A little caution ... transmit power does not necessarily equate to speed.
Speed is a combination of signal strength, signal quality (lack of noise or
interference) and distance. And doubling the output power will not result in
double the speed.
Transmit power will give you further distance, but depending on the other
factors above and the client output power you may not see any gain in distance.
From: Colton Conor
Sent: Thursday, November 13, 2014 4:42 PM
To: r...@sbnettech.com ; WISPA General List
Subject: Re: [WISPA] 2dbi vs 3dbi vs 5 dbi vs 100mw vs 400mw
We are deploying a DSL network, and Broadcom is the leader in the DSL chipset
market. So most all these modems we are using have a Broadcom SoC design with
the VDSL2 modem, 802.11N 2x2 MIMO, Ethernet Switch, and CPU all built in. The
only thing the modem manufacturers change is the power output on the Broadcom
wifi (via a amp on the broad) and the selection of internal or external omni
antennas for the most part. Plus some tweak the wifi settings.
We are trying to decide if it is worth the small price premium to pay for the
modem that has the high powered amp at 400mw vs the regular ones that only have
100mw. Sounds like the the high powered ones are worth it especially since we
have no control of the clients devices (I guess you rarely ever do anyways) and
we are only supplying one AP/router per home.
I guess this is why AT&T uverse gets such good ratings and reviews from their
customers on wifi? They are using 2Wire/Pace modems for the most part that have
all high powered wifi. Thats why in an AT&T area you can see tons of them.
On Thu, Nov 13, 2014 at 5:59 PM, Ryan McKenzie <r...@lirr.net> wrote:
I second what Josh is saying. I build out a lot of hotels and large offices,
and because of iPhones and iPads, we've started doubling up on the AP's we
normally would deploy. In an indoor environment, it's really tough to do a
very directional antenna because you are usually trying to cover a 360 deg
area, so high power AP's, low gain antennas, and more AP's is usually the best
approach.
That being said, I'm curious about your specific choice of Broadcom radios in
your first post. Usually that means you are trying to utilize custom firmware
such as DD-WRT or Sputnik, etc. Is this the case? If so, it would be
interesting to hear what you are trying to accomplish. I've played with many
of those for a long time, until I really saw the capability and power of the
Unifi, and stopped messing around with anything else.
Just curious as Broadcom is not a radio chipset you hear much about on this
list.
Thanks,
Ryan McKenzie
Office 385-215-WIFI
Cell 801-309-6161
On 11/13/14 4:41 PM, Josh Luthman wrote:
You are correct. It never will. Rx can only be improved by a bigger
antenna to listen with. Antenna gain always has and will be better than raw
power.
Unless you include the other side's Tx, in which case more power and gain
will help. In the Wifi world you're totally screwed because it's a terrible
laptop/phone/game console/tablet/etc in which case you can't do ANYTHING to
their devices.
Josh Luthman
Office: 937-552-2340
Direct: 937-552-2343
1100 Wayne St
Suite 1337
Troy, OH 45373
On Thu, Nov 13, 2014 at 6:34 PM, Colton Conor <colton.co...@gmail.com>
wrote:
Awesome, I am already learning so much from this mailing list. So it
sound like the author was right. So boosting the power output on the AP will
more than likely boost the TX (downlink) speed on the AP side, but do nothing
on the RX speed side of the AP since nothing from the clients sending
perspective has changed right?
On Thu, Nov 13, 2014 at 3:43 PM, Ben West <b...@gowasabi.net> wrote:
Yes, radios will negotiate different rx/tx rates to each other, so up
to 2 distinct rates for a single link. On the open source mac80211
linux-wireless driver you can see this explicitly. The rx/tx on one radio is
the tx/rx on the other.
root@ap1:~# iw wlan0 station dump
Station 52:e6:fc:XX:XX:XX (on wlan0)
inactive time: 70 ms
rx bytes: 769202553
rx packets: 4644034
tx bytes: 326581907
tx packets: 465139
tx retries: 76461
tx failed: 4
signal: -56 [-57, -62] dBm
signal avg: -55 [-57, -62] dBm
tx bitrate: 117.0 MBit/s MCS 14
rx bitrate: 86.7 MBit/s MCS 12 short GI
authorized: yes
authenticated: yes
preamble: long
WMM/WME: yes
MFP: no
TDLS peer: no
root@ap2:~# iw wlan0 station dump
Station 62:66:b3:XX:XX:XX (on wlan0)
inactive time: 10 ms
rx bytes: 569548806
rx packets: 3191667
tx bytes: 412571117
tx packets: 490879
tx retries: 104831
tx failed: 1
signal: -57 [-67, -57] dBm
signal avg: -55 [-62, -56] dBm
tx bitrate: 86.7 MBit/s MCS 12 short GI
rx bitrate: 117.0 MBit/s MCS 14
authorized: yes
authenticated: yes
preamble: long
WMM/WME: yes
MFP: no
TDLS peer: no
On Thu, Nov 13, 2014 at 3:27 PM, Colton Conor <colton.co...@gmail.com>
wrote:
In my situation, we are assuming we are dealing with a location with
one and only one AP (typical home) and most devices are tablets and smartphones
who's antenna's and power output can't be modified. Can be either a 1 or 2
story home.
So, how much truth is in this article:
http://tomatousb.org/tut:increasing-wrt54g-transmit-power
The author is claiming that wifi negotiates speed (correct) but in
both directions in the uplink and downlink side. He is basically claiming if
you increase the power output at the AP, then the downstream (from AP to
client) link rate will increase, while the uplink (Client to AP) will stay the
same. This make sense, but does wifi really established a different PHY rate
for up and down stream. Is this correct?
On Thu, Nov 13, 2014 at 3:09 PM, Jack Unger <jun...@ask-wi.com> wrote:
Going from 20 dB to 26 dB will allow the AP to be heard (with the
same reliability) at double the distance away.
Yes. If the client power (actually the client EIRP which includes
the antenna gain) stays the same then the "uplink" distance from client to AP
will still be the same.
Yes, increasing the number of APs is one possible solution. Another
is to use a higher-gain (more directional) antenna on the AP recognizing that
when you increase the AP antenna gain in one direction, you are reducing the
gain (and the coverage) in all other directions.
jack
On 11/13/2014 11:10 AM, Colton Conor wrote:
So going from a regular powered 100mw (20db) to a high powered
400mw (26db) is a 6db increase in output power. So you are saying going from
regular to high powered is a double in coverage size?
Doesn't increasing the power output at the AP only increase how
loud the AP can "shout" which in term dictates how far the receiver can hear
from? If the client can't shout back does this do any good?
Most client devices today like iPads, Smartphones, and some
laptops can't be modified to increase their antenna gain or power output. So
the only option is to increase the numbers of APs, or the transmit
power/antennas at the AP right?
On Thu, Nov 13, 2014 at 12:25 PM, Jack Unger <jun...@ask-wi.com>
wrote:
To double the communications distance (everything else holding
steady) requires an additional 6 dB. Knowing this, you can do the math with the
various antenna gains and power levels to determine performance.
Regards,
Jack Unger
WISPA FCC Technical Consultant
On 11/13/2014 10:15 AM, Colton Conor wrote:
We are comparing multiple SOHO routers and modems that have
the same Broadcom chipsets. All of them have 802.11N 2x2 configuration. The
only differences between them are if they have internal or external antennas
and the gain of the antennas (either 2, 3, or 5dbi ratings). In addition, some
sell a high powered wifi radio (400mw) while others have the basic (100mw).
How much a difference does each of these hardware features
make in overall wifi performance?
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Serving the WISP Community since 1993
760-678-5033 jun...@ask-wi.com
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