution of RUs as needed across different frequencies, to increase throughput and reduce latency.

▴  These are the different sizes of RU in each WiFi channel band; a single RU can have as few as 26 tones, and a maximum of 966.

With WiFi 6, the concept of an RU is used to construct a well-known feature: OFDMA (Orthogonal Frequency Division Multiple Access). If you visualize data transmission in the form of trucks on a highway, pre-OFDMA WiFi could only deliver one packet of user data in each truck at once. When it came to multi-user scenarios, latency would become a problem, and the truck would have to frequently shift gears to handle the load. But with OFDMA, data can be split into smaller resource units, truck storage can be fully used by different combinations of RUs, and storage can be efficiently distributed to multiple users.

▴  Data has been separated into smaller RUs; the containers can be fully used by different combinations of RU, and they can be efficiently distributed to multiple users.

What is Multi-RU (MRU)?

MRU can be thought of as an upgraded version of OFDMA. The main purpose of OFDMA is distributing bandwidth and making sure it’s shared efficiently when multiple users are connected. But according to the previous WiFi 6 protocol, a single user can only have one RU, potentially leaving the other RUs with nothing to do. MRU allows a single user to leverage multiple RUs depending on their needs. This enables more efficient use of bandwidth, and it increases the amount of data that an individual user can download and upload.

▴  User 1 can have both RU-106 + RU-52, and User 2 has RU-52.

And puncturing?

Puncturing can take 80 MHz and 160 MHZ WiFi channels and slice or bond them in increments of 20 MHz. To can help avoid the congestion caused by interference, and it can maintain transmission speeds in multi-user scenarios without dropping the signal.

▴  If a secondary WiFi channel experiences signal interference, and puncturing is not available, User #2 has to wait for the primary channel to become available. With puncturing present, unused portions of another channel can now be used.

WiFi protocols require that data transmissions be achieved through the continuous use of wireless channels, identified as primary and secondary channels. When a secondary channel conflicts with a radar system or is blocked by regional regulations, the entire bandwidth of the network can be restricted to the primary channel. And the primary channel cannot be punctured.

So, what is Muti-RU (puncturing)?

As we mentioned earlier, puncturing sidesteps channel interference and provides more functional channels to use. Meanwhile, MRU distributes these channels to more users and can provide higher transmission speeds to each of them. MRU Puncturing combines all of these capabilities.

▴  Only a few channels can be punctured based on the protocol.

As you can see, this 80 MHz channel has three 20 MHz subchannels available, and the remaining 60 MHz can be automatically split (or combined) according to the traffic needs detected by a WiFi 7 router. Transmission speeds are preserved, and User #1 can use two 20 MHz channels instead of being limited to one.

(Compare this to Multi-link operation (MLO), which is another major feature of WiFi 7. It efficiently reconstructs the combination of multi-user data channels to increase throughput, even within a single band.)

We hope these amazing features can inspire many of you to try the next-generation online experience and have fun with it; just make sure that all of your networking equipment is compatible with WiFi 7.

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[i] Compared to the previous WiFi 6 platform

[ii] Measured using WiFi 6 client connected at 200 Mbps to WiFi 6 router with RangeBoost Plus, compared to same WiFi 6 client connected at 200 Mbps to WiFi 5 router without RangeBoost Plus.

[iii] Subject to regulatory limitations, and co-existence with 5 GHz WiFi. Number of channels may be less than 7. If no 6 GHz SSID is displayed, please check whether your OS and client device are fully licensed to support the newly released 6 GHz band. You can check with your OS and client device provider for the WiFi 6E driver release schedule.