WiFi

 

 

 

 

Beacon

 

Beacon is a special type of signal (message) being broadast periodically from an AP (Access Point) which carries its ID and capability to every devices placed around the AP. The overall frame structure of Beacon is as follows.

 

 

Following is an example showing the Beacon Frame Header part

    IEEE 802.11 Beacon frame, Flags: ..m.....C

        Type/Subtype: Beacon frame (0x08)

        Frame Control Field: 0x8020

            .... ..00 = Version: 0

            .... 00.. = Type: Management frame (0)

            1000 .... = Subtype: 8

            Flags: 0x20

                .... ..00 = DS status: Not leaving DS or network is operating in AD-HOC mode

                            (To DS: 0 From DS: 0) (0x00)

                            // (To DS: 0 From DS: 0) mean the address 1 is Destination address

                             // the address 2 is Source address

                .... .0.. = More Fragments: This is the last fragment

                .... 0... = Retry: Frame is not being retransmitted

                ...0 .... = PWR MGT: STA will stay up

                ..1. .... = More Data: Data is buffered for STA at AP

                .0.. .... = Protected flag: Data is not protected

                0... .... = Order flag: Not strictly ordered

        .000 0000 0000 0000 = Duration: 0 microseconds

        Receiver address: Broadcast (ff:ff:ff:ff:ff:ff)

        Destination address: Broadcast (ff:ff:ff:ff:ff:ff)

        Transmitter address: Anritsu_07:91:0e (00:00:91:07:91:0e)

        Source address: Anritsu_07:91:0e (00:00:91:07:91:0e)

        BSS Id: Anritsu_07:91:0e (00:00:91:07:91:0e)

        Fragment number: 0

        Sequence number: 78

        Frame check sequence: 0xe0fbec2b [correct]

            [Good: True]

            [Bad: False]

 

 

Following is the list of information broadcast carried in [Frame Body] of a Beacon signal. Not all of these information are broadcast by an AP. Many of these fields are broadcast only in a specific condition (you can find the further details in 802.11 - 8.3.3.2 Beacon frame format).

 

Order

Information

Description

1

Time Stamp  

2

Beacon Interval  

3

Capability Information  

4

SSID  

5

Supported Rates  

6

FH (Frequency Hopping) Parameter Set  

7

DS (Direct Sequence) Parameter Set  

8

CF (Contention Free) Parameter Set  

9

IBSS Parameter Set  

10

TIM(Traffic Indication Map)  

11

Country  

12

FH Parameters

 

13

FH Pattern Table

 

14

Power Constraint

 

15

Channel Switch Announcement

 

16

Quiet  

17

IBSS DFS

 

18

TPC Report

 

19

ERP  

20

Extended Supported Rates

 

21

RSN  

22

BSS Load

 

23

EDCA Parameter Set

 

24

QoS Capability

 

25

AP Channel Report

 

26

BSS Average Access Delay

 

27

Antenna

 

28

BSS Available Admission Capacity

 

29

BSS AC Access Delay

 

30

Measurement Pilot Transmission

 

31

Multiple BSSID

 

32

RM Enabled Capabilities

 

33

Mobility Domain

 

34

DSE registered location

 

35

Extended Channel Switch Announcement

 

36

Supported Operating Classes

 

37

HT Capabilities

 

38

HT Operation

 

39

20/40 BSS Coexistence

 

40

Overlapping BSS Scan Parameters

 

41

Extended Capabilities

 

42

FMS Descriptor

 

43

QoS Traffic Capability

 

44

Time Advertisement

 

45

Interworking

 

46

Advertisement Protocol

 

47

Roaming Consortium

 

48

Emergency Alert Identifier

 

49

Mesh ID

 

50

Mesh Configuration

 

51

Mesh Awake Window

 

52

Beacon Timing

 

53

MCCAOP Advertisement Overview

 

54

MCCAOP Advertisement

 

55

Mesh Channel Switch Parameters

 

Last

Vendor Specific

 

 

Followings are examples of Beacon Frame contents.

 

< Example 1 >

 

Following is an example from an old 802.11 specification, you would see relatively small set of informations included in the beacon. Compare this example with the next example which came from the latest specficiation (802.11ac) and how the feature set grows.

 

 

 

< Example 2 >

 

This is an example from the experimental AP(Access Point) called Anritsu MT8862 that support 802.11ac. The log is captured in a test setup shown here. Unless you get the full understanding of 802.11 PHY/MAC specification, it would be difficult to understand the meaning of all the parameters shown here. But if you go through all of the items here a couple of times even though you don't understand what it means. It will be helpful for you to read other technical material or specification related to 802.11. (The first step to learn any new things is to get used to it even though you don't understand the full details)

 

IEEE 802.11 Beacon frame, Flags: ..m.....C

    Type/Subtype: Beacon frame (0x08)

    Frame Control Field: 0x8020

        .... ..00 = Version: 0

        .... 00.. = Type: Management frame (0)

        1000 .... = Subtype: 8

        Flags: 0x20

            .... ..00 = DS status: Not leaving DS or network is operating in AD-HOC mode

                        (To DS: 0 From DS: 0) (0x00)

            .... .0.. = More Fragments: This is the last fragment

            .... 0... = Retry: Frame is not being retransmitted

            ...0 .... = PWR MGT: STA will stay up

            ..1. .... = More Data: Data is buffered for STA at AP

            .0.. .... = Protected flag: Data is not protected

            0... .... = Order flag: Not strictly ordered

    .000 0000 0000 0000 = Duration: 0 microseconds

    Receiver address: Broadcast (ff:ff:ff:ff:ff:ff)

    Destination address: Broadcast (ff:ff:ff:ff:ff:ff)

    Transmitter address: Anritsu_07:91:0e (00:00:91:07:91:0e)

    Source address: Anritsu_07:91:0e (00:00:91:07:91:0e)

    BSS Id: Anritsu_07:91:0e (00:00:91:07:91:0e)

    Fragment number: 0

    Sequence number: 78

    Frame check sequence: 0xe0fbec2b [correct]

        [Good: True]

        [Bad: False]

IEEE 802.11 wireless LAN management frame

    Fixed parameters (12 bytes)

        Timestamp: 0x0000000000f3c041

        Beacon Interval: 0.204800 [Seconds]

        Capabilities Information: 0x0001

            .... .... .... ...1 = ESS capabilities: Transmitter is an AP

            .... .... .... ..0. = IBSS status: Transmitter belongs to a BSS

            .... ..0. .... 00.. = CFP participation capabilities:

                                      No point coordinator at AP (0x0000)

            .... .... ...0 .... = Privacy: AP/STA cannot support WEP

            .... .... ..0. .... = Short Preamble: Not Allowed

            .... .... .0.. .... = PBCC: Not Allowed

            .... .... 0... .... = Channel Agility: Not in use

            .... ...0 .... .... = Spectrum Management: Not Implemented

            .... .0.. .... .... = Short Slot Time: Not in use

            .... 0... .... .... = Automatic Power Save Delivery: Not Implemented

            ...0 .... .... .... = Radio Measurement: Not Implemented

            ..0. .... .... .... = DSSS-OFDM: Not Allowed

            .0.. .... .... .... = Delayed Block Ack: Not Implemented

            0... .... .... .... = Immediate Block Ack: Not Implemented

    Tagged parameters (134 bytes)

        Tag: SSID parameter set: MT8862A6000000008

            Tag Number: SSID parameter set (0)

            Tag length: 17

            SSID: MT8862A6000000008

        Tag: Supported Rates 6(B), 9, 12(B), 18, 24(B), 36, 48, 54, [Mbit/sec]

            Tag Number: Supported Rates (1)

            Tag length: 8

            Supported Rates: 6(B) (0x8c)

            Supported Rates: 9 (0x12)

            Supported Rates: 12(B) (0x98)

            Supported Rates: 18 (0x24)

            Supported Rates: 24(B) (0xb0)

            Supported Rates: 36 (0x48)

            Supported Rates: 48 (0x60)

            Supported Rates: 54 (0x6c)

        Tag: Traffic Indication Map (TIM): DTIM 0 of 0 bitmap

            Tag Number: Traffic Indication Map (TIM) (5)

            Tag length: 4

            DTIM count: 0

            DTIM period: 1

            Bitmap control: 0x00

                .... ...0 = Multicast: False

                0000 000. = Bitmap Offset: 0x00

            Partial Virtual Bitmap: 00

        Tag: HT Capabilities (802.11n D1.10)

            Tag Number: HT Capabilities (802.11n D1.10) (45)

            Tag length: 26

            HT Capabilities Info: 0x007e

                .... .... .... ...0 = HT LDPC coding capability:

                                      Transmitter does not support receiving LDPC coded packets

                .... .... .... ..1. = HT Support channel width:

                                      Transmitter supports 20MHz and 40MHz operation

                .... .... .... 11.. = HT SM Power Save: SM Power Save disabled (0x0003)

                .... .... ...1 .... = HT Green Field: Transmitter is able to receive PPDUs

                                      with Green Field (GF) preamble

                .... .... ..1. .... = HT Short GI for 20MHz: Supported

                .... .... .1.. .... = HT Short GI for 40MHz: Supported

                .... .... 0... .... = HT Tx STBC: Not supported

                .... ..00 .... .... = HT Rx STBC: No Rx STBC support (0x0000)

                .... .0.. .... .... = HT Delayed Block ACK:

                                      Transmitter does not support HT-Delayed BlockAck

                .... 0... .... .... = HT Max A-MSDU length: 3839 bytes

                ...0 .... .... .... = HT DSSS/CCK mode in 40MHz:

                                      Won't/Can't use of DSSS/CCK in 40 MHz

                ..0. .... .... .... = HT PSMP Support: Won't/Can't support PSMP operation

                .0.. .... .... .... = HT Forty MHz Intolerant: Use of 40 MHz transmissions

                                      unrestricted/allowed

                0... .... .... .... = HT L-SIG TXOP Protection support: Not supported

            A-MPDU Parameters: 0x1f

                .... ..11 = Maximum Rx A-MPDU Length: 0x03 (65535[Bytes])

                ...1 11.. = MPDU Density: 16 [usec] (0x07)

                000. .... = Reserved: 0x00

            Rx Supported Modulation and Coding Scheme Set: MCS Set

                Rx Modulation and Coding Scheme (One bit per modulation): 1 spatial stream

                    .... .... .... .... .... .... 1111 1111 = Rx Bitmask Bits 0-7: 0x000000ff

                    .... .... .... .... 0000 0000 .... .... = Rx Bitmask Bits 8-15: 0x00000000

                    .... .... 0000 0000 .... .... .... .... = Rx Bitmask Bits 16-23: 0x00000000

                    0000 0000 .... .... .... .... .... .... = Rx Bitmask Bits 24-31: 0x00000000

                    .... .... .... .... .... .... .... ...0 = Rx Bitmask Bit 32: 0x00000000

                    .... .... .... .... .... .... .000 000. = Rx Bitmask Bits 33-38: 0x00000000

                    .... .... ...0 0000 0000 0000 0... .... = Rx Bitmask Bits 39-52: 0x00000000

                    ...0 0000 0000 0000 0000 0000 000. .... = Rx Bitmask Bits 53-76: 0x00000000

                .... ..00 0000 0000 = Highest Supported Data Rate: 0x0000

                .... .... .... ...0 = Tx Supported MCS Set: Not Defined

                .... .... .... ..0. = Tx and Rx MCS Set: Equal

                .... .... .... 00.. = Maximum Number of Tx Spatial Streams Supported: 0x0000,

                                      TX MCS Set Not Defined

                .... .... ...0 .... = Unequal Modulation: Not supported

            HT Extended Capabilities: 0x0006

                .... .... .... ...0 = Transmitter supports PCO: Not supported

                .... .... .... .11. = Time needed to transition between 20MHz and 40MHz:

                                      5 msec (0x0003)

                .... ..00 .... .... = MCS Feedback capability:

                                      STA does not provide MCS feedback (0x0000)

                .... .0.. .... .... = High Throughput: Not supported

                .... 0... .... .... = Reverse Direction Responder: Not supported

            Transmit Beam Forming (TxBF) Capabilities: 0x0000

                .... .... .... .... .... .... .... ...0 = Transmit Beamforming: Not supported

                .... .... .... .... .... .... .... ..0. = Receive Staggered Sounding:

                                                          Not supported

                .... .... .... .... .... .... .... .0.. = Transmit Staggered Sounding:

                                                          Not supported

                .... .... .... .... .... .... .... 0... = Receive Null Data packet (NDP):

                                                          Not supported

                .... .... .... .... .... .... ...0 .... = Transmit Null Data packet (NDP):

                                                          Not supported

                .... .... .... .... .... .... ..0. .... = Implicit TxBF capable: Not supported

                .... .... .... .... .... .... 00.. .... = Calibration: incapable (0x00000000)

                .... .... .... .... .... ...0 .... .... = STA can apply TxBF using CSI explicit

                                                          feedback: Not supported

                .... .... .... .... .... ..0. .... .... = STA can apply TxBF using uncompressed

                                                       beamforming feedback matrix: Not supported

                .... .... .... .... .... .0.. .... .... = STA can apply TxBF using compressed

                                                       beamforming feedback matrix: Not supported

                .... .... .... .... ...0 0... .... .... = Receiver can return explicit CSI

                                                       feedback: not supported (0x00000000)

                .... .... .... .... .00. .... .... .... = Receiver can return explicit

                                                          uncompressed Beamforming Feedback Matrix:

                                                          not supported (0x00000000)

                .... .... .... ...0 0... .... .... .... = STA can compress and use compressed

                                                          Beamforming Feedback Matrix:

                                                          not supported (0x00000000)

                .... .... .... .00. .... .... .... .... = Minimal grouping used for explicit

                                                          feedback reports: No grouping supported

                                                          (0x00000000)

                .... .... ...0 0... .... .... .... .... = Max antennae STA can support when CSI

                                                          feedback required: 1 TX antenna sounding

                                                          (0x00000000)

                .... .... .00. .... .... .... .... .... = Max antennae STA can support when

                                                          uncompressed Beamforming feedback

                                                          required: 1 TX antenna sounding

                                                          (0x00000000)

                .... ...0 0... .... .... .... .... .... = Max antennae STA can support when

                                                          compressed Beamforming feedback required:

                                                          1 TX antenna sounding (0x00000000)

                .... .00. .... .... .... .... .... .... = Maximum number of rows of CSI explicit

                                                          feedback: 1 row of CSI (0x00000000)

                ...0 0... .... .... .... .... .... .... = Maximum number of space time streams

                                                          for which channel dimensions can be

                                                          simultaneously estimated: 1 space time

                                                          stream (0x00000000)

                000. .... .... .... .... .... .... .... = Reserved: 0x00000000

            Antenna Selection (ASEL) Capabilities: 0x00

                .... ...0 = Antenna Selection Capable: Not supported

                .... ..0. = Explicit CSI Feedback Based Tx ASEL: Not supported

                .... .0.. = Antenna Indices Feedback Based Tx ASEL: Not supported

                .... 0... = Explicit CSI Feedback: Not supported

                ...0 .... = Antenna Indices Feedback: Not supported

                ..0. .... = Rx ASEL: Not supported

                .0.. .... = Tx Sounding PPDUs: Not supported

                0... .... = Reserved: 0x00

        Tag: HT Information (802.11n D1.10)

            Tag Number: HT Information (802.11n D1.10) (61)

            Tag length: 22

            Primary Channel: 36

            HT Information Subset (1 of 3): 0x05

                .... ..01 = Secondary channel offset: Secondary channel is above the primary

                            channel (0x01)

                .... .1.. = Supported channel width: Channel of any width supported

                .... 0... = Reduced Interframe Spacing (RIFS): Prohibited

                ...0 .... = Power Save Multi-Poll (PSMP) stations only: Association requests are

                            accepted regardless of PSMP capability

                000. .... = Shortest service interval: 5 ms (0x00)

            HT Information Subset (2 of 3): 0x0000

                .... .... .... ..00 = Operating mode of BSS: All STAs are - 20/40 MHz HT

                                      or in a 20/40 MHz BSS or are 20 MHz HT in a 20 MHz BSS

                                      (0x0000)

                .... .... .... .0.. = Non-greenfield STAs present:

                                      All associated STAs are greenfield capable

                .... .... .... 0... = Transmit burst limit: No limit

                .... .... ...0 .... = OBSS non-HT STAs present: Use of protection for non-HT STAs

                                      by overlapping BSSs is not needed

                0000 0000 000. .... = Reserved: 0x0000

            HT Information Subset (3 of 3): 0x0000

                .... .... ..00 0000 = Reserved: 0x0000

                .... .... .0.. .... = Dual beacon: No second beacon is transmitted

                .... .... 0... .... = Dual Clear To Send (CTS) protection: Not required

                .... ...0 .... .... = Beacon ID: Primary beacon

                .... ..0. .... .... = L-SIG TXOP Protection Full Support: One or more HT STAs

                                      in the BSS do not support L-SIG TXOP protection

                .... .0.. .... .... = Phased Coexistence Operation (PCO): Inactive

                .... 0... .... .... = Phased Coexistence Operation (PCO) Phase: Switch to or

                                      continue 20 MHz phase

                0000 .... .... .... = Reserved: 0x0000

            Rx Supported Modulation and Coding Scheme Set: Basic MCS Set

                Rx Modulation and Coding Scheme (One bit per modulation): Reserved:8

                    .... .... .... .... .... .... 0000 0000 = Rx Bitmask Bits 0-7: 0x00000000

                    .... .... .... .... 0000 0000 .... .... = Rx Bitmask Bits 8-15: 0x00000000

                    .... .... 0000 0000 .... .... .... .... = Rx Bitmask Bits 16-23: 0x00000000

                    0000 0000 .... .... .... .... .... .... = Rx Bitmask Bits 24-31: 0x00000000

                    .... .... .... .... .... .... .... ...0 = Rx Bitmask Bit 32: 0x00000000

                    .... .... .... .... .... .... .000 000. = Rx Bitmask Bits 33-38: 0x00000000

                    .... .... ...0 0000 0000 0000 0... .... = Rx Bitmask Bits 39-52: 0x00000000

                    ...0 0000 0000 0000 0000 0000 000. .... = Rx Bitmask Bits 53-76: 0x00000000

                .... ..00 0000 0000 = Highest Supported Data Rate: 0x0000

                .... .... .... ...0 = Tx Supported MCS Set: Not Defined

                .... .... .... ..0. = Tx and Rx MCS Set: Equal

                .... .... .... 00.. = Maximum Number of Tx Spatial Streams Supported: 0x0000,

                                      TX MCS Set Not Defined

                .... .... ...0 .... = Unequal Modulation: Not supported

        Tag: VHT Capabilities (IEEE Stc 802.11ac/D3.1)

            Tag Number: VHT Capabilities (IEEE Stc 802.11ac/D3.1) (191)

            Tag length: 12

            VHT Capabilities Info: 0x03800022

                .... .... .... .... .... .... .... ..10 = Maximum MPDU Length: 11 454 (0x00000002)

                .... .... .... .... .... .... .... 00.. = Supported Channel Width Set:

                                                          Neither 160MHz nor 80+80 supported

                                                          (0x00000000)

                .... .... .... .... .... .... ...0 .... = Rx LDPC: Not supported

                .... .... .... .... .... .... ..1. .... = Short GI for 80MHz: Supported

                .... .... .... .... .... .... .0.. .... = Short GI for 160MHz and 80+80MHz:

                                                          Not supported

                .... .... .... .... .... .... 0... .... = Tx STBC: Not supported

                .... .... .... .... .... .000 .... .... = Rx STBC: None (0x00000000)

                .... .... .... .... .... 0... .... .... = SU Beam-former Capable: Not supported

                .... .... .... .... ...0 .... .... .... = SU Beam-formee Capable: Not supported

                .... .... .... .... 000. .... .... .... = Compressed Steering Number of Beamformer

                                                          Antennas Supported: 1 (0x00000000)

                .... .... .... .000 .... .... .... .... = Number of Sounding Dimensions: 1

                                                          (0x00000000)

                .... .... .... 0... .... .... .... .... = MU Beam-former Capable: Not supported

                .... .... ...0 .... .... .... .... .... = MU Beam-formee Capable: Not supported

                .... .... ..0. .... .... .... .... .... = VHT TXOP PS: Not supported

                .... .... .0.. .... .... .... .... .... = +HTC-VHT Capable (VHT variant HT Control

                                                          field): Not supported

                .... ..11 1... .... .... .... .... .... = Max A-MPDU Length: 1 048 575 (0x00000007)

                .... 00.. .... .... .... .... .... .... = VHT Link Adaptation: No Feedback

                                                          (0x00000000)

                ...0 .... .... .... .... .... .... .... = Rx Antenna Pattern Consistency:

                                                          Not supported

                ..0. .... .... .... .... .... .... .... = Tx Antenna Pattern Consistency:

                                                          Not supported

                00.. .... .... .... .... .... .... .... = Reserved: False

            VHT Supported MCS Set

                Rx MCS Map: 0xfffe

                    .... .... .... ..10 = Rx 1 SS: MCS 0-9 (0x0002)

                    .... .... .... 11.. = Rx 2 SS: Not Supported (0x0003)

                    .... .... ..11 .... = Rx 3 SS: Not Supported (0x0003)

                    .... .... 11.. .... = Rx 4 SS: Not Supported (0x0003)

                    .... ..11 .... .... = Rx 5 SS: Not Supported (0x0003)

                    .... 11.. .... .... = Rx 6 SS: Not Supported (0x0003)

                    ..11 .... .... .... = Rx 7 SS: Not Supported (0x0003)

                    11.. .... .... .... = Rx 8 SS: Not Supported (0x0003)

                ...0 0000 0000 0000 = Rx Highest Long GI Data Rate

                                      (in Mb/s, 0 = subfield not in use): 0x0000

                Tx MCS Map: 0xfffe

                    .... .... .... ..10 = Tx 1 SS: MCS 0-9 (0x0002)

                    .... .... .... 11.. = Tx 2 SS: Not Supported (0x0003)

                    .... .... ..11 .... = Tx 3 SS: Not Supported (0x0003)

                    .... .... 11.. .... = Tx 4 SS: Not Supported (0x0003)

                    .... ..11 .... .... = Tx 5 SS: Not Supported (0x0003)

                    .... 11.. .... .... = Tx 6 SS: Not Supported (0x0003)

                    ..11 .... .... .... = Tx 7 SS: Not Supported (0x0003)

                    11.. .... .... .... = Tx 8 SS: Not Supported (0x0003)

                ...0 0000 0000 0000 = Tx Highest Long GI Data Rate  

                                      (in Mb/s, 0 = subfield not in use): 0x0000

        Tag: VHT Operation (IEEE Stc 802.11ac/D3.1)

            Tag Number: VHT Operation (IEEE Stc 802.11ac/D3.1) (192)

            Tag length: 5

            VHT Operation Info

                Channel Width: 80 MHz (0x01)

                Channel Center Segment 0: 42

                Channel Center Segment 1: 0

            Basic MCS Map: 0xfffc

                .... .... .... ..00 = Basic 1 SS: MCS 0-7 (0x0000)

                .... .... .... 11.. = Basic 2 SS: Not Supported (0x0003)

                .... .... ..11 .... = Basic 3 SS: Not Supported (0x0003)

                .... .... 11.. .... = Basic 4 SS: Not Supported (0x0003)

                .... ..11 .... .... = Basic 5 SS: Not Supported (0x0003)

                .... 11.. .... .... = Basic 6 SS: Not Supported (0x0003)

                ..11 .... .... .... = Basic 7 SS: Not Supported (0x0003)

                11.. .... .... .... = Basic 8 SS: Not Supported (0x0003)

        Tag: Vendor Specific: Microsof: WMM/WME: Parameter Element

            Tag Number: Vendor Specific (221)

            Tag length: 24

            OUI: 00-50-f2 (Microsof)

            Vendor Specific OUI Type: 2

            Type: WMM/WME (0x02)

            WME Subtype: Parameter Element (1)

            WME Version: 1

            WME QoS Info: 0x00

                0... .... = U-APSD: Disabled

                .... 0000 = Parameter Set Count: 0x00

                .000 .... = Reserved: 0x00

            Reserved: 00

            Ac Parameters ACI 0 (Best Effort), ACM no , AIFSN 3, ECWmin 4 ,ECWmax 10, TXOP 0

                ACI / AIFSN Field: 0x03

                    .00. .... = ACI: Best Effort (0)

                    ...0 .... = Admission Control Mandatory: No

                    .... 0011 = AIFSN: 3

                    0... .... = Reserved: 0

                ECW: 0xa4

                    1010 .... = ECW Max: 10

                    .... 0100 = ECW Min: 4

                TXOP Limit: 0

            Ac Parameters ACI 1 (Background), ACM no , AIFSN 7, ECWmin 4 ,ECWmax 10, TXOP 0

                ACI / AIFSN Field: 0x27

                    .01. .... = ACI: Background (1)

                    ...0 .... = Admission Control Mandatory: No

                    .... 0111 = AIFSN: 7

                    0... .... = Reserved: 0

                ECW: 0xa4

                    1010 .... = ECW Max: 10

                    .... 0100 = ECW Min: 4

                TXOP Limit: 0

            Ac Parameters ACI 2 (Video), ACM no , AIFSN 2, ECWmin 3 ,ECWmax 4, TXOP 94

                ACI / AIFSN Field: 0x42

                    .10. .... = ACI: Video (2)

                    ...0 .... = Admission Control Mandatory: No

                    .... 0010 = AIFSN: 2

                    0... .... = Reserved: 0

                ECW: 0x43

                    0100 .... = ECW Max: 4

                    .... 0011 = ECW Min: 3

                TXOP Limit: 94

            Ac Parameters ACI 3 (Voice), ACM no , AIFSN 2, ECWmin 2 ,ECWmax 3, TXOP 47

                ACI / AIFSN Field: 0x62

                    .11. .... = ACI: Voice (3)

                    ...0 .... = Admission Control Mandatory: No

                    .... 0010 = AIFSN: 2

                    0... .... = Reserved: 0

                ECW: 0x32

                    0011 .... = ECW Max: 3

                    .... 0010 = ECW Min: 2

                TXOP Limit: 47