Low Tx power levels on Cisco 3702i AP

[Brett Verney]

I was wondering why the available Tx power levels on the Cisco 3702i AP is so low when assigned a channel in the UNII-1 band?

'show ap config 802.11a <ap_name>'

Tx Power
Num Of Supported Power Levels ............. 3
Tx Power Level 1 .......................... 9 dBm
Tx Power Level 2 .......................... 6 dBm
Tx Power Level 3 .......................... 3 dBm
Tx Power Configuration .................... AUTOMATIC
Current Tx Power Level .................... 1
Tx Power Assigned By ...................... DTPC

Phy OFDM parameters
Configuration ............................. AUTOMATIC
Current Channel ........................... 36
Channel Assigned By ....................... DCA
Extension Channel ......................... NONE
Channel Width.............................. 20 Mhz

9dBm is not enough when trying to match client and AP Tx power, or when trying to maximize client SNR to acheive high MCS rates. The Cisco 3702i AP allows for 17dBm in my regulatory domain (Australia) for the UNII-1 band. In fact the maximum EIRP for the same band is 200mW (23dBm). With an antenna gain of +4dBi on the Cisco 3702i AP, I get an EIRP of around 20mW.

Am I missing something?

-Brett

[Philip D'Ath]

Any chance this is a universal AP, and has not been primed?

Definitely got the right country code configured on the controller?

[Brett Verney]

Hi Philip,

Definitely only running a single Country code (Australia).

(Cisco Controller) >show country

Configured Country............................. AU - Australia
Configured Country Codes
AU - Australia................................. 802.11a Indoor,Outdoor / 802.11b / 802.11g

Too many APs to show... But are all AIR-CAP3702I-Z-K9 models. I will log this one with TAC if no one knows!

-Brett

[Devaiah N K]

Hi All,

Here are my 5 cents for this issue!!!

This is the default behaviour for these access points operating on UNII-1 in this region. They cannot be powered to transmit beyond 16 dBm.

Along with various parts in the America region, Aus, NZ, parts of Oceania and various parts of Asia follow FCC as their regulatory domain.

Even though all these countries have their local governing regulatory body, ACMA for Australia, they are supposed to honour the main regulations of FCC.

Under FCC, transmitters operating in UNII-1 are allowed to transmit 16dBm, while their max EIRP is 160 mW. ACMA states that max EIRP allowed on these channels is 200 mW (FCC supersedes this decision).

Below are some supporting screenshots and excerpts to support this forum.

https://www.legislation.gov.au/Details/F2015L01438

http://www.air802.com/fcc-rules-and-regulations.html

I hope this clarifies this behaviour of low txPower in UNII-1 band. 

I must emphasise that it is sometimes tough to justify the exact TxPower values that we see on AP's, I have also seen AP's with 4dBi antenna gain limiting itself to 14 dBm in this band, this is because the access point also takes the antenna gain into consideration and alters its max transmit power levels.

--Devaiah N K

[Rasika Nayanajith]

Hi DNK,

Agree with your points.

For me, real issue was the bug ID listed. Due to that most of the AP in UNII-1 & UNII-2 does not go beyond 8 dBm which causing coverage issues.

Here is a snapshot to represent problem

With 8.1.131.0(affected code)

AP Name               Channel    TxPower       Allowed Power Levels   

----------------------- ---------- ------------- ------------------------

AP05-L2APT62         *(36,40)   *1/3 ( 8 dBm) [8/5/2/2/2/2/2/2]

AP04-L3APT59         *(36,40)   *1/3 ( 8 dBm) [8/5/2/2/2/2/2/2]

AP06-L3APT26         *(40,36)   *1/3 ( 8 dBm) [8/5/2/2/2/2/2/2]

AP08-L1APT08         *(40,36)   *1/3 ( 8 dBm) [8/5/2/2/2/2/2/2]

AP03-L2APT32         *(48,44)   *1/3 ( 8 dBm) [8/5/2/2/2/2/2/2]

With 8.1.131.18 (bug fix code)

AP Name               Channel    TxPower       Allowed Power Levels   

-------------------- ---------- ------------- ------------------------

AP05-L2APT62         *(36,40)   *1/5 (15 dBm) [15/12/9/6/3/3/3/3]

AP04-L3APT59         *(52,56)   *1/5 (16 dBm) [16/13/10/7/4/4/4/4]

AP06-L3APT26         *(40,36)   *1/5 (15 dBm) [15/12/9/6/3/3/3/3]

AP08-L1APT08         *(52,56)   *1/6 (16 dBm) [16/13/10/7/4/1/1/1]

AP03-L2APT32         *(48,44)   *1/5 (15 dBm) [15/12/9/6/3/3/3/3]

HTH

Rasika

[Devaiah N K]

Hi Rasika, 

I completely agree with you on this bug. You have provided the resolution for this bug too :).Thanks for that again.

In my previous response, I missed to acknowledge the impact of this bug before clarifying the 2nd part of the question highlighted by Brett.

Please note that my answer was only to this part of the question as the discussion around bug was in progress.

" The Cisco 3702i AP allows for 17dBm in my regulatory domain (Australia) for the UNII-1 band. In fact the maximum EIRP for the same band is 200mW (23dBm). With an antenna gain of +4dBi on the Cisco 3702i AP, I get an EIRP of around 20mW.

Am I missing something?"

Cheers,

Devaiah NK

[Howard Chen]

Does the latest firmware (8.3.102.0 / 8.2.121.0 ) fix the bug?

Our customers don't want to upgrade to a special firmware version.

[Rasika Nayanajith]

8.2.121.0 should have the fix. When I asked this from Javier, he confirmed. See below thread

https://supportforums.cisco.com/discussion/13059961/82mr2-beta-availability

Unfortunately it is not listed in the 8.2.121.0 release noteshttp://www.cisco.com/c/en/us/td/docs/wireless/controller/release/notes/crn82mr2.html

I would confirm again with TAC as it is not listed in release notes.

HTH

Rasika

[Howard Chen]

Hi Rasika,

Thanks a lot for your reply.

I reckon the bug should be fixed from 8.2.121.0, since the firmware version 15.3(3)JC3 is the known fixed release, and from the matrix, we can find that the access point IOS version 15.3(3)JC3 is used for firmware version 8.2.121.0.

https://bst.cloudapps.cisco.com/bugsearch/bug/CSCux23003

Known Fixed Releases:

(8)

15.3(3)JC3

8.0(120.34)

8.0(134.7)

8.1(131.17)

8.2(100.7)

8.2(113.3)

8.2(50.17)

8.3(15.79)

http://www.cisco.com/c/en/us/td/docs/wireless/compatibility/matrix/compatibility-matrix.html

Cisco WLC Release	Access Point IOS Release
8.2.121.0	15.3(3)JC3

[Rasika Nayanajith]

I noticed the same issue, would like to know the exact reason. See below

(WLC) >show advanced 802.11a txpower

Leader Automatic Transmit Power Assignment
 Transmit Power Assignment Mode................. AUTO
 Transmit Power Update Interval................. 600 seconds
 Transmit Power Threshold....................... -70 dBm
 Transmit Power Neighbor Count.................. 3 APs
 Min Transmit Power............................. 8 dBm
 Max Transmit Power............................. 17 dBm
 Update Contribution
 Noise........................................ Enable
 Interference................................. Enable
 Load......................................... Disable
 Device Aware................................. Disable
 Transmit Power Assignment Leader............... WC01 (10.x.x.x) 
 Last Run....................................... 437 seconds ago
 Last Run Time.................................. 0 seconds
 TPC Mode....................................... Version 1
 TPCv2 Target RSSI.............................. -67 dBm
 TPCv2 VoWLAN Guide RSSI........................ -67.0 dBm
 TPCv2 SOP...................................... -85.0 dBm
 TPCv2 Default Client Ant Gain.................. 0.0 dBi
 TPCv2 Path Loss Decay Factor................... 3.6
 TPCv2 Search Intensity......................... 10 Iterations

AP Name Channel TxPower Allowed Power Levels 
-------------- ------------ ------------- ------------------------
AP05-L2APT6 *(36,40) *1/3 ( 8 dBm) [8/5/2/2/2/2/2/2]
AP08-L2APT1 *(149,153) *5/8 (11 dBm) [23/20/17/14/11/8/5/2]
AP04-L3APT5 *(36,40) *1/3 ( 8 dBm) [8/5/2/2/2/2/2/2]
AP04-L2APT1 *(161,157) *3/8 (17 dBm) [23/20/17/14/11/8/5/2]
AP02-L3APT5 *(52,56) *1/5 (16 dBm) [16/13/10/7/4/4/4/4]
AP06-L3APT2 *(40,36) *1/3 ( 8 dBm) [8/5/2/2/2/2/2/2]
AP01-L1APT0 *(149,153) *3/8 (17 dBm) [23/20/17/14/11/8/5/2]
AP01-L2APT5 *(149,153) *3/8 (17 dBm) [23/20/17/14/11/8/5/2]
AP08-L1APT0 *(40,36) *1/3 ( 8 dBm) [8/5/2/2/2/2/2/2]
AP03-L2APT3 *(48,44) *1/3 ( 8 dBm) [8/5/2/2/2/2/2/2]
AP05-L1APT0 *(149,153) *3/8 (17 dBm) [23/20/17/14/11/8/5/2]
AP05-L3APT3 *(40,36) *1/3 ( 8 dBm) [8/5/2/2/2/2/2/2]
AP01-L3APT2 *(40,36) *1/3 ( 8 dBm) [8/5/2/2/2/2/2/2]
AP08-L1APT0 *(64,60) *1/6 (16 dBm) [16/13/10/7/4/1/1/1]
AP04-L3APT5 *(48,44) *1/3 ( 8 dBm) [8/5/2/2/2/2/2/2]
AP06-L1APT0 *(44,48) *1/3 ( 9 dBm) [9/6/3/3/3/3/3/3]
AP03-L3APT1 *(64,60) *1/6 (16 dBm) [16/13/10/7/4/1/1/1]
AP02-L3APT4 *(40,36) *1/3 ( 8 dBm) [8/5/2/2/2/2/2/2]

(WLC) >show ap summary
AP Name Slots AP Model 
--------- ----- --------------------
AP05-L2APT6 2 AIR-CAP3702I-Z-K9 
AP08-L2APT1 2 AIR-CAP3702I-Z-K9
AP04-L3APT5 2 AIR-CAP3702I-Z-K9 
AP04-L2APT1 2 AIR-CAP3702I-Z-K9 
AP02-L3APT5 2 AIR-CAP3702I-Z-K9 
AP06-L3APT2 2 AIR-CAP3702I-Z-K9
AP01-L1APT0 2 AIR-CAP3702I-Z-K9
AP01-L2APT5 2 AIR-CAP3702I-Z-K9 
AP08-L1APT0 2 AIR-CAP3702I-Z-K9
AP03-L2APT3 2 AIR-CAP3702I-Z-K9 
AP05-L1APT0 2 AIR-CAP3702I-Z-K9 
AP05-L3APT3 2 AIR-CAP3702I-Z-K9 
AP01-L3APT2 2 AIR-CAP3702I-Z-K9
AP08-L1APT0 2 AIR-CAP3702I-Z-K9 
AP04-L3APT5 2 AIR-CAP3702I-Z-K9

HTH

Rasika

[Brett Verney · Accepted solution]

Turns out it is a regulatory domain bug for WLCs running 8.0.x code. Resolved in 8.1(131.17), 8.2(100.7) and 8.3(15.79).

Symptom:
AP in -Z & -T domain provide 8 dbm TX Power only as Max Power when operating on channels 36,40,44,48,52,56,60,64

Conditions:
3700, 2600, 2700, 3600,1700 series APs, in -Z and -T regulatory domains.

https://bst.cloudapps.cisco.com/bugsearch/bug/CSCux23003

Time to upgrade!

-Brett

[Rasika Nayanajith · Accepted solution]

Thanks for the update

None of those code seems like to be public releases. Which code are you planning to go with ?

Rasika

[Philip D'Ath · Accepted solution]

Personally, I'm going to wait for the next public release that has the bug fixed integrated into it and properly regression tested.  However if anyone is desperate they can open a case with Cisco TAC to get it.

[Brett Verney]

Ahh I didn't take any notice of the exact versions of the code. I have a client who wants me to upgrade to 8.1.(131.0) in the next few weeks, so we'll see what happens.

I think I'll log a TAC to get the official word. According to the Bug ID, only two cases have been logged so far.

-Brett

[Rasika Nayanajith]

Ahh I didn't take any notice of the exact versions of the code. I have a client who wants me to upgrade to 8.1.(131.0) in the next few weeks, so we'll see what happens.

I am running this code and having the same issue. Actually output provided earlier in this thread from a WLC running this image. So do not keep any hope with that code.

I think TAC should give you the specific image (8.0.x or 8.1.x or 8.2.x train). I have to get a code from TAC for this as it is very serious issue.

HTH

Rasika