cambridge consultants SmartCart Portable LTE eNodeB Software User Guide
- June 9, 2024
- cambridge consultants
Table of Contents
cambridge consultants SmartCart Portable LTE eNodeB Software
Introduction
SmartCart is a portable LTE eNodeB that is used for testing new installations of SmartSky’s service on aircraft. It shares a common codebase with the SmartSky ground network eNodeBs including the nonstandard customisations of LTE to support the air-to-ground service. A USRP is used as the radio transceiver and the emissions of this transceiver are put through an FCC approvals process.
The SmartCart FCC test software drives the radio in a way that is representative of normal operation of SmartCart. It differs in the following ways:
- The eNodeB will transmit continuously and without needing a UE to talk to
- A normal LTE link has varying amounts of information in the control and data regions according to the data transferred, together with broadcast information and other overheads. The test software used a fixed data pattern and a fixed allocations so that measurements are repeatable and nontime-varying.
- The test software is intentionally a worst case as far as RF emissions are concerned. It can fully populate the on-air spectrum which may only occur transiently in normal operation.
Referenced documents
Table 1 – Referenced documents
| Reference | Title | Issued by |
|---|---|---|
| Reference 1. P4417-UG-016 | Smart Cart Installation Guide | CC |
Installing the software
The SmartCart FCC test software is part of the normal SmartCart installation. Either start with an already installed SmartCart or with reference to the installation manual (Reference 1 – P4417-UG-016):
- In section 4 “SmartCart Base station installation” follow steps 4.1 through 4.5 to install the software
- A login is needed to drive the software:
- This can be on the keyboard/monitor/console used for installation (step 9 of section 4.4 sets the password)
- This can be via SSH (see section 4.6) but it is recommended to use a different SSH key if the SmartCart is to be used by a test house or other non-SmartSky personnel
- Sections 4.7 eNodeB commissioning and 4.8 VPN commissioning are not required
Once SmartCart base station has been installed please stop and disable the normal SmartCart services by logging in and running:
smartcart@smartcart:~$ sudo systemctl stop enodeb
smartcart@smartcart:~$ sudo systemctl disable enodeb
smartcart@smartcart:~$ sudo systemctl stop diagnostics
smartcart@smartcart:~$ sudo systemctl disable diagnostics
then reboot the SmartCart base station. Running the software
The software is controlled by a script that will print its help text if called with no arguments:
usage: enodeb_test.py [-h] --bandwidth BANDWIDTH --allocation ALLOCATION --modulation MODULATION [--gain
GAIN] [--dev]
enodeb test-app runner script
optional arguments:
-h, --help show this help message and exit
--bandwidth BANDWIDTH
Bandwidth [5|10]
--allocation ALLOCATION
Allocation [full|low|mid|high]
--modulation MODULATION
Modulation [qpsk|qam16|qam64]
--gain GAIN Gain (default: 90)
--dev Enable development options Note the following about the parameters:
-
SmartCart uses an LTE cell with a nominal bandwidth of 5 MHz (an occupied bandwidth of 4.5 MHz); selecting 5 MHz also configured the lowest channel centre frequency of 2448.2 MHz.
-
Testing can be performed with a 10 MHz nominal (9 MHz occupied) bandwidth and this uses a channel centre frequency of 2450.7 MHz
-
A full allocation will occupy the entire LTE bandwidth and results in the highest average
transmitted power output. Otherwise the allocation occupies the minimum bandwidth possible that is consistent with the 500kHz minimum bandwidth limit in the FCC rules. low will place this allocation at the low frequency edge of the LTE channel bandwidth, high at the high frequency edge and mid in approximately the centre. -
SmartCart may use any of QPSK, QAM16 or QAM64 in normal operation. For FCC approvals select the worst case (based on measurements).
-
The gain should be set to at least the highest used in SmartCart i.e. 90.
Run the script with the relevant parameters e.g.:
$ sudo python3 /usr/local/bin/enodeb_test.py --bandwidth 5 --allocation full --modulation qam16
[INFO] [UHD] linux; GNU C++ version 9.3.0; Boost_107100; UHD_3.15.0.0-0-unknown
[INFO] [B200] Detected Device: B200
[INFO] [B200] Operating over USB 3.
[INFO] [B200] Detecting internal GPSDO....
[INFO] [GPS] Found an internal GPSDO: GPSTCXO, Firmware Rev 0.929b
[INFO] [B200] Initialize CODEC control...
[INFO] [B200] Initialize Radio control...
[INFO] [B200] Performing register loopback test...
[INFO] [B200] Register loopback test passed
[INFO] [B200] Setting master clock rate selection to 'automatic'.
[INFO] [B200] Asking for clock rate 16.000000 MHz...
[INFO] [B200] Actually got clock rate 16.000000 MHz.
Running: /usr/local/bin/pdsch_enodeb -a 'clock=gpsdo,serial=31ED0F9' -S -F -c 25 -g 90 -p 25 -f
2448200000 -N 13 -O 0 -m 14
Opening RF device...
Available RF device list: UHD zmq
Trying to open RF device 'UHD'
[INFO] [UHD] linux; GNU C++ version 9.3.0; Boost_107100; UHD_3.15.0.0-0-unknown
[INFO] [LOGGING] Fastpath logging disabled at runtime.
Opening USRP channels=1, args: serial=31ED0F9,type=b200,master_clock_rate=23.04e6
[INFO] [UHD RF] RF UHD Generic instance constructed
[INFO] [B200] Detected Device: B200
[INFO] [B200] Operating over USB 3.
[INFO] [B200] Detecting internal GPSDO....
[INFO] [GPS] Found an internal GPSDO: GPSTCXO, Firmware Rev 0.929b
[INFO] [B200] Initialize CODEC control...
[INFO] [B200] Initialize Radio control...
[INFO] [B200] Performing register loopback test...
[INFO] [B200] Register loopback test passed
[INFO] [B200] Asking for clock rate 23.040000 MHz...
[INFO] [B200] Actually got clock rate 23.040000 MHz.
Setting USRP time to 1664180657.000000s
[INFO] [MULTI_USRP] 1) catch time transition at pps edge
[INFO] [MULTI_USRP] 2) set times next pps (synchronously)
/builds/p4417/lte-stack/CC-srsLTE/lib/src/phy/rf/rf_uhd_imp.cc:822: Could not lock reference clock
source. Sensor: gps_locked=false
RF device 'UHD' successfully opened
Setting sampling rate 5.76 MHz
Set TX gain: 89.8 dB
Set TX freq: 2448.20 MHz
- Resource Allocation Type: Type 0
+ Resource Block Group Size: 2
+ RBG Bitmap: 0x1fff
- HARQ process: 0
- TPC command for PUCCH: --
- Transport blocks swapped: false
- Transport block 0 enabled: true
+ Modulation and coding scheme index: 14
+ New data indicator: No
+ Redundancy version: 0
- Transport block 1 enabled: false The eNodeB will run continuously and measurements can be made. See Appendix A
for example performance.
To stop the application press Ctrl-C:
^CSIGINT received. Exiting... Done Restoring normal operation
At the end of FCC testing reinstall SmartCart base station by following installation manual (Reference 1 – P4417-UG-016) including the eNodeB commissioning and VPN steps.
Appendix A
Figure 1 shows the typical performance of the USRP connected to an LTE analyser. Figure 2 and Figure 3 show the extent to which the resource grid is full for 5 MHz and 10 MHz allocations. Figure 4 shows the allocation detail and relative power of PDCCH vs PDSCH for 5MHz. The figures are not corrected for cable loss – the signal power at gain of 90 should be around 2 dBm and RSTP around -25 dBm.
Figure 1 LTE summary with full allocation
FCC Compliance Statement
Changes or modifications not expressly approved by Sma rtSky Networks could void the user’s authority to operate the equipment.
Note: This equipment has been tested and found to comply with the limits for a Class A digital device, pursuant to part 1S of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference when the equipment is operated in a commercial environment. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with the instruction manual, may cause harmful interference to radio communications. Operation of this equipment in a residential area is likely to cause harmful interference in which case the user will be required to correct the interference at his own expense.
This equipment complies with FCC radiation exposure limits set forth for an uncontrolled environment. This equipment shall be installed and operated with a minimum distance of 20cm between the radiator and any part of your body.
