Wi-Fi 7 Multi-RU Vs Preamble Puncturing:Advantages & Differences

Introduction : Multi-RU puncturing and Preamble puncturing in Wi-Fi 7 sound similar because both involve “ignoring” bad parts of the spectrum, but they solve different problems at different layers. Let’s break it down clearly.

Wi-Fi 7 Multi-RU Puncturing

• OFDMA (Orthogonal Frequency Division Multiple Access) is added in Wi-Fi 6. A channel is divided into smaller chunks called RUs in OFDMA. Each RU (Resource Unit) can be assigned to a device, so multiple devices can transmit/receive in parallel on same channel. Example: 20 MHz channel can split into smaller RUs like 26-tone, 52-tone, 106-tone etc.
• Problem faced in WiFi 6/6E : Device can only use one RU at a time, even if there multiple smaller RUs available. Due to this, when interference occurs to some RUs, the AP can not efficiently assign the rest. This leads to wasted spectrum and lower throughput.
• Wi-Fi 7 introduces Multi-RU allocation with puncturing to fix this problem encountered in WiFi 6/6E. A single device can now be assigned multiple RUs simultaneously. Example: Instead of just one 106-tone RU, a device could get two 52-tone RUs + one 26-tone RU at once, maximizing bandwidth usage.
• If part of a channel is interfered with (e.g., 40 MHz blocked in the middle of a 160 MHz channel), Wi-Fi 6 would discard the entire channel. Wi-Fi 7 allows puncturing the bad portion and still using the remaining clean spectrum.

Figure-1 Multi-RU Puncturing in Wi-Fi 7

Wi-Fi 7 Preamble Puncturing

• In Wi-Fi, every transmission starts with a preamble, which is like the “header” or “handshake signal” which is used for following reasons.

  • Tells devices when a transmission is coming.
  • Carries control information (like channel width, modulation, coding, etc.).
  • Ensures all devices listening on the channel know how to interpret the data.

• Instead of discarding the whole wide channel, Wi-Fi 7 can “puncture” (skip over) the interfered subchannels while keeping the rest active.

• Example : A 160 MHz channel might have interference in one 20 MHz subchannel. Wi-Fi 6 falls back to 80 MHz total. Wi-Fi 7 removes the bad 20 MHz and still uses the remaining 140 MHz.

Advantages of Puncturing in Wi-Fi 7

Following are some of the benefits of puncturing in WiFi 7.

1. It offers higher spectral efficiency.
2. It offers increased throughput.
3. It offers better Performance in Crowded Bands.
4. It offers improvement in user experience.
5. Preamble puncturing ensures wide bandwidth channels remain practical in real world scenarios. IoT sensors (which only need small RUs) and bandwidth hungry devices can coexist efficiently.

Key differences

Conclusion:

• Preamble puncturing equals keeping wide channels usable by ignoring bad subchannels.

• Multi-RU puncturing means allowing a device to use multiple small RUs and skip over bad ones for maximum efficiency.