Re: [Openbts-discuss] Device doesn't see network at all (openbts-uhd + usrp2 + wbx)

[Љубомир С. <lj...@gm...>]

News from me :) When I start kal with 95% gain I get something like this:

./kal -f 940.01e6 -v -g 95
linux; GNU C++ version 4.3.4; Boost_104200; UHD_003.001.001-09cf8eb

-- Opening a USRP2/N-Series device...
-- Current recv frame size: 1472 bytes
-- Current send frame size: 1472 bytes
-- mboard0 is MIMO master

UHD Warning:
    The hardware does not support the requested RX sample rate:
    Target sample rate: 0.270833 MSps
    Actual sample rate: 0.271739 MSps
kal: Calculating clock frequency offset.
Using GSM-900 channel 25 (940.0MHz)
        offset   1: -7661.58
        offset   2: -24499.12
        offset   3: -24431.74
        offset   4: -7659.51
        offset   5: 39077.79
        offset   6: -7624.26
        offset   7: -7647.07
        offset   8: 37708.44
        offset   9: -7662.61
        offset  10: -7681.27
        offset  11: 37858.75
        offset  12: -7635.67
        offset  13: 37938.57
        offset  14: 37830.76
        offset  15: 39156.57
        offset  16: -7651.21
        offset  17: 37794.48
        offset  18: 37984.18
        offset  19: 36736.11
        offset  20: -7546.52
        offset  21: -7521.64
        offset  22: 37936.50
        offset  23: 37790.33
        offset  24: -7606.64
        offset  25: -24500.15
        offset  26: -7573.47
        offset  27: 39492.43
        offset  28: -7551.70
        offset  29: -7491.58
        offset  30: -24460.76
        offset  31: -24429.66
        offset  32: -7535.11
        offset  33: 37981.07
        offset  34: -7605.60
        offset  35: 38243.32

So, how should I interpret this? usrp's internal clock is definitely too
much shifted but in which direction?

And one more thing I'm not sure about: after I know the clock offset, how
can I use it? Is there a way to permanently "tune up" usrp's internal clock?
Or to use this value within OpenBTS itself?

Cheers once again :)
Ljubomir


2011/6/11 Љубомир Самарџић <lj...@gm...>

> While I'm searching for another gigabit ethernet card (or switch) ... :)
>
> Antennas are VERT900, both. So, I'm still not sure whether usrp device is
> really transmitting anything (as I said A and C leds are on).
>
> I have read Open BTS / clocks article (
> https://sourceforge.net/apps/trac/openbts/wiki/OpenBTS/Clocks), so it
> literaly says: "Whatever system the handset sees first will control its
> clock and make it blind to the other."
>
> I'm still stuck with kal (kal-uhd), here is what I tried:
> (local bs is transmitting on 940M)
>
> src/kal -f 940.01e6 -v -D
>
> and I'm getting:
> linux; GNU C++ version 4.3.4; Boost_104200; UHD_003.001.001-09cf8eb
>
> debug: FPGA Master Clock Freq:  100000000
> debug: External Reference    :  No
> debug: RX Subdev Spec        :  B
> debug: Antenna               :  RX2
> debug: Gain                  :  0.450000
> -- Opening a USRP2/N-Series device...
> -- Current recv frame size: 1472 bytes
> -- Current send frame size: 1472 bytes
> -- mboard0 is MIMO master
>
>
> UHD Warning:
>     The hardware does not support the requested RX sample rate:
>     Target sample rate: 0.270833 MSps
>     Actual sample rate: 0.271739 MSps
> kal: Calculating clock frequency offset.
> Using GSM-900 channel 25 (940.0MHz)
> debug: error limit: inf
> debug: error limit: inf
> debug: error limit: inf
> debug: error limit: inf
> ........
>
> Cheers,
> Ljubomir
>
>
> On Sat, Jun 11, 2011 at 5:33 AM, abhinav anand <a.a...@gm...>wrote:
>
>> I have also tested Kal on USRP2 for the non 52Mhz transceiver.
>> It gave pretty accurate results !!!
>>
>> On Fri, Jun 10, 2011 at 2:36 PM, Thomas Tsou <tt...@vt...> wrote:
>>
>>> 2011/6/10 Alexander Chemeris <ale...@gm...>:
>>> > I think Kal is not ported to non 52 MHz configuration and doesn't work
>>> > with USRP2 - that's why you see this error about incorrect frequency.
>>> > Correct me if I'm wrong.
>>>
>>> I did a quick port to UHD - the necessary changes were minimal - when
>>> working with the usrp2 about nine months ago. The usrp2 doesn't have a
>>> reconfigurable clock rate and the sample rate for UHD devices can be
>>> set without specifying decimation. 52MHz is the default so that's what
>>> the usrp2 tries to use.
>>>
>>> http://ttsou.github.com/kalibrate-uhd/
>>>
>>> I can still detect signals, though I'm not entirely sure if and to
>>> what degree the sample rate offset has on accuracy.
>>>
>>>  Thomas
>>>
>>>
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