Performance Testing - Background
Since the GPHD is, at its core, a HomePlug AV adapter, I figured it was fair game to include a comparison to an HPAV product in the performance tests. It so happened that NETGEAR asked me whether I was interested in looking at their new XAVB1004 Home Theater Internet Connection Kit shortly after I received Belkin's review request.
Figure 4: NETGEAR XAV1004
The kit includes an XAV1004 HomePlug AV adapter with a built-in four-port 10/100 switch and an XAV101 HomePlug AV adapter with a single 10/100 port.
For the tests, I took a similar approach to that used in the last HomePlug AV review, the Zyxel PLA-400. I set up one adapter in my office, connected to my LAN's Gigabit switch. I then moved a second adapter to five outlets located in my wireless test locations. For Location A, I plugged both adapters into the same wall outlet in my office.
I used IxChariot to run the throughput.scr script, with the test file size changed to 1,000,000 Bytes and using TCP/IP. I ran separate Transmit (data sent from the "remote" adapter to the office adapter) and Receive (data sent from the office adapter to the "remote" adapter) tests in each location for one minute each. When transmission speed dropped, I sometimes changed the test file size back to the script's 100,000 Byte default, to improve the ability to see throughput variation.
Note that the physical distance between outlets doesn't necessarily correspond to the level of signal attenutation (and often subsequent throughput reduction) presented by each outlet. That depends on the actual path that the poweline networking signal must travel between the two adapters. Today's powerline networking technology uses both conducted and radiated signals. So signal loss also depends on coupling between AC mains phases and between circuit breakers, as well as conducted impedance and resistance.
After my last HomePlug AV testing, I discovered a more important source of powerline networking signal attenuation, that was not reflected in previous reviews. In the U.S., the National Electrical Code (NEC) has mandated the use of AFCI (Arc Fault Circuit Interrupter) circuit breakers to protect bedroom outlets for new residential construction as of January 1, 2002. Since my lab / office is located in a converted bedroom, the "local" adapter (the one not moved) is behind an AFCI breaker. It also turns out that test Location B is also located in a bedroom, so that outlet is also behind an AFCI breaker.
Note: The 2008 NEC expands the mandated use of AFCI breakers to include hallways, family rooms, closets and many other areas. This isn't effective in all states, yet, but it is coming.
So I'm going to present two sets of results so that the AFCI-related effects are clearly seen:
- No AFCI - No tested outlets are behind AFCI breakers. This would represent best-case performance.
- Local and Location B behind AFCI - The "Local" adapter (located in my lab/office) is behind an AFCI outlet, as well as the outlet in Location B.
I'll also be presenting some other results that represent even better and worse performance than I found in the test runs above.