Fwd: UmTRX Digest, Vol 9, Issue 16

Alexander Chemeris alexander.chemeris at gmail.com
Wed Mar 20 12:57:26 UTC 2013


This is pure host side UHD update (UHD driver as you call it).

Sent from my Android device.

--
Regards,
Alexander Chemeris
CEO, Fairwaves LLC
http://fairwaves.ru
20.03.2013 16:47 пользователь "Craig Reading" <craig.reading1 at gmail.com>
написал:

> Alexander
>
> Is this a firmware update or UHD driver update? If firmware would it be
> possible to upload an image?
>
> Regards
> Craig
>
> Begin forwarded message:
>
> *From:* umtrx-request at lists.osmocom.org
> *Date:* 19 March 2013 20:36:34 GMT
> *To:* umtrx at lists.osmocom.org
> *Subject:* *UmTRX Digest, Vol 9, Issue 16*
> *Reply-To:* umtrx at lists.osmocom.org
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> Today's Topics:
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>   1. Tx signal quality improvement (Alexander Chemeris)
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> ----------------------------------------------------------------------
>
> Message: 1
> Date: Wed, 20 Mar 2013 00:33:29 +0400
> From: Alexander Chemeris <alexander.chemeris at gmail.com>
> To: umtrx <umtrx at lists.osmocom.org>
> Subject: Tx signal quality improvement
> Message-ID:
>    <CABmJbFV4C0_WBCBuj61U8_2bQjm9x049ciB0yYQDjJdoHxiNGg at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Hi all,
>
> I've found an issue with out Tx configuration of LMS which led to
> constant phase rotation of the transmitted signal. After fixing this
> issue I get quite better signal quality on transmit side. I advise
> everyone to update to the most recent UHD on the host side to benefit
> from this improvement.
>
> The reason for the issue was that we used the wrong polarity of TX_
> IQ_SEL. As a result, LMS transmitted I from one sample and Q from the
> other sample. One of the visible results was a huge I/Q imbalance on
> Tx which made it impossible to use multi-ARFCN configurations. We've
> solved this issue in software by setting tx_fsinc_polarity and
> tx_interleave_mode to proper values in LMS configuration registers.
>
> Attached screenshots from our E4406A shows signal quality transmitted
> by OpenBTS we could have now. Tests are performed with "laurent"
> branch of Fairwaves, compiled with SPS (samples per symbol) set to 4.
> DC offset and I/Q imbalance are calibrated.
>
> screen2.gif, screen3.gif - constellation and phase error when LO
> leakage is at the center of the signal spectrum, i.e. with no LO
> offset on Tx.
>
> screen4.gif, screen5.gif - constellation and phase error when DC
> offset is when LO leakage is shifted to 300kHz away from the signal
> spectrum center, i.e, with 300kHz LO offset on Tx.
>
> screen6.gif - phase error per symbol plots for the same settings as
> with screen4.gif and screen5.gif.
>
> When we implement a true GMSK transmitter we should be able to get
> even better phase noise parameters, meaning excellent downlink signal
> quality. But even this values are much better than required by the
> Standard.
>
> --
> Regards,
> Alexander Chemeris.
> CEO, Fairwaves LLC / ??? ???????
> http://fairwaves.ru
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