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WL1837MOD: Problem with MIMO on 2.4GHz

Part Number: WL1837MOD

Hi,

I have some problems with enable MIMO on WL1837MOD.
Following some instructions it seems that for such configuration only "numbers_of_assembled_antennas_2.4" should be set to 2 and it is. 

Debug session shows that AP START_ROLE is executed with proper values. (visible also in FW logs)

With some default radio parameters we tried to verify MIMO using iperf.
On ANT2 emission is visible but on ANT1 there is very low siglan strength.

It looks like interference from ANT2 which seems to be proper diagnosis since we are not able to archive more than MCS7.
It doesn't matter how much traffic we want to transport, it is not impossible to jump into eg MCS11 which means that MIMO doesn't work

 

Screenshots from spectrum analyzer

ANT2

ANT1

TI Firmware logs

35 1 0 2017-07-19 08:42:38.475 0 0 roles.c:1427 1 Roles_ConfigureStartedRole Role 4, supportedRates 0xfffffff, Bandwidth NLCP_CHAN_NO_HT, io_method MIMO

117 1 0 2017-07-19 08:42:38.522 0 0 mac_phy_api.c:713 1 BalconyRadioTune_new API_SET_TX_POWER: Start Role first time set tx power, bitmap 0x3, index 0 rfset 0 setTxPwr_desiredPower 20000
118 1 0 2017-07-19 08:42:38.522 0 0 mac_phy_api.c:713 1 BalconyRadioTune_new API_SET_TX_POWER: Start Role first time set tx power, bitmap 0x2, index 1 rfset 0 setTxPwr_desiredPower 10000

glog_2017_07_19_084254_channel1.txt

glog_2017_07_19_084841_channel6 .txt

Is there something more to force MIMO (2 antennas) on TI module ?

Is there something more that need to be enabled to see the same signal level on second antenna ? 

BR //Marcin

  • Hi Marcin ,
    - Are you starting AP role on WiLink8 ? WL1837MOD ?
    - Are you working on Linux ?
    - If yes, can you please run following commands and check MCS rates ? "iw phy"
    - If possible , can you capture sniffer trace and share beacon IEs
    - Pls consult www.ti.com/.../swra489.pdf and make sure wl18xx.ht.mode=0

    Thanks
    Saurabh
  • Hi,

    This is custom board with TI wl18xx chip from U-Blox -> EVK-ODIN-W2 (EVK ODIN W260)
    So board with starts as AP (CMD to Firmware - START_ROLE) with the same parameters like linux reference board.
    Supported rates 0xfffffff, 2.4GHz on channel 1, channel type 1 (20HT) . All of these is visible on TI Firmware DBG logs. (attached in previous post)

    To this AP I conneced 2 STA on Linux laptops to run iperf.
    During test with 80Mbit/s I got ~30MBit/s and at the same time I verified MCS which shows MCS7 - 65MBit

    This mean that there is no MIMO.

    IE contains HT elements with 2 spatial streams - different tools on windows and android shows that there are 135MBps but I based on IE in the air (not real troughput).

    Odin_AP_11channel_N_MIMO.txt
    
    
    pM<+��������Linux 3.13.0-119-generic-Dumpcap 1.12.1 (Git Rev Unknown from unknown)pHwlan0	Linux 3.13.0-119-genericH��SWtS���.H�	���������x�/	�x�/	���%!d�UBXWifi��$20H`l-�����L3���=����P��'�BCab2/���SRU���.H�	���������x�/	�x�/	����"d�UBXWifi��$20H`l-�����L3���=����P��'�BCab2/���S��U���.H�	��P:��p9D�x�/	�x�/	����#d�UBXWifi��$20H`l-���=�����L3����P��'�BCab2/�<�S��U�.H�	���x�/	�<\�Sv�V�;;.H�	���:x�/	���p9D�x�/	�I�	\<�S��V�.H�	����x�/	�<P�Sw�V�00.H�	���<��p9D�x�/	�x�/	���P<�S��V�.H�	���x�/	�<��S��V���.H�	��:x�/	���p9D�x�/	�I!
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    --���@@k�	�P��<�S��V�.H�	���x�/	�<��S��V���.H�	��<��p9D�x�/	�x�/	������2���l-��=���P��'�BCab2/�<�S��V�.H�	���x�/	�<L�S�
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     please change *.txt to *.pcapng

    wl18xx.ht.mode=0 is a default value which is this case is not important since this is not linux host.
    and as far as I know this parameter is not written to FW memory (like other rg radio parameters) but It is used
    to properly set supported rates and at the end start AP role with correct settings.

    As I remember the same result I had on linux AM3xx reference board.

    Do you see something strange in FW logs ?

    Thanks //Marcin

  • Hi,

    @UPDATE:

    iw wlan0 station dump on AM335x

    Station 4c:49:e3:1b:a5:57 (on wlan0)

           inactive time:  350 ms

           rx bytes:       53726

           rx packets:     412

           tx bytes:       43345407

           tx packets:     28353

           tx retries:     0

           tx failed:      5

           signal:         0 dBm

           signal avg:     -97 dBm

           tx bitrate:     1.0 MBit/s

           rx bitrate:     65.0 MBit/s MCS 7

           authorized:     yes

           authenticated:  yes

           preamble:       long

           WMM/WME:        yes

           MFP:            no

           TDLS peer:      no

           connected time: 518 seconds

    Station 98:f1:70:39:44:88 (on wlan0)

           inactive time:  370 ms

           rx bytes:       84238113

           rx packets:     55243

           tx bytes:       19221

           tx packets:     45

           tx retries:     0

           tx failed:      0

           signal:         0 dBm

           signal avg:     -74 dBm

           tx bitrate:     1.0 MBit/s

           rx bitrate:     65.0 MBit/s MCS 7

           authorized:     yes

           authenticated:  yes

           preamble:       short

           WMM/WME:        yes

           MFP:            no

           TDLS peer:      no

           connected time: 285 seconds

    and logs from TI FW (AM335x):

    am335x_mimo.txt

    BR // Marcin

  • Hello,

    Is there someone from TI who are able to analyze logs from FW and give some support why MIMO doesn't work ?

    I don't know whether I have right or not but I found that MIMO support for wl18xx driver doesn't support MCS more then 7.
    Does it mean that there are no HT rates in MIMO ?

    Are there any requirements that need to be fullfiled to make this feature to work?

    Here is new version of TI FW logs: ti.txt

    Thanks //Marcin

  • Marcin ,
    We will let you now if we have any comments on firmware logs . This forum is only for WL18xxMOD Linux support - non Linux OS based system support is via 3rd party. Are you able to do same testing on AM335x Linux and let us know the results.
    WiLink8 does support MCS0-MCS15 . I reviewed the sniffer logs and MIMO seems to be enabled as per beacon HT capability IE . But in Association Response I see only MCS0-MCS7 enabled.
    Run configure-device.sh to make sure wl18xx configuration file is set properly for WL1837MOD. processors.wiki.ti.com/.../WiLink8_WLAN_Demo:_Linux

    Thanks
    Saurabh
  • Hello,

    Thanks for clarification.

    After corrections and some retests I was able to see MIMO functionality on AM335x board.

    I saw that on 2.4GHz in radiotap header MCS index is 15 and Data rate is 130Mb/s.

    iperf test gives ~90Mb/s

    --- > I suppose that problem was caused by week signal related to some radio parameters.

    END.

    Back to my board/case.

    I enabled full debug mask in TI FW logger:

    e2e.ti.com/.../mimo_5F00_debug_5F00_fw.xlsx

    isMimoDevice=1

    Role 4, supportedRates 0x3fffffff, Bandwidth NLCP_CHAN_HT20, io_method MIMO

    but even with these prints MCS Rate is 7 and Data Rate is 65Mb/s

    Thanks for support

    // Marcin