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Publications (131)
In this paper, the performance of different mathematical models for the joint connection-level and packet-level numerical evaluation of systems with Voice over Internet Protocol (VoIP) traffic are studied and compared. The evaluation focuses on computational running time, memory requirements, and accuracy of performance metrics. System dynamics are...
In this paper, both the achievement and practical implementation of a fractional number of servers in queueing systems is proposed. The Erlang-B traffic model is considered to demonstrate how the fractional number of servers can be physically realized and incorporated into teletraffic analysis. While mathematical extensions of the Erlang-B formula...
Cell dwell time (DT) and unencumbered interruption time (IT) are fundamental time interval variables in the teletraffic analysis for the performance evaluation of mobile cellular networks. Although a diverse set of general distributions has been proposed to model these time interval variables, the effect of their moments higher than the expected va...
Abstract In this paper, dynamic and anticipated resource leasing strategies to address the problem of leased resource availability are investigated. Then, network performance analysis is developed, and the performance evaluations of different leasing strategies (namely permanent, dynamic, and anticipated leasing strategies) are provided for some ne...
Cognitive radio technology was developed for spectral efficiency improvement in mobile communication networks. This is achieved by allowing secondary users to opportunistically and transparently use the white spaces of the primary network. In this paper, the effect of the service time distribution of the primary users in the statistics of the white...
This article studies the performance of a wireless sensor network with cognitive radio capabilities to gather information about structural health monitoring of buildings in case of seismic activity. Since the use of the local area network is intensive in office and home environments, we propose the use of empty cellular channels (primary system). A...
In this paper, the Erlang capacity achieved by the separate or joint use of several resource management mechanisms commonly considered in the literature (spectrum aggregation, spectrum adaptation, call buffering, channel reservation, selective interruption, and preemptive prioritization) to mitigate the effects of secondary call interruptions in co...
In this paper, teletraffic performance and channel holding time characterization in mobile cognitive radio cellular networks (CRCNs) under fixed-rate traffic with hard-delay constraints are investigated. To this end, a mathematical model to capture the effect of interruption of ongoing calls of secondary users (SUs) due to the arrival of primary us...
In this paper, a novel call admission control (CAC) strategy for a buffered cognitive radio network (CRN) with voice over Internet Protocol (VoIP) traffic is proposed. The main idea of the proposed CAC strategy relies on reducing the weight of the current number of secondary VoIP sessions in the admission/rejection decision criterion, which can pot...
In this paper, dynamic spectrum leasing strategies (with and without anticIPated resource leasing) for coordinated cognitive radio networks with delay-tolerant (best effort) traffic are proposed and analyzed to mitigate the effects of unpredictable resource availability. To exploit the tolerance to delay a buffer for preempted secondary calls is co...
In this paper, dynamic spectrum leasing strategies (with and without anticipated resource leasing) for coordinated cognitive radio networks are proposed to mitigate the effects of unpredictable resource availability. It is shown that anticipated resource leasing is an effective mechanism to increase the possibility to have available resources when...
Due to the unpredictable nature of channel availability, carrying delay-sensitive traffic in cognitive radio networks (CRNs) is very challenging. Spectrum leasing of radio resources has been proposed in the so called coordinated CRNs to improve the quality of service (QoS) experienced by secondary users (SUs). In this paper, the performance of coor...
In this paper, a novel joint connection-level and packet-level analytical model for the performance evaluation of cognitive radio networks (CRNs) under VoIP traffic is proposed and developed. The proposed teletraffic model captures the most relevant features of both CRNs (i.e., unreliable spectrum sensing, primary users' activity detection) and VoI...
In this paper, the performance of VoIP traffic-based cognitive radio networks ( CRNs) with different primary channel holding time (CHT) distribution (specifically, negative exponential, log-normal, and Coxian) is investigated. From the mathematical point of view, a joint connection level and packet level analysis considering the primary CHT to be C...
In this paper, the performance of spectrum adaptation in cognitive radio networks (CRNs) with elastic traffic is analytically evaluated. Contrary to most of the previously published related works on spectrum adaptation in CRNs, in this paper both call buffering and unencumbered service time with non-exponential probability distribution are consider...
Due to the unpredictable nature of channel availability, supporting the quality of service (QoS) of stringent delay sensitive traffic in cognitive radio networks (CRNs) is very challenging. Stringent delay sensitive calls in CRNs are susceptible to forced termination due to the preemptive resource occupancy priority of primary users. To enable more...
In cognitive radio networks (CRNs) based on spectrum overlay sharing, the connection of a secondary user fails when a primary user arrives and there is not idle channels. Retransmissions of interrupted secondary sessions may lead the system towards an unstable condition. Therefore, it is important to develop mechanisms to alleviate performance degr...
Guaranteeing QoS is challenging in cognitive radio networks due to the dynamically changing network resources, especially for stringent delay sensitive traffic. Dynamic spectrum leasing (and coordinated cognitive radio) of primary network resources has been previously proposed in the literature to improve QoS of secondary users. In this paper, the...
In the literature, Poisson or ON/OFF models have been commonly used to characterize the primary arrival process in cognitive radio networks (CRNs). In this paper, the performance analysis of CRNs with VoIP traffic considering either Poisson or ON/OFF models for the primary arrival characterization is evaluated and compared. To provide a fair basis...
in this letter a general admission control strategy is proposed and mathematically analized. Fractional biffering finely adjusts different QoS metrics allowing them to simultaneously achieve their maximum acceptable values, maximizing system capacity. Fractional buffering also allows the adequate and fair performance comparison among different reso...
In this paper, a simplified joint call and packet level teletraffic analysis method for performance evaluation of call admission control (CAC) strategies for voice over IP (VoIP) traffic over wireless access networks is proposed. The admission criterion of new sessions of the considered CAC strategies is based on either the total number of sessions...
In this paper, the relevance of considering the primary network resource occupancy information on the admission criterion of new secondary VoIP sessions in cognitive radio networks (CRNs) is investigated. In particular, the performance of two different call admission control (CAC) strategies whose admission criterion is based either on the total nu...
In this paper, channel reservation to prioritize ongoing
secondary users’ (SUs) calls over new SUs’ requests in cognitive
radio networks (CRNs) with delay tolerant traffic and the
RESTART (also known as preemptive repeat identical)
retransmission strategy is analyzed and evaluated. Additionally,
an analytical approach to approximately evaluate the...
Call admission control (CAC) functionality is a critical requirement for guarantee the desired quality of service (QoS) for voice calls in IP-based wireless networks. In this paper, three different CAC strategies for voice over IP (VoIP) traffic over wireless access networks with packet buffering are mathematically analyzed through a joint call and...
In this paper, the performance of cognitive radio networks under Resume (RR) and Restart (RS) retransmission strategies for interrupted secondary calls is investigated. System performance is analyzed and evaluated in terms of secondary users' blocking probability and mean transmission delay. For the RR strategy, a trellis-based mathematical analysi...
In this paper, the performance of cognitive radio networks (CRNs) considering either Poisson or ON/OFF models for the primary users' arrivals is evaluated and compared. These primary arrival models have been commonly used for the teletraffic analysis of CRNs in the literature. However, the performance of CRNs under these arrivals models has not bee...
In this paper, a general teletraffic analysis to evaluate the performance of cognitive radio networks with arbitrary order Coxian distributed channel holding time in the primary network is developed. The relevance of the considered Coxian model relies on its universality property, mathematical tractability, reduced dimensionality, and the fact that...
Even though degraded link condition due to the excessive intra-cell co-channel interference is the major cause of dropping calls in SDMA mobile cellular systems, most of the published system level studies have not considered co-channel interference as a cause of call forced termination. To include the effect of co-channel interference at system lev...
Channel holding time is fundamental for the performance analysis/evaluation of mobile cellular networks. Channel holding time depends on both call holding time and cell dwell time. In the literature, many assumptions on cell dwell time distribution have been done and different channel holding time characteristics have been obtained. However, to our...
In this paper, two analytical approaches to approximately calculate the access (at connection level) waiting time distribution for an OFDMA-based wireless cellular system with finite buffering under First-Come, First-Served (FCFS) discipline and Adaptive Modulation and Coding (AMC) are proposed. It has been demonstrated in previous published works...
In this paper, under the assumption that the unencumbered service time is exponentially distributed, a novel algebraic set of general equations that examines the relationships between cell dwell time (CDT) and residual cell dwell time as well as between cell dwell time and channel holding time (CHT) are derived. This work includes relevant new anal...
In this paper, sensitivity of the first three standardized moments of both unencumbered call interruption time and cell dwell time on teletraffic performance metrics of wireless cellular networks is investigated. Mathematical analysis for obtaining system-level performance metrics is developed considering that cell dwell time and unencumbered call...
In this paper, the Coxian distribution model to characterize users' mobility (through cell dwell time) is proposed and its application for the teletraffic analysis of mobile cellular networks is presented. To the best authors' knowledge, Coxian distribution has not been previously considered in the literature to characterize users' mobility in cell...
In this paper, probability distributions of new and handoff call channel holding times in mobile cellular networks are derived under the assumption that cell dwell time has generalized Coxian distribution. It is shown that when cell dwell time has a generalized Coxian distribution, the resulting residual cell dwell time has generalized Coxian distr...
Abstract-In this paper, a teletraffic model to analyze wireless mobile cellular networks with hyper-Erlang distributed cell dwell time is developed. We demonstrate that the residual cell dwell time is also hyper-Erlang distributed with a greater number of stages. More important, it is shown that the phases on each stage of the hyper-Erlang distribu...
Reuse Partitioning has been recently proposed as an effective inter-cell interference mitigation strategy for OFDMA cellular networks. However, mobility of users has been largely ignored in the system level analysis of these systems. To fill this void, in this paper, a teletraffic analysis of a Reuse Partitioning (RP) system is conducted in order t...
In this paper, a teletraffic analysis method based on channel holding time statistics for new and handoff calls for system level performance evaluation of mobile cellular networks with link unreliability is developed. Firstly, mathematical expressions for the probability distribution function of channel holding time for new and handoff calls are de...
In the literature, SDMA cellular networks have been studied from system level point of view by means of teletraffic analysis considering the resource assignment and users' mobility related quantities (i.e., beam overlapping time and beam overlapping rate) based only on geometrical considerations. However, the effect of realistic users' mobility, ch...
In this paper, the waiting time analysis for an OFDMA wireless cellular system with finite buffering and Adaptive Modulation and Coding (AMC) is addressed. When AMC is considered, several concentric regions within cells serving users with different data rates are differentiated. Phase type (PHT) distribution functions are used to model the conditio...
Traditionally, system-level performance evaluation of mobile wireless communication networks has been addressed by only considering resource insufficiency, whereas the effect of an unreliable wireless channel has largely been ignored because of the complexity that its inclusion entails. To fill this void, a general analytical model for the system-l...
In this paper, a novel prioritization mechanism for random access strategies in cellular networks is proposed. The proposed prioritized random access strategy sets different retransmission probabilities to users, depending on their priorities. First, a mathematical analysis method for simultaneously evaluating throughput and access delay, consideri...
Propagation loss is a fundamental phenomenon that affects the performance of any wireless network. Although propagation characteristics in line-of-sight (LOS) microcellular systems are well known, so far, only a few papers have investigated its effect on system performance in a comprehensive manner. In this paper, the impact of both system paramete...
In delay- and disruption-tolerant wireless communication networks, capacity is commonly traded off for delay. That is the case of spatial intermittent connectivity (SIC) networks. SIC networks are designed to provide high data rates to mobile nodes in small disjoint geographical areas. However, because of userspsila mobility, these high data rates...
In this paper, statistical characterization of link unreliability in cellular networks at system level is addressed. Traditionally, system-level performance evaluation of mobile wireless communication networks has been performed by considering only resource insufficiency, while the effect of unreliable wireless channel has been largely ignored. Rec...
Teletrafflc modeling of mobile communication networks has been commonly addressed by considering only resource insufficiency, while the effect of the unreliability nature of wireless channels has been largely ignored because of the complexity involved in its study. To fill this void, a general analytical model for the system level performance evalu...
A teletraffic analysis for the performance evaluation of the joint use of dynamic resource allocation (DRA), channel de-allocation (DAS), and channel re-allocation (RAS) strategies in GSM/GPRS networks is developed. In addition, an efficient DRA strategy with a link quality awareness policy, channel de-allocation and re-allocation policies as well...
A new call admission control (CAC) strategy based on the soft capacity constraint (SCC) concept is proposed for CDMA cellular systems. The use of the SCC concept allows maximizing system capacity while at the same time meeting the quality of service (QoS) requirements in terms of the outage probability. The fractional channel reservation (FCR) sche...
In this paper, the mobility/capacity conversion (MCC) efficiency of reuse-based resource management strategies in multi-service wireless communication networks is mathematically analyzed. In particular, a useful and efficient resource management strategy is proposed and evaluated. The proposed strategy exploits the synergy between the maximum packi...
In this paper, a mathematical analysis method to simultaneously evaluate throughput and access delay considering an infinite population model is considered. Most of the previous related research has been done considering both finite population and saturation conditions where all the nodes in the system have always a packet ready to be transmitted a...
In this paper, a new system level approach for modeling wireless channel unreliability in CDMA cellular systems is proposed. The analysis takes into account call connection types (i.e., soft handoff or single base station) and their respective link reliabilities, which according to some measurements in real cellular networks reported in the literat...
A new mathematical method to analyse the performance of guard-channel-based strategies is proposed. The analysis is based on the iterative calculation of the average effective channel holding time. The method presented provides higher accuracy than alternative solutions previously reported in the literature
A queueing model for the system level performance evaluation of mobile cellular networks considering both resource insufficiency
and wireless channel unreliability is proposed and mathematically analyzed. The proposed mathematical approach is based on
the use of simple call interruption processes to model the effect of wireless channel unreliabilit...
In this paper, the performance of three different fair resource allocation strategies for packet data transmission in wireless networks with link adaptation (LA) is mathematically analyzed. The strategies aim at achieving fair access, fair transmission rate or simultaneous fair access and transmission rate. As a case study, the performance of the c...
In this letter, closed-form non-recursive expressions for the probability mass function (pmf) of the access delay are addressed. As the exact non-recursive expression for the pmf of the access delay are typically complex and have high computational requirements, Gaussian approximations are derived for the uniform, binary exponential and geometric b...
In this paper, a new system level approach for the wireless channel unreliability modeling is proposed. Firstly, in order to characterize the call interruption process due to the wireless channel unreliability, the Gilbert-Elliot model is used to obtain the probability distribution of the interruption time. Then, it is shown that link unreliability...
In this paper, the performance of mobile cellular systems with link adaptation (LA) is analytically evaluated. Half- and full-rate vocoders are considered in the analysis. Mathematical expressions for the new call blocking, handoff failure, and forced termination probabilities are obtained. To our knowledge, no similar analysis considering LA exist...
In this paper, the performance of three fair resource allocation strategies for packet data transmission in EDGE/GPRS networks are mathematically analyzed. The strategies aim at achieving, respectively, fair access, fair transmission rate and, simultaneous fair access and transmission rate. The differences in terms of QoS and GoS caused by link ada...
In this letter, recursive formulas for the new call blocking and handoff failure probabilities for Fractional Guard Channel (FGC) policies in cellular networks are derived. The effect of users' mobility on the maximum system capacity achieved with the Guard Channel (GC), the Limited Fractional Guard Channel (LFGC), and the Uniform Fractional Guard...
In this paper, call admission and code allocation schemes are proposed to provide service differentiation in the forward link of wideband code-division multiple-access (WCDMA) systems. In particular, this paper proposes multiple leaf code reservation (MLCR) schemes, where different numbers of orthogonal variable spreading factor (OVSF) leaf codes (...
This chapter focuses on call-level Quality-of-Service (QoS) measures, and the new call blocking and forced termination probabilities are considered the relevant QoS metrics. The proportion of new call requests that are denied service is known as the new call blocking probability Pb. The forced termination probability, on the other hand, is defined...
In this paper we propose different backoff algorithms for different classes of users. Namely, throughput sensitive users that can support higher delays but do not support a high number of retransmissions, and delay sensitive users that need to transmit their information in a time constrained base and can support a high number of retransmissions. Th...
In this paper, a novel mathematical approach to evaluate the performance of adaptive or flexible resource allocation (FRA) strategies with uniform quality of service (QoS) provisioning in multiservices wireless cellular networks, in terms of the call blocking probabilities and transmission delay, is proposed. FRA strategies improve channel utilizat...
In this paper, three random access control mechanisms based on the well-known Slotted ALOHA, NP-CSMA, and 1P-CSMA protocols are presented. The basic idea is to limit the number of transmissions and retransmissions at high traffic loads in order to minimize collisions while keeping system stability. A new medium-access control protocol called Adapti...
In this paper, the performance of dynamic resource allocation and channel de-allocation in integrated voice/data wireless networks with link adaptation is mathematically analyzed and evaluated. To our knowledge, all previous related works published in the literature have considered only link adaptation (LA) or dynamic resource allocation (DRA) sepa...
One-dimensional recursive formulas to calculate the blocking probabilities of the different call types in multi-service mobile cellular networks using the multiple fractional channel reservation (MFCR) strategy are derived. MFCR achieves practically the same performance as the optimum call admission control policy in multi-service mobile cellular n...
In mobile cellular systems with link adaptation (LA), different quality zones, in terms of the signal-to-interference ratio (SIR), can be distinguished within each cell. In this paper, the effects of the inter-cell and intra-cell handoff hysteresis margins and log-normal shadowing on the residence time in the different quality zones in mobile cellu...
Different cellular systems with different resource management strategies have similar residence time characterization due to geometrical similarities. In such systems, different quality zones, in terms of the signal-to-interference ratio, are distinguished inside each cell. In this paper, the functional relationship between the cell residence time...
The capacity maximization of integrated voice/data wireless cellular communication systems with link adaptation (LA) is addressed using the GSM/GPRS system as a case study. Only coding schemes CS-1 and CS-2 are used. Two different quality zones differentiated by signal quality are used and mapped to the two coding schemes. Data users in the good qu...
We make a performance evaluation of the air interface system EDGE (enhanced data rate for GSM evolution) introducing the adaptive traffic load (ATL) S-ALOHA as the random access protocol. The EDGE system originally considers the S-ALOHA random access protocol to let users access the network for transmitting their data packets. However, S-ALOHA beco...
Flexible resource-allocation (FRA) strategies have been proposed in the literature to mitigate the high blocking rate caused in high-speed mobile communication networks when resource aggregation is used to increase the data rate. In this paper, new FRA strategies that cope with scenarios with multiple service types and multiple priorities are propo...