UE Configuration

This page covers srsRAN UE configuration and usage.

Overview

srsUE is a software 5G user terminal implementation, useful for:

• End-to-end testing without real phones
• Automated test scenarios
• Debugging and analysis

Hardware Requirements

srsUE requires a separate SDR device:

Device	Description
USRP B210	Recommended, full 5G support
ZMQ	Virtual RF, for gNB testing

Configuration Example

Real SDR Configuration

# ue.yaml
rat: nr                      # Network type

nas:
  apn: internet              # APN/DNN
  type: ipv4                 # PDN type

usim:
  mode: soft                 # Soft USIM
  algo: milenage             # Auth algorithm
  imsi: '001010000000001'    # IMSI
  k: 465B5CE8B199B49FAA5F0A2EE238A6BC      # K
  opc: E8ED289DEBA952E4283B54E88E6183CA    # OPc
  amf: 8000

cell_search:
  dl_arfcn: 632628           # Downlink ARFCN
  band: 78                   # NR band
  subcarrier_spacing: 30     # Subcarrier spacing

# SDR configuration
rf:
  device_name: uhd
  device_args: type=b200
  rx_gain: 40
  tx_gain: 50
  srate: 23.04e6

log:
  filename: /tmp/ue.log
  all_level: info
  nas_level: debug
  rrc_level: debug

ZMQ Simulation Configuration

For testing with ZMQ mode gNB:

# ue_zmq.yaml
rat: nr

nas:
  apn: internet
  type: ipv4

usim:
  mode: soft
  algo: milenage
  imsi: '001010000000001'
  k: 465B5CE8B199B49FAA5F0A2EE238A6BC
  opc: E8ED289DEBA952E4283B54E88E6183CA
  amf: 8000

cell_search:
  dl_arfcn: 368500
  band: 3
  subcarrier_spacing: 15

rf:
  device_name: zmq
  device_args: tx_port=tcp://127.0.0.1:2001,rx_port=tcp://127.0.0.1:2000,base_srate=23.04e6
  rx_gain: 40
  tx_gain: 50
  srate: 23.04e6

log:
  filename: /tmp/ue.log
  all_level: info

Key Parameters

USIM Parameters

Parameter	Description
imsi	Must match Open5GS
k	Authentication key, must match Open5GS
opc	Operator key, must match Open5GS
amf	Usually 8000
algo	milenage or xor

Cell Search Parameters

Parameter	Description
dl_arfcn	Must match gNB config
band	NR band number
subcarrier_spacing	Subcarrier spacing (kHz)

Start srsUE

Basic Start

sudo srsue -c ue.yaml

Background

sudo srsue -c ue.yaml > /tmp/ue.log 2>&1 &

Registration Process

Successful UE registration logs:

[NAS    ] 5GMM State: MM-DEREGISTERED -> MM-REGISTERED-INITIATED
[RRC    ] RRC Connected
[NAS    ] 5GMM State: MM-REGISTERED-INITIATED -> MM-REGISTERED
[NAS    ] PDU Session Establishment successful
[IP     ] Interface tun_srsue created, IP: 10.45.0.2

Data Testing

Check TUN Interface

ip addr show tun_srsue

Ping Test

# Ping through UE TUN interface
ping -I tun_srsue 8.8.8.8

Speed Test

# Install iperf3
sudo apt install iperf3

# Server side (on machine with internet)
iperf3 -s

# Client side (through UE interface)
iperf3 -c <server_ip> -B 10.45.0.2

ZMQ End-to-End Testing

Complete testing method without SDR hardware.

1. Start Open5GS

sudo systemctl start open5gs-nrfd
sudo systemctl start open5gs-amfd
sudo systemctl start open5gs-smfd
sudo systemctl start open5gs-upfd
# ... other services

2. Start gNB (ZMQ Mode)

sudo gnb -c gnb_zmq.yaml

3. Start UE (ZMQ Mode)

sudo srsue -c ue_zmq.yaml

4. Verify Connection

# Check UE assigned IP
ip addr show tun_srsue

# Ping test
ping -I tun_srsue 10.45.0.1

Troubleshooting

Cell Search Failed

[PHY    ] Cell search failed

Check:

1. dl_arfcn and band are correct
2. SDR is working properly
3. gNB is broadcasting

Authentication Failed

[NAS    ] Authentication Failure

Check:

1. IMSI, K, OPc match Open5GS
2. Subscriber is added to core network
3. AMF value is correct

PDU Session Failed

[NAS    ] PDU Session Establishment rejected

Check:

1. APN/DNN is correct
2. SMF/UPF configuration is correct
3. TUN interface is created

Next Steps

• Getting Started - Complete lab workflow
• Open5GS Subscriber - Manage UE subscribers