[srslte-users] PDCCH MISS being too High with PDSCH transmission

Tue Feb 13 11:16:19 UTC 2018

hi Justin,

As we do not have commercial cell, we are not able to run the suggested test.

We have few observations with respect to high PDCCH-Miss%

pdsch_enodeb is using constant CFI (cfi=2) in all subframes. However, in the UE logs we see different CFI values:

[INFO]: Decoded CFI=3 with correlation 2.28, sf_idx=2
[INFO]: Searching DL C-RNTI Format1A in 16 ue locations
[INFO]: Searching DL C-RNTI Format1  in 16 ue locations
[INFO]: Searching DL C-RNTI in 6 ue locations, format 1A
[INFO]: Decoded CFI=3 with correlation 5.65, sf_idx=3
[INFO]: Searching DL C-RNTI Format1A in 16 ue locations
[INFO]: Searching DL C-RNTI Format1  in 16 ue locations
[INFO]: Searching DL C-RNTI in 6 ue locations, format 1A
O[INFO]: Decoded CFI=1 with correlation 5.58, sf_idx=4
[INFO]: Searching DL C-RNTI Format1A in 12 ue locations
[INFO]: Searching DL C-RNTI Format1  in 12 ue locations
[INFO]: PSS: id=0, peak_pos=397, peak_value=14.735041
[INFO]: PSS-CFO: filter=yes, estimated=0.738486, mean=0.003154
[INFO]: Warning: Expected SF idx 5 but got 0! (0 frames)

Can you please provide us some pointers on why UE is not able to decode PCFICH correctly.

Thanks.

Best Regards,

Nazia

________________________________
From: Justin Tallon <justin.tallon at softwareradiosystems.com>
Sent: Friday, February 9, 2018 10:39 PM
To: Sandeep Sarma -ERS, HCL Tech
Cc: srslte-users at lists.softwareradiosystems.com; Sriram P; Jagadish Rajanna; Nazia Shaik
Subject: Re: [srslte-users] PDCCH MISS being too High with PDSCH transmission

Hey Sandeep,

Sorry I may not have been clear, I meant for you to run

./pdsch_ue -f 806000000 or ./pdsch_ue -f 816000000 with an antenna and try receive a commercial cell

let me know what this looks like.

Thanks,

Justin

____
Justin Tallon Ph.D.

Software Radio Systems (SRS)
http://www.softwareradiosystems.com<https://apac01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.softwareradiosystems.com%2F&data=02%7C01%7Cnazia.shaik%40hcl.com%7C171a3a7d2dba4fd76d3908d56fdfe129%7Cdd85efd06a9c4fee843ed525fa4be3ca%7C0%7C0%7C636537929726030776&sdata=q8IAR%2FEncSkNKXMMF8z7jjKkSaCWhQw9H1btHeOSyGI%3D&reserved=0>

+353-86-067-0753 | justin.tallon at softwareradiosystems.com<mailto:justin.tallon at softwareradiosystems.com>

On Fri, Feb 9, 2018 at 4:56 PM, Sandeep Sarma -ERS, HCL Tech <sandeep-s at hcl.com<mailto:sandeep-s at hcl.com>> wrote:

Hello Justin,

Thanks a lot for the quick response.

By default the mbsfn_subframe - sf_type is set to "true" on initialization (pdsch_enodeb).

I have set it to false and used the frequencies suggested by you and the behaviour is as below:

I could see some improvement where the PDCCH-Miss now shows up to 80%, a decrease ~20% from previous tests.

Just for information, what should be the ideal PDCCH decode failure rate in these radio conditions and what power levels should be set?

Again, appreciate your help.

BR,
Sandeep

________________________________
From: Justin Tallon <justin.tallon at softwareradiosystems.com<mailto:justin.tallon at softwareradiosystems.com>>
Sent: Friday, February 9, 2018 9:41:19 PM
To: Sandeep Sarma -ERS, HCL Tech
Cc: srslte-users at lists.softwareradiosystems.com<mailto:srslte-users at lists.softwareradiosystems.com>; Sriram P; Jagadish Rajanna; Nazia Shaik
Subject: Re: [srslte-users] PDCCH MISS being too High with PDSCH transmission

Hey Sandeep!

I see in the logs "Sandy setting mbsfn_subframe to true"

Are setting this value to True?

Can you try to receive a commercial cell with the pdsch_ue to see if you can see a reasonable signal?

try 806000000 or 816000000.

Thanks,
Justin

____
Justin Tallon Ph.D.

Software Radio Systems (SRS)
http://www.softwareradiosystems.com<https://apac01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.softwareradiosystems.com%2F&data=02%7C01%7Csandeep-s%40hcl.com%7Cf8fb5838bccc4f5a6c6908d56fd7cf4c%7Cdd85efd06a9c4fee843ed525fa4be3ca%7C0%7C0%7C636537895051230445&sdata=PCuP8RCLXrDpdQ%2B5vi%2Bj%2F%2FcQ1ipel%2BjatupFHBLDFm4%3D&reserved=0>

+353-86-067-0753<tel:+353%2086%20067%200753> | justin.tallon at softwareradiosystems.com<mailto:justin.tallon at softwareradiosystems.com>

On Fri, Feb 9, 2018 at 2:32 PM, Sandeep Sarma -ERS, HCL Tech <sandeep-s at hcl.com<mailto:sandeep-s at hcl.com>> wrote:

Hello srsLTE Users,

I have a test setup with 2 USRP B210 SDRs and a wired RF cable between Tx and Rx antenna ports.

While I run the pdsch_enb and pdsch_ue example scripts, I see a lot of DCI miss through PDCCH-Miss % being around 90-98%.

Tx_gain, clock rate is default and I have a 30DB attenuator at the pdsch_ue (USRP Rrx side).

Below are the commands and verbose logs are attached.

pdsch_enb:

./pdsch_enodeb -f 5200000000 -m 11 -p 50 -v -n 5000

pdsch_ue:

./pdsch_ue -f 5200000000 -r 1234 -v

I've also tried with increasing the tx_gain and mcs but situation is same.

Appreciate if I can hear from anyone on how to improve the decoding at the receiving end. It would help tremendously.

BR,

Sandeep

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