Call Blocking Probability Research Articles

Cooperative load-balancing strategy based on N-hops routing algorithm of ad hoc network in heterogeneous overlapping networks

A major challenge of the heterogeneous wireless networks is how to jointly utilize the resources of different radio access technologies in an efficient manner. In this paper, system performance, such as the block probability and throughput, was investigated in communication hot spots overlapped by heterogeneous networks: cellular, WLAN, and WiMax networks. Two cooperative load-balancing strategies based on hops-limited routing algorithm of ad hoc network are proposed in order to raise the resource utilization of the whole overlapping heterogeneous networks. They both firstly make a decision whether to admit a new call or not based on common radio resource management strategies, and in overloaded condition, select certain traffic to transfer into targeted BS/AP according to minimum price strategy or minimum load BS/AP and nearest traffic strategy, which take into account these factors such as load index, number of hops, traffic prediction, cost, etc. An analytical model is used to compute the call block probability and throughput performance for two different traffic models. Simulation results show that the proposed load-balancing strategies can distribute traffics to the whole heterogeneous wireless networks, decrease the call block probability, improve system throughputs efficiently, and obviously outperform HM-MACA and HS-TC load-balancing strategies.

Analysis of Common Radio Resource Management Scheme for End-to-End QoS Support in Multiservice Heterogeneous Wireless Networks

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Future-generation wireless networks will consist of heterogeneous radio access technologies (RATs) with Internet Protocol-based infrastructure and support multiple bearer services having different quality-of-service (QoS) requirements. However, a major issue is how to jointly utilize the resources in the different RATs in an efficient manner while simultaneously achieving the desired QoS and minimizing the service cost from both the user and service provider perspectives. To resolve this issue, this paper proposes an adaptive common radio resource management (CRRM) scheme in the context of CDMA2000 and IEEE 802.11 wireless technologies, which are examples of today's wireless wide-area network (WWAN) and wireless local area network (WLAN) RATs, respectively. The key parameters of the scheme, i.e., service type, user mobility and location information, and service cost, are described. The effectiveness of the proposed CRRM scheme is analytically assessed using the theory of Markov chains. Numerical results show that the proposed CRRM scheme minimizes the rate of unnecessary vertical handoffs, thereby providing stable communication without degrading call-blocking probabilities in all mobility and loading scenarios considered. The proposed CRRM scheme also minimizes service cost, which makes it attractive for implementation in heterogeneous wireless networks. </para>

Comments on "Call Blocking Probability and Bandwidth Utilization of OFDM Subcarrier Allocation in Next-generation Wireless Networks"

We claim that the Markovian model proposed by J.-C. Chen and W.-S.E. Chen (2006) is not suitable for the intended physical system. A more adequate model is proposed, which additionally offers important advantages that are discussed in this letter.

Dynamic Resource Adjustment to Provide Seamless Streaming Services on Multimedia Mobile Cellular Networks

With the rapid advances in wireless network communication, multimedia presentation has become more applicable. However, due to the limited wireless network resource and the mobility of Mobile Host (MH), QoS for wireless streaming is much more difficult to maintain. How to decrease Call Dropping Probability (CDP) in multimedia traffic while still keeping acceptable Call Block Probability (CBP) without sacrificing QoS has become an significant issue in providing wireless streaming services. In this paper, we propose a novel Dynamic Resources Adjustment (DRA) algorithm, which can dynamically borrow idle reserved resources in the serving cell or the target cell for handoffing MHs to compensate the shortage of bandwidth in media streaming. The experimental simulation results show that compared with traditional No Reservation (NR), and Resource Reservation in the six neighboring cells (RR-nb), and Resource Reservation in the target cell (RR-t), our proposed DRA algorithm can fully utilize unused reserved resources to effectively decrease the CDP while still keeping acceptable CBP with high bandwidth utilization.

Adaptive Genetic Algorithms for Dynamic Channel Assignment in Mobile Cellular Communication Systems

Two adaptive genetic algorithms (GAs), namely GA for locking channel (GALC) and GA for switching channel (GASC), are proposed for a dynamic channel assignment in mobile cellular communication systems. The algorithms aim to minimize the blocking probability of new calls and the dropping probability of handoff calls in channelized systems, simultaneously considering three types of electromagnetic compatibility (EMC) constraints: 1) the cochannel; 2) the adjacent channel; and 3) the cosite. The proposed algorithms add a number of mechanisms to the canonical GA in order to increase their efficiency and velocity of convergence. Such mechanisms are adaptive parameters, random immigrants, a greedy policy, a reservoir to assist the initial population, a truncation selection scheme, and a three-point crossover. The GASC allows call switching between channels during the call holding time, whereas the GALC does not allow it. Computer simulations evaluated the performance of the proposed models considering a benchmark cellular environment formed by 49 cells with 70 channels and nonuniform traffic load characteristics. The impact of EMC constraints on the blocking probability of new calls and on the dropping probability of handoff calls was assessed, and the proposed models reached suitable performance. Equipment failure tests showed robust performance of the two adaptive GA schemes during the fault occurrence and recovery capability after the fault ends. The results suggest that the GASC has lower overall blocking probability of new calls than the GALC; however, the GALC may do better than the GASC in a number of combinations of handoff requests and EMC restrictions.

An HMM prediction and throttling-based call admission control scheme for wireless multimedia networks

With the increase in data transmission for wireless networks, multimedia services are gaining popularity in next-generation cellular networks. If the appropriate information exists for Call admission control (CAC) schemes, the terms of quality of service (QoS), such as call dropping probability (CDP), and call blocking probability (CBP) will be kept as low as possible, and higher system utilization can be achieved. Unfortunately, it is difficult to obtain such information owing to user indeterminate mobility. In this paper, the proposed scheme reduces the CDP with a statistical method, called Hidden Markov Models (HMM), that is suitable for solving a dynamic situation has been introduced and applied to the CAC scheme. The prediction of user mobility can be modeled and solved as an optimal-state sequence problem for the HMM. The proposed CAC method that adopts the prediction result of user mobility can reserve appropriate bandwidths for a handoff call in advance, thus, the CDP will be kept below a lower level. Moreover, the throttle flag that indicates the usage of bandwidth in each cell is proposed to prevent the new call request from being dropped in the adjacent cells if handoff is needed, and then the CDP will be further lowered. Besides, the CBP will also be kept relatively low since the proposed method can reserve the suitable bandwidths in the appropriate cells but not reserve stationary ones which are always adopted by traditional CAC methods for each cell. The simulation results show that the proposed method can meet CDP and CBP requirements, and the system utilization can also be improved.

Fairness based channel borrowing strategy in multimedia LEO satellite communications

A novel bandwidth allocation strategy along with a connection admission control technique was proposed to improve the utilization of network resources. It provides the network with better quality-of-service (QoS) guarantees, such as new call blocking probability (CBP) and handoff call dropping probability (CDP) in multimedia low earth orbit (LEO) satellite networks. Simulation results show that, compared with other bandwidth allocation schemes, the proposed scheme offers very low call dropping probability for real-time connections while, at the same time, keeping resource utilization high. Finally we discussed the fairness for the borrowed nonreal-time connections under three different channel borrowing methods.

An HMM-based call admission control policy for supporting QoS in wireless cellular networks

The multimedia services are getting to become the major trend in next-generation cellular networks. Call admission control (CAC) plays the key role for guaranteeing the quality of service (QoS) in cellular networks. The goal which keeps both the call dropping probability (CDP) and call blocking probability (CBP) below a certain level is more difficult owing to user indeterminate mobility. In this paper, the Hidden Markov Models (HMMs) concept which is suitable for solving a dynamic situation is introduced and applied to the call admission control policy. The prediction of user mobility can be modeled and resolved as the decoding problem of the HMMs. According to the prediction result, the proposed CAC method can reserve appropriate bandwidths for a handoff call beforehand. Thus, the call dropping probability can be kept below a lower level. Moreover, the call blocking probability is not sacrificed too much since the proposed method can reserve the suitable bandwidths in the appropriate cells but not reserve stationary ones which are always adopted by traditional CAC methods. Therefore, the proposed method not only can satisfy both CDP and CBP issues, but also improve the system utilization.

Grade-of-service-based routing in optical networks [Quality-of-Service-Based Routing Algorithms for Heterogeneous Networks

Optical networks serve an increasing number of services, each having different requirements. This necessitates the evolution towards routing algorithms that cover all aspects of quality. This article presents a tutorial overview and comparison of grade-of-service-based routing strategies, with emphasis on mechanisms that provide differentiated call-blocking probability for different classes of lightpath requests

A new solution to the K-shortest paths problem and its application in wavelength routed optical networks

In communication networks, traffic carried over long paths suffers from a higher call blocking probability (CBP) than those carried over short paths. This is a well-known fairness problem. Such a problem becomes more serious in wavelength-routed optical networks (WRONs) due to the wavelength continuity constraint. This paper aims to enhance the fairness characteristic in WRONs by the novel classified alternate routing (CAR) approach. As a foundation of this approach, the first K-shortest paths (KSP) between a designated source/destination node pair in a given network should be obtained simultaneously. This has been studied as the KSP problem in the literature. In this paper, a new loopless deviation (LD) algorithm for solving such a loopless KSP problem will be proposed. It outperforms existing solutions in terms of running time in real-life implementations. In order to measure the fairness characteristic, we first classify all connection requests into categories such as 1-hop traffic, 2-hop traffic, etc., according to the number of minimal hop count between the corresponding source/destination node pair. We then quantify the fairness characteristic by the ratio of the average CBP of each traffic category to that of 1-hop traffic such that CBP ratios with a value closer to 1 are preferred. We will show that such a measure criterion is more precise and robust than existing ones in the literature. Finally, numerical experiments will reveal that the CAR approach outperforms existing fairness enhancement methods when considering the comprehensive performance in terms of the balance between the fairness characteristic and the overall CBP feature.

Determination of Optimal Cell Capacity for Initial Cell Planning in Wireless Cellular Networks

In wireless cellular networks, previous researches on admission control policies and resource allocation algorithm considered the QoS (Quality of Service) in terms of CDP (Call Dropping Probability) and CBP (Call Blocking Probability). However, since the QoS was considered only within a predetermined cell capacity, the results indicated a serious overload problem of systems not guaranteeing both CDP and CBP constraints, especially in the hotspot cell. That is why a close interrelationship between CDP, CBP and cell capacity exists. Thus, it is indispensable to consider optimal cell capacity guaranteeing multiple QoS (CDP and CBP) at the time of initial cell planning for networks deployment. In this paper, we will suggest a distributed determination scheme of optimal cell capacity guaranteeing both CDP and CBP from a long-term perspective for initial cell planning. The cell-provisioning scheme is performed by using both the two-dimensional continuous-time Markov chain and an iterative method called the Gauss-Seidel method. Finally, numerical and simulation results will demonstrate that our scheme successfully determines an optimal cell capacity guaranteeing both CDP and CBP constraints for initial cell planning.

A New Fair Call Admission Control for Integrated Voice and Data Traffic in Wireless Mobile Networks

It is essential to guarantee a handoff dropping probability below a predetermined threshold for wireless mobile networks. Previous studies have proposed admission control policies for integrated voice/data traffic in wireless mobile networks. However, since QoS has been considered only in terms of CDP (Call Dropping Probability), the result has been a serious CBP (Call Blocking Probability) unfairness problem between voice and data traffic. In this paper, we suggest a new admission control policy that treats integrated voice and data traffic fairly while maintaining the CDP constraint. For underprivileged data traffic, which requires more bandwidth units than voice traffic, the packet is placed in a queue when there are no available resources in the base station, instead of being immediately rejected. Furthermore, we have adapted the biased coin method concept to adjust unfairness in terms of CBP. We analyzed the system model of a cell using both a two-dimensional continuous-time Markov chain and the Gauss-Seidel method. Numerical results demonstrate that our CAC (Call Admission Control) scheme successfully achieves CBP fairness for voice and data traffic.

A HYBRID SCHEME FOR HANDOVER IN ATM-BASED PERSONAL COMMUNICATION NETWORK

In a Personal Communication Networks (PCN), the covered geographical area is typically partitioned into a set of microcells. Each microcell has a Base Station (BS) to exchange radio signals with wireless mobile terminals. Due to the limited range of wireless transceivers, mobile users can communicate only with BSs that reside within the same microcell at any instance. The number of handoffs/handovers during a call will increase as the cell radii decrease, thus affecting the Quality of Service (QoS). Frequent handoff in wireless/mobile networks introduces a new paradigm in the area of network congestion and admission control. The increase in processing load due to demand for service and fast handoffs to mitigate the propagation effect, a high speed backbone network for the PCN to connect BS is required. The ATM technology, which has recently emerged to be a predominant switching technology, is suited to be an infrastructure to interconnect the BSs of the PCN.To support network-wide handoff, new and handoff call requests will compete for connection resources in both the mobile and backbone networks. Handoff calls require a higher congestion related performance, i.e. blocking probability, relative to new calls because forced terminations of ongoing calls due to hand-off call blocking are generally more objectionable then new call blocking from the subscriber's perspective.A hybrid scheme has been proposed for handover in ATM-based PCN, which combines queuing and reservation schemes. In the scheme, FIFO and Measurement Based Priority Scheme (MBPS) queuing discipline [Tekinay & Jabbari, 1992] and the Reserved Channel Scheme (RCS) [Kim et al., 1999] are used. This scheme gives handovers higher priority than queuing or reservation schemes. When reservation is applied on both radio and backbone channels, it leads to significant improvement in QoS. After applying proposed scheme there is a remarkable reduction in Forced Termination Probability (FTP) at the cost of tolerable Call Blocking Probability (CBP).

Call blocking probability and bandwidth utilization of OFDM subcarrier allocation in next-generation wireless networks

Various studies have devised OFDM subcarrier-allocation schemes in next-generation wireless networks. However, the subcarrier-allocation system performance has seldom been assessed, especially in terms of the call blocking probability (CBP) and bandwidth utilization.(BU). This study proposes a batch-arrival bath-loss queueing model to evaluate the performance or the subcarrier-allocation system,and derives expressions for calculating two important system performance measurements, CBP and BU. Simulation results. indicate that the measures appear to work. The model should be helpful for constructing OFDM based wireless networks

Call blocking probability and bandwidth utilization of ofdm subcarrier allocation in next-generation wireless networks

Various studies have devised OFDM subcarrier-allocation schemes in next-generation wireless networks. However, the subcarrier-allocation system performance has seldom been assessed, especially in terms of the call blocking probability (CBP) and bandwidth utilization.(BU). This study proposes a batch-arrival bath-loss queueing model to evaluate the performance or the subcarrier-allocation system,and derives expressions for calculating two important system performance measurements, CBP and BU. Simulation results. indicate that the measures appear to work. The model should be helpful for constructing OFDM based wireless networks

Threshold-Based Adaptive Call Admission Control in Hierarchical Mobile IPv6

A call admission control (CAC) scheme used in hierarchical mobile IPv6 (HMIPv6) network is proposed, which solves the ideal call number of each cell adaptively to maximize system's profits, under the restriction of system's overload probability and capacity and in terms of hosts' mobility characteristics and call characteristics. The CAC threshold of each cell used in making decisions of accepting or rejecting a new call by network is solved by establishing a Markov model in HMIPv6 network, which can make system's call number up to the ideal value. Simulation analyzes the factors affecting the optimal regional size, providing a reference for designing a dynamic regional mobility management scheme. The simulation analyses reveal that with the increase of calls' handoff probability and average duration time, the optimal regional size increases while the regional ideal call number decreases; and with the restriction of overload probability relaxes, the new call blocking probability (CBP) comes down while the handoff dropping probability (HDP) goes up. Finally, a performance comparison result between the proposed scheme and the mobile IP reservation (MIR) scheme demonstrates that the average values of CBP and HDP in the proposed scheme are lower than those in MIR during 2000 simulation intervals, which means the optimization is realized.

Survivability and performance optimization of mobile wireless communication networks in the event of base station failure

In this paper, we investigate the survivability of mobile wireless communication networks in the event of base station (BS) failure. A survivable network is modeled as a mathematical optimization problem in which the objective is to minimize the total amount of blocked traffic. We apply Lagrangean relaxation as a solution approach and analyze the experiment results in terms of the blocking rate, service rate, and CPU time. The results show that the total call blocking rate (CBR) is much less sensitive to the call blocking probability (CBP) threshold of each BS when the load is light, rather than heavy; therefore, the more traffic loaded, the less the service rate will vary. BS recovery is much more important when the network load is light. However, the BS recovery ratio (BSRR), which is a key factor in reducing the blocking rate for a small number of BSs, is more important when a system is heavily loaded. The proposed model provides network survivability subject to available resources. The model also fits capacity expansion requirements by locating mobile/portable BSs in the places they are most needed.

DYNAMIC CHANNEL RESERVATION SCHEME FOR HANDOFF PRIORITIZATION IN WIRELESS CELLULAR NETWORKS

In wireless cellular networks, in order to ensure that ongoing calls are not dropped while the users roam among cells, handoff calls may be admitted with a higher priority as compared to new calls. One way to improve system performance of cellular networks is to use efficient handover schemes when users move between cells. In this paper, a new dynamic scheme, called Dynamic Channel Reservation (DCR) is proposed and evaluated to improve the utilization of wireless network resources. The required GoS of handoff calls are guaranteed. Simulation results show that the proposed scheme improves handoff calls blocking probability in expense of an acceptable blocking probability of new calls.

Performance analysis and overflowed traffic characterization in multiservice hierarchical wireless networks

A cellular hierarchical network with heterogeneous traffic is considered, where calls with shorter (longer) average call-holding time are assigned to the associated lower (upper) layer. The main contribution of this paper is that an efficient and reasonably accurate analytical method is proposed to calculate performance measures of interest, i.e., new call-blocking probability and forced termination probability for conversational services, new call-blocking probability, forced termination probability, and the average number of assigned time slots for streaming services. In particular, a simple two-state MMPP/sup (1,2,...,K)/, that takes into account not only the dependence among overflowed calls of the same class but also the correlation among overflowed calls of different classes, is used to approximate overflowed traffic to reduce computational complexity and improve accuracy. The methods with the multiclass overflowed traffic being approximated as independent Poisson processes and interrupted Poisson processes are also conducted for comparison. Importantly, it is shown via simulation results that the proposed model generates more accurate results than those obtained with the other two approximation methods. Last but not least, the effect of nonuniform traffic density on performance measures is studied via simulation. It is shown that the nonuniform traffic density may have a significant impact on the performance.

Engset multi-rate state-dependent loss models

Call blocking probabilities (CBP) are a key index of quality of service assessment in multi-rate networks. We focus on the CBP calculation in single link loss models where calls of each service-cla...