MRU in Wi-Fi 7 builds off OFDMA, a feature first introduced in Wi-Fi 6
Multiple Resource Unit (MRU) is a new feature in Wi-Fi 7 that builds off another feature first introduced in Wi-Fi 6: Orthogonal Frequency Division Multiple Access, or OFDMA. OFDMA establishes independently modulating subcarriers within frequencies, allowing for simultaneous transmissions to and from multiple clients, which increases throughput and reduces latency. MRU, then, provides enhanced interference mitigation and OFDMA efficiency, further reducing multiple-user latency by another 25%, according to some sources.
By making it possible to selectively puncture overlapping portions of the spectrum, MRU ensures that data travels only on clear frequencies, increasing data rates and reliability in congested Wi-Fi environments.
According to MediaTek, the MRU enhancement is achieved by assigning punctured resource units (RUs) — a unit used to denote a group of 78.125 kHz bandwidth subcarriers (tones) used in both DownLink (DL) and UpLink (UL) transmissions — to a device to “provide more variety of RU sizes to enhance OFDMA efficiency.”
“MRU can mitigate interference losses from 75% to just 25%. This is how a Wi-Fi 7 MRU STA can offer 3X effective data bandwidth availability than a Wi-Fi 6 STA in a dense network environment,” continued the company.
Further, latency can also be reduced when multiple users are trying to transmit data simultaneously if the access point (AP) supports MRU. Mediatek provided the following example in its white paper: “For example, four different users transmit different data lengths: the proportion of data length for users 1 to 2 to 3 to 4 is 2:2:3:1, respectively.” MRU, the paper goes on to argue, “can allocate RU in a more efficient way, achieving the shortest end-to-end latency versus Wi-Fi 5 and Wi-Fi 6 APs with a 33% and 25% latency reduction, respectively.”
In addition to OFDMA and MRU, Wi-Fi 7 also will also use multi-band/multi-channel aggregation and operation, and will support up to 30Gbps throughput, 320 MHz transmissions and the use of higher modulation orders, optionally supporting 4096-QAM — up from 1024-QAM in 802.11ax.
