Realistic cell-oriented adaptive admission control for QoS support in wireless multimedia networks

Adaptive call admission control for QoS provisioning in multimedia wireless networks

Next generation wireless networks target to provide quality of service (QoS) for multimedia applications. In this paper, the system supports two QoS criteria, i.e., the system should keep the handoff dropping probability always less than a predefined QoS bound, while maintaining the relative priorities of different traffic classes in terms of blocking probability. To achieve this goal, a dynamic multiple-threshold bandwidth reservation scheme is proposed, which is capable of granting differential priorities to different traffic class and to new ad handoff traffic for each class by dynamically adjusting bandwidth reservation thresholds. Moreover, in times of network congestion, a preventive measure by use of throttling new connection acceptance is taken. Another contribution of this paper is to generalize the concept of relative priority, hence giving the network operator more flexibility to adjust admission control policy by incorporating some dynamic factors such as offered load. The elaborate simulation is conducted to verify the performance of the scheme.

Dynamic rate-based borrowing scheme for QoS provisioning in high speed multimedia wireless cellular networks

In wireless networks carrying multimedia traffic, it becomes necessary to provide a quality of service (QoS) guarantee for multimedia traffic connections. A novel timing-based bandwidth allocation protocol is proposed as a solution to support QoS guarantees in the multimedia wireless networks. Based on the existing network conditions, the proposed scheme makes an adaptive decision for bandwidth reservation and call admission by employing fuzzy inference mechanism, timing based reservation strategy, and round-borrowing strategy in each base station. The amount of reserved bandwidth for each base station is dynamically adjusted, according to the online traffic information of each base station. Simulation results show that our timing-based bandwidth reservation scheme outperforms the previous schemes in terms of connection-blocking probability, connection-dropping probability, and bandwidth utilization.

This paper presents two novel heuristic algorithms for the design of wireless access multimedia networks. Emphasis was given to the design of CDMA based wireless multimedia networks and fixed wireless multimedia networks. The objectives of these methods are first to place a number of access points/base stations in a number of candidate sites and then to assign a number of fixed wireless terminals to the selected access points/base stations. Both methods are based on graph theory and they are essentially greedy algorithms. Except from capacity constraints, wireless reception characteristics are also considered. The algorithms are capable of designing medium and large-scale networks at polynomial time. Both algorithms were compared with an analogous optimisation problem through a series of tests. The results indicate that as regards design costs the performance of the heuristics is very close to this of the equivalent optimisation problem. The solution times for the heuristics are smaller especially when the number of the candidate access points/base stations becomes large

In this paper, a dynamic and adaptive bandwidth management scheme is proposed to provide as satisfactory quality-of-service (QoS) guarantee as possible for wireless multimedia services under variable traffic conditions. Under the highly variable wireless environment, the existing bandwidth management schemes result in more frequent quality changes for active flows than necessary, which are undesirable and intolerant to multimedia real-time applications. The proposed scheme is designed to provide high bandwidth utilization efficiency and low call blocking probability with minimum QoS fluctuation. In order to minimize the impact of bandwidth change for the QoS of existing flows, a controlled bandwidth degradation algorithm is performed when the free bandwidth in a cell isn't enough to admit a new flow. Compared with existing schemes, our scheme reduces the probability of frequent quality changes and provides more satisfactory services for higher priority flows. The performance analysis has shown that, under the same network load, our proposed scheme outperforms existing ones with lower QoS degradation probability.

Next-generation wireless networks have been designed to transport integrated multimedia services based on a cellular extension of a packet-switched architecture using variants of the Internet protocol (IP). Each call, arriving to or active within the network, carries demand for one or more services in parallel, where each service type has a guaranteed quality of service (QoS). Admission of new calls to the wireless IP network (WIN) from the gateway of a wired network or from a mobile subscriber (MS) is allowed by call admission control (CAC) procedures. MS roaming among the nodes of the WIN is controlled by handoff procedures between base stations (BSs), or BS controllers (BSCs), and the MSs. Both handoff and CAC procedures are typically embedded in the media access control (MAC) and logical link control (LLC) layers of the WIN protocol stack. Performance metrics, such as, probabilities of call blocking and handoff, control procedures within the WIN protocol. Earlier published results by the author present a method for the performance analysis of wireless multimedia networks based on multivariate point-process (MVPP) models and their semi-martingale representations. The models describe the finite-horizon, transient behavior of the packet flows in integrated multimedia traffic. This paper extends the earlier work to focus on the optimization of real-time control procedures embedded in the WIN protocol stack. The point processes corresponding to the packet flow of each service type and to collateral random network events are decomposed into right-continuous, pure jump processes and predictable, integrated random rate processes. Control of the set of point processes describing WIN behavior is implemented through the construction of an absolutely continuous change of a reference probability measure on network events to a controlled measure. With respect to the constructed controlled measure, the integrated random rates in the semi-martingale representations of the network point processes explicitly depend on the parameters of the protocol mechanisms for packet access, routing, switching, handoff, power control, and other resource allocations. The MVPP control approach via constructed probability measure also supports predictive models of packet flows that incorporate measurement-based estimates of the probability distributions for voice, video, data, and other Internet traffic as well as radio path distortions. Optimization of the performance metrics, represented in terms of the MVPPs and the control parameters of candidate WIN protocols for multimedia services, are discussed for both partial and complete observations of network events. The models are further used to develop optimal, recursive stochastic filters of network state, based on partial or incomplete observations of packet flow dynamics.

Next generation wireless communication systems target to provide guaranteed quality of service (QoS) for multimedia applications. In this paper, a multiple-threshold bandwidth reservation scheme combined with a call admission control algorithm is proposed and analyzed. The objective of our work is to be able to achieve better QoS provisioning for mobile users while achieving efficient utilization of the available limited bandwidth. The proposed scheme is modelled as M/M/C/C queueing system and the performance measures, call blocking probability and call dropping probability are computed. The performance of our scheme is compared to the complete sharing (CS) policy. Simulation results show that our scheme surpasses the CS policy in terms of call blocking probability, call dropping probability and bandwidth utilization.

Wireless multimedia networks are becoming very popular owing to the user demands for multimedia services. Packet dropping in the event of buffer congestion is one of the important issue in wireless multimedia networks. A packet dropping scheme has to be flexible and adaptive such that acceptable quality of an application is maintained. The paper presents a fuzzy based packet dropping scheme for wireless multimedia networks. A buffer manager placed at the base station performs packet dropping depending upon the traffic conditions and type of an application. Packet dropping is performed by computing dropping factor by considering packet priority, queue length and adaptive queue length threshold. The adaptive queue length threshold is used to dynamically adjust the dropping factor. The queue length threshold is varied by using two fuzzy input parameters, channel condition and rate of flow of an application. The scheme has been extensively simulated to test the performance in terms of acceptance and dropping probability of real-time handoff and new calls.

The major focus of this paper is distributed call admission control in mobile/wireless networks the purpose of which is to limit the call hand-off dropping probability in loss systems or the cell overload probability in lossless systems. Hand-off 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 rule 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 hand-off 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 provisioning.

MPI-QMULInformation Systems Research Centre, Macau Polytechnic InstituteMacau SAR,P. R. ChinaDepartment of Electronic Engineering, Queen MaryUniversity of LondonE-mail: xuy@mpi-gmul.org/john.bigham@elec.gmul.ac.ukAbstract: In this paper, we solve the call admission control(CAC) problem in a cellular network via a form ofNeuroEvolution algorithm. The results are compared withComplete Sharing scheme, which allows all types of traffic toaccess all available channels at all time, and show that ourproposed CAC scheme CN can reduce the handoff failuresubject to several predefined Quality of Service (QoS)constraints: the handoff dropping probability (CDR) andintra-class fairness are all guaranteed within the predefinedconstraints. Additionally, the numerical results shows thatunder the same handoff failure constraint, better fairnesscauses higher new setup calls blocking probabilities (CBR) andlower CDR, therefore the fairness and maximizing revenue aretwo opposite goals, and the fairness and CDR do not conflictwith each other.Keywords: CAC,NEAT, QoS, Fairness.

In this paper a new distributed adaptive admission control algorithm for wireless cellular networks with heterogeneous traffic is proposed. The resources needed for handoff calls are estimated by calculating the probability of visiting particular cells during the call lifetime based on the call duration and residence time statistics. This information is then communicated to the base stations in the S surrounding rings. The amount of reserved resources is updated at handoffs and call termination which involves simple arithmetic operations only. The admission algorithm also maintains the tuning parameters by which hard constraints on handoff dropping probabilities can be met. We have also derived the QoS bounds for homogeneous traffic.

The usage of voice over IP (VoIP) traffic in IEEE 802.11 wireless networks is expected to increase in the near future due to widely deployed 802.11 wireless networks and VoIP services on fixed lines. However, the quality of service (QoS) of VoIP traffic in wireless networks is still unsatisfactory. In this thesis, I identify several sources for the QoS problems of VoIP traffic in IEEE 802.11 wireless networks and propose solutions for these problems. The QoS problems discussed can be divided into three categories, namely, user mobility, VoIP capacity, and call admission control. User mobility causes network disruptions during handoffs. In order to reduce the handoff time between Access Points (APs), I propose a new handoff algorithm, Selective Scanning and Caching, which finds available APs by scanning a minimum number of channels and furthermore allows clients to perform handoffs without scanning, by caching AP information. I also describe a new architecture for the client and server side for seamless IP layer handoffs, which are caused when mobile clients change the subnet due to layer 2 handoffs. I also present two methods to improve VoIP capacity for 802.11 networks, Adaptive Priority Control (APC) and Dynamic Point Coordination Function (DPCF). APC is a new packet scheduling algorithm at the AP and improves the capacity by balancing the uplink and downlink delay of VoIP traffic, and DPCF uses a polling based protocol and minimizes the bandwidth wasted from unnecessary polling, using a dynamic polling list. Additionally, I estimated the capacity for VoIP traffic in IEEE 802.11 wireless networks via theoretical analysis, simulations, and experiments in a wireless test-bed and show how to avoid mistakes in the measurements and comparisons. Finally, to protect the QoS for existing VoIP calls while maximizing the channel utilization, I propose a novel admission control algorithm called QP-CAT (Queue size Prediction using Computation of Additional Transmission), which accurately predicts the impact of new voice calls by virtually transmitting virtual new VoIP traffic.

We propose call degradation and admission strategies based on modeling quality-of-service (QoS) degradation of multirate traffic for third generation multimedia wireless network. The real-time traffic is classified into K classes based on the bandwidth requirements, where a class i call uses i channels. To increase the carried traffic in an overloaded system, some of the ongoing calls release channels that they are using and enter a degraded mode of operation. Two orthogonal QoS parameters called carried traffic and bandwidth degradation are defined, and a cost function describing the total revenue earned by the system from a bandwidth degradation policy is formulated. This cost function model is extended to incorporate a call admission policy, and methods are shown to compute the optimal call admission and degradation policies which maximize the effective revenue earned. Detailed simulation experiments are conducted to validate our proposed model.

A set of centralized burst-level cell scheduling schemes, namely, First Come First Served with Frame Reservation (FCFS-FR), FCFR-FR+, Earliest Deadline First with Frame Reservation (EDF-FR), EDF-FR+, and Multitraffic Dynamic Reservation (MTDR), are investigated for transmission of multiservice traffic over time division multiple access (TDMA)/time division duplex (TDD) channels in wireless ATM (WATM) networks. In these schemes, the number of time slots allocated to a virtual circuit (VC) during a frame-time is changed dynamically depending on the traffic type, system traffic load, the time of arrival (TOA)/time of expiry (TOE) value of the data burst and data burst length. The performances of these schemes ate evaluated by computer simulation for realistic voice, Video and data traffic models and their quality-of-service (QoS) requirements in a wireless mobile multimedia network. Both the error-free and the correlated fading channel conditions are considered. Simulation results show that the EDF-FR+ and MTDR schemes outperform the other schemes and can provide high channel utilization with predictive QoS guarantee in a multiservice traffic environment even in the presence of bursty channel errors. The EDF-FR+ scheme is found to provide better cell multiplexing performance than the MTDR scheme. Such a scheme would be easy to implement and would also result in a power conservative TDMA/TDD medium access control (MAC) protocol for broadband wireless access. Burst-level cell scheduling schemes such as EDF-FR+ can be easily adapted as MAC protocols in the emerging differentiated services (DS) enhanced wireless Internet protocol (IP) networks.