VHT operation information subfield design in WLAN
A method of very high throughput (VHT) operation information subfields design for IEEE 802.11 WLAN is proposed. The VHT operation information subfields comprise a channel width, a channel center frequency segment 0 (CCFS 0 ), and a channel center frequency segment 1 (CCFS 1 ). Multiple definitions of the VHT operation information subfields have been adopted by different access points (AP)s and wireless stations (STAs). In accordance with one novel aspect, upon receiving the VHT operation information element broadcasted by an AP, an STA will first check the channel width indicated by the AP. The STA then follows different definitions under different channel widths. Under such method, the STA can support up to 160 MHz operation mode with APs following different definitions and operating up to 160 MHz mode.
1. A method comprising:
receiving a beacon frame broadcasted from an access point (AP) by a wireless station (STA) in a wireless local area network (WLAN), wherein the beacon frame comprises a very high throughput (VHT) operation information element, and wherein the AP uses a first center frequency value to indicate the center frequency for both 80 MHz and 160 MHz channel widths;
determining a BSS channel width of a basic service set (BSS) based on the VHT operation information element, wherein the VHT operation information element comprises:
a channel width subfield;
the first center frequency value; and
a second center frequency value;
determining a center frequency of the STA based on the first center frequency value if the channel width is equal to a first set of predefined values, and the BSS operating channel width is 160 MHz, wherein said determining comprises:
adopting the first center frequency as the center frequency if the operating channel width of the STA is 80 MHz;
determining the center frequency based on the second center frequency value if the channel width is equal to a second set of predefined values and the STA has an operating channel width same as the BSS operating channel width, wherein said determining comprises:
adopting the second center frequency value as the center frequency if the second center frequency value is non-zero and the operating channel width of the STA is 160 MHz; and
adopting the first center frequency value as the center frequency for a primary 80 MHz channel and adopting the second center frequency value as the center frequency for a secondary 80 MHz channel when the operating channel width of the STA is 80+80 MHz; and
determining the center frequency based on a different VHT operation element definition if the channel width subfield is set to a value other than 160 MHz or 80+80 MHz.
2. The method of claim 1 , further comprising the AP using the first center frequency value and the second center frequency value to indicate the center frequency for 80 MHz and 160 MHz channel widths respectively.
3. The method of claim 1 , wherein the BSS channel width is equal to the first set of predefined values, and the BSS channel width is one of 160 MHz and 80+80 MHz.
4. The method of claim 3 , further comprising the STA adopting the first center frequency value if the operating channel width of the STA is 160 MHz.
5. The method of claim 1 , wherein the BSS channel width is equal to the second set of predefined values.
6. The method of claim 5 , further comprising the STA adopting the first center frequency value as the center frequency if the second center frequency value is zero.
7. A wireless station (STA), comprising:
a receiver operable to receive a beacon frame broadcast from an access point (AP) in a wireless local area network (WLAN), wherein the beacon frame comprises a very high throughput (VHT) operation information element, wherein the AP is operable to use a first center frequency value to indicate the center frequency for both 80 MHz and 160 MHz channel widths;
a decoder operable to decode a BSS channel width of a basic service set (BSS) based on the VHT operation information element, wherein the VHT operation information element further comprises:
a channel width subfield;
the first center frequency value; and
a second center frequency value; and
a radio frequency (RF) transceiver operable to:
determine a center frequency of the STA based on the first center frequency value if the BSS channel width is equal to a first set of predefined values, and the BSS operating channel width is 160 MHz, wherein said determining comprises:
adopting the first center frequency as the center frequency if the operating channel width of the STA is 80 MHz;
determine the center frequency based on the second center frequency value if the BSS channel width is equal to a second set of predefined values and the STA has an operating channel width that is equal to the BSS channel width, wherein said determining comprises:
adopting the second center frequency value as the center frequency if the second center frequency value is non-zero and the operating channel width of the STA is 160 MHz; and
adopting the first center frequency value as the center frequency for a primary 80 MHz channel and adopting the second center frequency value as the center frequency for a secondary 80 MHz channel when the operating channel width of the STA is 80+80 MHz; and determine the center frequency based on a different VHT operation element definition if the channel width subfield is set to a value other 160 MHz or 80+80 MHz.
8. The wireless STA of claim 7 , wherein the AP is operable to use the first center frequency value and the second center frequency value to indicate the center frequency for 80 MHz and 160 MHz channel widths respectfully.
9. The wireless STA of claim 7 , wherein the first center frequency value is adopted as the center frequency if the operating channel width of the STA is 160 MHz.
10. The wireless STA of claim 7 , wherein the BSS channel width is equal to the second set of predefined values.
11. The wireless STA of claim 10 , wherein the first center frequency value is adopted as the center frequency if the second center frequency value is zero.