WO 2020/112021
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`PCT/SG2019/050530
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`COMMUNICATION APPARATUS AND COMMUNICATION
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`METHOD FOR MULTI-BAND RANDOM ACCESS
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`TECHNICAL FIELD
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`The present disclosure is gencrally rclated to a communication apparatus and a
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`communication method.
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`In particular,
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`the disclosure relates, but
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`is not
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`limited,
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`to a
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`communication apparatus and a communication method for wireless multi-band random
`access.
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`BACKGROUND ART
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`Reference to backgroundart herein is not to be construed as an admission that such art
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`constitutes common general knowledge.
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`In the standardization of next-gencration Wirclcss Local Arca Network (WLAN)
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`technologies, a new radio access technology having backward compatibility with earlier
`
`standards, such as IEEE 802.1 1a/b/g/n/ac/ax technologies, has been discussed.
`
`In order to increase peak throughput and capacity over 802.1lax HE (High Efficiency)
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`WLAN,it has been considered to exploit multi-band operation over multiple frequency bands
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`such as, for example, over the 2.4 GHz, 5 GHz, and 6 GHz bands.
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`Communication methods
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`and apparatus
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`for
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`implementing multi-band Uplink
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`Orthogonal Frequency Division Multiple Access (OFDMA) based Random Access (UORA)
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`have not, however, been considered.
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`CITATION LIST
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`Non-Patent Literature:
`
`[NPL 1]
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`IEEE 802.11-18/0695r3, CIDs Related to UORA Procedure — Part
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`1
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`(Initialization), May 2018
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`[NPL 2] IEEE 802.11-18/0694r2, CIDs Related to UORA Procedure — Part 2, April
`
`2018
`
`2018
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`[NPL 3] IEEE 802.11-18/1525r1, EHT Features for Multi-Band Operation, September
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`[NPL 4] LEEE 802.11-18/1549r0, Recommended Direction for EHT, September 2018
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`SUMMARYOF INVENTION
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`One non-limiting and exemplary embodiment facilitates providing multi-band Uplink
`
`Orthogonal Frequency Division Multiple Access (OFDMA) based Random Access (UORA).
`
`In one general embodiment, the techniques disclosed here feature a communication
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`apparatus operating in at least a first band and a second band, the communication apparatus
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`comprising:
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`a receiver which, in operation, receives a signal including a Trigger frame allocating
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`at least one Random Access Resource Unit (RA-RU); and
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`a controller which, in operation:
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`sets a first Orthogonal Frequency Division Multiple Access
`
`(QFDMA)
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`random access backoff (OBO) counter according to a number of RA-RUs determined to be
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`eligible in at least one of the first and second bands in the received Trigger frame; and
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`randomly selects an eligible RA-RUin each ofthe at least one of the first and
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`second bands corresponding to the first OBO counter for Trigger Based (TB) Physical layer
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`Protocol Data Unit (PPDU) transmission whenthe first OBO counteris set to 0;
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`wherein the first OBO counter is initialized according to a first OFDMA Contention
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`Window (OCW).
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`In another general embodiment, the techniques described here feature a communication
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`method for uplink OFDMAbased random access, the method comprising:
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`initializing an OBO counter according to a first OCW;
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`receiving a signal including a Trigger frame having at least one RA-RU;
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`setting the firs’ OBO counter according to a number of RA-RUs determined to be
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`eligible in at least one of the first and second bands corresponding to a received Trigger
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`frame; and
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`randomly selecting an eligible RA-RU in each of the at least one of the first and
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`second bands corresponding to the first OBO counter for TB PPDU transmission when the
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`first OBO counteris set to 0.
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`It should be noted that general or specific embodiments may be implemented as a
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`system, a method, an intcgrated circuit, a computcr program, a storage medium, or any
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`selective combination thereof.
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`Additional benefits and advantages of the disclosed embodiments will become apparent
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`from the specification and drawings. The benefits and/or advantages may he individually
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`obtained by the various embodiments and features of the specification and drawings, which
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`need not all be provided in order to obtain one or more of such benefits and/or advantages.
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`BRIEF DESCRIPTION OF THE DRAWINGS
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`By way of example only, embodiments of the disclosure will be described more fully
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`hereinafter with reference to the accompanying figures, wherein:
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`Figure 1 illustrates an example wireless communications apparatus in the form of part
`
`of an access point (AP) or station (STA);
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`Figure 2 illustrates an example message transfer in multi-band Uplink Orthogonal
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`Frequency Division Multiple Access (OFDMA)based Random Access (UORA);
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`Figure 3 illustrates an example format of a Trigger frame for randomaccess;
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`Figure 4 illustrates an example UORA Parameter Set element according to a first
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`embodiment;
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`Figure 5 illustrates an example multi-band UORA procedure according to the first
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`embodiment;
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`Figure 6 illustrates a flow chart for an example method of implementing multi-band
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`UORAaccordingto the first embodiment;
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`Figure 7 illustrates an example UORA Parameter Set element according to a second
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`embodiment;
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`Figure 8 illustrates an example multi-band UORAprocedure according to the second
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`embodiment;
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`Figure 9 illustrates a first part of a flow chart for an example method of implementing
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`multi-band UORAaccording to the second embodiment;
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`Figure 10 illustrates a second part of the flow chart for the example method of
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`implementing multi-band UORAaccording to the second embodiment;
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`Figure 11 illustrates an example UORA Parameter Set element according to a third
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`embodiment;
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`Figure 12 illustrates another example UORA Parameter Set element according to the
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`third embodiment;
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`Figure 13 illustrates a flow chart for an example method of implementing multi-band
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`UORAaccording to the third embodiment;
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`Figure 14 illustrates another example format of a Trigger frame for random access;
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`Figure 15 illustrates an example configuration of an AP in greater detail; and
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`Figure 16 illustrates an example configuration of a STA in greater detail.
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`DETAILED DESCRIPTION
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`The present disclosure can be better understood with the aid of following figures and
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`embodiments. The embodiments described here are merely exemplary in nature and are used
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`to describe some of the possible applications and uses of the present disclosure and should
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`not be taken as limiting the present disclosure with regard to alternative embodimentsthat are
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`not explicitly described herein.
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`Figure 1 illustrates an example wireless communications apparatus 100 in the form of
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`part of an access point (AP) or station (STA), in which the present disclosure may be applied.
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`The apparatus 100 of figure 1 has a controller 110 and signal generation circuitry in the form
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`of a transmission signal generator 120 that generates signals under control of the controller
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`110. A radio transmitter 130 thereby transmits generated transmission signals via an antenna
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`140. The antenna 140 is also coupled to a radio receiver 150. Signal processing circuitry in
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`the form of a receive signal processor 160 receives signals from the radio receiver 150 and
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`processes them under control of the controller 110.
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`Transmitted and received signals may take any suitable form, but
`
`in the present
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`disclosure the signal typically includes a Physical Layer Protocol Data Unit (PPDU)and the
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`apparatus 100 may therefore be configured to, in operation, transmit and receive PPDUs.
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`In
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`the case of an AP the transmission signal generator 120 may generate a PPDU containing a
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`Trigger frame and/or a Multi-STA BlockAck frame and the radio recciver 150 may reccive
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`an Extremely High Throughput (EHT) Trigger Based (TB) PPDU.
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`In the case of a STA the
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`transmission signal generator 120 may generate an EHT TB PPDUandthe radio receiver 150
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`may receive a PPDU containing a Trigger frame and/or a Multi-STA BlockAck frame.
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`Inter-band channel aggregation can be utilized for higher data rates. An AP may
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`establish a Basic Service Set (BSS) with its operating channel set to an inter-band aggregated
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`channel which comprises two or more non-contiguous channels across multiple frequency
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`bands. For example, using a 20, 40, 80 or 160 MHz channel in the 5 GHz bandtogether with
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`a 20, 40, 80 or 160 MHz channel in the 6 GHz band.
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`An AP may transmit a PPDU, such as EHT Single User (SU) PPDU, EHT Multi-User
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`(MU) PPDU, or non-High Throughput (HT) duplicate PPDU for example, which carries one
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`or more identical Trigger frames in aggregated channels across multiple frequency bands to
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`trigger EHT TB PPDUtransmission in an inter-band aggregated channel.
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`In certain situations, such as to save power, a STA may await a Trigger frame only in
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`one band (e.g. 5 GHz band) and may havecircuitries for at least one other band (e.g. 6 GHz
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`band) in a deactivated or low power ‘sleep’ mode. The STA may wakc upthecircuitrics for
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`the at least one other band upon identification of a multi-band Trigger frame being received.
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`By adding a signaling that indicates a multi-band Trigger frame in a CommonInfofield of
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`the Trigger frame as shownin Figure 3 or Figure 14 allows early detection of a multi-band
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`Trigger frame. As a result, the AP may assign Random Access (RA) Resource Units (RUs) in
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`the at least one other bands even if it knows the STA has the circuitries for the at least one
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`other bandin a deactivated or low power ‘sleep’ mode.
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`Figure 2 illustrates an example message transfer in multi-band Uplink Orthogonal
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`Frequency Division Multiple Access (OFDMA) based Random Access (UORA). Band A
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`200, which may be the 5 GHz band for example, may communicate over an 80 MHz Primary
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`Channel (PCH) 210 and band B 300, which may be the 6 GHz band for example, may be
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`communication over an 80 MHz Secondary Channel (SCH) 310. An AP performs Enhanced
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`Distributed Channel Access (EDCA) in the PCH 210. When a backoff timer of the PCH 210
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`becomes zero, if the SCH 310 is idle during a certain period, e.g. Priority Interframe Spacing
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`(PIFS) 360, the AP may transmit a non-HT duplicate PPDU 220 containing more than one
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`identical Trigger frames in the aggregated PCH 210 and SCH 310. The Trigger frames
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`allocate at least one RA-RUs in the PCH 210 and/or SCH 310. After a Short Interframe
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`Spacing (SIFS) 240 following the reception of the at least one Trigger frames, if a STA wins
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`RA contention, it transmits an EHT TB PPDU 230 in the PCH 210, in the SCH 310 orin the
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`aggregated PCH 210 and SCH 310. The EHT TB PPDU 230 carries at least one Medium
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`Access Control (MAC) Protocol Data Unit (MPDU) or Aggregate MPDU (A-MPDU)
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`(collectively referred to as ‘(A)-MPDU’). After a SIFS 260, the AP may transmit a non-HT
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`duplicate PPDU 250 containing more than one identical Multi-STA BlockAck frames in the
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`aggregated PCH 210 and SCH 310. The Multi-STA BlockAck frames
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`include the
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`acknowledgementon the at least one (A)-MPDUin the received EHT TB PPDU 230.
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`Figure 3 illustrates an example format of a Trigger frame 400 for RA that schedules
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`RA-RUsin one or multiple frequency bands (e.g. 5 GHz and 6 GHz bands). The Trigger
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`frame 400 includes a User Info ficld 410 which has its subficlds shown in greater detail
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`including a RU Allocation subfield 412, a Band Indication subfield 414 and a RA-RU
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`Information subfield 420 indicating RA-RU information. The RA-RU Information subfield
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`420 includes a Number of RA-RU subfield 422 and a No More RA-RU subfield 424. The
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`RU Allocation subfield 412 indicates the first RU of one or more contiguous RA-RUsin a
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`band specified by a Band Indication subfield 414 of the User Info field 410. The Number Of
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`RA-RU subfield 422 indicates the number of contiguous RA-RUs minus one in the band
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`specified by the Band Indication subfield 414.
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`If there is more than one RA-RU in a band,
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`the sizes of all RA-RUs in the band are equal to the size of the first RU. AI] remaining
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`subfields of the User Info field 410 apply to all the RA-RUsin the band.
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`Figure 4 illustrates an example UORA Parameter Set element 450 accordingtoafirst
`
`embodiment. The UORA Parameter Set element 450 can be included in a management frame
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`such as, for example, a Beacon frame, Probe Response frame, (Re)association Response
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`frame, etc. The UORA Parameter Set element 450 contains an OFDMA Contention Window
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`(OCW) Rangefield 452 that indicates an OCW range. The OCW Rangefield 452 contains
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`an EOCWmin subfield 454 and an EOCWmaxsubfield 456 that indicate the OCW range.
`This may be achieved by having OCWmin being derived by the equation Qhocwmin 1 and
`OCWmaxbeing derived from the equation 2°°-¥™-1,
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`According to the first embodiment, a communication apparatus, such as a STA, shall
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`maintain an internal OCW and OFDMArandom access backoff (OBO) counter. Prior to an
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`initial attempt of RA transmission, or after each successful RA transmission, the STA mayset
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`the value of OCW to OCWmin and may initialize its OBO counter to an integer value
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`randomly selected from a uniform distribution in the range 0 to OCW. The OCWmin and
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`OCWmax maybe obtained from a most recently reccived UORA Parameter Sct clement (c.g.
`
`see figure 4) from an APor, if a UORA Parameter Set element was not received, predefined
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`default values.
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`Upon receipt of a Trigger frame containing at least one RA-RU determined to be
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`eligible (‘eligible RA-RU(s)’) from an AP, if the OBO counter of a STA is not greater than a
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`numberof eligible RA-RUsin the Trigger frame, the STA sets its OBO counter to zero and
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`randomly selects an eligible RA-RUin each of its operating band(s). Otherwise, the STA
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`decrements its OBO counter by the numberof eligible RA-RUs in the Trigger frame. A STA
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`should not contend for an eligible RA-RU or decrement its OBO counter if it does not have
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`pending frames for the AP.
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`An RA-RUis determined to be eligible if the STA is capable of generating an EHT TB
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`PPDU (xe. the STA supports all transmit parameters indicated in the CommonInfo field and
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`in the User Info field corresponding to the RA-RU) and maysatisfy at least one of the
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`following conditions: (1) that the STA is not associated with a BSS thatit intends to transmit
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`frames to and a predetermined subfield of the User Info field of the Trigger frame, such as the
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`AID12 subfield,
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`is a first predetermined number, such as 2045; and (2) the STA is an
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`associated STA and a Transmitter Address (TA) field of the Trigger frame is set to a BSS
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`identifier (BSSID) of the associated BSS and the predetermined subfield of the User Info
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`field of the Trigger frame, such as the AID12 subfield, is a second predetermined number,
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`such as 0.
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`If all the selected RU(s) are considered busy as a result of either physical or virtual
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`Carrier Sense (CS), a STA may not transmit EHT TB PPDU and the STA mayset its OBO
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`counter to a random value drawn from a uniform distribution in the range 0 to OCW. If only
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`one of the selected RA-RU(s)is idle as a result of both physical and virtual CS, the STA may
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`transmit an EHT TB PPDUinthis idle RU.
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`If two RA-RUs are selected and both the selected RA-RUs are idle as a result of both
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`physical and virtual CS then a STA mayeither down select one RU from both the selected
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`RUs and transmits an EHT TB PPDUat this RU or transmit an EHT TB PPDU with the same
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`(A)-MPDU in each of the selected RUs. Advantageously the probability for successful
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`transmission of (A)-MPDUincreasesas a result.
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`Figure 5 illustrates an example multi-band UORA procedure according to the first
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`embodiment for a Dual Band (DB) operating STA 1 with an Association Identifier (AID) of
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`5, a 6 GHz Single Band (SB) operating STA 2 with an AID of 7, a5 GHz SB operating STA
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`3 that is unassociated, and a DB operating STA 4 with an AID of 3. DB operating STAs are
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`operating in both bands at a time (i.e. able to simultaneously transmit or receive frames at
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`both bands) and SB operating STAs are operating in either of both bands at a time(i.e. able to
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`transmit or receive frames at either of two bands at a time). An SB operating STA may be a
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`SB only STA capable of supporting either of both bands or a DB capable STA which is
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`capable of supporting both bands but has reduced its operating bands to either of both bands,
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`such as for power saving purposes.
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`In the example of Figure 5, before a Trigger frame was sent by an AP, STA 1, STA 2,
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`STA 3 and STA 4 had initial OBO values of 5, 7, 4 and 2 respectively. Upon receiving the
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`Trigger frame, STA 4, which is associated with the AP and has pending frames for the AP,is
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`allocated a dedicated RU (RU6). STA 4 does not contend for RA-RUs and instead transmits
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`its pending frames on RU6. STA 1, operating in both bands, associated with the AP and
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`having pending frames for the AP, decrement its OBO counter by the numberofeligible RA-
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`RUs in both bands indicated in the Trigger frame (i.ec., five RA-RUs in both bands with
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`AID12 subfield equal to 0). Since STA 1's OBO counter decrements to O, it transmits its
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`pending frames on RU1 in 6 GHz band whichit randomly selects from the eligible set of RUs
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`(Le., RU1, RU2 and RU3 in 5 GHz band and RU1 and RU2 in 6 GHz band). STA 2,
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`operating in 6 GHz band, associated with the AP and having pending frames for the AP,
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`decrement its OBO counter by the numberof cligible RA-RUs in 6 GHz bandindicated in the
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`Trigger frame (i.c., two RA-RUs in 6 GHz band with AID12 subficld cqual to 0). Since STA
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`2's OBO counter decrements to a nonzero value, it maintains the new OBO value (5) until it
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`receives a later Trigger frame carrying RA-RUs for associated STAs. STA 3, whichis
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`operating in 5 GHz band, not associated with the AP but has a pending frame for the AP,
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`decrements its OBO counter by the number of eligible RA-RUsin the 5 GHz bandindicated
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`in the Trigger frame (i.e., two RA-RUs in 5 GHz band with AID12 subfield equal to 2045).
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`Since STA 3's OBO counter decrements to a nonzero value, it maintains the new OBO value
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`(2) until it receives a later Trigger frame carrying RA-RUs for unassociated STAs.
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`If an EHT TB PPDUthat solicits an immediate response is transmitted in a single
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`selected RA-RU and the expected responseis not received, the RA transmission is considered
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`unsuccessful. Otherwise, the RA transmission is considered successful. Similarly, if an EHT
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`TB PPDU with same (A)-MPDUthat solicits an immediate response is transmitted in each of
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`two selected RA-RUsand neither of the expected responses is received, the RA transmission
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`is considered unsuccessful. Otherwise, the RA transmission is considered successful.
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`If an RA transmission is considered unsuccessful, the STA may, for example, update its
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`OCW to 2*OCW + 1 when the OCWisless than the value of OCWmax, and may randomly
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`select its OBO counter in the range of 0 to OCW. Once the OCW reaches OCWmax for
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`successive retransmission attempts, the OCW may remain at the value of OCWmax until the
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`OCWis reset. A STA may update its OCW value as long as the updated OCW remains in
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`the range OCWmin to OCWmax obtained from the most recently received UORA Parameter
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`Set element.
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`If the updated OCW becomes greater than OCWmax as consequence of
`
`receiving a modified UORA Parameter Set element, then the STA mayset the value of OCW
`
`to the new OCWmaxvalue.
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`Figure 6 illustrates a flow chart for an example method of implementing multi-band
`
`UORAaccording to the first embodiment at a STA. The methodstarts by setting OCW to
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`OCWmin at step 600 and then initializes the OBO counter at step 610 before waiting until a
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`Trigger frame for RA is received at step 612. At step 614 a determination is made as to
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`whether there are any pending frames for the AP.
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`If not, then the STA reverts back to
`
`waiting until a Trigger frame for RA is received at step 612.
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`If so,
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`then a further
`
`determination is made as to whether the OBO counteris smaller than, or equal to, the number
`
`of eligible RA-RUsin the Trigger frameat step 616. If not, the OBO counter is decremented
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`by the numberof eligible RA-RUs in the Trigger frame at step 618 and the STA reverts back
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`to waiting until a Trigger frame for RA is received at step 612. If so, the OBO counteris sect
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`to 0 at step 620.
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`Once the OBO counteris set to O at step 620, the STA randomly selects one of the
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`eligible RA-RUsin each of its operating band(s) at step 622 and then a determination is made
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`as to whether at least one of the selected RA-RU(s) is idle at step 624.
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`If not, then the STA
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`reverts back to initialize the OBO counter at step 610.
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`If so, then a further determinationis
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`made as to whether only onc of the selected RA-RU(s)is idle at step 626.
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`If only one of the selected RA-RU(s) is determined to be idle at step 626, the STA
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`transmits an EHT TB PPDU at this RA-RU at step 628 and makes a determination as to
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`whether the transmission was successful at step 630. If so, the STA goes back to the first step
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`of setting OCW to OCWminat step 600.
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`If not, then a determination is made as to whether
`
`OCW is less than OCWmax at step 632 and, if so, OCW is updated to min{2*OCW+1,
`
`OCWmax} at step 634. The STA then gocs back to initializing the OBO counterat step 610.
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`If more than one of the selected RA-RUsis determinedto be idle at step 626, there are
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`two proposed options. Option 1 is to down select one of both the selected RA-RUsat step
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`636 and then proceed to transmitting an EHT TB PPDU at this RA-RUat step 628. Option 2
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`is to transmit an EHT TB PPDU with the same (A)-MPDU in each of both the selected RA-
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`RUsat step 638 and move on to determining whether the transmission was successful at step
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`630.
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`As may be appreciated, DB operating STAs are advantageous to SB operating STAsin
`
`UORAsince DB operating STAs can contend all eligible RA-RUs in both bands while SB
`
`operating STAs can contend cligible RA-RUs in a single band and the same OCWmin and
`
`OCWmaxare used by SB and DB operating STAs.
`
`Figure 7 illustrates an example UORA Parameter Set element 650 according to a
`
`second embodiment whereby each band has a band-specific OCW range. For example,
`
`OCWS5min and OCW5max may represent an OCW range specific to the 5GHz band and
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`OCWobmin and OCW6max may represent an OCW range specific to the 6GHz band. The
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`OCW Range 1 ficld 652 and OCW Range 2 ficld 660 in the UORA Parameter Sct clement
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`650 indicate an OCW range, e.g. via an EOCWmin subfield 654 and an EOCWmaxsubfield
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`656, for the band indicated by the BandIndication subfield 658.
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`As with before,
`
`the UORA Parameter Set element 650 may be included in a
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`management
`
`frame such as,
`
`for example,
`
`a Beacon frame, Probe Response frame,
`
`(Re)association Response frame, etc. However, when a UORA Parameter Set element is
`
`included in an individually addressed frame (c.g. (Re)association Response frame) it may
`
`only include the OCW rangespecific to the operating band(s) of the intended recipient for the
`
`individually addressed frame.
`
`A SB operating STA may maintain a single internal OCW anda single internal OBO
`
`counter for its operating band. For a SB operating STA, the method of implementing UORA
`
`for the second embodiment could therefore be the same as for the first embodiment. A DB
`
`operating STA may maintain an intcrnal OCW and internal OBO countcr per band. For
`
`example, OCW5 and OBOS5counters may represent OCW and OBO counters specific to the
`
`5 GHz first band and OCW6 and OBO6 counters may represent OCW and OBO counters
`
`specific to the 6 GHz second band. These bands (i.e. 5 GHz and 6 GHz) are for example only
`
`and it should be appreciated that other suitable frequency bands could be utilized. As may be
`
`appreciated, DB operating STAs have similar contention opportunities to SB operating STAs
`
`in UORA since the OCW and OBO counters are band-specific and DB operating STAs
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`contend RA-RUsin each band independently.
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`For a DB operating STA to operate multi-band UORA there may be some options. For
`
`example, a first option is to independently operate a UORA procedure for a first band (e.g. 5
`
`GHz band) and another UORA procedure for a second band (e.g. 6 GHz band). With this
`
`option, the STA behaves like two independent SB operating STAs with, for example, the
`
`operating bands of 5 GHz and 6 GHzrespectively. A second option is to operate a single
`
`UORAprocedure for both bands.
`
`In the second embodiment, using the second option described above, a DB operating
`
`STA, prior to an initial attempt of RA transmission or after each successful RA transmission,
`
`sets values of OCW5 and OCW6 to OCW5min and OCW6min and then initializes its OBOS5
`
`counter to an integer value randomly selected from a uniformdistribution in the range 0 to
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`OCW5 and its OBO6 counter to an integer value randomly selected from a uniform
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`distribution in the range 0 to OCW6.
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`After each partially successful RA transmission in the 5 GHz band, for example, a DB
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`operating STA may set the value of OCW5 to OCW5min and may initialize its OBOS
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`counter to an integer value randomly selected from a uniform distribution in the range 0 to
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`OCWS5S. Similarly, after each partially successful RA transmission in the 6 GHz band, a DB
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`operating STA may set the value of OCW6 to OCWé6min and mayinitialize its OBO6
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`counter to an integer value randomly selected from a uniform distribution in the range 0 to
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`OCW6.
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`Uponthe reception of a Trigger frame containing at least one eligible RA-RU from an
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`AP, if the OBOS5 counter of a DB operating STA is not greater than the numberof eligible
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`RA-RUsin the 5 GHz band in the Trigger frame, then the DB operating STA shall set its
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`OBOS5counter to zero. Otherwise, the DB operating STA decrements its OBOS5 counter by
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`the numberof eligible RA-RUs in the 5 GHz bandin the Trigger frame. If the OBO6 counter
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`of a DB operating STA is not greater than the number of eligible RA-RUsin the 6 GHz band
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`in the Trigger frame,
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`then the DB operating STA shall set
`
`its OBO6 counter to zero.
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`Otherwise, the DB operating STA decrements its OBO6 counter by the numberofeligible
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`RA-RUsin 6 GHzbandin the Trigger frame.
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`If both OBOS and OBC6 counters are zero a DB operating STA may randomlyselect
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`one of the eligible RA-RUs in each band.
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`If only one of the OBO5 and OBC6 counters is
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`zero, a DB operating STA may randomly select one of the eligible RA-RUs in the band
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`whose corresponding OBO counteris set to 0.
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`If all selected RA-RU(s) are considered busy as a result of either physical or virtual CS,
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`the STA maynot transmit an ENT TB PPDUand the STA mayinstead set its OBO5 counter
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`to a random value drawn from a uniform distribution in the range 0 to OCW5and, similarly,
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`set its OBO6 counter to a random value drawn from a uniformdistribution in the range 0 to
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`OCW68.
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`If only one of the selected RA-RU(s) is idle as a result of both physical and virtual
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`CS, the STA may transmit an EHT TB PPDUin this RU.
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`A few options are envisaged if two RA-RUs are selected and both the selected RUs are
`
`idle as a result of both physical and virtual CS. For example, option 1 is for the STA to down
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`select one RU from both the selected RUs and transmits an EHT TB PPDU in this RU.
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`Option 2 is for the STA to transmit an EHT TB PPDU with a same (A)-MPDUin each of
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`both the selected RUs which should increase the probability for successful transmission of
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`(A)-MPDU. Option 3 is for the STA to transmit an EHT TB PPDU with a different (A)-
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`MPDUineach of both the selected RUs which should increase throughput.
`
`Figure 8 illustrates an example multi-band UORA procedure according to the second
`
`embodiment for a DB operating STAI with an AID of 5, a 6GHz SB operating STA2 with an
`
`AID of 7, a 3GHz SB operating STA3 that is un-associated, and a DB operating STA4 with
`
`an AID of 3.
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`In the cxample of Figure 8, before a Trigger frame was scnt by the AP, STA 1 had
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`initial OBOS and OBO6 values of 4 and 2 respectively, STA 2 had initial OBO6 value of 2,
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`STA 3 had initial OBOS5 value of 4; and STA 4 had initial OBO5 and OBO6 values of 2.
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`Uponreceiving the Trigger frame, STA 4, which is associated with the AP and has pending
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`frames for the AP, is allocated a dedicated RU (RU6). STA 4 does not contend for RA-RUs
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`and instead transmits its pending frames on RU6. STA 1, operating in both bands, associated
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`with the AP and having pending frames for the AP, decrement its OBOS5 and OBO6 counter
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`by the numberof eligible RA-RUs in 5 GHz and 6 GHz bandsindicated in the Trigger frame,
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`respectively (i.e., three RA-RUs in 5 GHz band with AID12 subfield equal to 0 and two RA-
`
`RUs in 6 GHz band with AID12 subfield equal
`
`to 0). Since STA 1's OBO6 counter
`
`decrements to 0, it transmits its pending frames on RU1 in 6 GHz band which it randomly
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`selects from the cligible sct of RUs (.c., RU] and RU2 in 6 GHz band). STA 2, opcrating in
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`6 GHz band, associated with the AP and having pending frames for the AP, decrementits
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`OBO6 counter by the number of eligible RA-RUs in 6 GHz band indicated in the Trigger
`
`frame (i.e., two RA-RUs in 6 GHz band with AID 12 subfield equal to 0). Since STA 2's
`
`OBO6 counter decrements to O, it transmits its pending frames on RU2 in 6 GHz band which
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`it randomly selects from the eligible set of RUs G.e., RUJ and RU2 in 6 GHz band). STA 3,
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`whichis operating in 5 GHz band, not associated with the AP but has a pending frame for the
`
`AP, decrements its OBO counter by the numberof eligible RA-RUs in the 5 GHz band
`
`indicated in the Trigger frame (i.e., two RA-RUs in 5 GHz band with AID12 subfield equal
`
`to 2045). Since STA 3's OBO counter decrements to a nonzero value, il maintains the new
`
`OBO value (2) until it receives a later Trigger frame carrying RA-RUs for unassociated
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`STAs.
`
`In the second embodiment, RA transmissions are considered to be successful if: an
`
`EHT TB PPDUthat solicits an immediate response is transmitted in a single selected RA-RU
`
`and the expected response is received, an EHT TB PPDU with a same (A)-MPDUthat
`
`solicits an immediate responseis transmitted in each of two selected RA-RUsandat least one
`
`of the expected responses is received, or an EHT TB PPDU with a different (A)-MPDUthat
`
`solicits an immediate response is transmitted in each of two selected RA-RUsand both of the
`
`expected responsesare received.
`
`In the second embodiment, RA transmissions are considered to be unsuccessful if: an
`
`EHT TB PPDUthat solicits an immediate response is transmitted in a single selected RA-RU
`
`and the expected responseis not received or an EHT TB PPDU with a same (A)-MPDUor a
`
`different (A)-MPDU that solicits an immediate response is transmitted in each of two
`
`selected RA-RUsandneither of the expected responsesis received.
`
`An RA transmission is considered to be partially successful in the first (5 GHz) band
`
`and partially unsuccessful in the second (6 GHz) band if an EHT TB PPDUwitha different
`
`(A)-MPDUthat solicits an immediate response is transmitted in each of two selected RA-
`
`RUs and only the expected response in the first (5 GHz) band is received. An RA
`
`transmission is considered to be partially unsuccessful in the first (5 GHz) band andpartially
`
`successful in the second (6 GHz) band if an EHT TB PPDU with a different (A)-MPDU that
`
`solicits an immediate response is transmitted in each of two selected RA-RUs and only the
`
`expected response in the second (6 GHz) bandis received.
`
`In the event that an RA transmission is considered to be unsuccessful, a STA may
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`update its OCW5 to 2*OCW5+1 when the OCWS5is less than the value of OCW5max and
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`update its OCW6to 2*OCW6+1 when the OCW6is less than the value of OCW6max. The
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`STA may randomly select its OBOS counter in the range of O and OCW5 and its OBO6
`
`counter in the range of O and OCW6. Once the OCW5 reaches OCW5max, for successive
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`retransmission attempts, the OCWS5shall remain at the value of OCW5max until the OCW5
`
`is reset. Once the OCW6 reaches OCW6max, for successive retransmission attempts, the
`
`OCW6 shall remain at the value of OCW6max until the OCW6is reset.
`
`If the RA transmission is considered to be partially unsuccessful in the first (5 GHz)
`
`band, the STA may update its OCW5 to 2*OCW5 + 1 when the OCW5Sis less than the value
`
`of OCW5max, and may randomly sclect its OBOS counter in the range of 0 and OCW5S.
`
`Once the OCW5 reaches OCW5max for successive retransmission attempts, the OCW5 may
`
`remain at the value of OCW5maxuntil the OCW5Sis reset.
`
`If the RA transmission is considered to be partially unsuccessful in the second (6 GHz)
`
`band, the STA may update its OCW6to 2*OCW6 + 1 when the OCW6