3,528 research outputs found
Unified Performance Analysis of Mixed Line of Sight RF-FSO Fixed Gain Dual-Hop Transmission Systems
In this work, we carry out a unified performance analysis of a dual-hop fixed
gain relay system over asymmetric links composed of both radio-frequency (RF)
and unified free-space optics (FSO) under the effect of pointing errors. The RF
link is modeled by the Nakagami- fading channel and the FSO link by the
Gamma-Gamma fading channel subject to both types of detection techniques (i.e.
heterodyne detection and intensity modulation with direct detection (IM/DD)).
In particular, we derive new unified closed-form expressions for the cumulative
distribution function, the probability density function, the moment generation
function, and the moments of the end-to-end signal-to-noise ratio of these
systems in terms of the Meijer's G function. Based on these formulas, we offer
exact closed-form expressions for the outage probability, the higher-order
amount of fading, and the average bit-error rate of a variety of binary
modulations in terms of the Meijer's G function. Further, an exact closed-form
expression for the end-to-end ergodic capacity for the Nakagami--unified FSO
relay links is derived in terms of the bivariate G function. All the given
results are verified via Computer-based Monte-Carlo simulations
Cross-Layer Optimization of Fast Video Delivery in Cache-Enabled Relaying Networks
This paper investigates the cross-layer optimization of fast video delivery
and caching for minimization of the overall video delivery time in a two-hop
relaying network. The half-duplex relay nodes are equipped with both a cache
and a buffer which facilitate joint scheduling of fetching and delivery to
exploit the channel diversity for improving the overall delivery performance.
The fast delivery control is formulated as a two-stage functional non-convex
optimization problem. By exploiting the underlying convex and quasi-convex
structures, the problem can be solved exactly and efficiently by the developed
algorithm. Simulation results show that significant caching and buffering gains
can be achieved with the proposed framework, which translates into a reduction
of the overall video delivery time. Besides, a trade-off between caching and
buffering gains is unveiled.Comment: 7 pages, 4 figures; accepted for presentation at IEEE Globecom, San
Diego, CA, Dec. 201
Performance analysis of mixed Nakagami- m and Gamma–Gamma dual-hop FSO transmission systems
In this paper, we carry out a unified performance analysis of a dual-hop relay system over the asymmetric links composed of both radio-frequency (RF) and unified free-space optical (FSO) links under the effect of pointing errors. Both fixed and variable gain relay systems are studied. The RF link is modeled by the Nakagami-m fading channel and the FSO link by the Gamma-Gamma fading channel subject to both types of detection techniques (i.e., heterodyne detection and intensity modulation with direct detection). In particular, we derive new unified closed-form expressions for the cumulative distribution function, the probability density function, the moment generating function (MGF), and the moments of the end-to-end signal-to-noise ratio (SNR) of these systems in terms of the Meijer's G function. Based on these formulas, we offer exact closed-form expressions for the outage probability (OP), the higher order amount of fading, and the average bit error rate (BER) of a variety of binary modulations in terms of the Meijer's G function. Furthermore, an exact closed-form expression of the end-to-end ergodic capacity is derived in terms of the bivariate G function. Additionally, by using the asymptotic expansion of the Meijer's G function at the high-SNR regime, we derive new asymptotic results for the OP, the MGF, and the average BER in terms of simple elementary functions
Network Formation Games Among Relay Stations in Next Generation Wireless Networks
The introduction of relay station (RS) nodes is a key feature in next
generation wireless networks such as 3GPP's long term evolution advanced
(LTE-Advanced), or the forthcoming IEEE 802.16j WiMAX standard. This paper
presents, using game theory, a novel approach for the formation of the tree
architecture that connects the RSs and their serving base station in the
\emph{uplink} of the next generation wireless multi-hop systems. Unlike
existing literature which mainly focused on performance analysis, we propose a
distributed algorithm for studying the \emph{structure} and \emph{dynamics} of
the network. We formulate a network formation game among the RSs whereby each
RS aims to maximize a cross-layer utility function that takes into account the
benefit from cooperative transmission, in terms of reduced bit error rate, and
the costs in terms of the delay due to multi-hop transmission. For forming the
tree structure, a distributed myopic algorithm is devised. Using the proposed
algorithm, each RS can individually select the path that connects it to the BS
through other RSs while optimizing its utility. We show the convergence of the
algorithm into a Nash tree network, and we study how the RSs can adapt the
network's topology to environmental changes such as mobility or the deployment
of new mobile stations. Simulation results show that the proposed algorithm
presents significant gains in terms of average utility per mobile station which
is at least 17.1% better relatively to the case with no RSs and reaches up to
40.3% improvement compared to a nearest neighbor algorithm (for a network with
10 RSs). The results also show that the average number of hops does not exceed
3 even for a network with up to 25 RSs.Comment: IEEE Transactions on Communications, vol. 59, no. 9, pp. 2528-2542,
September 201
Wireless Video Transmission with Over-the-Air Packet Mixing
In this paper, we propose a system for wireless video transmission with a
wireless physical layer (PHY) that supports cooperative forwarding of
interfered/superimposed packets. Our system model considers multiple and
independent unicast transmissions between network nodes while a number of them
serve as relays of the interfered/superimposed signals. For this new PHY the
average transmission rate that each node can achieve is estimated first. Next,
we formulate a utility optimization framework for the video transmission
problem and we show that it can be simplified due to the features of the new
PHY. Simulation results reveal the system operating regions for which
superimposing wireless packets is a better choice than a typical cooperative
PHY.Comment: 2012 Packet Video Worksho
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