SE3: Two-Node LTE MIMO

1) Experiment Overview

Experiment Definition: The user logs into one E-VM on the fixed AERPAW Node (Machine #1) and one E-VM on the fixed AERPAW Node (Machine #2). At the end of the experiment, the user can view logs and test results.

Experiment Scenarios Applicable: S1, S2, S3, S4, S7. These scenarios correspond to various different user experimentation scenarios in AERPAW.

Experiment Goals: The main goal of this experiment is to provide a complete end-to-end LTE network, using srsUE with srsENB and srsEPC in a 2x2 MIMO configuration.The different modes offered in this experiment are TESTBED and applicable tests for these modes are PING, IPERF

Mode Descriptions:

TESTBED

Base Station to Single UE Link (# of UEs + 1 PCs)

Description: This mode sets up an EPC and eNB on one machine and a UE on one or more machines. A connection will be established. If the default configuration settings are used, the radios will operate within the 3.3 - 3.55 GHz spectrum (band 22) at 10 MHz bandwidth (50 resource blocks) using FDD.

Test Descriptions:

PING

Description: Ping (latency is the technically more correct term) means the time it takes for a small data set to be transmitted from your device to a server on the Internet and back to your device again. The ping time is measured in milliseconds (ms)

IPERF

Description: Iperf has client and server functionality, and can create data streams to measure the throughput between the two ends in one or both directions.

Software version

Machine #1 (for B210 Container):

• Ubuntu version 18.04

• srsLTE version 20.10 

• uhd 3.15 

Machine #2 (for B210 container):

• Ubuntu version 18.04

• srsLTE version 20.10

• uhd 3.15

Most Common Configuration Parameters:

• Transmission mode: this enables MIMO using the specified transmission mode of 2, 3, or 4

• EARFCN (center frequency): this sets the center frequency of the downlink transmission for 3GPP supported bands. The uplink center frequency is automatically set, and it depends on whether the band is TDD (same uplink and downlink frequency) or FDD (uplink and downlink offset by the channel spacing)

• LTE system bandwidth, configured as resource blocks: supported values are 6 resource blocks for 1.4 MHz system bandwidth, 15 for 3 MHz, 25 for 5 MHz, 50 for 10 MHz, 75 for 15 MHz and 100 for 20 MHz

• USRP Tx Gain (sets the gain of variable PA in the USRP in the range of 0 to 89 for B series, 0 to 30 for X310): default is 0 dBFS which has been determined for the external Tx RF front end.

• USRP Rx Gain (sets the gain of variable PA in the USRP in the range of 0 to 76 for B series, 0 to 30 for X310): default is 0 dBFS which has been determined for the external Rx RF front end and Tx/Rx isolation.

2) Performing the Experiment:

2.A) Choosing the Experiment Mode

Machine #1:

LTE Base Station (eNodeB or eNB) configuration

We assume the transmitter is a fixed node. Login to the E-VM corresponding to the fixed node. Navigate to the folder containing all the Radio scripts

$ cd /root/Profiles/ProfileScripts/Radio

Copy the startSRSRAN-MIMO-EPCandENB.sh script as startRadio.sh

$ cp Samples/startSRSRAN-MIMO-EPCandENB.sh startRadio.sh

Use an editor to uncomment the line /Radio/startRadio.sh in /root/startexperiment.sh and run the following command:

$ /root/startExperiment.sh

Machine #2+:

User equipment (UE) configuration

We assume the transmitter is a portable node. Login to the E-VM corresponding to the portable node. Navigate to the folder containing all the Radio scripts

$ cd /root/Profiles/ProfileScripts/Radio

Copy the startSRSRAN-MIMO-UE.sh script as startRadio.sh

$ cp Samples/startSRSRAN-MIMO-UE.sh startRadio.sh

Use an editor to uncomment the line /Radio/startRadio.sh in /root/startexperiment.sh and run the following command:

$ /root/startExperiment.sh

3) Modifying the Experiment Configuration Parameters:

Core Network & Base Station: 

The shell script /root/Profiles/ProfileScripts/Samples/startSRSRAN-MIMO-EPCandENB.sh calls two scripts /root/Profiles/ProfileScripts/Radio/Helpers/startEPC.sh and /root/Profiles/ProfileScripts/Radio/Helpers/startENBMIMO.sh which can be edited by the experimenter to modify the parameters of the core network and base station.

UE: 

The shell script /root/Profiles/ProfileScripts/Samples/startSRSRAN-MIMO-UE.sh calls the script /root/Profiles/ProfileScripts/Radio/Helpers/startUEMIMO.sh which can be edited by the experimenter to modify the parameters of the UE.

For advanced users, the IP address per UE can be statically assigned. Please refer to section 4.1.1) SrsRan Experiments for further instruction

4) Results:

Results can be viewed by executing the following commands:

4.A) Ping Results:

The UE will search for a cell at the specific frequency. The experiment generates a timestamped measurement log under the /root/Results folder. Once it finds a cell, it will initiate the attachment processes and once attached, the data sessions can be established.

4.B) IPERF Results:

The UE will search for a cell at the specific frequency. The experiment generates timestamped measurement log under the /root/Results folder. Once it finds a cell, it will initiate the attachment processes and once attached, the data sessions can be established. Example results using iperf are shown in Figure 1.