In this paper, the performance of the toroidal cellular simulation structure under users' mobility, time-varying traffic, and dynamic channel assignment is evaluated. The toroidal cellular simulation structure has been proposed to effectively eliminate the so called edge effect (elimination of the inflow/outflow of handoff traffic streams to/from the examined area). However, in the toroidal cellular simulation structure appears the so called wrapping effect (the effect of an event at a cell may ripple back to that cell through chains of adjacent cells). Both the edge and wrapping effects may significantly bias performance modeling of wireless mobile systems. The wrapping effect effectively disappears as the number of considered cells in the cellular mesh structure increases. The effect of users' mobility factor and burstiness of new call arrivals on the system performance are evaluated as function of the total number of considered cells in the cellular mesh structure for fixed and dynamic channel assignment strategies. Numerical results of the different performance metrics show that for most of the considered evaluation scenarios, simulation results are close to the convergence value with a toroidal cellular structure of 37 cells (i.e., four rings of cells).

In this paper, the performance of heterogeneous traffic Cognitive Radio Networks (CRNs) with spectrum adaptation and spectrum leasing is mathematically analyzed and evaluated. Spectrum adaptation and spectrum leasing are used jointly with spectrum handoff, call buffering, and preemptive priority mechanisms to improve system performance. Two different spectrum leasing strategies are proposed and evaluated. Service differentiation between real-time and elastic (data) traffic is considered according to their different delay tolerance characteristics. For given quality of service (QoS) requirements, the Erlang capacity as a function of the maximum allowable number of simultaneously rented resources is evaluated. Additionally, the fraction of time that rented resources are needed is calculated. This quantity is used to estimate the cost of spectrum leasing per capacity Erlang. Numerical results demonstrate that resource leasing is an effective strategy to drastically improve system capacity and avoids the existence of the critical utilization factor of the primary resources (i.e., value of the primary resource utilization factor from which it is no longer possible to guarantee QoS in CRNs). Finally, by prioritizing the use of rented resources for service requests with stringent delay requirement, the cost for spectrum lease can be minimized.

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 potentially allow more efficient spectrum usage. To show this, the maximum VoIP Erlang capacity achieved by the proposed CAC strategy is calculated. Compared to the conventional (occupancy-based) CAC strategy, our proposed "differentiated resource occupancy-aware" CAC scheme increases Erlang capacity without an important increase in the system complexity cost. This indicates that in a CRN with VoIP traffic, system capacity not only depends on the total number of busy channels but also on the proportion of busy channels that are used by primary users.

Interruption of ongoing calls of secondary users (SUs) due to the arrival of primary users (PUs) is one of the most relevant factors that degrade both quality of service and system throughput in cognitive radio networks (CRNs). In this paper, the Erlang capacity achieved by different resource management mechanisms previously proposed in the literature to mitigate the effects of call interruptions is evaluated and compared when they are employed separately in cognitive radio networks (CRNs) with heterogeneous traffic. This evaluation is done to identify the most relevant mechanisms to improve the performance of these networks. Also, strategies that jointly employ different resource management techniques and spectrum adaptation to exploit the synergy of the different mechanisms are proposed and evaluated. The aim of the proposed spectrum allocation strategy is to take advantage of the flexibility and delay tolerance features of elastic traffic. Additionally, a mathematical model for the performance analysis of the proposed strategies in CRNs with heterogeneous traffic is developed. Numerical results demonstrate that call buffering and adaptive spectrum mechanisms in heterogeneous traffic CRNs can significantly improve overall system performance by efficiently exploiting the elasticity of delay-tolerant traffic.

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 considered. From the mathematical point of view, our contribution is to develop a teletraffic model for the performance evaluation of the proposed strategies. The tradeoff between the spectrum leasing cost and system Erlang capacity is also investigated. For a given maximum allowed number of simultaneously rented channels and Quality of Service (QoS) requirement in terms of new call blocking probability, maximum Erlang capacity is obtained for different traffic scenarios. Numerical results reveal that system performance strongly depends on the value of the mean secondary channel holding time relative to the mean primary channel holding time. Finally, the cost per capacity and mean transmission delay as a function of both the utilization factor of the primary resources and the maximum allowed number of simultaneously rented channels is evaluated. It is shown that anticipated resource leasing is an effective mechanism to increase the possibility to have available resources when needed for the secondary network.

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 needed for the secondary network. Additionally, to finely control the provided quality of service, fractional channel reservation to prioritize ongoing secondary calls over new ones is considered. A teletraffic mathematical analysis for the performance evaluation of the proposed strategies is developed. The tradeoff between the spectrum leasing cost and the system Erlang capacity is also investigated. For a given maximum allowed number of simultaneously rented channels, maximum Erlang capacity is obtained by optimizing the number of reserved channels for different traffic scenarios. Numerical results reveal that system performance strongly depends on the value of the mean secondary service time relative to the mean primary service time. Finally, the cost per capacity a function of both the utilization factor of the primary resources and the maximum allowed number of simultaneously rented channels is evaluated.

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 VoIP traffic (i.e., ON/OFF activity processes for individual VoIP sessions, periodic packet generation of individual VoIP sessions in the ON state). In addition, our mathematical model captures relevant aspects of multiuser VoIP-based networks such as the use of packet buffering, adaptive modulation coding, proportional fair sharing scheduling for secondary users with different link qualities, and call admission control (CAC). Our mathematical analysis is based on the time-scale decomposition technique and employs conventional discrete time Markov chain tools. However, the most important feature of our mathematical formulation is the introduction of the so called cross-level analysis methodology used here to link packet-level and connection-level analyses. This proposed methodology allows to use time-scale decomposition technique when it is no longer possible to perform the connection level analysis in an independent manner from the packet level analysis (i.e., when connection level statistics depend on packet level parameters).

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 efficient usage of the spectrum while improving the QoS experienced by secondary users (SUs), dynamic spectrum leasing (and coordinated cognitive radio) of resources has been previously proposed in the literature. In this paper, the Erlang capacity in coordinated cognitive radio networks with real-time hard delay constraint traffic as function of the rented resources is analytically calculated. For the adequate and fair performance comparison, call admission with fractional channel reservation to prioritize ongoing secondary calls over new ones is considered. From numerical results, it is observed that in CRNs exists a critical utilization factor of the primary resources from which it is not longer possible to guarantee the required QoS of SUs and, therefore, delay sensitive services cannot be even supported in cognitive radio networks. Thus, spectrum leasing can be essential for CRN operators to provide the QoS demanded by delay sensitive services. Then, the cost per capacity Erlang as function of both the utilization factor of the primary resources and the maximum allowed number of simultaneously rented channels is evaluated.

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 of comparison for the ON/OFF and Poisson arrival models, the same both resource utilization factor and mean white space duration in both arrival models are considered. To the best of the authors' knowledge, this performance comparison of CRNs with VoIP traffic under these arrivals models has not been reported in the literature yet. Numerical results show that system performance metrics (new session blocking probability, packet dropping probability, and packet delay) are more pessimistic under the Poisson model than under the ON/OFF model. This is due to the fact that the variance of the white space duration is greater in the Poisson model than in the ON/OFF model.

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 considered. To reduce the negative impact of the interruption of ongoing calls of secondary users (SUs) due to the arrival of primary users (PUs) on the quality of service and to exploit the delay tolerance of elastic traffic, call buffering is employed. Although in cognitive radio networks with elastic traffic and spectrum adaptation there is a tradeoff among blocking/interruption probability and transmission delay, transmission delay has been not previously evaluated as performance metric in these systems. The developed mathematical model additionally considers both impatient time and non-homogeneous bandwidth requirement (i.e., different number of channels utilized) for PUs and SUs. System performance is evaluated in terms of new call and forced call termination probabilities, throughput, and transmission delay. Different probability distributions of the unencumbered service time are considered.

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 degradation due to reconnected secondary sessions. To the best of the authors' knowledge, mechanisms based on limiting the number of reconnections for reducing failure rate have been neither analyzed nor evaluated in the literature. In this paper, limiting the maximum number of reconnections in CRNs with RESTART retransmission strategy for delay tolerant traffic is evaluated as a mechanism to reduce the negative impact of retransmissions and to widen the conditions under which system stability can be achieved. Numerical results show that limiting reconnections is an effective mechanism to alleviate performance degradation due to connection failure. Also a tradeoff between the call completion probability and the supported offered traffic load that can be controlled by varying either the number of reserved channels or the number of allowed retransmission is observed.

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 Erlang capacity in coordinated cognitive radio networks with VoIP traffic is investigated. Employing time-scale decomposition technique and conventional continuous and discrete time Markov chain tools, a joint connection-level and packet-level analytical model is developed. For the adequate and fair performance comparison, a call admission strategy with fractional admission threshold and fractional buffering is considered. An algorithm to determine the optimal values (i.e., the ones that maximize Erlang capacity) of the admission threshold and buffer size is proposed. For given QoS requirements at session and packet level (i.e., VoIP session blocking, packet dropping, and packet delay), the Erlang capacity as function of the maximum allowable number of simultaneously rented resources is evaluated. Additionally, the fraction of time that spectrum leasing is needed is calculated.

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 or the number of active sessions. Arrivals and completions of VoIP sessions, on/off activity detection, and periodic and constant length packet generation of individual VoIP active sessions are modeled. Packet buffering, adaptive modulation coding, and proportional fair sharing scheduling are also considered. Our proposed analysis is based on the quantized queue and cross-level linked decomposition mechanisms that we introduce in this paper to drastically simplify the mathematical and computational procedures with no major impact on the accuracy of the results. The developed analysis allows evaluating the performance of the CAC strategies in terms of the most relevant QoS metrics of VoIP traffic at both call and packet level and, at the same time, mathematical and computational complexity are reduced with no major impact on the accuracy of numerical results.

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 packet level discrete time teletraffic model. The admission criterion (i.e., admission threshold) of new sessions of these strategies is based on either the total number of sessions, the number of active sessions (i.e., sessions in talk-spurt periods), or the number of packets queued in the buffer. Admission threshold and buffer size can be both controlled for QoS provisioning in terms of session blocking and packet dropping probabilities. Arrivals and completions of VoIP sessions, on/off activity detection, and periodic and constant length packet generation (of active sessions) of individual VoIP sessions are modeled. The developed teletraffic analysis allows to evaluate the performance of the CAC strategies in terms of the most relevant QoS metrics of VoIP traffic at both call and packet level (i.e., session blocking and packet dropping probabilities and packet delay). Finally, the maximum traffic attained by the different studied-CAC strategies (while QoS provisioning is guaranteed) is obtained.

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 been compared in the open literature yet. This is the subject under discussion in this work. In order to provide a fair basis of comparison for the ON/OFF and Poisson arrival models, similar average primary channel occupancy characteristics are considered. Specifically, performance comparison is carried out considering both the same resource utilization factor and the same mean white space duration in both arrival models. In addition, different traffic scenarios (i.e., probability distributions of the channel holding time for primary users) are considered to provide deep insights into the performance behavior of CRNs under these arrival models. Our numerical results show the relevance of the adequate characterization of the primary channel occupancy to accurately evaluate the performance of CRNs. In particular, system performance results obtained with the Poisson model are more pessimistic than those obtained with the ON/OFF model. This is due to the fact that the variance of the white space duration is greater in the Poisson model. Finally, it is observed that performance metrics (i.e., call blocking and forced termination probabilities) for the CRN are practically insensitive to the distribution type of the channel holding time in the primary network.

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 it generalizes a large class of useful previous employed distributions in the literature to characterize the channel holding time (i.e., exponential, Erlang, hyper-exponential, and hypo-exponential). Additionally, recently, there have been major advances in fitting Coxian distributions. Our numerical results for 2nd order Coxian model show negligible differences compared with those obtained when the log-normal distribution is considered. (Empirical evidence supports the log-normal assumption for the primary channel holding time.) Thus, the analytical model presented in this paper represents a step towards a general and mathematically tractable framework for the performance evaluation of cognitive radio networks under more realistic assumptions.

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 knowledge, channel holding time statistics has not been obtained under the assumption of heavy-tailed distributed cell dwell time. In this paper, this is addressed by considering Pareto, log-normal or Weibull distributed cell dwell time. Additionally, under the assumption that call holding time is exponentially distributed and cell dwell time is Pareto distributed, novel mathematical expressions for the probability distribution of the channel holding time for new and handed off calls are derived. Numerical results show the extent by which channel holding time statistics are affected by the different parameters of the cell dwell time distribution.

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 level models, “beam overlapping time” has been previously introduced. Beam overlapping time is the period of time in which users sharing the same radio resource degrade the link condition of each other. This time depends on the current co-channel interference conditions which are the result of the real beam pattern and users mobility. Due to the necessity to understand the behavior of this time, some published works have characterized it based on geometrical considerations. However, if only geometrical considerations are contemplated current co-channel interference conditions are ignored. Thus, to fill this void in this paper beam overlapping time is statistically characterized considering real beam patterns as well as realistic users' movement instead of geometrical considerations. Beam overlapping time is statistically characterized via simulation by means of its cumulative distribution function (CDF), mean, variance, and coefficient of variation. Numerical results show that beam overlapping time strongly depends on the antenna array parameters as well as on the users' mobility.

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 analysis is proposed and developed for the calculation of the secondary users' mean total transmission delay. Considering that service time for secondary users is Coxian distributed, numerical results are shown to quantitatively compare the performance of the RR and RS retransmission strategies. It is found that the value of the coefficient of variation (CoV) of service time of SUs plays a major role in the system performance of cognitive radio networks under RR or RS strategies. For scenarios where the CoV of service time for SUs has values around 1, the RS strategy is preferred over the more complex RR strategy. On the contrary, as the CoV of the service time of SUs increases, the system performance improvement becomes significantly greater for the RR strategy relative to the RS strategy.

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 analytical results and insights into the dependence of CHT characteristics on the CDT distribution. For instance, it is found that when CDT is Coxian or hyper-exponentially distributed, CHT is also Coxian or hyper-exponentially distributed, respectively.

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 that access waiting time is a random sum of random variables with the same distribution but random mean. Therefore, the computational complexity for the numerical evaluation of the access waiting time probability distribution increases exponentially with the size of the buffer and the number of coverage regions. In order to reduce the computational complexity, the use of negative exponential distribution is proposed to approximate the whole access waiting time distribution for certain conditions of traffic load. Moreover, an efficient way to calculate its parameter through the Little's theorem is proposed. A more general approach is based on the central limit theorem (CLT). In particular, it considers that the conditional access waiting time of a service request queued in the a given position can be adequately approximated by a Gaussian distribution. The proposed approximation approaches are numerically evaluated and compared against the exact mathematical analysis in terms of the cumulative distribution function. Numerical results show that the maximum percentage error between the both approximated CDFs is smaller than 10% relative to the exact analysis under certain conditions.

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 distribution as well. Furthermore, both new and handoff call channel holding times have generalized Coxian distributions of the same order (number of stages and number of phases within the stages). Additionally, it is demonstrated that the phases on each stage of the hyper-generalized Coxian distributed channel holding times have the same mean permanence time. Therefore, the global channel holding time has also generalized Coxian distribution of the same order (number of stages and number of phases within the stages) of those of the new and handoff call channel holding times. This result permits to simplify teletraffic analysis of cellular networks as a single state variable can be used to keep track of all the types of calls (new and handed off) in a phase (of any stage) with both the same mean permanence time and order within the stages. Mathematical expressions to calculate the parameters of the resulting distributions in terms of the parameters of the distributions of both cell dwell time and unencumbered service time are given. The results obtained in this work are relevant because they allow one to develop analytically and computationally tractable general teletraffic models for performance evaluation of mobile wireless networks under more realistic assumptions.

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 distributed cell dwell and residual cell dwell times have the same mean permanence time. This fact allows us to make our teletraffic model computationally tractable by keeping track in a single state variable all the calls (new and handed off) in a phase (of any stage) with both the same mean permanence time and order within the stages. For this feature, it is also shown that the, so called, global cell dwell time (for new and handoff calls) can be represented by a Coxian model. This Coxian model can be the mixture of Coxian probability distributions. The teletraffic model proposed in this paper represents a step toward the development of a general, analytical, and computationally tractable modelling tool for the performance evaluation of mobile wireless communication networks under more realistic considerations.

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 interruption time are phase-type distributed random variables. Numerical results allow us to quantify the extent by which system performance depends on first three standardized moments of both cell dwell time and unencumbered interruption time.

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 to evaluate the impact of mobility on the performance of this kind of systems. Contrary to the previous related published works, in the present paper the analysis considers realistic users' mobility conditions by means of a smooth random mobility model. Also, intra-cell handoff attempts from outside region to inside region are considered. Novel mathematical expressions for the new call blocking, handoff failure, and call forced termination probabilities are then derived. In addition, Multiple Fractional Channel Reservation is used as a prioritization scheme in order to maximize system capacity. Moreover, the best distribution of resources for each region within a cell is also found for different Radio Resource Management (RRM) strategies and mobility scenarios.

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 conditional cumulative distribution function of the waiting time for users in the different coverage regions. The representation of the conditional waiting time distribution through PHT distributions allows expressing cumulative distribution function (CDF) as a linear combination of negative exponential distributions. The analytical method proposed here captures the exact behavior of the waiting time and the obtained solution is based on matrix analytic derivation, which allows evaluating system performance for any size of buffer and any number of coverage regions.

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, channel characteristics, co-channel interference, and the number of users sharing the same channel within a cell (intra-cell reuse factor) have been largely ignored because the complexity its inclusion entails. To fill this void, a system level model that models both smooth random mobility of users and link unreliability due to (intra-cell and inter-cell) co-channel interference is proposed. Novel mathematical expressions for the new call blocking probability, handoff failure, and probability of interruption due to co-channel interference are derived. The system level model presented here allows simplifying system level mathematical analysis and easily identifying the factors that mainly influence the system performance. Such understanding is vital for planning, dimensioning and optimizing SDMA mobile cellular networks.

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 derived considering different phase-type distributions for both cell dwell time and unencumbered call interruption time due to link unreliability. Then, moments of channel holding time for new and handoff calls are derived using its moment generating function. After that, distribution of channel holding time is approximated by different phase-type distribution functions using the moment matching method. Finally, a novel teletraffic analysis formulation based on this channel holding time approximation is developed. This teletraffic model allows us to reduce computational complexity compared to the exact teletraffic model, which is based on cell dwell time and unencumbered call interruption time statistics. Important system-level performance metrics are derived using this model. Our numerical results are in good agreement with both simulation results and analytical results obtained using the exact teletraffic model.

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 come at the expense of significant connectivity delay and service disruption that users may experience. In this paper, the spatial and temporal intermittent connectivity (STIC) network paradigm is introduced to improve system performance in terms of both connectivity delay and disruption connectivity. The STIC paradigm consists of one or more non-overlapping and coordinated sets of information nodes operating in a temporal intermittent and sequential fashion. This temporally intermittent and sequential operation mode allows STIC systems to spatially distribute the total system capacity. To quantify performance improvement of STIC over SIC wireless communication networks, a simple but an illustrative one-dimensional (drive-through) architecture is considered.

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. Recently, a new system level analytical approach to capture the effect of both link unreliability and radio resource insufficiency in mobile wireless networks was proposed. In that model, the effect of unreliable wireless channel is captured through the appropriate statistical characterization of the unencumbered call interruption time (UCIT). The present paper shows how the probability distribution function of unencumbered call interruption time can be derived from either few system level statistics that can be easily obtained at base stations or link level statistics. Numerical results clearly show that UCIT should be modeled as a general distributed random variable to adequately capture the effect of link unreliability.

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 evaluation of mobile wireless networks taking into account both resource insufficiency and link unreliability is proposed and mathematically analyzed in this paper. In the mathematical analysis, for the sake of generality, the involved time variables (i.e., cell dwell time, unencumbered call interruption time, and channel holding time) are considered to have a general probability distribution. Then, original and easily computable mathematical expressions for many fundamental system level performance metrics are derived. The proposed analytical model allows obtaining more general and realistic results.

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) scheme is also used in the proposed CAC strategy as a system capacity booster. The proposed CAC strategy is mathematically analyzed by means of a teletraffic analysis considering both soft handoff and users' mobility. Realistic mobility conditions are taken into account by characterizing users' mobility parameters considering a smooth random mobility model. Novel mathematical expressions for the new call blocking, handoff failure, and forced termination probabilities are then derived. Mason's rule is employed for the derivation of the forced termination probability.

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 as user prioritization (called DRA LA DAS RAS) is proposed. To the authors' knowledge, most related works have either studied link adaptation (LA) or dynamic resource allocation (DRA) strategies as independent topics but have failed to address their combined effect on GSM/GPRS systems. DRA LA DAS RAS uses both call degradation and call compensation techniques. Calls with the largest number of channels allocated and the worst link quality are degraded first. Conversely, calls with the lowest number of channels allocated and the best link quality are upgraded first. This allows upgraded calls to release resources more rapidly, making them readily available for new calls. Numerical results show that the proposed DRA LA DAS RAS strategy significantly improves system performance, i.e. up to 82% (74%) {58%} [37%]less blocking probability relative to the DRA (DRA LA with p=0.75) {DRA DAS} [DRA LA DAS with p=0.75]strategy.

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 considered strategies is evaluated in GSM/EGPRS networks in terms of call blocking probability for voice packet data users and system throughput. However, the analysis is valid for any Radio Transmission Technology that uses LA techniques. For the mathematical analysis, packet data traffic (i.e., IP) is modeled as a process showing pseudo-long range dependence. In particular, to capture their bursty nature, packet data arrivals are considered to follow a Modulated Markov Poisson Process (MMPP) process. Numerical results show that voice calls get lower blocking probability than data packet transmissions when a fair access resource allocation strategy is used. Also, a trade off between (access and/or transmission rate) fairness and system utilization is observed. Finally, it is also shown that high grade of burstiness significantly degrades the system performance.

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 packing, multiple fractional channel reservation, and anticipated channel release mechanisms to maximize the MCC efficiency achieved by reuse-based resource management strategies in multi-service wireless communication networks. In order to capture the inter-cell dependency, which is required to study the MCC process, a multi-cell model is considered for the teletraffic analysis. The effect of the relative users' mobility and bandwidths requirements on system capacity is evaluated. Numerical results show that the use of dynamic channel allocation and handoff protection policies, in addition to the anticipated channel release mechanism, in the resource management strategy is crucial for minimizing the impact of mobility on the MCC process. This is especially true when the network supports multiple classes of subscribers having different bandwidth and quality of service requirements.

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 and the transmission queue of each station is assumed to be always nonempty. This assumption is a good approximation for a local area network working at full capacity; however, in a cellular system the assumptions of finite population and that every node in a cell has always a packet to transmit is not very realistic. Here, analytical results considering a S-ALOHA random access protocol with a Poisson arrival process - more suitable for the traffic model in a cellular system - for the users in the cells is presented. Using the geometrical backoff (GB) strategy, two approaches to find the optimum retransmission probabilities are developed; in the first one, the number of backlogged packets is required while a simpler and efficient alternative method requires only the knowledge of the new packet arrival rate.

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 literature can adequately be modeled by considering a Poisson call interruption process. This is turn results in significant simplifications of system level analysis. Then, with the proposed interruption modeling, an elegant teletraffic analysis for the performance evaluation of mobile cellular CDMA networks considering both wireless link unreliability and resource insufficiency is developed. Realistic mobility conditions are taken into account by characterizing users' mobility parameters by means of a smooth random mobility model. Novel mathematical expressions for the new call blocking, handoff failure, and forced termination probabilities are then derived. Graph theory and Mason's rule are employed for the derivation of the forced termination probability.

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 adaptation (LA) and multi-slot allocation experienced by data users in EGPRS networks is smoothed by these strategies through the use of multiple resource reservation and/or dynamic resource allocation strategies, which, at the same time, compensate users with poor radio channel conditions. Also, the performance of the proposed strategies is evaluated by means of teletraffic analysis tools in terms of packet blocking probabilities and throughput

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 (i.e., codes of the lowest layer of the OVSF code tree) are reserved to differentiate users with different bandwidth requirements. Leaf codes are only reserved for as long as the call admission process lasts. Once the decision of whether a new request is admitted or not has been made, a Code Dereservation procedure is carried out to increase flexibility in the code assignment phase. The performance of these MLCR strategies with/without code reassignments is then evaluated. Analysis shows that MLCR schemes are also useful in improving fair access among different traffic classes. In addition, perfect fair access among requests with different data rates can be achieved when code reassignments are jointly employed with the proposed OVSF-code reservation schemes.

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 exists in the literature. Also, the link quality-aware dual fractional channel reservation (LQA DFCR) scheme is proposed. In LQA DFCR, user differentiation is implemented in terms of link quality. Preference is given to users with good link quality because they require fewer resources than users with bad link quality. Numerical results show that the proposed LQA DFCR scheme effectively increases system capacity: LQA DFCR achieves more than a 11% capacity gain relative to systems with the non priority scheme (NPS) and with LA, and approximately 3% relative to the fair access prioritisation scheme (FAPS) strategy. Numerical results also show that LA yields an approximately 18% capacity increase relative to a cellular system without LA when no admission control is employed (admission control strategies further increase system capacity.) The synergy between LA and admission control strategies yields more than a 31% capacity gain

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 Channel (UFGC) strategies is then evaluated. Results show that maximum system capacity decreases exponentially as the mean cell dwell time decreases and that the relative capacity gain of each scheme depends on the mean cell dwell time. It was also found that LFGC outperforms GC and UFGC under any mobility condition.

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) separately. Additionally, a DRA strategy with link quality-aware prioritized channel de-allocation (called DRA LA DAS) is proposed. With the DRA LA DAS scheme that calls with the greatest number of channels and the worst link quality are degraded first. In this way, in DRA LA DAS preference is given to data users with good quality link which, on average, retain resources less time than data users with bad quality link. Numerical results show that the proposed DRA LA DAS strategy significantly improves system performance. The GSM/GPRS system is used as a case study. The GSM voice new call blocking and forced termination probabilities, GPRS packet dropping probability, average GPRS packet transmission time, and channel utilization are analyzed

In this paper, recursive formulas to calculate the new call blocking and handoff failure probabilities for fractional guard channel (FGC) policies in cellular networks are derived. Since the limited fractional guard channel (LFGC), the uniform fractional guard channel (UFGC), the guard channel (GC), and the non-prioritization schemes (NPS) are particular cases of the FGC policies; the recursive formulas for the blocking probabilities of these schemes are implicitly obtained as well. The optimal performance of the GC, LFGC, and UFGC strategies is compared in terms of the maximum system capacity for different mobility conditions. It is observed that as mobility increases the system capacity decreases. Results show that the relative capacity gain of the different schemes depends on the value of the mean cell dwell time relative to the mean service time. It is shown that LFGC overcome the GC, UFGC, and NPS strategies for any mobility condition and can achieve as much as 3% capacity gain relative to GC, 10% relative to UFGC, and 12% relative to NPS.

A mobility-aware call admission strategy for wireless communication systems, called regulated call dropping (RCD) with fractional channel reservation (FCR) (RCD-FCR), is proposed. RCD-FCR combines a RCD scheme with the FCR strategy to increase fairness among all classes of mobile users and channel utilization efficiency. Users are classified according to their mobility characteristics int slow and fast moving users (i.e., pedestrians and vehicles). Calls by slow moving users are intentionally dropped in a controlled manner (through the use of a call dropping authorization probability). The FCR strategy', on the other hand, is used to improve the protection of ongoing calls against new calls. Numerical results show that RCD-FCR achieves 23.3% capacity gain relative to the nonpriority scheme and 5.56% relative the FCR strategy.

In mobile cellular systems with link adaptation (LA), different quality/.ones, in terms of the Signal-to-interference Ratio (SIR), are distinguished. In this paper, the quality zone residence time distribution in mobile cellular systems with link adaptation is addressed. The cell residence time distribution has been widely studied in the literature. However, a literature survey shows that relatively few in-depth papers have addressed the quality zone residence time. In this work, comprehensive simulation results for a generalised mobility model are shown. Results show that as the mobility randomness increases, the probability density function of the quality zone residence time tends to a negative exponential one.

In this paper, a new adaptive resource allocation strategy called equal resource sharing allocation with differentiated QoS (ERSAQoS) is presented. This strategy is suitable for operation in environments with integrated service types (i.e.: voice, video, videophone) with different bandwidth requirements and priorities each. Our strategy allows soft-controlled differentiated QoS provisioning. Results show that ERSAQoS meets the upper capacity bound for flexible resource allocation strategies while improving the QoS of the prioritised service types.

In this paper, the multiple fractional channel reservation (MFCR) strategy for service differentiation is proposed. Contrary to the rest of the channel reservation schemes proposed in the literature, these strategy reserves, on average, real numbers of channels to prioritise different call types (new or handoff) in multiple service environments. Determining the right number of reserved channels for each call type to satisfy all QoS constraints is a difficult task. Also, selecting the right prioritisation order is not an easy process, as it depends on QoS constraints and system characteristics. Thus, an algorithm to determine the optimum numbers of reserved channels to achieve maximum system capacity when using the MFCR is also proposed. To our knowledge, the capacity optimisation problem considering individual QoS constraints for each call type had only been addressed in single service environments.

In this paper, the performance of wireless mobile communication systems with link adaptation is evaluated by means of a teletraffic analysis. To our knowledge, no similar analysis considering link adaptation exists in the literature. In particular, mathematical expressions for the handoff call arrival rate, the intra-cell handoff failure and the forced termination probabilities are derived. Half- and full-rate vocoders are considered and a link quality-aware dual channel reservation (LQA DCR) scheme is proposed. In LQA DCR, preference is given to users with good link quality because they require fewer resources than users with bad link quality. Numerical results show that the proposed LQA DCR scheme effectively increases system capacity.

A mobility-aware handoff prioritisation strategy for wireless communication systems with heterogeneous platform types, called regulated call dropping (RCD) with channel reservation (CR) (RCD-CR), is proposed. RCD-CR combines a RCD scheme with the CR strategy to increase fairness among all classes of mobile users and channel utilisation efficiency. Call dropping (pre-emptive) strategies have almost exclusively been used to prioritise real time traffic over non-real time data traffic (delay tolerant traffic classes) in the literature. In this paper, call dropping is used to prioritise calls carrying real time traffic over other calls carrying the same class of traffic. RCD-CR takes into account the different speeds of slow and fast mobile users to equalise the QoS provided to all of them. With the aim of releasing resources to attend handoff calls by fast moving users, calls by slow moving users are intentionally dropped in a controlled manner (through the use of a call dropping authorisation probability). The CR strategy, on the other hand, is used to improve the protection of ongoing calls against new calls.

In this paper, the transmission delay in adaptive resource allocation strategies with uniform quality of service (QoS) provisioning is addressed. The accuracy of a mathematical analysis approach is corroborated by semi-analytical results. The analytical approach is based on the fact that in flexible resource allocation (FRA) strategies with uniform QoS provisioning all active sessions of each service type equally share their resources and tend to utilise an average bandwidth. The fact that the probability density function of the normalized transmission delay is almost a symmetrical function is also considered.

Future wireless communication systems will consist of at least one network with anywhere/anytime coverage supplemented by limited coverage networks offering high speed communication services with low cost per transmitted bit, and using low power consumption portable terminals. In this paper a new system architecture for limited coverage wireless communication networks, called Intermitstations, is proposed. An Intermitstations system consists of two or more nonoverlapping Infostations systems operating intermittently. That is, Infostations systems do not work simultaneously, instead they operate sequentially. Each Infostations system works periodically during a fixed time period. Due to their configuration flexibility, Intermitstations systems are intended to provide wireless communication services in a variety of different environments, including highways and hot spots located mainly in urban areas. Also, in this paper, the coverage delay in both Infostations and Intermitstations systems is mathematically analyzed. It is shown that Intermitsations can greatly decrease coverage delay relative to the Infostations architecture.

In this paper, a novel approach to mathematically analyse the performance of adaptive resource allocation strategies with uniform quality of service (QoS) provisioning, when session service time depends on the allocated bandwidth, is proposed. Our proposed approach is based on the fact that in adaptive resource allocation strategies with uniform QoS provisioning all active sessions of each service type tend to utilise a bandwidth close to the average. The transmission delay experienced by sessions, compared to an optimal transmission operating at the maximum bandwidth requested is a characteristic related performance measurement that is also addressed in this work.

This article presents a mathematical analysis of the access delay in the adaptive traffic load (ATL) protocol. The basic idea of the ATL protocol is to limit the number of packet transmission for both new and backlogged users, in order to avoid collisions and keep the system stability. For this purpose, all users have an authorization probability to transmit which depends on the system traffic load. By using ATL protocol for high traffic loads, we maintain the throughput constant at its maximum value regardless of the traffic load of the system. Additionally in ATL, access delay is a linear function of the traffic load, meanwhile in conventional access protocols it is an exponential function. Additionally, we consider the EDGE (enhanced data for GSM evolution) frame structure and slot duration. EDGE is proposed as the evolution of TDMA based second generation networks to offer packet data transmission in order to provide the 3G services.

The performance of a flexible resource allocation strategy (FRA) combined with a dynamic channel allocation strategy (DCA) is assessed. Special attention is given to the upper capacity limits. Hence, the maximum packing (MP) is selected as the DCA strategy whereas the resource sharing for data services (RSDS) is selected as the FRA strategy. MP and RSDS represent, respectively, the upper limit in terms of capacity in DCA and FRA strategies. The assessment is performed in a Manhattan-like environment. Results show that the combination of DCA and FRA can produce an increase in terms of capacity of about 18% with respect to the use of FRA only.

We study the impact of the anticipated channel release (ACR) strategy in the performance of multi-rate transmission mobile microcellular networks. The ACR strategy takes advantage of break-before-make hard handoff characteristics to improve system capacity. We obtain analytical expressions for new call blocking and handoff failure probabilities in the full access system using the multidimensional birth-and-death process. From these expressions, we observe that the anticipated channel release strategy increases the system capacity to m channels, where m is the number of basic channels required by a high-rate traffic call. Moreover, we note that the use of ACR improves the forced termination probability for high-rate traffic calls. Also, we evaluate the performance of the maximum packing algorithm for multi-rate transmission traffic calls under two different simulation topologies. These are the wrapped around topology, which minimizes the boundary effect, and the unwrapped topology, which ignores it. Simulation results obtained using the unwrapped topology compared to those obtained using the wrapped one differ no more than 1.5%.

In this paper we describe two priority-based algorithms for data communication considering the length of the packet which improves the performance of packet data transmission on EDGE. We also propose packet voice transmission over EDGE by allowing real-time users to use packet data channels in the same network maintaining both the normalized delay and the low blocking probability.

A new flexible resource allocation (FRA) scheme called flexible resource allocation strategy with prioritised levels (FRASPL) is proposed. FRASPL meets the upper capacity bound for FRA strategies while providing acceptable quality to the admitted request by using degradation and compensation of all active calls. FRASPL can trade-off capacity and QoS. FRASPL is deliberately designed to cope with several service types defining also prioritisation rules that makes it different to the rest of the strategies previously proposed in the literature.

A comprehensive study of flexible resource allocation (FRA) strategies is presented and a new strategy called Flexible Resource Allocation Strategy with Differentiated Priorities and QoS (FRAQoS) is proposed. FRAQoS copes with scenarios where multiple types of service coexist with different priorities and QoS requirement each, offering service integration and differentiation required by 2.5G and 3G systems. Also, a fair comparison of FRAQoS with almost all the previously proposed strategies is performed through the use of an analytical model (validated by computer simulations).

We present a new flexible resource allocation (FRA) strategy, called resource sharing for data services (RSDS), that dynamically averages the allocated resources to the call requests based on the number of calls in a cell. RSDS accommodates the maximum number of requests while providing acceptable quality to the admitted request through the use of. degradation and compensation techniques. An analytical model (validated by computer simulations) is developed to model RSDS in a scenario with multiple types of service, each of them with different priorities. Preliminary results indicate that the RSDS strategy outperforms some strategies already reported in the literature.

The boundary effect in multimedia TDMA personal mobile communication network simulation is investigated. We evaluate the performance of several channel assignment strategies (CASs) for multi-rate traffic calls in a Manhattan-like microcellular environment under two different simulation topologies. These are the wrapped around topology, which minimize the boundary effect, and the unwrapped topology, which ignore it. Both, uniform traffic and uneven time varying traffic are considered. Also, the user mobility is taken into account. The CASs evaluated are the maximum packing (MP) algorithm with cluster channel reservation (CCR) and the extended local packing (ELP) algorithm. The ELP is a practical distributed dynamic CAS that approaches closely the system capacity of the MP with CCR algorithm. Simulation results obtained using the unwrapped topology compared to those obtained using the wrapped one differs no more than 2%.

We propose a new medium access control mechanism for EDGE. This strategy employs the slotted ALOHA random multiple access based on the traffic load of the system. Slotted ALOHA reaches the maximum throughput of 36% at a normalized traffic load of 1 packet per slot transmission time. Adaptive traffic load S-ALOHA keeps the maximum throughput for normalized offered load higher than one, by assigning a probability to transmit to each user in the system. In this way, we maintain the throughput constant at the maximum value for all normalized traffic loads bigger than 1 packet per time slot and we keep the blocking probability lower than the original slotted ALOHA protocol. In particular, we consider the EDGE frame structure and slot duration but this is a general medium access control mechanism that can be employed by all S-ALOHA protocols with a minimum modification.

We propose a channel assignment strategy to prioritize handoff calls in multi-rate mobile microcellular networks. This strategy is based on the non-handoff failure system and employs the novel concept of intra-cluster channel reassignment. Simulation results reveal that large bandwidth traffic classes are blocked or forced to terminate more often than small bandwidth traffic classes. In our proposed strategy the channels may be kept in use in the target cell with high probability when a handoff occurs. In this way, the handoff failure probability is significantly reduced. Also, the channel change probability at cell crossing is reduced. Because of the channel sharing between cells, our strategy adapts better than the fixed channel assignment (FCA) to the time variant non-uniform traffic characteristic of the microcellular networks.

The effects of cell radius reduction and path loss model parameters on the performance of microcellular networks are studied. The performance is measured in terms of the average co-channel interference probability and reuse efficiency. The influence of reuse distance, cell size, traffic intensity, break point distance of the dual path loss law characteristics of microcells, and standard deviation of log-normal shadowed local mean on the performance parameters are investigated. Also, capacity increase due to cell radius reduction combined with dynamic channel assignment strategies (DCA) is evaluated. Our main contribution is the observation that the system performance is extremely sensitive to the propagation model parameters and depends strongly on the cell size and reuse factor. As it is expected, analytical and simulation results show that reducing the cell radius increases the cell's Erlang capacity per unit area. However, this cell radius reduction implies an increase in the co-channel interference level and then a higher reuse factor may be required to keep the quality of service. On the other hand, it is shown that the system capacity increase due to the cell radius reduction is much greater in microcellular systems with DCA than in those with fixed channel assignment.

In this paper, the effect of the hard and soft handoff on the reverse link capacity for a CDMA Manhattan like microcellular system is evaluated. We obtain analytical expressions for the relative other-cell interference factor as a function of the breakpoint, the cell radio, the variance of the random variation and the propagation path loss exponents for both hard and soft handoff. It is shown that the capacity is an increasing function of the breakpoint distance to the cell radio ratio and that the capacity increase because of the soft handoff process is a function of the breakpoint to the cell radio ratio. The highest capacity is obtained for breakpoint distances smaller than 0.7 the cell radio. On the other hand, the lowest capacity increase because of the use of soft handoff (over hard handoff) is obtained for breakpoint distances smaller than 0.7 the cell radio.

In this paper the frequency reuse problem in microcellular systems is studied. It is shown that due to the particular propagation conditions in microcellular environments, the frequency reuse pattern can tolerate one or more violations. Taking into account the possibility of admitting one violation to the reuse pattern, a new concept of available carrier with violation (ACV) is developed. This concept of ACV allows to use carriers with at most one violation to the reuse pattern (VRP), under the restriction that both cells using simultaneously the same carrier must be the bound cells of their interference neighborhoods. The effect on the outage probability of using carriers with one VRP can be tolerated, because the decrease of SIR is moderate, and with an specially designed carrier acquisition and release policies, the probability that a carrier be used with VRP is less than 5% for all the range of offered traffic simulated. The concept of ACV is introduced in two distributed dynamic channel assignment (DDCA) schemes, and simulation results show that these new DDCA with VRP schemes overcome the performance of the maximum packing (MP) algorithm, without the need of centralized coordination and global rearrangements.