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Multiuser HE Transmission

Transmission Mode Options

The available options for multiuser (MU) high efficiency (HE) transmissions are OFDMA, Full-band MU-MIMO, and mixed OFDMA and MU-MIMO. Applicability of these modes depend on SIGB compression usage.

  • When SIGB compression is not used:

    • The system behaves like OFDMA or like mixed OFDMA and MU-MIMO.

    • The HE-SIG-B Common field includes RU Allocation subfields to specify the RU assignment and the number of users per RU for each 20 MHz bandwidth segment.

  • Full-band MU-MIMO transmissions can use SIGB compression.

  • When SIGB compression is used, the HE-SIG-B field contains no Common field, and the RU allocation in the user fields adhere to a standard-specified pattern. Because there is no common field in this case, no allocation index is transmitted.

The 802.11ax Parameterization for Waveform Generation and Simulation example introduces the concepts associated with HE transmission modes, RU allocation, and parameterization.

OFDMA Allocation Index

When creating a wlanHEMUConfig object you must specify the value of the AllocationIndex property. Once the object is created, AllocationIndex is read-only.

The AllocationIndex property defines the resource unit (RU) allocation index or a set of RU allocation indices.

  • Specify a single allocation index using one integer in either of these forms:

    • An integer scalar

    • An 8-bit binary sequence specified as a string or character vector

  • Specify a multiple allocation indices using two, four, or eight integer values any of these forms:

    • A vector of integers

    • An 8-bit binary sequences specified as a string array

    • An 8-bit binary sequences specified as a cell array of character vectors

An RU is a group of 26, 52, 106, 242, 484, 996, or 2×996 subcarriers defining an allocation unit in time and frequency.

The values specified by AllocationIndex correspond to the 8-bit indices in the first column of IEEE® P802.11ax™/D2.0 [1], Table 28-24 (RU Allocation subfield). These 8-bit RU Allocation subfield values indicate the RU assignment and the number of users per RU. Together the RU assignment and the number of user fields per RU indicate the number of user fields in the user-specific field of HE-SIG-B.

When SIGB compression is not used, the HE-SIG-B field includes the Common field. The Common field carries the RU Allocation subfields in one or two content channels. Depending on the PPDU bandwidth, the Common field can contain multiple RU Allocation subfields. Frequency domain mapping of channel content into the Common field is discussed in Section of [1].

The format of the Common field is defined in Table 28-23 (Common field). An RU Allocation subfield in the Common field of HE-SIG-B consists of 8 bits that indicating this information for each 20 MHz PPDU BW:

  • RU assignment in the frequency domain — Indexes the size of the RUs and their placement in the frequency domain.

  • Number of user fields in a 20 MHz BW within the HE-SIG-B content channel — Number of users multiplexed in the RUs indicated by the arrangement. For RUs of size greater than or equal to 106-tones, that support MU-MIMO, the RU Allocation subfield indicates the number of users multiplexed using MU-MIMO. An HE-SIG-B consists of N RU Allocation subfields, where:

    • N = 1 for 20 MHz and 40 MHz HE-MU PPDUs

    • N = 2 for 80 MHz HE-MU PPDUs

    • N = 4 for 160 MHz and 80+80 MHz HE-MU PPDUs

This RU Allocation subfield table lists the allocation index and RU assignments. This table indicates the number of tones per RU and the number of users assigned for each allocation index.

These allocation indices list the RU assignments for 20 MHz subchannels (RU ≤ 242 tones).

These allocation indices list the RU assignments for greater than 20 MHz subchannels (RU > 242 tones).


[1] IEEE Std 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.

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