The Measurement Start Time field shall be set to the TSF at the time (± 32 μs) at which the requested CCA request measurement shall start. A value of 0 shall indicate it shall start immediately.
The Measurement Duration field shall be set to the duration of the requested measurement, expressed in TUs.
7.3.2.21.3 RPI histogram request
A Measurement Type in the Measurement Request element may indicate an RPI histogram request. A response to an RPI histogram request is an RPI histogram report. It is optional for a STA to generate a RPI histogram report in response to a RPI histogram request. The Measurement Request field corresponding to an RPI histogram request is shown in Figure 7-62.
The Channel Number field shall be set to the channel number for which the measurement request applies (as defined in 17.3.8.3.3).
The Measurement Start Time field shall be set to the TSF at the time (± 32 μs) at which the requested RPI histogram request measurement shall start. A value of 0 shall indicate it shall start immediately.
The Measurement Duration field shall be set to the duration of the requested measurement, expressed in TUs.
7.3.2.22 Measurement Report element
The Measurement Report element contains a measurement report. The format of the Measurement Report element is shown in Figure 7-63.
The Length field is variable and depends on the length of the Measurement Report field. The minimum value of the Length field is 3.
The Measurement Token field shall be set to the Measurement Token in the corresponding Measurement Request element. If the Measurement Report element is being sent autonomously, then the Measurement Token shall be set to 0.
The Measurement Report Mode field (shown in Figure 7-64) is a bit field with the following bits defined:
— Late bit (bit 0) indicates whether this STA is unable to carry out a measurement request because it received the request after the requested measurement time. The Late bit shall be set to 1 to indicate the request was too late. The Late bit shall be set to 0 to indicate the request was received in time for the measurement to be executed.
— Incapable bit (bit 1) indicates whether this STA is incapable of generating a report of the type specified in the Measurement Type field that was previously requested by the destination STA of this Measurement Report element. The Incapable bit shall be set to 1 to indicate the STA is incapable. The Incapable bit shall be set to 0 to indicate the STA is capable or the report is autonomous.
— Refused bit (bit 2) indicates whether this STA is refusing to generate a report of the type specified in the Measurement Type field that was previously requested by the destination STA of this Measurement Report element. The Refused bit shall be set to 1 to indicate the STA is refusing. The Refused bit shall be set to 0 to indicate the STA is not refusing or the report is autonomous.
— All other bits are reserved and shall be set to 0.
The Measurement Type field shall be set to a number that identifies the measurement report. The
Measurement Types that have been allocated are shown in Table 7-30.
The Measurement Report field shall be null when the Late bit is set to 1, the Incapable bit is set to 1, or the Refused bit is set to 1. Otherwise, it shall contain the specification of the measurement report, as described in 7.3.2.22.1 through 7.3.2.22.3.
The Measurement Report element is included in a Measurement Report frame as described in 7.4.1.2. The use of Measurement Report elements and frames is described in 11.9.6.
7.3.2.22.1 Basic report
A Measurement Type in the Measurement Report element may indicate a basic report. The format of the Measurement Report field corresponding to a basic report is shown in Figure 7-65. It is mandatory for a STA to support the generation of this report.
The Channel Number field shall be set to the channel number to which the basic report applies (as defined in 17.3.8.3.3).
The Measurement Start Time field shall be set to the TSF at the time (± 32 μs) at which the basic report measurement started.
The Measurement Duration field shall be set to the duration over which the basic report was measured, expressed in TUs.
The Map field is coded as a bit field, as shown in Figure 7-66, and shall contain the following bits:
— BSS bit, which shall be set to 1 when at least one valid MPDU was received in the channel during the measurement period from another BSS or IBSS. Otherwise, the BSS bit shall be set to 0.
— OFDM preamble bit, which shall be set to 1 when at least one sequence of short training symbols, as defined in 17.3.3, was detected in the channel during the measurement period without a subsequent valid Signal field (see 17.3.4). This may indicate the presence of an OFDM preamble,such as highperformance RLAN/2 (HIPERLAN/2). Otherwise, the OFDM preamble bit shall be set to 0.
— Unidentified Signal bit, which may be set to 1 when significant power is detected in the channel during the measurement period that cannot be characterized as radar, an OFDM preamble, or a valid MPDU. Otherwise, the Unidentified Signal bit shall be set to 0. The definition of significant power is implementation dependent.
— Radar bit, which shall be set to 1 when radar was detected operating in the channel during the measurement period. The algorithm to detect radar shall satisfy regulatory requirements and is outside the scope of this standard. Otherwise, the Radar bit shall be set to 0.
— Unmeasured bit, which shall be set to 1 when this channel has not been measured. Otherwise, the Unmeasured bit shall be set to 0. When the Unmeasured field is set to 1, all the other bit fields shall be set to 0.
7.3.2.22.2 CCA report
A Measurement Type in the Measurement Report element may indicate a CCA report. It is optional for a STA to support the generation of this report. The format of the Measurement Report field corresponding to a CCA report is shown in Figure 7-67.
The Channel Number field shall contain the channel number to which the CCA report applies (as defined in 17.3.8.3.3).
The Measurement Start Time field shall be set to the TSF at the time (± 32 μs) at which the CCA report measurement started.
The Measurement Duration field shall be set to the duration over which the CCA report was measured, expressed in TUs.
The CCA Busy Fraction field shall contain the fractional duration over which CCA indicated the channel was busy during the measurement duration. The resolution of the CCA busy measurement is in microseconds. The CCA Busy Fraction value is defined as Ceiling (255 * [Duration CCA indicated channel was busy (microseconds)] / (1024 * [Measurement duration (TUs)])).
7.3.2.22.3 RPI histogram report
A Measurement Type in the Measurement Report element may indicate an RPI histogram report. It is
optional for a STA to support the generation of this report. The format of the Measurement Report field
corresponding to an RPI histogram report is shown in Figure 7-68.
The Channel Number field shall be set to the channel number to which the RPI histogram report applies (as defined in 17.3.8.3.3).
The Measurement Start Time field shall be set to the TSF at the time (± 32 μs) at which the RPI histogram report measurement started.
The Measurement Duration field shall be set to the duration over which the RPI histogram report was measured, expressed in TUs.
The RPI histogram report shall contain the RPI densities observed in the channel for the eight RPI levels defined in Table 7-31. To compute the RPI densities, the STA shall measure the received power level on the specified channel, as detected at the antenna connector, as a function of time over the measurement duration. The maximum tolerance of the received power measurements shall be ± 5 dB. Furthermore, the received signal power measurement should be a monotonic function of the actual power at the antenna. The time resolution of the received power measurements is in microseconds. The received power measurements are converted to a sequence of RPI values by quantizing the measurements according to Table 7-31. The RPI densities are then computed for each of the eight possible RPI values using Ceiling (255 * [Duration receiving at RPI value (microseconds) / (1024 * Measurement duration)]). The sum of the RPI densities will be approximately 255, but could be up to 262 because of rounding effects.
The RPI histogram report provides an additional mechanism for a STA to gather information on the state of a channel from other STAs. The STA may use this information to assist in the choice of new channel, to help avoid false radar detections, and to assess the general level of interference present on a channel.
7.3.2.23 Quiet element
The Quiet element defines an interval during which no transmission shall occur in the current channel. This interval may be used to assist in making channel measurements without interference from other STAs in the BSS or IBSS. The format of the Quiet element is shown in Figure 7-69.
The Length field shall be set to 6.
The Quiet Count field shall be set to the number of TBTTs until the beacon interval during which the next quiet interval shall start. A value of 1 indicates the quiet interval shall start during the beacon interval starting at the next TBTT. A value of 0 is reserved.
The Quiet Period field shall be set to the number of beacon intervals between the start of regularly scheduled quiet intervals defined by this Quiet element. A value of 0 indicates that no periodic quiet interval is defined.
The Quiet Duration field shall be set to the duration of the quiet interval, expressed in TUs.
The Quiet Offset field shall be set to the offset of the start of the quiet interval from the TBTT specified by the Quiet Count field, expressed in TUs. The value of the Quiet Offset field shall be less than one beacon interval.
The Quiet element may be included in Beacon frames, as described in 7.2.3.1, and Probe Response frames, as described in 7.2.3.9. The use of Quiet elements is described in 11.9.2.
7.3.2.24 IBSS DFS element
The IBSS DFS element contains information for DFS operation in an IBSS. The format of the IBSS DFS element is shown in Figure 7-70.
The Length field is variable.
The DFS Owner field shall be set to the individual IEEE MAC address of the STA that is the currently
known DFS Owner in the IBSS.
The DFS Recovery Interval field indicates the time interval that shall be used for DFS owner recovery, expressed as an integral number of beacon intervals. The DFS Recovery Interval value is static throughout the lifetime of the IBSS and is determined by the STA that starts the IBSS.
The Channel Map field shown in Figure 7-71 shall contain a Channel Number field and a Map field (see 7.3.2.22.1) for each channel supported by the STA transmitting the IBSS DFS element. Note that n in Figure 7-70 is the number of channels supported by the STA.
The IBSS DFS element may be included in Beacon frames, as described in 7.2.3.1, and Probe Response frames, as described in 7.2.3.9. The use of IBSS DFS elements is described in 11.9.7.2.
7.3.2.25 RSN information element
The RSN information element contains authentication and pairwise cipher suite selectors, a single group cipher suite selector, an RSN Capabilities field, the PMK identifier (PMKID) count, and PMKID list. See Figure 7-72. All STAs implementing RSNA shall support this element. The size of the RSN information element is limited by the size of an information element, which is 255 octets. Therefore, the number of pairwise cipher suites, AKM suites, and PMKIDs is limited.
In Figure 7-72, m denotes the pairwise cipher suite count, n the AKM suite count, and s is the PMKID count.
All fields use the bit convention from 7.1.1. The RSN information element shall contain up to and including the Version field. All fields after the Version field are optional. If any optional field is absent, then none of the subsequent fields shall be included.
Element ID shall be 48 decimal (30 hex).
Length gives the number of octets in the information field (field(s) following the Element ID and Length fields) of the information element.
The Version field indicates the version number of the RSNA protocol. The range of Version field values a STA supports shall be contiguous. Values 0 and 2 or higher of the Version field are reserved. RSN Version 1 is defined in this standard.
NOTE—The following represent sample information elements:
802.1X authentication, CCMP pairwise and group cipher suites (WEP-40, WEP-104, and TKIP not allowed):
30, // information element id, 48 expressed as Hex value
14, // length in octets, 20 expressed as Hex value
01 00, // Version 1
00 0F AC 04, // CCMP as group cipher suite
01 00, // pairwise cipher suite count
00 0F AC 04, // CCMP as pairwise cipher suite
01 00, // authentication count
00 0F AC 01 // 802.1X authentication
00 00 // No capabilities
802.1X authentication, CCMP pairwise and group cipher suites (WEP-40, WEP-104 and TKIP not allowed), preauthentication supported:
30, // information element id, 48 expressed as Hex value
14, // length in octets, 20 expressed as Hex value
01 00, // Version 1
00 0F AC 04, // CCMP as group cipher suite
01 00, // pairwise cipher suite count
00 0F AC 04, // CCMP as pairwise cipher suite
01 00, // authentication count
00 0F AC 01 // 802.1X authentication
01 00 // Preauthentication capabilities
802.1X authentication, Use GTK for pairwise cipher suite, WEP-40 group cipher suites, optional RSN Capabilities field omitted:
30, // information element id, 48 expressed as Hex value
12, // length in octets, 18 expressed as Hex value
01 00, // Version 1
00 0F AC 01, // WEP-40 as group cipher suite
01 00, // pairwise cipher suite count
00 0F AC 00, // Use group key as pairwise cipher suite
01 00, // authentication count
00 0F AC 01 // 802.1X authentication
802.1X authentication, Use CCMP for pairwise cipher suite, CCMP group cipher suites, preauthentication and a PMKID:
30, // information element id, 48 expressed as Hex value
26 // length in octets, 38 expressed as Hex value
01 00, // Version 1
00 0F AC 04, // CCMP as group cipher suite
01 00, // pairwise cipher suite count
00 0F AC 04, // CCMP as pairwise cipher suite
01 00, // authentication count
00 0F AC 01 // 802.1X authentication
01 00 // Preauthentication capabilities
01 00 // PMKID Count
01 02 03 04 05 06 07 08 09 0A 0B0C 0D 0E 0F 10 // PMKID
7.3.2.25.1 Cipher suites
The Group Cipher Suite field contains the cipher suite selector used by the BSS to protect broadcast/ multicast traffic.
The Pairwise Cipher Suite Count field indicates the number of pairwise cipher suite selectors that are
contained in the Pairwise Cipher Suite List field.
The Pairwise Cipher Suite List field contains a series of cipher suite selectors that indicate the pairwise cipher suites contained in the RSN information element.
The order of the organizationally unique indentifier (OUI) field shall follow the ordering convention for
MAC addresses from 7.1.1.
Table 7-32 provides the cipher suite selectors defined by this standard.
The cipher suite selector 00-0F-AC:4 (CCMP) shall be the default cipher suite value.
The cipher suite selectors 00-0F-AC:1 (WEP-40) and 00-0F-AC:5 (WEP-104) are only valid as a group cipher suite in a transition security network (TSN) to allow pre-RSNA devices to join the BSS.
Use of CCMP as the group cipher suite with TKIP as the pairwise cipher suite shall not be supported. NOTE—If the STAs can support CCMP, then there is no need for a weaker data confidentiality protocol. The cipher suite selector 00-0F-AC:0 (Use group cipher suite) is only valid as the pairwise cipher suite. An AP may specify the selector 00-0F-AC:0 (Use group cipher suite) for a pairwise cipher suite if it does not support any pairwise cipher suites. If an AP specifies 00-0F-AC:0 (Use group cipher suite) as the pairwise cipher selection, this shall be the only pairwise cipher selection the AP advertises.
If CCMP is enabled, then the AP supports pairwise keys, and thus the suite selector 00-0F-AC:0 (Use group cipher suite) shall not be a valid option.
Table 7-33 indicates the circumstances under which each cipher suite shall be used.
7.3.2.25.2 AKM suites
The AKM Suite Count field indicates the number of AKM suite selectors that are contained in the AKM
Suite List field.
The AKM Suite List field contains a series of AKM suite selectors contained in the RSN information element. In an IBSS, only a single AKM suite selector may be specified because STAs in an IBSS must use the same AKM suite and because there is no mechanism to negotiate the AKMP in an IBSS (see 8.4.4).
Each AKM suite selector specifies an AKMP. Table 7-34 gives the AKM suite selectors defined by this
standard.
The AKM suite selector value 00-0F-AC:1 (Authentication negotiated over IEEE 802.1X) with (RSNA key management as defined in 8.5 or using PMKSA caching as defined in 8.4.6.2) shall be the assumed default when the AKM suite selector field is not supplied.
NOTE—The selector value 00-0F-AC:1 specifies only that IEEE Std 802.1X-2004 is used as the authentication transport. IEEE Std 802.1X-2004 selects the authentication mechanism.
The AKM suite selector value 00-0F-AC:2 (PSK) is used when a PSK is used with RSNA key management.
NOTE—Selector values 00-0F-AC:1 and 00-0F-AC:2 can simultaneously be enabled by an Authenticator.
7.3.2.25.3 RSN capabilities
The RSN Capabilities field indicates requested or advertised capabilities. The value of each of the RSN Capabilities fields shall be taken to be 0 if the RSN Capabilities field is not available in the RSN information element.
The length of the RSN Capabilities field is 2 octets. The format of the RSN Capabilities field is as illustrated in Figure 7-74 and described after the figure.
— Bit 0: Pre-Authentication. An AP sets the Pre-Authentication subfield of the RSN Capabilities field to 1 to signal it supports preauthentication (see 8.4.6.1) and sets the subfield to 0 when it does not support preauthentication. A non-AP STA sets the Pre-Authentication subfield to 0.
— Bit 1: No Pairwise. If a STA can support WEP default key 0 simultaneously with a pairwise key (see 8.5.1), then the STA sets the No Pairwise subfield of the RSN Capabilities field to 0. If a STA cannot support WEP default key 0 simultaneously with a pairwise key (see 8.5.1), then the STA sets the No Pairwise subfield of the RSN Capabilities field to 1.
The No Pairwise subfield describes a capability of a non-AP STA. STAs in an IBSS and APs set the
No Pairwise subfield to 0. The No Pairwise subfield shall be set only in a TSN and when the pairwise cipher suite selected by the STA is TKIP.
— Bits 2–3: PTKSA Replay Counter. A STA sets the PTKSA Replay Counter subfield of the RSN Capabilities field to the value contained in dot11RSNAConfigNumberofPTKSAReplayCounters. The least significant bit (LSB) of dot11RSNAConfigNumberofPTKSAReplayCounters is put in bit 2. See 8.3.2.6 and 8.3.3.4.3. The meaning of the value in the PTKSA/GTKSA/STKSA Replay Counter subfield is defined in Table 7-35. The number of replay counters per STKSA is the same as the number of replay counters per PTKSA.
— Bits 4–5: GTKSA Replay Counter. A STA sets the GTKSA Replay Counter subfield of the RSN Capabilities field to the value contained in dot11RSNAConfigNumberofPTKSAReplayCounters. The LSB of dot11RSNAConfigNumberofGTKSAReplayCounters is put in bit 4. See 8.3.2.6 and 8.3.3.4.3. The meaning of the value in the GTKSA Replay Counter subfield is defined in Table 7-35.
— Bits 9: PeerKey Enabled. An AP STA sets the PeerKey Enabled subfield of the RSN Capabilities field to 1 to signal it supports PeerKey Handshake (see 8.5.8). This field is used by AP STA to describe its ability to support PeerKey Handshake.
— Bits 6–8 and 10–15: Reserved. The remaining subfields of the RSN Capabilities field are reserved and shall be set to 0 on transmission and ignored on reception.
7.3.2.25.4 PMKID
The PMKID Count and List fields shall be used only in the RSN information element in the (Re)Association Request frame to an AP. The PMKID Count specifies the number of PMKIDs in the PMKID List field. The PMKID list contains 0 or more PMKIDs that the STA believes to be valid for the destination AP. The PMKID can refer to
a) A cached PMKSA that has been obtained through preauthentication with the target AP
b) A cached PMKSA from an EAP authentication
c) A PMKSA derived from a PSK for the target AP
See 8.5.1.2 for the construction of the PMKID.
NOTE—A STA can choose not to insert a PMKID in the PMKID List field if the STA does not want to use that PMKSA.
7.3.2.26 Vendor Specific information element
The Vendor Specific information element is used to carry information not defined in this standard within a single defined format, so that reserved information element IDs are not usurped for nonstandard purposes and so that interoperability is more easily achieved in the presence of nonstandard information. The information element is in the format shown in Figure 7-75 and requires that the first 3 octets of the information field contain the OUI of the entity that has defined the content of the particular Vendor Specific information element. The length of the information field (n) is 3 ≤ n ≤ 255. The OUI field shall be a public OUI assigned by the IEEE. It is 3 octets in length. The length of the vendor-specific content is n–3 octets.
Multiple Vendor Specific information elements may appear in a single frame. Each Vendor Specific information element can have a different OUI value. The number of Vendor Specific information elements that may appear in a frame is limited only by the maximum frame size.
7.3.2.27 Extended Capabilities information element
The Extended Capabilities information element carries information about the capabilities of an IEEE 802.11 STA, intended to augment the Capability Information field (CIF) when these bits are fully allocated. The format of this information element is shown in Figure 7-76.
The element ID of this information element is 127.
The value of the Length field is equal to the number of octets in the Capabilities field.
The Capabilities field is a bit field indicating the capabilities being advertised by the STA transmitting the information element. There are no capabilities defined for this field in this revision of the standard.
7.3.2.28 BSS Load element
The BSS Load element contains information on the current STA population and traffic levels in the BSS. The element information format is defined in Figure 7-77. This element may be used by the non-AP STA for vendor-specific AP selection algorithm when roaming.
The STA Count field is interpreted as an unsigned integer that indicates the total number of STAs currently associated with this BSS.
The Channel Utilization field is defined as the percentage of time, normalized to 255, the AP sensed the medium was busy, as indicated by either the physical or virtual carrier sense (CS) mechanism. This percentage is computed using the formula,
((channel busy time/(dot11ChannelUtilizationBeaconIntervals * dot11BeaconPeriod * 1024)) * 255),
where channel busy time is defined to be the number of microseconds during which the CS mechanism, as defined in 9.2.1, has indicated a channel busy indication, and the MIB attribute dot11ChannelUtilization- BeaconIntervals represents the number of consecutive beacon intervals during which the channel busy time is measured. The default value of dot11 Channel Utilization Beacon Intervals is defined in Annex D.
The Available Admission Capacity field is 2 octets long and contains an unsigned integer that specifies the remaining amount of medium time available via explicit admission control, in units of 32 μs/s. The field is helpful for roaming non-AP STAs to select an AP that is likely to accept future admission control requests, but it does not represent a guarantee that the HC will admit these requests.
7.3.2.29 EDCA Parameter Set element
The EDCA Parameter Set element provides information needed by non-AP STAs for proper operation of the QoS facility during the CP. The format of the EDCA Parameter Set element is defined in Figure 7-78.
The EDCA Parameter Set element is used by the AP to establish policy (by changing default MIB attribute values), to change policies when accepting new STAs or new traffic, or to adapt to changes in offered load. The most recent EDCA parameter set element received by a non-AP STA is used to update the appropriate MIB values.
The format of the QoS Info field is defined in 7.3.1.17. The QoS Info field contains the EDCA Parameter Set Update Count subfield, which is initially set to 0 and is incremented each time any of the AC parameters changes. This subfield is used by non-AP STAs to determine whether the EDCA parameter set has changed and requires updating the appropriate MIB attributes.
The formats of AC_BE, AC_BK, AC_VI, and AC_VO Parameter Record fields are identical and are
illustrated in Figure 7-79.
Figure 7-79—AC_BE, AC_BK, AC_VI, and AC_VO Parameter Record field format
The format of the ACI/AIFSN field is illustrated in Figure 7-80.
The value of the AC index (ACI) references the AC to which all parameters in this record correspond. The mapping between ACI and AC is defined in Table 7-36. The ACM (admission control mandatory) subfield indicates that admission control is required for the AC. If the ACM subfield is set to 0, then there is no admission control for the corresponding AC. If the ACM subfield is set to 1, admission control has to be used prior to transmission using the access parameters specified for this AC. The AIFSN subfield indicates the number of slots after a SIFS duration a non-AP STA should defer before either invoking a backoff or starting a transmission. The minimum value for the AIFSN subfield is 2.
The ECWmin and ECWmax fields are illustrated in Figure 7-81.
The ECWmin and ECWmax fields encode the values of CWmin and CWmax, respectively, in an exponent form. The ECWmin and ECWmax values are defined so that
CWmin = 2ECWmin – 1
CWmax = 2ECWmax – 1
Hence the minimum encoded value of CWmin and CWmax is 0, and the maximum value is 32 767.
The value of the TXOP Limit field is specified as an unsigned integer, with the least significant octet transmitted first, in units of 32 μs. A TXOP Limit field value of 0 indicates that a single MSDU or MMPDU, in addition to a possible RTS/CTS exchange or CTS to itself, may be transmitted at any rate for each TXOP.
The default values used by non-AP STAs for the parameters in the EDCA Parameter Set element are defined in Table 7-37.19
19The default values for TXOP limit are expressed in milliseconds and are multiples of 32 μs.
7.3.2.30 TSPEC element
The TSPEC element contains the set of parameters that define the characteristics and QoS expectations of a traffic flow, in the context of a particular non-AP STA, for use by the HC and non-AP STA(s) in support of QoS traffic transfer using the procedures defined in 11.4. The element information format comprises the items as defined in this subclause, and the structure is defined in Figure 7-82.
The TSPEC allows a set of parameters more extensive than may be needed, or may be available, for any particular instance of parameterized QoS traffic. Unless indicated otherwise, fields that follow the TS Info field are set to 0 for any unspecified parameter values. Non-AP STAs set the value of any parameters to unspecified if they have no information for setting that parameter. The HC may change the value of parameters that have been set unspecified by the STA to any value that it deems appropriate, including leaving them unspecified.
The structure of the TS Info field is defined in Figure 7-83.
— The Traffic Type subfield is a single bit and is set to 1 for a periodic traffic pattern (e.g., isochronous TS of MSDUs, with constant or variable sizes, that are originated at fixed rate) or set to 0 for an aperiodic, or unspecified, traffic pattern (e.g., asynchronous TS of low-duty cycles).
— The TSID subfield is 4 bits in length and contains a value that is a TSID. Note that the MSB (bit 4 in TS Info field) of the TSID subfield is always set to 1. The combination of the TSID and Direction subfields identify the TS, in the context of the non-AP STA, to which the TSPEC applies. The same TSID may be used for multiple TSs at different non-AP STAs. A non-AP STA may use the TSID subfield value for a downlink TSPEC and either an uplink or a direct-link TSPEC at the same time. A non-AP STA shall not use the same TSID for both uplink and direct-link TS. A bidirectional link request is equivalent to a downlink TS and an uplink TS, each with the same TSID and parameters.
— The Direction subfield specifies the direction of data carried by the TS as defined in Table 7-38.
— The Access Policy subfield is 2 bits in length, specifies the access that would be used for the TS, and is defined in Table 7-39.
— The Aggregation subfield is 1 bit in length. The Aggregation subfield is valid only when access method is HCCA or when the access method is EDCA and the Schedule subfield is set to 1. It is set to 1 by a non-AP STA to indicate that an aggregate schedule is required. It is set to 1 by the AP if an aggregate schedule is being provided to the non-AP STA. It is set to 0 otherwise. In all other cases, the Aggregation subfield is reserved.
— The APSD subfield is a single bit and is set to 1 to indicate that automatic PS delivery is to be used for the traffic associated with the TSPEC and set to 0 otherwise.
— The UP subfield is 3 bits and indicates the actual value of the UP to be used for the transport of MSDUs belonging to this TS in cases where relative prioritization is required. When the TCLAS element is present in the request, the UP subfield in TS Info field of the TSPEC element is reserved.
— The TS Info Ack Policy subfield is 2 bits in length and indicates whether MAC acknowledgments are required for MPDUs belonging to this TID and the desired form of those acknowledgments. The encoding of the TS Info Ack Policy subfield is shown in Table 7-40. If the TS Info Ack Policy subfield is set to Block Ack and the type of Block Ack policy is unknown to the HC, the HC shall assume, for TXOP scheduling, that the immediate Block Ack policy is being used (see 9.10).
— The Schedule subfield is 1 bit in length and specifies the requested type of schedule. The setting of the subfield when the access policy is EDCA is shown in Table 7-41. When the Access Policy
subfield is set to any value other than EDCA, the Schedule subfield is reserved. When the Schedule
and APSD subfields are set to 1, the AP shall set the aggregation bit to 1, indicating that an
aggregate schedule is being provided to the non-AP STA.
The configuration of APSD=0, Schedule=1 is reserved.
The Nominal MSDU Size field is 2 octets long, contains an unsigned integer that specifies the nominal size, in octets, of MSDUs belonging to the TS under this TSPEC, and is defined in Figure 7-84. If the Fixed subfield is set to 1, then the size of the MSDU is fixed and is indicated by the Size subfield. If the Fixed subfield is set to 0, then the size of the MSDU might not be fixed and the Size subfield indicates the nominal MSDU size. If both the Fixed and Size subfields are set to 0, then the nominal MSDU size is unspecified.
The Maximum MSDU Size field is 2 octets long and contains an unsigned integer that specifies the maximum size, in octets, of MSDUs belonging to the TS under this TSPEC.
The Minimum Service Interval field is 4 octets long and contains an unsigned integer that specifies the minimum interval, in microseconds, between the start of two successive SPs.
The Maximum Service Interval field is 4 octets long and contains an unsigned integer that specifies the maximum interval, in microseconds, between the start of two successive SPs.
The Inactivity Interval field is 4 octets long and contains an unsigned integer that specifies the minimum amount of time, in microseconds, that may elapse without arrival or transfer of an MPDU belonging to the TS before this TS is deleted by the MAC entity at the HC.
The Suspension Interval field is 4 octets long and contains an unsigned integer that specifies the minimum amount of time, in microseconds, that may elapse without arrival or transfer of an MSDU belonging to the TS before the generation of successive QoS(+)CF-Poll is stopped for this TS. A value of 4 294 967 295 (= 232 – 1) disables the suspension interval, indicating that polling for the TS is not to be interrupted based on inactivity. The value of the suspension interval is always less than or equal to the inactivity interval.
The Service Start Time field is 4 octets and contains an unsigned integer that specifies the time, expressed in microseconds, when the first scheduled SP starts. The service start time indicates to AP the time when a non-AP STA first expects to be ready to send frames and a power-saving non-AP STA will be awake to receive frames. This may help the AP to schedule service so that the MSDUs encounter small delays in the MAC and help the power-saving non-AP STAs to reduce power consumption. The field represents the four lower order octets of the TSF timer at the start of the SP. If APSD subfield is set to 0, this field is also set to 0 (unspecified).
The Minimum Data Rate field is 4 octets long and contains an unsigned integer that specifies the lowest data rate specified at the MAC_SAP, in bits per second, for transport of MSDUs belonging to this TS within the bounds of this TSPEC. The minimum data rate does not include the MAC and PHY overheads incurred in transferring the MSDUs.
The Mean Data Rate20 field is 4 octets long and contains an unsigned integer that specifies the average data rate specified at the MAC_SAP, in bits per second, for transport of MSDUs belonging to this TS within the bounds of this TSPEC. The mean data rate does not include the MAC and PHY overheads incurred in transferring the MSDUs.
The Peak Data Rate field is 4 octets long and contains an unsigned integer that specifies the maximum allowable data rate, in bits per second, for transfer of MSDUs belonging to this TS within the bounds of this TSPEC. If p is the peak rate in bits per second, then the maximum amount of data, belonging to this TS, arriving in any time interval [t1,t2], where t1 < t2 and t2 – t1 > 1 TU, does not exceed p * (t2 – t1) bits.
The Burst Size field is 4 octets long and contains an unsigned integer that specifies the maximum burst, in octets, of the MSDUs belonging to this TS that arrive at the MAC_SAP at the peak data rate. A value of 0 indicates that there are no bursts.
The Delay Bound field is 4 octets long and contains an unsigned integer that specifies the maximum amount of time, in microseconds, allowed to transport an MSDU belonging to the TS in this TSPEC, measured between the time marking the arrival of the MSDU at the local MAC sublayer from the local MAC_SAP and the time of completion of the successful transmission or retransmission of the MSDU to the destination. The completion of the MSDU transmission includes the relevant acknowledgment frame transmission time, if present.
The Minimum PHY Rate field is 4 octets long and contains an unsigned integer that specifies the desired minimum PHY rate to use for this TS, in bits per second, that is required for transport of the MSDUs belonging to the TS in this TSPEC.21
The Surplus Bandwidth Allowance field is 2 octets long and specifies the excess allocation of time (and bandwidth) over and above the stated application rates required to transport an MSDU belonging to the TS in this TSPEC. This field is represented as an unsigned binary number and, when specified, is greater than 0. The 13 least significant bits (LSBs) indicate the decimal part while the three MSBs indicate the integer part of the number. This field takes into account the retransmissions, as the rate information does not include retransmissions. It represents the ratio of over-the-air bandwidth (i.e., time that the scheduler allocates for the transmission of MSDUs at the required rates) to bandwidth of the transported MSDUs required for successful transmission (i.e., time that would be necessary at the minimum PHY rate if there were no errors on the channel) to meet throughput and delay bounds under this TSPEC, when specified. As such, it should be greater than unity. A value of 1 indicates that no additional allocation of time is requested.
20The mean data rate, the peak data rate, and the burst size are the parameters of the token bucket model, which provides standard terminology for describing the behavior of a traffic source. The token bucket model is described in IETF RFC 2212-1997 [B19], IETF RFC 2215-1997 [B20], and IETF RFC 3290-2002 [B24].
21This rate information is intended to ensure that the TSPEC parameter values resulting from an admission control negotiation are sufficient to provide the required throughput for the TS. In a typical implementation, a TS is admitted only if the defined traffic volume can be accommodated at the specified rate within an amount of WM occupancy time that the admissions control entity is willing to
allocate to this TS.
The Medium Time field is a 16-bit unsigned integer and contains the amount of time admitted to access the medium, in units of 32 μs/s. This field is reserved in the ADDTS Request frame and is set by the HC in the ADDTS Response frame. The derivation of this field is described in K.2.2. This field is not used for controlled channel access.
The UP, Minimum Data Rate, Mean Data Rate, Peak Data Rate, Burst Size, Minimum PHY Rate, and Delay Bound fields in a TSPEC element express the QoS expectations requested by a non-AP STA, if this TSPEC was issued by that non-AP STA, or provided by the HC, if this TSPEC was issued by the HC, when these fields are specified with nonzero values. Unspecified parameters in these fields as indicated by a zero value indicate that the non-AP STA does not have specific requirements for these parameters if the TSPEC was issued by that non-AP STA or that the HC does not provide any specific values for these parameters if the TSPEC was issued by the HC.
7.3.2.31 TCLAS element
The TCLAS element specifies an information element that contains a set of parameters necessary to identify incoming MSDUs (from a higher layer in all STAs or from the DS in an AP) with a particular TS to which they belong. If required, the TCLAS element is provided in ADDTS Request and ADDTS Response frames only for the downlink or bidirectional links. TCLAS element need not be provided for the uplink or directlink transmissions. The structure of this element is shown in Figure 7-85.
The UP field contains the value of the UP of the associated MSDUs. The Frame Classifier field is 3–255 octets in length and is defined in Figure 7-86.
The Frame Classifier field comprises the following subfields: Classifier Type, Classifier Mask, and Classifier Parameters. The Classifier Type subfield is 1 octet in length and specifies the type of classifier parameters in this TCLAS as defined in Table 7-42. Three classifier types are defined later in this subclause.
The Classifier Mask subfield specifies a bitmap where bits that are set to 1 identify a subset of the classifier parameters whose values must match those of the corresponding parameters in a given MSDU for that MSDU to be classified to the TS of the affiliated TSPEC. The bitmap is ordered from the LSB to the MSB, with each bit pointing to one of the classifier parameters of the same relative position as shown in this subclause based on classifier type. An incoming MSDU that failed to be classified to a particular TS may be classified to another active TS based on the frame classifier for that TS. If, however, all the frame classifiers for the active TS have been exhausted, the MSDU does not belong to any active TS and is classified to be a best-effort MSDU. In cases where there are more bits in the bitmap than classifier parameters that follow, the MSBs that do not point to any classifier parameters are reserved.
For Classifier Type 0, the classifier parameters are the following parameters contained in an Ethernet packet header: Source Address, Destination Address, and Type (“Ethernet” [B5]). The Frame Classifier field for Classifier Type 0 is defined in Figure 7-87. It has a length of 16 octets.
For Classifier Type 1, frame classifier is defined for both IPv4 and IPv6, shown in Figure 7-88 and Figure 789, and distinguished by the Version field. The subfields in the classifier parameters are represented and transmitted in the big-endian format. The classifier parameters are the following parameters:
— In a TCP or UDP header: Source Address, Destination Address, Source Port, Destination Port, and Version, plus
— One of the following:
— In an IPv4 header: Differentiated Services Code Point (DSCP) (IETF RFC 2474-1998 [B21]) and Protocol, or
— In an IPv6 header: Flow Label.
The DSCP field shall contain the value in the 6 LSBs, and the 2 MSBs are set to 0. The 2 MSBs of the DSCP field are ignored for frame classification.
For Classifier Type 2, the Classifier Parameters are the following parameters in an IEEE 802.1Q tag header: IEEE 802.1D user priority and IEEE 802.1Q VLAN ID (see IEEE Std 802.1Q, 2003 Edition, [B14]). The Frame Classifier field for Classifier Type 2 is defined in Figure 7-90.
7.3.2.32 TS Delay element
The TS Delay element is used in the ADDTS Response frame transmitted by the HC to a non-AP STA and indicates the time after which the ADDTS may be retried. The TS Delay element is defined in Figure 7-91.
The Delay field is 4 octets long and specifies the amount of time, in TUs, a non-AP STA should wait before it reinitiates setup of a TS.
The TS Delay element is set to 0 when an AP does not want to serve any TSPECs for an indeterminate time and it does not know this time a priori.
7.3.2.33 TCLAS Processing element
The TCLAS Processing element is present in the ADDTS Request and Response frames if there are multiple TCLASs associated with the request. It indicates how an MSDU received from higher layers should be processed by the classifier. The TCLAS Processing element is defined in Figure 7-92.
The Processing subfield is 1 octet long. The encoding of the Processing subfield is shown in Table 7-43.
Table 7-43—Encoding of Processing subfield
7.3.2.34 Schedule element
The Schedule element is transmitted by the HC to a non-AP STA to announce the schedule that the HC/AP follows for admitted streams originating from or destined to that non-AP STA in the future. The information in this element may be used by the non-AP STA for power management, internal scheduling, or any other purpose. The element information format is shown in Figure 7-93.
The Schedule Info field is shown in Figure 7-94.
The Aggregation subfield is set to 1 if the schedule is an aggregate schedule for all TSIDs associated with the non-AP STA to which the frame is directed. It is set to 0 otherwise. The TSID subfield is as defined in 7.1.3.5.1 and indicates the TSID for which this schedule applies. The Direction subfield is as defined in 7.3.2.30 and defines the direction of the TSPEC associated with the schedule. The TSID and Direction subfields are valid only when the Aggregation subfield is set to 0. If the Aggregation subfield is set to 1, the TSID and Direction subfields are reserved.
The Service Start Time field is 4 octets and indicates the anticipated time, expressed in microseconds, when service starts and represents the lower order 4 octets of the TSF timer value at the start of the first SP. The AP uses this field to confirm or modify the service start time indicated in the TSPEC request.
The Service Interval field is 4 octets and indicates the time, expressed in microseconds, between two
successive SPs and represents the measured time from the start of one SP to the start of the next SP.
The Specification Interval field is 2 octets long and contains an unsigned integer that specifies the time interval, in TUs, to verify schedule conformance.
The HC may set the Service Start Time field and the Service Interval field to 0 (unspecified) for nonpowersaving STAs.
7.3.2.35 QoS Capability element
The QoS Capability element contains a number of subfields that are used to advertise optional QoS capabilities at a QoS STA. The QoS Capability element is present in Beacon frames that do not contain the EDCA Parameter Set element and in (Re)Association Request frames. The QoS Capability element is defined in Figure 7-95.
