CN104540172A - Unit area load balancing method based on position consciousness in WLAN system - Google Patents

Abstract

The invention discloses a unit area load balancing method based on position consciousness in a WLAN system. The unit area load balancing method comprises the steps that a station STA sends a Probe Request to surrounding access points (AP); the APs receiving the Probe Request sent by the STA feed back the emitting power of themselves, the load information of the current APs and the like to the STA through a Probe Response; the STA decides a target AP needing to be associated by adopting a local unit area load balancing strategy according to the received AP information carried by the Probe Response and the received signal strength indicator (RSSI) receiving the Probe Response. The invention further discloses an interference avoidance method based on the position consciousness. The APs dynamically adjust the emitting power according to associated STA position information so that interference between the adjacent APs can be reduced. The unit area load condition of the APs and the RSSI of the STA are considered to achieve load balance, meanwhile, interference avoidance is carried out based on the position information of the STA, resources of a whole network can be fully utilized, and meanwhile system performance is improved.

Description

The unit are load-balancing method of position-based consciousness in a kind of wlan system

Technical field

The present invention relates generally to wireless communication field, particularly relates to the load balancing in wlan system and interference avoidance technique.

Background technology

Along with the develop rapidly of WLAN (wireless local area network) WLAN (Wireless LAN) technology, WLAN (wireless local area network) obtains widespread deployment, wireless STA (Station) also gets more and more, the time-varying characteristics of wireless channel and the flexible mobility of STA, wlan network loading condition can constantly be changed, so, in large-scale structure of the WLAN, how to carry out efficient association between site STA and access point AP (Access Point), the performance of whole network and resource utilization are had a significant impact.

The method of traditional STA access network normally STA selects received signal strength indicator RSSI (Received Signal Strength Indication) the maximum AP scanned to connect, then based on related protocol access wlan network, but the position disposed due to each AP is different, some AP are in hotspot location, the STA Numerous of association, there is the phenomenon of overload, cause that bandwidth resources block, STA can not access network in time; The AP of some remote location then associates the seldom STA of number, causes bandwidth resources to waste, and from the angle of whole network resource utilization and user's request, this situation obviously will do one's utmost to avoid.So how realizing the load balancing in wlan system between AP, is the key improving whole network resource utilization and guaranteed qos.

Load-balancing technique is just used to balance the load difference between AP, improves the resource utilization of wireless network, and increases the throughput of network.Load balancing is exactly allow the STA scanning multiple AP, not select the maximum AP of RSSI to associate blindly when being linked into wireless network, but select suitable AP to associate by certain load balancing, thus the load difference reduced between AP, realize making full use of of bandwidth resources, improve the resource utilization of network.

On the other hand; for the WLAN (wireless local area network) that an AP density is higher; the AP of multiple vicinity can use same channel usually; due to the dense deployment of AP; the coverage of each AP can be overlapped; so not only can cause energy dissipation, also can cause the mutual interference between AP, affect performance and the communication quality of whole system.In wlan system, a kind of method reducing interference is, by the coverage of the transmitting power adjustment AP of each AP of adjustment, can reduce the overlapping region of adjacent AP coverage, thus reduce interference.

Summary of the invention

Goal of the invention: the unit are load-balancing method that the object of the present invention is to provide position-based consciousness in a kind of wlan system, can solve under WLAN environment, the resource utilization that between each AP, load imbalance causes is low, the problem that user's request is not being met, and a kind of interference avoidance method is provided further, the dense deployment that can solve due to AP causes the overlapped energy dissipation that causes of the coverage of each AP and problem of co-channel interference, contribute to the resource utilization improving wlan system, reduce the interference between AP, improve system system energy simultaneously.

Technical scheme: the unit are load-balancing method of position-based consciousness in a kind of wlan system, comprises the steps:

(A1) site STA peripherad access point AP broadcast probe request frame;

(A2) AP receives the probe requests thereby that STA sends, send probing response frame to this STA, feedback information comprise received signal strength indicator RSSI (Received Signal Strength Indication), AP current accessed load, the current transmitted power of AP, the antenna gain of AP and the deployment height of AP;

(A3) STA indicates according to the signal strength signal intensity of the probe response received, and the load capacity of AP, current transmitted power, antenna gain and deployment height, based on the unit are load balancing of this locality, determines the target AP needing association;

(A4) STA and target AP perform verification process, and after authentication success, STA sends association request frame to target AP;

(A5), after target AP receives association request, association response frame is sent to STA;

(A6) if the association request of target AP refusal STA, then STA is according to the load balancing in step (A3), in the AP except this AP, reselect the target AP needing association, and perform step (A4) ~ (A5); If target AP receives the association request of STA, then enter step (A7);

(A7) STA successfully accesses WLAN, the webserver by AP for STA provides service.

Preferably, the unit are load balancing of this locality in described step (A3) is specially:

The AP that STA selects following formula intermediate value maximum as target AP,

$\begin{array}{c}\mathrm{tar}\_\mathrm{AP}=\max \left\{\frac{{\mathrm{RSSI}}_i\·\mathrm{\π}\left({10}^{({\mathrm{TxPower}}_i+{\mathrm{AntennaGain}}_i-{\mathrm{RSSI}}_{\min }-{\mathrm{PL}}_{1\mathrm{Meter}}-s)/5n}\right)-h_i^2}{N_i}\right\},\\ i=\mathrm{1,2},\·\·\·,M\end{array}$

Wherein, RSSI _irepresent the received signal strength indicator of the probe response that i-th AP that STA receives sends, TxPower _irepresent the current transmit power of i-th AP; AntennaGain _irepresent the antenna gain of i-th AP, N _irepresent the total load number of access i-th AP, M represents the AP number that STA scans, RSSI _minrepresent the sensitivity of STA received signal strength indicator, PL _1Meterpath loss when representing that transmission path is 1 meter between AP and STA, n represents path loss index, and s represents the deviate relevant with shadow fading degree, h _irepresent the deployment height of i-th AP.

Further, the interference between adjacent AP, said method also comprises the positional information of AP based on STA, the step of dynamic conditioning transmitting power, and this step comprises:

(B1) range information of oneself distance AP and received signal strength indicator sensitivity are sent to the AP associated with it by STA;

(B2) positional information fed back according to each associated STA of AP, calculates the minimum emissive power that all STA of covering associated need;

(B3) AP arranges transmitting power according to the calculated value of power in step (B2);

(B4) transmitting power after adjustment is broadcast to STA, the STA associated therewith transmitting power according to the power adjustment of the AP received oneself by AP.

Preferably, described range information passes through formula

$d={10}^{({\mathrm{TxPower}+\mathrm{AntennaGain}-\mathrm{RSSI}-\mathrm{PL}}_{1\mathrm{Meter}}-s)/10n}$ Calculate.

Preferably, described minimum emissive power passes through formula

$P_{\min }={\mathrm{RSSI}}_{\min }+{\mathrm{PL}}_{1\mathrm{Meter}}+10\log \left(D_{\max }^n\right)+s-\mathrm{AntennaGain}$ Calculate, wherein D _maxfor the maximum in all STA and AP distances, RSSI _minthe received signal strength indicator sensitivity of the STA that maximum range value is corresponding.

Further, in order to prevent the load balancing of the mobile destruction system of STA, said method also comprises the step going when STA moves to associate, and this step comprises:

(C1) STA detects oneself and whether occurs effective movement, when STA detects that its received signal strength indicator RSSI value is less than the received signal strength indicator sensitivity RSSI of this STA _mintime, then STA judges that existing effect is mobile;

(C2) when STA occurs effectively mobile, STA initiatively sends to the AP of association and removes disassociation frame, disconnects existing connection;

(C3) AP re-starts power adjustment according to step (B2) ~ (B4).

Beneficial effect: the unit are load balancing that in a kind of wlan system that the present invention proposes, position-based is realized and interference avoidance method, load-balancing method different from the past, equilibrium is carried out in the unit are load considering each AP, and balance policy is more comprehensive.And, load balancing scheme is in the past all generally that STA selects the maximum AP of received signal strength indicator RSSI first to associate networking, and then consider load balancing, carry out the switching of STA between AP, the method for decision-making after this first association, can affect the friendly of Consumer's Experience, and the unit are load-balancing method that the present invention proposes, be then the right to choose of load balancing is given the new STA networked, just take into account the problem of load balancing before association, above-mentioned deficiency can be avoided.

On the other hand, the energy dissipation caused for AP dense deployment in WLAN (wireless local area network) and interference problem, the present invention proposes the interference avoidance method of a kind of position-based consciousness, by the Radio Network System after load balancing, the transmitting power of AP is not optimized, overlap unnecessary between adjacent AP coverage can be caused, in the present invention, STA by current location information report to AP, AP just can know apart from oneself AP position farthest, then the minimum emissive power covering all STA associated therewith is calculated, so both ensure that the communication service to STA, transmitting power can be saved again, while conserve energy, the interference between AP can also be reduced.Simultaneously, in wireless local area network (WLAN) system, STA can move at any time, and the movement of STA can destroy the load balancing of system, present invention contemplates that this situation, when STA needs mobile, initiatively go operation associated to AP transmission, terminate this existing association, after STA moves to destination, need re-accessing network, according to load balancing above and power regulation scheme, realize the networking demand of this STA.

Accompanying drawing explanation

Fig. 1 is the flow chart of the unit are load-balancing method of position-based of the present invention consciousness.

Fig. 2 is the flow chart of the interference avoidance method of position-based of the present invention consciousness.

Fig. 3 is based on the mobile method flow diagram going to associate in the inventive method.

Fig. 4 is the schematic diagram of the WLAN (wireless local area network) be made up of fat AP.

Fig. 5 is AP coverage schematic diagram.

Message interaction process schematic diagram when Fig. 6 is STA accessing WLAN.

Fig. 7 is the loading condition schematic diagram not having each AP of the WLAN (wireless local area network) of working load balance policy.

Fig. 8 is the loading condition schematic diagram of each AP of WLAN (wireless local area network) using unit are load balancing of the present invention.

Fig. 9 uses the interference avoidance method that the present invention is based on position consciousness, the coverage schematic diagram after AP Modulating Power.

Embodiment

Below in conjunction with Figure of description, in a kind of wlan system provide the embodiment of the present invention, the unit are load balancing of position-based consciousness and the embodiment of interference avoidance method are described.Should understand this embodiment to be only not used in for illustration of the present invention and to limit the scope of the invention, after having read the present invention, the amendment of those skilled in the art to the various equivalent form of value of the present invention has all fallen within right appended by the application.

Fig. 4 is a WLAN (wireless local area network) be typically made up of fat AP, and data are by the transmission of radio links between STA and AP, and AP is interconnected by compartment system (DS), is linked into server (Server) by cable network.The message interaction process of Fig. 6 when to be STA be linked into wireless network by AP.The present invention is based on the wireless local area network (WLAN) system of Fig. 4, select to consider AP current unit are load balancing during the AP that will connect at STA, the overlapped energy dissipation that causes simultaneously considering AP coverage and interference, dynamic power adjustment is carried out to the AP after load balancing, to reduce the co-channel interference between AP, as shown in Figure 1, in a kind of wlan system of providing of the embodiment of the present invention, the unit are load-balancing method of position-based consciousness specifically comprises the following steps:

Step 101:STA is by the AP around scanning discovery.According to the regulation of IEEE 802.11 wireless standard, STA is when receiving MLME-SCAN.request primitive, be about to begin scanning, MLME-SCAN.request primitive parameter and implication as shown in table 1, here we specify that STA performs active scan mode, and the peripherad AP of STA initiatively sends Probe Request frame;

Table 1MLME-SCAN.request primitive parameter table

Step 102:AP receives the Probe Request that STA sends, to this STA uni-cast probe response ProbeResponse frame, AP by current access load, the current transmit power of AP, AP antenna gain and AP deployment height inform to this STA;

Step 103:STA is according to the Probe Response signal strength signal intensity instruction RSSI received, and the deployment height of the load capacity of the AP carried in ProbeResponse, AP current transmit power, AP antenna gain and AP, based on the load balancing of this locality, determine the target AP needing association.Detailed process is as follows:

The signal cover of AP can be provided by following path loss model

PL=PL _1Meter+ 10log (d ⁿ)+s (formula 1)

RSSI=TxPower+AntennaGain-PL (formula 2)

Wherein, PL represents path loss total between AP and STA, unit dB; PL _1Meterpath loss when representing that transmission path is 1 meter between AP and STA, unit dB, wireless STA are based on supported wireless standard, and unit path loss value generally can be integrated in hardware chip; D represents the actual range between AP and STA; N is the path loss index under varying environment, and under spacious environment, n generally gets 2, and under indoor environment, n generally gets 3.5 ~ 4.5; S is the deviate relevant with shadow fading degree, generally gets 3 ~ 7dB; TxPower is the current transmit power of AP; AntennaGain is the antenna gain of AP, and different AP equipment, antenna gain has corresponding desired value.

By formula (1) and formula (2), the signal maximum transmission distance between AP and STA just can be expressed as

$d_{\max }={10}^{({\mathrm{TxPower}+\mathrm{AntennaGain}-\mathrm{RSS}{I}_{\min }-\mathrm{PL}}_{1\mathrm{Meter}}-s)/10n}$ (formula 3)

Wherein RSSI _minthe signal strength signal intensity that expression STA receives the Probe Response that AP sends indicates the minimum value that can identify, different wireless devices, have a receiving signal sensitivity, the minimum signal strength that such as generally can identify based on the wireless device of IEEE802.11g agreement is at about-74dBm.

Therefore, when the deployed position of AP is determined, be aware of the maximum transmission distance of AP signal, also just can determine the coverage of AP.As shown in Figure 5, the deployed position of AP is generally (as the positions such as ceilings) determined, and therefore the height h on AP distance ground is exactly known, calculates the maximum transmission distance d of AP signal under current transmit power in formula (3) _max, then the area S that AP can cover in the horizontal direction can calculate (ignoring the height problem of STA herein) by formula (4):

$\begin{array}{c}S=\mathrm{\π}(d_{\max }^2-h^2)\\ =\mathrm{\π}({10}^{({\mathrm{TxPower}+\mathrm{AntennaGain}-\mathrm{RSSI}}_{\min }-{\mathrm{PL}}_{1\mathrm{Meter}}-s)/5n}-h^2)\end{array}$ (formula 4)

The load of order access AP adds up to N, then the calculation expression of unit are load unit_load is:

$\begin{array}{c}\mathrm{unit}\_\mathrm{load}=N/S\\ =\frac{N}{\mathrm{\π}({10}^{({\mathrm{TxPower}+\mathrm{AntennaGain}-\mathrm{RSSI}}_{\min }-{\mathrm{PL}}_{1\mathrm{Meter}}-s)/5n}-h^2)}\end{array}$ (formula 5)

Therefore consider the local balance policy of the unit are load unit_load of received signal strength indicator RSSI and AP, can be formulated as:

$\begin{array}{c}\mathrm{tar}\_\mathrm{AP}=\max \left\{\frac{{\mathrm{RSSI}}_i}{\mathrm{unit}\_{\mathrm{load}}_i}\right\}\\ =\max \left\{\frac{{\mathrm{RSSI}}_i\·\mathrm{\π}({10}^{({\mathrm{TxPower}}_i+{\mathrm{AntennaGain}}_i-{\mathrm{RSSI}}_{\min }-{\mathrm{PL}}_{1\mathrm{Meter}}-s)/5n}-h_i^2)}{N_i}\right\}i=\mathrm{1,2},\·\·\·,M\end{array}$

(formula 6)

Wherein RSSI _irepresent the Probe Response signal strength signal intensity instruction that i-th AP that STA receives sends; TxPower _iit is the current transmit power of i-th AP; AntennaGain _iit is the antenna gain of i-th AP; N _irepresent the total load number of access i-th AP; M represents the AP number that STA scans; h _irepresent the deployment height of i-th AP.The AP that STA selects formula (6) intermediate value maximum is as target AP.

Step 104:STA and target AP perform verification process, and STA sends association request Association Request frame to target AP;

Step 105: after target AP receives association request, the maximum load according to AP limits, determines whether accept, and sends associated response Association Response frame to this STA;

Step 106: if target AP sends associated response to STA, the association request of refusal STA, then STA is according to the load balancing in step 103, reselect the target AP except this AP, and carry out step 104 ~ 105; If target AP sends associated response to STA, accept the association request of STA, then carry out step 107;

Step 107: distributed system DS connect server S erver by AP for STA provides service.

Meanwhile, the overlapped energy dissipation that causes considering AP coverage and interference, carry out dynamic power adjustment to the AP after load balancing, to reduce the co-channel interference between AP, as shown in Figure 2, concrete steps comprise:

After step 201:STA is linked into wlan network, communicate with the AP associated, the range information of oneself distance AP and received signal strength indicator sensitivity are reported to AP;

The positional information that step 202:AP feeds back according to each associated STA, calculates the coverage distance AP minimum emissive power P required for STA farthest _min, detailed process is:

The intensity instruction RSSI of the current transmit power that STA feeds back according to AP, the antenna gain of AP and STA Received signal strength, by formula below, just can calculate the distance of this STA distance AP.

$d={10}^{({\mathrm{TxPower}+\mathrm{AntennaGain}-\mathrm{RSSI}-\mathrm{PL}}_{1\mathrm{Meter}}-s)/10n}$ (formula 7)

The each STA associated with AP when carrying out information interaction with AP by the received signal strength indicator sensitivity RSSI of the distance of oneself distance AP and this STA _minbe reported to AP, AP selects the maximum D in all distances _max, and the RSSI of corresponding STA _minvalue, substituting into formula (2) namely has:

$\begin{array}{c}{P}_{\min }={\mathrm{RSSI}}_{\min }+\mathrm{PL}-\mathrm{AntennaGain}\\ ={\mathrm{RSSI}}_{\min }+{\mathrm{PL}}_{1\mathrm{Meter}}+10\log \left(D_{\max }^n\right)+s-\mathrm{AntennaGain}\end{array}$ (formula 8)

It is P that step 203:AP arranges transmitting power _min;

Step 204:AP is by the transmitting power P after adjustment _minbe broadcast to STA, the STA associated therewith transmitting power according to the power of the AP received corresponding adjustment STA.

Meanwhile, consider that in WLAN, STA can move at any time, the movement of STA can destroy the load balancing of system, and carry out operation associated when STA effectively moves, as shown in Figure 3, concrete steps comprise:

Step 301:STA detects oneself and whether occurs effective movement, and STA is when mobile, and its received signal strength indicator RSSI meeting respective change, when STA detects that its RSSI value is less than the received signal strength indicator sensitivity RSSI of this STA _mintime, then STA judges that this moves as effective movement;

Step 302: based on step 301, when STA occurs effectively mobile, STA initiatively sends to the AP of current association and removes disassociation frame, disconnects existing connection; .

Step 303: after going association, AP performs step 202 ~ step 204, re-starts power adjustment;

After STA moves to destination, need re-accessing network, then perform the access process of step 101 ~ 107, and the power adjustment flow process of step 201 ~ 204, realize again networking and power adjustment being carried out to the AP of associated of this STA.

Fig. 7 represents when not having working load balance policy, the loading condition schematic diagram of each AP in wlan system.Can find that the load of AP1 is very heavy, AP3 load is comparatively light, and AP2 is only associated with two STA, and load is the lightest, and this load imbalance phenomenon, can cause the wasting of resources of AP2 and AP3, and AP1 may occur that resource blocks, and even can not meet consumers' demand in time.Fig. 8 is the loading condition schematic diagram using each AP of load balancing provided by the invention, and STA, when accessing wlan network, take into account the unit are load balancing of AP, therefore the load relative equilibrium of each AP.Fig. 9 is the range information that each AP feeds back according to STA, coverage schematic diagram after dynamic conditioning power, can find out, each AP when do not affect provide service to STA, suitable reduction transmitting power, can reduce interference that the overlapped coverage between adjacent AP causes and energy dissipation.

It should be pointed out that under the premise without departing from the principles of the invention, those skilled in the art can also make some improvement to the present invention, and these improvement also should be considered as protection scope of the present invention.

Claims (6)

1. the unit are load-balancing method that in wlan system, position-based is realized, is characterized in that, comprise the steps:

(A1) site STA peripherad access point AP broadcast probe request frame;

(A2) AP receives the probe requests thereby that STA sends, and sends probing response frame to this STA, feedback information comprise received signal strength indicator, AP current accessed load, the current transmitted power of AP, the antenna gain of AP and the deployment height of AP;

(A3) STA indicates according to the signal strength signal intensity of the probe response received, and the load capacity of AP, current transmitted power, antenna gain and deployment height, based on the unit are load balancing of this locality, determines the target AP needing association;

(A4) STA and target AP perform verification process, and after authentication success, STA sends association request frame to target AP;

(A5), after target AP receives association request, association response frame is sent to STA;

(A6) if the association request of target AP refusal STA, then STA is according to the load balancing in step (A3), in the AP except this AP, reselect the target AP needing association, and perform step (A4) ~ (A5); If target AP receives the association request of STA, then enter step (A7);

(A7) STA successfully accesses WLAN, the webserver by AP for STA provides service.

2. the unit are load-balancing method that in wlan system according to claim 1, position-based is realized, it is characterized in that, the unit are load balancing of this locality in described step (A3) is specially:

The AP that STA selects following formula intermediate value maximum as target AP,

$\mathrm{tar}\_\mathrm{AP}=\max \left\{\frac{{\mathrm{RSSI}}_i\·\mathrm{\π}({10}^{({\mathrm{TsPower}}_i+{\mathrm{AntenaGain}}_i-{\mathrm{RSSI}}_{\min }-{\mathrm{PL}}_{1\mathrm{Meter}}-s)/5n}-h_i^2)}{N_i}\right\},$

i＝1,2,…,M

Wherein, RSSI _irepresent the received signal strength indicator of the probe response that i-th AP that STA receives sends, TxPower _irepresent the current transmit power of i-th AP; AntennaGain _irepresent the antenna gain of i-th AP, N _irepresent the total load number of access i-th AP, M represents the AP number that STA scans, RSSI _minrepresent the sensitivity of STA received signal strength indicator, PL _1Meterpath loss when representing that transmission path is 1 meter between AP and STA, n represents path loss index, and s represents the deviate relevant with shadow fading degree, h _irepresent the deployment height of i-th AP.

3. the unit are load-balancing method that in wlan system according to claim 1 and 2, position-based is realized, it is characterized in that, also comprise the positional information of AP based on STA, the step of dynamic conditioning transmitting power, this step comprises:

(B1) range information of oneself distance AP and received signal strength indicator sensitivity are sent to the AP associated with it by STA;

(B2) positional information fed back according to each associated STA of AP, calculates the minimum emissive power that all STA of covering associated need;

(B3) AP arranges transmitting power according to the calculated value of power in step (B2);

(B4) transmitting power after adjustment is broadcast to STA, the STA associated therewith transmitting power according to the power adjustment of the AP received oneself by AP.

4. the unit are load-balancing method that in wlan system according to claim 3, position-based is realized, is characterized in that,

Described range information passes through formula $d={10}^{(\mathrm{TxPower}+\mathrm{AntennaGain}-\mathrm{RSSi}-{\mathrm{PL}}_{1\mathrm{Meter}}-s)/10n}$ Calculate.

5. the unit are load-balancing method that in wlan system according to claim 3, position-based is realized, is characterized in that,

Described minimum emissive power passes through formula

$P_{\min }={\mathrm{RSSI}}_{\min }+{\mathrm{PL}}_{1\mathrm{Meter}}+10\log \left(D_{\max }^n\right)+s-\mathrm{AntennaGain}$ Calculate, wherein D _maxfor the maximum in all STA and AP distances, RSSI _minthe received signal strength indicator sensitivity of the STA that maximum range value is corresponding.

6. the unit are load-balancing method that in wlan system according to claim 3, position-based is realized, is characterized in that, also comprise the step going when STA moves to associate, this step comprises:

(C1) STA detects oneself and whether occurs effective movement, when STA detects that its received signal strength indicator RSSI value is less than the received signal strength indicator sensitivity RSSI of this STA _mintime, then STA judges that existing effect is mobile;

(C2) when STA occurs effectively mobile, STA initiatively sends to the AP of association and removes disassociation frame, disconnects existing connection;

(C3) AP re-starts power adjustment according to step (B2) ~ (B4).