Powerline Networking with the Western Digital Livewireby Ganesh T S on August 24, 2010 7:50 AM EST
- Posted in
- Powerline Adapters
Most of the CE devices in the market today connect to the Internet as well as the home network. While many of them have the capability to connect to wireless networks, it is not really a great option for many of the bandwidth hungry units. Examples of such units include Netflix streaming TVs or media streamers such as the WDTV Live. Many a consumer has been frustrated by the incessant buffering and playback stuttering while putting wireless networks (even of the 802.11n variety) to use in such scenarios. Further, not all consumers have the luxury of a flawless wireless network in their residence. Running an Ethernet cable around the house is one option, but it is too cumbersome and costly for many. In this scenario, the electrical network within the house looks like an unexploited part of the equation.
The HomePlug AV standard aims to deliver networking capabilities around the house by taking advantage of the already existing electrical wiring. It is the baseline specification for the upcoming IEEE standard (IEEE P1901). There are other competing standards (we will cover them briefly in the next section), but the product being covered today adheres to the HomePlug AV standard. If you are interested in only finding out how the WD Livewire performs, please feel free to continue reading from the 'Unboxing & Setup Impressions' section onwards. On the other hand, if you want to learn about the history of powerline networking and the companies active in this space, this, as well as the next section, will be of interest.
Wikipedia traces the history of the HomePlug standard quite well. We have been following the consumer powerline networking area over the last 4 or 5 years, and realized that there is only one chipset vendor shipping any appreciable amount of chips in this space. Intellon, acquired by Atheros towards the end of 2009, is the brain behind almost all the powerline network adapters shipped in the last few years. Belkin claimed a 1 Gbps powerline adapter last year based on the Hispano-Scottish startup Gigle Semiconductor, but the reviews indicated that it performed no better than the 200 Mbps chipsets supplied by Intellon. When Western Digital contacted us to review their first product in this space, and indicated that the PHY rate was at 200 Mbps, we had little doubt that this would be another unit based on the Atheros (Intellon) chipset. Our suspicions were confirmed later (details can be found in the 'Livewire Internals' section).
In the 2010 CES, Atheros / Intellon introduced their fourth generation HomePlug based chipset, the AR7400. As the release indicates, the AR7400 is supposed to operate at a PHY rate of 500 Mbps for powerline applications, but gets a boost to 700 Mbps over coax cables. However, units based on the AR7400 are yet to hit the market. All Atheros/Intellon based products shipping currently are based on the third generation product, the INT6400.
The first generation chipsets introduced way back in 2001 had PHY rates of 14 Mbps (the real throughput was much lesser). The second generation products had a PHY rate of 85 Mbps, while the INT6400 third generation products ups this to 200 Mbps. With the advent of HD media streaming (and multiple streams, at that), 200 Mbps PHY rates are barely enough, and Western Digital has wisely decided to advertise the Livewire kit as being meant for sharing an Internet connection. That said, an idea of the effective bandwidth available also indicates the suitability of the product for data and media transfer within the home network.
As already indicated, the WD Livewire product is based on the HomePlug standard. Are there any other standards available for networking with already existing cables? Do they work, and are they shipping? We will cover this in detail in the next section.
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jkostans - Tuesday, August 24, 2010 - linkEthernet is not twisted to prevent radiation, it's to reduce noise in a differential transmission line. (The fact that ethernet signaling is differential reduces radiation and loss but not the twists) In theory by keeping the wires as close as possible any noise that influences one wire will equally influence the other wire in the same manner. When the subtraction is done to find the voltage, the net result of the noise will have no effect. It's like the equation (5+X) - (0+X) = 5. No matter what value of the noise (X) is, the equation will always equal 5.
chromatix - Tuesday, August 24, 2010 - linkThe twists have both effects, and effectively isolate the electromagnetic fields of the wires and their surroundings up to a certain frequency and down to a certain distance. It is the isolation which eliminates both emissions and received noise.
flgt - Tuesday, August 24, 2010 - linkI think to some extent you're both right. The reduction in emissions comes from the fact that the signal is driven differentially (equal amplitude, opposite polarity) and the control of the electric fields which are generated. In a non-perfect transmission line there is a finite amount of cancellation between the two fields which can be improved with cable construction (Cat 6 > Cat 5 >> Romex). Twisting improves performance but a shield is required optimal emission performance. However the increased costs and installation time of shielded cables make them a less desirable solution as long as regulatory requirements can be met.
As stated, differential signaling provides inherent common-mode noise immunity which is aided by the tight coupling of the twisted wires. The twisting helps ensure the radiated noise excites each conductor in the pair equally (again to some finite amount).
I don’t see this being a major issue for radio operators for a number of reasons:
1) The noise immunity provided by differential signaling allows the line to be driven at lower voltage levels, thereby further reducing emissions.
2) The use of OFDM allows each individual frequency channel to be operated at very low signal-to-noise ratios due to the low-order modulation scheme being used. This is the only way they can operate over such a horrible channel in the first place (your power line). They most likely operate each carrier at a very low signal level to make the composite spectrum look more like broadband noise. DSL essentially operates in the same way.
3) The signal will quickly attenuate since the channel is so bad.
Per Hansson - Wednesday, August 25, 2010 - linkI can confirm your suspicions
I recently bought the Belkin Gigabit Powerline HD networking kit
It managed to do 5Mbps over my powerlines, an apartement built 1990
When I turned on my FM radio there was an amazing ammount of noise in the reception when I was transmitting data, less so when I was not transmitting data but still some pops and cracks in the reception
When I unplugged the adapter the reception became perfect
Next test was to run the powerline adapter from the apartement out in to my garage, the speed now dropped to 1Mbps
To my suprise though it managed to even interfere with the FM reception in my car!
The signal got way harder to recieve, it did not crack and pop in the audio tho, but I think that may be simply due to the fact that the stereo in my car is much better at receiving a signal, and the fact that the car itself acts like a faraday cage...
To say the least I returned this "Gigabit" junk
yottabit - Tuesday, August 24, 2010 - linkThere's a typo in the second sentence of the summary article on the anandtech home page... :(
reckert - Tuesday, August 24, 2010 - linkIn most homes, the electric coming in is 240v, and the circuits are split to 2 sets of 120v. I know from past experience power line protocols such as x10 couln't get their signals to jump between the two sides of the wiring without a special bridge.
ganeshts - Tuesday, August 24, 2010 - linkreckert, as you mention, x10 needed something to plug in to bridge the legs of the circuits. However, as all Homeplug stuff is on high frequency, they bridge due to the capacitive effect of the bus bars in the circuit breakers. Therefore, you will not have a problem with the configuration you mention as long as you are using HomePlug certified devices.
Souka - Tuesday, August 24, 2010 - linkMy house build 1984...2 story, 2200 sq/ft
Cable modem on second floor, tv on 1st with BriteView media player.
Netgear XE-104 (up to 85Mbs claim)... on same curcuit directly plugged into wall I got barely 15Mbps. Different circuit in adjoining rooms 5Mbps. Different circuit on different floors...under 1Mbps and often dropped connection.
BELKIN F5D4073 (up to 85Mbps) Powerline Turbo similar results...
Also tried the kits in my parents 1960's 2 story 3500 sq'ft home....worse results...
I really like the idea of powerline tech, just doesn't deliver for me
ganeshts - Tuesday, August 24, 2010 - linkSouka,
Please take a look at the SmallNetBuilder guide here, as it may be of some help to you: http://www.smallnetbuilder.com/lanwan/lanwan-basic...
It is best to buy these type of products from stores which have a good return policy / no restocking fee. Unless the consumer actually tries it out, it is not possible to know in advance as to how well the technology would work, as is evident in your case.
Souka - Tuesday, August 24, 2010 - linkI might give the XAVB5501 or XAVB5001 a shot when they come out....none of the listed retailers (or froogle.com) came up with any units available.
I do wish they had dual ports... or at least in kits one of the units had dual ethernet ports.
Yes I can easily hook a switch to it, but rather not.