CN106255224B - Channel access method and device of wireless network - Google Patents
Channel access method and device of wireless network Download PDFInfo
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- CN106255224B CN106255224B CN201610594030.9A CN201610594030A CN106255224B CN 106255224 B CN106255224 B CN 106255224B CN 201610594030 A CN201610594030 A CN 201610594030A CN 106255224 B CN106255224 B CN 106255224B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W74/00—Wireless channel access, e.g. scheduled or random access
- H04W74/08—Non-scheduled or contention based access, e.g. random access, ALOHA, CSMA [Carrier Sense Multiple Access]
- H04W74/0808—Non-scheduled or contention based access, e.g. random access, ALOHA, CSMA [Carrier Sense Multiple Access] using carrier sensing, e.g. as in CSMA
- H04W74/0816—Non-scheduled or contention based access, e.g. random access, ALOHA, CSMA [Carrier Sense Multiple Access] using carrier sensing, e.g. as in CSMA carrier sensing with collision avoidance
Abstract
The invention is suitable for the technical field of communication, and provides a channel access method and a device of a wireless network, wherein the channel access method comprises the following steps: adding a field for carrying link information in a control frame sent by a sending node; the receiving node receives the control frame and restores the link information from the control frame based on a preset physical layer beacon detection mechanism; and the receiving node judges whether the receiving node can generate interference on the data transmission of the current link or not according to the link information, and if the judging result shows that the receiving node can not generate interference on the data transmission of the current link, the receiving node triggers concurrent transmission. In the invention, aiming at the problem of influencing network performance in a CSMA/CA mechanism defined by IEEE802.11 standard, a cross-layer protocol design of a physical layer and an MAC layer is carried out, and the overall transmission performance of the network is finally improved from the two aspects of avoiding conflict and improving the opportunity of concurrent transmission.
Description
Technical Field
The invention belongs to the technical field of communication, and particularly relates to a channel access method and device of a wireless network.
Background
At present, the emergence of large data-driven applications has led to a dramatic increase in wireless traffic, creating a tremendous impact on the system bandwidth of wireless networks, and thus increasing wireless network performance is needed to meet the ever-increasing user demand. In the wireless local area network, because a plurality of nodes share the same channel resource, the nodes need to judge the channel availability before sending data, so as to avoid the conflict caused by the ongoing data transmission of other nodes.
Currently, in the IEEE802.11 standard mainly adopted by the wireless local area network, a Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) mechanism is defined for implementing channel Access in the distributed wireless local area network: the node firstly monitors the channel before sending the data, if the channel is idle, the node sends the data after a back-off time, otherwise, the node tries again until the channel changes from busy to idle. The above CSMA/CA mechanism of the physical layer has certain problems: since a sending node in a wireless network cannot accurately know the channel environment around a receiving node, the channel environment around the receiving node can only be evaluated by detecting the channel environment of the sending node, but the evaluation is often inaccurate, the sending node detects signal collision and does not represent that the receiving node also has signal collision, and otherwise, the sending node does not detect signal collision and does not represent that the receiving node also does not have signal collision. In summary, the CSMA/CA mechanism has two typical problems affecting network performance: (1) the simultaneous transmission of links possibly suffering from data transmission interference cannot be prevented, so that the network performance is reduced due to collision, namely the problem of hidden terminals is solved; (2) the simultaneous transmission of links without data transmission interference is prohibited, which causes network performance degradation due to transmission opportunity loss, i.e., exposes a terminal problem.
To solve the hidden terminal problem, the 802.11 protocol proposes a virtual carrier sense protocol, i.e. Request To Send/Clear To Send (RTS/CTS) mechanism, To reserve a channel for a certain data frame transmission. Before sending data, a node sends an RTS control frame to a receiving node, wherein the RTS frame comprises a NAV (time required for the sending node to successfully send the data frame), if a channel is idle, the receiving node replies a CTS (clear to send) control frame, the CTS frame also comprises a NAV (time required for the receiving node to successfully receive the data frame), if the sending node correctly receives the CTS frame, the sending node starts to transmit the data frame to the receiving node, after receiving an ACK (acknowledgement) control frame replied by the receiving node, the current transmission is successfully finished, and after receiving the RTS/CTS frame, the sending node and other nodes around the receiving node extract the NAV time in the RTS/CTS frame, the channel is placed in a busy state within the NAV time, data sending is forbidden, and collision is avoided.
Although the RTS/CTS mechanism solves part of hidden terminal problems, the hidden terminal problem under a large interference radius still exists; meanwhile, the control frame transmission introduced by the RTS/CTS mechanism deepens the problem of exposed terminals already existing in the physical layer CSMA/CA mechanism, and summarizing, the problems existing in the prior art are roughly divided into three categories (in the figure, a → B, C → D are two links in data transmission):
exposed terminal problem 1: miss concurrency due to prohibiting nodes around the sending node from sending dataA transmission opportunity. As shown in fig. 1(a), when node a transmits data to node B, the nodes in the gray area are in the carrier sensing range d of node aCSAnd the data transmission is prohibited, and the transmission opportunity is wasted. Taking C → D data transmission as an example, although the concurrent transmissions of a → B and C → D will not interfere with each other, node C monitors that the channel is busy, and therefore, it will keep silent until the data transmission of node a is completed.
Exposed terminal problem 2: since the links that interfere with each other and that do not interfere with each other are not distinguished according to the actual situation, the concurrent transmission opportunity is missed. As shown in FIG. 1(B), when node A transmits data to node B, the nodes in the gray area are within the transmission range d of node BTXAnd the data transmission is prohibited, and the transmission opportunity is wasted. Taking C → D data transmission as an example, although concurrent transmissions of a → B and C → D do not interfere with each other, node C receives the CTS frame from B, and therefore, will remain silent for the NAV period until node a finishes transmitting data.
Hiding the terminal problem under large interference radius: signal collisions arise due to allowing nodes within the interference radius to transmit data. As shown in fig. 1(c), since the interference radius of the node is much larger than the transmission radius, when node a transmits data to node B, the node within the diagonal area is allowed to transmit data, which interferes with the link transmission of a → B, causing retransmission, resulting in degraded network performance. Taking node C as an example, the position of the node C exceeds the transmission radius d of the node BTXBut at its interference radius dIRMeanwhile, node C does not keep silent due to failure to correctly receive the CTS frame from node B, resulting in collision.
Disclosure of Invention
In view of this, embodiments of the present invention provide a method and an apparatus for accessing a channel of a wireless network, so as to solve the problem of poor network performance of the wireless network.
In a first aspect, a channel access method for a wireless network is provided, including:
adding a field for carrying link information in a control frame sent by a sending node;
the receiving node receives the control frame and restores the link information from the control frame based on a preset physical layer beacon detection mechanism;
and the receiving node judges whether the receiving node can generate interference on the data transmission of the current link or not according to the link information, and if the judging result shows that the receiving node can not generate interference on the data transmission of the current link, the receiving node triggers concurrent transmission.
In a second aspect, a channel access apparatus of a wireless network is provided, including:
an adding unit, configured to add a field for carrying link information in a control frame sent by a sending node;
a restoring unit, configured to receive the control frame by a receiving node, and restore the link information from the control frame based on a preset physical layer beacon detection mechanism;
and the judging unit is used for judging whether the receiving node can generate interference on the data transmission of the current link or not by the receiving node according to the link information, and if the judging result shows that the receiving node can not generate interference on the data transmission of the current link, the receiving node triggers concurrent transmission.
In the embodiment of the invention, aiming at the problem of influencing the network performance in a CSMA/CA mechanism defined by the IEEE802.11 standard, the cross-layer protocol design of a physical layer and an MAC layer is carried out, and the overall transmission performance of the network is finally improved from the aspects of avoiding conflict and improving the opportunity of concurrent transmission.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
Fig. 1 is a diagram of an example of a wireless network hidden terminal problem and an exposed terminal problem provided by the prior art;
fig. 2 is a flowchart of an implementation of a channel access method of a wireless network according to an embodiment of the present invention;
fig. 3 is a flowchart of an implementation of a beacon detection mechanism provided by an embodiment of the present invention;
fig. 4 is a diagram illustrating the effect of solving hidden terminal problems and exposed terminal problems of a wireless network according to an embodiment of the present invention;
FIG. 5 is a diagram of a frame structure provided by an embodiment of the present invention;
fig. 6 is a flowchart of an implementation of control frame transmission according to an embodiment of the present invention;
FIG. 7 is a flowchart of an implementation of a NAV counter update mechanism provided by an embodiment of the present invention;
fig. 8 is a schematic diagram of an implementation of a channel access method of a wireless network according to another embodiment of the present invention;
fig. 9 is a block diagram of a channel access apparatus of a wireless network according to an embodiment of the present invention.
Detailed Description
In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular system structures, techniques, etc. in order to provide a thorough understanding of the embodiments of the invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.
Fig. 2 shows an implementation flow of a channel access method of a wireless network line provided by an embodiment of the present invention, which is detailed as follows:
s201, a field for carrying link information is added to the control frame transmitted by the transmitting node.
S202, the receiving node receives the control frame and restores the link information from the control frame based on a preset physical layer beacon detection mechanism.
S203, the receiving node determines whether the receiving node will interfere with the data transmission of the current link according to the link information, and if the determination result is that the receiving node will not interfere with the data transmission of the current link, the receiving node triggers a concurrent transmission.
In the four-step handshake protocol in the 802.11 standard, all frames can be correctly detected only in a high Signal-to-Noise Ratio environment, and information cannot be extracted in the presence of Interference or insufficient Signal energy, that is, a Signal in a wireless network can be correctly detected only when its Signal-to-Interference plus Noise Ratio (SINR) exceeds a certain threshold. Taking node C in fig. 1(a) as an example, it would remain silent to avoid interference of its data transmission to the reception of the CTS/ACK frame by node a, and taking node C in fig. 1(C) as an example, it would not be able to correctly detect the CTS frame from B and would therefore not remain silent, thus causing interference to the reception of data by node B. In order to solve the above problem, it is usually necessary to expand the transmission range of the control frame, however, it is not preferable to introduce extra interference caused by the control frame in the process of expanding the transmission range of the control frame. Therefore, the embodiment of the invention provides a new physical layer beacon detection mechanism, so that the CTS/ACK frame can be correctly detected under the condition of low SINR (far lower than a threshold value).
In a low SINR environment, when a signal is transmitted through a wireless network, a transmitting node maps a digital signal to a complex symbol through bandpass modulation, and a radio frequency receiver samples a received signal at a receiving node to obtain a corresponding discrete complex symbol, however, in an actual situation, due to the influence of an external environment and the difference of hardware, an actual symbol received by the receiving node has variations in amplitude, frequency and phase compared with an original symbol sent by the transmitting node, and therefore, the receiving node may not be able to recover a correct discrete complex symbol, thereby affecting the detection of a control frame. Therefore, in the embodiment of the present invention, first, a signal correlation technique is used to solve the problem of detecting the control frame in a low SINR environment, so that each node can detect the control frame in the low SINR environment. Fig. 3 shows an implementation flow of a signal detection method for a wireless network according to an embodiment of the present invention, which is detailed as follows:
in S301, L symbols are sequentially truncated from the first symbol of the received signal sequence to perform cross-correlation (cross-correlation) calculation with a predetermined beacon.
Here, assume that there is a beacon (i.e., a known symbol sequence) X [ i ]]1, wherein L is the number of symbols in the beacon, wherein x [ i ═ L]Representing the ith transmission symbol in the beacon, and representing the reception symbol corresponding to the ith transmission symbol as y [ i ] i at the receiving node]＝Hx[i]ej2πΔfΔt+w[i]Where H is a complex number representing a channel parameter between the transmitting node and the receiving node, ej2πΔfΔtRepresenting the phase shift of the signal, w [ i ]]Gaussian noise, which represents the ith symbol, is first received by the receiving node, starting with the first symbol (i.e., the received symbol) in the received beacon, truncating L symbols in the beacon and performing a cross-correlation operation with the first symbol.
In S302, the following operations are performed in a loop until the cross-correlation calculation for all symbols in the received signal sequence is completed: and moving one code element backwards, and sequentially intercepting L code elements to perform cross-correlation calculation with the beacon.
In S303, the position of the preset beacon in the received signal sequence is determined according to the result of the cross-correlation calculation.
Specifically, let the calculation result of the cross-correlation calculation at any position Δ in the received signal sequence beWhereinIs x [ i ]]Complex conjugate function of e-j2πΔfΔtFor phase shift compensation at the receiving node, it will beThe position of time delta' is determined as the position of the beacon in the received signal sequence.
The above scheme is based on the fact that the calculation result of the cross-correlation calculation reaches a peak value when the beacon X [ i ] appears at the position Δ 'in the received signal sequence, whereby it is possible to determine whether or not the beacon is present in the received signal sequence (the beacon is considered to be absent if the presence position Δ' is not detected), and the presence position.
In the design of the cross-layer protocol of the distributed network related to the embodiment of the invention, the RTS/CTS/DATA/ACK four-step handshake protocol defined by the IEEE802.11 standard is continuously used, a channel is reserved for DATA transmission between nodes at a certain time through an RTS/CTS frame, and a successfully received DATA packet is confirmed through ACK. In the scenarios shown in fig. 1(a) and fig. 1(b), when nodes are allowed to perform concurrent transmission, the policy inevitably causes interference to the control frame, and therefore, the solution is implemented in the embodiment of the present invention by using the above beacon detection mechanism based on the signal correlation technique; however, for the problem that the CTS frame cannot be correctly detected by the node located outside the transmission range in the hidden terminal problem with a large interference radius shown in fig. 1(c), the above beacon detection mechanism based on the signal correlation technique can also be used to solve, as shown in fig. 4:
when the node S1 is transferring data to the node R1, if the node S2 determines through the channel access mechanism that its transmission to the node R2 will not interfere with the S1 → R1 link (because the S2 has an interference radius d in the link S1 → R1)IROut), node S2 sends an RTS frame to initiate transmission. In the process of concurrent transmission of two links, the CTS and ACK of the control frame sent by the receiving node R1 or R2 may be interfered by information sent by the other link, and at this time, the relevant node may correctly extract the CTS/ACK frame through the above beacon detection mechanism based on the signal correlation technique, and successfully complete the whole transmission process.
In the process of S2 → R2 data transmission, although both S3 and S4 are outside the transmission radius dTX of R2, both nodes can correctly receive the CTS frame from R2 by the above beacon detection mechanism based on signal correlation technique, and extract the interference radius information and NAV information about S2 → R2.
In the data transmission process, the original information is firstly mapped to a certain symbol sequence (or called a map) with a unique beacon characteristic, and the receiving node recovers the original information according to the identified beacon characteristic. As shown in fig. 5, in the embodiment of the present invention, further, the control frame is modified appropriately, the map information after mapping is filled in the fields ta(s), type(s), ra(s), nav(s), and ir(s) in the new control frame structure, and for each of the fields, the node stores a mapping list unique to the entire network for describing the mapping of the original information to the map information. The sending node and the receiving node transmit the map information through the control frame, the mapped map information in the control frame is correctly identified under the condition of low signal-to-noise ratio, and then the original information is recovered according to the stored mapping list.
Specifically, as shown in fig. 5(a), a ta(s) field is added to the physical layer of the RTS frame, wherein the ta(s) field carries map information representing the node address of the sending node, and a node address-to-map information mapping table is prestored locally at the receiving node, and this information is transmitted to the receiving node along with the RTS frame. After acquiring the map information of the TA (S) field, the receiving node of the RTS frame uses the map information in the RA (S) field of the CTS/ACK frame corresponding to the RTS frame, after receiving the CTS/ACK frame of the receiving node, the sending node compares whether the RA (S) value is consistent with the TA (S) value in the RTS frame sent by the sending node, and if so, the receiving node is represented as the destination node of the frame, thereby completing the determination of the node identity. As shown in fig. 5(b), four fields of type(s), nav(s), ra(s) and ir(s) are added to the CTS frame and the ACK frame; type(s) for identifying the frame type (CTS or ACK), nav(s) describing the time required for the transmission of the data frame, ra(s) for the destination address; ir(s) describes the current link interference radius, and as with fig. 5(a), the original information will be mapped into corresponding map information and placed in the corresponding field, and the original information is recovered from the received control frame by the receiving node according to the pre-stored mapping table.
On the basis of the above embodiment, in order to further avoid interference to data frame transmission while fully mining transmission opportunities, the embodiment of the present invention adds a new field in the CTS frame for carrying the node interference radius dIRRelated information received by surrounding nodesExtracting d carried in CTS frameIRAnd if the information judges that the data transmission does not interfere with the data reception of the current link, starting the data transmission, and otherwise, keeping silence until the transmission of the current link is finished. The specific implementation mode is as follows:
in the embodiment of the invention, the carrier monitoring is no longer a judgment basis before the node sends the data, and the node also has an opportunity to send the data under the condition of monitoring that the physical channel is busy. As shown in fig. 6, when a node has a data packet to send, it will first determine whether the NAV counter is 0, and if it is 0, it means that the sent information does not affect the data transmission of other nodes; and then concurrent confirmation is carried out, if the confirmation can be transmitted, an S-RTS frame is sent after the back-off time, otherwise, the transmission is delayed, and the random time is waited for, and then the transmission is tried again. In this mechanism, the NAV counter is updated according to the received S-CTS frame and a new NAV counter update mechanism, which is shown in fig. 7:
in order to ensure that the transmission of data frames can not generate mutual interference, a NAV counter judges according to the distance between nodes in an actual scene and the interference radius of a current link, when a certain node receives an S-CTS frame, an interference radius d is replied from an IR (S) domain in the S-CTS frameIRAnd then calculating the distance d between the node and the S-CTS sending node, wherein the calculation mode is as follows: the node can evaluate and know the received power P of the S-CTSrCTSAccording to the Two Ray group model of wireless signal transmission, there areWhere c and alpha are both constants, at CTS transmit power PtCTSIn the case of a fixed, it can be calculatedAccording to d obtainedIRAnd d, the node judges whether to update the NAV counter: nodes within the interference radius need to update the NAV counter, otherwise no update is needed.
In order to increase the transmission opportunity of the node and improve the network transmission performance, in the embodiment of the present invention, the designed cross-layer protocol allows mutual interference between transmission of the control frame and the data frame, so that the node correctly extracts the required information under the condition of receiving the interference signal through a new signal detection scheme, and the processing mechanism is as shown in fig. 8. The node detects energy when monitoring a channel, if the energy increase is larger than a certain set threshold value, the node indicates that information needs to be received, and starts to perform preamble synchronous detection. The successful preamble synchronization represents that a certain frame starts to be received, and is also used for judging whether the received signal is formed by overlapping a plurality of signals in the scheme. If the received signal is a frame which is not interfered, the preamble can be directly demodulated to obtain the original information after being synchronized; if the received signal is an interfered control frame, the node may intercept the symbol at the corresponding position to perform the map identification of the feature beacon after completing the preamble synchronization, and then recover the information carried by the original control frame S-CTS (or S-ACK) according to the map information.
In the embodiment of the present invention, aiming at the three major scenarios (as shown in fig. 1) that affect the network performance in the CSMA/CA mechanism defined by the IEEE802.11 standard, the embodiment of the present invention performs a cross-layer protocol design of a physical layer and a MAC layer, and finally improves the overall transmission performance of the network from two aspects of avoiding collision and improving the opportunity of concurrent transmission.
It should be understood that, the sequence numbers of the steps in the foregoing embodiments do not imply an execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.
Corresponding to the channel access method of the wireless network described in the above embodiment, fig. 9 shows a structural block diagram of a channel access device of the wireless network provided in the embodiment of the present invention, and for convenience of description, only the relevant parts to this embodiment are shown.
Referring to fig. 9, the apparatus includes:
an adding unit 91 that adds a field for carrying link information to a control frame transmitted by a transmitting node;
a restoring unit 92, configured to receive the control frame by a receiving node, and restore the link information from the control frame based on a preset physical layer beacon detection mechanism;
and a determining unit 93, where the receiving node determines, according to the link information, whether the receiving node will interfere with data transmission of the current link, and if the determination result is that the receiving node will not interfere with data transmission of the current link, the receiving node triggers concurrent transmission.
Optionally, the additional unit 91 is specifically configured to:
adding a field for carrying map information representing a node address of the sending node in the control frame;
the reduction unit 92 is specifically configured to:
and restoring the node address from the field of the received control frame according to a mapping table from a prestored node address to map information, wherein the mapping table is used for determining the identity of the node.
Optionally, the additional unit 91 is further configured to:
adding a domain for carrying the interference radius of the sending node in a CTS control frame;
the reduction unit 92 is further configured to:
acquiring the interference radius from the domain when a CTS frame is received;
according toCalculating the distance, P, between the receiving node and the transmitting nodetCTSC and alpha are constants for the sending power of the CTS frame;
and if the distance is smaller than the interference radius, updating the NAV count of the receiving node.
Optionally, the additional unit 91 is further configured to:
adding a field of map information for describing a domain of time required for data frame transmission in the CTS control frame;
the reduction unit 92 is further configured to:
and restoring the domain from the field of the received CTS control frame according to a mapping table of prestored domain-to-map information.
Optionally, the reduction unit 92 comprises:
the intercepting subunit is used for sequentially intercepting L code elements from the first code element of the received signal sequence and carrying out cross-correlation calculation with a preset beacon;
a loop execution subunit, configured to loop the following operations until the cross-correlation calculation for all symbols in the received signal sequence is completed: moving a code element backwards, and intercepting L code elements in sequence to perform cross-correlation calculation with the preset beacon;
a determining subunit for making the calculation result of the cross-correlation calculation at any position delta in the received signal sequence asThen will beDetermining a position Δ' of the time as a position of the beacon in the received signal sequence;
wherein L is the number of code elements in the preset beacon, x [ i ]]Represents the ith transmission code element in the preset beacon, and the corresponding receiving code element of the ith transmission code element is y [ i [ i ]]＝Hx[i]ej2πΔfΔt+w[i]H is a complex number representing a channel parameter between the transmitting node and the receiving node, ej2πΔfΔtRepresenting the phase shift of the signal, w [ i ]]Representing the gaussian noise of the ith symbol,is x [ i ]]Complex conjugate function of e-j2πΔfΔtFor phase shift compensation at the receiving node.
It will be apparent to those skilled in the art that, for convenience and brevity of description, only the above-mentioned division of the functional units and modules is illustrated, and in practical applications, the above-mentioned function distribution may be performed by different functional units and modules according to needs, that is, the internal structure of the apparatus is divided into different functional units or modules to perform all or part of the above-mentioned functions. Each functional unit and module in the embodiments may be integrated in one processing unit, or each unit may exist alone physically, or two or more units are integrated in one unit, and the integrated unit may be implemented in a form of hardware, or in a form of software functional unit. In addition, specific names of the functional units and modules are only for convenience of distinguishing from each other, and are not used for limiting the protection scope of the present application. The specific working processes of the units and modules in the system may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
In the embodiments provided in the present invention, it should be understood that the disclosed apparatus and method may be implemented in other ways. For example, the above-described system embodiments are merely illustrative, and for example, the division of the modules or units is only one logical division, and there may be other divisions when actually implemented, for example, a plurality of units or components may be combined or may be integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the embodiments of the present invention may be implemented in the form of a software product, which is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, a network device, or the like) or a processor (processor) to execute all or part of the steps of the methods described in the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present invention, and are intended to be included within the scope of the present invention.
Claims (8)
1. A method for accessing a channel of a wireless network, comprising:
adding a field for carrying link information in a control frame sent by a sending node;
the receiving node receives the control frame and restores the link information from the control frame based on a preset physical layer beacon detection mechanism;
the receiving node judges whether the receiving node can generate interference on the current link data transmission according to the link information, and if the judging result shows that the receiving node can not generate interference on the current link data transmission, the receiving node triggers concurrent transmission;
wherein the preset physical layer beacon detection mechanism comprises:
sequentially intercepting L code elements from a first code element of a received signal sequence to perform cross-correlation calculation with a preset beacon;
circularly performing the following operations until the cross-correlation calculation of all the symbols in the received signal sequence is completed: moving a code element backwards, and intercepting L code elements in sequence to perform cross-correlation calculation with the preset beacon;
let the calculation result of the cross-correlation calculation at any position delta in the received signal sequence beThen will beDetermining a position Δ' of the time as a position of the beacon in the received signal sequence;
wherein L is the number of code elements in the preset beacon, x [ i ]]Represents the ith transmission code element in the preset beacon, and the corresponding receiving code element of the ith transmission code element is y [ i [ i ]]＝Hx[i]ej2πΔfΔt+w[i]H is a complex number representing a channel parameter between the transmitting node and the receiving node, ej2πΔfΔtRepresenting the phase shift of the signal, w [ i ]]Representing the gaussian noise of the ith symbol,is x [ i ]]Is compoundedYoke function, e-j2πΔfΔtFor phase shift compensation at the receiving node.
2. The method of claim 1, wherein the appending of the field for carrying link information in the control frame transmitted by the transmitting node comprises:
adding a field for carrying map information representing a node address of the sending node in the control frame;
the restoring the link information from the control frame based on a preset physical layer beacon detection mechanism includes:
and restoring the node address from the field of the received control frame according to a mapping table from a prestored node address to map information, wherein the mapping table is used for determining the identity of the node.
3. The method as claimed in claim 2, wherein said appending a field for carrying link information in a control frame transmitted by a transmitting node further comprises:
adding a domain for carrying the interference radius of the sending node in a CTS control frame;
the restoring the link information from the control frame based on the preset physical layer beacon detection mechanism further includes:
acquiring the interference radius from the domain when a CTS frame is received;
according toCalculating the distance, P, between the receiving node and the transmitting nodetCTSC and alpha are constants for the sending power of the CTS frame;
and if the distance is smaller than the interference radius, updating the NAV count of the receiving node.
4. The method of claim 2, wherein appending a field for carrying link information in the transmitted control frame further comprises:
adding a field of map information for describing a domain of time required for data frame transmission in the CTS control frame;
the restoring the link information from the control frame based on a preset physical layer beacon detection mechanism includes:
and restoring the domain from the field of the received CTS control frame according to a mapping table of prestored domain-to-map information.
5. A channel access apparatus of a wireless network, comprising:
an adding unit, configured to add a field for carrying link information in a control frame sent by a sending node;
a restoring unit, configured to receive the control frame by a receiving node, and restore the link information from the control frame based on a preset physical layer beacon detection mechanism;
a judging unit, configured to judge, by the receiving node, whether the receiving node will interfere with data transmission of a current link according to the link information, and if the judging result is that the receiving node will not interfere with data transmission of the current link, trigger concurrent transmission by the receiving node;
wherein the reduction unit comprises:
the intercepting subunit is used for sequentially intercepting L code elements from a first code element of the received signal sequence and carrying out cross-correlation calculation with a preset beacon;
a loop execution subunit, configured to loop the following operations until the cross-correlation calculation for all symbols in the received signal sequence is completed: moving a code element backwards, and intercepting L code elements in sequence to perform cross-correlation calculation with the preset beacon;
a determining subunit, configured to make a calculation result of a cross-correlation calculation at an arbitrary position Δ in the received signal sequence beThen will beDetermining a position Δ' of the time as a position of the beacon in the received signal sequence;
wherein L is the number of code elements in the preset beacon, x [ i ]]Represents the ith transmission code element in the preset beacon, and the corresponding receiving code element of the ith transmission code element is y [ i [ i ]]＝Hx[i]ej2πΔfΔt+w[i]H is a complex number representing a channel parameter between the transmitting node and the receiving node, ej2πΔfΔtRepresenting the phase shift of the signal, w [ i ]]Representing the gaussian noise of the ith symbol,is x [ i ]]Complex conjugate function of e-j2πΔfΔtFor phase shift compensation at the receiving node.
6. The apparatus of claim 5, wherein the additional unit is specifically configured to:
adding a field for carrying map information representing a node address of the sending node in the control frame;
the reduction unit is specifically configured to:
and restoring the node address from the field of the received control frame according to a mapping table from a prestored node address to map information, wherein the mapping table is used for determining the identity of the node.
7. The apparatus of claim 6, wherein the additional unit is further to:
adding a domain for carrying the interference radius of the sending node in a CTS control frame;
the reduction unit is further configured to:
acquiring the interference radius from the domain when a CTS frame is received;
according toCalculating the receiving node and the transmitting nodeDistance of points, PtCTSC and alpha are constants for the sending power of the CTS frame;
and if the distance is smaller than the interference radius, updating the NAV count of the receiving node.
8. The apparatus of claim 6, wherein the additional unit is further to:
adding a field of map information for describing a domain of time required for data frame transmission in the CTS control frame;
the reduction unit is further configured to:
and restoring the domain from the field of the received CTS control frame according to a mapping table of prestored domain-to-map information.
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