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Packet Size and Duration Dependencies

WLAN standards specify a maximum packet duration (TXTIME) for the various formats. The HE and S1G formats additionally specify the maximum PSDU length (PSDU_LENGTH) and number of symbols (NSYM). These WLAN properties are functions of transmission properties set in WLAN Toolbox™ configuration objects. The settings of WLAN format-specific configuration objects are validated when the object is used. Command-line feedback informs you when the configuration violates the packet size or duration limits.

This table indicates relevant properties that help determine the packet duration and length for the various WLAN formats. It also provides references to the IEEE® standards for further details.

WLAN FormatLength-Related ValidationRelevant and Dependent Properties
HE

TXTIME and PSDU_LENGTH require validation.

TXTIME and PSDU_LENGTH are defined by the equations in section 27.4.3 of [2].

As specified by aPPDUMaxTime and aPSDUMaxLength in Table 27-53, the maximum TXTIME is 5.484 ms and the maximum PSDU_Length is 6,500,631 octets.

For single user HE and single user extended range HE:

For PSDU_LENGTH:

  1. ChannelBandwidth

  2. NumSpaceTimeStreams

  3. STBC

  4. MCS

  5. DCM

  6. ChannelCoding

  7. APEPLength

For TXTIME:

  1. All the above PSDU_LENGTH properties

  2. ExtendedRange

  3. GuardInterval

  4. HELTFType

  5. HighDoppler

  6. MidamblePeriodictiy(he_1)

For multiuser HE:

The PSDU_LENGTH is different for each user in the configuration, but the transmit time is the same (like VHT). For PSDU_LENGTH:

  • Can vary per user:

    1. User RU size is based on:

      1. AllocationIndex

      2. ChannelBandwidth, which is derived from AllocationIndex

      3. Lower26ToneRU(he_2)

      4. Upper26ToneRU(he_2)

    2. NumSpaceTimeStreams

    3. MCS

    4. DCM

    5. ChannelCoding

    6. APEPLength

  • Same for all users:

    • STBC

For TXTIME:

  1. The above PSDU_LENGTH properties that can vary per user

  2. GuardInterval

  3. HELTFType

  4. SIGBCompression(he_3)(he_4)

  5. SIGBMCS

  6. SIGBDCM

  7. HighDoppler

  8. MidamblePeriodictiy(he_1)

Notes:

(he_1) MidamblePeriodictiy is only relevant when HighDoppler is true.

(he_2) Lower26ToneRU and Upper26ToneRU are only relevant if the user for which the PSDU_LENGTH is derived is allocated on either of these RUs.

(he_3) If SIG-B compression is used, there is common field in HE-SIG-B field that affects the TXTIME computation.

(he_4) The SIGBCompression property is only relevant when a full-band 20 MHz allocation is specified.

DMG

TXTIME requires validation.

TXTIME is defined by the equations in section 20.12.3 of [1].

As specified by aPPDUMaxTime in Table 20-32, the maximum TXTIME is 2 ms.

  1. MCS (dmg_1)

  2. PSDULength

  3. TrainingLength (dmg_1)

  4. PacketType (dmg_1)

  5. BeamTrackingRequest (dmg_1)

Notes:

(dmg_1) The property helps determine whether the packet is a beam refinement protocol (BRP) packet containing training fields or if it is a general packet signaling the number of fields to append. For more information, see [1]

S1G

TXTIME, PSDU_LENGTH, and NSYM require validation.

The equations for all three of these characteristics are in section 24.4.3 of [3], and the maximum TXTIME and PSDU_LENGTH are defined in Table 24-37.

In Table 24-37:

  • As specified by aPPDUMaxTime, the maximum TXTIME is 27.92 ms. This TXTIME is the maximum PPDU duration for an S1G_1M PPDU with:

    • A bandwidth of 1 MHz

    • S1G MCS set to 10

    • One spatial stream, limited by a PSDU length of 511 octets.

  • As specified by aPPDUMaxLength, the maximum PSDU_LENGTH is 797,159 octets. This PSDU length is the maximum length in octets for an S1G SU PPDU with:

    • A bandwidth of 16 MHz

    • S1G-MCS set to 9

    • Four spatial streams, limited by 511 data symbols supported by the Length field in the S1G SIG field, excluding the SERVICE field and tail bits.

  • The maximum NSYM is 511.

For TXTIME, the relevant properties are:

  1. ChannelBandwidth

  2. STBC (s1g_1)

  3. GuardInterval

  4. ChannelCoding (MU)

  5. APEPLength (MU)

  6. PSDULength – This property is read-only. When undefined, PSDULength is returned as empty of size 1×0. An empty return can happen when the set of property values for the object define an invalid state. (MU)

  7. MCS (MU)

  8. NumSpaceTimeStreams (MU)

  9. NumUsers

For PSDU_LENGTH and NSYM, the relevant properties are:

  1. ChannelBandwidth

  2. STBC (s1g_1)

  3. ChannelCoding (MU)

  4. APEPLength (MU)

  5. PSDULength – This property is read-only. When undefined, PSDULength is returned as empty, []. An empty return can happen when the set of property values for the object define an invalid state. (MU)

  6. MCS (MU)

  7. NumSpaceTimeStreams (MU)

  8. NumUsers

Notes:

(s1g_1) The property is relevant only when NumUsers = 1.

(MU) The property has multiple values for multiuser operation.

VHT

TXTIME requires validation.

TXTIME is defined by the equations in section 21.4.3 in [1].

As specified by aPPDUMaxTime in Table 21-29, the maximum TXTIME is 5.484 ms.

  1. ChannelBandwidth

  2. STBC (vht_1)

  3. GuardInterval

  4. ChannelCoding (MU)

  5. APEPLength (MU)

  6. PSDULength – This property is read only. When undefined, it is returned as an empty of size 1×0.(MU)

  7. MCS (MU)

  8. NumSpaceTimeStreams (MU)

  9. NumUsers

Notes:

(vht_1) The property is relevant only when NumUsers = 1.

(MU) The property has multiple values for multiuser operation.

HT

TXTIME requires validation.

TXTIME is defined by the equations in section 19.4.3 of [1].

As specified in Table 9-19, the maximum TXTIME for HT mixed PPDUs is 5.484 ms.

  1. ChannelBandwidth

  2. GuardInterval

  3. ChannelCoding

  4. PSDULength

  5. MCS

  6. NumSpaceTimeStreams

  7. NumExtensionStreams

non-HT

TXTIME requires validation.

TXTIME for OFDM modulation is defined by the equations in section 17.4.3 of [1].

Based on equation (17–29) and a valid combination of property settings, the maximum TXTIME is 21.936 ms.

  1. Modulation (non-ht_1)

  2. PSDULength

  3. MCS (non-ht_1)

  4. DateRate (non-ht_1)

Notes:

(non-ht_1) DataRate or MCS might be relevant depending on the Modulation setting.

References

[1] IEEE Std 802.11™-2016 (Revision of IEEE Std 802.11-2012). “Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications.” IEEE Standard for Information technology — Telecommunications and information exchange between systems. Local and metropolitan area networks — Specific requirements.

[2] IEEE P802.11ax™/D4.1. “Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications. Amendment 1: Enhancements for High Efficiency WLAN.” Draft Standard for Information technology — Telecommunications and information exchange between systems. Local and metropolitan area networks — Specific requirements.

[3] IEEE Std 802.11ah™-2016 (Amendment to IEEE Std 802.11-2016 as amended by IEEE Std 802.11ai™-2016). “Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications. Amendment 2: Sub 1 GHz License Exempt Operation.” IEEE Standard for Information technology — Telecommunications and information exchange between systems. Local and metropolitan area networks — Specific requirements.

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