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Concerns Over Increased 802.11n Power Usage
alphadogg writes "Next-generation 802.11n systems promise to considerably improve WLAN performance. But the processing required for the boost sucks up more power than the older 802.11a/b/g networks. Still, many enterprise-class Wi-Fi vendors claim to deliver full 802.11n capabilities without enterprise customers having to touch their power infrastructures. So what gives?"
Enterprise hardware does not use general-purpose CPUs, it uses special-purpose ASICs. These are lower power than general purpose hardware. They are fab'd using a newer process than the older ones, and so use less power per transistor than the old chips. Less power per transistor means more transistors (which means more processing power) per watt. If you rolled out 802.11g infrastructure four years ago, you can now fit around three to four times as many transistors on the same area of silicon as was possible when you deployed your current infrastructure.
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Maybe skimming TFA wasn't the best basis for comment. The article mentions no power issue at the client. It's basically saying that:
It's like 8 watts instead of 3 watts (not exact numbers). It's not a significant amount of power. That's why you don't need to upgrade your infrastructure.
I'm not sure how a silly article like this gets published. If it was tons of power, how could they make 802.11n adapters for laptops?
First of all, this has little to do with what is usually considered power infrastructure. This has to do with power-over-ethernet. It appears some dual band 802.11n radios require more power than one particular specification (802.3af) allows. Solution? Don't use 802.3af, or, don't use the radios which require too much power. Not really a big deal. I expect that manufacturers will bring the power requirements down to allowable levels over time.
Essentially just because vendor A has devices which consume "up to 18 watts" it doesn't mean that nobody can build devices which take less than 13 Watts.
That's just 5 watts difference. You could probably achieve this by switching to higher efficiency components. Or you could store some energy for the short bursts of transmission, getting a steady power of 13 watts.
Keep in mind that most vendors probably still have the very first itteration of hardware. It will significantly improve over the next years anyhow.
A laptop, 802.11n
Suckin 18 watts, instead of 15,
It's way less than a lightbulb, on a dull day
But the article author thinks there's no way
And isn't it ironic, don't you think?
No, sorry, can't see the irony there. And ffs for the 3 extra watts per base station/machine, it amounts to switching on a couple of extra lights at the company. I know it's still better to save power where you can, but needing a new power infrastructure to support it? You have to lol. *sigh*
which is totally what she said
Multiple radios in simultaneous operation (Read: MIMO) plus the circuits to coordinate and control the radios and it has *double the bandwidth* (in the physical layer) = more power use by the 802.11n device. Duh! (Also notice there are more and larger antennas?) http://en.wikipedia.org/wiki/IEEE_802.11n
If the big deal in the article is over PoE powered 802.11n solutions, just exceed the power spec at the power injector and use 24 Gauge CAT6 UTP (or larger Gauge CAT6 for longer runs) for your PoE runs to lower electrical resistance.
I have installed PoE devices that have their own proprietary power injectors that exceed the PoE power standard. The problem is where people use long runs of super cheap CAT5 and lots of punch-downs and they expect also their large switch with PoE injection to provide PoE to whatever is connected. There is a reason that the manufacturers' of powered by PoE devices do provide their own wall-wart PoE injectors...
The summary sucked, but this is clearly about Power over Ethernet, for which that 5% can be quite significant.
I bet most of the energy is in the form of heat from the individual DC converters plugged in to long extension cords laid along the drop ceiling to the nearest electric column.
And you'd be incorrect. Most corporate infrastructures that heavily/professionally deploy wireless is going to due it via PoE - putting in a PoE switch or injector is much cheaper than wiring dozens or hundreds of new power jacks up in ceilings and such. With PoE all you need to do is run a ethernet cable over to the AP to provide both network access and power.
And PoE is only capable of transmitting so much power. 12.95 watts at the device. The new N devices are being reported at 18 watts. We have a little problem here...
While the processing requirements of N is requiring more wattage at the processor, I figure that the dual-radio feature of N is also significant - corporate ones you normally have both a 2.4GHz and a 5GHz radio. With N you're possibly doubling the number of radios to four. This increases power demand. If nothing else, you're also subletting the frequency spectrum even more, thus need to, on average, transmit at a higher power level overall to beat the noise floor.
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Enterprise hardware does not use general-purpose CPUs, it uses special-purpose ASICs
Actually they don't - take a look in a high-end AP some time. "Enterprise" wireless systems use the same, or often older generation, of wireless technology that is in consumer access points. Competition in the consumer AP market is what drives all the incredible price/performance in wireless technology, and I assure you nobody is going to spend the tens of millions to do a custom spin of one of those chipsets for the relatively small high-end market. Those products sell on branding, special software features, and support contracts, not silicon performance. And as far as the CPU/memory etc, these are going to be much LESS specialized in a high-end system than in a consumer AP. Low-cost APs use highly integrated ARM or MIPs-based SOCs that are designed for sub $20 BOM cost. A higher-end system, however, is not bound by BOM costs and might have four times the memory and a more general purpose processor capable of running more software.
Routers and switches are a different story, and those DO use ASICs and FPGAs. The high-end models of these have to deliver a totally different hardware feature set than consumer equipment, and unlike wireless technology, the bleeding edge tends to be developed for the highest priced products before trickling down.
Just because a given access point will use "up to 18watts" does not mean it will always use 18watts. As long as the average power consumption is under what the supply can deliver, all can be well. Several possibilities exist.
Best case is that the supply can deliver short term bursts of power sufficient to meet the demand. This is realistic in most scenarios today, as supplies are typically rated by long-term average power. For example, the 20amp breaker on your typical home circuit will easily supply a few seconds at 30amps. My irrigation pump is rated at 28amps, the breaker at 50amps, and the pump draws over 100amps every time it starts. No problems.
Worst case is the access point requires some local power storage to meet the demand. This might take the form of a supercap or rechargeable battery. Average power usage keeps the battery charged, and peak demands are met from the battery. Only if the battery becomes depleted does the access point have to limit power usage -- perhaps by limiting transmit power or by limiting speed.
sdb
There is several ways vendors are getting around the power issue with .11n, by only having one antenna or by doing some software trickery where instead of getting 15.4 watts over every interface you lower the power to a couple and redistribute that power to get it to 18watts , (I know Cisco is doing this on their 3750-E switches and have been told they plan on it on their 4500E switches). Since most companies don't put 30 access points on one switch anyway (would be bad if that switch went out!) that probably will not be an issue, unless you run IP phones that eat a lot of juice also.
What I see as the large issue is that a significant amount of people have only 10/100 to the copper port and to run 802.11n you must have 1Gb copper to provide full bandwidth. (then power the device by how ever you want PoE, injector, wall plug)
Actually my informations is only 5 years out of date and from a quick Google search the 1300 series AP which is their next to newest offering is also ASIC based, so I wouldn't consider it so out of date =) They considered the stuff they could build into the ASIC to be a competitive advantage and knew that they could be to market with a new product months before the major chip houses would have even engineering samples. To be more on-topic their 1250AP which is 802.11n draft 2 compliant is only supported with one radio if powered by a 802.3af switch but you can use two radios if you have a Catalyst switch with 18.5W power capability or if you use the power injector. They claim 16.9W max power draw with 2 radios or 12.95W with one radio.
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Uh, no it can't. 18W - 100mW is 17.9W. Even if you cut the transmit power to zero, you're still not going to be able to cut 6W. That's like trying to empty a bathtub with a single bucket without making multiple trips....
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