A Hopfield neural-network-based dynamic channel allocation withhandoff channel reservation control

As channel allocation schemes become more complex and computationally demanding in cellular radio networks, alternative computational models that provide the means for faster processing time are becoming the topic of research interest. These computational models include knowledge-based algorithms, neural networks, and stochastic search techniques. This paper is concerned with the application of a Hopfield (1982) neural network (HNN) to dynamic channel allocation (DCA) and extends previous work that reports the performance of HNN in terms of new call blocking probability. We further model and examine the effect on performance of traffic mobility and the consequent intercell call handoff, which, under increasing load, can force call terminations with an adverse impact on the quality of service (QoS). To maintain the overall QoS, it is important that forced call terminations be kept to a minimum. For an HNN-based DCA, we have therefore modified the underlying model by formulating a new energy function to account for the overall channel allocation optimization, not only for new calls but also for handoff channel allocation resulting from traffic mobility. That is, both new call blocking and handoff call blocking probabilities are applied as a joint performance estimator. We refer to the enhanced model as HNN-DCA++. We have also considered a variation of the original technique based on a simple handoff priority scheme, here referred to as HNN-DCA+. The two neural DCA schemes together with the original model are evaluated under traffic mobility and their performance compared in terms of new-call blocking and handoff-call dropping probabilities. Results show that the HNN-DCA++ model performs favorably due to its embedded control for assisting handoff channel allocation     

Admission Control Algorithms for Revenue Optimization with QoS Guarantees in Mobile Wireless Networks

We propose and analyze call admission control algorithms integrated with pricing for revenue optimization with QoS guarantees to serve multiple service classes in mobile wireless networks. Traditional admission control algorithms make acceptance decisions for new and handoff calls to satisfy certain QoS constraints such as the dropping probability of handoff calls and the blocking probability of new calls being lower than a pre-specified threshold. We analyze a class of partitioning and threshold-based admission control algorithms that make acceptance/rejection decisions not only to satisfy QoS requirements but also to optimize the revenue of the system by taking prices and arrival/departure information of service calls into account. We show that for a “charge-by-time” pricing scheme, there exist optimal resource allocation settings under which the partitioning and threshold-based admission control algorithms would produce the maximum revenue obtainable by the system without sacrificing QoS requirements. Further, we develop a new hybrid admission control algorithm which outperforms both partitioning and threshold-based admission control algorithms over a wide range of input parameters characterizing the operating environment and service workload conditions. Methods for utilizing of the analysis results for realtime admission control for revenue optimization with QoS guarantees are described with numerical data given to demonstrate the applicability.     

The Complementary Use of 3G WCDMA and GSM/GPRS Cellular Radio Networks

The traffic performance of integrated 3G wide-band code division multiple access (WCDMA) and GSM/GPRS network is evaluated. This type of network links two cellular radio systems which have different set of frequency bands and the same coverage size. The base station of 3G WCDMA is installed on an existing GSM/GPRS site. Dual-mode mobile terminals use handoff to establish calls on the better system. The soft handoff or inter-frequency hard handoff occurs when mobile terminals of 3G WCDMA or GSM/GPRS move between two adjacent cells, respectively. The inter-system hard handoffs are used between 3G WCDMA and GSM/GPRS systems. The data rate conversions between different systems, soft handoff region size, multiple data rate multimedia services, and the effect of the mobile terminal mobility on the user mean dwell time in each system are considered in the study. The simulation results demonstrate that a great traffic performance improvement on the complementary use of 3G WCDMA and GSM/GPRS cellular radio networks compared with the use of GSM/GPRS cellular radio networks. When high-data rate transmission is chosen for low-mobility subscribers, both the handoff failure probability, and carried traffic rates increase with the new call generation rate. However, both rates decrease conversely with the increasing new call generation rate as soon as the new call generation rate exceeds a critical value. This causes the integrated networks saturation. The higher mean speed for the mobile terminals produces lower new call blocking probabilities and total carried traffic. The new call blocking probabilities and total carried traffic increase with the size of the soft handoff region.     

Channel reservation for handoff calls in a PCS network

Some new performance measures and channel reservation for handoff calls for maximizing the service provider's revenue in a personal communications service (PCS) network, with general cell residence time and general requested call holding time, are investigated. Here, each cell within the PCS network consists M channels, but only when at least m+1 (0⩽m<μ) channels are available will a new originating call be accepted. A handoff attempt is unsuccessful if no channel in the target cell is available. Some new performance measures of the system such as the modified offered load (MOL) approximations of the blocking probability of new and handoff calls, the distribution and the mean actual call holding time of a new call and related conditional distributions and the expectations, as well as the boundary of the mean of the actual call holding time of an incomplete call and a complete call are obtained. A necessary and sufficient condition for maximizing the provider's revenue is achieved for any general cost structure if it is an increasing function of the actual call holding time. In order to be fair to the customers with incomplete call and complete call, two different kinds of holding costs are considered for the different customers. In both situations, the optimal controlling value m of handoff priority is obtained by maximizing the service provider's revenue     

A Prioritized Real-Time Wireless Call Degradation Framework for Optimal Call Mix Selection

This paper describes a framework for selecting the optimal call mix to be admitted while employing a bandwidth degradation policy in a wireless cellular network. The optimal property is achieved by maximizing the revenue generated by different calls in a cell for the service provider. By degradation, we mean that: (1) some channels can be taken away from ongoing calls that are assigned multiple channels, and/or (2) newly admitted calls that require multiple channels get fewer than what they requested. To avoid removing more channels from calls than they could tolerate, we incorporate a new call attribute: the degradation tolerance, i.e., the number of channels a call can be degraded without sacrificing the acceptable level of quality. We also consider priorities over calls to influence the admission and/or degradation decision. Our analytical framework includes both static and dynamic scenarios. The dynamic case is enhanced with the ability to select the optimal call mix using incoming and departing handoffs, new calls, and call terminations in a recursive way, thus, resulting in a call admission policy. We also discuss how to accommodate non-real-time calls into our system. To evaluate the performance of the proposed scheme, a discrete event simulation tool has been developed that models our dynamic framework built on a customized simulated annealing optimization function. Simulation results demonstrate that not only does the proposed degradation framework maximize the total revenue generated by the admitted calls in the cells, but also reduce the handoff and new call blocking probabilities.     

New call blocking versus handoff blocking in cellular networks

In cellular networks, blocking occurs when a base station has no free channel to allocate to a mobile user. One distinguishes between two kinds of blocking, the first is called new call blocking and refers to blocking of new calls, the second is called handoff blocking and refers to blocking of ongoing calls due to the mobility of the users. In this paper, we first provide explicit analytic expressions for the two kinds of blocking probabilities in two asymptotic regimes, i.e., for very slow mobile users and for very fast mobile users, and show the fundamental differences between these blocking probabilities. Next, an approximation is introduced in order to capture the system behavior for moderate mobility. The approximation is based on the idea of isolating a set of cells and having a simplifying assumption regarding the handoff traffic into this set of cells, while keeping the exact behavior of the traffic between cells in the set. It is shown that a group of 3 cells is enough to capture the difference between the blocking probabilities of handoff call attempts and new call attempts. This revised version was published online in July 2006 with corrections to the Cover Date.     

Modeling and Simulation of Mixed Queueing and Loss Systems

In this paper, we investigate a multi-rate network in which wide-band calls are allowed to wait if insufficient resources are available at the time of the call arrival. On the link level, an analytical model is presented and simulations have been carried out on the network level. The results indicate that allowing a few wide-band calls to queue can give a significant improvement in performance in terms of network revenue , as well as a means to level out the blocking probabilities of the different traffic classes. This improvement becomes significant when the service discipline of the waiting calls (of different bandwidth requirements) is adaptive in the sense that longer queues get served first. This observation motivates the investigation of the impact of various buffer space assignment and queueing disciplines on network revenue and call blocking probabilities. The study of such mixed delay and queueing networks is motivated by its possible applications to traffic problems in future Broadband Integrated Services Digital Networks as well as in multi-rate cellular radio networks.     

Performance analysis of a cellular network with multiple classes of calls

In this paper, we study a cellular mobile communications network with multiple cells and multiple classes of calls. The different classes of calls have different call holding times and residence time distributions. We consider a protocol mechanism under which a blocked call in a cell is either disconnected from the network or is deemed as a handoff call in a neighboring cell. Under this protocol, we prove that the stationary distribution of this cellular mobile network has a product form. This allows us to derive explicit expressions for handoff rates of each class of calls from one cell to another and the disconnecting probabilities for each class of new and handoff calls. Our numerical results show how these measures depend on the mobility of the mobile terminals in each cell and on the numbers of reserved channels.     

Q-Win – A New Admission and Handoff Management Scheme for Multimedia LEO Satellite Networks

Low Earth Orbit (LEO) satellite networks are deployed as an enhancement to terrestrial wireless networks in order to provide broadband services to users regardless of their location. In addition to global coverage, these satellite systems support communications with hand-held devices and offer low cost-per-minute access cost, making them promising platform for Personal Communication Services (PCS). LEO satellites are expected to support multimedia traffic and to provide their users with the negotiated Quality of Service (QoS). However, the limited bandwidth of the satellite channel, satellite rotation around the Earth and mobility of end-users makes QoS provisioning and mobility management a challenging task. One important mobility problem is the intra-satellite handoff management. The main contribution of this work is to propose Q-Win, a novel call admission and handoff management scheme for LEO satellite networks. A key ingredient in our scheme is a companion predictive bandwidth allocation strategy that exploits the topology of the network and contributes to maintaining high bandwidth utilization. Our bandwidth allocation scheme is specifically tailored to meet the QoS needs of multimedia connections. The performance of Q-Win is compared to that of two recent schemes proposed in the literature. Simulation results show that our scheme offers low call dropping probability, providing for reliable handoff of on-going calls, good call blocking probability for new call requests, while maintaining bandwidth utilization high.     

Combined ICA and FCA Schemes for a Hierarchical Network

A combined idle channel assignment (ICA) and fixed channel assignment (FCA) scheme is proposed to improve the traffic performance in a hierarchical network. This dual-mode network integrates the Frequency Division Duplex (FDD) and Time Division Duplex (TDD) modes of the Universal Mobile Telecommunication System (UMTS) and Terrestrial Radio Access (UTRA) in a given cell. This approach includes a high traffic load area and a blocked area as an example to evaluate the traffic performance. The ICA threshold and network timeout period effects on the traffic performance of this integrated dual-mode network are also investigated. The analytical results show that the handoff failure probabilities of the integrated dual-mode network can be reduced significantly with a minimal increase in the new call blocking probability when the combined ICA and FCA scheme replaces the FCA scheme. The integrated dual-mode network using the combined ICA and FCA scheme also increases the carried traffic. The traffic performance improvements for non-uniformly generated new calls are more significant than those for uniformly generated new calls when the combined ICA and FCA scheme is used. An increase in the high ICA threshold will result in an increase in the total carried traffic and an increase in the new call blocking and handoff failure probabilities for higher-tiered and low-tiered systems located in the high traffic load area. The traffic performance was evaluated using the discrete time simulation method to validate the analysis results.     

A Modified Distributed Call Admission Control Scheme and Its Performance

Call admission control is one of the key elements to guarantee the handoff call dropping probability in cellular networks. Among numerous proposals in the literature, the distributed call admission control policy (DCAC) seems to be promising, due to its simplicity and adaptability to changing traffic. However, one crucial assumption used in DCAC is that the actually admitted new calls has to obey a Poisson process to enter the network after the call admission control. Given the dynamic and distributed nature of the control process, this can neither be validated nor be easily implemented. In this paper, we will first discuss a generalized DCAC which eliminates the above assumption and can be used in general environments. Then, a mobility-aware DCAC is introduced, which considers the difference of handoff support between low and high mobility calls in making the CAC decision in order to improve channel utilization. The performance of the modified DCAC scheme is investigated through simulation studies.     

A channel reservation and preemption model using overlapping regions in sector‐based cellular networks

This paper presents a channel reservation and preemption (CRP) model using overlapping regions in a cellular network with multiple sectors. To fully exploit and reuse the frequencies, directional antennas are installed on base stations (BSs) to divide the coverage into a number of equal‐sized sectors. When traffic is unevenly distributed across the sectors in a BS, channel utilization in every sector may become very different; low‐traffic sectors may be underutilized while high‐traffic sectors may be overutilized. A CRP scheme is thus proposed to more efficiently utilize free channels among sectors. CRP aims at reducing the dropping probabilities of handoff calls. Specifically, when free channels in a sector are not available, a handoff call, instead of being dropped, is allowed to preempt an ongoing call residing in the overlapping region of two adjacent sectors or two neighbor cells. Under CRP, the preempted ongoing call will not be disconnected, because it can switch over its service to the BS of a neighbor cell or to another directional antenna of an adjacent sector. For the purpose of evaluation, we build an analytical model for the proposed CRP using six‐tuple Markov chains. Analytical results show that the proposed CRP can significantly reduce the dropping probabilities of inter‐sector handoff calls, particularly when traffic between two sectors is not evenly distributed. Copyright © 2013 John Wiley & Sons, Ltd.     

Efficient call admission control for heterogeneous services inwireless mobile ATM networks

An efficient call admission control scheme for handling heterogeneous services in wireless ATM networks is proposed. Quality-of-service provisioning of jitter bounds for constant bit rate traffic and delay bounds for variable bit rate traffic is used in the CAC scheme to guarantee predefined QoS levels for all traffic classes. To reduce the forced handoff call dropping rate, the CAC scheme gives handoff calls a higher priority than new calls by reserving an appropriate amount of resources for potential handoff calls. Resource reservation in the CAC scheme makes use of user mobility information to ensure efficient resource utilization. Simulation results show that the proposed CAC scheme can achieve both low handoff call dropping rate and high resource utilization     

Adaptive resource allocation for prioritized call admission over anATM-based wireless PCN

In future personal communications networks (PCNs) supporting network-wide handoffs, new and handoff requests will compete for connection resources in both the mobile and backbone networks. Forced call terminations due to handoff call blocking are generally more objectionable than new call blocking. The previously proposed guard channel scheme for radio channel allocation in cellular networks reduces handoff call blocking probability substantially at the expense of slight increases in new call blocking probability by giving resource access priority to handoff calls over new calls in call admission control. While the effectiveness of a fixed number of guard channels has been demonstrated under stationary traffic conditions, with nonstationary call arrival rates in a practical system, the achieved handoff call blocking probability may deviate significantly from the desired objective. We propose a novel dynamic guard channel scheme which adapts the number of guard channels in each cell according to the current estimate of the handoff call arrival rate derived from the current number of ongoing calls in neighboring cells and the mobility pattern, so as to keep the handoff call blocking probability close to the targeted objective while constraining the new call blocking probability to be below a given level. The proposed scheme is applicable to channel allocation over cellular mobile networks, and is extended to bandwidth allocation over the backbone network to enable a unified approach to prioritized call admission control over the ATM-based PCN     

多业务无线蜂窝移动通信系统的一种呼叫允许控制策略

第三代移动通信系统要求支持宽带多媒体业务,如话音、视频、数据等多种业务,不同业务有不同的QoS要求。本文提出的多业务无线蜂窝移动通信系统中一种基于QoS的呼收允许控制策略,对不同业务的切换呼叫给予不同的优先权。本文分析了两种呼叫允许控制（CAC）算法,一种是各种业务的切控呼叫无缓冲器,不进入排队系统;另一种是各种业务的切换呼叫设置有缓冲器,进入排除系统,并且话音、视频业务的切切呼叫比数据业务的切换呼叫有更高的优先权,系统的空闲信道应首先分配给话音、视频业务的切换呼叫,再分配给数据业务的切换呼叫。在分析两种CAC算法的呼叫阻塞概率、切换失败概率以及系统吞吐量的基础上,给出了计算机仿真结果。     

Handoff performance in wireless DS‐CDMA networks

This paper analyses the performance of DS‐CDMA networks in the presence of call handoffs. We show that a handoff may violate the SINR requirements for other users, and thus cause an outage in the target cell. We propose to use the probability of such events as a possible metric for quality of service in networks with multiple traffic types, and derive the corresponding QoS parameters. A two‐level admission policy is defined: in tier 1 policy, the network capacity is calculated on the basis of the bound on outage probability. However, this policy does not suffice to prevent outage events upon handoffs for various traffic types, and henceforth, we propose an extension that reserves extra bandwidth for handoff calls, thus ensuring that handoff calls will not violate the outage probability bound. The overhead imposed by the extension is negligible, as the complete two‐tier admission control algorithm is executed only when a call is admitted into the network. Once admitted, calls can freely execute handoffs using the reserved bandwidth. The modified second‐tier bandwidth reservation policy is adaptive with respect to the traffic intensity and user's mobility and we show that it can provide satisfactory call (flow) quality during its lifetime. Analytical results for the QoS have been verified by the simulations. Copyright © 2002 John Wiley & Sons, Ltd.     

An efficient vertical handoff scheme for microcellular and macrocellular interworking

The next generation wireless network environments increasingly become integrated to support anywhere, anytime connectivity for various applications like multimedia, full‐motion video and high data rates with appropriate quality of service (QoS). With these emerging needs, interworking of microcellular and macrocellular networks has been accompanied by service providers. However, these networks have different technologies, which make efficient vertical handoff a challenging issue. In this study, an efficient vertical handoff scheme (EVHS) for interworking between microcellular and macrocellular networks is proposed and analyzed. The handoff decision criteria of the proposed scheme include crucial features like user mobility, network conditions, pricing issues, and user preferences in addition to the received signal strength (RSS). EVHS ensures the selection of the most appropriate network in terms of cost and acceptable QoS according to users' preferences. The results show that EVHS scheme outperforms other proposed schemes in the literature in terms of incompletion probabilities, grade of service (GoS) and cost without causing degradation in system utilization. Besides, although EVHS scheme is mainly intended for user satisfaction, the results show that it does not cause a significant degradation in the revenue of the service provider. Copyright © 2009 John Wiley & Sons, Ltd.     

DiffServ resource allocation for fast handoff in wireless mobileInternet

The next-generation wireless networks are evolving toward a versatile IP-based network that can provide various real-time multimedia services to mobile users. Two major challenges in establishing such a wireless mobile Internet are support of fast handoff and provision of quality of service (QoS) over IP-based wireless access networks. In this article, a DiffServ resource allocation architecture is proposed for the evolving wireless mobile Internet. The registration-domain-based scheme supports fast handoff by significantly reducing mobility management signaling. The registration domain is integrated with the DiffServ mechanism and provisions QoS guarantee for each service class by domain-based admission control. Furthermore, an adaptive assured service is presented for the stream class of traffic, where resource allocation is adjusted according to the network condition in order to minimize handoff call dropping and new call blocking probabilities     

Approximation models of wireless cellular networks using momentmatching

In this paper we present an analytical model for micro- and pico-cell wireless networks for any arbitrary topology in a high mobility feedforward environment. We introduce an approximation technique which uses a single-cell decomposition analysis which incorporates moment matching of handoff processes into the cell. The approximation technique can provide close approximations for non-Poisson arrival traffic and it is easily parallelized. Performance measures such as new calls blocked, handoff calls lost, and forced termination are derived for any general independent call arrival distribution in a heterogeneous traffic environment. We produce some numerical examples for some simple topologies with varying mobility for several call arrival distributions and compare our results to those from simulation studies     

Analysis of a hybrid cutoff priority scheme for multiple classes of traffic in multimedia wireless networks

In this paper, we propose and analyze the performance of a new handoff scheme called hybrid cutoff priority scheme for wireless networks carrying multimedia traffic. The unique characteristics of this scheme include support for N classes of traffic, each may have different QoS requirements in terms of number of channels needed, holding time of the connection and cutoff priority. The proposed scheme can handle finite buffering for both new calls and handoffs. Futhermore, we take into consideration the departure of new calls due to caller impatience and the dropping of queued handoff calls due to unavailability of channels during the handoff period. The performance indices adopted in the evaluation using the Stochastic Petri Net (SPN) model include new call and handoff blocking probabilities, call forced termination probability, and channel utilization for each type of traffic. Impact on the performance measures by various system parameters such as queue length, traffic input and QoS of different traffic has also been studied. This revised version was published online in June 2006 with corrections to the Cover Date.