Actual call connection time characterization for wireless mobile networks under a general channel allocation scheme

Actual call connection time (ACCT) is the total time that a mobile user engages in communications over a wireless network during a call connection. Due to limited network resources of wireless mobile networks, a call connection may be prematurely disconnected and the ACCT for the call in general may not be the same as the requested call connection time (RCCT). The ACCT depends not only on the RCCT, but also on the network resource allocation scheme and network traffic. We characterize the ACCT and related performance metrics for wireless mobile networks under a newly proposed general channel allocation scheme. This scheme generalizes the nonprioritized scheme, the reserved channel scheme, the queueing priority scheme and the subrating scheme in such a way as to reduce the blocking probability of the handoff calls while keeping the ACCT as long as possible. Explicit formulae for the distribution and the expectation of the ACCT are obtained. The call completion probability, the call drop probability, and the average actual call connection times for both the complete calls and the incomplete calls are derived. The results can form the basis for designing better billing rate schemes by differentiating incomplete calls and complete calls.     

Vertical handoffs in wireless overlay networks

No single wireless network technology simultaneously provides a low latency, high bandwidth, wide area data service to a large number of mobile users. Wireless Overlay Networks - a hierarchical structure of room-size, building-size, and wide area data networks - solve the problem of providing network connectivity to a large number of mobile users in an efficient and scalable way. The specific topology of cells and the wide variety of network technologies that comprise wireless overlay networks present new problems that have not been encountered in previous cellular handoff systems. We have implemented a vertical handoff system that allows users to roam between cells in wireless overlay networks. Our goal is to provide a user with the best possible connectivity for as long as possible with a minimum of disruption during handoff. Results of our initial implementation show that the handoff latency is bounded by the discovery time, the amount of time before the mobile host discovers that it has moved into or out of a new wireless overlay. This discovery time is measured in seconds: large enough to disrupt reliable transport protocols such as TCP and introduce significant disruptions in continuous multimedia transmission. To efficiently support applications that cannot tolerate these disruptions, we present enhancements to the basic scheme that significantly reduce the discovery time without assuming any knowledge about specific channel characteristics. For handoffs between room-size and building-size overlays, these enhancements lead to a best-case handoff latency of approximately 170 ms with a 1.5% overhead in terms of network resources. For handoffs between building-size and wide-area data networks, the best-case handoff latency is approximately 800 ms with a similarly low overhead. This revised version was published online in June 2006 with corrections to the Cover Date.     

Distributed call admission control in mobile/wireless networks

The major focus of this paper is distributed call admission control in mobile/wireless networks, the purpose of which is to limit the call handoff dropping probability in loss systems or the cell overload probability in lossless systems. Handoff dropping or cell overload are consequences of congestion in wireless networks. Our call admission control algorithm takes into consideration the number of calls in adjacent cells, in addition to the number of calls in the cell where a new call request is made, in order to make a call admission decision. This is done by every base station in a distributed manner without the involvement of the network call processor. The admission condition is simple enough that the admission decision can be made in real time. Furthermore, we show that our distributed call admission control scheme limits the handoff dropping or the cell overload probability to a predefined level almost independent of load conditions. This is an important requirement of future wireless/mobile networks with quality-of-service (QoS) provisioning     

Priority-determined multiclass handoff scheme with guaranteed mobile QoS in wireless multimedia networks

The provision of multiclass services is gaining wide acceptance and will be more ubiquitous in future wireless and mobile systems. The crucial issue is to provide the guaranteed mobile quality of service (QoS) for arriving multiclass calls. In multimedia cellular networks, we should not only minimize the dropping rate of handoff calls, but also control the blocking rate of new calls at an acceptable level. This paper proposes a novel multiclass call-admission-control mechanism that is based on a dynamic reservation pool for handoff requests. In this paper, we propose the concept of servicing multiclass connections based on priority determination through the combined analysis of mobile movement information and the desired QoS requirements of multimedia traffic. A practical framework is provided to determine the occurrence time of handoff-request reservations. In our simulation experiments, three kinds of timers are introduced for controlling the progress of discrete events. Our simulation results show that the individual QoS criteria of multiclass traffic such as the handoff call-dropping probability can be achieved within a targeted objective and the new-call-blocking probability is constrained to be below a given level. The proposed scheme is applicable to channel allocation of multiclass calls over high-speed wireless multimedia networks.     

A Dynamic Reservation-Based Call Admission Control Algorithm for Wireless Networks Using the Concept of Influence Curve

In this paper a dynamic channel reservation and call admission control scheme is proposed to provide QoS guarantees in a mobile wireless network using the concept of influence curve. The basic idea behind the proposed scheme is that a moving user, in addition to its requirements in the current cell, exerts some influence on the channel allocation in neighboring cells. Such an influence is related to the moving pattern of the users and is calculated statistically. Furthermore we developed a general analytical model to calculate the corresponding blocking probabilities for wireless networks with multiple platforms, which removes the commonly used assumption that new calls and handoff calls have same channel holding time. The numerical results demonstrate that our scheme outperforms traditional channel reservation schemes and can effectively adapt to the real time network conditions.     

Proactive load balancing with admission control for heterogeneous overlay networks

The next generation wireless networks will be the coexistence of heterogeneous wireless technologies. Balancing the traffic load among different networks can effectively utilize the overall radio resources in the system. In this paper, we propose an efficient load balancing scheme for the heterogeneous overlay systems, which is applied in the call admission control process. If the available network(s) cannot provide enough resource for the request call without degrading the quality‐of‐service (QoS) obtained by the ongoing calls, the system will perform load balancing operations first by initiating vertical handoffs among networks in order to create more rooms for the request call. The load balancing algorithm is to minimize the variance between the network utilizations of the entire system, which can be formulated as a quadratic binary programming problem. Simulation results show that the proposed scheme can admit more calls into the system compared with the other three reference schemes and then improve the overall throughput. Meanwhile, the scheme can keep the networks working in effective states and provide a better QoS support for users. Copyright © 2011 John Wiley & Sons, Ltd.     

Performance Evaluation of Non-prioritized and Prioritized Call Admission Control Schemes in Wireless Cellular Networks

In cellular wireless networks, the choice of Call Admission Control scheme impacts the performance of the system, particularly as how calls are managed when a mobile user is handed off from one cell to another. Non-prioritized schemes treat handoff calls and new calls equally, while, prioritized schemes give higher priority to handoff calls. In this paper, some of the popular non-prioritized and prioritized Call Admission Control schemes were investigated and their behavior was simulated and analyzed. They are evaluated based on call dropping probability, call blocking probability and system utilization parameters.     

DynaMO: A Topology-Aware P2P Overlay Network for Dynamic,Mobile Ad-Hoc Environments

Due to the key differences between wired and ad-hoc wireless networks, traditional networking services and techniques are not always easily portable from an infrastructure based network to a wireless environment. One of the most prominent examples is the TCP transport protocol, which performs only poorly in wireless ad-hoc networks. The Peer-to-Peer (P2P) overlay networks recently developed all target the Internet where a lot of performance issues can be neglected or can be completely ignored. In addition, assumptions made for infrastructure based networks cannot be made in an ad-hoc environment, such as a fixed set of nodes which are always available. This article presents a P2P network tailored towards mobile ad-hoc environments. It utilizes proximity information to efficiently generate an overlay structure which reflects the underlying physical network topology. This way, physical routing path lengths stretched by the overlay routing process are reduced. As a novelty it does not rely on a fixed set of nodes and adapts to changes in the physical network topology. A prominent property of the overlay construction process is that the communication overhead is reduced to a minimum. Additionally, the P2P network presented maintains an even Overlay ID distribution which is deliberately given up by some solutions previously developed for wired networks. The basis of this new overlay network is Pastry, a P2P substrate based on the concept of a distributed hash table. Two different bootstrap strategies were developed and analyzed, both explicitly designed to work in dynamic and mobile networks such as ad-hoc networks.     

应用于第3代无线IP网络中的自适应资源分配方案的研究

3G(第3代)系统可支持全IP的体系结构,以便灵活地部署IP技术,同时提供实时和非实时的服务.为了减少切换过程中的分组丢失和时延,文中提出了一种新的切换方案,它利用了同时多重绑定的概念;也提出了一种根据网络状况为呼叫请求分配资源的自适应资源分配方案,在这一方案中,可以通过减少正在进行的呼叫所占带宽来尽量降低切换呼叫的掉话率和始发呼叫的阻塞率.     

Network-aware P2P file sharing over the wireless mobile networks

With the coming wireless mobile networks era and the popular use of P2P applications, how to improve the resource retrieval and discovery for P2P file sharing applications in wireless mobile networks becomes a critical issue. In this paper, we propose a novel network-aware P2P file architecture and related control schemes that can provide continuous resource retrieval and discovery for mobile users over the wireless network environment. The proposed architecture divides a P2P file sharing network into multiple network-aware clusters, in which peers are assigned to a network-aware cluster using a network prefix division. Accordingly, there are two designs for supporting mobile peers to retrieve files in wireless mobile networks. First, a novel file discovery control scheme named mobility-aware file discovery control (MAFDC) scheme is devised to obtain fresh status of shared peers and find the new resource providing peers in wireless mobile networks. Second, a resource provider selection algorithm is devised to enable a mobile peer to select new resource providing peers for continuous file retrieval     

Call admission control for voice/data integration, in.broadband, wireless networks

This paper addresses bandwidth allocation for an integrated voice/data broadband mobile wireless network. Specifically, we propose a new admission control scheme called EFGC, which is an extension of the well-known fractional guard channel scheme proposed for cellular networks supporting voice traffic. The main idea is to use two acceptance ratios, one for voice calls and the other for data calls in order to maintain the proportional service quality for voice and data traffic while guaranteeing a target handoff failure probability for voice calls. We describe two variations of the proposed scheme: EFGC-REST, a conservative approach which aims at preserving the proportional service quality by sacrificing the bandwidth utilization, and EFGC-UTIL, a greedy approach which achieves higher bandwidth utilization at the expense of increasing the handoff failure probability for voice calls. Extensive simulation results show that our schemes satisfy the hard constraints on handoff failure probability and service differentiation while maintaining a high bandwidth utilization.     

An overlay and distributed approach to node mobility in multi-access wireless networks

Nowadays many manufacturers are building mobile devices with multiple interfaces. Thus, users have access to different types of wireless access networks, which often, as for WLAN and cellular systems, coexists independently. The challenge is to make such multiple access networks to cooperate to have ubiquitous access and enhanced user quality of service. In this paper we present a scheme to allow inter-technology mobility by the introduction of an overlay network, which works on top of current (and future) networks. The proposed architecture controls all the aspect related to the mobility management: mobile node localization, handover decision and execution. The approach is distributed: it is the mobile node that decides which network to use, based on the offered service quality and the cost of the communication of the available networks, and triggers the handover execution directly to the corresponding host, using optimized SIP-based procedures. The overlay network copes with the mobile node localization. We implemented our solution in the laboratory to prove its validity and to test performance using real equipment. We also simulated the scheme using ns-3 to extend the evaluation to large scale deployments. In both test environments, our solution demonstrates high accurateness in selecting the network with the best quality as well as in supporting seamless vertical handover.     

Handoff priority scheme with preemptive, finite queueing and reneging in mobile multiservice networks

A scheme supporting voice and data calls with some grade of service (GoS)¹ guarantee in mobile multiservice networks is proposed. In this system, voice calls have preemptive priority over data calls. Preempted data calls can wait in a queue for a random patience time after which they leave the queue. A data call can be preempted only if there is space left in the finite size queue. To assess the performance of this system, an analytical model is given and performance metrics such as call blocking, call dropping and call non‐completion probabilities are investigated. Although this scheme is a generic model, it can be easily adapted to take into account the specific definitions of practical and commercial data service standards in wireless mobile networks such as GPRS or DECT. This revised version was published online in June 2006 with corrections to the Cover Date.     

Scalable peer-to-peer resource discovering scheme for wireless self-organized networks

Peer-to-peer technologies have attracted increasing research attention with fruitful protocols and applications proposed for wired networks. As to mobile environments, there are currently no mature deployments. A novel resource managing and discovering protocol, Cheer, is proposed to realize scalable and effective peer-to-peer lookup in wireless self-organized networks. Cheer resolves the topologies mismatch problem between peer-to-peer overlay networks and actual nodes distribution, allowing for frequent nodes membership changes. With specially designed resource storage table, Cheer also supports multikey and fuzzy lookup. Its hybrid architecture and improved routing scheme based on small-world theory may realize effective lookup routing. Theoretical analysis and simulation results both prove that Cheer makes using peer-to-peer applications in large-scale self-organized mobile networks feasible and promising.     

An efficient handoff management scheme for mobile wireless ATMnetworks

A new handoff management scheme for wireless ATM networks is proposed. In this scheme, all cells are connected to their neighboring cells by permanent virtual circuits (PVCs) and to the access switch (AS) by switched virtual circuits (SVCs) which are only for new calls. Some carefully chosen cells, called rerouting cells, are also connected to the AS by PVCs. In summary, if a mobile roams to an ordinary neighboring cell, its traffic path is simply elongated by a PVC connecting the old and new cells. If a mobile roams to a rerouting cell, its traffic path is rerouted to a PVC between the AS and rerouting cell. By using PVC's for handoff calls, we can guarantee fast and seamless handoff. At the same time, our scheme improves the path efficiency by limiting the maximum number of hops that a path can be extended. Also, allowing path rerouting at a suitable time means the network resources are more efficiently utilized     

Delay-Sensitive Mobile Group Services Over Cellular Networks

A scalable framework for handling delay-sensitive, real-time mobile group applications over cellular infrastructure is introduced in this work. Examples for such applications are mobile instant messaging services, mobile social networks, mobile conference calls, and mobile multi-player on-line games. The key idea is to exploit the cellular database hierarchy in order to provide group applications in an efficient manner, to scalable groups, starting from 3 to 5 members, up to a few thousands members, dispersed over a wide geographic area. The main focus is on tracking the presence and the locations of the participating members in an efficient manner, and on advanced group services, such as multicast messages and conference calls, to group members, and advanced searches such as “find the nearest taxi”. As a result, the delay associated with delivering a message to many independent users is significantly reduced, in comparison with the delay typically expected from existing cellular networks. The proposed method is consistent with the existing mobility management scheme currently used in cellular networks, and fits into MIP and MIPv6. Thus, it can be easily applied on existing cellular networks, as well as on future all-IP wireless networks.     

Adaptive Congestion Control of mSCTP for Vertical Handover Based on Bandwidth Estimation in Heterogeneous Wireless Networks

This paper proposes a new congestion control scheme of mobile Stream Control Transmission Protocol (mSCTP) for vertical handover across heterogeneous wireless/mobile networks. The proposed scheme is based on the estimation of available bandwidths in the underlying network as a cross-layer optimization approach. For congestion control of mSCTP, the initial congestion window size of the new primary path is adaptively configured, depending on the available bandwidth of the new link that a mobile node moves into. By ns-2 simulation, the proposed scheme is compared with the existing congestion control schemes in the throughput perspective. From the numerical results, we can see that the proposed mSCTP congestion control scheme could give better performance than the existing schemes in the wireless networks with an amount of background traffic.     

PCS mobility management using the reverse virtual call setupalgorithm

The increased demand for wireless mobile communications coupled with the finite available spectrum has motivated investigation into alternative methods of tracking users and delivering calls. We present a new scheme for delivering mobile terminated calls named reverse virtual call setup (RVC). Only a few new fixed network SS7 signaling messages are needed to implement this protocol; we specify them here. RVC can function within the existing cellular paging network or with an integrated overlaid paging network. The relative performance of RVC for both scenarios is investigated     

End-to-End Adaptive QoS Provisioning over GPRS Wireless Mobile Network

The General Packet Radio Service (GPRS) offers performance guaranteed packet data services to mobile users over wireless frequency-division duplex links with time division multiple access, and core packet data networks. This paper presents a dynamic adaptive guaranteed Quality-of-Service (QoS) provisioning scheme over GPRS wireless mobile links by proposing a guaranteed QoS media access control (GQ-MAC) protocol and an accompanying adaptive prioritized-handoff call admission control (AP-CAC) protocol to maintain GPRS QoS guarantees under the effect of mobile handoffs. The GQ-MAC protocol supports bounded channel access delay for delay-sensitive traffic, bounded packet loss probability for loss-sensitive traffic, and dynamic adaptive resource allocation for bursty traffic with peak bandwidth allocation adapted to the current queue length. The AP-CAC protocol provides dynamic adaptive prioritized admission by differentiating handoff requests with higher admission priorities over new calls via a dynamic multiple guard channels scheme, which dynamically adapts the capacity reserved for dealing with handoff requests based on the current traffic conditions in the neighboring radio cells. Integrated services (IntServ) QoS provisioning over the IP/ATM-based GPRS core network is realized over a multi-protocol label switching (MPLS) architecture, and mobility is supported over the core network via a novel mobile label-switching tree (MLST) architecture. End-to-end QoS provisioning over the GPRS wireless mobile network is realized by mapping between the IntServ and GPRS QoS requirements, and by extending the AP-CAC protocol from the wireless medium to the core network to provide a unified end-to-end admission control with dynamic adaptive admission priorities.     

Adaptive quality of service handoff priority scheme for mobilemultimedia networks

For various advantages including better utilization of radio spectrum (through frequency reuse), lower mobile transmit power requirements, and smaller and cheaper base station equipment, future wireless mobile multimedia networks are likely to adopt micro/picocellular architectures. A consequence of using small cell sizes is the increased rate of call handoffs as mobiles move between cells during the holding times of calls. In a network supporting multimedia services, the increased rate of call handoffs not only increases the signaling load on the network, but makes it very difficult for the network to guarantee the quality of service (QoS) promised to a call at setup or admission time. This paper describes an adaptive QoS handoff priority scheme which reduces the probability of call handoff failures in a mobile multimedia network with a micro/picocellular architecture. The scheme exploits the ability of most multimedia traffic types to adapt and trade off QoS with changes in the amount of bandwidth used. In this way, calls can trade QoS received for fewer handoff failures. The call level and packet level performance of the handoff scheme are studied analytically for a homogeneous network supporting a mix of wide-band and narrow-band calls. Comparisons are made to the performance of the nonpriority handoff scheme and the well-known guard-channel handoff scheme