Multiple Priority Classes Research Articles

Elastic threshold-based admission control for QoS satisfaction with reward optimization for servicing multiple priority classes in wireless networks

We analyze performance characteristics of a class of call admission control (CAC) algorithms designed for servicing multiple priority classes in wireless networks with the goal of quality of service (QoS) satisfaction and reward optimization. By reward, we mean some sort of “value” obtained by the system as a result of servicing multiple priority classes. In this paper we design and evaluate the performance of a new algorithm, elastic threshold-based CAC, in terms of the maximum reward obtainable with QoS satisfaction from servicing multiple priority classes with distinct QoS requirements, and compare it with existing partitioning, threshold, and spillover CAC algorithms. We also develop a heuristic-based search method to determine the best threshold-value sets used for multiple service classes by sequentially adjusting these thresholds based on the reward and rejection rate obtainable vs. QoS constraints of each service class. We demonstrate through test cases and simulation that elastic threshold-based CAC outperforms existing CAC algorithms for QoS satisfaction and reward optimization in solution optimality for serving multiple QoS service classes in wireless networks.

Supporting Service Differentiation and Improving Channel Utilization with an Enhanced IEEE 802.11 DCF

Fair allocation of bandwidth and maximization of channel utilization are two important issues when designing a contention-based wireless medium access control (MAC) protocol. However, fulfilling both design goals at the same time is very difficult. Considering the problem in the IEEE 802.11 wireless local area networks (WLANs), in this work we propose a method using a p-persistent enhanced DCF, called P-IEEE 802.11 DCF, to achieve weighted fairness and efficient channel utilization among multiple priority classes in a WLAN. Its key idea is that when the back-off timer of a node reaches zero, the transmission probability is properly controlled to reflect the relative weights among data traffic flows so as to maximize the aggregate throughput and to minimize the frame delay at the same time. In particular, we obtain the optimal transmission probability based on a theoretical analysis, and also provide an approximation to this probability. The derived optimal and approximation are all evaluated numerically and simulated with different scenarios. The results show that the proposed method can fulfill our design goals under different numbers of priority classes and different numbers of nodes.

Guard-Channel-Based Incremental and Dynamic Optimization on Call Admission Control for Next-Generation QoS-Aware Heterogeneous Systems

Next-generation communication systems are expected to be highly integrated heterogeneous networking environments. Supporting multimedia services with different quality-of-service (QoS) requirements over such highly heterogeneous environments is a very challenging task, and a unified call admission control (CAC) optimization mechanism is needed to allow resources to be efficiently utilized. In this paper, we propose an optimal CAC mechanism, i.e., the guard-channel-based incremental and dynamic optimization (GUIDO), which is a threshold-based CAC scheme that is designed based on the Markov decision process (MDP) and sensitivity analysis (SA) techniques. The MDP is used to derive the optimal CAC policy for predetermined goals, whereas the use of SA can greatly reduce the effort of unnecessary recomputation of the CAC policy when the traffic condition varies. Through the use of system capacity estimation and QoS mapping techniques, GUIDO allows the CAC operation to be performed in a general framework, even with various underlying communication systems and different access/core networks. GUIDO can be implemented dynamically (online optimization) and statically (lookup table). Homogeneous and heterogeneous systems with multiple service priority classes are studied in this paper. We have considered comprehensive objective functions, and each characterizes a different interest of the service provider. The performance is evaluated via an event-driven simulator, and the results are compared with those of the complete sharing scheme and conventional guard channel schemes under constant call-arrival rates as well as time-varying call-arrival-rate traffic scenarios.

Congestion control, differentiated services, and efficient capacity management through a novel pricing strategy

Pricing is an effective tool to control congestion and achieve Quality of Service (QoS) provisioning for multiple differentiated levels of service. In this paper, we propose a practical, flexible and computationally simple pricing strategy that can achieve QoS provisioning in Differentiated Services networks with multiple priority classes operating in an efficient economic market, while also maintaining stable transmission rates from end-users. In contrast to previous work, in which dynamic pricing strategies are based on the state of congestion alone, our strategy adds a separate price component for the preferential service received by a packet. This permits an efficient market for network resources and services, with the price charged being dependent upon both the cost of the resources and the dynamically changing demand for it. In addition, this automatically enforces efficient capacity management in the allocation of resources among the various service classes, leading to a user-centric approach where a user is not charged a higher price unless preferential service is actually delivered. Our analytical and simulation results demonstrate that, with the combination of user adaptation and our pricing strategy, differentiated services can be achieved with stable transmission rates. This paper concludes with a discussion of various operational issues associated with actual deployment of such a pricing strategy.

Shared concentration output queuing switch for multiple priority classes

AbstractIn B‐ISDN, it is important to handle a variety of traffic having different loss probability requirements by using the same network. Since the shared concentration output queuing (SCOQ) switch has shared transmission networks, focus has been on its switch. In multimedia communications, the QoS (quality of service) is required and satisfied. Moreover, it is important to satisfy the requirement for cell loss probability. The switch has the advantage that the number of switching elements is small. However, it is not enough to correspond to priority classes. In this paper, we propose the SCOQ switch model for multiple priority classes, which is structured with a batcher network and independent banyan networks for each class and output buffers. We evaluate the cell loss probability and mean waiting time by computer simulations and analysis. The cell loss probability of the high‐priority class can be reduced since more high‐priority cells have priority to be transmitted to output buffers than low‐priority cells. As a result, we show that the proposed model is useful in satisfying different requirements of the cell loss probability for multiple priority classes. © 2001 Scripta Technica, Electron Comm Jpn Pt 1, 85(2): 41–50, 2002

Performance analysis of knockout ATM switch with batcher network for multiple priority classes

AbstractRecently, there has been a need for a network architecture with a variety of traffic. In order to meet the requirements, a conventional knockout switch for two priority classes has been proposed and evaluated by numerical calculations. However, the switch is analyzed for multiple priority classes even though there are many kinds of traffic in the network. In this paper, a knockout packet switch with a batcher network for multiple classes is proposed in order to satisfy different requirements for loss probability of packets with multiple classes. The proposed model involves sorting packets according to the small identification number of a priority class by a batcher network. Hence, it is possible to handle packets with multiple classes. The proposed switch consists of N modules structured with filters, batcher network, and output buffers. As a result, we show that the proposed model is useful in satisfying different requirements for packet loss probability with multiple classes. © 2001 Scripta Technica, Electron Comm Jpn Pt 2, 84(7): 10–18, 2001

Workload bounds in fluid models with priorities

In this paper we establish upper and lower bounds on the steady-state per-class workload distributions in a single-server queue with multiple priority classes. Motivated by communication network applications, the model has constant processing rate and general input processes with stationary increments. The bounds involve corresponding quantities in related models with the first-come first-served discipline. We apply the bounds to support a new notion of effective bandwidths for multi-class systems with priorities. We also apply the lower bound to obtain sufficient conditions for the workload distributions to have heavy tails.

Knockout packet switch with batcher network for two priority classes

Various types of ATM switches have been widely studied and developed in B-ISDN. However, the conventional knockout packet switch cannot handle the multiple priority classes. We consider two class packets of class 1 and class 2. Class 1 packets have priority for packet loss probability. A knockout packet switch with batcher network for two class packets is proposed in order to improve the packet loss probability of priority packets. The proposed switch consists of N modules structured with filters, a batcher network, and output buffers. We evaluate the packet loss probability of each class by computer simulations and numerical calculations. We obtain the total mean waiting time at output buffers by numerical calculations. In addition, we show the mean waiting time at output buffers by computer simulations. It is found that our proposed switch is able to satisfy the requirements of packet loss probability for the two classes under uniform traffic. © 2000 Scripta Technica, Electron Comm Jpn Pt 1, 83(12): 49–57, 2000

Performance analysis of replicated self‐routing switch model with multiple priority classes

Performance analysis of replicated self‐routing switch model with multiple priority classes

Performance analysis of replicated self-routing switch model with multiple priority classes

Performance analysis of replicated self-routing switch model with multiple priority classes

Optimal admission control of markov-modulated batch arrivals to a finite-capacity buffer

We consider packet acceptance policies for digitized voice packet transmission in high-speed networks in an ATM setting. The constant length packets, called cells, arrive in batches at an intermediate node. The arrival process is modulated by a random environment, typically arising from the multiplexing of on-off sources. The cells belong to multiple priority classes. The buffer access controller, at times 0,1,2,…, admits some of the cells from the intermediate buffer into the main buffer, discarding the rest. The transmission channel removes one cell per unit time. Dropping a cell causes distortion: the higher the priority of the dropped cell the higher the distortion. We use the methods of Markov Decision Processes to obtain an optimal cell discarding policy that minimizes distortion. We study structural monotonicity properties of the optimal policies and illustrate them with an example. Finally, the implementation issues are discussed

Securityholder Taxes, Corporate Capital Structures and the Priority Structure of Debt

AbstractThis paper shows that the firm has an incentive to issue multiple classes of debt that are differentiated by seniority to enhance securityholder tax‐timing option values. The analysis establishes that there is at least one mix of senior and junior debt that maximizes the tax option gain from having multiple priority classes of debt. An analytic example provides specifications for the optimal amount of leverage and the optimal mix of senior and junior debt. Relative to the case of only one class of debt, a multiple debt priority structure increases the optimal amount of corporate leverage.

Measurement-based performance evaluation of an ATM switch with external multicasting engine and multiple-priority classes

This paper uses measurement-based traffic models to evaluate a shared-memory ATM switch with 32/spl times/32 155 Mbit/s ports and an external multicasting engine; this is the design of Cisco System's next-generation ATM switch, the LightStream-1010 (LS-1010). Assuming that the multicast traffic can take approximately 30% of the total switch load, we find that an external multicasting engine requires a 32 (8) cell buffer at a replication rate of 16 (64) cells per cell service time. We discover that in a multimedia environment, the shared-memory architecture requires 10-30 times less total memory than the bus architecture; a 64 K cell buffer is sufficient to handle 90% utilization with the nonuniform traffic that we investigated. Multiple-priority classes are considered.

Input queueing multicast ATM packet switch with two priority classes using a priority scheme with a window policy

To achieve a high performance multicast switch with multiple priority classes, we have proposed a new N × N input queuing technique which uses a novel priority scheme and a high-performance arbitration algorithm. The scheme uses a priority without iteration (POI) method and a pipeline arbitration. Simulation results show that this scheme improves the performance of delay critical services and it can give almost the same performance as that which uses a priority with iteration (PWI) method.

Performance analysis of input and output queueing packet switch with multiple priority classes

AbstractThis paper proposes an N X N input‐output buffered switch model which switches several kinds of packets emphasizing the real‐time property as well as packets emphasizing the secure transmission. The model corresponds to the Poisson and Bernoulli traffic switching system. Such performances as the average system queueing delay and the loss probability for the packet emphasizing the real‐time transmission are analyzed. Nonpreemptive priority discipline is applied on the input side where the circuit configuration is relatively simple. On the output side, the first‐come/first‐served (FCFS) process is applied without considering the priority service.In the proposed model, the output buffer size is assumed as finite and the input buffer size is assumed as infinite. For the two kinds of switching systems which serve the Poisson arrival packets and the Bernoulli arrival packets, respectively, the mean system queueing delay for the priority class is analyzed. For the case where the input buffer size is limited for the packet with a high priority emphasizing the real‐time transmission, the relation between the loss probability for the packet with a high priority and the sizes of the input and output buffers is investigated by a computer simulation for the case of two classes. The adequate input buffer size for the packet with a high priority is determined.

Fair DQDB: The Rotating Slot Generator Scheme

We introduce the Rotating Slot Generator (RSG) scheme for dual bus architectures, a medium access control protocol appropriate for high capacity Metropolitan Area Networks (MANs). This scheme uses the looped bus architecture of the Distributed Queue Dual Bus (DQDB) MAN, in which slot generator hardware is incorporated into all stations. Its difference from DQDB is that during its operation the responsibility for generating slots moves periodically from station to station around the loop. Thus, station positions relative to the slot generator change continuously and, therefore, there are no favorable locations on the busses. We first present the system architecture and the RSG protocol. Then, we carry out a thorough investigation of the performance of the RSG scheme through simulation. We demonstrate the fairness of the protocol with respect to throughput and delay, and evaluate its performance in underload and overload conditions, under both a single and multiple priority classes of traffic. We also compare its performance with other variations of DQDB.

An M/G/1 queueing system with multiple priority classes

We consider anM/G/1 queueing system with multiple priority classes of jobs. Considered preemptive rules are the preemptiveresume, preemptive-repeat-identical, and preemptive-repeat-different policies. These three preemptive rules will be analyzed in parallel. The key idea of analysis is based on the consideration of a busy period as a composite of delay cycle. As results, we present the exact Laplace-Stieltjes (L.S.) transforms of residence time and completion time in the system.

Adaptive bandwidth waste rate: a fair bandwidth sharing scheme for the DQ protocol with multiple priority classes

In distributed queue dual bus (DQDB) networks, the distributed queueing (DQ) protocol is used to control access of asynchronous data to the bus. This paper proposes a new scheme, the adaptive bandwidth waste rate (ABWR) scheme, for fair bandwidth sharing among active nodes under the DQ protocol with multiple priority classes. With ABWR, each node adjusts the bandwidth waste rate for priority level j dynamically, depending upon the bus-wide bandwidth demand of a priority higher than j. We calculate the system capacity under the DQ protocol with ABWR. Four types of implementation are suggested, and their performance is evaluated by simulation. With the proposed scheme, fair bandwidth sharing among active nodes is accomplished, wasting only a small portion of the bus bandwidth.

Performance analysis of broadcast star network with priorities

The authors present a model for the broadcast star network with collision avoidance switch and with multiple priority classes of messages. They also propose a service discipline which is easy to implement and exhibits relatively low variance of message delay. This service discipline, which is used to select a message among messages with the same class-index, is a combination of first-come first-served (FCFS) and random-order of service (ROS) disciplines, and it uses the priority fields in the message header. Then, the ready stations can be considered to form a distributed queue, and the entire system can be considered to form a priority M/G/1 queueing system with multiple server vacations. They analyze the model to obtain the distributions of the message delay for the proposed service discipline, and compare the results with that for the FCFS discipline. From numerical results, they show that the variance of the message delay for the proposed service discipline is almost the same as that for the FCFS discipline for any distribution of message length and also for any value of normalized propagation delay.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The no slot wasting bandwidth balancing mechanism for dual bus architectures

A bandwidth balancing (BWB) mechanism has been added to the distributed queueing algorithm of the distributed-queue dual bus (DQDB) network. BWB can provide the requested throughputs by lightly loaded stations and evenly distribute the remaining channel bandwidth among overloaded stations. However, its operation requires the wastage of channel slots. The authors introduce a new bandwidth balancing mechanism for DQDB. The operation of the new mechanism requires one additional bit in the access control field (ACF) of the slot but has the advantage of exhibiting a similar behavior with the current BWB mechanism of DQDB without wasting any channel slots. For this reason, it can converge faster to the steady state in which fair bandwidth allocation is achieved. The authors investigate the throughput and delay performance of the proposed mechanism under one traffic class and examine its capacity to support multiple priority classes of traffic. They also compare its performance with the corresponding performance of the BWB mechanism of DQDB.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>