Des McLernon

Performance analysis of dual-hop variable gain relay networks over Generalized-K fading channels

In this paper, we develop a new and comprehensive analytical framework for the performance analysis of variable gain dual-hop relay networks over generalized-K fading channels which are typically encountered in composite fading/shadowing environments. We propose a new and generic approach for deriving the closed-form expressions of the ergodic capacity1 of the dual-hop networks with variable gain relays considering a Generalized-K fading and its specific case of Nakagami-m fading. Furthermore, we show that at high average end-to-end signal-to-noise ratio (SNR), the average symbol error probability (ASEP) of the dual-hop variable gain relay network over Generalized-K fading channels can be closely approximated by the sum of the ASEPs of the two same single input single output (SISO) systems. Finally, we also derive a new closed-form expression of the moments of an upper-bound of the end-to-end SNR. Monte-Carlo simulations are also provided in order to validate the analytical framework.

Performance analysis of cooperative communications with opportunistic relaying

In this paper we investigate the performance of proactive opportunistic relaying with amplify-and-forward (AF) protocol over independent and non-identically distributed Generalized Gamma fading channels. The Generalized Gamma distribution is very versatile and accurately approximates many of the commonly used channel scenarios for multipath, shadow and composite fading. We show that opportunistic relaying not only reduces the amount of required resources but also maintains the full diversity order. We derive the novel closed-form expressions for the cumulative distribution function (CDF) and the probability density function (PDF) for the opportunistic relaying scheme operating over independent and non-identically distributed Generalized Gamma fading channels. Moreover the average symbol error rate (SER), for several coherent and noncoherent modulations schemes, as well as the ergodic capacity novel closed-form expressions are also derived in terms of the tabulated Meijers G function. Simulation results are also shown to verify the analytical results.

Time-frequency signature sparse reconstruction using chirp dictionary

This paper considers local sparse reconstruction of time-frequency signatures of windowed non-stationary radar returns. These signals can be considered instantaneously narrow-band, thus the local time-frequency behavior can be recovered accurately with incomplete observations. The typically employed sinusoidal dictionary induces competing requirements on window length. It confronts converse requests on the number of measurements for exact recovery, and sparsity. In this paper, we use chirp dictionary for each window position to determine the signal instantaneous frequency laws. This approach can considerably mitigate the problems of sinusoidal dictionary, and enable the utilization of longer windows for accurate time-frequency representations. It also reduces the picket fence by introducing a new factor, the chirp rate α. Simulation examples are provided, demonstrating the superior performance of local chirp dictionary over its sinusoidal counterpart.

Transmission capacity analysis of cognitive radio networks under co-existence constraints

Cognitive radio networks (CRNs) are envisioned to eradicate the artificial scarcity caused by todays stringent spectrum allocation policy. In this article, we develop a comprehensive statistical framework to study the transmission capacity (TC) of the primary network in the presence of collocated CRN operating under self-coexistence constraint. Considering a system model based on stochastic geometry and the primary beacon enabled interweave spectrum sharing model, outage probability (OP) of a typical primary receiver is studied. Scaling laws for the OP of a typical primary receiver are established. With the help of simulations it is shown that TC of the primary network decreases with increasing number of secondary users and degree of the self-coexistence.

P-Persistent Stabilisation for Wireless Network Diversity Multiple Access Protocols

The network diversity multiple access (NDMA) protocols constitute an innovative way to resolve the packet collisions in wireless random access networks. However, unfavorable joint detection conditions at finite SNR can degrade their throughput performance. To mitigate this problem we propose a p-persistent stabilisation scheme to control the average number of colliding users. The optimum solution for the system parameters - i.e. the probability of false alarm and the parameter p - are given by a set of polynomial equations. A closed-form suboptimal solution, valid for large number of users and low SNR is demonstrated to be asymptotically bounded by the S-ALOHA characteristic. Further, with this new approach the throughput is optimized at the expense of a small delay degradation, and for traffic loads larger than a particular value the solution becomes traffic load independent. System parameters are analyzed by their analytical expressions and by simulations

Performance analysis of K th opportunistic relaying over non-identically distributed cooperative paths

In this paper, we consider the Kth opportunistic relaying based on amplify-and-forward (AF) transmission over independent and non-identically distributed relay channels. In the best relay selection scheme, only the best relay forwards the source message. However, the best relay might be unavailable, so we could possibly resort to the second, third or generally the Kth best relay. We derive the closed-form expressions of symbol error rate and ergodic capacity for the performance analysis of the Kth opportunistic relaying. More specifically, we derive a closed-form expression for the cumulative distribution function (CDF) and the probability density function (PDF) of the end-to-end signal-to-noise ratio (SNR) of the relayed path. Then, we utilize the moment generating function (MGF) approach to find the PDF of the total SNR at the destination. These statistical results are then applied to derive the closed-form expressions for the performance metrics. Our analytical based numerical results are validated by simulations.

Local sparse reconstructions of Doppler frequency using chirp atoms

The paper considers sparse reconstruction of Doppler and microDoppler time-frequency (TF) signatures of radar returns of moving targets from limited or incomplete data. The typically employed sinusoidal dictionary, relating the windowed compressed measurements to the signal local frequency contents, induces competing requirements on the window size. In this paper, we use chirp dictionary for each window position to relax this adverse window length-sparsity interlocking. It is shown that local frequency reconstruction using chirp atoms better represents the approximate piece-wise chirp behavior of most Doppler TF signatures. This enables the utilization of longer windows for accurate time-frequency representations. Simulation examples are provided demonstrating the superior performance of local chirp dictionary over its sinusoidal counterpart.

Closed-form bounds on the ergodic capacity and symbol error probability of the opportunistic incremental relaying protocol

In this paper, we analyze the ergodic capacity (per unit bandwidth) and Average symbol error probability (ASEP) of an incremental relaying protocol used in conjunction with opportunistic relaying and consider a non-regenerative wireless relay network with Rayleigh fading channels. We consider a selection combining technique at the destination in order to combine the two signals, one from the direct path and the other from the best relay path. For a tractable analysis we upper bound the end-to-end signal-to-noise ratio (SNR) and then derive a new closed-form expression of its probability density function (PDF). Utilizing this statistical result we then derive new closed-form lower bounds of ASEP and upper bounds of ergodic capacity over independent and non-identical Rayleigh fading channels. It is shown that the opportunistic incremental relaying (OIR) protocol can considerably improve the ASEP and at the same time (depending upon the channel conditions) also slightly increase (or decrease) the ergodic capacity of the network. The improvement in the performance metrics comes only at the expense of an increase in the networks complexity. Furthermore, it is shown that our derived closed-form bounds are tight in a sense that they match with the exact curves obtained through Monte Carlo simulations and numerical integration techniques.

Ballistic missile precession frequency extraction by homomorphic filtering

In order to extract the precession frequency, which is an important feature parameter in ballistic missile target recognition, we first establish the dynamic Radar Cross Section (RCS) signal model for a conical ballistic missile warhead with precession motion. A homomorphic filter is designed to remove the scintillation effect in the RCS signal. Simulations show the practical usefulness of the proposed method in extracting an estimate of the precession frequency.

Outage and ergodic capacity expressions for fixed-gain relay networks in the presence of interference

In this paper, we analyze the outage and ergodic capacities of a dual-hop cooperative system equipped with a single fixed-gain (also known as semi-blind) relay whilst considering an interference at the relay terminal. We derive the expression for end-to-end signal-to-interference and noise ratio (SINR) of the system under consideration. Using this expression, we then derive new exact closed-form expressions for the outage and ergodic capacities assuming flat Rayleigh fading conditions. Furthermore, new analytical closed-form expressions are derived for the gain of relay which are then used in the numerical simulations. Finally, we also provide the Monte Carlo simulations and show their exact match with our derived closed-form expressions.