1. Roaming Interval Measurements
March 2004
doc.: IEEE /0378
March 2004
Roaming Interval Measurements
Areg Alimian
Communication Machinery Corporation
Areg Alimian, CMC
Areg Alimian, CMC

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

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

10. March 2004
Feedback?
Areg Alimian, CMC