[srslte-users] srsLTE, control channel (PDCCH) decoding, CRC pass in PDSCH

[Inkyu Bang]

Hi, all.

We are trying to decode all PDCCH messages and corresponding DCI messages
and to get some messages in PDSCH by modifying srsLTE open sources (in real
time).

This kind of work was already done by [1] and [2] ([1] used their own code
and [2] utilized srsLTE).

[1] Swarun Kumar et al. "LTEye: LTE Radio Analytics Made Easy and
Accessible", sigcomm 2014.
[2] Nicola Bui et al. "OWL: a Reliable Online Watcher for LTE Control
Channel Measurements",  ATC (All Things Cellular) 2016.

We run the test for 1 hours recording all RA-RNTI (1~10) recovered from
PDCCH and corresponding RAR message.
The problem we are facing is that majority of the PDSCH of RAR do not pass
CRC.

We have checked the following for sure.
(1) We have good signal quality (Constellation using pdsch_ue example).
(2) Our USRP is close to the base station (We can obtain the location of
eNB using an android application such as "Network Cell Info".).
(3) srsLTE itself is working correctly. When we decode SI (system
information), i.e., PDCCH by SI-RNTI and corresponding PDSCH, we get
correct results.

We use the following setup:
DELL Latitude E5570
Intel Core  i7-6820HQ CPU @ 2.70GHz × 8
Intel HD Graphics 530 (Skylake GT2)
8GB RAM
256 SSD
OS: Ubuntu 16.04 (64bit)
SDR (software-defined radio) device: USRP B210

Thus, we have concluded that our USRP (B210) may not support these several
procedures (decoding several PDCCH and corresponding PDSCH) within 1ms (one
subframe) for real time.

Do you have any idea of this issue?

Thanks
Regards,
Inkyu bang
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