Cid, R.; Naderi, M.Y.; Chowdhury, K.R.; Albert Cabellos-Aparicio; Alarcon, E. IEEE communications letters Vol. 20, num. 12, p. 2554-2557 DOI: 10.1109/LCOMM.2016.2612189 Data de publicació: 2016-12-01 Article en revista
Wireless RF power transfer requires the deployment of multiple energy transmitters (ETs) to cover an entire area of interest. This letter aims at bounding the minimum cumulative power that ETs need to inject into the network, such that the recipient nodes harvest sufficient power to operate. The main findings are that, in the worst case, this scales as O(s1-a/2), where s and a are the number of ETs and the channel path loss. That is, the overall power decreases with the number of ETs. It is also shown that sophisticated design for power transmission can further improve the scalability by s-1.
Virtual data center (VDC) is a key service in modern data center (DC) infrastructures. However, the rigid architecture of traditional servers inside DCs may lead to blocking situations when deploying VDC instances. To overcome this problem, the disaggregated DC paradigm is introduced. In this letter, we present an integer linear programming (ILP) formulation to optimally allocate VDC requests on top of an optically interconnected disaggregated DC infrastructure, aiming to quantify the benefits that such an architecture can bring when compared with traditional server-centric DCs. Moreover, a lightweight simulated annealing-based heuristic is provided for the scenarios where the ILP scalability is challenged. The obtained numerical results reveal the substantial benefits yielded by the resource disaggregation paradigm.
In this letter we focus on the uplink offloading with IP Flow Mobility (IFOM). With IFOM a User Equipment (UE) is able to maintain concurrently two data streams, one through LTE and the other through WiFi. We consider the existence of malicious UEs that aim to exploit the WiFi bandwidth against their truthful peers, in order to upload less data through the energy demanding LTE uplink and a reputation based method is proposed to combat the selfish operation. The WiFi bandwidth is
allocated based on weighted proportional fairness and the LTE rate is defined through an exponential pricing algorithm. We theoretically analyse our approach and evaluate the performance of the malicious and the truthful UEs in terms of energy efficiency and throughput, through simulations. We show that while the malicious UEs present better energy efficiency before being detected, their performance is significantly degraded with the proposed reaction method.
In Software Defined Networking (SDN), the network management is logically centralized but physically distributed among the controllers to improve the scalability compared with a completely centralized model. As an alternative to managing the network state in SDN in a distributed way, this work proposes a distributed protocol called SDN Resource Discovery Protocol (SDN-RDP). This protocol divides and distributes the network management among the controllers. In essence, each controller discovers a portion of the network topology creating a minimum-latency tree rooted at each controller, thus creating the control layer. Through the delay-constrained shortest paths, henceforth called control channels, the controllers collect network state information from nodes, and decide and distribute the forwarding decisions to them. This process is asynchronous since there is no global initialization process to activate the execution of the protocol, and knowledge about the network is not required. Simulation results show that the proposed protocol works efficiently on large networks in terms of time and load.
This letter presents a rule-based solution search
(RBSS) algorithm for self-optimization in a cellular network. It
improves the solution search process of classical optimization
methodologies by including a set of rules that capture the knowledge
of how a given problem can be solved. The results obtained
in a scenario using measurements from a real network reveal that
including the RBSS algorithm achieves reductions of up to 60%
and 90% in the convergence time of Particle Swarm and Genetic
The deployment of a large number of access points in public areas presents a new paradigm in which a given station may be served by more than one access point at a time. Recently, a network model has been proposed to derive the optimal association strategy for the stations by solving a linear optimization problem. According to that model, a station cannot download data while performing a handover. In this letter, we demonstrate that, even in static conditions (i.e., no mobility and constant load in the cell), an association strategy can force a handover. We thus propose a multi-objective optimization function that maximizes the download rates and minimizes the number of handovers. As a handover implies an extra cost due to necessary signaling to be exchanged, we propose a new handover cost function that takes into account the extra bandwidth. Using the new strategy, the system throughput slightly decreases, and the number of handovers is reduced.
New applications require conveying huge bitrate from a source node to multiple destinations. As a result, point-to-multipoint (P2MP) connections need to be established on the optical layer. In this paper, the P2MP routing and spectrum allocation (RSA) problem is formally stated and modelled as an Integer Linear Program (ILP). Exhaustive numerical results show that creating several transparent sub-trees noticeably improves the performance obtained by serving the demand using one single tree. Moreover, cost savings from exploiting traffic asymmetry can be obtained by installing directed optical transponders consisting of one single module.
This letter presents a new and simple model for a
TCP flow experiencing random packet losses due to both trans-
mission errors and congestion events. From this model, we will
derive a straightforward expression of a unified loss probability
(ULP). This ULP gives the opportunity to reuse classical analytic
models to analyze the performance of TCP and to size the buffer to
optimize the wireless link utilization. Extensive simulations using
TCP Reno in ns-2 demonstrate that our model is valid not only for
the extreme cases where either transmission errors or congestion
losses dominate but also in the situations where both types of losses
This letter presents a new and simple model for a TCP flow experiencing random packet losses due to both transmission errors and congestion events. From this model, we will
derive a straightforward expression of a unified loss probability (ULP). This ULP gives the opportunity to reuse classical analytic models to analyze the performance of TCP and to size the buffer to optimize the wireless link utilization. Extensive simulations using TCP Reno in ns-2 demonstrate that our model is valid not only for the extreme cases where either transmission errors or congestion
losses dominate but also in the situations where both types of losses are significant.
Mekikis, P. V.; Lalos, A.; Antonopoulos, A.; Alonso, L.; Verikoukis, C. IEEE communications letters Vol. 18, num. 6, p. 1011-1014 DOI: 10.1109/LCOMM.2014.2320926 Data de publicació: 2014-06 Article en revista
In this letter, we study the performance of network coding (NC)-aided cooperative communications in large scale networks, where the relays are able to harvest energy emitted by wireless transmissions. In particular, we derive theoretical expressions for key network performance metrics, i.e., the probability of successful data exchange and the network lifetime gain. The proposed analytical expressions are verified via extensive Monte Carlo simulations, demonstrating the potential benefits of the energy harvested by the wireless transmissions.
This letter proposes a general packet delivery
mechanism in which routing decisions are taken on the basis
of the identifiers assigned to each node. Such identifiers depend
on the position of each node in the network, and their purpose
is to simplify as much as possible the communication process
between each pair of nodes. The proposal is based on building
trees as the Routing Protocol for Low-Power and Lossy Networks
(RPL), described in RFC 6550, does. Then, each node of the
tree receives a unique identifier following a hierarchical scheme.
Hence, every two nodes of the tree can communicate with each
other performing simple bitwise XOR operations at intermediate
nodes instead of building, storing and maintaining complex
In this Letter, a low-complexity Euclidean distance-based method for antenna subset selection in Spatial Modulation systems is presented. The proposed method avoids the high complexity of both the optimal exhaustive search and of a recently proposed Euclidean distance-based algorithm for performing the selection. Moreover, as the number of receive antennas increases and for practical signal-to-noise ratio (SNR) values, it offers better error performance than the conventional transmit antenna selection (TAS) algorithm. In addition, the benefits of the proposed selection scheme, as the number of receive antennas increases, are further substantiated by comparing its relative energy gain over the TAS method for a target uncoded Symbol Error Rate (SER).
In this Letter, a low-complexity Euclidean distancebased
method for antenna subset selection in Spatial Modulation
systems is presented. The proposed method avoids the high complexity
of both the optimal exhaustive search and of a recently
proposed Euclidean distance-based algorithm for performing
the selection. Moreover, as the number of receive antennas
increases and for practical signal-to-noise ratio (SNR) values, it
offers better error performance than the conventional transmit
antenna selection (TAS) algorithm. In addition, the benefits of
the proposed selection scheme, as the number of receive antennas
increases, are further substantiated by comparing its relative
energy gain over the TAS method for a target uncoded Symbol
Error Rate (SER).
In this letter, we provide a novel theoretical framework for studying the effects of correlated shadowing, in the number of relays that are capable of helping two nodes (sources) to exchange their messages. The relays use network coding to simultaneously transmit the received messages to the sources. We prove theoretically and verify by means of simulations that the average number of relays that are capable of forwarding the network coded message, is independent from any correlation between the links from one source to the relays. Finally, we apply this framework, to compute the network outage probability. The presented results are essential for the theoretical study of medium access control and relay selection protocols designed for network coded cooperative communications.
Botero, J.; Hesselbach, X.; Duelli, M.; Schlosser, D.; Fischer, A.; de Meer, H. IEEE communications letters Vol. 16, num. 5, p. 756-759 DOI: 10.1109/LCOMM.2012.030912.120082 Data de publicació: 2012-05 Article en revista
Waste of energy due to over-provisioning and overdimensioning
of network infrastructures has recently stimulated
the interest on energy consumption reduction by Internet Service
Providers (ISPs). By means of resource consolidation, network
virtualization based architectures will enable energy saving. In
this letter, we extend the well-known virtual network embedding
problem (VNE) to energy awareness and propose a mixed
integer program (MIP) which provides optimal energy efficient
embeddings. Simulation results show the energy gains of the
proposed MIP over the existing cost-based VNE approach.
A new Ordinary Differential Equation (ODE) governing the SNIR evolution of a Successive Interference Canceller (SIC) for DS-CDMA is derived when the number of users tends to infinity and all users share the same channel encoder. Using Variational Calculus, this ODE is applied to obtaining the energy profile that maximizes the average spectral efficiency when a constraint on the power unbalance (maximum power to minimum power ratio) of received users is enforced. The conditions for extremality of the optimum energy profile are established in terms of the common encoder's Packet Error Rate (PER) function.
An expression is derived for the average Packet Error Rate (PER) of a Successive Interference Canceller (SIC) for DS-CDMA when the number of users asymptotically tends to infinity. The asymptotic probability density function of the interference power is governed by a Fokker-Planck differential equation with drift and (asymptotically vanishing) diffusion depending on the PER function of the adopted forward error-correcting code (FEC). In addition to the asymptotic solution for the PER, a particle-based algorithm is also developed for computing efficiently the PER in the finite user case.
We present an analytical model for the maximum
throughput of Bluetooth Low Energy (BLE), considering the
presence of uncorrelated bit errors and the impact of a key
BLE parameter that defines the time between the start of
two consecutive connection events. The derived analysis models
the generic application of master-to-slave unidirectional data
transmission, which also forms an upper bound for bidirectional
data transmission throughput. Simulation results show that our
model accurately predicts the maximum BLE throughput for all
bit error rates and BLE parameter settings evaluated.
Medium access control (MAC) protocols can improve the burst/packet delivery rate in optical burst-switched (OBS) networks. In this letter, the delay analysis of slotted OBS under the use of the DAOBS MAC protocol is proposed. The correctness of the analysis has been assessed through simulation, showing that it achieves a good approximation on different networks despite the operational complexity of the protocol.
This letter proposes a novel and open method for pricing substitute elastic services in a streaming content delivery scenario when their Grade of Service (GoS) is guaranteed. The method forces each Service Provider (SP) to calculate the rate for each substitute service that guarantees the GoS. The price of each service is obtained according to the maximization of a chosen revenue function and the estimation of its demand function. This letter illustrates the method calculating the price of two substitute services with a selected exponential demand function, where the assignation of the prices depend on the maximization of a selected revenue function.
In this letter, we compute the exact probability that a receiver obtains N linearly independent packets among K ≥ N received packets, when the sender/s use/s random linear network coding over a Galois Field of size q. Such condition maps to the receiver's capability to decode the original information, and its mathematical characterization helps to design the coding so to guarantee the correctness of the transmission. Our formulation represents an improvement over the current upper bound for the decoding probability, and provides theoretical grounding to simulative results in the literature.
The routing inaccuracy problem is one of the major
issues impeding the evolution and deployment of Constraint-
Based Routing (CBR) techniques. This paper proposes a promising
CBR strategy that combines the strengths of prediction with
an innovative link-state cost. The latter explicitly integrates a
two-bit counter predictor, with a novel metric that stands for
the degree of inaccuracy (seen by the source node) of the state
information associated with the links along a path. In our routing
model, Link-State Advertisements (LSAs) are only distributed
upon topological changes in the network, i.e., the state and
availability of network resources along a path are predicted
from the source rather than updated through conventional LSAs.
As a proof-of-concept, we apply our routing strategy in the
context of circuit-switched networks. We show that our approach
considerably reduces the impact of routing inaccuracy on the
blocking probability, while eliminating the typical LSAs caused
by the traffic dynamics in CBR protocols.
This paper concentrates on the resilience of the Generalized Multi-Protocol Label Switching (GMPLS) enabled control plane. To this end, the problem of control plane resilience in GMPLS-controlled networks is firstly stated and previous work on the topic reviewed. Next, analytical formulae to quantify the resilience of generic meshed control plane topologies are derived. The resulting model is validated by simulation results on several reference network scenarios.
Alonso-Zárate, J.; Gregoratti, D.; Giotis, P.; Verikoukis, C.; Alonso, L. IEEE communications letters Vol. 13, num. 7, p. 495-497 DOI: 10.1109/LCOMM.2009.081502 Data de publicació: 2009-07 Article en revista
The analysis of an access priority mechanism for a high-performance medium access control (MAC) protocol, the distributed queueing MAC protocol for wireless ad hoc networks (DQMAN), is presented in this letter. DQMAN is comprised of a hierarchical, dynamic, and spontaneous master-slave clustering algorithm together with an embedded tree-splitting collision resolution algorithm based on access mini-slots. The responsibility of being master entails extra functionality, and thus extra energy consumption. Therefore, this responsibility must be shared in a dynamic manner among all the stations of the network in order to ensure fairness in the system. By allowing those stations acting as master stations to avoid contention to get access to the channel, their average packet transmission delay can be effectively reduced compared to that of slave stations. Consequently, stations may be encouraged to operate in master mode regardless of the extra functions they may have to carry out. We analyze in this letter the reduced average packet transmission delay for masters.
Klinkowski, M.; Pioro, M.; Careglio, D.; Marciniak, M.; Solé-Pareta, J. IEEE communications letters Vol. 11, num. 12, p. 1016-1018 DOI: 10.1109/LCOMM.2007.071311 Data de publicació: 2007-12 Article en revista
Optical Burst Switching (OBS) architectures without buffering capabilities are sensitive to burst losses. A proper routing strategy may help to reduce such congestion. In this letter we present a novel approach for OBS multi-path source routing problem. Our solution is based on non-linear optimization with a straightforward calculation of partial derivatives. Simulation results demonstrate that optimized routing effectively reduces the overall burst loss probability with respect to shortest path and
Within the generalized multi-protocol label switching (GMPLS), link management protocol (LMP) has been proposed to maintain the connectivity of the out-of-fiber control plane. In this paper, we analytically quantify the impact of control plane link failures on whole network performance. Then, we use the obtained results to suggest the keep-alive interval for LMP, introducing the least overhead to the control network while keeping an acceptable network grade of service (GoS).
In this letter, we propose two novel mechanisms which enable GMPLS LMP to cope with the automatic discovery of all-optical transport planes. The feasibility of our contributions and their performances are assessed by simulations as well as experimental results over the ASON/GMPLS CARISMA field-trial.
This letter presents a BS selection criterion for WCDMA that allows selecting the base station requiring the minimum transmission power in both the uplink and downlink direction. The importance of minimizing transmitted power lies on the associated interference reduction and, consequently, the capacity increase. Furthermore, it is shown that, with a proper setting of the parameters, the criterion used in practical WCDMA systems based on Ec/Io measurements can be adjusted to provide results similar to the proposed method.
Mobile communications systems often work under high heterogeneous conditions, both in time and space domains. This fact makes the proper design of the network infrastructures very important, specially the radio access part. Optimizing this design is a technical and economical challenge. On the other hand, active repeaters are of special interest when considering the deployment of the coverage of a mobile communications system in a certain set of situations that include, but are not limited to: Inside big buildings, tunnels, or any place where the propagation losses are high, open areas where there are time limited very high demand peaks (stadiums, expositions, etc), remote sites, normally in rural areas, where the service demand is widely spread in space domain, suburban areas, near big urban cities, and roads and railroads.
This paper analyzes the performance of a MAC scheme for wireless local area networks (WLANs) that makes use of distributed queues to improve radio channel utilization. Analytical values for the maximum throughput performance are derived as a function of the system parameters. The obtained results show that the proposed scheme outperforms the legacy 802.11 MAC protocol in terms of maximum stable throughput. This benefit is obtained from eliminating back-off periods and collisions in data packet transmissions while minimizing the needed control overhead. The proposal also makes performance to be independent of the number of nodes transmitting in the system and provides stability for high load conditions.
Analytic expressions have been derived for the probability density functions of the total signal-to-interference ratio when considering mixed-type interference sources in the reverse link of a DS/CDMA packet radio system with Rayleigh fading. Four different scenarios were studied, and the corresponding expressions are presented for each situation. The users are divided into two groups: those that apply a closed-loop power control and those that only use an open-loop power control. By making use of these expressions, the mean block error probability is derived as a function of the number of total interfering users in each group.