User guide

Chapter 5: Initial setting 13
bandwidth: 20,
dl_nr_arfcn: 632628,
ssb_nr_arfcn: 632256,
subcarrier_spacing: 30,
n_antenna_dl: 1,
n_antenna_ul: 1,
}],
}],
5.4 TX/RX gain setting
TX and RX gain values must be fine tuned depending on your setup (conducted vs wireless
conditions, physical attenuator used, combiner/divider, etc..) as dynamic power control is not
handled at UE side (excepted if channel simulation mode is enabled) .
TX and RX gain values are defined in RF configuration file located under
/root/ue/config/rf
driver directory. To know which files is used by LTE service, just
look at ue.cfg file. Example:
include "rf_driver/1chan.cfg",
5.4.1 Wired test
In wired test conditions, it’s recommended to put attenuator between eNodeB and LTE UE
simulator in order not to damage SDR cards and avoid saturation.
On UE Simulator side, max SDR input is -10 dBm, max SDR output is 5dBm.
Recommended values for PCIe SDR cards are :
tx_gain: 60.0, /* TX gain (in dB) */
rx_gain: 0.0, /* RX gain (in dB) */
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Note: If physical attenuators are used, equivalent gain must be added to these default values
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5.4.2 Wireless test
In Wireless test conditions, the recommended values for PCIe SDR cards are :
tx_gain: 90.0, /* TX gain (in dB) */
rx_gain: 60.0, /* RX gain (in dB) */
5.5 Multiple UE mode and timing advance
To activate the simulation of multiple UEs, the parameter multi_ue must be set to true.
The "multiple UE" mode aims to simulate hundreds of devices on the same PC sharing the same
physical layer. As a consequence all UE have the same timing advance and this value must be
defined in the ue.cfg file.
There are two ways to define the timing advance for multiple UE.
• It can be set automatically by using the global_timing_advance=-1. If automatic mode
is set, the UE simulator uses the timing advance from the first received RAR for all UEs.
This is the default behaviour.
• It can be set manually by using the global_timing_advance=x, (x = TA of the uplink
relative to the downlink in 1/1.92 us unit)