UE failed to attach at 20MHz

Scenario: OAI ENodeB + UE in noS1 mode(lte-softmodem-nos1) Hardware: Both enb and UE use USRP b210 Setting: 20MHz, FDD, LTE Band 7 (2660MHz)

Problem Description: Everything works well when the bandwidth is 5MHz or 10MHz. However, when I modify enb.band7.tm1.usrpb210.conf (N_DL_RB = 100), several problems pop up. I cut the display and lower the log level because the connection still fails due to following:

1. Received RAR preamble (**) doesn't match.

Curiously, this problem randomly appears. Even if I try using -A option, I just cannot find a value to make the system stable.

2. Contention resolution timer expired.

[1;31m[MAC][E][ue_scheduler] Module id 0 Contention resolution timer expired, RA failed

Even if RAR passes, connections usually fails due to the msg4 timeout. I check log and find that eNodeB indeed reply msg4 and get acknowlodge for the msg. Howver, it turns out the frame number (during msg3/4) in UE and eNodeB are different.

3. bad DCI 1/ 1A !!! Sometimes the UE indeed sucessfully attachs, ping between devices still fails. And a lot pdcch errors appear at the UE side.

[PHY][I][check_dci_format1_1a_coherency] bad dci rballoc rballoc 29802256 RIV_max 5049 bad DCI 1 !!!

btw, I am also trying to make the system operating in unlicensed band, i.e. 2.4ghz. I modified the frequency for band 7 in both ./openair2/ENB_APP/enb_config.c and ./targets/RT/USER/lte-ue.c static const eutra_band_t eutra_bands[] = { //{ 7, 2500 * MHz, 2570 * MHz, 2620 * MHz, 2690 * MHz, FDD}, { 7, 2280 * MHz, 2350 * MHz, 2400 * MHz, 2470 * MHz, FDD}, . And it turns out the UE attachment almost 100% fails after tunned to 2.4ghz.

question.tar.gz Where should I start to solve the problems. I attach several instances of error logs to the post.

Thanks!!!