1. Bss Load Balancing Requirements
Month Year
Jul 2005
July 2005
Bss Load Balancing Requirements
Date:
Authors:
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Bin Wang, ZTE Corporation
Bin Wang, ZTE Corporation

2. Month Year
Jul 2005
July 2005
Abstract
This document suggests AP load balancing requirements for Wireless Network Managements. Review the advantages and disadvantages of current, and gives some possible approaches.
Bin Wang, ZTE Corporation
Bin Wang, ZTE Corporation

3. Agenda Introduction Load balancing illustration 802.11 Current
Month Year
Jul 2005
July 2005
Agenda
Introduction
Load balancing illustration
Current
Possible Approaches
Bin Wang, ZTE Corporation
Bin Wang, ZTE Corporation

4. Introduction The meaning of load balancing:
Month Year
Jul 2005
July 2005
Introduction
The meaning of load balancing:
The traffic in ESS maintain even distribution during it’s life, varies smoothly.
It is reasonable to satisfy high QoS requirement Applications that some STAs with low-level QoS requirements will be handed over to another AP, release their resources for the high QoS application.
The necessity of load balancing:
The utilization of the ESS’s resources will be more evenly and effectively, could decrease drastic wave and boosting of traffic.
The characteristics of ESS: BSSs live in harmony with each other to form a ESS, and work together to supply services for STAs in the ESS.
To guarantee the continuity of the Application which has QoS requirements.
To prevent the happening of AP’s congestion and choke.
Bin Wang, ZTE Corporation
Bin Wang, ZTE Corporation

5. Unbalanced Wireless Network
July 2005
Unbalanced Wireless Network
Bin Wang, ZTE Corporation

6. July 2005
AP Load Balancing
Bin Wang, ZTE Corporation

7. Month Year
Jul 2005
July 2005
Current
The APs in ESS manage their own load status respectively and independently, and the distribution of load burden among APs just according to RSSI.
STA based hand over: After STA decide to handover, it break it’s current connection and then subscribe JOIN request to it’s favorite target;
As current hand over is a new process of authentication and JOIN, it is in all probability to happen that STA frequently checking out from a AP and checking in back to the same one, which degrades the performance of ESS tremendously.
Handover caused by load balancing is a “two-edged sword”. It could release the burden of AP or break the application of STA. So the action must be controlled and restricted.
Advantages:
STA knows exactly the occasion of hand over.
STA knows exactly the strength of signals in around.
Disadvantages:
No communication and correspond among BSSs.
The information STA can acquire is insufficient to make correct decision.
Huge differences between STAs from different venders.
Uncontrolled handover.
Heavy bss will retain their chaos, while the lighter couldn’t be a partaker.
Bin Wang, ZTE Corporation
Bin Wang, ZTE Corporation

8. 80211v Possible Approach(1/3)
July 2005
80211v Possible Approach(1/3)
There should be a center point in ESS. An AP may perform this role, who responsible for communicating and corresponding load balancing information within the ESS, managing and controlling the global load balancing policy.
The center point should not be fixed on one AP, because the extra burden will be imported to the BSS who acting as the center point. All the APs in ESS have chance to take this role.
Need the support of Neighbor Report Element(TGk).
Advantage:
ESS has the inherent privilege to gather global load balancing information.
Could across-the-board dispatch the resources in ESS more effectively.
The lightest burden BSS make the greatest contribution in Load balancing hand over progress. The heaviest burden BSS will be release after hand over.
Disadvantage:
Networking overhead will be increased to some extent.
Bin Wang, ZTE Corporation

9. 80211v Possible Approach(2/3)
July 2005
80211v Possible Approach(2/3)
Adding mechanism to implement frequent handover detection and frequent handover avoidance.
Restrain the fluctuation of application’s performance.
Improve the efficiency of handover caused by load balancing；
Could be implement on the STA side；
Bin Wang, ZTE Corporation

10. 80211v Possible Approach(3/3)
July 2005
80211v Possible Approach(3/3)
AP-STA cooperative load balancing: AP holds the dominant position, where STA acts an assistant role. This can combining the information from network and the executor of handover: client.
Maybe: A list of one or more APs that could be heard by STA will be recommended to the network, AP perform the judgment and succedent actions.
Advantage:
Could make use of both the network condition and the client status.
Could make the decision more accurate.
Could make the command or recommend generated by load balancing policy more meaningful and significative.
Diminish the “bad” handover or “regret” handover.
Bin Wang, ZTE Corporation

11. July 2005
Feedback?
Bin Wang, ZTE Corporation