We conducted our most recent evaluations in early October, in a cinder-block and Sheetrock office building on the periphery of the Syracuse University campus, selected because of its geographic and radio frequency isolation. We used a spectrum analyzer to verify that the air was clear, ensuring that performance results weren't contaminated by RF interference.
We tested the Airport Extreme version 7.2.1 using a 20-MHz channel in the 2.4-GHz band (Apple doesn't support 40-MHz channels at 2.4 GHz) and a 40-MHz channel in the 5-GHz band. We used IxChariot's High Performance Throughput tests with 10-Mbyte file size. We ran multiple iterations of upstream and downstream performance tests at four locations with results averaged:
- Location 1: 15 feet from AP; no intervening walls
- Location 2: 75 feet from AP; one Sheetrock and one cinder-block wall
- Location 3: 110 feet from AP; two cinder-block walls
- Location 4: 130 feet from AP; four cinder-block walls
Results of our tests were illuminating and provide guidance to enterprise IT professionals as they begin to think about deploying 802.11n networks. The highest performance--111.2 Mbps--was turned in by an Intel Centrino client communicating with the Airport Extreme AP using 40-MHz channels at 5 GHz. This represented approximately 5.5 times the throughput of our 11a baseline. Also notable is the fact that at locations 110 feet from the access point with two intervening cinder-block walls, the 5-GHz 802.11n implementations far exceeded the performance of our baseline 802.11g test system. In fact, even at 110 feet from the AP, the Intel/Apple combination was more than twice as fast as any 802.11g product we've ever tested. And, after discussing our test results with Apple, we retested with a newer MacBook and reconfigured the AP to run in bridge mode rather than NAT mode, typical of enterprise deployments. At short range, we achieved throughput of 137 Mbps, MacBook to Airport Extreme 11n. Peak performance for Centrino increased very slightly to 112 Mbps.
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