By paul ~ March 31st, 2008. Filed under: FAQ, SDR & SCA.
We’ve been asked about Foresight’s application to JTRS enough times that we thought it best to just include the following here for reference.
Early in the JTRS program, Foresight was contracted by JPO to develop a demonstration model for waveform/platform performance analysis and as a result, the use of Foresight was highly recommended to the GMR bidders by the selection committee.
Over the last three years, Foresight has been used on several JTRS-related performance modeling projects at Boeing, Northrop and GDC, with some of the results being published in OMG workshops (see whitepapers). This work has shown that Foresight-based performance modeling is effective and adds significant value to the JTRS program by providing:
- Early radio design guidance and performance prediction including processor and memory sizing, technology selection, memory and processor utilization and power analysis.
- Waveform design guidance and performance prediction on different candidate platforms. Performance metrics include startup time, packet latency, throughput, jitter, and QoS.
- Impact analysis of proposed requirement modifications, design changes, unmet constraints, or new waveforms.
- Performance models for use by JTRS client programs, such as FCS, that would be available before prototypes.
- Early detection and clear communication of component-level performance and timing/resource budget issues.
In addition, Foresight has been used on the FCS program for trade studies as part of the risk mitigation effort. This effort used and built upon a performance model of the WNW waveform running on the increment 0 GMR platform developed earlier. This work was highly successful and established the usefulness of a waveform/radio performance model to client programs.
Our experience has shown that, at the outset of performance modeling, only 50% of a model’s usefulness is envisioned. Once that model becomes available, even if incomplete, many other uses of the model become apparent. For instance, on the AMF program a performance model was used to perform a sensitivity analysis of the central non-volatile memory data read rate on startup time given a couple of different startup strategies. This provided excellent information for component selection from a model that was originally intended to provide startup time and processor utilization.
Foresight’s approach is to build a model of the radio platform, a model of the waveform, and then execute the waveform model on the radio platform model. The resulting composite model can accurately predict the behavior of the waveform when deployed on the radio. With such a composite model, the radio performance can be predicted under many different environmental scenarios, traffic patterns, etc. In addition, the model acts as an excellent experimental environment for trade studies to aid in design decisions or addressing problem areas.Moving from the radio model to systems-of-systems modeling at the network level (such as is required for FCS-type scenarios) can be accomplished in a number of ways. The Foresight radio models are complete enough to be connected together for a multiple radio scenario but, for modeling larger scenarios, it is probably better to abstract the performance of the radio model into a node model within a network simulation or operational scenario simulation.
In a nutshell, what we do is to create two models: (1) the radio hardware (CPUs, busses, memory, FPGA & DSPs) and (2) a model of the waveform, radio services and devices, operating environment (framework), CORBA, and RTOS. Then we execute the model of the software on the model of the radio to evaluate how the software will perform on the radio platform. We can model & measure:
- Processor utilization as a function of time
- Memory utilization
- Bus utilization as a function of time
- Packet or data latency & jitter through waveform
- Data throughput through the waveform
- Radio startup time
- CORBA overhead
- RTOS overhead
Using this model, we can also perform trade studies to determine optimal system configuration. The same software model(s) can be executed on different radio models through a simple re-mapping activity in order to evaluate application performance on different radio platforms that you may have to build.