User guide
Table Of Contents
- Introduction
- Hardware setup
- Connection to AMARI UE Simbox
- LTE service
- Initial setting
- Create scenario using WebGui
- Run UE scenarios with WebGui
- Create scenario without WebGui
- Downlink and Uplink transfer using iperf
- NB-IOT devices
- Channel simulator
- logging
- Advanced options
- Troubleshooting
Chapter 14: Troubleshooting 45
14.3 Downlink peak throughput not achieved
If peak throughput is not achieved in Downlink, a first investigation can be done at physical
layer using the webGui. In the main panel, click on analytics button. A new window will pop
up. Note : physical layer trace level must be set to debug prior to the testing.
In this new window, several statistics are displayed and provide useful information about UE
performance
Throughput
Displays Downlink and Uplink throughput at physical layer
CQI CQI values reported by the UE to the eNodeB. A low CQI value means that Down-
link channel quality is low and results in low throughput in downlink as eNodeB
will use small MCS
Rank indicator
Rank Indicator values reported by UE to the eNodeB. A RI of 0 means that UE is
not able to receive data in MIMO mode (TM3) and results in lower throughput .
This can be caused by a low SNR, or a high correlation between two antenna stream
or simply because the n_antenna_dl parameter as been set to 1 in the ue.cfg file
TPC TPC (Transmit power control) average values received by the eNodeB. Note: When
channel simulation is disabled, TPC command are not taken into account by the
UE. The transmit power is set in the configuration file
RX/TX packets
Display number of packet received and sent with good and bad CRC (cyclic redun-
dancy check) This graphic give a good overview of the downlink/uplink performance.
In perfect radio conditions, no packet with bad CRC should be received by UE or
eNodeB. Having a high number of bad CRC indicates that RF path is not optimal
or that UE is running out of CPU.
t cpu command provides CPU indication at UE side.
• If webGui is used for downlink, verify that ltesim server service is running on eNodeB
(./ltesim server -a 192.168.3.1) and check that scenario created under webBui uses the
same IP address.
• Force CQI and RI values (RI reported value is not dynamic and forced CQI value may give
better throughput than the one calculated by the LTE UE simulator based on downlink
signal quality)