Issue with 4G LTE Signal Detection and Internet Connectivity in SRSRAN

[Andrysm]

Hello,
I am working on a 4G LTE project using SRSRAN and USRP B210 as the hardware. I have encountered an issue where the 4G LTE signal is detected intermittently. Sometimes the UE connects successfully, but most of the time it fails to detect the network, or the connection drops frequently. Additionally, the internet connection is not established, even though the 4G LTE signal appears on the UE.

Problem Details:

1. The 4G LTE signal is sometimes detected, but it keeps disconnecting and reconnecting intermittently.
2. There is no internet connectivity even though the UE is connected to the network.
3. I have checked the logs and seen messages about RRC Reestablishment and Tx while waiting for EOB timed out, but I am unable to identify the root cause.

Steps I have tried:

1. I have adjusted tx_gain and rx_gain settings in the eNB configuration.
2. I checked and ensured that the CPU Governor is set to performance mode.
3. I tested the connectivity with different earfcn and RACH parameters.

Despite these changes, the issue persists, and I am unsure why the internet connection is still not established.

Questions:

1. Can you help me understand why the 4G LTE signal is unstable and intermittently detected?
2. Why am I unable to get internet connectivity despite the 4G LTE signal being available?
3. Are there any other configuration parameters or steps I should check in the SRSRAN setup to resolve this issue?

Any help or advice would be greatly appreciated!
Thank you.

EPC CONFIG
[mme]
mme_code = 0x1a
mme_group = 0x0001
tac = 0x0007
mcc = 510
mnc = 77
mme_bind_addr = 127.0.1.100
apn = 12345
dns_addr = 8.8.8.8
encryption_algo = EEA0
integrity_algo = EIA1
paging_timer = 2
request_imeisv = false
lac = 0x0006

[hss]
db_file = /home/andry/.config/srsran/user_db.csv

[spgw]
gtpu_bind_addr = 127.0.1.100
sgi_if_addr = 172.16.0.1
sgi_if_name = srs_spgw_sgi
max_paging_queue = 100

[log]
all_level = debug
all_hex_limit = 32
filename = /tmp/epc.log

ENB Config
[enb]
enb_id = 0x18B
mcc = 510
mnc = 77
mme_addr = 127.0.1.100
gtp_bind_addr = 127.0.1.1
s1c_bind_addr = 127.0.1.1
s1c_bind_port = 0
n_prb = 25
tm = 1
nof_ports = 1

[enb_files]
sib_config = sib.conf
rr_config = rr.conf
rb_config = rb.conf

[rf]
dl_earfcn = 500
tx_gain = 100
rx_gain = 50

device_name = uhd

[log]
all_level = debug
all_hex_limit = 32
filename = /tmp/enb.log
file_max_size = -1

[gui]
enable = false

LOG EPC
Attach request -- Attach type: 2
Attach Request -- UE Network Capabilities EEA: 11110000
Attach Request -- UE Network Capabilities EIA: 01110000
Attach Request -- MS Network Capabilities Present: true
PDN Connectivity Request -- EPS Bearer Identity requested: 0
PDN Connectivity Request -- Procedure Transaction Id: 86
PDN Connectivity Request -- ESM Information Transfer requested: true
Attach Request -- Found previously attach UE.
Received GTP-C PDU. Message type: GTPC_MSG_TYPE_DELETE_SESSION_REQUEST
Downlink NAS: Sending Authentication Request
UL NAS: Received Authentication Response
Authentication Response -- IMSI 510770123456781
UE Authentication Accepted.
Generating KeNB with UL NAS COUNT: 0
Downlink NAS: Sending NAS Security Mode Command.
UL NAS: Received Security Mode Complete
Security Mode Command Complete -- IMSI: 510770123456781
Sending ESM information request
UL NAS: Received ESM Information Response
ESM Info: APN 12345
Getting subscription information -- QCI 7
Sending Create Session Request.
Creating Session Response -- IMSI: 510770123456781
Creating Session Response -- MME control TEID: 3
Received GTP-C PDU. Message type: GTPC_MSG_TYPE_CREATE_SESSION_REQUEST
SPGW: Allocated Ctrl TEID 3
SPGW: Allocated User TEID 3
SPGW: Allocate UE IP 172.16.0.4
Received Create Session Response
Create Session Response -- SPGW control TEID 3
Create Session Response -- SPGW S1-U Address: 127.0.1.100
SPGW Allocated IP 172.16.0.4 to IMSI 510770123456781
Adding attach accept to Initial Context Setup Request
Sent Initial Context Setup Request. E-RAB id 5
Received Initial Context Setup Response
E-RAB Context Setup. E-RAB id 5
E-RAB Context -- eNB TEID 0x3; eNB GTP-U Address 127.0.1.1
UL NAS: Received Attach Complete
Unpacked Attached Complete Message. IMSI 510770123456781
Unpacked Activate Default EPS Bearer message. EPS Bearer id 5
Received GTP-C PDU. Message type: GTPC_MSG_TYPE_MODIFY_BEARER_REQUEST
Sending EMM Information
UL NAS: PDN Connectivity Request
DL NAS: Sending PDN Connectivity Reject
UL NAS: PDN Connectivity Request
DL NAS: Sending PDN Connectivity Reject
Received UE Context Release Request. MME-UE S1AP Id 6
There are active E-RABs, send release access bearers request
Received GTP-C PDU. Message type: GTPC_MSG_TYPE_RELEASE_ACCESS_BEARERS_REQUEST
Received UE Context Release Complete. MME-UE S1AP Id 6
UE Context Release Completed.
Initial UE message: LIBLTE_MME_MSG_TYPE_TRACKING_AREA_UPDATE_REQUEST
Received Initial UE message -- Tracking Area Update Request
Tracking Area Update Request -- S-TMSI 0x5e14d1a8
Tracking Area Update Request -- eNB UE S1AP Id 6
Warning: Tracking area update requests are not handled yet.
Initial UE message: LIBLTE_MME_MSG_TYPE_ATTACH_REQUEST
Received Initial UE message -- Attach Request
Attach request -- M-TMSI: 0x5e14d1a8
Attach request -- eNB-UE S1AP Id: 7
Attach request -- Attach type: 2
Attach Request -- UE Network Capabilities EEA: 11110000
Attach Request -- UE Network Capabilities EIA: 01110000
Attach Request -- MS Network Capabilities Present: true
PDN Connectivity Request -- EPS Bearer Identity requested: 0
PDN Connectivity Request -- Procedure Transaction Id: 88
PDN Connectivity Request -- ESM Information Transfer requested: true
Attach Request -- Found previously attach UE.
Found UE context. IMSI: 510770123456781, old eNB UE S1ap Id 0, old MME UE S1AP Id 0
Received GUTI-Attach Request from attached user.
GUTI Attach request NAS integrity failed.
RE-starting authentication procedure.
Received GTP-C PDU. Message type: GTPC_MSG_TYPE_DELETE_SESSION_REQUEST
Downlink NAS: Sent Authentication Request
UL NAS: Authentication Failure
Authentication Failure -- Synchronization Failure
Downlink NAS: Sent Authentication Request
UL NAS: Received Authentication Response
Authentication Response -- IMSI 510770123456781
UE Authentication Accepted.
Generating KeNB with UL NAS COUNT: 0
Downlink NAS: Sending NAS Security Mode Command.
UL NAS: Received Security Mode Complete
Security Mode Command Complete -- IMSI: 510770123456781
Sending ESM information request
Unhandled NAS integrity protected message LIBLTE_MME_MSG_TYPE_ESM_STATUS
Received UE Context Release Request. MME-UE S1AP Id 7
No UE context to release found. MME-UE S1AP Id: 7
Received UE Context Release Request. MME-UE S1AP Id 9
Initial UE message: LIBLTE_MME_MSG_TYPE_ATTACH_REQUEST
Received Initial UE message -- Attach Request
Attach request -- M-TMSI: 0x5e14d1a8
Attach request -- eNB-UE S1AP Id: 8
Attach request -- Attach type: 2
Attach Request -- UE Network Capabilities EEA: 11110000
Attach Request -- UE Network Capabilities EIA: 01110000
Attach Request -- MS Network Capabilities Present: true
PDN Connectivity Request -- EPS Bearer Identity requested: 0
PDN Connectivity Request -- Procedure Transaction Id: 89
PDN Connectivity Request -- ESM Information Transfer requested:

LOG ENB
Disconnecting rnti=0xb40.
Disconnecting rnti=0xb3f.
Disconnecting rnti=0xb3e.
Disconnecting rnti=0xb3d.
Disconnecting rnti=0xb3c.
RACH: tti=2921, cc=0, pci=1, preamble=40, offset=14, temp_crnti=0xb51
RACH: tti=2921, cc=0, pci=1, preamble=43, offset=20, temp_crnti=0xb52
RACH: tti=2921, cc=0, pci=1, preamble=46, offset=25, temp_crnti=0xb53
RACH: tti=2921, cc=0, pci=1, preamble=49, offset=31, temp_crnti=0xb54
Disconnecting rnti=0xb45.
Disconnecting rnti=0xb44.
Disconnecting rnti=0xb43.
Disconnecting rnti=0xb42.
Disconnecting rnti=0xb41.
RACH: tti=2941, cc=0, pci=1, preamble=1, offset=9, temp_crnti=0xb55
RACH: tti=2941, cc=0, pci=1, preamble=4, offset=14, temp_crnti=0xb56
RACH: tti=2941, cc=0, pci=1, preamble=7, offset=20, temp_crnti=0xb57
RACH: tti=2941, cc=0, pci=1, preamble=10, offset=25, temp_crnti=0xb58
RACH: tti=2941, cc=0, pci=1, preamble=13, offset=31, temp_crnti=0xb59
RACH: tti=2961, cc=0, pci=1, preamble=1, offset=25, temp_crnti=0xb5a
Disconnecting rnti=0xb4a.
Disconnecting rnti=0xb49.
Disconnecting rnti=0xb48.
Disconnecting rnti=0xb47.
Disconnecting rnti=0xb46.
RACH: tti=2961, cc=0, pci=1, preamble=4, offset=31, temp_crnti=0xb5b
RACH: tti=2961, cc=0, pci=1, preamble=25, offset=43, temp_crnti=0xb5c
RACH: tti=2961, cc=0, pci=1, preamble=27, offset=1, temp_crnti=0xb5d
RACH: tti=2961, cc=0, pci=1, preamble=30, offset=7, temp_crnti=0xb5e