Roaming Interval Measurements March 2004 doc.: IEEE 802.11-04/0378 March 2004 Roaming Interval Measurements Areg Alimian Communication Machinery Corporation aalimian@cmc.com Areg Alimian, CMC Areg Alimian, CMC

Goals of this presentation March 2004 Goals of this presentation Present roaming interval measurements for a given test case. Present test configurations for roaming measurements. Areg Alimian, CMC

Different Test Scenarios for Evaluating Handoff Performance March 2004 Different Test Scenarios for Evaluating Handoff Performance Handoff Triggering Mechanisms The power to the current AP is switched off Decreasing the Tx power of current AP Changing the load on the current AP Injecting Traffic Patterns during handoff Unidirectional upstream traffic from STA to a host on the LAN Unidirectional downstream traffic from LAN host to STA. Bidirectional traffic between STA and LAN host. 2nd STA at the new AP competing for media access. Areg Alimian, CMC

Experimental Roaming Test Scenario March 2004 Experimental Roaming Test Scenario Mobile STA performs roaming between two APs attached to the same LAN via Eth. Sw. Mobile STA is communicating with a host on the wired LAN. Traffic sent between the STA and the host emulates voice data. UDP packets are generated with 172 bytes of payload every 20 ms, carried inside IPv4. Emulates 64 kbit/s pulse code modulated (PCM) voice stream. Areg Alimian, CMC

Handoff Test Procedure Example March 2004 Handoff Test Procedure Example Configure AP1 to Ch1, AP2 to Ch2, with the same SSID. Install and configure NTP Time synchronization clients on both sniffer and Mobile Unit PCs to be synchronized to the NTP server with +/-5ms. Set sniffers to monitor each AP channel. Cause the Mobile STA to associate with the desired initial AP(1) Configure the load generator for the Mobile Unit to generate equivalent of streaming voice traffic. Disconnect (power off) currently associated AP. Examine sniffer traces to determine rate adaptation, authentication and overall handoff latency. Areg Alimian, CMC

Handoff Test Metrics Summary March 2004 Handoff Test Metrics Summary Rate adaptation Rate adaptation time Packet loss during rate adaptation (Re)authentication (Re)authentication (AKM) without prior security Association states. (Re)authentication (AKM) without prior security State. (Re)authentication with IAPP. Roaming Handoff Interval Downstream loss during handover Session continuity during handover Upstream delay Scanning Passive Scanning Active Scanning Behavioral Roaming hysteresis Rate adaptation hysteresis Network Connectivity resumption Valid IP address acquisition/ IP configuration Transport adaptation Areg Alimian, CMC

Example Test setup AP 1 AP 2 MU Sniffer 1 Sniffer 2 Channel 11 March 2004 Example Test setup AP 1 AP 2 Channel 11 Channel 6 MU Sniffer 1 Sniffer 2 Areg Alimian, CMC

Handoff Interval Measurements March 2004 Handoff Interval Measurements Rate Adapt. Detection Scanning Handoff Test 1 30ms 26.9s 100ms 27s Test 2 20ms 3.1s 8.6s 11.7s Test 3 50ms 590ms 253ms 843ms Test 4 120ms 1.6s 4.7s Note: 4 different STAs and 4 different APs used making the above measurements Areg Alimian, CMC

March 2004 Future Work Comprehensive studies utilizing the test methodologies and metrics outlined earlier in this presentation on IEEE 802.11i implementations would be very useful. Areg Alimian, CMC

March 2004 Feedback? Areg Alimian, CMC