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Re: [USRP-users] Toggle between 2 transmit antennas

Marcus D. Leech

Fri, Jul 13, 2018 1:59 AM

On 07/12/2018 06:21 PM, Ayaz Mahmud wrote:

Hello Markus,

Thanks for suggestion. Yes, I have two channels.

I don’t know if I am doing this correct, here what I understood from
your suggestion:

1^st Channel : Vector source (1,0)

2^nd Channel : Vector source (0,1)

So when 1^st channel will transmit a data while 2^nd channel will be
NULL at simultaneous time.

Now at receiver side, I have a TAG DEBUG, connected with OFDM channel
estimation (to get the CSI). Therefore I was hoping to receive 2 CSI
values (from each antenna). But I am getting only 1 (64 subcarrier).

This was the reason I was trying to do a enable/disable of antenna, so
that I can receive the CSI from each transmit antenna separately.

Please let me know if I am doing it correct, or you have a suggestion
for this.

Thanks

Ayaz

I think we need a better overall description of what you're doing, and
since this is about 80% Gnu Radio related, the discuss-gnuradio mailing list
may be a better venue, but I can't tell from your very-brief
description if it is or not.

On 07/12/2018 06:21 PM, Ayaz Mahmud wrote: > > Hello Markus, > > Thanks for suggestion. Yes, I have two channels. > > I don’t know if I am doing this correct, here what I understood from > your suggestion: > > 1^st Channel : Vector source (1,0) > > 2^nd Channel : Vector source (0,1) > > So when 1^st channel will transmit a data while 2^nd channel will be > NULL at simultaneous time. > > Now at receiver side, I have a TAG DEBUG, connected with OFDM channel > estimation (to get the CSI). Therefore I was hoping to receive 2 CSI > values (from each antenna). But I am getting only 1 (64 subcarrier). > > This was the reason I was trying to do a enable/disable of antenna, so > that I can receive the CSI from each transmit antenna separately. > > Please let me know if I am doing it correct, or you have a suggestion > for this. > > Thanks > > Ayaz > > I think we need a better overall description of what you're doing, and since this is about 80% Gnu Radio related, the discuss-gnuradio mailing list may be a better venue, but I can't tell from your very-brief description if it is or not.

Ayaz Mahmud

Fri, Jul 13, 2018 2:56 AM

Hi Marcus,

Thanks for replying.

So my ultimate goal is to get the CSI (Channel State Information) between 2 Tx antenna (1st B210) and 2 Rx antenna(2nd B210). So that each antenna at Rx will have 2 CSI measurement.

Attached is my picture of the flowgraph.

To build this scenario, I have used the “Tx_OFDM” and “Rx_OFDM” from Gnuradio examples. I am using a text file to be transmitted. Exact same blocks are used twice (to make 2 channels) and fed into an USRP sink.

At receiver side USRP source is used with other blocks to decode. & Tag Debug box is added to read the CSI at console.

This setup work fine. But I am seeing only 1 CSI measurement at each Rx antenna. This is because I am transmitting the same signal at same time from 2 Tx antennas, so it is arriving at the same time at Rx thereby the CSI is accumulated ( I am guessing) !

I have tried to add a delay in one tx antenna, but the result was same.
Now I am trying to transmit from 1 antenna at a time. So 1st Tx antenna will be received at both Rx antenna thereby give 2 CSI measurement. It will then stop transmitting and the 2nd Tx antenna will start transmitting which will also give CSI from 2 Rx antenna.

So I wanted to know if this enabling/disabling of antenna (TX/RX) port is possible or not.
If it is not possible, what are the possible workarounds?

Let me know how should I proceed in this case.

Thanks,
Ayaz

From: Marcus D. Leechmailto:mleech@ripnet.com
Sent: Thursday, July 12, 2018 8:00 PM
To: Ayaz Mahmudmailto:ayazmahmud@hotmail.com; usrp-users@lists.ettus.com mailto:usrp-users@lists.ettus.com
Subject: Re: [USRP-users] Toggle between 2 transmit antennas

On 07/12/2018 06:21 PM, Ayaz Mahmud wrote:
Hello Markus,

Thanks for suggestion. Yes, I have two channels.

I don’t know if I am doing this correct, here what I understood from your suggestion:

1st Channel : Vector source (1,0)
2nd Channel : Vector source (0,1)
So when 1st channel will transmit a data while 2nd channel will be NULL at simultaneous time.

Now at receiver side, I have a TAG DEBUG, connected with OFDM channel estimation (to get the CSI). Therefore I was hoping to receive 2 CSI values (from each antenna). But I am getting only 1 (64 subcarrier).

This was the reason I was trying to do a enable/disable of antenna, so that I can receive the CSI from each transmit antenna separately.

Please let me know if I am doing it correct, or you have a suggestion for this.

Thanks
Ayaz

I think we need a better overall description of what you're doing, and since this is about 80% Gnu Radio related, the discuss-gnuradio mailing list
may be a better venue, but I can't tell from your very-brief description if it is or not.

Hi Marcus, Thanks for replying. So my ultimate goal is to get the CSI (Channel State Information) between 2 Tx antenna (1st B210) and 2 Rx antenna(2nd B210). So that each antenna at Rx will have 2 CSI measurement. Attached is my picture of the flowgraph. To build this scenario, I have used the “Tx_OFDM” and “Rx_OFDM” from Gnuradio examples. I am using a text file to be transmitted. Exact same blocks are used twice (to make 2 channels) and fed into an USRP sink. At receiver side USRP source is used with other blocks to decode. & Tag Debug box is added to read the CSI at console. This setup work fine. But I am seeing only 1 CSI measurement at each Rx antenna. This is because I am transmitting the same signal at same time from 2 Tx antennas, so it is arriving at the same time at Rx thereby the CSI is accumulated ( I am guessing) ! I have tried to add a delay in one tx antenna, but the result was same. Now I am trying to transmit from 1 antenna at a time. So 1st Tx antenna will be received at both Rx antenna thereby give 2 CSI measurement. It will then stop transmitting and the 2nd Tx antenna will start transmitting which will also give CSI from 2 Rx antenna. So I wanted to know if this enabling/disabling of antenna (TX/RX) port is possible or not. If it is not possible, what are the possible workarounds? Let me know how should I proceed in this case. Thanks, Ayaz From: Marcus D. Leech<mailto:mleech@ripnet.com> Sent: Thursday, July 12, 2018 8:00 PM To: Ayaz Mahmud<mailto:ayazmahmud@hotmail.com>; usrp-users@lists.ettus.com<mailto:usrp-users@lists.ettus.com> Subject: Re: [USRP-users] Toggle between 2 transmit antennas On 07/12/2018 06:21 PM, Ayaz Mahmud wrote: Hello Markus, Thanks for suggestion. Yes, I have two channels. I don’t know if I am doing this correct, here what I understood from your suggestion: 1st Channel : Vector source (1,0) 2nd Channel : Vector source (0,1) So when 1st channel will transmit a data while 2nd channel will be NULL at simultaneous time. Now at receiver side, I have a TAG DEBUG, connected with OFDM channel estimation (to get the CSI). Therefore I was hoping to receive 2 CSI values (from each antenna). But I am getting only 1 (64 subcarrier). This was the reason I was trying to do a enable/disable of antenna, so that I can receive the CSI from each transmit antenna separately. Please let me know if I am doing it correct, or you have a suggestion for this. Thanks Ayaz I think we need a better overall description of what you're doing, and since this is about 80% Gnu Radio related, the discuss-gnuradio mailing list may be a better venue, but I can't tell from your very-brief description if it is or not.