Support for Load Balancing in 802.11v January 2003 IEEE 802.11-03/100r1 May 2005 doc: IEEE 802.11-05/xxx5r0 Support for Load Balancing in 802.11v Joe Kwak, Marian Rudolf (InterDigital) Submission Kwak, Rudolf

Agenda Introduction Load balancing illustration 802.11 today STA-centric 802.11v opportunities Decision taken by network AP-centric with support from STA Hybrid scheme Split of load balancing responsibilities between AP and STA Kwak, Rudolf Submission

Introduction What do we mean by load balancing? Why is this needed? Handover of one or multiple STA from one AP to another AP Triggered by load considerations; not by mobility Why is this needed? Indoor or dense deployments tend to be characterized by geographically non-uniformly distributed traffic This can translate into having a congested BSS while other neighbor BSS’s have spare capacity Sub-optimal use of system resources (e.g. achieved system throughput much lower than it actually could be) Sub-optimal throughput and/or QoS experienced by users Kwak, Rudolf Submission

Load balancing illustration Non-uniform load Kwak, Rudolf Submission

Load balancing illustration Spare Capacity Congestion Load Non-uniform load Kwak, Rudolf Submission

Load balancing illustration No more congestion More uniform and predictable service Load Kwak, Rudolf Submission

802.11 today (STA-centric) Each STA has its own criteria to determine its handover triggers Many or most STA do not try to select BSS based on network load balancing considerations Pros STAs are in a good position to evaluate the different candidates RF-wise and decide at which instant they should handover Cons STAs do not have a view of the whole system, particularly not network-wide traffic distribution Unless all STAs come from the same vendor and are configured the same, load balancing is not performed in a cohesive fashion today Kwak, Rudolf Submission

Possible Load Balancing approach for 802.11v (1/2) Decision could be taken by the network (AP-centric approach) Pros APs (or network) have broader view of system and are in better position to perform actions that will optimize system performance For a network operator, it is easier to implement a given load balancing policy through the APs (O&M) than through the STAs APs can capitalize on robustness and bandwidth of Distribution System for facilitating handover Signalling for Handover execution is (almost) in place, 802.11r Cons Proper timing of the handover and load balancing performance trade-offs could require the AP to monitor the quality perceived by STA Outline for one possible way for TGv to support load balancing Signaling for AP to initiate STA handover to another AP in the ESS Signaling for AP to suggest a STA to handover to an AP in the ESS STA supporting AP by sending candidate AP lists Rely on TGr for handover execution by STA Kwak, Rudolf Submission

Possible Load Balancing approach for 802.11v (2/2) Or, load balancing responsibilities shared between STA and AP (as alternative to AP-centric, some sort of hybrid approach) AP’s (or network) responsible for determining the load balancing policy in the BSS that will optimize system-wide throughput Broadcast in the BSS or sent to STAs during (re-)association STA is responsible for implementing/executing the load balancing policy Monitoring of load-balancing motivated handover conditions and actual handover execution (as by 11r for example) One possible approach for the AP Serving AP sends the BSS load balancing policy to STA Triggers, for example metric X BSS1 - metric X BSS2 > Margin for 10 sec In addition, serving AP supporting STA by – for example - Sending neighboring AP lists accompanied by observed load metrics and timing of beacons (11k) APs supporting STA by sending advertisement packets on channels other than their own to allow STA to scan without changing channels Kwak, Rudolf Submission