WO2013143355A1 - 下行数据碰撞避免的方法、接入点和站点 - Google Patents

下行数据碰撞避免的方法、接入点和站点 Download PDF

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Publication number
WO2013143355A1
WO2013143355A1 PCT/CN2013/070830 CN2013070830W WO2013143355A1 WO 2013143355 A1 WO2013143355 A1 WO 2013143355A1 CN 2013070830 W CN2013070830 W CN 2013070830W WO 2013143355 A1 WO2013143355 A1 WO 2013143355A1
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Prior art keywords
station
frame
radio frame
channel
time
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Ceased
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PCT/CN2013/070830
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English (en)
French (fr)
Inventor
韩志强
吕开颖
孙波
田开波
邢卫民
李楠
杨丹
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ZTE Corp
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ZTE Corp
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Priority to US14/387,578 priority Critical patent/US9345042B2/en
Priority to EP13768870.1A priority patent/EP2816860B1/en
Publication of WO2013143355A1 publication Critical patent/WO2013143355A1/zh
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W74/00—Wireless channel access
    • H04W74/08—Non-scheduled access, e.g. ALOHA
    • H04W74/0808—Non-scheduled access, e.g. ALOHA using carrier sensing, e.g. carrier sense multiple access [CSMA]
    • H04W74/0816—Non-scheduled access, e.g. ALOHA using carrier sensing, e.g. carrier sense multiple access [CSMA] with collision avoidance
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/50—Allocation or scheduling criteria for wireless resources
    • H04W72/535—Allocation or scheduling criteria for wireless resources based on resource usage policies
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/1607—Details of the supervisory signal
    • H04L1/1685—Details of the supervisory signal the supervisory signal being transmitted in response to a specific request, e.g. to a polling signal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1829—Arrangements specially adapted for the receiver end
    • H04L1/1835—Buffer management
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1829—Arrangements specially adapted for the receiver end
    • H04L1/1854—Scheduling and prioritising arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1829—Arrangements specially adapted for the receiver end
    • H04L1/1864—ARQ related signaling
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/08—Access point devices
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/1607—Details of the supervisory signal
    • H04L1/1614—Details of the supervisory signal using bitmaps
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/10—Small scale networks; Flat hierarchical networks
    • H04W84/12—WLAN [Wireless Local Area Networks]

Definitions

  • the present invention relates to the field of wireless communications, and in particular, to a method, a point of access, and a point of occupying downlink data collision avoidance. Background technique
  • wireless local area networks WLANs
  • IEEE Institute of Electrical and Electronics Engineers
  • 802.11 group has promulgated 802.11a, 802.11b, 802. l lg, 802.11 ⁇ and other series of WLAN technology standards, and then set up other task groups to develop specifications for designing existing 802.11 technology improvements.
  • IEEE established the 802.1 lah task group. Its main task is to modify and enhance the medium access control (MAC) layer and physical (PHY) layer of the WLAN to adapt to Smart Grid, Sensor Network, and Environmental/Agricultural Monitoring ), industrial process automation 4 (industrial Process Automation) and other network requirements.
  • MAC medium access control
  • PHY physical
  • an access point (AP) and a plurality of non-AP stations (STAs) associated with the AP form a basic service set (BSS). ).
  • the STA must complete the authentication and association process with the AP before using the service of the BSS. If the association is successful, the AP assigns an association identifier (Association Identifier, AID) to the STA.
  • the AID is the identity of the STA in the BSS. It is distinguished from other STAs in the BSS by AID, but STAs belonging to different BSSs may use the same AID.
  • multiple BSSs can be connected to each other through the Distribution System (DS) to form an Extend Service Set (ESS).
  • ESS Extend Service Set
  • Multiple STAs can also form a self-organizing wireless LAN, called Independent BSS (IBSS). In IBSS, STA can communicate directly.
  • IBSS Independent BSS
  • an Access Point and a plurality of stations (Stations, referred to as STAs) associated with an AP form a basic service set (Basic Service Set, Jane). Called BSS).
  • 802.11 defines two modes of operation: Distributed Coordination Function (DCF) and Point Coordination Function (PCF), and improvements for these two modes of operation: Enhanced Distributed Channel Access (Civilized Distributed Channel Access, EDCA for short) and Hybrid Coordination Function Controlled Channel Access (HCCA).
  • DCF is the most basic mode of operation, and multiple stations share wireless channels by using CSMA with Collision Avoidance (CSMA/CA) with collision avoidance.
  • EDCA is an enhanced mode of operation that maps upper-level data to four different Access Categories: AC—VO, AC—VI, AC—BE, AC—BK, each queue category uses a different competition The parameters of the channel are used to prioritize.
  • EDCA uses the CSMA/CA mechanism to allow multiple different priority queues to share wireless channels and to reserve a Transmission Opportunity (TXOP).
  • TXOP Transmission Opportunity
  • the basic process for obtaining transmission opportunities for different priority queues is as follows: Each queue uses a different backoff interval plus any contention backoff window to access the channel when the channel is idle to reduce collisions.
  • the other listening site that receives the radio frame with the time reservation information sets a network Allocation Vector (NAV) stored locally, and the value of the NAV is set to the maximum value of the channel reservation time information and the retained time information. During this time, the listening site will not send data, thus avoiding the problem of hidden sites competing for channels and causing collisions. After NAV is reduced to zero, other sites can send data.
  • the sender may first send a request to send (RTS) for channel reservation, which includes channel reservation time information.
  • RTS request to send
  • the receiver performs channel reservation confirmation in response to the Clear to Send (CTS), which also includes channel reservation time information to protect the subsequent transmission of the radio frame.
  • CTS Clear to Send
  • IEEE802.il defines two modes of energy management: Active Mode (AM) And power saving mode (Power Saving, PS).
  • the AP For the site in the power-saving mode, the AP carries the service indication information, that is, the Traffic Indication Map (TIM) information element, to notify the stations in the power-saving mode whether the site is in the power-saving mode.
  • the Bufferable Unit is pending. If these sites find a cache unit, the AP can reply to an acknowledgment (ACK) frame or directly reply to the data frame by sending a power save inquiry frame (PS-Poll).
  • ACK acknowledgment
  • PS-Poll power save inquiry frame
  • the PS-Poll For a long-sleeping site waking up, the PS-Poll frame is actively sent, and the AP responds by sending an ACK carrying a downlink service indication or directly transmitting a data frame.
  • the embodiment of the present invention provides a method, an access point, and a site for collision avoidance of a downlink data, to solve the problem that a collision occurs on the STA side when the STA sends a PS-Poll frame and returns a longer frame.
  • the embodiment of the invention provides a method for collision avoidance of downlink data, including:
  • An access point ( ⁇ ) a radio frame sent by the receiving station to query whether the ⁇ has a cache unit of the station;
  • a radio frame exchange reservation channel is performed with the station, and the cache unit is sent to the station after the channel reservation is successful.
  • the predetermined threshold is a value negotiated between the UI and the site during the association process or the re-association process, or a value indicated by the capability information element of the broadcast frame initiated by the UI, or the The value indicated in the capability negotiation by the site, or the default value of the system where the ⁇ is located.
  • step of performing a radio frame exchange reservation channel with the station, and the step of sending the cache unit to the station after the channel reservation is successful includes:
  • the reserved channel time included in the RTS frame is set to a transmission time of one or more buffer units to be transmitted, a time of a required response, and a radio frame in which the buffer unit is located and a radio frame in which the response is located.
  • the sum of the frame intervals, the response includes an immediate response and/or a delayed response, and the time cutoff point of the reserved channel time included in the CTS frame is the same as the time cutoff point of the reserved channel time included in the RTS frame.
  • the embodiment of the invention further provides a method for collision avoidance of downlink data, including:
  • the station in the power save mode sends a radio frame to the access point (AP) for inquiring whether the AP has a cache unit of the station;
  • the station cooperates with the AP to complete a radio frame exchange reservation channel, and receives the cache unit sent by the AP by using a channel that is successfully reserved.
  • the step of the station sending a radio frame to the AP includes:
  • the station actively sends the radio frame to the AP;
  • the station After the station listens to the service indication information sent by the AP, the station sends the radio frame to the AP.
  • the total transmission duration of the frame exchange sequence from the radio frame is limited by the attributes of the station.
  • the attributes of the station include access category parameters corresponding to the radio frame.
  • the total transmission duration is a total time of a radio frame transmitted by the station, a total time of a radio frame transmitted by the access point, and a radio frame transmitted by the station and a radio frame transmitted by the access point.
  • An embodiment of the present invention further provides an access point (AP), including:
  • a receiving module configured to receive a radio frame sent by the station for inquiring whether the AP has a cache unit of the station;
  • a processing module configured to determine that the AP has a cache unit of the station, and after the buffer unit is greater than a predetermined threshold, perform a radio frame exchange reservation channel with the station, after the channel reservation is successful Sending the cache unit to the site.
  • the predetermined threshold is a value negotiated by the AP and the site during the association process or the re-association process, or a value indicated by the capability information element of the broadcast frame initiated by the AP, or the AP and the The value indicated in the capability negotiation of the site, or the default value of the system where the AP is located.
  • the processing module is configured to: perform a channel reservation after transmitting a request to send (RTS) frame to the station; and send the cache unit to the station after receiving a grant transmission (CTS) frame returned by the station
  • RTS request to send
  • CTS grant transmission
  • the reserved channel time included in the RTS frame is set to the transmission time of one or more buffer units to be transmitted, the time of the required response, and the radio frame in which the buffer unit is located and the radio frame in which the response is located. a sum of frame intervals, the response including an immediate response and/or a delayed response, the time cutoff point of the reserved channel time included in the CTS frame being the same as the time cutoff point of the reserved channel time included in the RTS frame .
  • An embodiment of the present invention further provides a site, including:
  • a sending module configured to send, to an access point (AP), a radio frame for inquiring whether the AP has a cache unit of the station;
  • a processing module configured to complete the radio frame exchange reservation channel with the AP, and receive the cache unit sent by the AP by using a channel that is successfully reserved.
  • the sending module is configured to: actively send the radio frame to the AP; or, after periodically listening to the service indication information sent by the AP, send the radio frame to the AP.
  • the total transmission duration of the frame exchange sequence from the radio frame is limited by the attributes of the station.
  • the attributes of the station include access category parameters corresponding to the radio frame.
  • the total transmission duration is a total time of a radio frame transmitted by the station, a total time of a radio frame transmitted by the access point, and a radio frame transmitted by the station and a radio frame transmitted by the access point.
  • the foregoing method for transmitting downlink data collision avoidance can ensure fairness between each station and reasonable utilization of channel resources, thereby avoiding collision occurrence; further, after PS-Poll, the AP sends a channel reservation frame, such as an RTS frame, to reserve a segment. For a longer period of time, multiple buffer units can be sent to the STA at a time without sending a PS-Poll to each cache, thereby saving link overhead.
  • a channel reservation frame such as an RTS frame
  • Figure 1 is a schematic diagram of an existing hidden site
  • FIG. 2 is a schematic diagram of a prior art solution to a hidden site problem
  • Embodiment 1 of a method for downlink data collision avoidance according to the present invention
  • FIG. 4 is a schematic diagram 1 of the total duration of frame transmission according to the present invention.
  • FIG. 5 is a second schematic diagram of the total duration of frame transmission according to the present invention.
  • Embodiment 2 is a schematic diagram of Embodiment 2 of a method for downlink data collision avoidance according to the present invention.
  • FIG. 7 is a schematic structural diagram of an AP embodiment of the present invention.
  • FIG. 8 is a schematic structural diagram of an embodiment of a STA according to the present invention.
  • the embodiment of the invention provides a method for collision avoidance of downlink data, which is described from the perspective of a station, and the method includes:
  • Step 11 The station in the power saving mode sends a radio frame to the access point (AP) for inquiring whether the AP has a cache unit of the station;
  • the step may include: the station actively sending the radio frame to the AP; or the station sends the radio frame to the AP after periodically listening to the service indication information sent by the AP.
  • Step 12 The station cooperates with the AP to complete a radio frame exchange reservation channel, and receives the cache unit sent by the AP by using a channel that is successfully reserved.
  • the total transmission duration of the frame exchange sequence from the radio frame is limited by the attributes of the station in the obtained transmission opportunity; wherein the attribute of the station includes an access category corresponding to the radio frame
  • the total transmission duration is the total time of the radio frame transmitted by the station, The total time of the radio frame transmitted by the access point and the sum of the frame interval between the radio frame transmitted by the station and the radio frame transmitted by the access point.
  • the base station cooperates with the AP to complete the channel reservation, so that the site side can avoid collision occurrence.
  • the embodiment of the invention further provides a method for collision avoidance of downlink data, which is described from the perspective of an AP, and the method includes:
  • Step 21 The access point (AP) receives a radio frame sent by the station to query whether the AP has a cache unit of the station.
  • Step 22 After determining that the cache unit of the station is greater than the predetermined threshold, the AP performs a radio frame exchange reservation channel with the station, and sends the cache unit to the station after the channel reservation is successful.
  • the predetermined threshold is a value negotiated by the AP and the site during the association process or the re-association process, or a value indicated by the capability information element of the broadcast frame initiated by the AP, or the AP and the AP The value indicated in the capability negotiation of the site, or the default value of the system where the AP is located.
  • the step may include: the AP sending a request to send (RTS) frame to the station for channel reservation; and the AP sending the buffer unit to the station after receiving a grant transmission (CTS) frame returned by the station;
  • the reserved channel time included in the RTS frame is set to a transmission time of one or more buffer units to be transmitted, a time of a required response, and a radio frame in which the buffer unit is located and a radio frame in which the response is located.
  • the sum of the frame intervals, the response includes an immediate response and/or a delayed response, and the time cutoff point of the reserved channel time included in the CTS frame is the same as the time cutoff point of the reserved channel time included in the RTS frame.
  • the method for avoiding downlink data collision avoids, when the AP determines that the buffered data is greater than a predetermined threshold, and reserves a channel with the station, so that the channel becomes a dedicated channel between the AP and the station, thereby avoiding a collision; and, after the PS-Poll, the AP
  • the transmission channel reservation frame such as the RTS frame, can be reserved for a long period of time, that is, one time can send multiple buffer units to the STA without sending PS-Poll to each buffer unit, thereby saving link overhead.
  • This embodiment is an embodiment of a transmission method for downlink data collision avoidance using the present invention.
  • Implementing downlink data transmission in this embodiment mainly includes the following steps:
  • the site notifies or negotiates the predetermined threshold with the access point during the association process.
  • the site in the energy-saving mode wakes up actively, sends a PS-Poll frame, and asks the AP whether there is a cache unit of the site; when the AP receives the PS-Poll sent by the station in the PS mode, according to the situation of the site BU , responded:
  • the AP When the AP does not have the buffer unit of the STA, the AP sends an ACK indicating that the buffer unit is not.
  • the AP replies to the buffer unit indicating that there is an ACK, or when the buffer unit is smaller than the negotiated threshold, the AP may directly reply to the buffer unit, or when the cache unit is greater than the negotiated threshold.
  • the AP first sends an RTS for channel reservation, and the reserved channel time of the RTS is set to the time required to transmit data.
  • the station transmitting the PS-Poll When the station transmitting the PS-Poll receives the RTS frame, it will respond to the CTS frame after the short frame interval (SIFS), and the time cutoff point of the reserved channel time setting of the CTS is the same as the cutoff point set by the RTS reserved channel information.
  • the AP After receiving the CTS frame, the AP sends a buffer unit. If the cache unit needs to respond immediately, the STA responds, as shown in Figure 3.
  • the station If the station does not detect any signal within a period of time after transmitting the PS-Poll frame, or receives an error frame, it re-competes the channel.
  • the RTS frame is sent for channel reservation. If a correct CTS is received after SIFS, after a SIFS, it responds to a cache unit. After SIFS, it successfully receives an ACK, and then can continue to transmit to the cache unit of the station, but the entire transmission time (including PS) -Poll) cannot exceed the TX0P upper limit of the PS-Poll collision avoidance (AC). As shown in Figure 4, if the TXOP Limit of the PS-Poll corresponding AC is 0, only one frame exchange required by the buffer unit can be performed. Sequence transmission.
  • the PS-Poll listening site is received, and the NAV is updated according to the SIFS plus ACK transmission time.
  • the listening site successfully receives the RTS frame and performs a NAV update. If no channel is detected within a certain interval, NAV reset is performed.
  • the predetermined threshold is configured by default system parameters.
  • the station in the energy-saving mode wakes up actively, sends a PS-Poll frame, and asks the AP whether there is a cache unit of the site.
  • the AP receives the PS-Poll sent by the station in PS mode, it responds according to the situation of the site BU:
  • the AP When the AP does not have the buffer unit of the STA, the AP sends an ACK indicating that the buffer unit is not.
  • the AP replies to the buffer unit indicating that there is an ACK, or when the buffer unit is smaller than the negotiated threshold, the AP may directly reply to the buffer unit, or when the cache unit is greater than the negotiated threshold.
  • the AP first sends an RTS for channel reservation, and the reserved channel time of the RTS is set to the time required to transmit data.
  • the station transmitting the PS-Poll When the station transmitting the PS-Poll receives the RTS frame, it will respond to the CTS frame after the short frame interval (SIFS), and the time cutoff point of the reserved channel time setting of the CTS is the same as the cutoff point set by the RTS reserved channel information.
  • the AP After receiving the CTS frame, the AP sends a buffer unit. If the cache unit needs to respond immediately, the STA will respond.
  • the station If the station does not detect any signal within a period of time after transmitting the PS-Poll frame, or receives an error frame, it re-competes the channel.
  • the RTS frame is sent for channel reservation. If a correct CTS is received after SIFS, after a SIFS, a buffer unit is responded. After SIFS, if a block acknowledgement (Block Acknowledgment, BA) is successfully received, the subsequent cache unit of the station may continue to be performed. Transmission, but the entire transmission time (including PS-Poll) cannot exceed the TXOP upper limit of the PS-Poll corresponding collision avoidance (AC). As shown in Figure 5, if the PS-Poll corresponds to the AC's TXOP Limit of 0, then only Can transmit a buffer unit frame exchange transmission.
  • Block Acknowledgment, BA Block Acknowledgment
  • the PS-Poll listening station is received, and the NAV is updated according to the SIFS plus ACK transmission time.
  • the listening station successfully receives the RTS frame and performs the NAV update. If the channel is not detected within a certain interval, the NAV reset is performed.
  • This embodiment is an embodiment of a transmission method for downlink data collision avoidance using the present invention.
  • Implementing downlink data transmission in this embodiment mainly includes the following steps:
  • the site notifies during the association process, or negotiates the predetermined threshold with the access point.
  • the station in the energy-saving mode periodically wakes up and listens to the service indication in the Beacon. If the AP is found to have its own cache unit, it will send a PS-Poll frame through the competition. When the AP receives the station in the PS mode, it sends the message. After PS-Poll, respond according to the situation of the site BU:
  • the AP When the AP does not have the buffer unit of the STA, the AP sends an ACK indicating that the buffer unit is not.
  • the AP replies to the buffer unit indicating that there is an ACK, or when the buffer unit is smaller than the negotiated threshold, the AP may directly reply to the buffer unit, or when the cache unit is greater than the negotiated threshold.
  • the AP first sends an RTS for channel reservation, and the reserved channel time of the RTS is set to the time required to transmit data.
  • the station transmitting the PS-Poll When the station transmitting the PS-Poll receives the RTS frame, it will respond to the CTS frame after the short frame interval (SIFS), and the time cutoff point of the reserved channel time setting of the CTS is the same as the cutoff point set by the RTS reserved channel information.
  • the AP After receiving the CTS frame, the AP sends a buffer unit. If the cache unit needs to respond immediately, the STA responds, as shown in Figure 3.
  • the station If the station does not detect any signal within a period of time after transmitting the PS-Poll frame, or receives an error frame, it re-competes the channel.
  • the RTS frame is sent for channel reservation. If a correct CTS is received after SIFS, after a SIFS, a buffer unit is responded. After the SIFS, if an ACK is successfully received, the subsequent transmission of the cache unit of the station may continue, but the entire transmission time ( Including PS-Poll) can not exceed the TXOP upper limit (Limit) of PS-Poll corresponding collision avoidance (AC), as shown in Figure 4; if PS-Poll corresponds to AC's TXOP Limit is 0, only one buffer unit frame exchange can be transmitted. transmission.
  • the PS-Poll listening station is received, and the NAV is updated according to the SIFS plus ACK transmission time.
  • the listening station successfully receives the RTS frame and performs the NAV update. If the channel is not detected within a certain interval, the NAV reset is performed.
  • the station notifies or negotiates the predetermined threshold with the access point during the association process.
  • the site in the energy-saving mode wakes up actively, sends a PS-Poll frame, and asks the AP whether there is a cache unit of the site.
  • the AP responds according to the situation of the station BU:
  • the AP When the AP does not have the buffer unit of the STA, the AP sends an ACK indicating that the buffer unit is not.
  • the AP replies to the buffer unit indicating that there is an ACK, or when the buffer unit is smaller than the negotiated threshold, the AP may directly reply to the buffer unit, or when the cache unit is greater than the negotiated threshold.
  • the AP first sends an RTS to make a channel reservation.
  • the station transmitting the PS-Poll When the station transmitting the PS-Poll receives the RTS frame, it will respond to the CTS frame after the short frame interval (SIFS), and the time cutoff point of the reserved channel time setting of the CTS is the same as the cutoff point set by the RTS reserved channel information.
  • the AP When the AP receives the SIFS after the CTS frame, it will send the buffer unit. When the response mechanism of the buffer unit is set to delay response, the AP will continue to send data after the interframe interval, as shown in Figure 6.
  • the station If the station does not detect any signal within a period of time after transmitting the PS-Poll frame, or receives an error frame, it re-competes the channel.
  • the RTS frame is sent for channel reservation. If a correct CTS is received after SIFS, after a SIFS, it responds to a buffer unit and continues to transmit to the cache unit of the station after SIFS, but the entire transmission time (including PS-Poll) cannot exceed the PS-Poll correspondence.
  • TXOP upper limit Limit
  • PS-Poll corresponds to AC's TXOP Limit is 0, then only one buffer unit frame exchange transmission can be transmitted.
  • the PS-Poll listening station is received, and the NAV is updated according to the SIFS plus ACK transmission time.
  • the listening station successfully receives the RTS frame and performs the NAV update. If the channel is not detected within a certain interval, the NAV reset is performed.
  • the AP includes a receiving module 71 and a processing module 72, where:
  • a receiving module 71 configured to receive a radio frame sent by the station for inquiring whether the AP has a cache unit of the station;
  • a processing module 72 configured to determine that the AP has a cache unit of the site and the cache If the unit is greater than the predetermined threshold, the station performs a radio frame exchange reservation channel with the station, and after the channel reservation is successful, the buffer unit is sent to the station.
  • the predetermined threshold is a value negotiated by the AP and the site during the association process or the re-association process, or a value indicated by the capability information element of the broadcast frame initiated by the AP, or the AP and the AP The value indicated in the capability negotiation of the site, or the default value of the system where the AP is located.
  • the processing module 72 is configured to: after transmitting a request to send (RTS) frame to the station, perform channel reservation; and, after receiving the permission to send (CTS) frame returned by the station, to the site Transmitting the buffer unit; wherein, the reserved channel time included in the RTS frame is set to a transmission time of one or more buffer units to be sent, a time of a required response, and a radio frame in which the buffer unit is located Responding to the sum of frame intervals between radio frames in which the response includes an immediate response and/or a delayed response, a time cutoff point of the reserved channel time included in the CTS frame and a reserved channel time included in the RTS frame The time cut-off point is the same.
  • RTS request to send
  • CTS permission to send
  • the AP reserves a channel with the station when determining that the buffered data is greater than a predetermined threshold, so that the channel becomes a dedicated channel between the AP and the station, so that collisions can be avoided.
  • the AP can send a channel reservation frame, such as an RTS frame. You can reserve a longer period of time, that is, you can send multiple cache units to the STA at one time, saving link overhead.
  • the station includes a sending module 81 and a processing module 82, where:
  • a sending module 81 configured to send, to the access point (AP), a radio frame for inquiring whether the AP is a cache unit of the station;
  • the processing module 82 is configured to complete the radio frame exchange reservation channel with the AP, and receive the cache unit sent by the AP by using a channel that is successfully reserved.
  • the sending module 81 is configured to: actively send the radio frame to the AP; or, after periodically listening to the service indication information sent by the AP, send the radio frame to the AP.
  • the total transmission duration of the frame exchange sequence from the radio frame is limited by the attributes of the station in the obtained transmission opportunity; wherein the attribute of the station includes an access category corresponding to the radio frame
  • the total transmission duration is the total time of the radio frame transmitted by the station, The total time of the radio frame transmitted by the access point and the sum of the frame spacing between the radio frame transmitted by the station and the radio frame transmitted by the access point.
  • the channel reservation is completed by cooperation with the AP, so that the site side can avoid collision occurrence.
  • the foregoing method for transmitting downlink data collision avoidance can ensure fairness between each station and reasonable utilization of channel resources, thereby avoiding collision occurrence; further, after PS-Poll, the AP sends a channel reservation frame, such as an RTS frame, to reserve a segment. For a longer period of time, multiple buffer units can be sent to the STA at a time without sending a PS-Poll to each cache, thereby saving link overhead.
  • a channel reservation frame such as an RTS frame

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Abstract

本发明提供了一种下行数据碰撞避免的方法、接入点和站点，其中，下行数据碰撞避免的方法包括：接入点（AP）接收站点发送的用于询问所述AP是否有所述站点的缓存单元的无线帧；所述AP确定有所述站点的缓存单元且所述缓存单元大于预定门限后，与所述站点进行无线帧交换预约信道，信道预约成功后向所述站点发送所述缓存单元。上述下行数据碰撞避免的发送方法，能够保证各个站点之间的公平性和信道资源的合理利用，从而避免碰撞发生；此外，AP发送的信道预约帧可以预约一段较长的时间，即一次可以向STA发送多个缓存单元，从而节省了链路开销。

Description

下行数据碰撞避免的方法、 接入点和站点
技术领域
本发明涉及无线通信领域， 尤其涉及一种下行数据碰撞避免的方法、 接 人点和占点。 背景技术
目前， 在无线网络领域， 无线局域网 （WLAN )发展快速， WLAN的应 用范围日益扩大， 为应对各种网络需求， 电气和电子工程师协会工业规范 ( IEEE )802.11组颁布了 802.11a, 802.11b, 802. l lg, 802.11η等一系列 WLAN 技术标准， 随后又陆续成立了其它任务组， 致力于发展设计现有 802.11技术 改进的规范， 例如， 随着物联网的发展， IEEE成立了 802.1 lah任务组， 其主 要任务就是对 WLAN 的媒介接入控制 （MAC )层和物理（PHY )层进行修 改和增强， 以适应智能电网 （Smart Grid ) 、 传感器网络（ Sensor Network ) 、 环境 /农业检测 ( Environmental/Agricultural Monitoring ) 、 工业过程自动 4匕 ( Industrial Process Automation )等网络的需求。
无线局域网中， 一个接入点（ Access Point,简称 AP )以及与 AP相关联的 多个非接入点站点（ Non-AP Station,简称 STA )组成了一个基本服务集（ Basic Service Set, 简称 BSS ) 。 STA在使用 BSS的服务之前， 必须与 AP完成鉴权 和关联过程， 若成功关联， 则 AP 为 STA分配关联标识信息 （Association Identifier, 简称 AID ) , AID为 STA在本 BSS的身份标识， 即可以与本 BSS 内其它 STA通过 AID区分，但是属于不同 BSS的 STA可能使用同一个 AID。 同时， 多个 BSS通过分配系统（ Distribution System, 简称 DS )相连后， 可以 组成扩展服务集（ Extend Service Set, ESS ) 。 多个 STAs也可以组成一个自 组织无线局域网， 称之为独立 BSS ( Independent BSS, IBSS ) , IBSS中 STA 可以直接通信。
802.11中， 一个接入点（ Access Point, 简称 AP ) 以及与 AP相关联的多 个站点 （Station, 简称 STA )组成了一个基本服务集（Basic Service Set, 简 称 BSS ) 。 802.11 定义了两种操作模式： 分布式协调功能 （Distributed Coordination Function,简称 DCF )和点协调功能 ( Point Coordination Function , 简称 PCF ) , 以及针对这两种操作模式的改进： 增强型分布式信道访问功能 ( Enhanced Distributed Channel Access, 简称 EDCA )和混合协调功能控制信 道访问功能 ( Hybrid Coordination Function Controlled Channel Access , 简称 HCCA ) 。 其中， DCF是最基本的操作模式， 利用带有冲突避免的载波侦听 多路访问机制 （ CSMA with Collision Avoidance, CSMA/CA )使多个站点共享 无线信道。 EDCA是增强型操作模式， 将上层数据映射到四个不同的队列类 别 (AC, Access Categories): AC— VO、 AC— VI、 AC— BE、 AC— BK, 每个队列 类别使用不同的竟争信道的参数来区分优先级。 EDCA利用 CSMA/CA机制， 使多个不同优先级队列共享无线信道， 并预约一个传输机会 ( Transmission Opportunity, 简称 TXOP )。 不同优先级队列获得传输机会的基本过程为： 每 个队列在信道空闲时， 使用不同的退避间隔加上任意的竟争退避窗来接入信 道， 以减少碰撞。
多个无线站点共享信道时， 无线环境的冲突检测变得非常困难， 其中一 大问题就是隐藏站点。 如图 1所示， 站点 Α向 Β发送数据， 同时站点 C也向 站点 B发送数据， 由于站点 C和站点 A彼此都处于对方的覆盖范围之外， 站 点 A和站点 C同时发送将导致冲突。从站点 A的角度来看站点 C即是一个隐 藏站点。 为解决隐藏站点问题， 802.11提出了虚拟信道检测机制， 即通过在 无线帧帧头中包含预约信道时间信息的方式来避免隐藏站点的碰撞。 其它接 收到含有时间预约信息的无线帧的旁听站点设置本地存储的一个网络分配矢 量（Network Allocation Vector, NAV ) , NAV的取值设置为上述信道预约时 间信息和已保留的时间信息的最大值， 在该时间内， 旁听站点不会发送数据， 从而避免隐藏站点竟争信道， 造成碰撞的问题。 NAV减为零后， 其它站点才 能发送数据。 在大数据发送之前， 发送方可以先发送请求发送（Request to send, RTS )进行信道预约， 其包含信道预约时间信息。 接收方响应准许发送 ( Clear to send, CTS )进行信道预约确认， 其也包含信道预约时间信息， 以 保护发送方后续发送的无线帧， 具体过程可参见图 2。
IEEE802.i l定义了能量管理的两种模式： 活跃模式（ Active Mode, AM ) 和节电模式（Power Saving, PS ) 。 对于处于节电模式的站点， AP通过在周 期发送的信标帧 （Beacon ) 中携带业务指示信息， 即业务指示图 （Traffic Indication Map, 简称 TIM )信息元素通知这些处于节电模式的站点是否有緩 存单元（Bufferable Unit )待发。 如果这些站点发现有緩存单元， 就会通过发 送一个节电查询帧（PS-Poll ) , AP可以回复一个确认（ACK )帧也可直接回 复数据帧。 对于长时间睡眠的站点醒来， 主动发送 PS-Poll帧， AP通过发送 携带是否有下行业务指示的 ACK或者直接发送数据帧来响应。
对于大覆盖、 站点多的应用场景， 相互侦听不到的站点就会增多， 隐藏 站点的问题就会更加明显。 如果在站点发送 PS-Poll帧后， 接入点回复的帧较 长， 该帧传输的时间就会比较长， 在该站点侧， 不能接收到接入点响应的站 点就会判断信道为空闲， 竟争信道并发送数据， 造成在发送 PS-Poll的站点侧 发生碰撞。 发明内容
本发明实施例提供了一种下行数据碰撞避免的方法、 接入点和站点， 以 解决 STA发送 PS-Poll帧后，ΑΡ回复较长帧时，在该 STA侧发生碰撞的问题。
本发明实施例提供了一种下行数据碰撞避免的方法， 包括：
接入点 （ΑΡ )接收站点发送的用于询问所述 ΑΡ是否有所述站点的緩存 单元的无线帧； 以及
所述 ΑΡ确定有所述站点的緩存单元且所述緩存单元大于预定门限后， 与所述站点进行无线帧交换预约信道， 信道预约成功后向所述站点发送所述 緩存单元。
所述预定门限为所述 ΑΡ和所述站点在关联过程中或重关联过程中协商 的值， 或者， 所述 ΑΡ发起的广播帧的能力信息元素指示的值， 或者， 所述 ΑΡ和所述站点进行能力协商中指示的值，或者，所述 ΑΡ所在系统默认的值。
所述 ΑΡ与所述站点进行无线帧交换预约信道， 信道预约成功后向所述 站点发送所述緩存单元的步骤包括：
所述 ΑΡ向所述站点发送请求发送（RTS ) 帧进行信道预约； 以及 述緩存单元；
其中， 所述 RTS帧中包含的预约信道时间设置为即将发送的一个或多个 緩存单元的传输时间、 需要的响应的时间以及所述緩存单元所在的无线帧和 所述响应所在的无线帧之间的帧间隔之和， 所述响应包括立即响应和 /或延迟 响应，所述 CTS帧中包含的预约信道时间的时间截止点和所述 RTS帧中包含 的预约信道时间的时间截止点相同。
本发明实施例还提供了一种下行数据碰撞避免的方法， 包括：
处于节电模式的站点向接入点 （AP )发送用于询问所述 AP是否有所述 站点的緩存单元的无线帧； 以及
所述站点配合所述 AP完成无线帧交换预约信道， 并通过预约成功的信 道接收所述 AP发送的所述緩存单元。
所述站点向 AP发送无线帧的步骤包括：
所述站点主动向所述 AP发送所述无线帧； 或者
所述站点在周期侦听所述 AP发送的业务指示信息后，向所述 AP发送所 述无线帧。
所述站点在获得的传输机会内， 从所述无线帧开始进行的帧交换序列的 总传输时长受所述站点的属性限制。
所述站点的属性包括所述无线帧对应的接入类别参数。
所述总传输时长为所述站点传输的无线帧的总时间、 所述接入点传输的 无线帧的总时间以及所述站点传输的无线帧和所述接入点传输的无线帧之间 的帧间隔之和。
本发明实施例又提供了一种接入点 （AP ) , 包括：
接收模块， 其设置成接收站点发送的用于询问所述 AP是否有所述站点 的緩存单元的无线帧； 以及
处理模块， 其设置成确定所述 AP有所述站点的緩存单元且所述緩存单 元大于预定门限后， 与所述站点进行无线帧交换预约信道， 信道预约成功后 向所述站点发送所述緩存单元。
所述预定门限为所述 AP和所述站点在关联过程中或重关联过程中协商 的值， 或者， 所述 AP发起的广播帧的能力信息元素指示的值， 或者， 所述 AP和所述站点进行能力协商中指示的值，或者，所述 AP所在系统默认的值。
所述处理模块是设置成： 向所述站点发送请求发送（RTS ) 帧后进行信 道预约； 以及， 在接收到所述站点返回的准许发送（CTS ) 帧后向所述站点 发送所述緩存单元； 其中， 所述 RTS帧中包含的预约信道时间设置为即将发 送的一个或多个緩存单元的传输时间、 需要的响应的时间以及所述緩存单元 所在的无线帧和所述响应所在的无线帧之间的帧间隔之和， 所述响应包括立 即响应和 /或延迟响应，所述 CTS帧中包含的预约信道时间的时间截止点和所 述 RTS帧中包含的预约信道时间的时间截止点相同。
本发明实施例另提供了一种站点， 包括：
发送模块， 其设置成向接入点 （ AP )发送用于询问所述 AP是否有所述 站点的緩存单元的无线帧； 以及
处理模块， 其设置成配合所述 AP完成无线帧交换预约信道， 并通过预 约成功的信道接收所述 AP发送的所述緩存单元。
所述发送模块是设置成： 主动向所述 AP发送所述无线帧； 或者， 在周 期侦听所述 AP发送的业务指示信息后， 向所述 AP发送所述无线帧。
所述站点在获得的传输机会内， 从所述无线帧开始进行的帧交换序列的 总传输时长受所述站点的属性限制。
所述站点的属性包括所述无线帧对应的接入类别参数。
所述总传输时长为所述站点传输的无线帧的总时间、 所述接入点传输的 无线帧的总时间以及所述站点传输的无线帧与所述接入点传输的无线帧之间 的帧间隔之和。
上述下行数据碰撞避免的发送方法， 能够保证各个站点之间的公平性和 信道资源的合理利用， 从而避免碰撞发生； 此外， PS-Poll后， AP发送信道 预约帧， 比如 RTS帧， 可以预约一段较长的时间， 即一次可以向 STA发送多 个緩存单元， 而不用对每个緩存都发送 PS-Poll, 从而节省了链路开销。 附图概述
图 1为现有隐藏站点的示意图；
图 2为现有技术解决隐藏站点问题的示意图；
图 3为本发明下行数据碰撞避免的方法实施例一的示意图；
图 4为本发明帧传输总时长的示意图一；
图 5为本发明帧传输总时长的示意图二；
图 6为本发明下行数据碰撞避免的方法实施例二的示意图；
图 7为本发明 AP实施例的结构示意图；
图 8为本发明 STA实施例的结构示意图。
本发明的较佳实施方式
为使本发明的目的、 技术方案和优点更加清楚明白， 下文中将结合附图 对本发明的实施例进行详细说明。 需要说明的是， 在不冲突的情况下， 本申 请中的实施例及实施例中的特征可以相互任意组合。
本发明实施例提供了一种下行数据碰撞避免的方法， 该方法从站点的角 度进行描述， 该方法包括：
步骤 11、 处于节电模式的站点向接入点 （AP )发送用于询问所述 AP是 否有所述站点的緩存单元的无线帧；
该步骤可以包括： 所述站点主动向所述 AP发送所述无线帧； 或者， 所 述站点在周期侦听所述 AP发送的业务指示信息后，向所述 AP发送所述无线 帧。
步骤 12、 所述站点配合所述 AP完成无线帧交换预约信道， 并通过预约 成功的信道接收所述 AP发送的所述緩存单元。
所述站点在获得的传输机会内， 从所述无线帧开始进行的帧交换序列的 总传输时长受所述站点的属性限制； 其中， 所述站点的属性包括所述无线帧 对应的接入类别参数； 所述总传输时长为所述站点传输的无线帧的总时间、 所述接入点传输的无线帧的总时间以及所述站点传输的无线帧和所述接入点 传输的无线帧之间的帧间隔之和。
上述下行数据碰撞避免的方法， 基站与 AP配合完成信道预约， 使站点 侧避免碰撞发生成为可能。
本发明实施例还提供了一种下行数据碰撞避免的方法， 该方法从 AP 的 角度进行描述， 该方法包括：
步骤 21、 接入点 （AP )接收站点发送的用于询问所述 AP是否有所述站 点的緩存单元的无线帧；
步骤 22、 所述 AP确定有所述站点的緩存单元且所述緩存单元大于预定 门限后， 与所述站点进行无线帧交换预约信道， 信道预约成功后向所述站点 发送所述緩存单元。
其中， 所述预定门限为所述 AP和所述站点在关联过程中或重关联过程 中协商的值， 或者， 所述 AP发起的广播帧的能力信息元素指示的值， 或者， 所述 AP和所述站点进行能力协商中指示的值， 或者， 所述 AP所在系统默认 的值。
该步骤可以包括： 所述 AP向所述站点发送请求发送（ RTS )帧进行信道 预约； 所述 AP接收到所述站点返回的准许发送（CTS )帧后向所述站点发送 所述緩存单元； 其中， 所述 RTS帧中包含的预约信道时间设置为即将发送的 一个或多个緩存单元的传输时间、 需要的响应的时间以及所述緩存单元所在 的无线帧和所述响应所在的无线帧之间的帧间隔之和， 所述响应包括立即响 应和 /或延迟响应， 所述 CTS 帧中包含的预约信道时间的时间截止点和所述 RTS帧中包含的预约信道时间的时间截止点相同。
上述下行数据碰撞避免的方法， 在 AP确定緩存的数据大于预定门限时 与站点预约信道， 使得该信道成为 AP和站点之间的专用信道， 从而可以避 免碰撞发生； 此外， PS-Poll后， AP发送信道预约帧， 比如 RTS帧， 可以预 约一段较长的时间， 即一次可以向 STA发送多个緩存单元， 而不用对每个緩 存单元都发送 PS-Poll, 从而节省了链路开销。 实施例一
本实施例是釆用本发明的一种下行数据碰撞避免的发送方法的实施例。 在本实施例中实现下行数据传输主要包括以下步骤：
站点在关联过程中通知或者与接入点协商上述预定门限。
处于节能模式的站点， 主动醒来， 发送 PS-Poll帧， 询问 AP是否有本站 点的緩存单元； 当 AP收到处于 PS模式下的站点发送的 PS-Poll后， 根据该 站点 BU的情况 , 做出响应：
当 AP 没有该 STA 的緩存单元时， AP发送一个緩存单元指示为无的 ACK。 当 AP有该 STA的緩存单元时， AP回复緩存单元指示为有的 ACK, 或者当緩存单元小于上述协商的门限值时， AP可直接回复緩存单元， 或当緩 存单元大于上述协商的门限值时， AP先发送 RTS进行信道预约， RTS的预 约信道时间设置到发送数据需要的时间。
当发送 PS-Poll的站点收到的是 RTS帧， 会在短帧间隔 （SIFS )后， 响 应 CTS帧， CTS的预约信道时间设置的时间截止点和 RTS预约信道信息设置 的截止点一致。 AP在收到 CTS帧后的 SIFS, 会发送緩存单元， 如果该緩存 单元是需要立即响应， 该 STA就会响应， 如图 3所示。
如果站点在发送 PS-Poll帧后的一段时间间隔内， 没有检测到任何信号， 或者收到错误帧， 则重新竟争信道。
AP成功接收到 PS-Poll后， 如果发送的緩存单元超过预定的门限值， 则 发送 RTS帧进行信道预约。如果 SIFS后，接收到一个正确的 CTS,则在 SIFS 后， 响应一个緩存单元， 在 SIFS后， 成功接收到一个 ACK, 后续可以继续 对该站点的緩存单元进行传输， 但是整个传输时间 （包括 PS-Poll )不能超过 PS-Poll对应避免碰撞（ AC )的 TX0P上限（ Limit )，如图 4所示，如果 PS-Poll 对应 AC的 TXOP Limit为 0 , 则只能进行一个緩存单元需要的帧交换序列传 输。
收到 PS-Poll的旁听站点， 按照 SIFS加 ACK传输时间来更新 NAV。 旁 听站点成功收到 RTS帧并进行了 NAV更新， 如果在一段时间间隔内没有检 测到信道， 则进行 NAV重设。 实施例二
本实施例中， 上述预定门限釆用系统默认参数配置得到。
处于节能模式的站点， 主动醒来， 发送 PS-Poll帧， 询问 AP是否有本站 点的緩存单元。 当 AP收到处于 PS模式下的站点发送的 PS-Poll后， 根据该 站点 BU的情况， 做出响应：
当 AP 没有该 STA 的緩存单元时， AP发送一个緩存单元指示为无的 ACK。 当 AP有该 STA的緩存单元时， AP回复緩存单元指示为有的 ACK, 或者当緩存单元小于上述协商的门限值时， AP可直接回复緩存单元， 或当緩 存单元大于上述协商的门限值时， AP先发送 RTS进行信道预约， RTS的预 约信道时间设置到发送数据需要的时间。
当发送 PS-Poll的站点收到的是 RTS帧， 会在短帧间隔 （SIFS )后， 响 应 CTS帧， CTS的预约信道时间设置的时间截止点和 RTS预约信道信息设置 的截止点一致。 AP在收到 CTS帧后的 SIFS, 会发送緩存单元， 如果该緩存 单元是需要立即响应， 该 STA就会响应。
如果站点在发送 PS-Poll帧后的一段时间间隔内， 没有检测到任何信号， 或者收到错误帧， 则重新竟争信道。
AP成功接收到 PS-Poll后， 如果发送的緩存单元超过预定的门限值， 则 发送 RTS帧进行信道预约。如果 SIFS后，接收到一个正确的 CTS,则在 SIFS 后， 响应一个緩存单元， 在 SIFS 后， 如果成功接收到一个块确认（Block Acknowledgment, BA ) , 则后续可以继续对该站点的緩存单元进行传输， 但 是整个传输时间（包括 PS-Poll )不能超过 PS-Poll对应避免碰撞（AC )的 TXOP 上限（ Limit ) , 如图 5所示， 如果 PS-Poll对应 AC的 TXOP Limit为 0, 则只 能传输一个緩存单元帧交换传输。
收到 PS-Poll的旁听站点， 按照 SIFS加 ACK传输时间来更新 NAV。 旁 听站点成功收到 RTS帧并进行了 NAV更新， 如果在一段时间间隔内没有检 测到信道， 则进行 NAV重设。
实施例三
本实施例是釆用本发明的一种下行数据碰撞避免的发送方法的实施例。 在本实施例中实现下行数据传输主要包括以下步骤：
本实施例中， 站点在关联过程中通知， 或者与接入点协商上述预定门限。 处于节能模式的站点， 周期地醒来， 侦听 Beacon中的业务指示， 如果发 现 AP有自己的緩存单元，会通过竟争发送 PS-Poll帧， 当 AP收到处于 PS模 式下的站点发送的 PS-Poll后， 根据该站点 BU的情况， 做出响应：
当 AP 没有该 STA 的緩存单元时， AP发送一个緩存单元指示为无的 ACK。 当 AP有该 STA的緩存单元时， AP回复緩存单元指示为有的 ACK, 或者当緩存单元小于上述协商的门限值时， AP可直接回复緩存单元， 或当緩 存单元大于上述协商的门限值时， AP先发送 RTS进行信道预约， RTS的预 约信道时间设置到发送数据需要的时间。
当发送 PS-Poll的站点收到的是 RTS帧， 会在短帧间隔 （SIFS )后， 响 应 CTS帧， CTS的预约信道时间设置的时间截止点和 RTS预约信道信息设置 的截止点一致。 AP在收到 CTS帧后的 SIFS, 会发送緩存单元， 如果该緩存 单元是需要立即响应， 该 STA就会响应， 如图 3所示。
如果站点在发送 PS-Poll帧后的一段时间间隔内， 没有检测到任何信号， 或者收到错误帧， 则重新竟争信道。
AP成功接收到 PS-Poll后， 如果发送的緩存单元超过预定的门限值， 则 发送 RTS帧进行信道预约。如果 SIFS后，接收到一个正确的 CTS,则在 SIFS 后， 响应一个緩存单元， 在 SIFS后， 如果成功接收到一个 ACK, 则后续可 以继续对该站点的緩存单元进行传输， 但是整个传输时间 （包括 PS-Poll )不 能超过 PS-Poll对应避免碰撞（AC ) 的 TXOP上限（Limit ) , 如图 4所示； 如果 PS-Poll对应 AC的 TXOP Limit为 0 ,则只能传输一个緩存单元帧交换传 输。
收到 PS-Poll的旁听站点， 按照 SIFS加 ACK传输时间来更新 NAV。 旁 听站点成功收到 RTS帧并进行了 NAV更新， 如果在一段时间间隔内没有检 测到信道， 则进行 NAV重设。
实施例四
本实施例中， 站点在关联过程中通知或者与接入点协商上述预定门限。 处于节能模式的站点， 主动醒来， 发送 PS-Poll帧， 询问 AP是否有本站 点的緩存单元。 当 AP收到处于 PS模式下的站点发送的 PS-Poll后， 根据该 站点 BU的情况 , 做出响应：
当 AP 没有该 STA 的緩存单元时， AP发送一个緩存单元指示为无的 ACK。 当 AP有该 STA的緩存单元时， AP回复緩存单元指示为有的 ACK, 或者当緩存单元小于上述协商的门限值时， AP可直接回复緩存单元， 或当緩 存单元大于上述协商的门限值时， AP先发送 RTS进行信道预约。
当发送 PS-Poll的站点收到的是 RTS帧， 会在短帧间隔 （SIFS )后， 响 应 CTS帧， CTS的预约信道时间设置的时间截止点和 RTS预约信道信息设置 的截止点一致。 AP在收到 CTS帧后的 SIFS时， 会发送緩存单元， 緩存单元 的响应机制设置为延迟响应时， AP就会在帧间间隔后继续发送数据， 如图 6 所示。
如果站点在发送 PS-Poll帧后的一段时间间隔内， 没有检测到任何信号， 或者收到错误帧， 则重新竟争信道。
AP成功接收到 PS-Poll后， 如果发送的緩存单元超过预定的门限值， 则 发送 RTS帧进行信道预约。如果 SIFS后，接收到一个正确的 CTS,则在 SIFS 后， 响应一个緩存单元， 在 SIFS后继续对该站点的緩存单元进行传输， 但是 整个传输时间（包括 PS-Poll )不能超过 PS-Poll对应避免碰撞（ AC )的 TXOP 上限（ Limit ) , 如果 PS-Poll对应 AC的 TXOP Limit为 0, 则只能传输一个緩 存单元帧交换传输。
收到 PS-Poll的旁听站点， 按照 SIFS加 ACK传输时间来更新 NAV。 旁 听站点成功收到 RTS帧并进行了 NAV更新， 如果在一段时间间隔内没有检 测到信道， 则进行 NAV重设。
如图 7所示， 为本发明 AP实施例的结构示意图， 该 AP包括接收模块 71和处理模块 72, 其中：
接收模块 71 , 其设置成接收站点发送的用于询问所述 AP是否有所述站 点的緩存单元的无线帧； 以及
处理模块 72, 其设置成确定所述 AP有所述站点的緩存单元且所述緩存 单元大于预定门限， 则与所述站点进行无线帧交换预约信道， 信道预约成功 后向该站点发送所述緩存单元。
其中， 所述预定门限为所述 AP和所述站点在关联过程中或重关联过程 中协商的值， 或者， 所述 AP发起的广播帧的能力信息元素指示的值， 或者， 所述 AP和所述站点进行能力协商中指示的值， 或者， 所述 AP所在系统默认 的值。
另外， 所述处理模块 72是设置成： 向所述站点发送请求发送（RTS )帧 后， 进行信道预约； 以及， 在接收到所述站点返回的准许发送（CTS )帧后， 向所述站点发送所述緩存单元； 其中， 所述 RTS帧中包含的预约信道时间设 置为即将发送的一个或多个緩存单元的传输时间、 需要的响应的时间以及所 述緩存单元所在的无线帧和所述响应所在的无线帧之间的帧间隔之和， 所述 响应包括立即响应和 /或延迟响应 ,所述 CTS帧中包含的预约信道时间的时间 截止点和所述 RTS帧中包含的预约信道时间的时间截止点相同。
上述 AP, 在确定緩存的数据大于预定门限时与站点预约信道， 使得该信 道成为 AP和站点之间的专用信道， 从而可以避免碰撞发生； 另夕卜， AP可以 发送信道预约帧，比如 RTS帧，可以预约一段较长的时间，即一次可以向 STA 发送多个緩存单元， 节省了链路开销。
如图 8所示， 为本发明 STA实施例的结构示意图， 该站点包括发送模块 81和处理模块 82, 其中：
发送模块 81 , 其设置成向接入点 （ AP )发送用于询问所述 AP是否有所 述站点的緩存单元的无线帧； 以及
处理模块 82, 其设置成配合所述 AP完成无线帧交换预约信道， 并通过 预约成功的信道接收所述 AP发送的所述緩存单元。
其中， 所述发送模块 81是设置成： 主动向所述 AP发送所述无线帧； 或 者，在周期侦听所述 AP发送的业务指示信息后，向所述 AP发送所述无线帧。
所述站点在获得的传输机会内， 从所述无线帧开始进行的帧交换序列的 总传输时长受所述站点的属性限制； 其中， 所述站点的属性包括所述无线帧 对应的接入类别参数； 所述总传输时长为所述站点传输的无线帧的总时间、 所述接入点传输的无线帧的总时间以及所述站点传输的无线帧与所述接入点 传输的无线帧之间的帧间隔之和。
上述站点， 通过与 AP配合完成信道预约， 使站点侧避免碰撞发生成为 可能。
本领域普通技术人员可以理解上述方法中的全部或部分步骤可通过程序 来指令相关硬件完成， 上述程序可以存储于计算机可读存储介质中， 如只读 存储器、 磁盘或光盘等。 可选地， 上述实施例的全部或部分步骤也可以使用 一个或多个集成电路来实现。 相应地， 上述实施例中的各模块 /单元可以釆用 硬件的形式实现， 也可以釆用软件功能模块的形式实现。 本发明不限制于任 何特定形式的硬件和软件的结合。
以上实施例仅用以说明本发明的技术方案而非限制， 仅仅参照较佳实施 例对本发明进行了详细说明。 本领域的普通技术人员应当理解， 可以对本发 明的技术方案进行修改或者等同替换， 而不脱离本发明技术方案的精神和范 围， 均应涵盖在本发明的权利要求范围当中。
工业实用性
上述下行数据碰撞避免的发送方法， 能够保证各个站点之间的公平性和 信道资源的合理利用， 从而避免碰撞发生； 此外， PS-Poll后， AP发送信道 预约帧， 比如 RTS帧， 可以预约一段较长的时间， 即一次可以向 STA发送多 个緩存单元， 而不用对每个緩存都发送 PS-Poll, 从而节省了链路开销。

Claims

权 利 要 求 书
1、 一种下行数据碰撞避免的方法， 包括：
接入点 （AP )接收站点发送的用于询问所述 AP是否有所述站点的緩存 单元的无线帧； 以及
所述 AP确定有所述站点的緩存单元且所述緩存单元大于预定门限后， 与所述站点进行无线帧交换预约信道， 信道预约成功后向所述站点发送所述 緩存单元。
2、 根据权利要求 1所述的方法， 其中：
所述预定门限为所述 AP和所述站点在关联过程中或重关联过程中协商 的值， 或者， 所述 AP发起的广播帧的能力信息元素指示的值， 或者， 所述 AP和所述站点进行能力协商中指示的值，或者，所述 AP所在系统默认的值。
3、 根据权利要求 1或 2所述的方法， 其中：
所述 AP与所述站点进行无线帧交换预约信道， 信道预约成功后向所述 站点发送所述緩存单元的步骤包括：
所述 AP向所述站点发送请求发送（RTS ) 帧进行信道预约； 以及 述緩存单元；
其中， 所述 RTS帧中包含的预约信道时间设置为即将发送的一个或多个 緩存单元的传输时间、 需要的响应的时间以及所述緩存单元所在的无线帧和 所述响应所在的无线帧之间的帧间隔之和， 所述响应包括立即响应和 /或延迟 响应，所述 CTS帧中包含的预约信道时间的时间截止点和所述 RTS帧中包含 的预约信道时间的时间截止点相同。
4、 一种下行数据碰撞避免的方法， 包括：
处于节电模式的站点向接入点 （AP )发送用于询问所述 AP是否有所述 站点的緩存单元的无线帧； 以及
所述站点配合所述 AP完成无线帧交换预约信道， 并通过预约成功的信 道接收所述 AP发送的所述緩存单元。
5、 根据权利要求 4所述的方法， 其中：
所述站点向所述 AP发送无线帧的步骤包括：
所述站点主动向所述 AP发送所述无线帧； 或者
所述站点在周期侦听所述 AP发送的业务指示信息后，向所述 AP发送所 述无线帧。
6、 根据权利要求 4或 5所述的方法， 其中：
所述站点在获得的传输机会内， 从所述无线帧开始进行的帧交换序列的 总传输时长受所述站点的属性限制。
7、 根据权利要求 6所述的方法， 其中：
所述站点的属性包括所述无线帧对应的接入类别参数。
8、 根据权利要求 6所述的方法， 其中：
所述总传输时长为所述站点传输的无线帧的总时间、 所述接入点传输的 无线帧的总时间以及所述站点传输的无线帧和所述接入点传输的无线帧之间 的帧间隔之和。
9、 一种接入点 （AP ) , 包括：
接收模块， 其设置成接收站点发送的用于询问所述 AP是否有所述站点 的緩存单元的无线帧； 以及
处理模块， 其设置成确定所述 AP有所述站点的緩存单元且所述緩存单 元大于预定门限后， 与所述站点进行无线帧交换预约信道， 信道预约成功后 向所述站点发送所述緩存单元。
10、 根据权利要求 9所述的 AP, 其中：
所述预定门限为所述 AP和所述站点在关联过程中或重关联过程中协商 的值， 或者， 所述 AP发起的广播帧的能力信息元素指示的值， 或者， 所述 AP和所述站点进行能力协商中指示的值，或者，所述 AP所在系统默认的值。
11、 根据权利要求 9或 10所述的 AP, 其中：
所述处理模块是设置成： 向所述站点发送请求发送（RTS ) 帧后进行信 道预约； 以及， 在接收到所述站点返回的准许发送（CTS ) 帧后向所述站点 发送所述緩存单元； 其中， 所述 RTS帧中包含的预约信道时间设置为即将发 送的一个或多个緩存单元的传输时间、 需要的响应的时间以及所述緩存单元 所在的无线帧和所述响应所在的无线帧之间的帧间隔之和， 所述响应包括立 即响应和 /或延迟响应，所述 CTS帧中包含的预约信道时间的时间截止点和所 述 RTS帧中包含的预约信道时间的时间截止点相同。
12、 一种站点， 包括：
发送模块， 其设置成向接入点 （ AP )发送用于询问所述 AP是否有所述 站点的緩存单元的无线帧； 以及
处理模块， 其设置成配合所述 AP完成无线帧交换预约信道， 并通过预 约成功的信道接收所述 AP发送的所述緩存单元。
13、 根据权利要求 12所述的站点， 其中：
所述发送模块是设置成： 主动向所述 AP发送所述无线帧； 或者， 在周 期侦听所述 AP发送的业务指示信息后， 向所述 AP发送所述无线帧。
14、 根据权利要求 12或 13所述的站点， 其中：
所述站点在获得的传输机会内， 从所述无线帧开始进行的帧交换序列的 总传输时长受所述站点的属性限制。
15、 根据权利要求 14所述的站点， 其中：
所述站点的属性包括所述无线帧对应的接入类别参数。
16、 根据权利要求 14所述的站点， 其中：
所述总传输时长为所述站点传输的无线帧的总时间、 所述接入点传输的 无线帧的总时间以及所述站点传输的无线帧与所述接入点传输的无线帧之间 的帧间隔之和。
PCT/CN2013/070830 2012-03-26 2013-01-22 下行数据碰撞避免的方法、接入点和站点 Ceased WO2013143355A1 (zh)

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US20150055577A1 (en) 2015-02-26
EP2816860A4 (en) 2015-03-25
CN103369691A (zh) 2013-10-23
CN103369691B (zh) 2019-01-15
US9345042B2 (en) 2016-05-17
EP2816860A1 (en) 2014-12-24

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