Eric N. Koski

The JTRS program: software-defined radios as a software product line

The Joint Tactical Radio System (JTRS) program of the US Department of Defense is an ambitious multiyear initiative aimed at developing a new family of highly capable software programmable radio systems designed around a common software communications architecture (SCA). The procurement and development approaches of the JTRS initiative make it an interesting application of a software product line strategy. In this paper, we (a) provide an overview of the JTRS program, its key technologies, and its development and procurement strategies; (b) highlight the aspects of the JTRS program that make it a clear instance of a software product line; (c) analyze the degrees of success with which product line concepts have been applied within the JTRS initiative, and highlight some ongoing challenges; (d) discuss the significance of the JTRS initiative for the software product lines community.

Channel Quality Variation as a Design Consideration for Wireless Data Link Protocols

The data link protocol HDL+, which has been proposed for incorporation into NATO STANAG 4538, employs an innovative combination of Type II Hybrid-ARQ techniques with real-time adaptation of signal constellation and code rate to achieve high throughput performance under a wide variety of channel conditions. The ionospheric HF channels for which HDL+ was designed exhibit important variations in channel quality (SNR, fading and multipath chcracteristics) at a variety of time scales from seconds to minutes. It appears plausible that the design characteristics of the HDL+ protocol couldprove especially valuable in coping with time-varying channel quality over these time scales. In this paper, we ¿ Present and discuss a model of channel quality variation and a way of incorporating it into an ionospheric channel simulator suitable for performance characterization of HF communications waveforms andprotocols ¿ Provide overviews of HDL+ and of the STANAG 5066 data link protocol, a widely-used protocol based on conventional (not hybrid) ARQ techniques ¿ Present and discuss comparative performance data for the HDL+ and STANAG 5066 protocols obtained under test conditions including channel quality variation.

Efficient high-fidelity simulation of HF communications systems and networks

Harris Corporation is conducting a series of investigations in which network simulations are used to characterize and analyze the performance of existing HF communications waveforms and protocols, and to develop and optimize innovative techniques realizing improved network throughput, capacity, and user experience. The work reported in this paper includes development of HF physical layer models providing high-fidelity simulation of modem error statistics as a function of the channel attributes of the widely-used Watterson ionospheric channel model; implementation and validation of a simulation model of the NATO STANAG 5066 data link protocol; and integration of these models with the OMNeT++ network simulation framework and its INET library of Internet protocol models. The integrated simulation model is used to characterize the impacts of different STANAG 5066 configuration settings on bulk data throughput, to characterize system performance in conjunction with the TCP transport layer protocol, and to investigate performance improvements realizable over HF links with TCP performance enhancing proxy (PEP) techniques.

RF Performance Implications of Wideband HF Waveforms

Emerging approaches to HF communications aim to increase the range of missions and applications HF can support by using higher bandwidths to achieve higher on-air data rates and/or improved communications robustness. Current proposals achieve this in either of two ways: by (i) increasing the bandwidth allocated to a single-carrier modulated waveform, to up to 24 kHz (or possibly higher), or (ii) using existing modulation formats to simultaneously modulate up to 16 carriers in noncontiguous 3 kHz channels. Each of these approaches has inevitable consequences for both radio system performance and spectrum utilization and availability. Both the US Department of Defense and NATO have standards documents (respectively, MIL-STD-188-141C and STANAG 4203) intended to specify the performance and spectral occupancy characteristics of military HF radios. However, these standards have been primarily focused on operation on traditional 3 kHz channels, and do not fully address either of the two proposed Wideband HF (WBHF) approaches. This paper analyzes some key performance impacts of the two WBHF approaches, uses a simple system model to predict the spectrum occupancy and efficiency of the two approaches, and provides recommendations for new and revised requirements to address Wideband HF systems in the applicable US and NATO standards.