At present, in the field of wireless network, with the rapid development of the Wireless Local Area Network (referred to as WLAN for short), the requirement for the WLAN coverage is increasing and the requirement for the throughput is also higher and higher. A series of most common WLAN technical standards such as 802.11a, 802.11b and 802.11g are successively defined in the 802.11 group of the Institute for Electrical and Electronic Engineers (referred to as IEEE for short). Then other task groups appear successively, which work toward developing the standards relating to the existing 802.11 technical improvements, for example, the 802.11n task group proposes the requirement for high throughput (referred to as HT for short), introducing Multiple Input Multiple Output (referred to as MIMO for short) and beam forming technologies, and supporting a data rate of up to 600 Mbps; and the 802.11ac task group further proposes the concept of Very High throughput (referred to as VHT for short) with the data rate being able to arrive at more than 1 Gbps by introducing technologies such as greater channel bandwidth, higher order MIMO and multi-user multiple input multiple output (MU-MIMO). In addition, the main task of the newly established 802.11ah task group is to amend and enhance the Media Access Control layer (referred to as MAC for short) and the Physical Layer Protocol (referred to as PHY for short) of WLAN so as to adapt same for the requirements of networks such as Smart Grid, Environmental/Agricultural Monitoring and Industrial Process Automation.
In the WLAN, a Basic Service Set (referred to as BSS for short) is constituted of an Access Point (referred to as AP for short) and a plurality of Stations (referred to as STA for short) associated with the AR 802.11 defines two operation modes: Distributed Coordination Function (referred to as DCF for short) and Point Coordination function (referred to as PCF for short), and the improvements of these two operation modes: Enhanced Distributed Channel Access function (referred to as EDCA for short) and Hybrid Coordination Function Controlled Channel Access function (referred to as HCCA for short), wherein the DCF is the most fundamental operation mode which uses a CSMA with Collision Avoidance mechanism (referred to as CSMA/CA for short) to enable multiple stations to share a wireless channel. Whereas EDCA is an enhanced operation mode which uses the CSMA/CA mechanism to enable multiple different priority queues to share a wireless channel and reserves a transmission opportunity (referred to as TXOP for short), wherein the different priority queues are referred to as Access Category (referred to as AC for short). In a competition access mechanism, a station waits for an interframe space plus a random backoff time to detect the channel, only when the channel is idle throughout the above-mentioned waiting time, the station can access the channel; if the station starts channel access competition after accurately receiving a packet, then the interframe space of the above-mentioned waiting time is a common interframe space, wherein the common interframe space is DIFS (DCF interframe Space) under DCF and is AIFS (Arbitration Interframe Space) under EDCA; or if the station starts channel competition access after inaccurately receiving a packet, then the above-mentioned interframe space is an extended interframe space which equals a normal interframe space used after accurately receiving plus a short interframe space, and then further plus a predefined response frame transmission time, wherein the short interframe space is an interframe space used when a target recipient needs to response immediately after receiving the radio frame transmitted to itself.
When multiple wireless stations sharing the channel, it becomes very difficult to detect collisions of the wireless environment with one big problem thereof being hidden stations (as shown in FIG. 1). In an example of FIG. 1, a station A sends data to a station B, meanwhile, a station C also sends data to a station B; since C and A are both located outside the coverage range of each other, the station A and the station C sending simultaneously will result in a collision, and cause the station B to be unable to accurately receive data. Seen from a perspective of the station A, the station C is a hidden station. In order to solve the problem of hidden stations, 802.11 proposes a virtual channel detection mechanism, that is, reservation channel time information is contained in the frame header of a radio frame, other auditing stations which receive the radio frame containing the time reservation information set a locally stored Network Allocation Vector (referred to NAV for short), wherein the NAV value is set to be the maximum of the above-mentioned time reservation information, and the auditing stations will not send data within this time period so as to avoid the collisions caused by the hidden nodes competing for the channel. And other stations can send data only after the NAVs thereof decrease to zero. For example, a sender sends a Request To Send frame (referred to as RTS for short) to reserve the channel, wherein the RTS contains the channel reservation time information; and a recipient responds with a Clear To Send frame (referred to as CTS for short) to acknowledge the channel reservation, wherein the CTS also contains the channel reservation time information so as to ensure that the sender is capable of accomplishing the subsequent data frame switching. The setting of NAV is shown in FIG. 2, a general data frame switching process comprises a sender sending a data frame and a target recipient responding with a response frame after receiving successfully; and the channel time NAV reserved by the RTS/CTS may contain a time for multiple frame switching processes. In addition, the data frame and the response frame may also contain the channel reservation time information, for example, a data frame may be directly sent without using the channel time reserved by the RTS/CTS, wherein the data frame and the response frame thereof carry the channel reservation time, and the reservation time information of the data frame at least contains the transmission time of the response frame of this frame switching, and may also contain the time for subsequent frame switching.
In the WLAN, a radio frame generally contains a PHY Protocol Data Unit (referred to as PPDU for short) and a PHY Service Data Unit (referred to as PSDU for short), and in the issued Wireless Local Area Network technical standards, the PPDU only contains a training sequence and a signalling indication, e.g., an indication of modulation and coding scheme, which are necessary for decoding the PSDU. However, in the Wireless Local Area Network standards which are in the establishment, partial identification information of the recipient is added in the PPDU; when an STA detects a PPDU and the PPDU of the frame indicates that this STA cannot be the recipient of the frame, the STA may give up receiving the PEW Service Data Unit of the PPDU, where the setting value of the NAV is in the PHY Service Data Unit, then giving up receiving the PPDU, the STA will not update the NAV thereof. The main purpose of doing this is to avoid the STA decoding data packets irrelevant to itself so as to save station power; wherein the above-mentioned partial identification information of the recipient mainly refers to partial relevant identification information (Partial AID) and group identification information (Group ID). For example, in the new WLAN standards, the STA may give up receiving a certain PPDU while not update the NAV thereof in the following two cases:
(1) the PPDU is an SU PPDU, the Group ID and the Partial AID in the physical frame thereof indicate that the STA cannot be the target recipient, that is, the Partial AID indicated in the radio frame is different from the Partial AID of the STA, or the Group ID in the radio frame is 0, but the STA is neither an AP, nor a Mesh STA. and
(2) the PPDU is an MU PPDU, the STA is not in an MU group indicated by the Group ID in the frame; or the STA is in the MU group indicated by the Group ID in the frame, but the number of space time streams indicated at the position of the MU group in which the STA is located is 0.
In the prior art, although the case that an STA may give up receiving a PPDU while not update an NAV is defined, the receiving operation processing procedure of the STA which has the function of discarding a PPDU while not updating the NAV is not provided, therefore rendering the STA being unable to realise giving up the receiving of a PPDU while not updating an NAV. In addition, the prior art also fails to consider the problems that may appear after a PPDU being given up, which may cause the problems such as sending collisions. For example, in the case as shown in FIG. 1, a station B sends a radio frame to a station A, and C is an auditing station; since the station A and the station C are hidden stations to each other, the station C judges by detecting the PPDU that the PPDU sent by the station B does not contain data of itself, and the station C chooses to discard the PPDU while not update the NAV. When the station B finishes sending the PPDU, the station A will reply a response frame to the station B after a short interframe space (SIFS), whereas the station C neither updating the NAV thereof nor detecting the response frame signal sent by the station B will compete for the channel after the station B finishes sending; if the station C accesses the channel using a general competition accessing waiting time, and at this moment, the station A has not finished transmitting a response frame, then the station A and the station C are still sending simultaneously, thus the station B cannot receive accurately the response frame.