doc.: IEEE /0757r0 Submission July 2005 C Trecker, Azimuth SystemsSlide 1 Test Methodology for measuring Fast BSS Transition Performance Notice: This document has been prepared to assist IEEE It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE Working Group. If you have questions, contact the IEEE Patent Committee Administrator at. Date: Authors:

doc.: IEEE /0757r0 Submission July 2005 C Trecker, Azimuth SystemsSlide 2 Abstract This presentation proposes test metrics and test methodologies to characterize fast BSS transition performance.

doc.: IEEE /0757r0 Submission July 2005 C Trecker, Azimuth SystemsSlide 3 Outline Definitions and Metrics Methodology Topology Procedure Results

doc.: IEEE /0757r0 Submission July 2005 C Trecker, Azimuth SystemsSlide 4 Definitions and Metrics Fast BSS Handshake Time: Time between FBT Auth Request and FBT (Re) Assoc Response (Base Mechanism). When pre- reservation is used, time between FBT (Re) Association Request and FBT (Re) Association Response. –This time can be precisely measured. Fast BSS Transition Time. Time between MSDU delivery to DS from AP1 and AP2 as a STA executes a FBT transition from AP1 to AP2. Should also measure the time downstream DS – STA MSDU time. –This time is measured both on the DS (FBT Time DS) and on the air (FBT Time Air) –This time can not be precisely measured unless using WIFI test equipment configured to act as a STA in a controlled environment. –This time will generally be measured statistically over several transitions at different data rates.

doc.: IEEE /0757r0 Submission July 2005 C Trecker, Azimuth SystemsSlide 5 Fast BSS Handshake Time Observed BSS Transition Time FBT Handshake Time Auth ReqAuth RespAssoc ReqAssoc Resp packets observed on the air

doc.: IEEE /0757r0 Submission July 2005 C Trecker, Azimuth SystemsSlide 6 Fast BSS Transition Time MSDU-AP1ACK Last possible instant where frames can pass through old AP MSDU-AP2ACK First possible instant where frames can pass through new AP Theoretical BSS Transition Time... Observed FBT Time on air packets observed on the air MSDU-AP1MSDU-AP2... packets observed on the DS Observed FBT Time on DS

doc.: IEEE /0757r0 Submission July 2005 C Trecker, Azimuth SystemsSlide 7 Methodology Force a Fast BSS Transition –Base Mechanism –Pre-reservation Measure Fast BSS Handshake Measure Fast BSS Transition on DS and over the air Iterate to allow for statistical aberrations Use different data rates. This allows for apples-to-apples comparisons in FBT performance

doc.: IEEE /0757r0 Submission July 2005 C Trecker, Azimuth SystemsSlide 8 Different ways to cause a fast-BSS Transition STA or AP initiated for reasons other than a degrading RF signal Rolling cart Power off AP “Cone of Silence” RF Attenuators –Open Air –Controlled Environment

doc.: IEEE /0757r0 Submission July 2005 C Trecker, Azimuth SystemsSlide 9 Use cases require controlled environment Both APs always on Must control amount of BSS overlap Figure 1 implies client moves between BSSs smoothly Methodology must be flexible for additional use cases

doc.: IEEE /0757r0 Submission July 2005 C Trecker, Azimuth SystemsSlide 10 Controlled Environment Topology Combiner Wireless Sniffer Combiner Wireless Sniffer Ethernet Hub Ethernet Sniffer Traffic Source / Sink

doc.: IEEE /0757r0 Submission July 2005 C Trecker, Azimuth SystemsSlide 11 Device Topology 2 APs, 1 Client, 1 Server 2 Wireless Protocol Analyzers – Positioned between each AP and Client 1 Ethernet Sniffer (assumes DS is ethernet) Packets Captured on: –Both AP Channels –Wired Ethernet on Server Traffic generated between Client and Server

doc.: IEEE /0757r0 Submission July 2005 C Trecker, Azimuth SystemsSlide 12 Controlling Path Loss Each station is cabled into a shielded chamber –Greater than 120 dB isolation required between station and AP to guarantee loss of association Path loss between stations is controlled programmatically with step attenuators –Dynamic range of 80dB is sufficient

doc.: IEEE /0757r0 Submission July 2005 C Trecker, Azimuth SystemsSlide 13 Packet Capture On Wired DS: –Last Data Packet before Roam from AP1 –First Data Packet after Roam from AP2 On Wireless Protocol Analyzers –Above packets, plus: – Management frames to measure FBT handshake.

doc.: IEEE /0757r0 Submission July 2005 C Trecker, Azimuth SystemsSlide 14 Client Association: First data packet after roam Stimulating a Transition t PRE-RES t RETRY Last data packet before roam t FT t ROAM t DATA AP1AP2 max min Atten AP1 AP2 Attenuator Sweep Time Inter-Roam Delay

doc.: IEEE /0757r0 Submission July 2005 C Trecker, Azimuth SystemsSlide 15 Test Results, Total Roam Time

doc.: IEEE /0757r0 Submission July 2005 C Trecker, Azimuth SystemsSlide 16 Conclusion Fast BSS Transition Performance metrics will allow for valid comparisons between different implementation algorithms and vendor solutions Repeatability and flexibility of controlled environment is very beneficial Valid system FBT performance measurement will depend on statistical analysis