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In future fifth-generation (5G) communication systems, driven by the evolution of today's most demanding applications, video streaming over vehicle networks will play an increasingly significant role in our daily lives. In this paper, based on a heterogeneous architecture consisting of both cellular base stations (BSs) of wide coverage and cognitive-radio-enabled roadside infrastructures, a semi-Markov decision process (SMDP)-based resource-allocation scheme is proposed to facilitate video streaming application in terms of peak signal-to-noise ratio (PSNR) and smooth playback. In addition to improving video quality of vehicle users, quality of service (QoS) provisioning for background users that can originally exist in the cellular network is also considered in the proposed scheme. Specifically, based on the states of the background users, vehicle users, and the availability of the cognitive bands, the optimal resource allocation, aiming at maximizing the video streaming quality while guaranteeing the call-level performance of the background users, is achieved by addressing two interrelated joint call admission control (CAC) and channel allocation problems for cellular and roadside infrastructure networks, respectively. Simulation results show that the proposed scheme can well protect background users when coexisting with bandwidth-hungry vehicle video users and is effective in not only improving video streaming quality for vehicle users but boosting bandwidth utilization of the whole network as well.

In this paper, we propose a mobility-aware call admission control (MA-CAC) algorithm with a handoff queue (HQ) in mobile hotspots, where different admission control policies are employed, depending on the vehicle mobility. Specifically, when a vehicle is static, a handoff priority scheme with guard channels is studied to protect vehicular handoff users because handoff users may get on the vehicle. In addition, an HQ is examined during stopping to further accept handoff users. On the other hand, for a moving vehicle, no guard channels for handoff users are allocated to maximize channel utilization. By means of Markov chains, we evaluate MA-CAC with an HQ in terms of new-call blocking probability (NCBP), handoff-call dropping probability (HCDP), handoff-call waiting time in the HQ, and channel utilization. Analytical and simulation results demonstrate that MA-CAC with an HQ can lower both the HCDP and the NCBP while maintaining high channel utilization.

Dynamic spectrum access (DSA) techniques based on the exclusive-use model provide a huge opportunity for wireless service providers (WSPs) to improve the spectrum utilization in their licensed bands and generate additional profits by allowing temporary wireless access to unsubscribed secondary users (SUs). This paper presents a techno-economic analysis for regulated SU access based on a novel base station (BS)-centric framework, where SUs coexist with the subscribers, i.e., primary users (PUs), on a mutually exclusive basis. Considering the highly competitive WSP environment, the proposed framework is aimed at maximizing the localized spectrum utilization within the static spectrum licensed to the WSP and assumes no cooperation and no spectrum sharing among WSPs, thus making this a business case for implementation. The dynamic incentive-based SU pricing model proposed in this paper has the inherent capability of call admission control and, hence, is useful in attracting SUs to obtain temporary wireless access during periods of low PU demand, thus improving spectrum usage in the temporal domain. Although SU access is regulated by the WSP at their BS, the SUs have the freedom to connect or handoff to their preferred BS in the area based on the SU price quoted by the WSP. The implementation of the proposed framework to Long Term Evolution (LTE) infrastructure requires minimal enhancements and can be potentially attractive to WSPs, since the SU devices in this framework do not require spectrum sensing cognitive capabilities. Considering all the aforementioned aspects, this paper can be considered an intermediate step in the evolution toward complete DSA.

Broadband wireless communication systems, namely, Worldwide Interoperability for Microwave Access (WiMAX) and Long-Term Evolution (LTE), promise to revolutionize the mobile users wireless experience by offering many of the services and features promised by fourth-generation (4G) wireless systems, such as supporting multimedia services with high data rates and wide coverage area, as well as all-Internet Protocol (IP) with security and quality-of-service (QoS) support. These systems, however, require proficient radio resource management (RRM) schemes to provide the aforementioned features they promise. In this paper, we propose a new framework, which is called dynamic QoS-based bandwidth allocation (DQBA), to support heterogeneous traffic with different QoS requirements in WiMAX networks. The DQBA framework operates as such; it dynamically changes the bandwidth allocation (BA) for ongoing and new arrival connections based on traffic characteristics and service demand. The DQBA aims at maximizing the system capacity by efficiently utilizing its resources and by being fair, practical, and in compliance with the IEEE 802.16 standard specifications. To achieve its objectives, DQBA employs a flexible architecture that combines the following related components: 1) a two-level packet scheduler scheme; 2) an efficient call admission control policy; and 3) a dynamic BA mechanism. Simulation results and comparisons with existing schemes show the effectiveness and strengths of the DQBA framework in delivering promising QoS and being fair to all classes of services in a WiMAX network.

A hierarchical overlay structure is an alternative solution that integrates existing and future heterogeneous wireless networks to provide subscribers with better mobile broadband services. Traffic loss performance in such integrated heterogeneous networks is necessary for an operator's network dimensioning and planning. This paper investigates the computationally efficient loss performance modeling for multiservice in hierarchical heterogeneous wireless networks. A speed-sensitive call admission control (CAC) scheme is considered in our model to assign overflowed calls to appropriate tiers. This approach avoids unnecessary and frequent handoff between cells and reduces signaling overheads. An approximation model with guaranteed accuracy and low computational complexity is presented for the loss performance of multiservice traffic. The accuracy of numerical results is validated by comparing the results from the approximation with simulations.

The wireless mesh network (WMN) has recently emerged as a promising technology for next-generation wireless networking. In the WMN, it is crucial to support mobile users roaming around the network without service interruption. This consideration motivates us to develop an efficient fast handoff approach using distributed computing technology. Particularly, we propose a mobile agent (MA)-based handoff architecture for the WMN, where each mesh client has an MA residing on its registered mesh router to handle the handoff signaling process. To guarantee quality of service (QoS) and achieve differentiated priorities during the handoff, we develop a proportional threshold structured optimal effective bandwidth (PTOEB) policy for call admission control (CAC) on the mesh router, as well as a genetic algorithm (GA)-based approximation approach for the heuristic solution. The simulation study shows that the proposed CAC scheme can obtain a satisfying tradeoff between differentiated priorities and the statistical effective bandwidth in a WMN handoff environment.

When spectrum is shared among multiple radio systems, spectrum admission control (SAC) can be performed via a centralized spectrum manager to meet their respective traffic demands. The adopted policy will determine the admission of service requests and, in turn, affect the overall spectrum utilization efficiency. The design of SAC policies becomes more challenging when each radio system provides a grade of service (GoS) in the form of a blocked service guarantee to its users. Given such constraints, we study the admission region, which indicates the maximum amount of supported traffic for the given resources. We first study the performance based on a simple first-come-first-serve (FCFS) policy. Our studies show that the admission region is, in general, limited by the radio system that first violates its prescribed GoS guarantee (i.e., the performance-limiting radio). We propose three SAC policies to enhance the total offered traffic and compare them against the FCFS policy. The first is a random discard (RD) policy, where requests from other systems are discarded with some predetermined probabilities so that a larger portion of the spectrum is made available to the performance-limiting radio. The second SAC uses a reservation (RES) policy, where a suitable amount of spectrum is reserved for the performance-limiting radio. In the third policy, SAC is formulated as a discrete-time constrained Markov decision process (MDP). We analyzed the performance of each policy at low and high request rates and show how the additional design parameters in each policy can be optimized to enhance the offered traffic. As admission decisions are jointly made with traffic predictions, the MDP admission policy shows superior performance over the other policies due to its flexibility to operate both radios at the bound of the respective GoS constraint.

Next-generation communication systems are expected to be highly integrated heterogeneous networking environments. Supporting multimedia services with different quality-of-service (QoS) requirements over such highly heterogeneous environments is a very challenging task, and a unified call admission control (CAC) optimization mechanism is needed to allow resources to be efficiently utilized. In this paper, we propose an optimal CAC mechanism, i.e., the guard-channel-based incremental and dynamic optimization (GUIDO), which is a threshold-based CAC scheme that is designed based on the Markov decision process (MDP) and sensitivity analysis (SA) techniques. The MDP is used to derive the optimal CAC policy for predetermined goals, whereas the use of SA can greatly reduce the effort of unnecessary recomputation of the CAC policy when the traffic condition varies. Through the use of system capacity estimation and QoS mapping techniques, GUIDO allows the CAC operation to be performed in a general framework, even with various underlying communication systems and different access/core networks. GUIDO can be implemented dynamically (online optimization) and statically (lookup table). Homogeneous and heterogeneous systems with multiple service priority classes are studied in this paper. We have considered comprehensive objective functions, and each characterizes a different interest of the service provider. The performance is evaluated via an event-driven simulator, and the results are compared with those of the complete sharing scheme and conventional guard channel schemes under constant call-arrival rates as well as time-varying call-arrival-rate traffic scenarios.

Worldwide interoperability for microwave access (WiMAX) is a promising technology for last-mile Internet access, particularly in the areas where wired infrastructures are not available. In a WiMAX network, call admission control (CAC) is deployed to effectively control different traffic loads and prevent the network from being overloaded. In this paper, we propose a framework of a 2-D CAC to accommodate various features of WiMAX networks. Specifically, we decompose the 2-D uplink and downlink WiMAX CAC problem into two independent 1-D CAC problems and formulate the 1-D CAC optimization, in which the demands of service providers and subscribers are jointly taken into account. To solve the optimization problem, we develop a utility- and fairness-constrained optimal revenue policy, as well as its corresponding approximation algorithm. Simulation results are presented to demonstrate the effectiveness of the proposed WiMAX CAC approach.

This paper presents a new linear programming approach for throughput maximization on the uplink of a multiclass variable spreading gain code-division multiple-access (CDMA) multicellular system in Rayleigh fading for both binary phase-shift keying (BPSK) and quaternary phase-shift keying (QPSK) modulations. Based on the improved Gaussian approximation technique, we derive exact closed-form expressions of the outage probability, which are used as a physical (PHY) layer constraint of the maximization problem. We show that it is possible to transform the nonlinear constraint into a set of equivalent linear expressions. This facilitates the formulation of a new linear throughput maximization that noticeably requires less computational complexity than the known nonlinear approaches. Furthermore, due to the simplicity of the linear approach, we can include the constraints of such higher layers, i.e., media access control (MAC) and call admission control (CAC) layers, into the proposed formula. Accordingly, we introduce two linear programming optimization formulas. One is for MAC-PHY optimization, and another is for cross-layer optimal CAC policy. In the case of MAC-PHY optimization, the throughput is maximized, at low background noise level, when every user retains the same bit energy, particularly in the case where the difference in data rates is high. Nonetheless, at high levels of background noise, the throughput would be maximized when a larger amount of bit energy is allocated to the high-rate users. For the joint optimal policy, the throughput and the blocking probability are optimized and improved up to 50% in comparison to those of the conventional CAC policy, which is known as the complete sharing policy. © 2008 IEEE.

Future wireless networks are designed to support adaptive multimedia by controlling individual ongoing flows to increase or decrease their bandwidths in response to changes in traffic load. There is growing interest in quality-of-service (QoS) provisioning under this adaptive multimedia framework, in which a bandwidth adaptation algorithm needs to be used in conjunction with the call admission control algorithm. This paper presents a novel method for QoS provisioning via average reward reinforcement learning in conjunction with stochastic approximation, which can maximize the network revenue subject to several predetermined QoS constraints. Unlike other model-based algorithms (e.g., linear programming), our scheme does not require explicit state transition probabilities, and therefore, the assumptions behind the underlying system model are more realistic than those in previous schemes. In addition, when we consider the status of neighboring cells, the proposed scheme can dynamically adapt to changes in traffic condition. Moreover, the algorithm can control the bandwidth adaptation frequency effectively by accounting for the cost of bandwidth switching in the model. The effectiveness of the proposed approach is demonstrated using simulation results in adaptive multimedia wireless networks.

Call admission control (CAC) strongly influences the performance of 3G/4G spread spectrum systems because it determines the number of active users that are admitted to the network, i.e., influences spectral efficiency. A novel air interface CAC algorithm is introduced in this paper. It optimizes the utilization of radio resources and provides real-time adaptation to the radio channel with generalized multiplicative fading. Users are handled as memory-less traffic sources. The suggested CAC method was evaluated for lognormal fading and on/off traffic.

Most call admission control (CAC) schemes proposed for dynamic channel allocation (DCA)-based systems simply follow the same philosophy as adopted by fixed channel allocation (FCA)-based systems, i.e., only considering intercell handoffs. Doing so is acceptable for FCA and coordinated DCA systems because an intracell handoff caused by a new channel assignment rarely happens in these cases. However, as discussed in this paper, in a distributed DCA with a measurement-based channel assignment, the intracell handoff may happen frequently and can dominate handoff events because failed intracell handoffs reduce the number of intercell handoffs. In this case, the CAC considering only the intercell handoff cannot work properly for such DCA systems. In this paper, we discuss a novel CAC to consider both intercell and intracell handoffs to guarantee a handoff call dropping probability (CDP) by jointly using the channel carrying approach. We also investigate a measurement-based implementation of this proposal through computer simulations. The results show that the proposed CAC can effectively bound the CDP to a target CDP

Interference is the key parameter in a code-division multiple access (CDMA) network. As users move around, the interference will flow with the movement. The objective of this paper is to study the impact of the moving interference (mobility) on systems' performance and design parameters. In this paper, we develop a detailed CDMA interference model with soft handoff, power-control errors, and shadowing effect. We combine this interference model with a Markov model to study the performance of CDMA systems under various mobility and traffic conditions. We also present a call admission control (CAC) scheme that sets aside some interference cushion for handling mobility and compare this scheme with other CAC schemes in terms of the effectiveness of mitigating the negative impact of mobility on system capacity

Many guard-channel-based call admission control (CAC) schemes for cellular networks have been proposed to provide the desired quality of service to not only new calls but also ongoing calls when they hand off to neighboring cells. Blocking/dropping probabilities of new/handoff calls are generally analyzed using one-dimensional Markov chain modeling under specific assumptions to avoid solving large sets of flow equations that makes exact analyses of these schemes using multidimensional Markov chain models infeasible. This is the case with the "traditional" approach, which assumes that channel holding times for new and handoff calls have equal mean values, and the "normalized" approach, which relaxes this assumption but is accurate only for the new call bounding CAC scheme. In this paper, we reevaluate the analytical methods for computing new/handoff call blocking/dropping probabilities for several widely known CAC schemes and develop an easy-to-implement method under more general assumptions. Numerical results show that when the mean channel holding times for new and handoff calls are different, the proposed "effective holding time" approach gives more accurate results compared with the traditional and the normalized methods while keeping the computational complexity low. The accuracy of these methods and their levels of computational complexity with the exact solution are also compared

An analytical model to study the performance of wireless local area networks (WLANs) supporting asymmetric nonpersistent traffic using the IEEE 802.11 distributed coordination function mode for medium access control (MAC) is developed. Given the parameters of the MAC protocol and voice codecs, the voice capacity of an infrastructure-based WLAN, in terms of the maximum number of voice connections that can be supported with satisfactory user-perceived quality, is obtained. In addition, voice capacity analysis reveals how the overheads from different layers, codec rate, and voice packetization interval affect voice traffic performance in WLANs, which provides an important guideline for network planning and management. The analytical results can be used for effective call admission control to guarantee the quality of voice connections. Extensive simulations have been performed to validate the analytical results

Resource allocation and call admission control (CAC) are key management functions in future cellular networks, in order to provide multimedia applications to mobiles users with quality of service (QoS) guarantees and efficient resource utilization. In this paper, we propose and analyze a priority based resource sharing scheme for voice/data integrated cellular networks. The unique features of the proposed scheme are that 1) the maximum resource utilization can be achieved, since all the leftover capacity after serving the high priority voice traffic can be utilized by the data traffic; 2) a Markovian model for the proposed scheme is established, which takes account of the complex interaction of voice and data traffic sharing the total resources; 3) optimal CAC parameters for both voice and data calls are determined, from the perspective of minimizing resource requirement and maximizing new call admission rate, respectively; 4) load adaption and bandwidth allocation adjustment policies are proposed for adaptive CAC to cope with traffic load variations in a wireless mobile environment. Numerical results demonstrate that the proposed CAC scheme is able to simultaneously provide satisfactory QoS to both voice and data users and maintain a relatively high resource utilization in a dynamic traffic load environment. The recent measurement-based modeling shows that the Internet data file size follows a lognormal distribution, instead of the exponential distribution used in our analysis. We use computer simulations to demonstrate that the impact of the lognormal distribution can be compensated for by conservatively applying the Markovian analysis results.

This paper investigates the features of a cellular geometry in code-division multiple-access (CDMA) systems with soft handoff and distinguishes controlling area of a cell from coverage area of a cell. Some important characteristics of the cellular configuration in soft handoff systems are used to propose a new design of efficient call admission control (CAC) in CDMA systems. Then, the paper constructs a continuous-time Markov chain (CTMC) model for CAC in CDMA with a soft handoff queue, obtains closed-form solutions, and thus develops loss formulas as performance indices such as the new blocking probability and the handoff dropping probability. In order to determine handoff traffic arrival rate, a fixed-point strategy is developed. Algorithms are also provided to stably compute loss probabilities and to determine the optimal number of guard channels. A new soft handoff scheme-eliminating pseudo handoff calls (EPHC)-is proposed to improve channel utilization efficiency based on mobility information. As an application of the loss formulas, the proposed modeling techniques are used to evaluate and compare the performance of conventional and proposed EPHC soft handoff schemes. Numerical results show the effectiveness of the proposed Markov chain models and the benefits of the new soft handoff scheme.

This paper introduces a new call admission control scheme. Quality of service (QoS) parameters are negotiated during the admission procedure at heavy loaded cells and maximum capacity is achieved. Blocking and dropping are used to prevent the system from an outage situation but their probability of occurrence is greatly reduced. Reservation bandwidth is used thoroughly as a means of improving overall QoS. Furthermore, the greatest common divisor of all the application load factors is considered as the resource unit, the resulting resource pool is identified and the performance of the above algorithms is analyzed using a novel multistep Markov analysis. The analysis takes account of classes without time restrictions, which are served with a pre-emptive system. Although the increased channel utilization of our proposed scheme reduces the available bandwidth for calls with pre-emption, we compensate for this loss using an extra reservation bandwidth. Blocking probability, dropping probability, average time delay in the queue, and channel utilization factor are used as benchmarks for the proposed schemes.

We consider hierarchical cellular code-division multiple-access networks supporting soft handoff, where users with different mobility are assigned to different layers, i.e., microcells in the lower layer are used to carry slow users, whereas macrocells in the upper layer are for fast users, and handoff queues are provided for handoff calls that cannot obtain the required channel immediately, so that forced termination probability can be reduced. According to whether handoff queues are provided in microcells and/or macrocells, four different call admission control schemes are proposed and studied. We derive the mathematical model of the considered system with multidimensional birth-death process and utilize Gauss-Seidel iterative method to find the steady-state probability distribution and thus the performance measures of interest: new call blocking probability, handoff failure probability, and forced termination probability. Analytical results show that providing handoff queues in both microcells and macrocells can achieve largest performance improvement. Furthermore, handoff queue size greater than a threshold is shown to have little effect on performance measures of interest. Last but not least, the studied two-tier system is compared with a one-tier counterpart. It is shown that the two-tier system performs better in terms of average number of handoffs per fast call.

In this paper, we explore, via an extensive simulation study, the performance of a call-admission-control (CAC) and traffic-policing mechanisms proposed for transmitting multiple quality encoded videoconference movies over a wireless asynchronous transfer mode channel of high capacity, depending on the user's needs and requests. Both the CAC algorithm and the traffic-policing mechanism are novel mechanisms proposed for the first time in this paper. For their implementation, we use an estimation of the equivalent bandwidth of the movies, which has been introduced in the past. We focus on both MPEG-4 and H.263 coded movies, as the integration of such video streams has not been studied in the relevant literature. In the case of H.263 movies, our scheme achieves high aggregate channel throughput, while preserving the very strict quality-of-service requirements of the video traffic.

Resource allocation is a vital component of call-admission control that determines the amount of resource to assign to new and handoff connections for quality-of-service (QoS) satisfaction. In this paper, we present approximate analytical formulations of virtual partitioning resource-allocation schemes for handling multiclass services with guard channels in a cellular system. Resource-allocation models for best effort and guarantee access with preemption for best effort traffic and virtual partition with preemption for all classes are investigated. The analytical models, derived using a K-dimensional Markov chain, are solved using preemption rules for these schemes. Call-level grade of service, such as new-call-blocking probability, handoff-call-blocking probability, and system utilization, and packet-level QoS, such as packet-loss probability, are used as performance metrics. The performances of fast and slow mobile users are evaluated analytically and by simulation. The analytical and simulation results show excellent agreement. A method to maximize system utilization through joint optimization of call-/packet-level parameters is proposed. Numerical results indicate that significant gain in system utilization is achieved.

Using intelligent techniques to perform radio resource management is an effective method. The paper proposes neural fuzzy control for radio resource management in hierarchical cellular systems supporting multimedia services. A neural fuzzy resource manager (NFRM) is designed, which mainly contains a neural fuzzy channel allocation processor (NFCAP). The NFCAP has a two-layer architecture: a fuzzy cell selector (FCS) in the first layer and a neural fuzzy call-admission and rate controller (NFCRC) in the second layer. The FCS chooses not only the handoff failure probabilities and the resource availabilities in both microcell and macrocell, but also the user mobility, as input linguistic variables. The NFCRC takes the handoff failure probability and the resource availability of the selected cell as input variables to perform call admission control and rate control for the call. Simulation results show that the NFRM can always guarantee the quality of service (QoS) requirement for handoff failure probability for all traffic loads. Also, the NFRM improves the system utilization by 31.1% while increasing the handoff rate by 2% over the overflow channel allocation (OCA) scheme; it enhances the system utilization by 6.3% and 1.4%, and still reduces the handoff rate by 14.9% and 6.8%, as compared to the combined channel allocation (CCA) and fuzzy channel allocation control (FCAC) schemes, respectively, under a predefined QoS constraint.

We propose a network architecture for code-division multiple-access (CDMA) cellular systems based on adaptive sector coverage. We show that there is a capacity limit for a CDMA system, which for a soft limit is fairly hard. We also show that for nonhomogeneous traffic, changing the area of coverage for each sector in a sectored-cell can absorb the dynamics of the traffic. For a cell of a fixed radius, divided into n sectors, it is possible to select the angles of coverage of each sector in order to avoid excessive blocking due to temporary nonuniformity of traffic across the cell. This result is based on the fact that for a given set of system parameters (bandwidth, bit rates, E/sub b//N/sub 0/ etc.), a certain amount of area is covered. Hence, the exact shape of the cell/sector is not important. The idea presented is shown to be applicable to overlapping sectors.

Call admission control (CAC) plays a significant role in providing the desired quality of service in wireless networks. Many CAC schemes have been proposed. Analytical results for some performance metrics such as call blocking probabilities are obtained under some specific assumptions. It is observed, however, that due to the mobility, some assumptions may not be valid, which is the case when the average values of channel holding times for new calls and handoff calls are not equal. We reexamine some of the analytical results for call blocking probabilities for some call admission control schemes under more general assumptions and provide some easier-to-compute approximate formulas.

Wireless information networks need to employ small radio cells to support large user populations. However, this will impose extra burden on network traffic control as a result of frequent handover behavior. Existing approaches to support a high handover rate still have cell loss and cell out-of-sequence penalty while the handover is in progress. This paper proposes a novel handover protocol that can avoid cell loss and guarantee cell sequence. It can enhance the performance of a microcellular asynchronous transfer mode network. By multicasting cells to a new base station before handover, our scheme can avoid cell loss and support a nonoverlapping microcell environment as well. The multicast of signaling messages during handover is to coordinate the cell transmission order between the old base station and the new base station to guarantee cell sequence. A formal representation of the handover protocol using finite-state diagrams has been developed to specify and verify the protocol. To guarantee quality of service, we present a hierarchical wireless call admission control to limit the number of in-progress connections and to prevent radio channel congestion. Mathematical models have been developed to analyze two quality-of-service parameters: handover dropping probability and forced termination probability. Experimental results show that our hierarchical wireless call admission control can effectively lower the handover dropping probability and the forced termination probability in comparison with the single-layer wireless call admission control.

Call admission control can significantly affect the performance of a cellular system by adding additional bandwidth to a wireless network. In this paper, we show how call admission control can be used to optimize the performance of a hierarchical cellular system. The hierarchical system we study is based on a novel frequency planning scheme, whereby both the micro and macro layers can share the same spectrum and a hard partition of the frequency spectrum is not needed. The original analysis of the hierarchical system showed that a significant capacity gain can be achieved by the scheme. However, this capacity is gained at the expense of the carrier-to-interference ratio (C/I) performance of the macrocells. In this paper, we show that call admission control can be used in hierarchical cellular systems to achieve a capacity gain without sacrificing the C/I performance of the macrocells.

Soft handoff techniques in direct-sequence code-division multiple-access (DS-CDMA) systems provide mobile calls with seamless connections between adjacent cells. Channel reservation schemes are used to give high priority to more important soft handoff attempts over new call attempts. However, since the number of soft handoff attempts varies according to environmental conditions, fixed reservation schemes for handoff attempts can be inefficient. An adaptive channel reservation scheme is herein proposed to control the size of reservation capacity according to varying the number of soft handoff attempts. The proposed scheme also includes a balancing procedure between soft handoff failure and new call blocking to maximize the system capacity. To evaluate the performance of the proposed scheme, a Markovian model is developed that considers the interference-limited capacity effect of DS-CDMA systems. The analytical result shows that the proposed scheme yields a considerable enhancement in terms of new call blocking and soft handoff failure probabilities when compared with the conventional fixed channel reservation scheme.

A unique feature of code division multiple access (CDMA) systems is the use of soft handoff between cells. Soft handoff, in general, increases the system capacity because while the link between a mobile and one base station is poor, it might be better between the same mobile and some other base station. Hence, the user may transmit at a lower power in a soft handoff situation. Teletraffic analysis of soft handoff is complex because one cannot separate transmission issues from traffic issues. Many papers in the literature have independently analyzed the effect of soft capacity and soft handoff on network performance. Some papers have analyzed the effect of soft handoff on soft capacity but there has been no proper teletraffic analysis that includes both soft capacity and soft handoff. This paper proposes a traffic model for a DS-CDMA cellular network that includes both soft capacity and soft handoff. Network performance is then computed in terms of call blocking.

Analytical models are proposed for various direct sequence code-division multiple-access (DS/CDMA) call admission control schemes. Many mathematical call admission models for DS/CDMA cellular networks have been proposed. However, they have shortcomings. First, by ignoring the stochastic traffic load variation or call blocking effect, they failed to sufficiently characterize the second moment of other-cell interference. This leads to inaccurate analysis of a real network. Second, the optimal control parameters were often obtained through an exhaustive search which was very time consuming. Finally, the estimation of system capacity in previous models was obtained by using a simple one-slope path-loss propagation model. However, it is well known that a two-slope path loss propagation model is needed in a line-of-sight (LOS) microcell propagation environment. We propose an analytical model for call admission to overcome these drawbacks. In addition, we combine a modified linear programming technique with the built analytical model to find better call admission control schemes for a DS/CDMA cellular network.

Capacity estimation in code division multiple access (CDMA) systems is an important issue which is closely related to power control. Many previous studies assumed strength-based power control, which maintains received power at a desired level regardless of changes in the number of active users and in the amount of total other cell interference. However, in signal-to-interference ratio (SIR)-based power control systems, which maintain the received SIR at a desired level, the power level is a function of the above two variables. This study derives the reverse link capacity of an SIR-based power control system supporting ON-OFF traffic in a multiple cell environment. Two different power control systems are compared in terms of capacity in both CBR and ON-OFF traffic environments. The effects of activity factor, the required E/sub b//I/sub o/, the maximum received power, and propagation parameters are also investigated.

This paper analyzes the feasibility and potential benefits of following a novel design strategy for cellular systems known as partial loading. This strategy seeks low channel occupancy per cell at the capacity limit, as opposed to the high channel occupancy per cell of more conventional design strategies. By doing so, a considerable flexibility for the radio resource management is obtained, which can be exploited both to increase system capacity and to ease the accommodation of highly fluctuating traffic. A comprehensive system capacity analysis has been performed, based on an analytical model, and it is shown that the introduction of flexibility through partial loading has a capacity cost associated with it. However, it is shown that when that flexibility is properly exploited by adaptive radio link control techniques, such as link adaptation, frequency hopping, or call admission control policies, that cost is more than compensated for, making the partial loading approach a very attractive strategy for the evolution of current TDMA systems and the design of future ones.

When a mobile newly arrives and seeks admission in power-controlled cellular/personal communications services (PCS) systems, interactive call admission control guides the evolution of the power transmitted by the new mobile in order to protect the transmission quality of ongoing calls from dropping below a desired level. In addition, it eventually decides whether the new mobile should be accepted or rejected without errors. However, existing interactive call admission algorithms incur high network signaling costs and suffer from slow speed in the "accept/reject" decision, which often renders the implementation of these algorithms impractical. This paper presents efficient interactive algorithms that improve the admission speed as well as curtail the network coordination cost. The algorithms are numerically evaluated with respect to the admission speed, decision error, and performance of protecting ongoing call quality. The simulation result shows that the proposed algorithms are promising for practical implementation.

In many previous low Earth orbit (LEO) satellite networks, intersatellite links (ISLs) are used to enhance the capability of the networks. The ISLs are continuously deleted and established since the visibility between satellites changes over time. These topological changes require rerouting of the traffic on ISLs, which unavoidably involves dropping of some ongoing calls. In general, such an ongoing call dropping degrades the quality-of-service (QoS) more severely than an initiated call blocking. We propose a call admission control scheme that allows a flexible tradeoff between dropped ongoing calls and blocked initiated calls. The call admission control scheme makes use of two techniques: traffic recasting and traffic projection. The traffic recasting maps the current traffic onto the network after the topological change whereas the traffic projection projects the recast traffic from the current time to the time of the topological change. The projected traffic is used to estimate the increase in ongoing call dropping whose QoS penalty is compared against that of increased newly initiated call blacking to make the call admission decision. Simulation results show that the proposed call admission control scheme significantly reduces the ongoing call dropping probability with only a marginal increase in the initiated call blocking and call completion probabilities.

We develop product form traffic models for single- and multiple-cell code-division multiple-access (CDMA) networks with multiple classes of mobile subscribers. The key feature of this development is the specification of a flexible call admission control procedure that details the numbers of mobiles of each class in each cell that the system operator should allow in order to maintain an acceptable quality of service. Effective bandwidth techniques from the analysis of statistical multiplexing at an asynchronous transfer mode (ATM) based broadband integrated services digital network (ISDN) link are used to give performance guarantees that overcome the variability in interference levels characteristic of CDMA cellular networks. The result is an admissible region bounded by a finite number of hyperplanes and a simple and efficient call admission policy. The CDMA mobile network, operating within the admissible region described, has a very similar form to a circuit-switched network operating with fixed routing. This similarity allows the existing traffic modeling techniques and network management strategies for general loss networks to be applied to CDMA mobile cellular networks. In particular, with standard assumptions on the call arrival processes and holding times, the stationary state distribution has a product form on the truncated state space defined by the call admission strategy.

Coordinated multipoint transmission (CoMP) with the joint transmission (JT) scheme is employed in cellular networks to improve data rate and cell-edge throughput and/or to increase system throughput. In CoMP-JT, since the user equipment (UE) is capable of receiving the desired signal from an adjacent cell, as well as from its serving cell, it can achieve an improved signal-to-interference ratio (SIR). However, this scheme entails exhaustion of resources in serving base stations. In this paper, we propose a call admission control scheme (CAC) to improve the performance of CoMP-JT-based cellular systems. In this CAC scheme, the CoMP-JT technique is applied to UEs located near the edge of a cell. To establish an analytical model for CoMP-JT-based cellular systems, we introduce a model for traffic analysis using a 2-D Markov chain and approximate the computation of the power sum of multiple lognormal random components in a multicell environment. Performances of CoMP-JT-based cellular systems are evaluated with respect to two quality-of-service (QoS) constraints pertaining to call-blocking and outage probabilities, respectively, from the network-layer and the physical-layer perspectives. We first measure the resource utilization and call blocking probability for the downlink resources for various offered loads in the cell. Based on that, we obtain the outage probability and effective throughput of the system. The analytical results are compared with computer simulations. Finally, we consider the dynamic point selection (DPS) scheme that is a modified version of the JT scheme, in which some resources of adjacent cells are muted.

Bandwidth is an extremely valuable and scarce resource in mobile networks; therefore, efficient mobility-aware bandwidth reservation is necessary to support multimedia applications (e.g., video streaming) that require quality of service (QoS). In this paper, we propose a distributed bandwidth reservation scheme called the mobility-prediction-aware bandwidth reservation (MPBR) scheme. The objective of MPBR is to reduce handoff call dropping rate and maintain acceptable new call blocking rate while providing efficient bandwidth utilization. MPBR consists of 1) a handoff time estimation (HTE) scheme that aims to estimate the time windows when a user will perform handoffs along the path to his destination, 2) an available bandwidth estimation (ABE) scheme that aims to estimate in advance available bandwidth, during the computed time windows in the cells to be traversed by the user to his destination, and 3) an efficient call admission control (ECaC) scheme that aims to control bandwidth allocation in the network cells. The simulation results show that MPBR outperforms existing schemes in terms of reducing handoff call dropping rate.