Preemptive Priority Research Articles

Supporting multimedia streaming and best‐effort data transmission over IEEE 802.11e EDCA

AbstractAs demand for broadband multimedia wireless services increases, improving quality of service (QoS) of the widely deployed IEEE 802.11 wireless LAN (WLAN) has become crucial. To support the QoS required by a wide range of applications, the IEEE 802.11 working group has defined a new standard: IEEE 802.11e. In this paper, we propose a measurement‐based dynamic media time allocation (MBDMTA) scheme combined with a concatenating window scheme to support real‐time variable bit rate (rt‐VBR) video and best‐effort (BE) data transmission using IEEE 802.11e enhanced distributed channel access (EDCA). To provide the QoS guarantee for rt‐VBR video, the proposed MBDMTA scheme dynamically assigns channel time to the rt‐VBR video based on the estimate of the required network resources. On the other hand, the concatenating window scheme controls the contention window (CW) ranges of different priority flows such that real‐time services always have higher channel access probability, thus achieving the capability of preemptive priorities. In addition, the concatenating window scheme preserves fairness among flows of the same class and attains high channel utilization under different network conditions. Simulation results demonstrate that the throughput and delay performance improve significantly for the transmission of rt‐VBR video and BE traffic as compared to those for the 802.11e EDCA specification. It is also revealed that combining the two proposed schemes provides seamless integration and reliable transmission of digital video and data service within the 802.11e EDCA framework. Copyright © 2007 John Wiley & Sons, Ltd.

A fuzzy goal programming approach with priority for channel allocation problem in steel industry

A model is presented to address a steel supplier's channel allocation problem that includes decisions of channel mix and capacity allocation for each distribution channel. The problem has been formulated as a fuzzy mixed integer multiple goal programming problem that includes business competitive advantages such as maximizing net profits, minimizing the rate of end user claims, and minimizing the rate of late lading, and is subject to constraints regarding manufacturing capacity, customer's demand, channel capacity, channel quota flexibility, budget limitations, and so on. Realistic data from Taiwan's largest steel company is implemented for the effectiveness of the model. The proposed model can also be applied to the allocation problem in other industries with preemptive priority and desired achievement level in a fuzzy environment.

Performance Evaluation of CAC Schemes for Multi-service Traffic Environment in 3G Networks

The ever-growing mobile market and the number of services offered by the network providers, which are increasing with every passing day, has reinforced the need for optimized CAC schemes. The introduction of Code Division Multiple Access (CDMA) has resulted in extensive reuse of frequency and therefore the birth of microcells has increased the number of handovers especially in metropolitan cities. Consequently further stress is exerted on existing CAC schemes to maintain the Quality of Service (QoS). In this paper we present new CAC algorithms based on dynamic allocation of channels to multiple input traffic streams. In this context two CAC schemes are proposed; IPG (Independent DT Queue priority, Pre-emptable DS priority, Guard Channel priority) and ITPG (Independent DT Queue priority, Timeout handover DS queuing Priority, Pre-emptable DS priority, Guard Channel priority). This scheme provides differentiated admission to various delay sensitive (DS) and delay tolerant (DT) traffic streams for both handover request (HOR) and new call request (NCR) according to current load intensity. The scheme provides an effective pre-emption priority in order to decreases forced handover failure probability. Service nature and customer behavior was considered to lay down the different levels of priorities that were assigned at different stages of the CAC scheme in order to achieve optimal QoS for urban area (metropolitan) cell. The simulation results demonstrate the improved QoS under various traffic scenarios.

Two-class priority queueing system with restricted number of priority customers

In this paper, we analyze a two-class single-server preemptive priority queueing system with arrivals to each class are assumed to follow a Poisson process with exponentially distributed service times. Customers are served on a first-come, first-served basis within their own queue. Explicit expressions for the mean queue length and the steady-state joint distribution of the number of high and low priority customers in the system are derived. The analysis is based on the generating function technique. The obtained expressions are free from Bessel functions or any integral functions. Moreover, numerical values testing the quality of our analytical results are also presented.

An adaptive bandwidth allocation scheme with preemptive priority for integrated voice/data mobile networks

This paper presents an adaptive bandwidth allocation scheme, called complete sharing with preemptive priority (CSPP) scheme, for integrated voice/data mobile networks. It uses the complete sharing approach to maximize the bandwidth utilization efficiency by allowing data traffic to share all the bandwidth resource of a cell and introduces a preemptive priority mechanism to maintain the high performance of voice traffic while the injury of data traffic is compensated through a victim buffer. A degradation/compensation mechanism is applied to the data traffic which has elastic characteristics. The model of the CSPP scheme is analyzed by a two dimensional Markov process. The steady state probability vector is obtained recursively by the matrix-analytic method and many important performance measures are then determined such as different types of probabilities, total channel utilization, transmission delay, busy period time and blocking period time. From the performance analysis and comparison as well as the numerical results, we can conclude that the CSPP scheme can achieve complete service differentiation for different traffic classes and very high and stable channel utilization under various traffic loads. By adjusting the defined constraint factors, we can not only maintain higher priority for handoff voice over new voice calls and voice calls over data calls but also provide necessary protection for data calls in hot-spot data traffic situations

An adaptive bandwidth allocation scheme with preemptive priority for integrated voice/data mobile networks

This paper presents an adaptive bandwidth allocation scheme, called complete sharing with preemptive priority (CSPP) scheme, for integrated voice/data mobile networks. It uses the complete sharing approach to maximize the bandwidth utilization efficiency by allowing data traffic to share all the bandwidth resource of a cell and introduces a preemptive priority mechanism to maintain the high performance of voice traffic while the injury of data traffic is compensated through a victim buffer. A degradation/compensation mechanism is applied to the data traffic which has elastic characteristics. The model of the CSPP scheme is analyzed by a two dimensional Markov process. The steady state probability vector is obtained recursively by the matrix-analytic method and many important performance measures are then determined such as different types of probabilities, total channel utilization, transmission delay, busy period time and blocking period time. From the performance analysis and comparison as well as the numerical results, we can conclude that the CSPP scheme can achieve complete service differentiation for different traffic classes and very high and stable channel utilization under various traffic loads. By adjusting the defined constraint factors, we can not only maintain higher priority for handoff voice over new voice calls and voice calls over data calls but also provide necessary protection for data calls in hot-spot data traffic situations

Randomized pushing-out in the priority queueing with a finite buffer size

Consider the nonpreemptive priority queueing system with two classes of packets. Class-1 packets have priority over class-2 packets. The packets of class 1 (2) arrive into the buffer according to the Poisson process with rate λ1 (λ2), respectively. The service time has the exponential distribution with the same rate μ for each class. The service times are independent of the arrival processes. The buffer has a finite size N and it is shared by both types of customers. If the buffer is full, a new incoming customer of class 1 can push out of the buffer a customer of class 2 with probability α. Note that if α = 1, we retrieve the standard nonrandomized push-out mechanism. The infinite buffer priority queueing has been thoroughly studied in [4, 7, 8]. The case of finite buffer priority queueing has received considerably less attention. The M | M | C | K type finite-buffer nonpreemptive priority queueing with nonrandomized push-out mechanism is analyzed in [5, 6]. Bondi, in [1], considers the M | M | 1 | K type preemptive and nonpreemptive priority queueing with the following buffer management schemes: complete partitioning, complete sharing, and sharing with minimum allocation. Wagner and Krieger, in [9], analyze the M | M | 1 | K type nonpreemptive priority queueing with complete sharing buffer management scheme and with class-dependent service rates. In [2], Cheng and Akyildiz consider the priority queueing with general service-time distributions and a general service discipline function. Most of the above works use recursive relations to solve steady-state Kolmogorov equations. We use a generating function approach, which only requires the solution of a linear system ofN equations. As far as we know, the randomized push-out mechanism is analyzed for the first time.

Optimal threshold policies in a two-class preemptive priority queue with admission and termination control

We consider a two-class $$M^{\lambda_1, \lambda_2}|M^{\mu}|1$$ 1 preemptive priority queue in which there are two essential, on-line decisions that have to be taken. The first is the decision to either accept or reject new type-1 or type-2 jobs. The second is the decision to abort jobs, i.e., to remove any type-1 or type-2 jobs from the system. We show that there exist optimal threshold policies for these two types of, decisions.

Waiting time analysis of the multiple priority dual queue with a preemptive priority service discipline

The dual queue consists of two queues, called the primary queue and the secondary queue. There is a single server in the primary queue but the secondary queue has no service facility and only serves as a holding queue for the overloaded primary queue. The dual queue has the additional feature of a priority scheme to help reduce congestion. Two classes of customers, class 1 and 2, arrive to the dual queue as two independent Poisson processes and the single server in the primary queue dispenses an exponentially distributed service time at the rate which is dependent on the customer’s class. The service discipline is preemptive priority with priority given to class 1 over class 2 customers. In this paper, we use matrix-analytic method to construct the infinitesimal generator of the system and also to provide a detailed analysis of the expected waiting time of each class of customers in both queues.

An evaluation approach to engineering design in QFD processes using fuzzy goal programming models

Quality function deployment (QFD) is a product development process used to achieve higher customer satisfaction: the engineering characteristics affecting the product performance are designed to match the customer requirements. From the viewpoint of QFDs designers, product design processes are performed in uncertain environments, and usually more than one goal must be taken into account. Therefore, when dealing with the fuzzy nature in QFD processes, fuzzy approaches are applied to formulate the relationships between customer requirements (CRs) and engineering design requirements (DRs), and among DRs. In addition to customer satisfaction, the cost and technical difficulty of DRs are also considered as the other two goals, and are evaluated in linguistic terms. Fuzzy goal programming models are proposed to determine the fulfillment levels of the DRs. Differing from existing fuzzy goal programming models, the coefficients in the proposed model are also fuzzy in order to expose the fuzziness of the linguistic information. Our model also considers business competition by specifying the minimum fulfillment levels of DRs and the preemptive priorities between goals. The proposed approach can attain the maximal sum of satisfaction degrees of all goals under each confidence degree. A numerical example is used to illustrate the applicability of the approach.

Performance analysis of a channel allocation scheme for multi‐service mobile cellular networks

AbstractThis paper presents a new channel allocation scheme, namely the dynamic partition with pre‐emptive priority (DPPP) scheme, for multi‐service mobile cellular networks. The system is modelled by a two‐dimensional Markov process and analysed by the matrix‐analytic method. A pre‐emptive priority (PP) mechanism is employed to guarantee the quality of service (QoS) requirement of the real‐time (RT) traffic at the expense of some degradation of non‐real‐time (NRT) traffic, while the victim buffer compensates the degradation and has no negative impact on the RT traffic. The complete service differentiation between new calls and handoff calls from different traffic classes is achieved by using the dynamic partition (DP) concept with the help of related design parameters. The performance analysis and numerical results show that the DPPP scheme, compared with the existing schemes, is effective and practical in multi‐service environments. Copyright © 2006 John Wiley & Sons, Ltd.

A flexible contention resolution scheme for QoS provisioning in optical burst switching networks

Contention resolution is a major issue in bufferless optical burst switching (OBS) networks. The existing contention resolution schemes consider priority and arrival time to resolve contention. For most multimedia applications priority and delay are key parameters for QoS provisioning. In this paper, we propose a new signaling protocol for reducing contention in OBS networks and consider three parameters, namely, priority of the burst, number of hops traversed, and burst size into account to resolve contention. The source node in the proposed protocol can be informed of the contention up to halfway along the path of the burst, and thus, can reschedule the burst accordingly. The scheme is adaptable to both prioritized and delay constrained traffic. We call the scheme OBS- Flex. For selecting a data channel, we propose three channel selection algorithms, namely, Least Recently Used (LRU), First Fit (FF), and Priority Set (PS). We simulate OBS- Flex and compare with preemptive priority just-enough-time (PPJET) contention resolution scheme. We show that OBS- Flex outperforms PPJET in terms of burst loss rates. For simulation, we have considered Poisson and bursty traffic models.

Hardware-Based Precise Time Synchronization on Gb/s Ethernet Enhanced with Preemptive Priority

SUMMARY Time synchronization is indispensable for wide area distributed systems including sensor networks, automation systems, and measurement/control systems. Another application is clock distribution, which is indispensable to support continuous information transfer. Because of the increasing demand for more sophisticated applications, it is essential to establish a time synchronization technique that offers higher accuracy and reliability. Particularly, the accuracy of time synchronization for Ethernet must be enhanced since Ethernet is becoming more important in telecommunication networks. This paper investigates a precise time synchronization technique that supports Gb/s Ethernet. To obtain accurate time synchronization, delay variation in message transfer and processing must be minimized. For this purpose, the paper first describes the implementation of preemptive priority queuing, which decreases the message delay variation of Ethernet. Through experiments, it is shown that preemptive priority queuing effectively achieves very low delay variation. The paper then proposes a method to synchronize the time signal of a slave node to that of the master node. The proposed time synchronization method is performed in the lower protocol layer and implemented on FPGA-based hardware. The method achieves superior time accuracy through the low message transfer/processing delay variation provided by preemptive priority, lower layer execution, and hardware implementation. The effectiveness of the method is confirmed through experiments. The experiments show that the time variation achieved by the method is smaller than 0.1 µsec. This perfor

ENHANCED INTERACTIVE SATISFYING OPTIMIZATION APPROACH TO MULTIPLE OBJECTIVE OPTIMIZATION WITH PREEMPTIVE PRIORITIES

This paper proposes an enhanced interactive satisfying optimization method based on goal programming for the multiple objective optimization problem with preemptive priorities. Based on the previous method, the approach presented makes the higher priority achieve the higher satisfying degree. For three fuzzy relations of the objective functions, the corresponding optimization models are proposed. Not only can satisfying results for all the objectives be acquired, but the preemptive priority requirement can also be simultaneously actualized. The balance between optimization and priorities is realized. We demonstrate the power of this proposed method by illustrative examples.

Analysis of an optical hybrid switch

This paper provides new loss models for an OCS/OBS optical hybrid switch. Exact results for the blocking probability based on an analysis, of a 3-dimension state-space Markov chain is derived when circuits are given preemptive priority over bursts and are allowed to wait a certain amount of time if all wavelengths are busy in the desired output link. Because it is difficult to-exactly compute the blocking probability in realistic scenarios, we derive a. computationally scalable approximation for the blocking probability reducing the 3-dimension state space into a single dimension

Preemptive Short Packets Priority Scheduling for Asynchronous Optical Packet Switching

The average queue delay of optical packet increases when the packets block in the virtual output queue header in the asynchronous optical packet switching. We analyze the character of variable length Internet packet and propose the preemptive short packets priority (PSPP) algorithm for reducing the total packet queue time in the queue. In the PSPP algorithm, the short packet can preempt the transmission time of the long packet and can be served first. The analysis and the simulation showed the PSPP algorithm can make the average queue time of the short packet decrease to zero almost and can decrease the total packet average queue time largely when the traffic load was middle and low. The PSPP could guarantee the low average queue delay for the real -time TCP traffic.

Performance evaluation of an optical hybrid switch with circuit queued reservations and circuit priority preemption

We provide here a new loss model for an optical hybrid switch that can function as an optical burst switch and/or optical circuit switch. Our model is general as it considers an implementation whereby some of the circuits have preemptive priority over bursts and others are allowed to queue their reservations. We first present an analysis based on a 3-dimension state-space Markov chain that provides exact results for the blocking probabilities of bursts and circuits, the proportion of circuits that are delayed and the mean delay of the circuits that are delayed. Because it is difficult to exactly compute the blocking probability in realistic scenarios with a large number of wavelengths, we derive computationally a scalable and accurate approximations based on reducing the 3-dimension state space into a single dimension. These scalable approximations that can produce performance results in a fraction of a second can readily enable switch dimensioning. Extensive numerical results are presented to demonstrate the accuracy and the use of the new approximations.

Resource management and QoS control in multiple traffic wireless and mobile Internet systems

AbstractEnd‐to‐end quality of service (QoS) control for multiple traffic in wired networks is carried out through Differentiated services (DiffServ). Edge routers in DiffServ domain classify incoming flows into different per‐hop behavior (PHB) groups and give a policy‐based QoS guarantee to these behavior aggregates. As Internet extends into the wireless and mobile section, different traffic flows should be treated differently not only in wired core network, but also in wireless resource allocations. In this paper, we propose a preemptive priority handoff and adaptive resource allocation scheme. DiffServ PHB groups are mapped into different wireless and mobile QoS classes. Traffic flows are categorized into these classes in order to allow the system to allocate different bandwidth and make resource reservation according to their priorities. Higher priority traffic flows are permitted to preempt lower priority flows in service. Lower ones, on the contrary, can expand their bandwidth into areas reserved for higher priority traffic flows for better resource utilization. We use both analytical model and simulation to evaluate the system performance in terms of blocking probabilities, forced termination probabilities, and delay. The forced termination probability of high priority traffic flows can be decreased significantly by introducing the preemptive priority scheme. Therefore, this scheme can be used in wireless part of the system along with DiffServ to give further guarantee for low delay, low jitter, and low loss services to high priority services. Copyright © 2005 John Wiley & Sons, Ltd.

Scalable performance evaluation of a hybrid optical switch

This paper provides new loss models for a hybrid optical switch (HOS) combining optical circuit switching (OCS) and optical burst switching (OBS). Exact blocking probabilities are computed when 1) no priority is given to either circuits or bursts and 2) circuits are given preemptive priority over bursts. Because it is difficult to exactly compute in realistic scenarios, computationally scalable approximations are derived for the blocking probability. The sensitivity of the analytical results to burst length and circuit holding-time distributions is quantified by simulation. It is demonstrated how the proposed approximations can be used for multiplexing-gain evaluation of a hybrid switch. In addition, the extension of the proposed single-node model to a network model composed of OCS, OBS, and hybrid switches is outlined.

An MCDM model for media selection in the dual consumer/industrial market

An optimal advertising media selection is a strategic factor for the operations of both traditional and e-business environments. This paper presents a case study that considers two options: industrial and consumer products. In order to resolve the strategic decision-making about dual market high technology products, a mixed integer goal programming model is developed to facilitate the advertising media selection process. Preemptive priority ordering is established by the analytic hierarchy process. The problem is solved lexicographically using a software package, based on the data obtained from the e-business industry in Korea. The satisfying solution is identified and analyzed, and sensitivity analyses are performed for model flexibility.