Resouce Unit (RU) is a unit in OFDMA terminology used in 802.11ax to denote a group of subcarriers (tones) used in both download and upload transmission. With OFDMA, different transmit powers may be applied to different RUs. In OFDMA, there are maximum of 9 RUs for 20 MHz, 18 in case of 40 MHz and more in case of 80 or 160 MHz. ^[1]

Description

In OFDMA, an OFDM symbol is constructed of subcarriers where the total number defines a PPDU bandwidth. Each user is assigned different subsets of subcarriers to achieve simultaneous data transmission in MU (Multi-Users) environment. The more subcarriers are used, the longer their symbol rate is, which means that the overall rate of information remains the same.

There are a few RUs currently defined: 26-tone RU, 52-tone RU, 106-tone RU, 242-tone RU, 484-tone RU, 996-tone RU and 2x996-tone RU. For basic 20 MHz bandwidth, nine 26-tone RUs can be used, but only four with 52-tone RUs. ^[1]

=Reference

^ ^a ^b 802.11 Working Group (October 2017). IEEE P802.11ax™/D2.0 Draft Standard for Information technology— Telecommunications and information exchange between systems Local and metropolitan area networks—Specific requirements: Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications; Amendment 6: Enhancements for High Efficiency WLAN. IEEE. {{cite book}}: |access-date= requires |url= (help)CS1 maint: numeric names: authors list (link)

[80211ax-1] 802.11 Working Group (October 2017). IEEE P802.11ax™/D2.0 Draft Standard for Information technology— Telecommunications and information exchange between systems Local and metropolitan area networks—Specific requirements: Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications; Amendment 6: Enhancements for High Efficiency WLAN. IEEE. {{cite book}}: |access-date= requires |url= (help)CS1 maint: numeric names: authors list (link)

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