Mar

Dwell on the wireless LAN load balancing of various factors

As the name suggests, wireless local area network load balancing, load balancing is based on the wireless LAN network structure above, to improve the performance of the network. Those that specifically improve performance? Is through what principles to enhance its effects? Through this article, you will understand.

We all know that, due to the randomness of the external network of task arrival, as well as processing nodes processing differences, when the distributed system running for some time, some nodes are still many assigned tasks (called overburden) , while others are idle nodes (called light-load). On the one hand, so that overloaded nodes to complete the task as quickly as possible is a priority; on the other hand, some nodes at light loads is a waste. How to avoid this busy and idle coexist happen in order to effectively improve the system resource utilization, reducing the average response time for the task. This is a load-balancing issues to be addressed.

simple, the load balancing problem is the task of optimizing combinatorial problems. Wired distributed system load balancing method is the object of the task. The basic approach is to collect the load information to the relevant decision-making algorithm for the tasks assigned to each node to re-schedule tasks, such as process migration, or migration.

Wireless LAN load balancing to face more difficulties than the wired network. As wireless LAN extension services focused on the mobile terminals and the time-varying wireless channel, each access point (AP) load on the discrepancy. The role of load balancing is to balance the various differences in AP in order to maximize network resource utilization. In fact, the load balancing is the focus of radio resource management, IEEE 802.11 Working Group TGv Task Force, specializing in wireless local area network load balancing to resolve the issue.

Our main to explore the load balancing of wireless LAN.

wireless and wired LAN load balancing load balancing in distributed systems is different from the performance of the control objects in the load balancing and control means. As wireless terminal mobility and wireless channel time-varying, wireless LAN, load balancing to face the situation more complicated. Wireless local area network (WLAN) is the application of wireless communication technology to computer equipment connected together to form that can communicate with each other and achieve resource sharing network.

In the wireless LAN, there are two roles: AP and terminal (STA). AP as a fixed infrastructure, through the wired distributed system interconnect. STA as a mobile terminal to receive access to services provided by AP.

the form of an unbalanced load: Wireless AP the number of terminals connected to the uneven

Terminal by scanning the channel, access to WLAN environment in which to expand their services and basic service set of information collection , and choose to join an appropriate set of basic services. Wireless LAN is by a number of AP load balancing for multiple mobile terminals access the system, each AP site through the use of Internet information management, and aims to make full use of the network of existing resources and reducing network congestion.

in the center of the AP, after a period of operation, the number of terminals connected to the terminal than the number of AP around the bear's business has also been saturated and the connection to the center of the terminal AP Business Quality of Service (QoS) can no longer be guaranteed. To the periphery of the AP business is not saturated, the network appears in the load differences. Load balancing is to resolve this difference, the AP some of the operations center moved to the AP on the periphery in order to improve network service capacity and quality of service center of AP.

load imbalance Type 2: Terminal constantly switch the load caused by jitter

WLAN There are two forms of work organization, Independent Basic Service Set (IBSS) and basic service set (BSS ).

terminal (for example, wireless network with a notebook computer) when entering the network must select an AP as a connection object, which is the process of terminal access, access to go through the process of scanning, authentication, connection and other steps. In general, the terminal will be scanned during the scanning process to multiple AP's information, select the terminal to the AP on condition that scans the AP's signal strength. As the wireless LAN terminals, mobile features and time-varying characteristics of wireless channel, the terminal will occur in some cases, to switch from one BSS to another BSS situation. This is the wireless LAN switch. The problem is caused by the terminal to switch handoff delay, and even the upper disruption to business.

switch will also bring the issue is ping-pong effect. Namely, the terminal around the clock to switch between two or more AP, the terminal just as the same as table tennis. This will result in the load jitter on the network resources, causing great losses.

classification of wireless local area network load balancing

can be two aspects of wireless local area network load balancing technology categories. In accordance with the initiator of load balancing points, load balancing can be divided into STA-dominated load balancing and AP-dominated load balancing. In accordance with the load-balanced solution can be divided into Plug-in load balancing and switching load balancing.

terminal (STA) host load-balancing

STA-dominated load-balancing is actually a self-load balancing strategy is the characteristics of the wireless LAN, one of STA. Switching completed STA actually achieved a network load transfer. Simply by switching the signal quality as the STA condition is one-sided, there are a large number of studies focus on how to improve the time to switch to more accurate realization of the load brought about changes in the terminal switch.

STA-dominated advantages: STA of the most aware of their business needs and their environment, STA scans the environment to be available in BSS situation on the STA in terms of the most accurate. Moreover, the switch or access is the mainstay of STA, the STA operation is carried out on, switch losses borne by the STA. The disadvantage is that: STA just know that the terminal side of the situation and the STA's own situation, the network environment is concerned, STA is not very accurate, and no voice. STA switching arbitrary large, will cause confusion throughout the ESS, so that the network load balancing effect of the global poor.

AP host load-balancing

AP host load balancing, the starting point is, AP is the network side, AP wired connections between, you can not affect the operation of STA Under the mutual transmission and load-balancing-related information. Based on these information, ESS can tell AP the AP load and load the heaviest lightest AP. ESS has the information you can make some decisions, for example, so that the load under the weight of the AP terminal to switch to the AP, under light loads, or join the network terminals of the new restrictions do not allow access to the load weight of AP only Allow access to AP and other light load to achieve load balancing within the ESS.

AP has the advantage of controlling the overall situation of the network side can be distributed between the AP system, accurate and timely statistics, in the overall coordination and scheduling aspects of the network side benefit, but also relatively easy to achieve the overall strategy implementation. The other is the load balancing across the network to adjust the speed quickly. The disadvantage is that the network side does not know the location of STA and the network environment, STA which can scan the case to the AP, so there is the risk of making a wrong decision to switch.