So we have the set of the systems:

System "A" is x86 machine with Atheros 2.4Ghz card set to station mode, PC in shielded and grounded metal box

System "B" is x86 machine with two Atheros 2.4Ghz cards set to ap bridge mode, PC in shielded and grounded metal box.
Antenna to system "A" set to vertical polarization
Antenna to system "C" set to horizontal polarization

System "C" is x86 machine with Atheros 2.4Ghz card set to station mode, PC in shielded and grounded metal box


All have the same config: ROS 3.22, nstreme enabled, enable pools, disable CSMA, framer policy = exact size, framer limit = 4000


System states:

1) Link A-B and B-C is idle
System "A": Signal strength -69, Tx Signal strength -69, Signal to Noise 32, Tx/Rx CCQ 46/62, Tx/Rx Rate 54Mbps/48Mbps, P Throughput 25000
System "B", card to system "A": Signal strength -69, Tx Signal strength -69, Signal to Noise 34, Tx/Rx CCQ 58/38, Tx/Rx Rate 54Mbps/48Mbps, P Throughput 29000

System "B", card to system "C": Signal strength -65, Tx Signal strength -64, Signal to Noise 36, Tx/Rx CCQ 98/100, Tx/Rx Rate 54Mbps/54Mbps, P Throughput 30000
System "C": Signal strength -64, Tx Signal strength -65, Signal to Noise 37, Tx/Rx CCQ 100/98, Tx/Rx Rate 54Mbps/54Mbps, P Throughput 30000

2) Link A-B with low traffic
System "A": Signal strength -69, Tx Signal strength -73, Signal to Noise 30, Tx/Rx CCQ 40/64, Tx/Rx Rate 18Mbps/24Mbps, P Throughput 8000
System "B", card to system "A": Signal strength -73, Tx Signal strength -69, Signal to Noise 30, Tx/Rx CCQ 64/30, Tx/Rx Rate 24Mbps/18Mbps, P Throughput 18000

System "B", card to system "C": Signal strength -65, Tx Signal strength -64, Signal to Noise 36, Tx/Rx CCQ 98/100, Tx/Rx Rate 54Mbps/54Mbps, P Throughput 30000
System "C": Signal strength -64, Tx Signal strength -65, Signal to Noise 37, Tx/Rx CCQ 100/98, Tx/Rx Rate 54Mbps/54Mbps, P Throughput 30000

3) Link A-B with high traffic
link form A to B disconnects every second

System "B", card to system "C": Signal strength -65, Tx Signal strength -64, Signal to Noise 36, Tx/Rx CCQ 98/100, Tx/Rx Rate 54Mbps/54Mbps, P Throughput 30000
System "C": Signal strength -64, Tx Signal strength -65, Signal to Noise 37, Tx/Rx CCQ 100/98, Tx/Rx Rate 54Mbps/54Mbps, P Throughput 30000

4) Link B-C with low or high traffic
System "A": Signal strength -69, Tx Signal strength -73, Signal to Noise 30, Tx/Rx CCQ 40/64, Tx/Rx Rate 24Mbps/36Mbps, P Throughput 11000
System "B", card to system "A": Signal strength -73, Tx Signal strength -69, Signal to Noise 30, Tx/Rx CCQ 64/30, Tx/Rx Rate 36Mbps/24Mbps, P Throughput 21000

System "B", card to system "C": Signal strength -65, Tx Signal strength -64, Signal to Noise 36, Tx/Rx CCQ 98/100, Tx/Rx Rate 54Mbps/54Mbps, P Throughput 30000
System "C": Signal strength -64, Tx Signal strength -65, Signal to Noise 37, Tx/Rx CCQ 100/98, Tx/Rx Rate 54Mbps/54Mbps, P Throughput 30000

5) Link B-C is off
System "A": Signal strength -68, Tx Signal strength -67, Signal to Noise 32, Tx/Rx CCQ 96/98, Tx/Rx Rate 54Mbps/54Mbps, P Throughput 30000
System "B", card to system "A": Signal strength -67, Tx Signal strength -68, Signal to Noise 33, Tx/Rx CCQ 98/97, Tx/Rx Rate 54Mbps/54Mbps, P Throughput 30000

We tryed to change frequency (example A-B 2.3Ghz and B-C 2.5Ghz), 10/5Mhz bands, A-B only 802.11b and B-C only 802.11G bands, lowed TX power, shortest pigtails, shields on WiFi cards - all doesn't affect to degradation of A-B link

is there a question in this post ?

is there a question in this post ?

Howto solve problem with link degradation?

Howto solve problem with link degradation?

Don't run two radios in the same frequency band (2.4GHz) in the same enclosure or on the same board.

In addition to bradg's reply I would suggest adjusting your Data Rates too as those too can play against connection quality not including SNR & in-band RF interference.

Here is statistic from side A to B

interface wireless monitor wlan1
status: connected-to-ess
band: 2.4ghz-g
frequency: 2474MHz
tx-rate: "48Mbps"
rx-rate: "48Mbps"
ssid:
bssid:
radio-name:
signal-strength: -66dBm
tx-signal-strength: -64dBm
noise-floor: -100dBm
signal-to-noise: 34dB
tx-ccq: 88%
rx-ccq: 74%
p-throughput: 19757
overall-tx-ccq: 88%
authenticated-clients: 1
wds-link: no
nstreme: yes
polling: yes
csma-disabled: yes
framing-mode: exact-size
framing-limit: 3999
routeros-version: "3.22"
last-ip: 10.0.2.2
802.1x-port-enabled: yes
compression: no
current-tx-powers: 1Mbps:19(19),2Mbps:19(19),5.5Mbps:19(19),
11Mbps:19(19),6Mbps:19(19),9Mbps:19(19),
12Mbps:18(18),18Mbps:16(16),24Mbps:14(14),
36Mbps:12(12),48Mbps:10(10),54Mbps:8(8)
current-ofdm-errors: 668
current-cck-errors: 61


here is statistic from side B to A

interface wireless monitor wlan1
status: running-ap
band: 2.4ghz-g
frequency: 2474MHz
noise-floor: -102dBm
overall-tx-ccq: 70%
registered-clients: 1
authenticated-clients: 1
nstreme: yes
polling: yes
csma-disabled: yes
current-tx-powers: 1Mbps:19(19),2Mbps:19(19),5.5Mbps:18(18),
11Mbps:18(18),6Mbps:18(18),9Mbps:18(18),
12Mbps:18(18),18Mbps:16(16),24Mbps:12(12),
36Mbps:10(10),48Mbps:8(8),54Mbps:6(6)
current-ofdm-errors: 388
current-cck-errors: 10



What is "current-ofdm-errors" and "current-cck-errors" ?

What is "current-ofdm-errors" and "current-cck-errors" ?

Basically, CCK errors = 802.11b mode data rate errors, OFDM errors = 802.11g mode data rate errors

Reducing the allowable data rates in both b and g mode may help your situation some, but the card proximity issues can only be fixed by increasing the distance between them.

What is "current-ofdm-errors" and "current-cck-errors" ?

Basically, CCK errors = 802.11b mode data rate errors, OFDM errors = 802.11g mode data rate errors

Reducing the allowable data rates in both b and g mode may help your situation some, but the card proximity issues can only be fixed by increasing the distance between them.

I tryed to reduce data rate and tryed to set second card to another PC - nothing helps

you may try to use different channels one 5800 and one 5600 or something like this; between the channels U must have more that 150 Mhz difference.

Bets Regards Remus