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StatusOngoing
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Activity Code3A.143
The NTN NB-IoT test-bench project delivers:
- NTN NB-IoT base-station (eNB)
- remotely configurable: frequency band, cell-ID, power level
- a corresponding NTN NB-IoT User Equipment (UE) using a customised Access Stratum (AS), Non-Access Stratum (NAS) and Physical layer (PHY)
- ability to run multiple-instances of UE (up to 48)
- UEs will have parameterised characteristics, to represent different use cases
- eNB selection and re-selection
- operates in HD-FDD (Half-Duplex Frequency Division Duplex) mode
- uses standard NTN Radio Frequency (RF) bands 255, 256
- test scripts to control satellite channel emulator to vary: noise, Doppler, signal attenuation, delay for uplink and downlink
- UDP (User Datagram Protocol) and ping test applications
- tests Low Earth Orbit transparent and regenerative, and Geostationary Orbit operation
One of the challenges of this project is that the 3GPP® specifications are frequently refined and updated. CCww keeps a close watch for new versions of approved specifications and output from 3GPP® working groups, and updates its code as necessary.
Another challenge has been limitations of hardware performance. This has been mitigated by moving the upper PHY (Physical Layer) functionality to the fast PC, and configuring real-time priority for the most demanding processes (e.g. PHY-H and Medium access control (MAC) layers).
The exact synchronisation of timing and frequency of the sub-systems proved to be a challenge in the early stages of the project. These issues were resolved by adding external clock references to the eNB and channel emulator, and using Network Time Protocol (NTP) to align the time of day of the sub-systems.
The test bench provides early capability to designers and system integrators of base station, and IoT user terminal equipment to test and evaluate various features of their NTN IoT systems in a real-time environment. This can be done in a controlled laboratory situation, a long time before any final hardware platforms are available. Test sequences may be defined which exercise various scenarios for different orbits and modes, and allow regression testing following modifications to any sub-systems.
The test bench also allows satellite network operators to test the real-time operation of planned LEO NTN constellations long before they exist. The Two-line elements (TLE) orbital data can be loaded into the test bench system, and then the sequence of satellite movements is automatically executed for the duration of a test.
The UE developed as part of this project supports the 3GPP® 5G Release 17 NTN NB-IoT standard. This allows device manufacturers to license the software IP of the UE and integrate this into their own commercial user terminal products. The UE will interoperate with any other 3GPP® standards-based NTN IoT equipment.
The test bench system consists of 5 sub-systems; an NTN NB-IoT eNodeB (base station), multiple NTN NB-IoT UEs (user terminals), a minimal Core Network (CN), a satellite channel emulator, and a system manager/ diagnostics viewer.
The eNB is implemented on a PC and an NI/ Ettus SDR.
The lower physical layer (PHY-L) of the UE is implemented on a standard AMD/ Xilinx FPGA dev board under embedded Linux, and the upper physical layer (PHY-H), and protocol stack of the UE are executed on a high specification Intel i9 PC under a Ubuntu Linux OS, with a Gigabit Ethernet interface between the 2 platforms. A multiplexing functionality is provided to allow multiple instances of UE to be instantiated, so creating a more realistic test environment.
The channel emulator is implemented on a fast PC and NI/ Ettus SDRs (one for downlink and one for uplink path). This allows typical satellite weather impairments, Doppler shifts, and delays to be simulated.
The project consists of 2 initial parallel development phases for updates to the protocol stack and PHY, and creation of the test environment. These are followed by several stages of testing, adding different modes and more complex scenarios at each stage.
The Test Bench development is based on CCww’s and Lekha’s existing embedded software IP for terrestrial cellular Narrow-Band IoT.
All necessary development hardware has been sourced and configured in both CCww’s and Lekha’s labs.
The protocol stack and PHY for the UE have been updated to support 3GPP® NTN NB-IoT requirements, and multiplexing functionality has been added to the UE to allow multiple instancing.
A satellite channel emulator has been developed to implement GEO round trip delay, and the real-time orbital paths of LEO satellites with dynamically changing delay and Doppler shift, as well as the capability to inject impairments.
The integration of the various sub-systems has been completed and a suite of test sequences has been developed to exercise the various modes of operation; GEO, LEO transparent and regenerative.
