Brian's Brain

Yesterday afternoon's SMPTE conference presentations on 'HD For the Consumer', specifically the networking technologies discussion by Stephen Palm of Broadcom, reminded me that I haven't yet told you about my recent tests of Panasonic's HD-PLC powerline networking technology. As I mentioned as an aspiration late last month, I successfully got my hands on several '190 Mbps' HD-PLC adapters and plugged them into the locations where I've currently got powerline 'spurs' in stable operation; between my home office and our backyard 'hut', and between the office and a closet in the middle of the house. Review this writeup, specifically this diagram, before continuing, along with my prior test results from other 'high speed' powerline technologies (HomePlug 1.0 Turbo and DS2) compared to the 'raw' CAT5-connected transfer speeds to and from the Infrant ReadyNAS.

I was surprised, upon cracking open the HD-PLC box, to find no software inside. Panasonic ships the adapters in two-unit packages, with one unit factory-configured as a 'master' (i.e. connected to the router) and the other as 'terminal' (i.e. at the other end of the powerline spur). A user-accessible switch enables easy reconfiguration from 'master' to 'terminal' or visa versa. I plugged one adapter into the office outlet, the other into the outlet in the closet, and within a few seconds the front-panel LEDs on the two units indicated that they'd established a solid connection. Better yet, a diagnostics code entered by pressing the 'setup' button suggested that the 'terminal' unit had measured and deemed the link bandwidth worthy of a 'Best' (i.e. 30 Mbps or higher) rating.

I didn't have quite the same plug-and-play experience when I tried to add a third adapter (i.e. a second 'terminal' unit) to the network. In order to accomplish this you need to first depress the recessed reset button on the unit to be added, then depress both its and the 'master' unit's setup buttons in any order, but within 5 seconds of each other, thereby necessitating that the two units be in close proximity. In spite of repeated attempts, I never was able to get the 'master' and new 'terminal' units to pair in my office, for some unknown reason. When I unplugged both units and moved them to a shared outlet in the kitchen, they paired up just fine. And they remained paired after I moved the 'master' back to the office and the second 'terminal' to the hut (which also subsequently assigned a 'Best' rating to its connection with the 'master').

Neither powerline spur exhibited any sort of protocol incompatibility; my Xbox 360, for example, saw my laptop PC just fine over UPnP. Pings to Yahoo's server over powerline typically also got 'ack'd' in 20 ms or less. I did occasionally see evidence of lost packets, in the form of non-ack'd pings, but this imperfect behaviour would seemingly disappear after the powerline connection to my router (and from there to the Internet) had been established for a few minutes.

In past tests, I've put the ReadyNAS in the hut and transferred files between it and my Gigabit Ethernet-connected desktop PC in the office. This time around, I left the ReadyNAS in the office and connected it to a CAT5-tethered laptop computer in the hut. The specific file I transferred was the rental movie Ultraviolet from CinemaNow, at 857,319,619 bytes in size. Note in assessing the following data that HD-PLC adapters employ 128-bit AES encryption that, as far as I can tell, cannot be disabled (for potential performance improvement reasons).

Looking back at my previous testing, you'll note that the raw sustained ReadyNAS read and write speeds are around 90 Mbps. '85 Mpbs' HomePlug 1.0 throttled that best-case speed back to 20 Mbps (for data transfers from the office to the hut) and 15 Mbps (visa versa). And '200 Mbps' DS2 technology, in my testing environment, only delivered 35 Mbps sustained speed (30 Mbps with interference filters turned on) for office-to-hut file transfers, and 25 Mbps sustained (20 Mbps with filters on) for hut-to-office data swaps.

Continued with 'HD-PLC: Data and Analysis'....