WO2008131659A1

WO2008131659A1 - Medium access control method and equipment for supporting intelligent antenna application

Info

Publication number: WO2008131659A1
Application number: PCT/CN2008/070339
Authority: WO
Inventors: Changle Li; Jiandong Li; Xuelian Cai; Jianfeng Song; Ting Chen; Qi Ding
Original assignee: Huawei Technologies Co., Ltd.; Xidian University
Priority date: 2007-04-28
Filing date: 2008-02-21
Publication date: 2008-11-06
Also published as: CN101034925B; CN101034925A

Abstract

A medium access control method and equipment for supporting intelligent antenna application. The method includes: the access point determines the user station number currently correlative with the access point and the directional beam width for scanning(101); the access point chooses the access method with the best performance under the current user station number and the directional beam width, according to the relationship between the two beforehand established parameters of the user station number and the directional beam width and the access method with the best performance(102); the access point uses the chosen access method to provide the access for the user station point(103). The access point equipment includes: the intelligent antenna unit, the determining unit, the memory unit, the processing unit, and the access unit. The method or equipment can adaptively choose the access method currently with the best performance and provide the access for the user station point, according to the current traffic load of the network.

Description

Media access control method and device supporting smart antenna application

Technical field

The present invention relates to the field of wireless local area networks and smart antennas, and in particular to a medium access control method and device for supporting smart antenna applications in a wireless local area network. Background of the invention

Wireless LAN, as a wireless data network solution, uses wireless signals to connect user sites and access points (APs). Access points and user sites in WLANs generally use omnidirectional antennas, and the coverage of access points is small at a specified transmit power.

Smart antennas can be viewed as a mechanism for making full use of space resources for signal quality improvement, interference suppression (or cancellation), and adaptive beam adjustment. A significant advantage of smart antennas is distance extension. The beam when the smart antenna works in beamforming mode allows the user station to operate farther away from the access point without having to increase the uplink transmit power of the user site or the downlink transmission of the access point. power.

In view of the shortcomings of the above-mentioned wireless local area network using omnidirectional antennas, it is hoped to expand the coverage of the wireless local area network by using smart antennas in the wireless local area network, and the application of the access point using the smart antenna and the support of the wireless local area network. The media access control method of the antenna has been studied. Research shows that the access point equipped with smart antenna has two modes of operation: omnidirectional and beamforming (ie, orientation), and its directional mode access point can communicate with user sites outside its omnidirectional broadcast range. Media access control method for supporting smart antennas in wireless local area networks, specifically, literature (Li Changle, Li Jiandong, Li Bo, Zhang Guanghui, Zhou Lei, He Peng, "A new type of multiple access to effectively support smart antennas in wireless local area networks Into the agreement,,, Journal of Xidian University, Vol. 33, No. 2, Apr. 2006, pp. 236-240, 256) discloses an AP superframe structure combining an omnidirectional transmission period and a directional transmission period, where the AP communicates with the user site in the omnidirectional transmission period and the omnidirectional broadcast period, in the directional transmission period and in the omnidirectional direction Communication of user sites outside the broadcast range provides access to all user sites located within the targeted transmission range of the AP. At the same time, the document also discloses that media access control methods supporting smart antenna applications in the following four wireless local area networks can be used to provide access to all user sites located within the directional transmission range of the AP:

(1) The AP provides access to the user station in its omnidirectional broadcast range by polling in the omni mode (the mode is called 0 mode), but is outside the omnidirectional broadcast range but oriented The user site within the transmission range adopts a method of providing access by competing interactive packets in a directional mode (called d mode, also referred to as beamforming mode). The method is called the o/d (competition) method, which shows that the AP and its user sites outside the broadcast range communicate through a competitive method.

(2) The AP provides access to the user station within the omni-directional broadcast range by polling in the omni mode, and provides the polling method in the directional mode for the user station outside the omnidirectional broadcast range. Access, that is, each time communicating with the external site of the broadcast range, the directional beam is first used to scan the entire space to find the user site, and then the data packet is sent to the user and the user's uplink data packet is received, which is called o/d (polling). method.

(3) The AP does not distinguish the location of the user, and provides access to all user sites located in its directional transmission range by means of competing interactive data packets in the directional mode, that is, the AP scans the entire space through the directional beam, and the beam range All sites compete for sending data packets, which are called d/d (competition) methods.

(4) The AP does not distinguish the location of the user, and provides access to all user sites located within its directional transmission range by polling in the directional mode, that is, all user sites located within its directional transmission range are first passed. The directional beam scans the entire space to find the user site, and then interacts with the user site for data packets, called the d/d (polling) method. The o/d (competition) access method and the o/d (polling) access method can be implemented by adopting an AP superframe structure combining an omnidirectional transmission period and a directional transmission period.

At the same time, the paper also compares the performance of users across the network using these four access methods. In the case of different traffic loads, the performance of the four access methods is different. Among them, the use of o / d (competition) method in the case of heavy traffic load can make the network have superior performance, but this method can not guarantee the performance under the light load of network traffic. In the case of light load on the network service, if the number of user sites in the network is less than 34, the d/d (polling) method performs better. However, any of the above access methods cannot guarantee that the performance of the entire network user is superior under various service load conditions. Summary of the invention

In view of the above, the first object of the present invention is to provide a medium access control method for supporting a smart antenna application, and a second object of the present invention is to provide an access point device to ensure network-wide user performance in various services. It is superior under load conditions.

In order to achieve the above object, the technical solution of the present invention is achieved as follows:

A media access control method supporting a smart antenna application, comprising:

The access point determines the number of user sites currently associated with it and the width of the directional beam it uses for scanning;

The access point selects the best performance access under the current number of user stations and the directional beamwidth according to the correspondence between the pre-established number of user sites and the directional beamwidth and the optimal access method. Method

The access point provides access to the user site using the selected access method.

An access point device, the access point device includes: a smart antenna unit, a determining unit, a storage unit, a processing unit, and an access unit, where

a smart antenna unit for transmitting a continuous directional beam scanning network with a predetermined beamwidth Network space

a determining unit, configured to determine a number of user sites currently associated with the access point device and a width of the directional beam used by the smart antenna unit for scanning;

a storage unit, configured to store a correspondence between a pre-established number of user sites and a directional beamwidth and an access method with optimal performance;

a processing unit, configured to select, according to the number of user sites and the directional beamwidth determined by the determining unit, and the corresponding relationship stored in the storage unit, to select an optimal performance under the current number of user sites and directional beamwidth Entry method

An access unit, configured to provide access to a user site by using an access method selected by the processing unit.

Thus, the present invention has the following advantages:

When the service load of the network changes, the medium access control method of the present invention can adaptively switch to the service load after the change according to the correspondence between the pre-established service load and the performance-optimized access method. The performance-optimized access method ensures that the performance of the entire network user is superior under various service load conditions. BRIEF DESCRIPTION OF THE DRAWINGS

1 is a network model diagram of a BSS of the prior art;

2 is a schematic diagram of a wireless local area network coverage range formed by an AP and a user site in a BSS in the prior art;

3 is a flowchart of Embodiment 1 of a medium access control method according to the present invention;

4 is a flow chart showing the access provided by polling in Embodiment 1 of the medium access control method of the present invention;

FIG. 5 is a flowchart of providing access by using a competitive manner in Embodiment 1 of the medium access control method of the present invention; FIG. 6 is a structural diagram of a protocol for providing access to a user site in a contending mode in a directional mode in Embodiment 1 of the medium access control method of the present invention;

FIG. 7 is a flowchart of providing access to a user site in a competitive mode in a directional mode in Embodiment 1 of the medium access control method of the present invention; FIG.

8 is a flowchart of providing access to a destination user site located in a current directional beam range by using a polling mode in a directional mode in Embodiment 1 of the medium access control method of the present invention;

9 is a flowchart of providing access to a destination station located in an omnidirectional broadcast range by using a polling mode in an omni mode in Embodiment 1 of the medium access control method of the present invention; FIG. 10 is in the present invention. In Embodiment 1 of the medium access control method, a protocol structure diagram for providing access to a destination station located in an omnidirectional broadcast range by using a polling mode in an omnidirectional mode;

11 is a superframe structure diagram for combining an omnidirectional transmission period and a directional transmission period for implementing an o/d (competition) access method in Embodiment 1 of the medium access control method of the present invention; 12 is a typical frame structure diagram of an omnidirectional transmission period for implementing an o/d (competition) access method in Embodiment 1 of the medium access control method of the present invention;

13 is a diagram showing a typical frame structure of a directional transmission period for implementing an o/d (competition) access method in Embodiment 1 of the medium access control method of the present invention;

14 is a time slot structure diagram of a competitive decomposition section for implementing an o/d (competition) access method in Embodiment 1 of the medium access control method of the present invention;

15 is a flowchart of an embodiment of a media access control method according to the present invention;

16 is a schematic diagram showing the basic structure of Embodiment 1 of an access point device according to the present invention;

FIG. 17 is a schematic diagram of a specific structure of Embodiment 2 of an access point device according to the present invention. Mode for carrying out the invention

In order to make the objects, the technical solutions and the advantages of the embodiments of the present invention more clear, the embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

The embodiment of the present invention provides a media access control method for supporting a smart antenna application, and the core idea is: the access point is based on the number of user sites associated with the current network and the width of the directional beam used to scan the network space. And the correspondence between the two parameters of the number of pre-established user sites and the width of the directional beam and the optimal access method to adaptively switch the current access method to the current number of user sites and directional beamwidth The best performance access method.

It can be seen that, in the embodiment of the present invention, the access point does not use an access mode to provide access to the user site, but the number of user sites associated with the access point in the current network and the width of the directional beam used. The adaptive access method from the adaptation to the current performance, so as to ensure that the performance of the entire network user is superior under various service load conditions. The user site uses a normal omnidirectional antenna, and the AP is configured with a single beam smart antenna.

The invention can be applied to a basic service set (BSS) of a wireless local area network. FIG. 1 shows a network model diagram of a BSS in the prior art. As shown in FIG. 1, a BSS includes: an access point (AP) and a plurality of user stations (STAs). In this embodiment, all user sites use the same frequency as the AP, and communicate in a time division duplex mode. The AP is equipped with a smart antenna, which has an omnidirectional and directional working mode, and the user site can use a common omnidirectional antenna or a smart antenna. The AP omnidirectional broadcast range is determined by the maximum transmit power level of the antenna array omni mode. Depending on the transient topology of the system, the user site resides inside or outside the AP omnidirectional broadcast range. 2 is a schematic diagram of a wireless local area network coverage formed by an AP and a user station in a BSS of the prior art. As shown in Figure 2, the directional mode of operation of the AP forms a beam whose communication distance Rs exceeds the broadcast distance Rc of its omni mode.

Example 1: In this embodiment, the user site uses a common omnidirectional antenna, and the AP is configured with a single beam smart antenna. The single beam formed by the AP can cover the entire surrounding space after B consecutive scans.

Figure 3 is a flow chart of Embodiment 1 of the method of the present invention. Referring to FIG. 3, the media access control method supporting the smart antenna in this embodiment includes the following steps:

Step 101: The access point determines the number of user stations currently associated with it and the width of the directional beam it uses for scanning.

In the actual service implementation, after the association phase of each user site (ie, the process of mapping between the user site and the access point to start the user site accessing the network), the AP can count all the registrations in the network (ie, all The number N of user sites associated with the access point. For a directional beam width, after the smart antenna is configured on the AP, the beam width is a performance parameter of the AP. In the specific implementation, the AP can obtain the information of the parameter through the communication primitive.

Step 102: The access point selects the performance according to the current number of user sites and the directional beamwidth according to the correspondence between the two parameters of the pre-established number of user sites and the directional beamwidth and the optimal access method. The optimal access method.

In an actual service implementation, the pre-established correspondence may be preset in the AP. The implementation of the correspondence may be a list stored in the AP, the list includes a predetermined number of user sites, a directional beamwidth of a predetermined value, and a number of user sites and directional beams of the predetermined value. The best performance access method for the width. The access point can obtain the best performance access method corresponding to the current number of user data stations and the directional beamwidth by looking up the table.

In a specific implementation of the embodiment, the access point selects an access method with the best performance from the following four methods for providing access to all user sites within the directional transmission range of the access point, and compares the performance by using the simulation. The performance of the four access methods, where, exemplarily, the performance metric selected for evaluation is the average delay and network normalized throughput of all site data packets. Then, based on the result of the comparison, the number of user sites required for adaptive switching is established. The correspondence between the two parameters of the directional beam width and the access method with the best performance. These four access methods have been introduced in the background art, specifically:

(i) The AP provides access to omni-directional mode polling for user sites located within its omni-directional broadcast range, and uses directional mode for user sites located outside its omnidirectional broadcast range and within its directional transmission range. The way of competing provides the access method of access, that is, the o/d (competition) method.

(ii) the AP provides access to omnidirectional mode polling for subscriber stations located within its omnidirectional broadcast range, and directional mode rounds for subscriber stations located outside its omnidirectional broadcast range and within its directional transmission range The polling mode polling mode provides an access method for access, that is, an o/d (polling) method.

( iii ) The AP does not distinguish the location of the user, and all access to the user's site within its directional transmission range is provided by the access method in the directional mode, that is, the d/d (competition) method.

( iv ) The AP does not distinguish the location of the user, and provides access mode, ie d/d (polling) method, for directional mode polling for all user sites located within its directional transmission range.

In an embodiment of the invention, the performance of the above four access methods is evaluated by simulation. In a specific implementation, the following simulation models and simulation parameters may be used:

The AP is configured with a single-beam antenna. The number of all user stations associated with the AP in the network is N, and is evenly distributed around the AP. (Each user is equally probable in each beam range in each simulation.) AP omnidirectional broadcast range If the ratio of the directional transmission range radius is 1.5, the number of users residing outside the AP broadcast range is 0.44N, and the number of users residing outside the AP broadcast range is 0.56N.

In the simulation in this embodiment, it is assumed that the user's packets are sent outside the local area network, that is, the user's packets are all sent to the AP for forwarding, and the downlink service is randomly selected by the AP. The user sends it. The arrival process of the service packet from the upper layer to the MAC layer is a Poisson process. The packet arrival rate of each site is set to be the same, and the average arrives at λ packets per second. The packet arrival rate of ΑΡ reaches an average of Ν.λ packets per second, and each arriving packet randomly selects one user as the destination site. The simulation is implemented in the Visual C++ 6.0 environment.

In order to ensure the versatility and consistency of the simulation results, the simulation parameters used in the simulation of this embodiment are completely consistent with the parameters in the IEEE 802.11a international standard, as shown in Table 1.

Table 1 Table 2 and Table 3 show some of the results of the simulation of this embodiment. The number of user sites associated with the AP in the network is changed from 20 to 40. The beam widths of the smart antennas used are: δ= 90ο (the corresponding number of beams is: Β=4), δ=45ο (the corresponding number of beams is: Β=8) and δ=30ο (the number of beams corresponding to degrees is: Β=12), using the above four Access method Average latency of all site data packets and network normalized throughput. As shown in Table 2, when Ν=20~32, Β=4, Β=8 or Β=12, the performance of the (iii) d/d (competition) access method is optimal, that is, the average delay is the smallest. The highest throughput. When N=34 and B=4, the average delay of the (i)o/d (competition) access method is the smallest, and the throughput is the highest, that is, the performance is optimal. Similarly, the best performing access method among the four access methods corresponding to 情况, Β, can be obtained.

Thus, according to the contents of Table 2 and Table 3, the number of user sites in the network can be established. The correspondence between the two parameters of the directional beam width of the smart antenna and the optimal access method is as shown in Table 4. As shown in Table 4, where N is the number of user sites associated with the AP in the network, and B is the number of consecutive beams that can cover all spaces.

(Β=360ο/δ, δ is the directional beamwidth) Ν=20, Β=4 corresponds to (iii) d/d (competition) access method, ie when the number of user sites in the network is 20, the orientation adopted When the beam width is 360O/4 or 90°, the d/d (competition) access method performs optimally; similarly, when the number of user sites in the network is 34, the directional beamwidth used is 90ο o/d (competition) The access method has the best performance; when the number of user sites in the network is 40, the directional beamwidth is 90ο, the o/d (polling) access method performs optimally; when the number of user sites in the network is 40, The directional beamwidth used is 360O/8, that is, 45ο o/d (competition) access method performance is optimal.

According to this embodiment, when the AP determines the current number of user sites N=32, and the current number of directional beams used is B=4, the access network selects according to the corresponding relationship shown in Table 4.

(iii) d/d (competition) access method for access.

According to the embodiment, the beam width of the smart antenna configured by the AP may be changed or fixed. When the beam width of the smart antenna is variable, the method of the present invention can switch the access method according to different beam widths and network site sizes; when the beam width of the smart antenna is fixed, the method in the present invention is based only on the network site. The scale is adaptively switched.

The simulation method for establishing the correspondence between the two parameters of the number of user stations in the network and the directional beam width of the smart antenna used in the embodiment and the optimal access method is only exemplary, and is not used. This is a limitation of the invention. Average delay

N o/d (race) o/d (polling) d/d (race) d/d (polling)

B=4 20 5. 17 5. 77 0. 74 2. 99

22 5. 32 6. 01 0. 79 3. 47

24 5. 49 6. 27 0. 87 4. 04 :/:/ O 6εεο/-ο>1£ 6SS2800ZAV

28 0. 4926 0. 4926 0. 4927 0. 4926

30 0. 5277 0. 5278 0. 5279 0. 5279

32 0. 563 0. 563 0. 5631 0. 563

34 0. 5981 0. 5981 0. 5851 0. 5982

36 0. 6333 0. 6333 0. 5231 0. 6332

38 0. 6685 0. 6684 0. 5046 0. 6683

40 0. 7036 0. 7035 0. 4884 0. 7033

20 0. 3518 0. 3519 0. 3519 0. 3519

22 0. 3871 0. 387 0. 3871 0. 387

24 0. 4222 0. 4222 0. 4223 0. 4223

26 0. 4574 0. 4574 0. 4575 0. 4573

28 0. 4926 0. 4926 0. 4927 0. 4926

B=8 30 0. 5278 0. 5278 0. 5279 0. 5277

32 0. 563 0. 563 0. 563 0. 5629

34 0. 5982 0. 5981 0. 5982 0. 5976

36 0. 6333 0. 6332 0. 632 0. 5922

38 0. 6685 0. 6682 0. 6125 0. 5809

40 0. 7036 0. 684 0. 6055 0. 5857

20 0. 3518 0. 3519 0. 352 0. 3519

22 0. 3871 0. 3871 0. 3872 0. 3871

24 0. 4222 0. 4222 0. 4223 0. 4221

26 0. 4574 0. 4574 0. 4574 0. 4573

28 0. 4925 0. 4925 0. 4927 0. 4923

B=12 30 0. 5278 0. 5277 0. 5278 0. 526

32 0. 5629 0. 5628 0. 5631 0. 5361

34 0. 5981 0. 5979 0. 5983 0. 5465

36 0. 6333 0. 6283 0. 6334 0. 5582

38 0. 6686 0. 6105 0. 6451 0. 5612

40 0. 7036 0. 6239 0. 6352 0. 5756 Table 3

Optimal access method

N

B = 4 B = 8 B = 12

20 (iii) (iii) (iii)

22 (iii) (iii) (iii)

24 (iii) (iii) (iii)

26 (iii) (iii) (iii)

28 (iii) (iii) (iii) 30 (iii) (iii) (iii)

32 (iii) (iii) (iii)

34 (i) (iii) (iii)

36 (i) (i) (iii)

38 (i) (i) (i)

40 (ii) (i) (i)

(i): old (contest); (ii): old (polling); (iii): d/d (contest)

Table 4

In the embodiment of the present invention, referring to Table 4, the d/d (polling) method has not been used since it always has worse performance than other methods.

In this embodiment, when the beam width is fixed, the correspondence between the number of user sites and the access method with optimal performance includes:

In the case that the number of user sites in the network is small, that is, when the number of user sites is less than the preset first threshold, since the competition method can effectively obtain a relatively small delay, the d/d inside and outside the broadcast range is not distinguished ( The performance of the access method is optimal. As the number of stations increases and increases to a value greater than or equal to the first threshold but less than the second threshold, the performance of the contention method approaches saturation, and the delay performance begins to deteriorate. The broadcast range of the AP is internal or external to reduce the number of sites participating in the competition. At this time, the o/d (competition) access method performs optimally; if the number of network sites continues to increase, it increases to a second threshold or more, even if the distinction is made. The location of the site, the competition method is still close to saturation, and the performance is still deteriorating. In this case, the delay-controlled polling-based method performs better than the competitive method, at this time o/d (polling) access The method is optimal. In the case of a fixed number of beams, as the number of stations increases, the AP will switch the access method in the following order: d/d (race) → o/d (race) → o/d (Competition), that is, (iii) → (i) → (ii). In the present embodiment, when B=4, the first threshold is 34, the second threshold is 40; when B=8, the first threshold is 36; when B=12, the first threshold is 38.

According to the embodiment, in the case that the number of user sites in the network does not change, as the number of B increases, the number of sites participating in the competition within one beam range decreases, so that there may be more In the case of the site, a contention-based method is adopted, that is, a switching point in which the different access methods are switched according to the number of stations in the adaptive method is deferred, that is, as the number of users increases, the number of corresponding user stations switches. A threshold and a second threshold also increase accordingly. In the present embodiment, when B is increased from 4, 8 to 12, the access method switches from (iii) to (i) the number of corresponding stations is 34, 36, 38, respectively.

Step 103: The access point provides access to the user site by using the selected access method. After the access point selects the current optimal access method from the above four access methods in step 102, the access method is used to provide access to the user site in the step. Specifically, the access point may notify the surrounding user station to access the network through different beacon frames, and the beacon frame includes the destination site address as a non-competitive polling method, otherwise it is a competitive method. The beacon frame may be an omnidirectional beacon frame and a directional beacon frame or only a directional beacon frame, depending on the selected access method. The omni-directional beacon frame can only communicate with the internal user site of the omnidirectional broadcast range, and the directional beacon frame can notify all user sites within the directional beam range. User sites located within the AP omnidirectional broadcast only respond to omnidirectional beacon frames.

The following describes how to implement the above four access methods that can provide access to all user sites located within the directional transmission range of the access point in actual services.

In the actual service implementation, after using the smart antenna, the AP can provide access to surrounding user sites in a competitive manner and in a polling manner, that is, in a non-competitive manner.

4 is a flow diagram of an AP providing access by means of polling in an embodiment of the method of the present invention. As shown in Figure 4, the method for the AP to provide access by means of polling includes:

Step 201: The AP first sends a polling message including the destination site address.

Step 202: The destination station receives the polling message, and immediately sends an uplink packet response to the polling after receiving the message.

FIG. 5 is a schematic diagram of a process in which an AP provides access by using a contention method in an embodiment of the method of the present invention. As shown in Figure 5, the AP provides access by means of competition: Step 301: The AP sends a special polling packet that does not contain any specific destination address information.

Step 302: Multiple user stations receive the special polling packet and respond at the same time, and their responses collide at the AP.

Step 303: The AP starts a collision resolution mechanism to obtain all uplink packets.

6 is a diagram showing a protocol structure for an AP to provide access to a user site in a contending mode in a directional mode in an embodiment of the method of the present invention. As shown in Figure 6, the AP forms a continuous directional beam scan. The entire space starts from the beam Beam1 and determines that all users in one beam end the communication after the end of the communication until the beam BeamB (B is the number of beams). In the competition mode, the uplink and downlink are separated, that is, the packet confirmation is required regardless of whether the AP or the user station successfully transmits one data packet each time. As shown in Figure 6, each beam scanning period of the AP includes: an uplink period (ULP) and a downlink period DLP, and the ULP includes a plurality of contention resolution areas CRI. Among them, each collision decomposition process is called a competitive decomposition zone. 7 is a flow diagram of an AP providing access to a user site in a contending mode in a directional mode in an embodiment of the method of the present invention. As shown in Figure 7, the AP provides access to the user site in a contending mode in a directional mode, including:

Step 501: The AP sends a directional beacon frame (D_Beacon) that does not include the destination site address for initialization.

In step 502, all service stations in the beam immediately start a competitive response and enter the uplink period ULP.

Step 503: The AP determines whether a response of multiple user sites collides at the AP; if yes, step 504 is performed; otherwise, step 505 is performed.

Step 504: The AP initiates a collision resolution process to separate responses between user sites within a range of beams; and then performs step 505.

In this step, a method and tree for retransmitting a collision packet with a fixed retransmission probability p may be employed. A type decomposition algorithm, a first-come-first service decomposition algorithm, or a hybrid decomposition algorithm is used to decompose the collision group. Among them, each collision decomposition process is called a competitive decomposition interval CRI.

Step 505: Determine whether the AP wants to send the downlink service; if yes, go to step 506; otherwise, go to step 507.

Step 506: The AP sequentially sends a downlink data packet to each station in the beam range. After the sending, step 507 is performed.

Step 507: The AP sends a directed end frame to end the data communication process in the range of the beam.

Step 508, the AP starts scanning of the next beam, and repeats steps 501-507 until the entire space is covered.

FIG. 8 is a schematic diagram of a process in which an AP provides access to a destination user site located in a current directional beam range by using a polling mode in an directional mode. As shown in Figure 8, the method for the AP to provide access to the destination user site in the polling mode in the directional mode includes:

Step 601: The AP sends a directional beacon frame including a destination site address.

Step 602: The AP determines whether it receives the response from the destination station; if yes, executes step 604, otherwise, performs step 603.

In this step, if the destination site is within the current beam range, it responds to the directional beacon frame sent by the AP; if the destination site is not within the current beam range, the AP will not receive any information.

In step 603, the AP continues to scan the next beam range until the destination site is found. Then, step 604 is performed.

Step 604, the AP continues to scan the next destination site in the polling list.

FIG. 9 is a schematic diagram of a process in which an AP provides access to a destination station located in an omnidirectional transmission range by using a polling manner in an omnidirectional mode in the present invention. 10 is an embodiment of the present invention, the AP uses a polling mode in an omni mode to a destination site located in an omnidirectional transmission range. Provide a protocol structure diagram for access. As shown in FIG. 9, the method for the AP to provide access to the destination station located in the omnidirectional transmission range by using the polling mode in the omni mode includes:

Step 701: The AP sends an omnidirectional beacon frame including a destination site address.

Step 702: The AP sends a data-free polling packet, a data packet, or a composite packet of data and polling to the destination station.

Step 703: After receiving the polling packet from the AP, the destination user station sends a response packet to the AP. In this step, the response packet may be a dataless polling response packet ACK, or a composite packet Data+ACK of data and response. Or, if the destination site has no data to send, it also sends a null frame with no data back to the AP.

Step 704: After receiving the response packet from the destination station, the AP sends the receipt notification destination to the site that the uplink packet has been correctly received. In this step, after receiving the response packet from the destination site, the AP may send a Data+ACK+Poll packet to another station, where the ACK is used to acknowledge the data packet received by the previous AP.

In step 705, the AP will continue to send the polling packet, the data packet, or the composite packet of data and polling to the next station in the polling list, and repeat steps 703-704 until all stations in the list are polled.

If the destination user site in the omni-directional beacon frame sent by the AP is not within the current omnidirectional broadcast range, the AP will not receive any response packet from the site, and the AP will continue to poll the next destination site in the list. Sends a polling packet, a data packet, or a composite packet of data and polling.

For the o/d (competition) method, the AP may utilize a superframe structure combining an omnidirectional transmission period and a directional transmission period, and use the above-mentioned AP to poll the omnidirectional broadcast in the omni mode in the omnidirectional transmission period. The user sites in the range provide access, and provide access to user sites located outside the omnidirectional broadcast during the directional transmission period by utilizing the above-mentioned AP's contention mode in the directional mode.

Specifically, an example of implementing the O/D (race) method is given below. 11 is a superframe structure diagram of an omnidirectional transmission period and a directional transmission period generated by an AP. As shown in FIG. 11, the superframe is divided into two parts: an omnidirectional transmission period OTP for implementing communication in the omnidirectional broadcast range and a directional transmission period DTP for realizing omnidirectional broadcast out-of-range communication. The duration of the OTP loop interval is a manageable parameter that determines how often the OTP occurs. During a round-robin interval, part of the time is allocated to users in the omni-directional broadcast range, and the remaining time is allocated to users outside the omni-directional broadcast range. The OTP loop interval is initialized by the omni-directional beacon frame ( 0_Beacon ) sent by the AP. One of the main functions of the 0_Beacon is synchronization and timing. The AP determines the working time of the OTP in any cyclic interval. The maximum duration of the OTP is defined as the parameter OTP_Max. If the traffic is very light, the AP can shorten the OTP and leave more time to the DTP.

At the beginning of the omni-directional transmission period, the AP sends a 0_Beacon for initialization, and then starts the uncontested transmission, including the data-free polling frame, the data frame, or the composite frame of data and polling. FIG. 12 shows a typical frame structure of an omnidirectional transmission period, where D represents a downlink data frame sent by the AP, U represents an uplink data frame sent by the user, ACK represents a response to the data frame, and Poll represents an AP-to-user round. Inquiry. A station starts responding after receiving a polling frame from the AP, and the response frame may be a dataless polling acknowledgement frame ACK or a composite frame Data+ACK of data and response. If the AP receives a Data+ACK from one station, the AP may send a Data+ACK+Poll frame to another station, where the ACK is used to acknowledge the data frame received by the previous AP. A composite frame that sends polls, replies, and data between the AP and the site is designed to increase the efficiency of the communication. If the AP sends a polling frame Poll and the destination station has no data to send, the destination station sends a null frame with no data (Null) back to the AP. If the AP does not receive an acknowledgement ACK for the data frame, the AP continues to send to the next station in the polling list. If the omni-directional transmission period service ends (the polling list has been emptied) or the omni-directional transmission period transmission time reaches the maximum value OTP_Max, the AP immediately suspends the transmission of the omni-directional service by transmitting an omni-directional end frame (0_End). The polling mechanism employed during the omni-directional transmission period is described below. At the beginning of each OTP, the AP adds all the broadcast-wide sites to the polling list, and then the AP sends Poll frames in turn to poll each station in the order of the polling list. When the AP polls a station, if the AP sends downlink data to the station, it can send the poll frame in the form of a composite frame of Data+Poll. In this polling mechanism, the AP provides a counter to each site to add to the polling list. At the beginning of each OTP, the counter value of all stations is set to zero. In the OTP period, the AP sends a Poll frame to one station and the station responds to the AP-empty frame, and the AP increments the corresponding site counter value by one. When the counter value reaches a predetermined value (called K, that is, a station has no data to send or receive after K rounds of polling), the AP deletes the corresponding station from the polling list. When all stations are deleted from the polling list or the timing has reached the OTP maximum duration OTP_Max, the AP saves the information of the last polling site. Then, in the next OTP period, the AP again adds all the sites in the broadcast range to the polling list, and continues to poll from the last last polled site. In addition, in addition to the above-described counter-based polling method, other polling methods that can achieve the same function, such as the polling method of the point coordination function (PCF) not explicitly defined in the IEEE802.il protocol, can be employed.

During the directional transmission period, the AP forms a continuous directional beam to scan the entire space, and determines that all users in one beam end the scanning of the next beam after the communication ends. As shown in Fig. 13, a typical frame structure diagram of a directional transmission period is shown. In the directional transmission period, the uplink and downlink are separated, that is, the response frame confirmation is required regardless of whether the AP or the station successfully transmits one data frame each time. At the beginning of each beam-oriented transmission period, the AP sends a directional beacon frame (D_Beacon) for initialization, and the service station within the beam immediately begins a competitive response and enters the ULP. If more than one user responds at the same time, a collision occurs at the AP, and the AP then initiates a collision resolution process to separate the responses between users and ensure uplink communication success. Each collision decomposition process is called a contention resolution interval. , CRI ), its detailed collision decomposition process will be described below. ULP junction after successful collision resolution within a beam range Bunch. If the AP has a downlink service to send, it enters a downlink period (DLP), and the AP sequentially sends a downlink data frame to each station in the beam range. After the downlink communication ends, the AP sends an directional end frame (End) to end the data communication process in the beam range. At this point, the directional communication process in one beam ends, and then the directional transmission in the next beam range is started until the DTP is terminated. The AP records the beam information at this time. In the next DTP period, the AP continues to scan the entire space from the last last scanned beam. If the DTP has not ended after the entire spatial scan is over, the scanning from the first beam is resumed.

Figure 14 is a time slot structure diagram of a CRI. As shown in Figure 14, each CRI contains L contention slots. At the beginning of a CRI, the AP directionally sends a directional beacon frame (D_Beacon), which does not contain any user address. Each user in the current beam with uplink service immediately responds to a data frame containing the preamble sequence and the user address. . If only one user sends uplink data, the AP can correctly receive and obtain the spatial characteristics of the user through the preamble sequence. At this time, the AP sends a response message (ACK) to the user to notify that the reception has succeeded. However, if there are multiple users in the beam range, their uplink data collides at the AP, and the AP will not be able to send an ACK message, and the user knows that the collision has occurred and then proceeds to the next competition. Collision decomposition can be performed by a single method: each collision user retransmits with a probability p in the subsequent L time slots of the CRI. If only one user in a time slot transmits, the user resolves successfully, and then the AP sends The ACK message informs the user of the success, which will delay the transmission of the user in the next time slot; if no user sends the uplink data frame after the D_Beacon, the AP considers that there is no user in the current beam or all users have been decomposed in the previous time slot, and then The AP ends the transmission of the uplink period ULP; if a CRI times out, the AP starts the next CRI and transmits a 0_:86&0)11 again; the process is repeated until the AP is instructed that all users in the current beam are successfully decomposed. In Figure 14, L is 6, two users compete, the first time slot collides, the next three time slots are idle, and the last two time slots After successful transmission, after two CRIs, the AP knows that the collision was successfully decomposed.

In the access method, there are two beacon frames (Beacon), which are an omnidirectional beacon frame (0_Beacon) and a directional beacon frame (D_Beacon). The user site needs to distinguish the type of the received beacon frame. If the 0_Beacon is received, the site is in the AP broadcast range, and the received D_Beacon can be ignored. Otherwise, the site is outside the AP broadcast range. To send, respond to D_Beacon, as this marks the beginning of a race period within a beam range.

For the o/d (polling) method, referring to the implementation of the above o/d (competition) method, the AP can utilize the superframe structure combining the omnidirectional transmission period and the directional transmission period, and utilize the above AP in the omnidirectional transmission period. The polling mode in the omnidirectional mode provides access to user sites in the omnidirectional broadcast range, and provides the user site in the omnidirectional broadcast range by using the above-mentioned polling mode of the AP in the directional mode during the directional transmission period. Access.

For the d/d (competition) method, the AP can provide access to all user sites located within the directional transmission range by using the above-mentioned AP's contention mode in the directional mode and the slot structure of the above-mentioned competitive decomposition interval.

For the d/d (Polling) method, the AP can provide access to all user sites located within the directional transmission range by using the above-mentioned AP polling mode in the directional mode.

Example 2:

Figure 15 is a flow chart showing Embodiment 2 of the present invention. Referring to FIG. 15, the media access control method for supporting a smart antenna in this embodiment includes the following steps:

In step 1301, the access point determines the number of user stations currently associated with it and the width of the directional beam it is currently using for scanning.

Step 1302: The access point selects the performance according to the current number of user sites and the directional beamwidth according to the correspondence between the two parameters of the pre-established number of user sites and the directional beamwidth and the optimal access method. The optimal access method. Step 1303: The access point provides access to the user site by using the selected access method. Step 1304: In the process of communicating between the access point and the user site, the access point determines whether at least one of the number of user stations associated with the current network and the beam width used by the access network changes; if yes, execute Step 1305; Otherwise, proceeding to step 1303, the access point maintains access to the user site using the current access method.

Step 1305, the access point determines whether the currently used access method is: an optimal access method corresponding to the changed number of user stations and the directional beamwidth; if yes, proceeds to step 1303, the access point Maintain access to the user site using the current access method; otherwise, go to step 1306.

Step 1306: The access point switches to correspond to the changed number of user stations and the directional beamwidth according to the correspondence between the two parameters of the pre-established number of user sites and the directional beamwidth and the optimal access method. The best performance access method.

Steps 1301 to 1303 of this embodiment are the same as steps 101 to 103 of the first embodiment. In the specific implementation of the embodiment, in the process of communication between the AP and the user site, if a new site joins, the AP may obtain the registration information of the site through the association of the site, thereby knowing that N is increased; The polling of the exiting site will not respond, so that N is reduced. In the next beacon frame, the AP will adaptively switch the access policy according to the changed N, and so on.

In addition, the present invention also proposes an access point device. FIG. 16 is a schematic diagram of the basic structure of Embodiment 1 of an access point device according to the present invention. Referring to FIG. 16, the basic structure of the access point device of the present invention includes: a smart antenna unit, a determining unit, a storage unit, a processing unit, and an access unit, where the smart antenna unit is configured to transmit a continuous directional beam with a predetermined beamwidth. a scanning network space; a determining unit, configured to determine a number of user sites currently associated with the access point device and a width of the directional beam used by the smart antenna unit for scanning; and a storage unit, configured to store the pre-established number of user sites and orientation Two parameters of beam width and optimal performance access Corresponding relationship between the methods; a processing unit, configured to select, according to the number of user sites and the directional beamwidth determined by the determining unit, and the corresponding relationship stored in the storage unit, to adopt the current number and orientation of user sites An access method with optimal performance under the beam width; an access unit, configured to provide access to the user site by using an access method selected by the processing unit.

FIG. 17 is a schematic structural diagram of Embodiment 2 of an access device according to the present invention. Referring to FIG. 17, the processing unit further includes: a switching unit, configured to determine, in the two parameters, the number of user stations associated with the access point device and the directional beam width of the smart antenna unit for scanning the network space. Whether at least one change; if yes, further determining whether the currently used access method is: an optimal access method corresponding to the changed number of user stations and directional beamwidth, and if so, the access point Maintaining the current access method. Otherwise, the access point switches to the changed user site according to the correspondence between the two parameters of the number of user sites and the directional beam width and the optimal access method. The optimal number of access methods corresponding to the number and directional beamwidth.

The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalents, improvements, etc., which are included in the spirit and scope of the present invention, should be included in the present invention. Within the scope of protection.

Claims

Claim

A media access control method for supporting a smart antenna application, the method comprising:

The method according to claim 1, wherein the correspondence between the two parameters of the number of user stations and the directional beam width and the access method with the best performance is preset in the access point. .

The method according to claim 1, wherein the correspondence between the two parameters of the number of user stations and the directional beam width and the access method with the best performance is implemented as follows: A list of the number of user sites, the directional beamwidth of the predetermined value, and the performance-optimized access method corresponding to the number of user sites and the directional beamwidth.

The method according to claim 1, wherein after the access point provides access to the user site by using the selected access method, the method further includes:

During the communication between the access point and the user site, the access point determines whether at least one of the two parameters of the number of user stations associated with it and the width of the directional beam used for scanning changes; if yes, The access point further determines whether the currently used access method is: an optimal access method corresponding to the changed number of user sites and the directional beamwidth, and if so, the access point maintains the current access method, Otherwise, the access point is based on The correspondence between the two parameters of the number of user sites and the directional beam width and the optimal access method is switched to the performance-optimized access corresponding to the changed number of user sites and the directional beamwidth. method.

The method according to any one of claims 1 to 4, wherein the optimal access method is selected from the following access methods:

The access point provides access to the user site located in its omnidirectional broadcast range by polling in the omni mode, and in the directional mode for the user site located outside its omnidirectional broadcast range and within its directional transmission range. The method of accessing the o/d (competition) access method for access;

The access point provides access to the user site located in its omnidirectional broadcast range by polling in the omni mode, and in the directional mode for the user site located outside its omnidirectional broadcast range and within its directional transmission range. The next round of polling provides access to the o/d (polling) access method;

The access point provides access to the d/d (competition) access method for all user sites located within its directional transmission range in a manner that competes in a directed mode;

The access point provides access to the d/d (Poll) access method for all user sites located within its directional transmission range by polling in directional mode.

The method according to claim 5, wherein, for a fixed-size directional beam width, a correspondence between the number of user sites and an access method with optimal performance includes:

When the number of the user sites is less than a preset first threshold, the d/d (competition) access method performs optimally;

When the number of the user sites is greater than or equal to a preset first threshold and less than a preset second threshold, the o/d (competition) access method performs optimally;

When the number of user sites is greater than the preset second threshold, the o/d (polling) The access method has the best performance;

The first threshold is smaller than the second threshold.

The method according to claim 5, wherein the step of the access point providing access to the user site by using the selected access method comprises: sending, by the access point, a beacon frame to notify the user of the site Access to the network.

8. The method according to claim 7, wherein the access point provides access to an omnidirectional mode for a user site located in its omnidirectional broadcast range, and is located in its omnidirectional broadcast range. When the user site outside the directional transmission range provides access in a directional mode, the access point sends the beacon frame to notify the user that the site accesses the network, including:

The access point sends an omni-directional beacon frame to inform the user station access network within its omnidirectional broadcast range; and

The access point sends a directional beacon frame to inform the user station access network within its directed broadcast range;

When the access point provides access to all user sites located in its directional transmission range in a directional mode, the step of the access point transmitting the beacon frame to notify the user that the site accesses the network includes:

The access point sends a directional beacon frame to inform the user station access network within its directed broadcast range.

a smart antenna unit, configured to transmit a continuous directional beam scanning network space with a predetermined beamwidth;

a determining unit, configured to determine a number of user sites currently associated with the access point device and a width of the directional beam used by the smart antenna unit for scanning; a storage unit, configured to store a correspondence between two parameters of a pre-established number of user sites and a directional beam width and an access method with optimal performance;

The access point device according to claim 9, wherein the processing unit further comprises: a switching unit, configured to determine, by the determining unit, the number of user sites associated with the access point device and the smart And determining, by the antenna unit, whether at least one of the two parameters of the directional beam width of the network space is changed; if yes, determining whether the currently used access method is: according to the corresponding relationship stored in the storage unit: The number of user sites and the directional beamwidth corresponding to the performance-optimized access method. If yes, the access point maintains the current access method. Otherwise, the access point switches to the change according to the corresponding relationship. The number of user sites and the directional beamwidth correspond to the performance-optimized access method.