User Guide

Chapter 8: Monitoring 17
• TX PAPR: stands for Peak-to-Average Power Ratio. PAPR is the ratio of peak power to the
average power of a signal. It is expressed in the units of dB. In LTE system, OFDM signal
PAPR is approx. 12dB . If RMS + PAPR exceed the max power of the power amplifier,
saturation will happen
• TX MAX: stands for Maximum. Displays the maximum sample value during the measurement
interval period.
• TX SAT: stands for Saturation. Displays the number of saturation events during the mea-
surement interval. If SAT value is different of 0, it means that the transmitted signal in
Downlink is saturated. In this case, tx gain should be decreased until SAT is equal to 0.
RX columns provides information about received signal power.
• RX RMS: stands for Received Root-Mean-Square. This is the mean value in dB FS (full
Scale)
• RX MAX: stands for Maximum. Displays the maximum sample value during the measurement
interval period. If RX MAX value equals to 0, it means that the received signal in UL is
saturated. In this case, rx gain should be decreased until RX MAX is below 0.
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) */
In RF cables test conditions, the recommended values for PCIe SDR cards are :
tx_gain: 60.0, /* TX gain (in dB) */
rx_gain: 00.0, /* RX gain (in dB) */
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Note : tx gain and rx gain commands can be used in eNB screen to decrease or increase the
TX gain and RX gain respectively
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8.2.3 t cpu command
t cpu command provides key information about the CPU load .This is useful for verifying that
PC is not running out of CPU when expected KPI are not reached.
-Proc- ---RX-------- ---TX-------- ---- TX/RX diff (ms)
CPU MS/s CPU MS/s CPU min/avg/max sigma
51.8% 23.040 6.6% 23.040 1.6% 2.23/2.8/3.3 0.2
52.9% 23.040 6.6% 23.039 1.6% 1.97/2.8/3.3 0.2
52.3% 23.040 6.6% 23.041 1.5% 2.20/2.8/3.3 0.2
51.4% 23.040 6.6% 23.040 1.6% 2.20/2.8/3.3 0.2
50.8% 23.040 6.6% 23.039 1.6% 2.19/2.8/3.3 0.2
t cpu shows CPU consumption for the main LTE task (Proc), the reception chain (RX) or
transmission chain (TX). Units are MS/s (Million of sample per second)
On top of that, t cpu command provides information on TX-RX delay: The min, average and
max values are given in milliseconds.
In other words, in LTE FDD mode as instance, eNodeB receives data in Uplink and must
acknowledge (or nack) them 4ms later to the UE. eNodeB has by consequence 4ms to decode the
uplink samples and send the ack/nack answer in downlink. The RX/TX delay is the remaining
time before data are processed and time they must be sent in downlink.
If this value decreases to zero, this means that PC is too slow and physical layer is running out
of CPU to process the data within this period. The higher is the TX/RX value is , the better
it is.