Slotted OFDMA based channel access
地域：
Guangdong
摘要
Access to a wireless medium is controlled based on contention arbitration. A certain number of wireless devices are allowed by an access point to contend for a transmission opportunity. A trigger frame is used to communicate access opportunities to multiple devices. A beacon transmission may additionally be used for communication of access opportunities.
說明書
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This patent document claims the benefit of priority U.S. Provisional Patent Application No. 62/423,659, filed on Nov. 17, 2016. The entire content of the before-mentioned patent application is incorporated by reference as part of the disclosure of this document.
This patent document relates to wireless communication, and in particular, access to a wireless transmission medium by multiple wireless devices.
Wireless communication systems can include a network of one or more access points (AP) to communicate with one or more wireless stations (STA). An access point can emit radio signals that carry management information, control information, or users' data to one or more wireless stations, and a station can also transmit radio signals to the access point in the same frequency channel via time division duplexing (TDD) or in different frequency via frequency division duplexing (FDD).
IEEE 802.11 is an asynchronous time division duplexing technology designated for wireless local area network (WLAN). The basic unit of WLAN is a basic service set (BSS). The infrastructure BSS is the BSS with stations through associating with an Access Point (AP) to connect to the wired network or Internet. In a BSS, both access point and stations share the same frequency channel via using Carrier Sensing Multiple Access with Collision Avoidance (CSMA/CA) technology, a kind of TDD mechanism, for multiple access and data transmission.
權(quán)利要求
What is claimed is what is described and illustrated, including:1. A method of controlling operation of a wireless network comprising an access point and a plurality of stations, comprising:transmitting, by the access point, a control message comprising a parameter indicating start of an uplink multiuser channel access transmission opportunity (CA-TXOP) during which multiple of the plurality of stations are permitted to attempt uplink transmissions using orthogonal frequency division multiplexing access (OFDMA),wherein the control message includes a minimum contention window size (CWmin) and a maximum contention window size (CWmax) used for channel access, and wherein a backoff counter value of the channel access is in range [0, CW?1], where CW is initially within a range of the CWmin to the CWmax; receiving a number of response messages from the multiple stations during a channel access slot in the uplink multiuser channel access transmission opportunity; and transmitting, based on identities of stations that sent the response messages, an acknowledgement message identifying which of the multiple stations have succeeded. 2. The method of claim 1 , wherein the control message includes at least some of the following fields: a duration of the CA-TXOP, a number channel access slots, a duration of each channel access slot, and a trigger response acknowledgement policy. 3. The method of claim 1 , further comprising:switching, after transmitting the control message, to a receiving mode to detect response messages within a time period after a channel access opportunity begins, and when no response messages are detected, sending a next control message instead of waiting until end of current channel access opportunity duration. 4. The method of claim 1 , further including:changing values of the CWmin and the CWmax based on a network load condition. 5. The method of claim 1 , wherein transmitting the control message includes:identifying a set of stations from the plurality of stations that are permitted to contend in a medium in the CA-TXOP. 6. The method of claim 1 , wherein receiving the number of response messages includes:monitoring a wireless channel for a first legacy preamble; and decoding one or more response messages transmitted over OFDMA sub-channels when the first legacy preamble is detected. 7. The method of claim 6 , wherein the first legacy preamble includes legacy short training field (L-STF), legacy long training field (L-LTF) and legacy signal field (L-SIG). 8. The method of claim 1 , wherein transmitting the acknowledgement message includes:deferring transmission of the acknowledgement message when a trigger response acknowledgement policy is set to a deferred state; and combining all acknowledgements into a single message. 9. The method of claim 1 , wherein the control message is transmitted periodically or aperiodically based on an operating condition of the wireless network. 10. The method of claim 1 , further comprising:transmitting at least one channel access parameter indicative of a characteristic of the control message in a beacon frame transmission. 11. The method of claim 1 , further including:detecting collisions while receiving the number of response messages; and transmitting an indication to increase backoff in a next channel access transmission opportunity (CA-TXOP) or a next control message transmission. 12. The method of claim 5 , wherein the control message further includes a special station identifier to allow all capable stations to access to the channel access slot or a list of identifiers for one or more specified station to access to the channel access slot. 13. An apparatus for controlling operation of a wireless network comprising an access point and a plurality of stations, the apparatus comprising:a memory that stores instructions; and a processor that reads the instructions from the memory and implements a method of controlling operation of the wireless network, the instructions comprising: instructions for transmitting, by the access point, a control message comprising a parameter indicating start of an uplink multiuser channel access transmission opportunity (CA-TXOP) during which multiple of the plurality of stations are permitted to attempt uplink transmissions using orthogonal frequency division multiplexing access (OFDMA),wherein the control message includes a minimum contention window size (CWmin) and a maximum contention window size (CWmax) used for channel access, and wherein a backoff counter value of the channel access is in range [0, CW?1], where CW is initially within a range of the CWmin to the CWmax; instructions for receiving a number of response messages at a channel access slot in the CA-TXOP; and instructions for transmitting, based on identities of stations that sent the number of response messages, an acknowledgement message identifying stations allowed to transmit in an extended TXOP. 14. The apparatus of claim 13 , wherein the control message includes at least some of the following fields: a duration of the CA-TXOP, a number channel access slots of the CA-TXOP, a duration of each channel access slot, and a trigger response acknowledgement policy. 15. The apparatus of claim 13 , wherein the instructions further include:instructions for identifying a set of stations from the plurality of stations that are permitted to contend in the medium in the CA-TXOP. 16. The apparatus of claim 13 , wherein the instructions further include:instructions for monitoring a wireless channel for a first legacy preamble; and instructions for decoding one or more response messages transmitted over OFDMA sub-channels when the first legacy preamble is detected. 17. The apparatus of claim 16 , wherein the first legacy preamble includes legacy short training field (L-STF), legacy long training field (L-LTF) and legacy signal field (L-SIG). 18. The apparatus of claim 13 , wherein the instructions further include:instructions for deferring transmission of the acknowledgement message when a trigger response acknowledgement policy is set to a deferred state; and instructions for combining all acknowledgements into a single message. 19. The apparatus of claim 13 , wherein the instructions further include:instructions for detecting collisions while receiving the number of response messages; and instructions for transmitting an indication to increase backoff in a next RX-TXOP or a next control message transmission. 20. The apparatus of claim 13 , wherein the instructions further include:instructions for switching, after transmitting the control message, to a receiving mode to detect response messages within a time period after a channel access opportunity begins, and when no response messages are detected, sending a next control message instead of waiting until end of current channel access opportunity duration. 21. The apparatus of claim 15 , wherein the instructions further include instructions for transmitting a special station identifier to allow all capable stations to access to the channel access slot or a list of identifiers for one or more specified station to access to the channel access slot. 22. A method of controlling operation of a wireless network comprising an access point and a plurality of wireless stations, the method comprising:receiving, by a wireless station, a control message comprising a parameter indicating start of an uplink multiuser channel access transmission opportunity (CA-TXOP) during which multiple of the plurality of wireless stations are permitted to attempt uplink transmissions using orthogonal frequency division multiplexing access (OFDMA); transmitting, by the wireless station, a response message at a channel access slot specified in the CA-TXOP, wherein transmitting the response message includes:setting a backoff counter to an integer value, decreasing the backoff counter after each CA-TXOP duration after receiving the control message, and selectively transmitting the response message after a shortened time interval after a prior CA-TXOP designated for another wireless station when the backoff counter has reached zero and no transmission is detected in the prior CA-TXOP after a shortened time duration; and receiving, for the response message, an acknowledgement message identifying the corresponding response transmission success. 23. The method of claim 22 , wherein the control message includes at least some of the following fields: a duration of the CA-TXOP, a number channel access slots of the CA-TXOP, a duration of each channel access slot, minimum and maximum contention windows sizes used for channel access, and a trigger response acknowledgement policy. 24. The method of claim 22 , further comprising:transmitting user data in an extended TXOP in accordance with the received acknowledgement message. 25. An apparatus for controlling operation of a wireless network comprising an access point and a plurality of stations, the apparatus comprising:a memory that stores instructions; and a processor that reads the instructions from the memory and implements a method of controlling operation of the wireless network, the instructions comprising: instructions for receiving, by a wireless station, a control message comprising a parameter indicating start of an uplink multiuser channel access transmission opportunity (CA-TXOP) during which multiple of the plurality of wireless stations are permitted to attempt uplink transmissions using orthogonal frequency division multiplexing access (OFDMA); instructions for transmitting, by the wireless station, a response message at a channel access slot specified in the CA-TXOP, wherein the instructions for transmitting the response message includes:instructions for setting a backoff counter to an integer value, instructions for decreasing the backoff counter after each CA-TXOP duration after receiving the control message, and instructions for selectively transmitting the response message after a shortened time interval after a prior CA-TXOP designated for another wireless station when the backoff counter has reached zero and no transmission is detected in the prior CA-TXOP after a shortened time duration; instructions for receiving, for the response message, an acknowledgement message identifying the corresponding response received successfully; and instructions for transmitting user data in an extended TXOP in accordance with the received acknowledgement message. 26. The apparatus of claim 25 , wherein the control message includes at least some of the following fields: a duration of the CA-TXOP, a number channel access slots of the CA-TXOP, a duration of each channel access slot, minimum and maximum contention windows sizes used for channel access, and a trigger response acknowledgement policy. 27. A wireless communication network comprising an access point and multiple wireless stations,wherein the access point stores, in a first memory, instructions causing the access point to:transmit a control message comprising a parameter indicating start of an uplink multiuser channel access transmission opportunity (CA-TXOP) during which multiple of the plurality of stations are permitted to attempt uplink transmissions using orthogonal frequency division multiplexing access (OFDMA),wherein the control message includes a minimum contention window size (CWmin) and a maximum contention window size (CWmax) used for channel access, and wherein a backoff counter value of the channel access is in range [0, CW?1], where CW is initially within a range of the CWmin to the CWmax; receive a number of response messages from the multiple stations during a channel access slot in the CA-TXOP; and transmit, based on identities of stations that sent the response messages, an acknowledgement message identifying which of the multiple stations have succeeded and are allowed to transmit in an upcoming arbitrated contention-free transmission opportunity; and wherein each of the plurality of wireless stations stores, in a second memory, instructions causing each of the plurality of wireless station to:receive the control message; transmit a corresponding response message over OFDMA sub-channel at a channel access slot specified in the CA-TXOP, wherein the transmit the corresponding response message includes:set a backoff counter to an integer value, decrease the backoff counter after each CA-TXOP duration after receiving the control message, and selectively transmit the response message after a shortened time interval after a prior CA-TXOP designated for another wireless station when the backoff counter has reached zero and no transmission is detected in the prior CA-TXOP after a shortened time duration; and receive an acknowledgement message identifying the corresponding response received successfully. 28. The wireless communication network of claim 27 , wherein the control message includes at least some of the following fields: a duration of the CA-TXOP, one or more channel access slots of the CA-TXOP, a duration of each channel access slot, and a trigger response acknowledgement policy. 29. The wireless communication network of claim 27 , wherein each of the plurality of wireless stations stores, in the second memory, instructions causing each of the plurality of wireless stations further to:transmit user data in the an extended TXOP in accordance with the received acknowledgement message.
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