This paper studies a jamming statistics-dependent frequency-hopping (FH) pattern generation scheme. Most existing FH patterns are determined by two encryption keys: (a) one for FH in the frequency domain, and (b) the other for time permutation in the time domain. These keys are independent of channel conditions. Hence, an FH signal generated by these two keys occupies the entire spectrum in both frequency and time domains, and the probability of detection by a jammer is low. However, the probability of a hit (or jamming) on the desired user's frequency channels by partial-band noise jamming (PBNJ) can be high because it is inversely proportional to the total number of available frequency positions. Can an FH system with jamming-dependent adaptive FH patterns safeguard the communications systems more effectively? If the answer is yes, then how can an efficient jamming-dependent adaptive FH pattern be found, and can it be implemented cost-effectively for future communications systems against jamming? The aim of this paper is to study answers to the questions posed here.

Jamming statistics-dependent frequency hopping

As opposed to chaotic communication systems where a message signal directly modulates a broadband chaotic signal, it is also possible to indirectly utilise a chaotic signal to form a chaos-based communication system. This study proposes a class of novel broadband chaos-based coherent communication systems and demonstrates that their theoretical probability of error expressions match those of their counterpart conventional narrowband systems in the additive white Gaussian noise and the Rayleigh flat fading channel. The results are confirmed with the corresponding empirical bit error rate (BER) simulations. It is demonstrated that the chaos-based quadrature phase shift keying system offers an overall best performance while the chaos-based amplitude shift keying and frequency shift keying equivalent systems offer a possibility of performance optimisation. Most importantly, it is shown that the proposed systems outperform the chaotic communication systems in terms of BER while also being more practicable. The proposed systems thus hold high promise as the chaotic communication systems pose implementation difficulties, lack robust synchronisation techniques and are generally considered of academic interest only.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-com.2016.0432

Class of novel broadband chaos-based coherent communication systems

Group communication over multicast ad hoc network suffers from insufficient utilization of limited resources, i.e. shared channel, battery, data processing capabilities and storage space etc. Multicast routing protocol should be able to manage all these resources because their consumption depends upon different factors, i.e. Unicast/Multicast network operations, dynamic topology due to mobility, control overhead due to scalability, packet loss and retransmission due to collision and congestion etc. All these factors may cause unnecessary network load, delay and unfair resource utilization. However, multicast ad hoc routing protocols are more efficient than Unicast routing protocols, but they also suffer from performance degradation factors discussed above. Researchers have developed various layer wise solutions for resource optimization. In this paper, we will explore the different schemes for fair utilization of network resources.

/pdf/efficient-resource-management-for-multicast-ad-hoc-networks-3u39u4bw2f.pdf

Efficient Resource Management for Multicast Ad Hoc Networks: Survey

This paper analyzes the outage probability of a multicarrier signal, using the Protected Tactical Waveform (PTW) on the return link (RL). The signal is relayed over a nonlinear distorted satellite transponder. The transponder is modelled to include a gain element, a soft limiter, and a travelling wave tube amplifier (TWTA); a Shaleh model is used to model the TWTA. The outage probability is determined when the probability of the mutual information random variable is less than the code rate. The outage probability is used as a theoretical bound for maximum capacity. This bound serves as an important benchmark of the achievable rate for the RL. The degree in which M-ary phased shift keying (MPSK) signals using Digital Video Broadcasting — Satellite — Second generation (DVB-S2) forward error correction (FEC) with numerous code rates to achieve this bound is investigated by computer simulation, and also discussed in the paper.

Outage probability analysis of the Protected Tactical Waveform (PTW) on the return link

Adaptive code modulation (ACM) has been studied for last two decades to enhance the bandwidth and power efficiency in a bandwidth-constrained and power-constrained communication system environment. This paper studies how to decide the boundaries of a signal-to-noise ratio (SNR) for the ACM mode selection for a given set of parameters and system model. Also, this paper proposes an efficient and practical algorithm to search the proper ACM mode that meets a target bit error rate (BER) and achieves the maximum data rate. The proposed algorithm is found to be effective under jamming and interference, even if channel and jamming state information (JSI) are unavailable. The results in this paper can be applicable for future satellite and mobile communication system designs against jamming and interference environments.

/pdf/boundaries-of-signal-to-noise-ratio-for-adaptive-code-3rmxpsi9ck.pdf

Boundaries of signal-to-noise ratio for adaptive code modulations

The 2010 Joint Space Communication Layer (JSCL) Initial Capabilities Document (ICD) forecasts a large demand increase for US MILSATCOM in contested environments during the 2020–2025 timeframe. In response, the US Air Force in 2012 commenced the MILSATCOM Design for Affordability Risk Reduction (DFARR) effort to develop prototypes for a new protected tactical communications system. MIT Lincoln Laboratory (MIT LL) was tasked with building a test bed for this effort that would enable demonstration of prototype user terminals and space segment designs provided by DFARR contractor teams. This paper describes the test bed implementation and its use throughout the DFARR, which culminated in system-level over-the-air demonstrations, and risk-reduction demonstrations for a terminal End Cryptographic Unit (ECU) prototype.

Implementation and testing of the Protected Tactical Waveform (PTW)

We propose a hierarchical and heterogeneous multichannel ad hoc network. The channels employed by this network are nonoverlapping, and each channel differs significantly in its characteristics, such as achievable data rate, communication range, and traffic load. Each terminal is equipped with a frequency-agile radio that has the ability to change its carrier frequency and transmission rate over a wide range of possibilities. These radios communicate using contention-based access and are permitted to utilize multiple channels. A subset of the terminals form a backbone network, and are equipped with a second radio tuned to a traffic channel employing schedule-based access. We consider various hierarchical and heterogeneous multichannel ad hoc network topologies and investigate the backbone networks that increase network-layer performance over scenarios in which too few or too many terminals are selected to form the backbone network.

/pdf/investigation-of-mac-for-a-hierarchical-and-heterogeneous-2j1bd2amxf.pdf

Investigation of MAC for a Hierarchical and Heterogeneous Multichannel Ad Hoc Network

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Implementation and testing of the Protected Tactical Waveform (PTW)

Investigation of MAC for a Hierarchical and Heterogeneous Multichannel Ad Hoc Network