support for load balancing in v

Submission Kwak, Rudolf1

Support for Load Balancingin 802.11v

Joe Kwak, Marian Rudolf (InterDigital)

doc: IEEE 802.11-05/xxx5r0May 2005



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



Introduction What do we mean by load balancing?

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



Load balancing illustration

Non-uniform load

Load



Load balancing illustrationCongestion

SpareCapacity

Non-uniform load

Load



Load balancing illustrationNo more congestion

More uniform and predictable service

Load



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



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



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

Possible Load Balancing approach for 802.11v (2/2)

support for load balancing in v

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