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SweetSunday
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Using B/G

Fri May 30, 2008 6:11 am

I guess this is covered in Wireless Networking 101 but I didn't get to Wireless College so I beg you bear with me:

I've a small network with one client just at the edge of the AP's transmission lobe and not a clear line of sight so his TX/RX readings have always been low (eg -85/-88) and his PPPoE link frequently drops out although the wireless doesn't seem to disconnect.

To try to get around this I decided to try reverting the whole network from G-only to B-only as everyone is limited to download speeds of 2mbps anyway.

It seems to have helped the 'outlying' CPE as its CCQ has gone up appreciably, but the CPE closest to the AP has started behaving oddly (it seems to me). I couldn't remember which antenna socket on the card the pigtail was attached to so changed it in Winbox and tried both. This is the result-

With antenna a

status: connected-to-ess
band: 2.4ghz-b
frequency: 2412MHz
tx-rate: "11Mbps-SP"
rx-rate: "1Mbps"
ssid: "Totaranui"
bssid: 00:80:48:3D:5A:6A
radio-name: "Mt. Kiwi B"
signal-strength: -51dBm
tx-signal-strength: -54dBm
noise-floor: -97dBm
signal-to-noise: 46dB
tx-ccq: 56%
rx-ccq: 82%
p-throughput: 7823
overall-tx-ccq: 56%
authenticated-clients: 1
current-ack-timeout: 30
wds-link: no
nstreme: no
framing-mode: none
routeros-version: "2.9.51"
last-ip: 10.0.3.1
802.1x-port-enabled: yes
authentication-type: wpa2-psk
encryption: aes-ccm
group-encryption: aes-ccm
compression: no
current-tx-powers: 1Mbps:16(16),2Mbps:16(16),5.5Mbps:16(16),11Mbps:16(16)
notify-external-fdb: no


With antenna b

status: connected-to-ess
band: 2.4ghz-b
frequency: 2412MHz
tx-rate: "11Mbps-SP"
rx-rate: "1Mbps"
ssid: "Totaranui"
bssid: 00:80:48:3D:5A:6A
radio-name: "Mt. Kiwi B"
signal-strength: -74dBm
tx-signal-strength: -70dBm
noise-floor: -94dBm
signal-to-noise: 20dB
tx-ccq: 76%
rx-ccq: 93%
p-throughput: 7403
overall-tx-ccq: 76%
authenticated-clients: 1
current-ack-timeout: 30
wds-link: no
nstreme: no
framing-mode: none
routeros-version: "2.9.51"
last-ip: 10.0.3.1
802.1x-port-enabled: yes
authentication-type: wpa2-psk
encryption: aes-ccm
group-encryption: aes-ccm
compression: no
current-tx-powers: 1Mbps:16(16),2Mbps:16(16),5.5Mbps:16(16),11Mbps:16(16)
notify-external-fdb: no


It seems from the signal strengths that the antenna 'mode' is A (TX -54dB as opposed to B's TX of -70dB) but the CCQ for antenna B is significantly better.


Will anyone take the time to:

1. Explain the apparent contradiction.

2. Is it that I need to turn the TX power down? If so, how and what am I aiming for?

3. What does the -SP mean in the TX rate? The AP is running 2.9.51 but the CPE is running 3.9.

4. Would I be better switching the AP to B/G mode and the CPE's with good signals back to Only-G mode? Or can I switch everything to B/G and let the system sort it out?

5. Enlighten me as to anything else I need to know.

Thanks.
 
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jwcn
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Re: Using B/G

Fri May 30, 2008 7:27 am

You want to aim between -64 and -72 for signal. I think in this case less signal is just performing better than more if that makes and sense.
 
SweetSunday
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Re: Using B/G

Fri May 30, 2008 11:47 pm

You want to aim between -64 and -72 for signal. I think in this case less signal is just performing better than more if that makes and sense.
Fine, but how do I turn the signal down? Is it just a case of deliberately misaligning the antenna or can it be done by twiddling a knob on the card - the 'TX powers' tab in Winbox for manual setting looks like this:
TX.jpg
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jwcn
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Re: Using B/G

Sat May 31, 2008 3:21 am

You can go below 17...
 
SweetSunday
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Re: Using B/G

Sat May 31, 2008 8:16 am

You can go below 17...
Yes, but *how*?

Do I manually alter the number in the Tx Powers window? If so, what do I alter it to?

What am I actually looking at in this window? In what way is it supposed to be useful, if it is?

Is there a dB setting at which I could still get 5.5Mbps but not get 11Mbps any more? How would I know?

I'm still running with 2.4GHz-B. Could I revert to 2.4GHz only-G but with a setting giving me a good stable 18Mbps across the link at a Tx/Rx CCQ of 100/100? That's likely to be more than anyone is ever likely to want.
 
Tanker
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Re: Using B/G

Sat May 31, 2008 4:04 pm

Set it to "Card Rates"....

... and select the power you want - DO NOT go ABOVE the card's abilities... this feature is ONLY to turn down the power otherwise you'll fry the card - quickly..!!

I have some set down as low as 8....

Hope this helps

T
 
SweetSunday
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Re: Using B/G

Sun Jun 01, 2008 12:24 am

Thanks.

Three follow-on questions;

1. Is it OK to change the card rates while it's running or should it be disabled first?

2. Having changed the rate (down to 12, disabling it first)) I noticed on the status tab that the Rx/CCQ seemed rock solid on 100% but the Tx/CCQ rate was jumping around 46 - 54%. Is this just attenuation caused by the intervening atmosphere or is the card itself trying to fine tune something? If the latter how long should I leave it to 'settle' before interfering and are there any knobs I can twiddle to assist this process.

3. Presumably the ideal Tx/Rx is 100/100 which I had with this card at default power (17?). However is CPE sits right in the middle of the AP's antenna lobe. Will I be 'drowning out' the weaker CPEs further out or on the edge of the lobe at this setting, and if so is the 'socially responsible' ideal to have everyone's setting at whatever gives it a Tx signal strength around that of the weakest on the network? Or is there some esoteric compromise formula?

Given that I download much more than I upload - about a 10:1 ratio - I'd assume that at the CPE end a high Rx is more desirable than a high Tx /low Rx CCQ

Thanks for your patience.

(An additional observation - with the card rate at 12 the Tx/Rx signal strength is still -59/-60dB but the Tx/Rx CCQ is 50/100%. Surely the Tx should be higher. Is this telling me something?)
 
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jwcn
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Re: Using B/G

Sun Jun 01, 2008 12:31 am

As you decrease the CPE power you need to be looking at the AP not the CPE for the signal.

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