Dimitrios Skraparlis

Performance of N-branch receive diversity combining in correlated lognormal channels

Diversity reception techniques combine diversity branches to improve system performance. Fading gains of the diversity branches are correlated lognormal in indoor propagation as well as in systems deploying power control, handovers and dynamic channel allocation. In this letter, novel exact and compact expressions are proposed for the outage probability of N-branch maximal ratio combining (MRC), equal gain combining (EGC) and selection combining (SC) under correlated non-identically distributed lognormal channels. The proposed expressions consist of N-1 nested integrals with favorable numerical properties.

Outage performance analysis of cooperative diversity with MRC and SC in correlated lognormal channels

The study of relaying systems has found renewed interest in the context of cooperative diversity for communication channels suffering from fading. This paper provides analytical expressions for the end-to-end SNR and outage probability of cooperative diversity in correlated lognormal channels, typically found in indoor and specific outdoor environments. The system under consideration utilizes decode-and-forward relaying and Selection Combining or Maximum Ratio Combining at the destination node. The provided expressions are used to evaluate the gains of cooperative diversity compared to noncooperation in correlated lognormal channels, taking into account the spectral and energy efficiency of the protocols and the half-duplex or full-duplex capability of the relay. Our analysis demonstrates that correlation and lognormal variances play a significant role on the performance gain of cooperative diversity against noncooperation.

Outage Performance Analysis of a Dual-Hop Radio Relay System Operating at Frequencies above 10GHz

In order to compress calculation, the background estimation algorithm for the infrared target detection was proposed. Firstly, a Least Square Matrix is proposed and an image background is estimated. Then the target is detected by self-adaptive threshold detection in different images. It is shown by nonlinear function regression experiment and sequence infrared image detection experiment whose methods improve the performance of nonlinear function regression and the infrared background estimation. Experimental results show that this method has good operability and effective suppression of drift and objectives in matching with points of non-rigid deformation, as well as the accuracy of the infrared target detection tracking.The ever increasing demand for multimedia services has led to the extensive use of fixed wireless outdoor networks, where the transmitted information signals arrive to the final destination through a relay node, creating a dual-hop transmission. Due to the increased demand for bandwidth and the spectral congestion at low frequencies, operation at frequencies above 10GHz satisfying the Line-Of-Sight condition is required. At this frequency range, the dominant fading mechanism exposing spatial and temporal stochastic properties is rain attenuation, typically modeled as a lognormal flat fading channel when expressed in dB (log-lognormal in linear scale). In this paper, the outage performance of a dual hop system using several radio relay types is presented and physical prediction models with analytical formulas are proposed, employing spatially correlated lognormal fading channels. Extended numerical results investigate the impact of various operational, geometrical and geographical radio relay parameters, as well as the impact of the employment of a relay channel estimator, on the end-to-end performance.

Cooperative diversity performance of selection relaying over correlated shadowing

Abstract The study of relaying systems has found renewed interest in the context of cooperative diversity for communication channels suffering from fading. In particular, dual-hop relaying with diversity combining of the relayed and direct path at the receiver has practical importance and can be considered as a building block for forming larger communication systems. This paper presents novel analytical expressions and numerical results on cooperative diversity performance using selection relaying over correlated lognormal channels for both SC and MRC techniques at the receiver. In addition, an exact framework for comparing the performance and efficiency of the medium access protocol and relay capabilities (TDMA/half-duplex, SDMA/full-duplex) is proposed. Finally, based on the analysis and novel mathematical expressions for the outage probability, we investigate the impact of the lognormal parameters (including correlation) on the cooperative system performance and its efficiency.

Optimum Placement of Radio Relays in Millimeter-Wave Wireless Dual-Hop Networks [Wireless Corner]

In modern wireless mesh networks, the transmitted-information signals from the source node arrive at the final destination through relay stations. The introduction of relay stations into metropolitan-area networks allows the provision of ubiquitous broadband access, even in remote places, and increases the scalability potential. Due to the increased demand for bandwidth and the spectral congestion at low frequencies, these wireless mesh networks usually operate at frequencies above 10 GHz, satisfying the line-of-sight condition. In this frequency range, the most dominant fading mechanism degrading the availability of radio links and exposing spatial and temporal stochastic variation is rain attenuation. In this paper, the optimum placement of radio relays in a dual-hop configuration is studied, based on physical prediction models for the total outage probability. The focus is on the spatial inhomogeneity of rain attenuation over the converging microwave paths, which leads to the incorporation of the two-dimensional lognormal distribution. The impact of various operational and geometrical properties of adaptive gain transparent and regenerative radio relays on the outage performance and on the optimum relay position for various locations is investigated through a series of extended numerical results.

Cooperative Diversity Performance in Millimeter Wave Radio Systems

The constantly increasing demand for capacity in modern communication systems such as wireless backhaul has led to the employment of frequencies above 10 GHz where the dominant fading mechanism is rain attenuation which is usually modelled as a lognormal random variable (when expressed in dB - log-lognormal in linear scale). In addition, in the context of green communications the use of cooperative diversity techniques can be considered as an important tool which improves the performance, reliability and efficiency of such systems. In this paper, the outage performance analysis of a cooperative system operating at frequencies above 10 GHz is presented, where the propagation medium consists of spatially correlated fading channels. In addition, the energy and spectral efficiency of various multiple-access protocols as well as different relay retransmission and receiver combining techniques are investigated. Moreover, it is proposed that the high correlation coefficient between various rain fading channels can be exploited by the relay to estimate the rain fading of the next hop. Extended numerical results present the impact of various system parameters on the end-to-end performance. Finally, comparison with an energy- and bandwidth- equivalent direct link highlights the system parameter regions where cooperative diversity offers gains over non-cooperation.

On the Effect of Correlation on the Performance of Dual Diversity Receivers in Lognormal Fading

The bivariate lognormal distribution has been extensively utilized for modeling the fading gains of dual branch diversity receivers in both indoor and outdoor communication systems. The contribution of this letter is twofold: firstly, a general expression for the average bit-error probability (BEP) of diversity combining with two correlated lognormal fading branches is presented, based on a Gauss-Hermite sum approximation to the moment generating function. Secondly, using the proposed expression, it is shown that correlation can be viewed as an increase in the standard deviations of an equivalent diversity system with uncorrelated lognormal fading gains.

New Results on the Statistics and the Capacity of Dual-Branch MRC and EGC Diversity in Correlated Lognormal Channels

This letter addresses the performance analysis of dual diversity reception systems in correlated lognormal fading channels with not-necessarily-identical parameters. More specifically, novel results on the probability density function (PDF) and the ergodic capacity of dual-branch maximal ratio combining (MRC) and equal gain combining (EGC) diversity receivers are presented. The proposed expressions find application in cost-sensitive diversity receiver implementations and handover designs.

Cooperation within the Small Cell: The indoor, correlated shadowing case

Abstract The deployment of Small Cells in fourth generation (4G) communication systems is aimed at providing significant capacity improvements and higher availabilities. However, the design of Small Cell systems in indoor environments is especially challenging due to high shadowing attenuation induced by clutter and human blockage. This paper studies node cooperation and multiple relaying and proposes novel analytical formulas for the outage probability of cooperative Small Cells suffering from shadowing. The channel fading gains are modeled as correlated lognormal random variables, in order to reflect the properties of indoor propagation environments. Various cooperative strategies are considered, taking into account the use of one or two relays and different receiver combining techniques. In addition, the relative performance of each cooperative configuration and the benefit of cooperation over non-cooperation are investigated. Finally, interesting and useful insights are produced regarding the impact of the correlated lognormal environment parameters on the configuration of cooperative Small Cells.

Performance of MRC satellite diversity receivers over correlated lognormal and gamma fading channels

Multi-satellite or orbital diversity is an effective technique to reduce the large fading margins in satellite communications under fading conditions. Transmitted signals from multiple angularly-spaced satellites are combined at the terminal station which is equipped with multiple antennas or a single multiple-input (multiple satellite feed - MSF) antenna. Typical signal processing techniques used for diversity combining of the multiple satellite signals are selection combining (SC) and maximal ratio combining (MRC). The subject of this paper is to present physical statistical models for the signal-to-noise ratio distribution as well as a closed-form mathematical expression for the outage probability of dual-satellite orbital diversity with MRC operating under correlated log-normal or gamma fading conditions.