CN102413582B - Method for accessing 802.11 wireless network channel under centralized control - Google Patents
Method for accessing 802.11 wireless network channel under centralized control Download PDFInfo
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- CN102413582B CN102413582B CN201210006140.0A CN201210006140A CN102413582B CN 102413582 B CN102413582 B CN 102413582B CN 201210006140 A CN201210006140 A CN 201210006140A CN 102413582 B CN102413582 B CN 102413582B
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
Abstract
The invention relates to a method for accessing an 802.11 wireless network channel under centralized control. On the premise of retaining a competitive mechanism, the method changes a random backoff channel accessing mode into a wireless controller (AP, access point)-based centralized control mode, thus optimizing the following problems in the channel accessing process: (1) the waiting time for random backoff of a station (STA) is not necessary and different inter-frame space (IFS) durations are uniformly replaced by a short inter-frame space (SIFS) duration, thus reducing time delay of frame transmission, improving the use ratio of a channel and greatly increasing the throughput of a system; (3) when multiple stations compete for channels simultaneously, the occurrence of collision is avoided, the accessing time delay of the stations is reduced, and the packet loss rates of the stations are reduced; and (4) stations do not use channel availability assessment (CAA), thus reducing energy consumption of the stations.
Description
Technical field
The present invention is the method for the 802.11 radio network information channel accesses that a kind of center controls, and belongs to the crossing domain of computer network and radio communication.
Background technology
Along with the development of wireless communication technology, the operational environment of people is from fixedly moving towards flexibly, and WLAN (wireless local area network) all obtains in every field and uses widely.
802.11 is one of wireless local area network technologies of at present most main flow, it is formulated by IEEE (IEEE), the physical layer (PHY) of WLAN (wireless local area network) and MAC layer (MAC) is carried out to the international standard of specification.802.11 series standards currently provide two kinds of MAC access mechanisms, distributed coordination function (DCF respectively, Distributed Coordination Function) and centralized coordination function (PCF, Point Coordination Function), wherein distributed coordination function is the most widely used current MAC access mechanism.Distributed coordination function does not adopt any center to control, but allows each website use the distributed access way of carrier sense/conflict avoidance (CSMA/CA) mechanism, allows each website obtain the access right of channel by free competition.Each website is when intending access, need first by carrying out a fixing duration (DCF inter-frame space to media, intercepting DIFS) carries out a channel available assessments (CCA), if media state is idle, this website thinks that it can have media and start a Frame switch.If busy medium, this website waits for that cut-off becomes idle condition, after prolong DIFS duration, and further wait for a random back-off period.If media prolong and keep idle condition during backoff period after DIFS, then website thinks that it can have media and can start a Frame switch.
The all websites of DCF mechanism regulation all will carry out CCA before access media, and when media transfer the free time to, prolonged DIFS duration after needs, and then waited for a backoff period.In addition, if multiple website accesses and collides simultaneously, then website all needs to adopt fallback mechanism, and the interval [0 of random back duration is expanded when next time is accessed, CW] (competition window, contention window, CW), reduce with this probability that again collides.Therefore, when the increase of website quantity, the traffic increase time, DCF mechanism is difficult to solving collision and frequently occurs, the ever-increasing problem of backoff period, thus causes website access delay to increase, and channel utilization declines.
Summary of the invention
Technical goal: the object of the invention is, in order to overcome above-mentioned shortcoming of the prior art, to provide a kind of center of improvement to control the method for 802.11 channel access.This method passes through the access of wireless controller (AP) centralized management and control channel, under the prerequisite ensureing competition, eliminate the free competition of website (STA) random back formula, and replace with short frame pitch duration (SIFS) by unified for different frame pitch durations (IFS), reduce the time delay between frame transmission, improve the efficiency of channel usage, especially multi-site simultaneously competitive channel time, the generation of collision free, optimize the access of website, make website eliminate the use of channel available assessments (CCA) simultaneously, reduce the energy consumption of website.
Service condition: in the method that 802.11 radio network information channels controlled at a kind of center of the present invention access, when there is following situation, AP and website enable the method:
1) when website will carry out Frame switch constantly, or transmission is more than a transmission opportunity (TXOP), then website is after completing first Frame switch, or after a TXOP, AP and website enable the method;
2) in a basic service set (BSS), if there be the website active more than will carry out Frame switch simultaneously, then AP and website enable the method.
To achieve the above object, the present invention adopts following technical scheme: in the method for a kind of center of the present invention control type 802.11 radio network information channel access, AP will set up a site information competition permutation table, prepare to use the website of channel to send the competition information of the interior random number in given zone as oneself to AP, AP organizes website to carry out channel access by recording and arrange these competition information.
A method for center control type 802.11 radio network information channel access, comprises the following course of work:
1) AP is after beacon (Beacon) frame of periodic broadcast, the access slot that a length is DCF frame pitch (DIFS) is set, all websites newly added in the access slot of this DIFS duration, can send access request to AP;
2) AP is after having broadcasted beacon frame, carries out intercepting of lasting DIFS duration to administrative channel, judges whether the site requests access newly added;
3) newly add after website receives beacon (Beacon) frame, channel available assessments (CCA) is not carried out to media, after SIFS time slot, send access request (RTS) frame directly to AP to attempt accessing channel, this time access is the initial access newly adding website;
4), after AP listens to RTS frame, inform that corresponding website can use channel at ensuing time slot to newly adding station replies modified model permission transmission (eCTS) frame;
5) newly add website and carry out exchanges data with AP after access channel, and safeguard the communication next time with AP by the data frames exchange of subsidiary random number;
6) AP records random number in competition permutation table, then according to competition permutation table, determine the next website using channel, send eCTS frame, inform that website uses channel at ensuing time slot, and confirm the random number of (ACK) upper website, meanwhile, AP upgrades competition permutation table;
7) corresponding website and AP carry out exchanges data, and safeguard the communication next time with AP by the data frames exchange of subsidiary random number, until complete the transmission of all data, thus terminate communication, exit competition permutation table.
In the 802.11 wireless channel cut-in methods that above-mentioned center controls, in described step (1), the beacon (Beacon) of periodic broadcast is specially: the interval duration of AP periodic broadcast beacon (Beacon) is 20 ~ 1000ms, and default value is 100ms.
In the 802.11 wireless channel cut-in methods that above-mentioned center controls, modified model in described step (4) allows to send (eCTS) frame and is specially: this frame is the frame that this method newly defines, it acts between AP and STA, eCTS frame is sent to website by AP, be used for informing that the next one can use the website of channel to access, confirm whether the random number that (CRT field) upper website sends correctly is received by AP, and confirm the Frame of (ACK) upper station transmission.
In the 802.11 wireless channel cut-in methods that above-mentioned center controls, in described step (2), judge whether the site requests access newly added, successively through following steps: AP is intercepting in process, if receive after sending (RTS) frame from the request newly adding website, then send modified model to allow to send (eCTS) frame, and preferentially allow the website newly added carry out attaching the data frames exchange of random number next time; If do not receive the access request newly adding website, then continue to carry out Frame switch by competition permutation table order with website in permutation table.
In the 802.11 wireless channel cut-in methods that above-mentioned center controls, in described step (3), newly add website to send access request (RTS) frame to AP and attempt initially accessing channel, successively through once step: if website receives the eCTS frame corresponding with oneself sent from AP, then access channel success, newly adds website and AP carries out the data frames exchange that first time attaches random number; If website does not receive the eCTS frame corresponding with oneself, then access channel failure, website is from interval [0, CW] an interior selection random back number, and after prolong the corresponding beacon of this number, then ask access, website repeats step (3) until complete access.
In the 802.11 wireless channel cut-in methods that above-mentioned center controls, described interval [0, CW] specifically refer to: contention window parameter CW initial value is taken as 3, effectively double when each access is unsuccessful, until 15, (that is 3,7,15) unless and till keeping this value to be reset, CW is reset newly adding after website successfully accesses.
In the 802.11 wireless channel cut-in methods that above-mentioned center controls, in described step (5), the data frames exchange of subsidiary random number is specially: when website carries out exchanges data at every turn, one is incidentally sent afterwards in competition window interval [0 at Frame (or last Frame in a TXOP), CWmax] in random number, as obtaining channel usufructuary competition information next time.
In the 802.11 wireless channel cut-in methods that above-mentioned center controls, described interval [0, CWmax] specifically refers to: this interval is a fixed interval, and wherein the value of CWmax is 1023.The random number that the website preparing access media is chosen from competition window interval, only with the position of this website in competition permutation table of making decision.
In the 802.11 wireless channel cut-in methods that above-mentioned center controls, in described step (6), AP upgrades competition permutation table, concrete grammar is: AP is after the website selecting next use channel, random number corresponding to this website is deducted, to complete renewal by remaining random number in competition permutation table.
In the 802.11 wireless channel cut-in methods that above-mentioned center controls, after described step (7), if AP does not receive random number after website Frame switch terminates, then remove the information of website in competition permutation table.
Beneficial effect: have employed the 802.11 wireless channel cut-in methods that this center controls, access in the process of channel at STA, both ensure that competition, justice eliminates the wait time slot of STA random back, and replace with short frame pitch duration (SIFS) by unified for different frame pitch durations (IFS), reduce the time delay between frame transmission, improve the efficiency of channel usage, especially multi-site simultaneously competitive channel time, the generation of collision free, optimize the access of STA, make STA eliminate the use of channel available assessments (CCA) simultaneously, reduction website energy consumption.
Accompanying drawing explanation
Fig. 1 is the frame assumption diagram of the eCTS (modified model allows access frame) of the centralized cut-in method of center of the present invention control type 802.11 wireless channel, wherein CRT field is for confirming the random number of a upper website, RA field is the next address allowing the website of access channel, and RA (ACK) field is for confirming a upper Frame;
Fig. 2 is the schematic diagram of the website contention access power of the centralized cut-in method of center of the present invention control type 802.11 wireless channel, random back number is sent after new access STA1 first completes a data transfer, all the other STA obtain channel access power successively according to the competition permutation table order in AP, and after Frame, send random back number;
Fig. 3 is the use schematic diagram of the TXOP of the website contention access power of the centralized cut-in method of center of the present invention control type 802.11 wireless channel, STA1 completes the transmission of desired data at a TXOP, STA2 does not complete the transmission of desired data in a TXOP, then send random back number after last Frame in TXOP;
Fig. 4 is the schematic diagram of the blocks of data turnaround sequence of the centralized cut-in method of center of the present invention control type 802.11 wireless channel, STA1 carries out the data burst without the need to collision detection in first TXOP, if Bulk transport needs to cross over multiple TXOP, then STA sends random back number after last Frame;
Fig. 5 is the flow chart of the centralized cut-in method of center of the present invention control type 802.11 wireless channel.
Embodiment
In order to more clearly understand technology contents of the present invention, describe in detail especially exemplified by following examples.
Referring to shown in Fig. 1 and Fig. 4, is a kind of Frame switch sequence of method and the flow chart of execution mode of 802.11 wireless networks accesses of a kind of center control provided by the present invention.
Suppose application example: one based on 802.11 wireless network, all STA associate with AP, and all STA are in same BSS collection, and network just completes initialization, and the competition permutation table of AP is empty.Its embodiment is described below:
1) AP checks whether competition permutation table is empty;
2) send beacon to the AP cycle (100ms), then wait for the DIFS period, and intercept the RTS frame whether having and send from STA to be accessed in section at this moment;
3) certain website (STA1) prepares initiating communication, and STA1 does not carry out CCA detection to channel, but sends RTS frame directly to AP:
4) after AP receives the RTS frame sent from STA1, through the SIFS period, AP sends eCTS (STA1) frame, allows STA1 to carry out Frame switch;
5) after STA1 receives eCTS frame, learn and oneself obtain channel access power, after waiting for the SIFS period, start frame exchanges, after completing first (TXOP) data frames exchange, still have outgoing data, so in the end send random back number (e.g., 317) after a Frame;
6) AP receives Frame from STA1 and rollback number, sets up competition permutation table;
7) owing to only having STA1 in the current competition permutation table of AP, therefore AP is after the interval SIFS period, send eCTS (STA1) frame, the random back number of a upper Frame and STA1 is confirmed, and informs that STA1 allows ensuing channel access;
8) AP is while communicating with STA1, guarantees to send beacon periodically;
9) after some periods, STA2, STA3 ..., STAn (n=2,3 ..., 1024) also start respectively to carry out exchanges data;
10) website such as STA2 adopts the mode of initial access to access channel after AP broadcast beacon, and sends random back number to AP after completing first time and the exchanges data of AP, adds the competition permutation table of AP;
11) AP is according to competition permutation table, selects the channel access having the minimum STA of rollback number and carry out next time, and after sending eCTS frame, upgrade competition permutation table, until STA1, STA2 ..., STAn (n=1,2 ..., 1024) all complete data transmission, the competition permutation table of AP is empty, repeats step (1).
The method of the 802.11 wireless network accesses that a kind of center that have employed this invention controls, wireless STA no longer needs to carry out CCA detection to media before access channel, and only need by intercepting eCTS frame, determine whether to obtain channel access power, the DIFS time slot that the media free time is waited for afterwards is also reduced to SIFS.In addition, the method changes the character of random back number, and the time both eliminated physically is waited for, remains competition mechanism again, simultaneously because the foundation of competition permutation table, completely avoid collision.
In this description, the present invention is described with reference to its specific embodiment.But, still can make various amendment and conversion obviously and not deviate from the spirit and scope of the present invention.Therefore, specification and accompanying drawing are regarded in an illustrative, rather than a restrictive.
Claims (2)
1. the method that 802.11 radio network information channels that center controls access, 802.11 described wireless networks comprise wireless access point AP and some wireless site STA, and described cut-in method comprises the following steps:
1) AP periodically sends beacon frame, then waits for the distributed frame spacing duration DIFS period, and intercepts the access request RTS frame whether having and send from STA to be accessed in section at this moment;
2) new site STA1 prepares initiating communication, and STA1 does not carry out channel available assessments CCA to channel and detects, but sends RTS frame to AP after waiting for the short frame pitch duration SIFS period after beacon frame;
3) after AP receives the RTS frame sent from STA1, preferentially give the chance of a new access website data frames exchange, through the SIFS period, AP sends modified model and allows to send eCTS frame, allows STA1 to carry out data frames exchange;
4), after STA1 receives eCTS frame, learn and oneself obtain channel access power, after waiting for the SIFS period, start data frames exchange, after completing first transmission opportunity TXOP data frames exchange, if still have outgoing data, then in the end carry random back number in a Frame;
5) AP receives Frame from STA1 and random back number, is joined by STA1 in competition permutation table;
6) AP selects to have in competition permutation table the exchanges data that the minimum STA of random back number carries out next time, after the interval SIFS period, send eCTS frame, a upper Frame carrying random back number is confirmed, and inform that selected STA carries out data frames exchange, the SIFS period is waited for after being received eCTS by the STA selected, complete a TXOP data frames exchange, if still have outgoing data, in the end carry random back number in a Frame, AP upgrades competition permutation table after receiving random back number, send until all STA in competition permutation table all complete data, the competition permutation table of AP is empty, repeat step 1),
7) after some periods, STA2, STA3, ..., STAn performs step 1 respectively as new site according to the mode of STA1)-5) realize the exchange of first run Frame, after this when not having new site to add, according to step 6) and mode carry out the exchange of subsequent data frame, wherein, n represents the STA number in network.
2. the method that 802.11 radio network information channels that a kind of center according to claim 1 controls access, it is characterized in that, STA is only when accessing channel first, send RTS and carry out access channel request, STA only, after receiving the eCTS frame of informing and oneself allowing to access channel, just sends Frame, if fail to receive corresponding eCTS frame, then adopt the mode of rollback, wait for that next access slot sends RTS frame again and asks; STA, except obtaining in the period except channel access power, does not carry out channel competition.
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| CN108650715B (en) * | 2012-06-19 | 2022-04-15 | 韩国电子通信研究院 | Time slot-based channel access control device and method for wireless local area network system |
| CN102883461B (en) | 2012-09-21 | 2016-06-08 | 华为技术有限公司 | The method of channel access and node |
| CN102984807B (en) * | 2012-12-14 | 2015-12-09 | 东莞宇龙通信科技有限公司 | Data communication equipment and data communications method |
| JP6018323B2 (en) * | 2013-01-16 | 2016-11-02 | エルジー エレクトロニクス インコーポレイティド | Method and apparatus for performing backoff in wireless LAN system |
| CN104333858B (en) * | 2013-07-22 | 2018-03-16 | 中国科学院信息工程研究所 | It is a kind of based on the channel resource control method for going association/de-authentication frames |
| CN104333859B (en) * | 2013-07-22 | 2017-11-14 | 中国科学院信息工程研究所 | A kind of communication management-control method of WLAN |
| WO2015042876A1 (en) * | 2013-09-27 | 2015-04-02 | 华为技术有限公司 | Channel access method and equipment |
| CN104661320B (en) * | 2013-11-20 | 2019-03-19 | 华为技术有限公司 | Channel access control method and device |
| US9801147B2 (en) * | 2013-11-25 | 2017-10-24 | Qualcomm Incorporated | Method of synchronization within an LTE/LTE-A system in unlicensed spectrum |
| WO2015109890A1 (en) * | 2014-01-27 | 2015-07-30 | 华为技术有限公司 | Method and apparatus for channel competition |
| WO2015109603A1 (en) * | 2014-01-27 | 2015-07-30 | 华为技术有限公司 | Method and device for channel competition |
| WO2016145662A1 (en) * | 2015-03-19 | 2016-09-22 | 华为技术有限公司 | Uplink multi-user access method and apparatus |
| CN105188107B (en) * | 2015-08-11 | 2018-11-23 | 华讯方舟科技有限公司 | Improve the method and device of the access efficiency of website |
| CN107113865A (en) * | 2015-08-14 | 2017-08-29 | 华为技术有限公司 | Based on the channel evaluating method and sending node for exempting from licensed spectrum |
| CN108024315B (en) * | 2018-01-04 | 2023-12-05 | 苏州中亿丰科技有限公司 | Large-scale space WiFi multi-point access system and communication method thereof |
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