Is Your Router's Transmit Power Juiced?

[thiggins]

Higher Power Now Allowed For 5 GHz Wi-Fi

Article updated.

 

[sfx2000]

sfx: Are you saying that the measurement technique and comparison was invalid?

I'm not saying that the test was improper or invalid - but conducted power is only part of the story.

Going back in history a bit - the methodology used in the SNB router testing - the OctoScope MPE chamber - and there you have the radiated paths - with proper setup, tools, and calibration, the SNB team should be able to get the Tx/Rx values and work the numbers back from there.

sfx

 

[Razor512]

yay now all they need to do it update the other rules to increase the transmit power to at least 5 watts (they allow it for some of the other unlicensed bands).

5GHz inherently has a shorter range, so more transmit power will do it good, especially for covering an entire home properly without dropping to horribly low speeds.

 

[thiggins]

I'm not saying that the test was improper or invalid - but conducted power is only part of the story.

Going back in history a bit - the methodology used in the SNB router testing - the OctoScope MPE chamber - and there you have the radiated paths - with proper setup, tools, and calibration, the SNB team should be able to get the Tx/Rx values and work the numbers back from there.

You are right that this is only one spec. I chose it because it was relatively easy to measure.

NETGEAR's suit alleges multiple spec violations in addition to conducted power. ASUS is off the hook on only this one.

I won't be pursuing any other tests. Too many other things to do!

 

[stevech]

As we know, MIMO is all about coping with multipath. Indoors, the average delay spread is around 55nSec RMS.

Testing in a small chamber or RF shoebox is not a good approach, in my opinion. But testing with a fade/delay channel simulator is normally done with wired connections. A bit hard to do this with consumer MIMO WiFi and the economical ways they fabricate antennas.

Building a mock up of a "typical" residence or office building area is impractical.

Sorry, but I don't have a good suggestion on a solution. I do know that testing without realistic multipath conditions will skew the conclusions too much.

 

[sfx2000]

As we know, MIMO is all about coping with multipath. Indoors, the average delay spread is around 55nSec RMS.

Testing in a small chamber or RF shoebox is not a good approach, in my opinion. But testing with a fade/delay channel simulator is normally done with wired connections. A bit hard to do this with consumer MIMO WiFi and the economical ways they fabricate antennas.

Building a mock up of a "typical" residence or office building area is impractical.

Sorry, but I don't have a good suggestion on a solution. I do know that testing without realistic multipath conditions will skew the conclusions too much.

The OctoBox MPE does support the IEEE Model B - it's a really cool box - and it's not just tx/rx measurement - it has a fader built in, so it should support both Rayleigh and Rician fading on the channel.

Would be fun to get some time on the box - I could make it dance

 

[thiggins]

Would be fun to get some time on the box - I could make it dance

Sure sfx, c'mon over. The new testbed I am bringing up has the 38" chambers and a turntable in the DUT chamber, too.

 

[sfx2000]

Sure sfx, c'mon over. The new testbed I am bringing up has the 38" chambers and a turntable in the DUT chamber, too.

Sweet - nice upgrade

Would be awesome to head over - but me being out in SoCal, it makes it a bit of a challenge

 

[stevech]

How many paths in the channel simulator?

 

[thiggins]

How many paths in the channel simulator?

The current testbed has three. The new one has 4.

 

[sm00thpapa]

To get the 1W on lower channels will this need a FW upgrade for current routers?

 

[thiggins]

To get the 1W on lower channels will this need a FW upgrade for current routers?

That would make sense.

 

[RMerlin]

To get the 1W on lower channels will this need a FW upgrade for current routers?

That would be assuming that the hardware can support it. I have no idea if that's the case.

 

[sm00thpapa]

Ok thank you guys.

Sent from my LG-D800 using Tapatalk

 

[thiggins]

That would be assuming that the hardware can support it. I have no idea if that's the case.

Let me rephrase my answer.

Yes, I firmware change would likely be needed. But all it would be able to do is let the Channel 36 - 48 power be about the same as the power in the higher channels.

 

[azazel1024]

Assuming that the rest of the hardware can support that.

My brother has been doing a lot of tinkering and it looks like some/most/all routers' radio have seperate firmware that is not updateable through the routers main firmware. If the cap is in the radio firmware, it might not be something that can be changed without a hardware revision. His Netgear 3700 (I think it is a 3700) has such an issue where he can crank the radio power through Open WRT, but it does nothing as the 5GHz radios actually have a hard limit encoded in the lower channels (40mw I think he said).

 

[sm00thpapa]

Would be nice if Linksys put the mw that the WRT1900AC transmits. Or at least have it adjustable.

Sent from my LG-D800 using Tapatalk

 

[RMerlin]

One thing that worries me, from the RevolutionWifi article linked by Tim:

http://www.revolutionwifi.net/2014/04/impact-of-fcc-5-ghz-u-nii-report-order.html

All devices (AP or client) operating in any U-NII band must be secured to prevent unauthorized software modification and to ensure it operates as approved to prevent harmful interference. The exact methods used to secure the software are left to the manufacturer, but must be documented in their application for equipment authorization to the FCC. The FCC is not setting specific technical security requirements since they are likely to change over time, but rather defining the capabilities that should be implemented by manufacturers. They do make note that more detailed security requirements may be necessary later as software-defined radio technology develops. They also declined to implement rules that would force manufacturers to render a device inoperable if unauthorized modifications were made, citing additional complexity and costs resulting in questionable benefits above the software security being mandated.

I hope this would only apply to the radio firmware and not the router firmware itself...

 

[azazel1024]

I would butt-ume it just means radio firmware.

I wouldn't bet any of my own money on that though.

 

[stevech]

I haven't seen any OFDM broadband gear under $5K that can produce OFDM at 1 watt Pout (excluding antenna gain). Too costly. No market. The long point to point links use 30dBi dishes and start with about 0.1W Pout - and radiate 0.1W (20dBm) + up to 30db = 50dBm in a narrowbeam pattern (to be FCC legal in EIRP).

OFDM's need for high linearity (unlike 802.11b, and lowest speeds of 11g/n), lead to expensive amplifiers. And going from the typical consumer 802.11n or 11ac at well under 100mW at high modulation orders, to 1000mW, would be quite expensive.