Patent Publication Number: US-11032237-B1

Title: Changing a basic service set color identifier

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/945,460, now U.S. Pat. No. 10,404,653, entitled “Changing a Basic Service Set Color Identifier,” filed on Apr. 4, 2018, which is a continuation of U.S. patent application Ser. No. 14/961,359, now U.S. Pat. No. 9,942,193, entitled “Basic Service Set Color Identifier,” filed on Dec. 7, 2015, which claims the benefit of U.S. Provisional Patent Application No. 62/088,008, entitled “BSS Identifier and OFDMA Short Frame Format,” filed on Dec. 5, 2014, U.S. Provisional Patent Application No. 62/112,967, entitled “BSS Identifier and OFDMA Short Frame Format,” filed on Feb. 6, 2015, and U.S. Provisional Patent Application No. 62/140,393, entitled “BSS Identifier and OFDMA Short Frame Format,” filed on Mar. 30, 2015. The disclosures of all of the applications referenced above are incorporated herein by reference in their entireties. 
     Additionally, this application is related to U.S. patent application Ser. No. 14/961,512, entitled “ORTHOGONAL FREQUENCY DIVISION MULTIPLE ACCESS SHORT FRAME FORMAT,” filed on Dec. 7, 2015. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure relates generally to communication networks and, more particularly, to wireless local area networks that utilize multiple basic service set identifiers having different lengths. 
     BACKGROUND 
     Wireless local area networks (WLANs) have evolved rapidly over the past decade. Development of WLAN standards such as the Institute for Electrical and Electronics Engineers (IEEE) 802.11a, 802.11b, 802.11g, and 802.11n Standards has improved single-user peak data throughput. For example, the IEEE 802.11b Standard specifies a single-user peak throughput of 11 megabits per second (Mbps), the IEEE 802.11a and 802.11g Standards specify a single-user peak throughput of 54 Mbps, the IEEE 802.11n Standard specifies a single-user peak throughput of 600 Mbps, and the IEEE 802.11ac Standard specifies a single-user peak throughput in the gigabits per second (Gbps) range. Future standards promise to provide even greater throughputs, such as throughputs in the tens of Gbps range. 
     SUMMARY 
     In an embodiment, a method includes: determining, at a communication device, that a first value of a first basic service set (BSS) color identifier is the same as a value of a second BSS color identifier, wherein the first BSS color identifier corresponds to a first wireless network and the second BSS color identifier corresponds to a second wireless network that neighbors the first wireless network, and wherein the first BSS color identifier is shorter than a BSS identifier (BSSID) corresponding to the first wireless network; determining, at the communication device, a second value of the first BSS color identifier in response to determining that the first value of the first BSS color identifier is the same as the value of the second BSS color identifier; transmitting, by the communication device, one or more packets that each include i) an indication that the first BSS color identifier is changing, ii) the second value of the first BSS color identifier, and iii) a respective integer number of remaining beacon intervals corresponding to a start time when the second value of the first BSS color identifier will supersede the first value of the first BSS color identifier; and based on the start time, beginning to use, at the communication device, the second value of the first BSS color identifier with communications with other communication devices in the first wireless network. 
     In another embodiment, an apparatus comprises a network interface device having one or more integrated circuit (IC) devices. The one or more IC devices are configured to: determine that a first value of a first basic service set (BSS) color identifier is the same as a value of a second BSS color identifier, wherein the first BSS color identifier corresponds to a first wireless network and the second BSS color identifier corresponds to a second wireless network that neighbors the first wireless network, and wherein the first BSS color identifier is shorter than a BSS identifier (BSSID) corresponding to the first wireless network; determine a second value of the first BSS color identifier in response to determining that the first value of the first BSS color identifier is the same as the value of the second BSS color identifier; transmit or more packets that each include i) an indication that the first BSS color identifier is changing, ii) the second value of the first BSS color identifier, and iii) a respective integer number of remaining beacon intervals corresponding to a start time when the second value of the first BSS color identifier will supersede the first value of the first BSS color identifier; and based on the start time, begin to use the second value of the first BSS color identifier with communications with other communication devices in the first wireless network. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of an example wireless local area network (WLAN), according to an embodiment. 
         FIGS. 2A and 2B  are diagrams of a prior art data unit format. 
         FIG. 3  is a diagram of another prior art data unit format. 
         FIG. 4  is a diagram of another prior art data unit format. 
         FIG. 5  is a diagram of another prior art data unit format. 
         FIG. 6  is a diagram of an orthogonal frequency division multiplexing (OFDM) data unit, according to an embodiment. 
         FIG. 7  is a diagram of a medium access control (MAC) protocol data unit (MPDU), according to an embodiment. 
         FIG. 8  is a diagram of an MPDU, according to another embodiment. 
         FIG. 9  is a diagram of an example system having a first access point, a second access point, and a network management device, according to an embodiment. 
         FIG. 10  is a diagram of a sequence of OFDM data units transmitted by an access point for a change in the BSS color identifier of the access point, according to an embodiment. 
         FIG. 11  is a diagram of a sequence of OFDM data units transmitted by the access point for a change in the BSS color identifier of the access point, according to another embodiment. 
         FIG. 12  is a flow diagram illustrating an example method for changing a first basic service set (BSS) color identifier for a first communication device, according to an embodiment. 
         FIG. 13  is a flow diagram illustrating an example method for causing a change of a first BSS color identifier for a first communication device, according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In embodiments described below, a wireless network device such as an access point (AP) of a wireless local area network (WLAN) is identifiable by a basic service set identifier (BSSID) and a basic service set (BSS) color identifier. In an embodiment, the BSSID is an identifier that uniquely identifies the access point, while the BSS color identifier has a shorter length than the BSSID but does not uniquely identify the access point. For example, the BSS color identifier is a short, local address that is unique within a wireless network associated with the device but is not unique with respect to other wireless networks, in an embodiment. The shorter length of the BSS color identifier helps to reduce signaling overhead for transmissions to the access point (e.g., uplink frames) and/or transmissions from the access point (e.g., downlink frames). In some scenarios, one or more “collisions” occur when a first access point and a second access point are located proximately to each other and have a same value for their respective BSS color identifiers. For example, a client station or other communication device that receives a downlink frame that includes the BSS color identifier, but omits the BSSID, cannot readily determine which access point transmitted the downlink frame. In an embodiment, a communication device that detects a collision transmits a suitable indication of the collision to the first access point to cause a change in a value of the BSS color identifier for the first access point. 
       FIG. 1  is a block diagram of an example wireless local area network (WLAN)  10 , according to an embodiment. An AP  14  includes a host processor  15  coupled to a network interface  16 . In an embodiment, the network interface  16  includes one or more integrate circuits (ICs) configured to operate as discussed below. The network interface  16  includes a medium access control (MAC) processing unit  18  and a physical layer (PHY) processing unit  20 . The PHY processing unit  20  includes a plurality of transceivers  21 , and the transceivers  21  are coupled to a plurality of antennas  24 . Although three transceivers  21  and three antennas  24  are illustrated in  FIG. 1 , the AP  14  includes other suitable numbers (e.g., 1, 2, 4, 5, etc.) of transceivers  21  and antennas  24  in other embodiments. In some embodiments, the AP  14  includes a higher number of antennas  24  than transceivers  21 , and antenna switching techniques are utilized. 
     In one embodiment, the MAC processing unit  18  and the PHY processing unit  20  are configured to operate according to a first communication protocol (e.g., the HE communication protocol), including at least a first transmission mode and a second transmission mode of the first communication protocol. In some embodiments, the first transmission mode corresponds to a use of a BSS color identifier instead of a BSSID for transmissions to and/or from an access point, while the second transmission mode corresponds to a use of the BSSID for transmissions to and/or from the access point. The first transmission mode is configured to reduce signaling overhead as compared to the second transmission mode, which corresponds to an identifier for the access point that has a shorter length than for the second transmission mode. In another embodiment, the MAC processing unit  18  and the PHY processing unit  20  are also configured to operate according to a second communication protocol (e.g., according to the IEEE 802.11ac Standard). In yet another embodiment, the MAC processing unit  18  and the PHY processing unit  20  are additionally configured to operate according to the second communication protocol, a third communication protocol, and/or a fourth communication protocol (e.g., according to the IEEE 802.11a Standard and/or the IEEE 802.11n Standard). 
     The WLAN  10  includes a plurality of client stations  25 . Although four client stations  25  are illustrated in  FIG. 1 , the WLAN  10  includes other suitable numbers (e.g., 1, 2, 3, 5, 6, etc.) of client stations  25  in various scenarios and embodiments. At least one of the client stations  25  (e.g., client station  25 - 1 ) is configured to operate at least according to the first communication protocol. In some embodiments, at least one of the client stations  25  is not configured to operate according to the first communication protocol but is configured to operate according to at least one of the second communication protocol, the third communication protocol, and/or the fourth communication protocol (referred to herein as a “legacy client station”). 
     The client station  25 - 1  includes a host processor  26  coupled to a network interface  27 . In an embodiment, the network interface  27  includes one or more ICs configured to operate as discussed below. The network interface  27  includes a MAC processing unit  28  and a PHY processing unit  29 . The PHY processing unit  29  includes a plurality of transceivers  30 , and the transceivers  30  are coupled to a plurality of antennas  34 . Although three transceivers  30  and three antennas  34  are illustrated in  FIG. 1 , the client station  25 - 1  includes other suitable numbers (e.g., 1, 2, 4, 5, etc.) of transceivers  30  and antennas  34  in other embodiments. In some embodiments, the client station  25 - 1  includes a higher number of antennas  34  than transceivers  30 , and antenna switching techniques are utilized. 
     According to an embodiment, the client station  25 - 4  is a legacy client station, i.e., the client station  25 - 4  is not enabled to receive and fully decode a data unit that is transmitted by the AP  14  or another client station  25  according to the first communication protocol. Similarly, according to an embodiment, the legacy client station  25 - 4  is not enabled to transmit data units according to the first communication protocol. On the other hand, the legacy client station  25 - 4  is enabled to receive and fully decode and transmit data units according to the second communication protocol, the third communication protocol, and/or the fourth communication protocol. 
     In an embodiment, one or both of the client stations  25 - 2  and  25 - 3 , has a structure that is the same as or similar to the client station  25 - 1 . In an embodiment, the client station  25 - 4  has a structure similar to the client station  25 - 1 . In these embodiments, the client stations  25  structured the same as or similar to the client station  25 - 1  have the same or a different number of transceivers and antennas. For example, the client station  25 - 2  has only two transceivers and two antennas (not shown), according to an embodiment. 
     In various embodiments, the PHY processing unit  20  of the AP  14  is configured to generate data units conforming to the first communication protocol and having formats described herein. The transceiver(s)  21  is/are configured to transmit the generated data units via the antenna(s)  24 . Similarly, the transceiver(s)  21  is/are configured to receive data units via the antenna(s)  24 . The PHY processing unit  20  of the AP  14  is configured to process received data units conforming to the first communication protocol and having formats described hereinafter and to determine that such data units conform to the first communication protocol, according to various embodiments. 
     In various embodiments, the PHY processing unit  29  of the client device  25 - 1  is configured to generate data units conforming to the first communication protocol and having formats described herein. The transceiver(s)  30  is/are configured to transmit the generated data units via the antenna(s)  34 . Similarly, the transceiver(s)  30  is/are configured to receive data units via the antenna(s)  34 . The PHY processing unit  29  of the client device  25 - 1  is configured to process received data units conforming to the first communication protocol and having formats described hereinafter and to determine that such data units conform to the first communication protocol, according to various embodiments. 
     In various embodiments, the client device  25 - 1  is configured to receive OFDM data units from access points that are identifiable by a basic service set (BSS) color identifier and a basic service set identifier (BSSID) having a length that is longer than a length of the BSS color identifier. In an embodiment, the client device  25 - 1  maintains an association of the BSSID with the BSS color identifier such that the client device  25 - 1  can generally identify which access point has transmitted an OFDM data unit when the OFDM data unit includes the BSS color identifier but omits the BSSID. In an embodiment, the client device  25 - 1  stores and/or maintains a list of BSS color identifiers that have been received or detected. 
       FIG. 2A  is a diagram of a prior art orthogonal frequency division multiplexing (OFDM) data unit  200  that the AP  14  is configured to transmit to the legacy client station  25 - 4  via orthogonal frequency division multiplexing (OFDM) modulation, according to an embodiment. In an embodiment, the legacy client station  25 - 4  is also configured to transmit the data unit  200  to the AP  14 . The data unit  200  conforms to the IEEE 802.11a Standard and occupies a 20 Megahertz (MHz) bandwidth. The data unit  200  includes a preamble having a legacy short training field (L-STF)  202 , generally used for packet detection, initial synchronization, and automatic gain control, etc., and a legacy long training field (L-LTF)  204 , generally used for channel estimation and fine synchronization. The data unit  200  also includes a legacy signal field (L-SIG)  206 , used to carry certain physical layer (PHY) parameters with the data unit  200 , such as modulation type and coding rate used to transmit the data unit, for example. The data unit  200  also includes a data portion  208 .  FIG. 2B  is a diagram of example data portion  208  (not low density parity check encoded), which includes a service field, a scrambled physical layer service data unit (PSDU), tail bits, and padding bits, if needed. The data unit  200  is designed for transmission over one spatial or space-time stream in a single input single output (SISO) channel configuration. In various embodiments, the data portion  208  includes a MAC protocol data unit (MPDU), for example, the MPDU  700  ( FIG. 7 ) or the MPDU  800  ( FIG. 8 ). 
       FIG. 3  is a diagram of a prior art OFDM data unit  300  that the AP  14  is configured to transmit to the legacy client station  25 - 4  via OFDM modulation, according to an embodiment. In an embodiment, the legacy client station  25 - 4  is also configured to transmit the data unit  300  to the AP  14 . The data unit  300  conforms to the IEEE 802.11n Standard, occupies a 20 MHz bandwidth, and is designed for mixed mode situations, i.e., when the WLAN includes one or more client stations that conform to the IEEE 802.11a Standard but not the IEEE 802.11n Standard. The data unit  300  includes a preamble having an L-STF  302 , an L-LTF  304 , an L-SIG  306 , a high throughput signal field (HT-SIG)  308 , a high throughput short training field (HT-STF)  310 , and M data high throughput long training fields (HT-LTFs)  312 , where M is an integer generally based on the number of spatial streams used to transmit the data unit  300  in a multiple input multiple output (MIMO) channel configuration. In particular, according to the IEEE 802.11n Standard, the data unit  300  includes two HT-LTFs  312  if the data unit  300  is transmitted using two spatial streams, and four HT-LTFs  312  is the data unit  300  is transmitted using three or four spatial streams. An indication of the particular number of spatial streams being utilized is included in the HT-SIG field  308 . The data unit  300  also includes a data portion  314 . In various embodiments, the data portion  314  includes an MPDU, for example, the MPDU  700  ( FIG. 7 ) or the MPDU  800  ( FIG. 8 ). 
       FIG. 4  is a diagram of a prior art OFDM data unit  400  that the AP  14  is configured to transmit to the legacy client station  25 - 4  via OFDM modulation, according to an embodiment. In an embodiment, the legacy client station  25 - 4  is also configured to transmit the data unit  400  to the AP  14 . The data unit  400  conforms to the IEEE 802.11n Standard, occupies a 20 MHz bandwidth, and is designed for “Greenfield” situations, i.e., when the WLAN does not include any client stations that conform to the IEEE 802.11a Standard, and only includes client stations that conform to the IEEE 802.11n Standard. The data unit  400  includes a preamble having a high throughput Greenfield short training field (HT-GF-STF)  402 , a first high throughput long training field (HT-LTF1)  404 , a HT-SIG  406 , and M data HT-LTFs  408 . The data unit  400  also includes a data portion  410 . In various embodiments, the data portion  410  includes an MPDU, for example, the MPDU  700  ( FIG. 7 ) or the MPDU  800  ( FIG. 8 ). 
       FIG. 5  is a diagram of a prior art OFDM data unit  500  that the AP  14  is configured to transmit to the legacy client station  25 - 4  via OFDM modulation, according to an embodiment. In an embodiment, the legacy client station  25 - 4  is also configured to transmit the data unit  500  to the AP  14 . The data unit  500  conforms to the IEEE 802.11ac Standard and is designed for “Mixed field” situations. The data unit  500  occupies a 20 MHz bandwidth. In other embodiments or scenarios, a data unit similar to the data unit  500  occupies a different suitable bandwidth, such as a 40 MHz, an 80 MHz, or a 160 MHz bandwidth. The data unit  500  includes a preamble having an L-STF  502 , an L-LTF  504 , an L-SIG  506 , two first very high throughput signal fields (VHT-SIGAs)  508  including a first very high throughput signal field (VHT-SIGA 1 )  508 - 1  and a second very high throughput signal field (VHT-SIGA 2 )  508 - 2 , a very high throughput short training field (VHT-STF)  510 , M very high throughput long training fields (VHT-LTFs)  512 , and a second very high throughput signal field (VHT-SIG-B)  514 . The data unit  500  also includes a data portion  516 . In various embodiments, the data portion  516  includes an MPDU, for example, the MPDU  700  ( FIG. 7 ) or the MPDU  800  ( FIG. 8 ). 
     In an embodiment, the data unit  500  occupies a bandwidth that is an integer multiple of 20 MHz and the L-STF  502  is duplicated within each 20 MHz sub-band. In an embodiment, the VHT-STF  510  has a duration of 4.0 microseconds and uses a same frequency sequence as the L-STF  502 . For example, in an embodiment, the VHT-STF  510  uses the frequency sequence defined in equation 22-29 of the IEEE 802.11ac standard. In at least some embodiments, the VHT-STF  510  occupies a whole bandwidth for the data unit  500  (e.g., 20 MHz, 40 MHz, 80 MHz, etc.) and is mapped to multiple antennas for multiple input, multiple output (MIMO) or beamforming in a manner similar to the data portion  516 . 
       FIG. 6  is a diagram of an OFDM data unit  600  that the AP  14  is configured to transmit to the client station  25 - 1  via orthogonal frequency domain multiplexing (OFDM) modulation, according to an embodiment. In an embodiment, the client station  25 - 1  is also configured to transmit the data unit  600  to the AP  14 . The data unit  600  conforms to the first communication protocol and occupies a 20 MHz bandwidth. Data units that conform to the first communication protocol similar to the data unit  600  may occupy other suitable bandwidths such as 40 MHz, 80 MHz, 160 MHz, 320 MHz, 640 MHz, etc., for example, or other suitable bandwidths, in other embodiments. The data unit  600  is suitable for “mixed mode” situations, i.e., when the WLAN  10  includes a client station (e.g., the legacy client station  25 - 4 ) that conforms to a legacy communication protocol, but not the first communication protocol. The data unit  600  is utilized in other situations as well, in some embodiments. 
     In an embodiment, the data unit  600  includes a preamble  601  having an L-STF  602 , an L-LTF  604 , an L-SIG  606 , two first HE signal fields (HE-SIGAs)  608  including a first HE signal field (HE-SIGA 1 )  608 - 1  and a second HE signal field (HE-SIGA 2 )  608 - 2 , a HE short training field (HE-STF)  610 , M HE long training fields (HE-LTFs)  612 , and a third HE signal field (HE-SIGB)  614 . In an embodiment, the preamble  601  includes a legacy portion  601 - 1 , including the L-STF  602 , the L-LTF  604 , and the L-SIG  606 , and a non-legacy portion  601 - 2 , including the HE-SIGAs  608 , HE-STF  610 , M HE-LTFs  612 , and HE-SIGB  614 . 
     Each of the L-STF  602 , the L-LTF  604 , the L-SIG  606 , the HE-SIGAs  608 , the HE-STF  610 , the M HE-LTFs  612 , and the HE-SIGB  614  are included in an integer number of one or more OFDM symbols. For example, in an embodiment, the HE-SIGAs  608  correspond to two OFDM symbols, where the HE-SIGA 1   608 - 1  field is included in the first OFDM symbol and the HE-SIGA 2  is included in the second OFDM symbol. In another embodiment, for example, the preamble  601  includes a third HE signal field (HE-SIGA 3 , not shown) and the HE-SIGAs  608  correspond to three OFDM symbols, where the HE-SIGA 1   608 - 1  field is included in the first OFDM symbol, the HE-SIGA 2  is included in the second OFDM symbol, and the HE-SIGA 3  is included in the third OFDM symbol. In at least some examples, the HE-SIGAs  608  are collectively referred to as a single HE signal field (HE-SIGA)  608 . In some embodiments, the data unit  600  also includes a data portion  616 . In other embodiments, the data unit  600  omits the data portion  616  (e.g., the data unit  600  is a null-data packet). In various embodiments, the data portion  616  includes an MPDU, for example, the MPDU  700  ( FIG. 7 ) or the MPDU  800  ( FIG. 8 ). 
     In the embodiment of  FIG. 6 , the data unit  600  includes one of each of the L-STF  602 , the L-LTF  604 , the L-SIG  606 , and the HE-SIGA 1 s  608 . In other embodiments in which an OFDM data unit similar to the data unit  600  occupies a cumulative bandwidth other than 20 MHz, each of the L-STF  602 , the L-LTF  604 , the L-SIG  606 , the HE-SIGA 1 s  608  is repeated over a corresponding number of 20 MHz-wide sub-bands of the whole bandwidth of the data unit, in an embodiment. For example, in an embodiment, the OFDM data unit occupies an 80 MHz bandwidth and, accordingly, includes four of each of the L-STF  602 , the L-LTF  604 , the L-SIG  606 , and the HE-SIGA 1 s  608  in four 20 MHz-wide sub-bands that cumulatively span the 80 MHz bandwidth, in an embodiment. In some embodiments, the modulation of different 20 MHz-wide sub-bands signals is rotated by different angles. For example, in one embodiment, a first sub-band is rotated 0-degrees, a second sub-band is rotated 90-degrees, a third sub-band is rotated 180-degrees, and a fourth sub-band is rotated 270-degrees. In other embodiments, different suitable rotations are utilized. The different phases of the 20 MHz-wide sub-band signals result in reduced peak to average power ratio (PAPR) of OFDM symbols in the data unit  600 , in at least some embodiments. In an embodiment, if the data unit that conforms to the first communication protocol is an OFDM data unit that occupies a cumulative bandwidth such as 20 MHz, 40 MHz, 80 MHz, 160 MHz, 320 MHz, 640 MHz, etc., the HE-STF, the HE-LTFs, the HE-SIGB and the HE data portion occupy the corresponding whole bandwidth of the data unit. 
       FIG. 7  is a diagram of an MPDU  700 , according to an embodiment. The MPDU  700  includes a MAC header  702 , a frame body  704 , and a frame check sequence field  720 . The number above each field in  FIG. 7  indicates the number of octets occupied by the corresponding field. Accordingly, the MAC header  702  includes a frame control field  704  (2 octets), a duration/ID field  706  (2 octets), a first address (A1) field  710 - 1  (6 octets), a second address (A2) field  710 - 2  (6 octets), a third address (A3) field (6 octets)  710 - 3 , a sequence control field  712  (2 octets), a fourth address (A4) field  710 - 4  (6 octets), a QoS control field  714  (2 octets), and an HT control field  716  (4 octets). The data unit  700  also includes the frame body  718  and a four-octet frame check sequence (FCS) field  720 . In some embodiments and/or scenarios, the frame body  718  is omitted (e.g., a null data frame). Each of the address fields  710  is a 48 bit (6 octet) field that includes a globally unique MAC address of a device associated with the data unit  700 , such as a transmitting device of the data unit  700 , a receiving device of the data unit  700 , etc. In general, the MAC header  702  occupies 36 octets of the MPDU  700 . 
       FIG. 8  is a diagram of an MPDU  800 , according to another embodiment. The MPDU  800  includes a MAC header  802 , a frame body  804 , and a frame check sequence field  806 . The number above each field in  FIG. 8  indicates the number of octets occupied by the corresponding field. Accordingly, the MAC header  802  includes a frame control field  804  (2 octets), a first address (A1) field  810 - 1  (2 or 6 octets), a second address (A2) field  810 - 2  (2 or 6 octets), a third address (A3) field (0 or 6 octets)  810 - 3 , a sequence control field  812  (0 or 2 octets), and a fourth address (A4) field  810 - 4  (0 or 6 octets). The data unit  800  also includes the frame body  818  and a four-octet frame check sequence (FCS) field  820 . In some embodiments and/or scenarios, the frame body  818  is omitted (e.g., a null data frame). 
     As compared to the MPDU  700 , the MPDU  800  has a “short frame format” having a reduced length of the MAC header  802 . In some embodiments and/or scenarios, one or more of the address fields  810 - 1  or  810 - 2  is a 48 bit (6 octet) field that includes a globally unique MAC address of a device associated with the data unit  800 , such as a transmitting device of the data unit  800 , a receiving device of the data unit  800 , etc. In other embodiments and/or scenarios, one or more of the address fields  810 - 1  or  810 - 2  is a 16 bit (2 octet) field that includes a BSS color identifier, partial association identification (PAID or partial AID), or other suitable address having a reduced length as compared to a MAC address (i.e., less than 6 octets). In various embodiments, the BSS color identifier occupies 6 bits, 7 bits, 10 bits, or another suitable number of bits. In some embodiments and/or scenarios, one or more of the sequence control field  812 , the address field  810 - 3 , or the address field  810 - 4  are optional and omitted from the MAC header  802 . In general, the MAC header  802  occupies 6 octets, or up to 28 octets, of the MPDU  800 . 
       FIG. 9  is a diagram of an example system  900  having a first access point  902 , a second access point  904 , and a client station (STA 1 )  922 , according to an embodiment. While only two access points and a single client station are shown in  FIG. 9 , in other embodiments, the system  900  includes other suitable numbers of access points and other suitable numbers of client stations. In an embodiment, the first access point  902  and the second access point  904  are implemented as instances of the access point  14  described above with reference to  FIG. 1 . In an embodiment, the client station  922  is implemented as an instance of the client station  25 . The first access point  902  and the second access point  904  communicate with client stations by transmitting and/or receiving OFDM data units, for example, OFDM data unit  200 , OFDM data unit  300 , OFDM data unit  400 , OFDM data unit  500 , or OFDM data unit  600 . In some embodiments and/or scenarios, the OFDM data units include an MPDU having a reduced header length using a BSS color identifier or other suitable non-unique identifier for the corresponding access point, for example, the MPDU  800 . In an embodiment, for example, the OFDM data units include scheduling frames for uplink orthogonal frequency division multiple access (OFDMA). In some embodiments and/or scenarios, the OFDM data unit includes the BSS color identifier in a PHY field, for example, the HE signal field  608  of the data unit  600 . 
     The first access point  902  and the second access point  904  provide service coverage area  912  and service coverage area  914 , respectively. The service coverage area  912  and service coverage area  914  each represent respective physical regions within which a client station may receive and decode transmissions from the corresponding access point, for example, broadcast management frames or downlink data frames provided by the access point. In the example embodiment shown in  FIG. 9 , the service coverage area  912  at least partially overlaps with the service coverage area  914 , the client station  922  is located within an overlapping region  916 , and the client station  922  is associated with a wireless local area network provided by the first access point  902 . 
     In some scenarios, the client station  922  receives an OFDM data unit that includes the BSS color identifier to indicate the transmitter of the OFDM data unit. In one such scenario, the client station  922  cannot readily determine which access point transmitted the OFDM data unit if both the first access point  902  and the second access point  904  have a same value for their respective BSS color identifiers (e.g., a “color collision”). In an embodiment, the client station  922  determines that the first access point  902  and the second access point  904  have the same value for their respective BSS color identifiers and generates a notification frame for the first access point  902  to cause a change in the BSS color identifier of the first access point  902 . In an embodiment, the first access point  902  determines a new value for its BSS color identifier and changes the BSS color identifier, as described below. 
     In some embodiments, the system  900  also includes a network management device  930 . In an embodiment, the network management device  930  is implemented as an instance of the access point  14  described above with reference to  FIG. 1 . In another embodiment, the network management device  930  is a network server or other suitable computing device. The network management device  930 , when present in the system  900 , manages the allocation of BSS color identifiers to access points within the system  900 . In an embodiment, the first access point  902  sends an indication of a color collision to the network management device  930 . In this embodiment, the network management device  930  determines a new value for the BSS color identifier for the first access point  902 . In other embodiments, the network management device  930  selects a new value for the BSS color identifier for the second access point  904 . 
       FIG. 10  is a diagram of a sequence of OFDM data units  1000  transmitted by the first access point  902  for a change in the BSS color identifier of the first access point  902 , according to an embodiment. In some embodiments, the OFDM data units  1000  are notification frames. In an embodiment, at least some of the notification frames are beacon management frames transmitted at predetermined beacon intervals. In various embodiments, a current value of the BSS color identifier is included in the frame body of the beacon management frame, for example, within the frame body  718  or frame body  818 . In an embodiment, for example, the BSS color identifier is included in an HE Operation element of the beacon management frame. In other embodiments, a suitable location other than the HE Operation element includes the BSS color identifier. 
     In the embodiment illustrated in  FIG. 10 , the sequence of OFDM data units  1000  includes a beacon management frame  1002 , one or more notification frames  1004 , and a beacon management frame  1006 . The first access point  902  transmits the beacon management frame  1002 , which includes a first value of the BSS color identifier of the first access point  902  and a first BSSID of the first access point  902 . In an embodiment, the client station  922  associates with the first access point  902 . In an embodiment, the client station  922  receives and decodes the beacon management frame from the second access point  904  and determines that the first access point  902  and the second access point  904  have the same value for their respective BSS color identifiers (e.g., a color collision). In an embodiment, for example, the client station  922  receives an OFDM data unit or beacon management frame (not shown), transmitted by the second access point  904 , that indicates a BSSID of the second access point  904  and the BSS color identifier of the second access point  904 . 
     In some embodiments, the client station  922  generates a BSS color collision notification frame  1003  for the first access point  902  in response to the determination of the color collision. In an embodiment, the BSS color collision notification frame  1003  provides a report of neighboring BSS color identifiers and/or neighboring BSSIDs. In an embodiment, the BSS color collision notification frame  1003  includes an indication that the BSS color identifier for the first access point  902  and the BSS color identifier for the second access point  904  have the same first value (e.g., a color collision indication). In an embodiment, the BSS color collision notification frame  1003  includes the color collision indication and the BSSID of the second access point  904 . In an embodiment, the BSS color collision notification frame  1003  includes the color collision indication and a set of BSS color identifier values detected by the client station  922 , for example, an “occupied” set of values. The client station  922  transmits the BSS color collision notification frame  1003  to the first access point  902 . In some embodiments, the access point  902  itself detects that the BSS color identifier for the second access point  904  has the same first value as the access point  902 . 
     In various embodiments, the first access point  902  determines a second value for its BSS color identifier in response to the BSS color collision notification frame  1003 . In some embodiments, the first access point  902  selects a second value that is different from the first value. For example, the first access point  902  selects a random value that is different from the first value, adds a predetermined offset to the first value, or selects another suitable value, in various embodiments. In another embodiment, the first access point  902  selects a second value that is not within the set of BSS color identifier values detected by the client station  922  or the access point  902  itself. In yet another embodiment, the first access point  902  transmits the first value and the set of BSS color identifier values to the network management device  930  and receives the second value from the network management device  930 . 
     After the determination of the second value, the first access point  902  generates one or more notification frames  1004  that indicate i) the second value of the first BSS color identifier, and ii) a start time at which the second value will supersede the first value (e.g., a subsequent changeover to the second value), in various embodiments. The notification frames  1004  generally indicate to client stations associated with the first access point  902  that a changeover will occur, while still using the first value of the BSS color identifier. 
     In some embodiments, the start time corresponds to a predetermined integer number of beacon intervals (BIs). In an embodiment, the start time is based on a backoff or delay to reduce the likelihood of a simultaneous change in the BSS color identifier for multiple access points. In the embodiment shown in  FIG. 10 , the first access point  902  generates four beacon management frames  1004 - 1 ,  1004 - 2 ,  1004 - 3 , and  1004 - 4  to notify client stations of the change of the BSS color identifier and the number of BIs before the new BSS color is used. Each of the beacon management frames  1004  i) identifies the first value of the first BSS color identifier as the transmitter of beacon management frame, ii) indicates the second value, and iii) indicates the start time at which the second value will supersede the first value for subsequent beacon management frames. On or after the start time, the first access point  902  transmits a beacon management frame  1006  that identifies the second value of the first BSS color identifier as the transmitter of beacon management frame  1006 . In some embodiments, the start time is immediately after the determination of the second value. In an embodiment, for example, the predetermined integer number of beacon intervals indicated by the beacon management frame is zero. 
     As discussed above, in an embodiment, the first value of the BSS color identifier is included in the HE Operation element of the beacon management frames  1004 . In an embodiment, the second value is included in a Color Change element within the frame body of the beacon management frames  1004 . In various embodiments, the Color Change element includes a new color field that indicates the second value and a start time field. In an embodiment, the start time field indicates an effective target beacon transmission time for the beacon management frame  1006 . In an embodiment, for example, the start time field of each of the beacon management frames  1004  indicates an integer number of remaining beacon intervals until the second value supersedes the first value (e.g., beacon management frame  1004 - 1  indicates an integer value of 4, beacon management frame  1004 - 2  indicates an integer value of 3, beacon management frame  1004 - 3  indicates an integer value of 2, and beacon management frame  1004 - 4  indicates an integer value of 1). In another embodiment, the start time field indicates a timing synchronization function (TSF) time. 
       FIG. 11  is a diagram of a sequence of OFDM data units  1100  transmitted by the first access point  902  for a change in the BSS color identifier of the first access point  902 , according to another embodiment. In some embodiments, the OFDM data units  1100  include beacon management frames  1102 ,  1104 , and  1106  and an integer number of BSS color change notification frames  1105 . The beacon management frames  1102 ,  1104 , and  1106  are transmitted at predetermined beacon intervals. In various embodiments, a current value of the BSS color identifier is included in the frame body of the beacon management frames  1102 ,  1104 , and  1106 , for example, within the frame body  718  or frame body  818 . 
     The first access point  902  transmits the beacon management frame  1102 , which includes a first value of the BSS color identifier of the first access point  902  and a first BSSID of the first access point  902 . In an embodiment, the client station associates with the first access point  902 . In an embodiment, the client station  922  receives and decodes the beacon management frame from the second access point  904  and determines that the first access point  902  and the second access point  904  have the same value for their respective BSS color identifiers (e.g., a color collision). In some embodiments, the client station  922  generates and transmits a BSS color collision notification frame  1103  for the first access point  902  in response to the determination of the color collision, as described above with respect to  FIG. 10 . 
     In various embodiments, the first access point  902  determines a second value for its BSS color identifier in response to the BSS color collision notification frame  1103 , as described above with respect to  FIG. 10 . In the embodiment shown in  FIG. 11 , after determining the second value for the BSS color identifier, the first access point  902  performs a changeover to the second value and begins generating beacon management frames with the second value. For example, after the determination of the second value, the first access point  902  generates the beacon management frame  1104 , which identifies the second value of the first BSS color identifier as the transmitter of beacon management frame  1104 . Accordingly, a first beacon management frame, generated at a beacon interval that occurs first after the determination of the second value, indicates that the first access point  902  is identifiable by the second value. 
     The first access point  902  generates one or more BSS color change notification frames that indicate the changeover from the first value to the second value, in various embodiments. In some embodiments, the first access point  902  generates a plurality of BSS color change notification frames within one or more beacon intervals after the changeover. In an embodiment, the first access point  902  transmits each of the plurality of BSS color change notification frames  1105  between i) the beacon interval of the predetermined beacon intervals that occurs first after the determining of the second value of the first BSS color identifier (e.g., the beacon interval corresponding to the beacon management frame  1104 ), and ii) a beacon interval of the predetermined beacon intervals that occurs second after the determining of the second value of the first BSS color identifier (e.g., the beacon interval corresponding to the beacon management frame  1106 ). In the embodiment shown in  FIG. 11 , the first access point  902  generates three BSS color change notification frames  1105 - 1 ,  1105 - 2 , and  1105 - 3  and transmits each of the BSS color change notification frames within a single beacon interval. The first access point  902  uses other suitable numbers of BSS color change notification frames and other suitable numbers of beacon intervals, in various embodiments. 
       FIG. 12  is a flow diagram illustrating an example method  1200  for changing a first basic service set (BSS) color identifier for a first communication device, according to an embodiment. With reference to  FIG. 1 , the method  1200  is implemented by the network interface  16 , in an embodiment. For example, in one such embodiment, the PHY processing unit  20  is configured to implement the method  1200 . According to another embodiment, the MAC processing  18  is also configured to implement at least a part of the method  1200 . With continued reference to  FIG. 1 , in yet another embodiment, the method  1200  is implemented by the network interface  27  (e.g., the PHY processing unit  29  and/or the MAC processing unit  28 ). In other embodiments, the method  1200  is implemented by other suitable network interfaces. 
     At block  1202 , an indication that the first BSS color identifier for the first communication device and a second BSS color identifier for a second communication device have a same first value is received. In an embodiment, the indication comprises the BSS color collision notification frame  1003 , as described above with respect to  FIG. 10 . In an embodiment, the indication is received by the first access point  902 , the second access point  904 , or another suitable communication device. As described above, the first access point  902  is identifiable by i) the first BSS color identifier, and ii) the first BSSID having a length that is longer than a length of the first BSS color identifier. In an embodiment, a first service coverage area of the first communication device at least partially overlaps a second service coverage area of the second communication device. 
     At block  1204 , a second value of the first BSS color identifier is determined in response to the indication received in block  1202 . In an embodiment, the determination corresponds to the determination of the second value by the first access point  902 , as described above with respect to  FIG. 10 . 
     At block  1206 , one or more BSS color change notification frames are generated that indicate i) the second value of the first BSS color identifier, and ii) a start time at which the second value will supersede the first value of the first BSS color identifier. In an embodiment, the BSS color change notification frames include the beacon management frames  1004 , as described above with respect to  FIG. 10 . In another embodiment, the BSS color change notification frames include the notification frames  1105 , as described above with respect to  FIG. 11 . 
     At block  1208 , the first BSS color identifier is changed to the second value based on the start time. 
       FIG. 13  is a flow diagram illustrating an example method  1300  for causing a change of a first BSS color identifier for a first communication device, according to an embodiment. With reference to  FIG. 1 , the method  1300  is implemented by the network interface  16 , in an embodiment. For example, in one such embodiment, the PHY processing unit  20  is configured to implement the method  1300 . According to another embodiment, the MAC processing  18  is also configured to implement at least a part of the method  1300 . With continued reference to  FIG. 1 , in yet another embodiment, the method  1300  is implemented by the network interface  27  (e.g., the PHY processing unit  29  and/or the MAC processing unit  28 ). In other embodiments, the method  1300  is implemented by other suitable network interfaces. 
     At block  1302 , a first indication is received from a second communication device and by a third communication device. The first indication indicates that the second communication device is identifiable by i) a first BSS color identifier, and ii) a second BSSID. In an embodiment, the first indication is a beacon management frame received by the client station  922 , for example, a beacon management frame  1002  transmitted by the second access point  904 . 
     At block  1304 , a second indication is received from a first communication device and by the third communication device. The second indication indicates that the second communication device is identifiable by i) a first BSS color identifier, and ii) a second BSSID. In an embodiment, the second indication is a beacon management frame received by the client station  922 , for example, a beacon management frame  1002  transmitted by the first access point  902 . In an embodiment, a first service coverage area of the first communication device at least partially overlaps a second service coverage area of the second communication device. 
     At block  1306 , it is determined that the first BSS color identifier for the first communication device and the second BSS color identifier for the second communication device have a same first value. 
     At block  1308 , a notification frame is generated for the first communication device to cause a change of the first BSS color identifier. In an embodiment, the notification frame includes i) an indication that the first BSS color identifier for the first communication device and the second BSS color identifier for the second communication device have the same first value, and ii) the second BSSID. In an embodiment, the notification frame is the BSS color collision notification frame  1003 , as described above with respect to  FIG. 10 . In another embodiment, the notification frame is the BSS color collision notification frame  1103 , as described above with respect to  FIG. 11 . 
     At least some of the various blocks, operations, and techniques described above may be implemented utilizing hardware, a processor executing firmware instructions, a processor executing software instructions, or any combination thereof. When implemented utilizing a processor executing software or firmware instructions, the software or firmware instructions may be stored in any computer readable memory such as on a magnetic disk, an optical disk, or other storage medium, in a RAM or ROM or flash memory, processor, hard disk drive, optical disk drive, tape drive, etc. Likewise, the software or firmware instructions may be delivered to a user or a system via any known or desired delivery method including, for example, on a computer readable disk or other transportable computer storage mechanism or via communication media. Communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism. The term “modulated data signal” means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, radio frequency, infrared and other wireless media. Thus, the software or firmware instructions may be delivered to a user or a system via a communication channel such as a telephone line, a DSL line, a cable television line, a fiber optics line, a wireless communication channel, the Internet, etc. (which are viewed as being the same as or interchangeable with providing such software via a transportable storage medium). The software or firmware instructions may include machine readable instructions that, when executed by the processor, cause the processor to perform various acts. 
     When implemented in hardware, the hardware may comprise one or more of discrete components, an integrated circuit, an application-specific integrated circuit (ASIC), etc. 
     While the present invention has been described with reference to specific examples, which are intended to be illustrative only and not to be limiting of the invention, changes, additions and/or deletions may be made to the disclosed embodiments without departing from the scope of the invention.