5. The Tests - Single STA Throughput

To shake things down and get the hang of using the EE, I started out nice and simple, using the EE to generate one virtual STA (vSTA) to check the maximum throughput of each AP with my test setup.

The results shown in Figures 9 and 10 represent the average throughput from a 5 minute IxChariot run using the throughput script with the default 1,000,000 Byte file size per timing record.

Figure 9: STA to AP throughput - One STA - 5min.

Figure 10: AP to STA throughput - One STA - 5 min.

I started out letting the Emulation Engine use its automatic rate algorithm, but noticed lower performance than expected during my initial testing. After consulting with a CMC applications engineer, I decided to force the EE's rate to 54Mbps. This definitely improved the measured throughput for the products using the Broadcom chipset, but degraded the STA to AP speed for the 3Com and SMC Atheros-based APs.

By looking at the statistics accumulated by the Emulation Engine, I was able to see that the main contributor to the lower forced-rate speed was that vSTA transmit errors increased by about 8X when the rate was forced for the 3Com and SMC twins. I also found that the uplink speed of the Gigabyte AP was the same whether the EE rate was forced or left to autorange. I attribute this to the fact that the Gigabyte AP uses the same Atheros AR2112 radio, but the newer AR5213 MAC/baseband processor instead of the AR5212 MAC/baseband used by the 3Com / SMC AP.

So the results in Figure 9 reflect letting the EE auto-range its transmit rate for the 3Com and SMC AP runs, while being forced to 54Mbps for all the other products. All the test runs shown in Figure 10 have the EE rate forced to 54Mbps.