2,638 research outputs found
Monitoring cycle design for fast link failure detection in all-optical networks
Fast link failure detection in all-optical networks (AONs) can be achieved using monitoring cycles (m-cycles). An m-cycle is a loop-back optical connection of supervisory wavelengths with a dedicated monitor. Compared to the channel-based or link-based monitoring schemes, m-cycle based schemes require much less number of monitors. In this paper, we propose an ILP (Integer Linear Program) formulation for m-cycle design to minimize the network cost. Our contributions are two-fold: 1) non-simple m-cycles are enabled; and 2) an efficient tradeoff is allowed between the monitor cost and the bandwidth cost. Numerical results show that our algorithm outperforms existing algorithms with a significant performance gain. © 2007 IEEE.published_or_final_versionIEEE Global Telecommunications Conference (GLOBECOM '07), Washington, DC, USA, 26-30 November 2007 p. 2315-231
Asymptotic Mutual Information Statistics of Separately-Correlated Rician Fading MIMO Channels
Precise characterization of the mutual information of MIMO systems is
required to assess the throughput of wireless communication channels in the
presence of Rician fading and spatial correlation. Here, we present an
asymptotic approach allowing to approximate the distribution of the mutual
information as a Gaussian distribution in order to provide both the average
achievable rate and the outage probability. More precisely, the mean and
variance of the mutual information of the separatelycorrelated Rician fading
MIMO channel are derived when the number of transmit and receive antennas grows
asymptotically large and their ratio approaches a finite constant. The
derivation is based on the replica method, an asymptotic technique widely used
in theoretical physics and, more recently, in the performance analysis of
communication (CDMA and MIMO) systems. The replica method allows to analyze
very difficult system cases in a comparatively simple way though some authors
pointed out that its assumptions are not always rigorous. Being aware of this,
we underline the key assumptions made in this setting, quite similar to the
assumptions made in the technical literature using the replica method in their
asymptotic analyses. As far as concerns the convergence of the mutual
information to the Gaussian distribution, it is shown that it holds under some
mild technical conditions, which are tantamount to assuming that the spatial
correlation structure has no asymptotically dominant eigenmodes. The accuracy
of the asymptotic approach is assessed by providing a sizeable number of
numerical results. It is shown that the approximation is very accurate in a
wide variety of system settings even when the number of transmit and receive
antennas is as small as a few units.Comment: - submitted to the IEEE Transactions on Information Theory on Nov.
19, 2006 - revised and submitted to the IEEE Transactions on Information
Theory on Dec. 19, 200
Performance analysis of joint precoding and MUD techniques in multibeam satellite systems
This paper considers interference mitigation techniques in the forward link of multibeam satellite systems. In contrast to previous works, either devoted to receiver interference mitigation (e.g. multiuser detection) or transmitter interference mitigation (precoding), this work evaluates the achievable rates of the joint combination of both techniques. On the one hand, precoding cannot properly mitigate all the inter- beam interference while maintaining a sufficiently high signal-to-noise ratio. On the other hand, the receiver cost and complexity exponentially increases with the number of signals to be simultaneously detected. This highlights that the receiver cannot deal with all the interferences so that in general only 2 signals are jointly detected. As a result, the use of precoding within a coverage area jointly with multiuser detection can both benefit from each other and extremely increase the achievable rates of the system. This is numerically evaluated in a close-to-real coverage area considering simultaneous non-unique decoding strategies. The results show the benefits of this joint scheme that eventually can increase the current precoding performance a 23%.Peer ReviewedPostprint (author's final draft
On the Performance of Millimeter Wave-based RF-FSO Links with HARQ Feedback
This paper studies the performance of hybrid radio-frequency (RF) and
free-space optical (FSO) links in the cases with and without hybrid automatic
repeat request (HARQ). Considering millimeter wave (mmwave) characteristics in
the RF link and pointing errors in the FSO link, we derive closed-form
expressions for the message decoding probabilities as well as the throughput
and the outage probability of the RF-FSO setups. We also evaluate the effect of
various parameters such as power amplifiers efficiency, different transmission
techniques in the FSO link, pointing errors in the FSO link as well as
different coherence times/symbol rates of the RF and the FSO links on the
throughput and outage probability. The results show the efficiency of the
RF-FSO links in different conditions. Moreover, the HARQ can effectively
improve the outage probability/energy efficiency, and compensate the effect of
hardware impairments in RF-FSO links.Comment: Under review in PIMRC'201
Multicell Edge Coverage Enhancement Using Mobile UAV-Relay
Unmanned aerial vehicle (UAV)-assisted communication is a promising technology in future wireless communication networks. UAVs can not only help offload data traffic from ground base stations (GBSs) but also improve the Quality of Service (QoS) of cell-edge users (CEUs). In this article, we consider the enhancement of cell-edge communications through a mobile relay, i.e., UAV, in multicell networks. During each transmission period, GBSs first send data to the UAV, and then the UAV forwards its received data to CEUs according to a certain association strategy. In order to maximize the sum rate of all CEUs, we jointly optimize the UAV mobility management, including trajectory, velocity, and acceleration, and association strategy of CEUs to the UAV, subject to minimum rate requirements of CEUs, mobility constraints of the UAV, and causal buffer constraints in practice. To address the mixed-integer nonconvex problem, we transform it into two convex subproblems by applying tight bounds and relaxations. An iterative algorithm is proposed to solve the two subproblems in an alternating manner. Numerical results show that the proposed algorithm achieves higher rates of CEUs as compared with the existing benchmark schemes
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