Deterministic on-line call control in cellular networks

We study an on-line call control problem in cellular networks that are based on the Frequency Division Multiplexing (FDM) technology. In such networks, interference may occur when the same frequency is assigned to two different calls emanating from the same cell or its neighboring cells. The number of frequencies supporting the networks is limited. The goal is to maximize the number of calls served without causing any interference. We focus on the case that the number of frequencies is sufficiently large and the calls stay forever. We give a deterministic on-line algorithm with asymptotic competitive ratio of 2.5 and show a general lower bound of 2. For the special case of linear cellular networks, we achieve a best possible deterministic on-line algorithm with asymptotic competitive ratio of 3/2.     

A self-learning call admission control scheme for CDMA cellular networks

In the present paper, a call admission control scheme that can learn from the network environment and user behavior is developed for code division multiple access (CDMA) cellular networks that handle both voice and data services. The idea is built upon a novel learning control architecture with only a single module instead of two or three modules in adaptive critic designs (ACDs). The use of adaptive critic approach for call admission control in wireless cellular networks is new. The call admission controller can perform learning in real-time as well as in offline environments and the controller improves its performance as it gains more experience. Another important contribution in the present work is the choice of utility function for the present self-learning control approach which makes the present learning process much more efficient than existing learning control methods. The performance of our algorithm will be shown through computer simulation and compared with existing algorithms.     

Mobility-based predictive call admission control and bandwidth reservation in wireless cellular networks

This paper presents call admission control and bandwidth reservation schemes in wireless cellular networks that have been developed based on assumptions more realistic than existing proposals. In order to guarantee the handoff dropping probability, we propose to statistically predict user mobility based on the mobility history of users. Our mobility prediction scheme is motivated by computational learning theory, which has shown that prediction is synonymous with data compression. We derive our mobility prediction scheme from data compression techniques that are both theoretically optimal and good in practice. In order to utilize resource more efficiently, we predict not only the cell to which the mobile will handoff but also when the handoff will occur. Based on the mobility prediction, bandwidth is reserved to guarantee some target handoff dropping probability. We also adaptively control the admission threshold to achieve a better balance between guaranteeing handoff dropping probability and maximizing resource utilization. Simulation results show that the proposed schemes meet our design goals and outperform the static-reservation and cell-reservation schemes.     

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.     

Integration of pricing with call admission control to meet QoS requirements in cellular networks

Call admission control (CAC) plays a significant role in providing the desired quality of service (QoS) in cellular networks. We investigate the role of pricing as an additional dimension of the call admission control process in order to efficiently and effectively control the use of wireless network resources. First, we prove that, for a given wireless network, there exists a new call arrival rate which can maximize the total utility of users while maintaining the required QoS. Based on this result and observation, we propose an integrated pricing and call admission control scheme where the price is adjusted dynamically based on the current network conditions in order to alleviate the problem of congestion. Our proposed integrated approach implicitly implements a distributed user-based prioritization mechanism by providing negative incentives according to the current network conditions and therefore shaping the aggregate traffic in the network. We compare the performance of our approach in terms of congestion prevention, achievable total user utility, and obtained revenue, with the corresponding results of conventional systems where pricing is not taken into consideration in the call admission control process. These performance results verify the considerable improvement that can be achieved by the integration of pricing in the call admission control process in cellular networks.     

Joint call and packet QoS in cellular packet networks

This paper proposes a novel call admission control scheme capable of providing a combination of call and packet level quality of service requirements in cellular packet networks. Specifically, we propose a distributed call admission control scheme called PFG, which maximizes the wireless channel utilization subject to a predetermined bound on the call dropping and packet loss probabilities for variable-bit-rate traffic in a packet-switched wireless cellular network. We show that in wireless packet networks, the undesired event of dropping an ongoing call can be completely eliminated without sacrificing the bandwidth utilization. Extensive simulation results confirm that our scheme satisfies the hard constraint on call dropping and packet loss probabilities while maintaining a high bandwidth utilization.     

无线蜂窝网络呼叫接入控制仿真平台的设计与实现

介绍了蜂窝网络无线通信中的呼叫接入控制(CAC)的特点,描述了基于面向对象的事件驱动技术的仿真平台的设计思想和仿真系统的优化,对仿真平台的物理模型进行了分析,并给出平台的运行过程。最后给出了无预留信道和固定预留信道的接入控制算法的进行了仿真,并对仿真的结果进行了分析,试验结果符合理论分析。     

Utilizing call admission control for pricing optimization of multiple service classes in wireless cellular networks

In this paper, we utilize admission control algorithms designed for revenue optimization with QoS guarantees to derive optimal pricing of multiple service classes in wireless cellular networks. A service provider typically adjusts pricing only periodically. Once a “global” optimal pricing is derived, it would stay static for a period of time, allowing users to be charged with the same rate while roaming. We utilize a hybrid partitioning-threshold admission control algorithm to analyze a pricing scheme that correlates service demand with pricing, and to periodically determine optimal pricing under which the system revenue is maximized while guaranteeing that QoS requirements of multiple service classes are satisfied.     

An adaptive call admission algorithm for cellular networks

In this paper, we first propose a new continuous action-set learning automaton and theoretically study its convergence properties and show that it converges to the optimal action. Then we give an adaptive and autonomous call admission algorithm for cellular mobile networks, which uses the proposed learning automaton to minimize the blocking probability of the new calls subject to the constraint on the dropping probability of the handoff calls. The simulation results show that the performance of the proposed algorithm is close to the performance of the limited fractional guard channel algorithm for which we need to know all the traffic parameters in advance.     

Adaptive call admission control in circuit-switched networks

We consider threshold-based admission control policies for traffic in fixed-route circuit-switched networks, and develop a scheme for adjusting the threshold parameters online so that, as operating conditions in the network change, the thresholds "adapt" with the objective of minimizing a weighted sum of call blocking probabilities. An algorithm for estimating online the sensitivity of the call blocking metric with respect to thresholds is presented. The formal optimization problem over the set of discrete threshold parameters is solved by means of a conversion to an optimization problem over a set of auxiliary real-valued parameters. Such threshold-based policies, though conservative at low traffic rates, have the advantage of being simple to implement, distributed in nature, adaptive, and not requiring explicit distributional modeling assumptions. Numerical results included in the paper indicate that at higher traffic rates these simple policies yield the same performance as more complex and less flexible call admission schemes     

Completed analysis of cellular networks with PH-renewal arrival call

In this paper, we apply the PH-renewal process to model new call and handoff processes, and apply the matrix-analytic approach to explore the performance measures of the drop and block probabilities. We examine the bursty nature of handoff call drops by means of conditional statistics with respect to alternating block and non-block periods. Five related performance measures are derived from conditional statistics, including the long-term new call block and handoff call drop probabilities, and the three short-term measures of average length of a block period and a non-block period, as well as the conditional handoff call drop probability during a block period. These performance measures greatly assist the priority reservation handoff mechanism in determining a proper threshold guard channel in the cell. Furthermore, we derive the handoff call drop probability from the short-term performance measures of average length of a block period and a non-block period, as well as the conditional handoff call drop probability during a block period. The results presented in this paper can provide guidelines for designing adaptive algorithms to adjust the threshold in the guard channel reservation handoff scheme.     

异构蜂窝系统中动态联合呼叫接纳控制算法

针对异构蜂窝系统的接纳控制问题,设计了一种动态联合呼叫接纳控制算法。该算法采取TOPSIS法选择最优接入网,根据系统负载分布情况动态调整网络资费,对用户的接入选择决策施加影响,以均衡网络间负载;针对不同的呼叫优先级,采取多级接入阈值及动态带宽分配策略,在接入控制环节进一步改善系统性能及用户体验。仿真结果表明,该算法在重视用户偏好的同时实现了负载均衡,降低了呼叫阻塞率和掉线率。     

无线通信网络呼叫接纳控制策略研究综述

呼叫接纳控制（CAC）是无线通信网络无线资源管理中一个重要的组成部分,CAC策略依据一定的准则决定呼叫到达请求的允许接入或拒绝接入,其中策略设计的好坏直接影响着网络的性能和资源利用率。20多年来,CAC策略得到了广泛地研究,极大地改善了网络呼损率、中断率、分组延时、丢包率和吞吐率等性能。简要介绍了无线通信网络中与CAC的一些相关背景及CAC策略的功能定位与作用,重点介绍了近年来CAC研究的一些新的成果,并分析了这些成果仍然存在的一些问题,最后给出了对于CAC进一步研究的探讨。     

适合于移动多媒体网络的呼叫接纳控制算法

移动多媒体网络应该能够同时支持传统的数据业务和实时交互式多媒体业务,并能够为用户提供QoS保证.在无线移动网中提供QoS保证,呼叫接纳控制扮演着重要的角色.通过对呼叫接纳算法中资源预留方案进行了分析总结,提出了一种适合于移动多媒体网络的自适应呼叫接纳控制算法.     

一种新型的异构无线网络呼叫接纳控制算法研究

在CDMA2000蜂窝网络和WLAN组成的异构无线网络中,呼叫接纳控制算法对于提高系统资源的利用率有着非常重要的作用。根据WLAN的网络负载情况和移动用户的速度来判决是否接入WLAN;提出一种基于概率机制的CAC算法,WLAN能够限制来自于蜂窝网的VHO呼叫,减少不必要的VHO处理负荷;对新呼叫阻塞率和DVHO呼叫阻塞率进行理论分析和推导。仿真结果表明,该CAC算法能够减少不必要的重复上下垂直切换,同时将DVHO呼叫阻塞率控制在可接受的范围内。算法保证了较高的系统吞吐量,提高了系统整体性能。     

A comparison of strategies for call admission control in mobile networks

Four strategies designed to provide the advantage of the handover of calls are considered for the channel reservation in mobile cellular networks: dynamic redundancy, partial dynamic reservation, fixed reservation, and the limitation of the allowable number of new calls. The advantage of dynamic reservation is shown. For the case of two-channel systems with losses, this claim is rigorously proved.     

Traffic speed estimation based on normal location updates and call arrivals from cellular networks

Information and communication technologies have improved the quality of Intelligent Transportation Systems (ITS). By estimating from Cellular Floating Vehicle Data (CFVD) is more cost-effective, and easier to acquire than traditional ways. In this paper, this study proposes a novel approach to evaluate the relation of normal location update, call arrivals, traffic flow, and traffic density. Moreover, the traffic speed is estimated by the proposed approach according to CFVD. In the simulation, this study compares the real traffic information with the estimated traffic information by Vehicle Detector (VD). The experiment results show that the accuracy of traffic speed estimation is 92.92%. Therefore, the proposed approach can be used to estimate traffic speed from CFVD for ITS.     

A unified approach to analyzing models of cellular communication networks with data call buffering

A unified approach to the analysis of models of cellular communication networks with queues of data calls was developed. Consideration was given to the models with two types of strategies for admission to the cell channels and the buffer. In one strategy, admission to the voice call channels is based on reservation of channels for handover of calls of the given type, and in the other strategy, on the scheme of truncating the calls of the given type. In both models, the strategy of buffer admission by the data calls relies on the scheme of place reservation for handover of the calls of the given type. The models with finite and infinite data call queues were studied. For different admission strategies, algorithms to calculate the servicing performance indices were given, and the results of their comparative analysis were presented.     

Adaptive bandwidth reservation and admission control in QoS-sensitive cellular networks

How to keep the probability of hand-off drops within a prespecified limit is a very important quality-of-service (QoS) issue in cellular networks because mobile users should be able to maintain ongoing sessions even during their hand-off from one cell to another. We design and evaluate predictive and adaptive schemes for bandwidth reservation for the hand-offs of ongoing sessions and the admission control of new connections. We first develop a method to estimate user mobility based on an aggregate history of hand-offs observed in each cell. This method is then used to probabilistically predict mobiles' directions and hand-off times in a cell. For each cell, the bandwidth to be reserved for hand-offs is calculated by estimating the total sum of tractional bandwidths of the expected hand-offs within a mobility-estimation time window. Three different admission-control schemes for new connection requests using this bandwidth reservation are proposed. We also consider variations that utilize the path/location information available from the car navigation system or global positioning system. Finally, we evaluate the performance of the proposed schemes extensively to show that they meet our design goal and outperform the static reservation scheme under various scenarios.     

Call admission control policies in cellular wireless networks with spectrum renting

Radio spectrum is scarce and precious resource in wireless networks. To efficiently utilize radio spectrum, a wireless network can rent radio channels from another wireless network and returns back the rented channels when the rented channels are required to be withdrawn. The rental and withdrawal of radio channels result in two phenomena: (i) variable number of radio channels in a wireless network and (ii) call dropping due to the channel withdrawal. Call admission control aims to provide good quality-of-services for mobile users while efficiently utilize radio channels. Many call admission control policies in the previous literatures were studied without the two phenomena. In this paper, we study three call admission control policies, namely, fixed-reservation policy, single-threshold policy and multiple-threshold policy in a wireless network which rents channels from another wireless network. We develop numerical analyses to analyze and compare the performances of the three call admission control policies. Numerical results show that the multiple-threshold policy produces higher throughput than the single-threshold and fixed-reservation policies under the same constraint of quality-of-services.