CN108055677B - Load balancing method based on software defined wireless network - Google Patents

Load balancing method based on software defined wireless network Download PDF

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CN108055677B
CN108055677B CN201810133114.1A CN201810133114A CN108055677B CN 108055677 B CN108055677 B CN 108055677B CN 201810133114 A CN201810133114 A CN 201810133114A CN 108055677 B CN108055677 B CN 108055677B
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bandwidth
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李云
王林
曹傧
吴广富
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Chongqing University of Post and Telecommunications
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    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
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    • H04W28/08—Load balancing or load distribution

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Abstract

The invention provides a load balancing method based on a software defined wireless network, and belongs to the technical field of mobile communication. The method adopts the bandwidth utilization rate of the access points as a load index, and a network is defined by software, and a controller periodically checks the load state of each access point in the current network; the introduced load balancing factor beta judges whether the current network load is balanced; if the access points are unbalanced, a load state judgment threshold factor phi is introduced to judge different states of the access points in the system; and selecting a candidate terminal from the overload access points to transfer to the light-load access points, then selecting a proper light-load access point as a transfer receiving object of the candidate terminal by calculating the K value, and executing the transfer by the controller. The load balancing method is more general in load measurement scale, the times of transfer decision making are reduced as much as possible by using the candidate terminal, two influence factors of signal strength and residual capacity of the target access point are comprehensively considered, and the method is more practical.

Description

Load balancing method based on software defined wireless network
Technical Field
The invention belongs to the technical field of mobile communication, and particularly relates to a load balancing method based on a Software Defined Wireless Network (SDWN).
Background
In recent years, the number of mobile intelligent terminals has increased. In some special scenarios (such as meeting rooms, gymnasiums, etc.), a large number of wireless terminals attempt to connect to an Access Point (AP) with good signal quality in a short time. After the wireless hotspot appears, the following problems may occur: first, the load of a part of APs may exceed the limit, and a large amount of traffic and users compete for the resources of the AP, causing the Quality of Service (QoS) of the traffic on the AP to deteriorate, and may be in such a state for a long time. If the load level of the adjacent AP is relatively low, if no load balance adjustment is carried out, the efficiency and the performance of the wireless network can be greatly reduced; secondly, the switching of the terminals is free and blind without a network with load balancing control, along with the occurrence of hot spots, a large number of terminals newly added into the network can rush to the hot spot AP, and even part of the terminals can leave the original AP and disassociate the hot spot AP. However, the quality cannot be guaranteed as a result of switching the terminal to the hotspot AP, and when the service of the hotspot AP is saturated, a new terminal may not be accessed, or even if the terminal is accessed, the AP may be congested, and all services may be affected badly; thirdly, when the load of an AP may be saturated, a new terminal may be accessed to cause a serious result, but other unsaturated APs exist in the network and can also accept the access of the terminal to provide services for more terminals and services. If load balancing is adopted for adaptive adjustment, the tasks of load-saturated APs can be shared, the load of the APs in the whole extended service set is kept relatively stable, the tolerance in the network can be improved to a greater extent, and the method adapts to the fluctuation and change of the network; fourth, without a load balancing network, the service load in the network cannot be scheduled and arranged overall, and the AP with saturated service may occur in the network to affect the user experience, while the resource of the unsaturated AP cannot be utilized reasonably, resulting in a problem of poor network resource utilization. Therefore, based on the foregoing, a reasonable load balancing strategy becomes important. However, there are still some difficulties in implementing load balancing strategies under current wireless network architectures. Firstly, a management mechanism under a traditional architecture is lack of flexibility, and a new user association control mechanism is difficult to add on a currently deployed AP; secondly, a large amount of investment cost is needed in the aspects of configuring forwarding rules for all APs and avoiding conflicts among the rules; finally, due to lack of cooperative cooperation between APs, frequent signal interference is caused between neighboring APs. Therefore, a network architecture with centralized control capability is needed to make the network more flexible and extensible.
Software Defined Networking (SDN) has emerged as a new type of network architecture that allows network administrators to manage network services by abstracting lower-level functions, facilitating separation of the control and data layers in the network, and enabling customized programming. In the SDN architecture, OpenFlow is a standard communication interface for a centralized controller and a network forwarding device, which implements the programmable idea of SDN and allows the controller to control the behavior of a switch. OpenFlow can mask the diversity of switches from different vendors to work in conjunction with each other, providing more options for the selection infrastructure (e.g., switches, APs, etc.). By utilizing a global visual angle concentrated by the SDN, the method is beneficial to collecting load information concentrated by the extended service and is convenient for people to make a more reasonable load balancing decision. Furthermore, SDN allows a network administrator to program on the controller, so we can more easily apply the designed load balancing policy to such programmable network architecture.
Currently, researchers have devised some solutions to the wireless network load balancing problem. The documents "i.pa pikoss and m.logothtis," advanced on Dynamic Load balance for IEEE 802.11b Wireless LAN, "in proc.comcon,2001, pp.83-89" comprehensively consider RSSI and the number of Wireless terminals, and propose a minimum Load first (LLF) strategy, in which a user terminal selects an AP with the smallest number of associated terminals. In the GSM network environment, it is appropriate to select the number of terminals as the load metric because each voice call generates the same voice traffic, but in the WLAN environment, it is not reasonable to measure the load in the WLAN environment purely by the number of terminals in the cellular environment, because the traffic generated by each user terminal has large differences. The strongest Signal Strength First (SSF) method proposed in the documents "I.S. Association et al, IEEE Standard for Information Technology-Telecommunications and Information Exchange Between Systems-Local and metropolar Area Networks-Specific Requirements: Part11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications IEEE, 2001" is an AP association mechanism for 802.11, which is also widely used in load switching strategies. The 802.11k amendment also attempts to solve the load balancing problem, but needs to modify the AP and the wireless client, which causes additional hardware overhead and has a defect in feasibility. Documents "y.bejerano and s.j.han and l.li," relations and Load Balancing in Wireless LANs Using Association Control, "IEEE/access allocations on network, vol.15, No.3, pp.560-573, June 2007" propose a solution to Control maximization of the minimum fair bandwidth allocation associated with a user AP, reducing Load imbalance and consequent unfair bandwidth allocation. However, this solution requires software to be deployed on the user terminal side, and is not highly practical. Compared with the traditional wireless architecture, the software defined wireless network architecture (SDWN) can shield the difference of bottom layer equipment, and can reduce the overhead of bottom layer physical equipment without adding extra software on the terminal when a load balancing strategy is implemented.
Disclosure of Invention
Aiming at the problem of uneven load in a wireless local area network, the embodiment of the invention provides a load balancing method based on a software defined wireless network, which comprises the following steps:
s1, the controller of the SDN periodically checks the load information of each access point in the network;
s2, introducing a load balancing factor beta to represent the load state of the system at the current moment, and presetting a threshold value for the load state
Figure BDA0001575487960000031
If it is
Figure BDA0001575487960000032
The system is considered to be in an overload state at the current moment, S3 is entered, and otherwise, S1 is returned;
s3, introducing a load state judgment threshold factor phi to judge an underload access point, a balance access point and an overload access point in the system;
s4, selecting a user terminal under the overload access point as a candidate object of load transfer, transferring the user terminal to the light load access point, and selecting the user terminal as a candidate terminal;
s5, comprehensively considering the signal intensity of the light-load access point received by the candidate terminal and the residual bandwidth condition of the light-load access point, calculating the weighted value K of the signal intensity and the residual bandwidth condition of the light-load access point, and selecting the light-load access point with the maximum K value as a transfer receiving object of the candidate terminal;
s6, judging whether the transfer receiving object has the condition of receiving the candidate terminal, if yes, the controller executes the receiving and returns to S1; otherwise, return to S4.
Further, the load information includes bandwidth information of the access point, and the access point periodically records the received signal strength of the user terminal, the association state table of the user terminal, and bandwidth information required by each user terminal.
Further, the expression of the load balancing factor β is as follows:
Figure BDA0001575487960000041
wherein, Vtotal_iRepresents the total bandwidth of the ith access point; vused_iIndicating the bandwidth used by the ith access point; n denotes the total number of access points, and i is 0, 1.
Further, the method for calculating the load state decision threshold factor phi comprises the following steps:
Figure BDA0001575487960000042
wherein R isused_avgRepresents the average bandwidth usage of all access points of the system; rused_iBandwidth usage for the ith access point.
Further, a specific method for judging an underloaded access point, a balanced access point and an overloaded access point in the system by introducing a load state decision threshold factor phi comprises the following steps:
if R isused_iIf the access point is less than phi, the access point is a light load access point; if phi < Rused_iIf phi + delta phi is less than phi, the access point is a balanced access point; if R isused_iIf phi + delta phi is greater than phi, the access point is an overloaded access point; wherein, the delta phi is a preset range adjustment value.
Further, the candidate terminal selection method includes: selecting a jth user terminal UE in an m-th overloaded access pointmjAs candidate terminal, and UEmjIs closest to the value of U,
Figure BDA0001575487960000045
wherein: rused_mRepresents the bandwidth utilization, V, of the mth overloaded access pointtotal_mRepresents the total bandwidth of the mth overloaded access point, m 1,2, 3.; j ═ 1,2,3.
Further, the calculation mode of the K value is as follows:
Figure BDA0001575487960000043
and is
Figure BDA0001575487960000044
Figure BDA0001575487960000051
Figure BDA0001575487960000052
Wherein: kkThe K value of the kth light load access point; α represents a weight coefficient of the received signal strength; RSSIreceive_kIndicating the signal strength of the kth light-load access point received by the candidate terminal; RSSIneed_minRepresenting the minimum signal strength required by the candidate terminal for transferring; RSSIreceive_k_maxReceiving the maximum signal strength of the kth light-load access point for the candidate terminal; vremain_kRepresenting the bandwidth left by the kth light-load access point; vremain_k_minThe minimum value of the remaining bandwidth of the kth light-load access point; vtotal_kThe total bandwidth of the kth light load access point; k 1,2,3.
Further, the determining whether the transfer receiving object has the condition for receiving the candidate terminal specifically includes:
RSSIreceive_k＞RSSIneed_min
Vremain_k_min＞Vneed
wherein: vneedIndicating the bandwidth required for the candidate terminal to make the transition.
The beneficial technical effects of the invention are as follows: in the extended service set of the conventional wireless network, for the AP with the optimal load, the interaction of load information does not have a good solution due to the protocol privacy between devices, and then the decision for making the extended service set is difficult because each AP lacks the interaction of information. Compared with the traditional wireless architecture, the software-defined wireless network architecture can shield the difference of bottom-layer equipment, the load information of the AP in the expanded service set can be more easily acquired from a centralized global view, and the load balancing strategy of the user is deployed in the controller through customized programming, so that the centralized management and control capability is easy to make a decision smoothly. Meanwhile, the load balancing algorithm is more general in load measurement scale, the times of transfer decision making are reduced as much as possible by using the candidate terminal, two influence factors of signal strength and residual capacity of the target AP are comprehensively considered, and the re-associated AP is selected for the candidate terminal, so that the load balancing algorithm is more practical.
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FIG. 1 is a flow chart of a load balancing method based on a software defined wireless network according to the present invention;
FIG. 2 is a graph showing the variation of the bandwidth utilization of AP1 and AP2 in a simulation experiment;
FIG. 3 is a variation curve of the load balancing factor β of the system in the simulation experiment;
FIG. 4 is a graph of average throughput rate variation of user terminals under AP1 and AP2 in a simulation experiment;
fig. 5 is a comparison curve of the average throughput of the SSF policy and the LLF policy in the simulation experiment and the user terminal in the system of the method of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention are described in further detail below with reference to the accompanying drawings.
As shown in fig. 1, the specific process of the present invention is as follows:
s1, the controller of the SDN periodically checks the load information of each access point in the network;
s2, introducing a load balancing factor beta to represent the load state of the system at the current moment, and presetting a threshold value for the load state
Figure BDA0001575487960000061
If it is
Figure BDA0001575487960000062
Then it is considered asThe previous time system is in an overload state, S3 is entered, otherwise, S1 is returned;
s3, introducing a load state judgment threshold factor phi to judge an underload access point, a balance access point and an overload access point in the system;
s4, selecting a user terminal under the overload access point as a candidate object of load transfer, transferring the user terminal to the light load access point, and selecting the user terminal as a candidate terminal;
s5, comprehensively considering the signal intensity of the light-load access point received by the candidate terminal and the residual bandwidth condition of the light-load access point, calculating the weighted value K of the signal intensity and the residual bandwidth condition of the light-load access point, and selecting the light-load access point with the maximum K value as a transfer receiving object of the candidate terminal;
s6, judging whether the transfer receiving object has the receiving candidate terminal condition, if yes, the controller executes receiving and returns to S1; otherwise, return to S4.
For the calculation of the load balancing factor beta, it is assumed that there are n wireless access points AP in the current area, and the total capacity and the used bandwidth of the ith (i is more than or equal to 1 and less than or equal to n, i belongs to Z) AP are respectively Vtotal_iAnd Vused_iThen APiThe ratio of the bandwidth used to the total capacity is
Figure BDA0001575487960000071
Average bandwidth usage in the system is
Figure BDA0001575487960000072
Then, a load balancing factor β is introduced to characterize the load state difference of the current system, which is essentially a standard deviation formula as follows:
Figure BDA0001575487960000073
the smaller beta is, the closer the ratio of the bandwidth resources used among the APs of the system is, the more balanced the load state of the system is; on the contrary, the more uneven the load state of the system at this time. Therefore, the threshold value may be set in advance
Figure BDA0001575487960000075
When in use
Figure BDA0001575487960000076
At this time, the system may be considered to be in a load balancing state at the current time. Ideally, when β is equal to 0, the system is in perfect load balancing.
In order to determine the current load status (light load, balanced load and overload) of each AP, the load of each AP is compared with the average load of the system, i.e. a load status decision threshold factor Φ is introduced, which is expressed as follows:
Figure BDA0001575487960000074
if APiIs less than phi (i.e. R)used_i< phi), where such AP is defined as a light-load AP, which can accommodate more traffic;
APiis greater than phi, i.e. Rused_iPhi is larger than phi. Such APs are subdivided here into two categories: if APiIs located between (phi, phi + delta phi), i.e. phi < Rused_iIf phi + delta phi is less than phi, the class of AP is a balanced AP; if APiIs greater than phi + delta phi, i.e. Rused_iIf phi + delta phi is greater, the AP is an overloaded AP.
To balance the network load, the overloaded AP will hand over some of the terminals associated with it to the underloaded AP.
Through a centralized view of the SDN, whether the system load is unbalanced or not can be detected by using load measurement standards, and if the system load is unbalanced, a load balancing algorithm of an application layer located above the controller is called.
Then, in the selection of the switching object, the load balancing strategy designed by the invention aims to consider how to transfer part of the user terminals under the overloaded AP to the underloaded AP.
First, how to select a part of terminals under an overloaded AP as a load transfer target is considered. The simplest and most straightforward way is to randomly select a part of the terminals for load shifting. However, this approach may result in a large number of diversion decisions before the system is load balanced. Based on this hidden danger, this document takes a method of finding candidate terminals in order to reduce the number of terminals transferred as much as possible.
Suppose to be connected with the m-th overloaded access point AP'mAssociated jth user terminal UEmjUsing a bandwidth of Vused_mjThen, then
Figure BDA0001575487960000081
AP'mThe ratio of the bandwidth used by the jth user terminal to the total capacity
Figure BDA0001575487960000082
The user terminal UE with throughput rate closest to the difference U between the overload AP load and the average system load is selectedmjSuch a terminal is referred to as a candidate terminal as a candidate for the transition. U ═ Rused_m-Rused_avg)×Vtotal_m。
Second, consider how to select a suitable lightly loaded access point for the candidate terminal for the transfer. Here, the invention considers the candidate terminal from the kth lightly loaded access point
Figure BDA0001575487960000083
Received signal strength RSSI ofreceive_kAnd
Figure BDA0001575487960000084
is of residual bandwidth Vremain_kAnd calculating to obtain a weighted value K of the two, wherein the light load access point with the maximum K value is selected as a transfer receiving object of the candidate terminal.
The K value is calculated as follows:
Figure BDA0001575487960000085
Figure BDA0001575487960000086
and is
Figure BDA0001575487960000087
Figure BDA0001575487960000088
Figure BDA0001575487960000089
RSSIreceive_k＞RSSIneed_min (6)
Vremain_k_min＞Vneed (7)
Wherein: kkThe K value of the kth light load access point; α represents a weight coefficient of the received signal strength; RSSIreceive_kIndicating the signal strength of the kth light-load access point received by the candidate terminal; RSSIneed_minThe minimum signal strength required by the candidate terminal for transferring is represented, and once the minimum signal strength is lower than the value, the condition for switching the candidate terminal is not met; RSSIreceive_k_maxReceiving the maximum signal strength of the kth light-load access point for the candidate terminal; vremain_kRepresenting the bandwidth left by the kth light-load access point; vremain_k_minMinimum of bandwidth left for the kth light-load access point, once below this value
Figure BDA0001575487960000091
The load status may change (i.e., become a balanced AP or an overloaded AP); vtotal_kThe total bandwidth of the kth light load access point; k 1,2,3. VneedIndicating the bandwidth required for the candidate terminal to make the transition. The formula (6) is to satisfy the signal strength switching threshold to be reached by the terminal switching; equation (7) aims to guarantee the handover sought for the candidate terminal
Figure BDA0001575487960000092
The remaining capacity of (a) can meet the bandwidth requirement of the terminal.
In order to further verify the reliability of the load balancing strategy provided by the patent, a simulation experiment is carried out on a Mininet platform. 2 APs and 4 user terminals are deployed in a Mininet environment, the APs are expanded through Python scripts, and 3 attributes of signal strength, available bandwidth and coverage are added to the APs. The coverage radius of each AP is 20 meters, the maximum throughput rate of each AP is 80Mbps, and the signal strength and the transmission rate are reduced along with the increase of the distance from the terminal to the AP.
First, a fixed threshold is set for the system load difference
Figure BDA0001575487960000093
When the system load difference is higher than the threshold value
Figure BDA0001575487960000094
The load balancing algorithm will be triggered, here
Figure BDA0001575487960000095
Set to 0.025. Then, we set the boundary Δ Φ between the balanced AP and the overloaded AP to 10%, that is, an AP whose load exceeds the average system load by more than 10% is the overloaded AP, and an AP whose load exceeds the average system load by less than 10% is the balanced AP. The overloaded AP is no longer associated with other terminals and some of the terminals below it should roam to the underloaded AP.
For the scenario of the simulation experiment, two APs are deployed in the area where the coverage areas overlap. Initially, only one of the ues is associated with AP1, and the remaining 3 ues are associated with AP2, in order to create an AP load imbalance environment. The duration of the simulation is 300s, an average value is collected every 10s, the system preheating time is 100s, namely no load balancing strategy is adopted, and a load balancing algorithm deployed in the controller starts to operate after 100 s.
In fig. 2, the ratio of bandwidth usage is used as an index for measuring the AP load, and a larger value indicates a larger traffic load of the AP in the current extended service set. In fig. 2, it is shown that the load of AP2 is approximately twice that of AP1 for 100s before the load balancing policy is triggered. Then, for the remaining 200s, part of the terminals associated with AP2 gradually roam to AP1 because of the implementation of the load balancing policy, causing the loads of AP1 and AP2 to gradually approach equality.
FIG. 3 is a variation curve of the load balance factor β of the system in the simulation experiment, where the first 100s network load is in a severe imbalance state, so the value of β is large; however, under the coordination of the load balancing mechanism, the beta value is continuously reduced and is lower than the threshold
Figure BDA0001575487960000101
And then tends to be stable.
Fig. 4 shows the average throughput rates of user terminals associated with AP1 and AP2 in the extended service set. In the beginning, the average throughput of the AP1 is about 33Mbps, while the average throughput of the AP2 is only about 12 Mbps. At 100s, along with the implementation of the load balancing strategy, the association state of the terminal and the AP is changed and gradually becomes stable, and the average throughput rate of the terminal associated with the AP2 is improved by about 10 Mbps. Although the average throughput of the terminals associated with AP1 in the extended service set drops to around 20Mbps, the throughput is greatly improved for the entire system.
Fig. 5 shows a comparison between the method proposed in this patent and the average throughput of the terminal under the system using the strongest Signal Strength First (SSF) strategy and the minimum load first (LLF) strategy, where LLF is the traditional most direct load balancing strategy, and the user terminal selects the AP with the smallest number of associated terminals. The strongest signal strength and best SSF method is an 802.11 AP association mechanism, which is also widely used in load handover strategies. Fig. 5 shows that the method, SSF policy, and LLF policy provided in this patent all have good effects in balancing network load and improving system throughput. More preferably, even though SSF is improved by about 12% over LLF in terms of throughput, the strategy proposed by this patent is improved by about 21% over SSF.
Those skilled in the art will appreciate that all or part of the steps in the methods of the above embodiments may be implemented by associated hardware instructed by a program, which may be stored in a computer-readable storage medium, and the storage medium may include: ROM, RAM, magnetic or optical disks, and the like.
The above-mentioned embodiments, which further illustrate the objects, technical solutions and advantages of the present invention, should be understood that the above-mentioned embodiments are only preferred embodiments of the present invention, and should not be construed as limiting the present invention, and any modifications, equivalents, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (6)

1. A load balancing method based on a software defined wireless network is characterized by comprising the following steps:
s1, the controller of the SDN periodically checks the load information of each access point in the network;
s2, introducing a load balancing factor beta to represent the load state of the system at the current moment, and presetting a threshold value for the load state
Figure FDA0003101514050000011
If it is
Figure FDA0003101514050000012
The system is considered to be in an overload state at the current moment, S3 is entered, and otherwise, S1 is returned;
s3, introducing a load state judgment threshold factor phi to judge an underload access point, a balance access point and an overload access point in the system;
s4, selecting a user terminal under the overload access point as a candidate object of load transfer, transferring the user terminal to the light load access point, and selecting the user terminal as a candidate terminal;
s5, comprehensively considering the signal intensity of the light-load access point received by the candidate terminal and the residual bandwidth condition of the light-load access point, calculating the weighted value K of the signal intensity and the residual bandwidth condition of the light-load access point, and selecting the light-load access point with the maximum K value as a transfer receiving object of the candidate terminal;
s6, judging whether the transfer receiving object has the condition of receiving the candidate terminal, if yes, the controller executes the transfer and returns to S1; otherwise, return to S4;
the specific method for judging the underloaded access point, the balanced access point and the overloaded access point in the system by introducing the load state judgment threshold factor phi comprises the following steps:
if R isused_iIf the access point is less than phi, the access point is a light load access point; if phi < Rused_iIf phi + delta phi is less than phi, the access point is a balanced access point; if R isused_iIf phi + delta phi is greater than phi, the access point is an overloaded access point; wherein, delta phi is a preset range adjustment value, Rused_iBandwidth usage for the ith access point;
the K value is calculated as follows:
Figure FDA0003101514050000013
Figure FDA0003101514050000014
and is
Figure FDA0003101514050000015
Figure FDA0003101514050000021
Figure FDA0003101514050000022
Wherein: kkThe K value of the kth light load access point; α represents a weight coefficient of the received signal strength; RSSIreceive_kIndicating the signal strength of the kth light-load access point received by the candidate terminal; RSSIneed_minRepresenting the minimum signal strength required by the candidate terminal for transferring; RSSIreceive_k_maxReceiving the maximum signal strength of the kth light-load access point for the candidate terminal; vremain_kRepresenting the bandwidth left by the kth light-load access point; vremain_k_minThe minimum value of the remaining bandwidth of the kth light-load access point; vtotal_kThe total bandwidth of the kth light load access point; k 1,2,3.
2. The method of claim 1, wherein the load balancing method based on the software defined wireless network comprises: the load information comprises bandwidth information of the access point, and the access point periodically records the received signal strength of the user terminal, the user terminal association state table and the bandwidth information required by each user terminal.
3. The method of claim 1, wherein the load balancing method based on the software defined wireless network comprises: the expression of the load balancing factor β is as follows:
Figure FDA0003101514050000023
wherein, Vtotal_iRepresents the total bandwidth of the ith access point; vused_iIndicating the bandwidth used by the ith access point; n denotes the total number of access points, and i ═ 1, 2.
4. The method of claim 3, wherein the load balancing method comprises: the method for calculating the load state judgment threshold factor phi comprises the following steps:
Figure FDA0003101514050000024
wherein R isused_avgRepresents the average bandwidth usage of all access points of the system; rused_iBandwidth usage for the ith access point.
5. The method for load balancing based on the software-defined wireless network as claimed in claim 4, wherein the candidate terminal selecting method comprises:
selecting a jth user terminal UE in an m-th overloaded access pointmjAs a waiting timeSelect a terminal, and UEmjIs closest to the value of U ═ Rused_m-Rused_avg)×Vtotal_m；
Wherein: rused_mRepresents the bandwidth utilization, V, of the mth overloaded access pointtotal_mRepresents the total bandwidth of the mth overloaded access point, m 1,2, 3.; j ═ 1,2,3.
6. The method of claim 1, wherein the load balancing method based on the software defined wireless network comprises: judging whether the transfer receiving object has the condition of receiving the candidate terminal specifically comprises the following steps:
RSSIreceive_k＞RSSIneed_min
Vremain_k_min＞Vneed
wherein: vneedIndicating the bandwidth required for the candidate terminal to make the transition.
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