A novel two-phase access priority scheme in wireless communication systems

An efficient uplink access priority scheme is of great importance for supporting a large number of mobile users with various levels of quality of service (QoS). The authors propose a novel two-phase access priority scheme, and show through mathematical analysis and computer simulation that the proposed scheme can differentiate the success probability of each class adaptively, and can also support many priorities effectively.     

Throughput analysis of the IEEE 802.4 priority scheme

The IEEE 802.4 token bus standard defines an optional priority scheme to handle multiple classes of data. It allocates the channel bandwidth among different priority classes of messages by a set of timers at each station. An analytical model for the priority scheme is presented. The model relates the throughput of each priority class of messages to the traffic intensities of different classes, the target rotation times, and the high-priority token holding time. The network is assumed to be symmetric with respect to its parameters and the traffic distribution among nodes. Simulation results are used to evaluate the accuracy of the model. The model provides means of evaluating the network throughput and can be used to determine the time values to meet the throughput requirements of different classes of traffic     

Approximate availability analysis of VAXcluster systems

The availability of an n-processor VAX cluster system is determined using a hierarchical approach that allows: (1) a closed-form answer to an apparently difficult problem to be obtained, and (2) the determination of the optimal number of processors in the cluster for a given set of cluster parameters. The approach is a two-level hierarchical model in which the lower-level model is a nine-state Markov chain that is solved in a closed form. The nine-state Markov chain is then aggregated into a three-state device analogous to a diode. Subsequently, the system availability is computed by analyzing a simple network     

Queueing analysis of a threshold based priority scheme for ATMnetworks

A threshold-based priority scheme in which a tuning parameter is used to provide adequate quality of service to real-time traffic while providing the best possible service to the non-real-time traffic is proposed. The priority scheme is a generalization of the static priority scheme and the one-limited scheme and is more flexible than both. For this scheme, the authors carry out a queueing analysis and obtain the joint distribution of the queue-lengths. They show by numerical examples how the parameter of this scheme can be tuned dynamically, so that the tuning function can be integrated with the call admission policy     

Random polling scheme with priority

A random polling scheme which has an inherent priority structure is proposed. The priority structure is implemented by appropriate choice of the polling table. Numerical results for the case of no load show that the priority scheme is effective and the mean no-load token cycle time can be tailored to the priority of the station.<>     

Approximate analysis of n-unit cold-standby systems

In this paper, a n-unit cold-standby system with a single repair facility is analysed using two approximate methods namely, cutting and clustering the state space. It has been assumed that the failure rate is constant and the repair time is arbitrarily distributed. A mathematical model is developed using semi-regenerative phenomena and systems of convolution integral equations satisfied by various state probabilities corresponding to different initial conditions are obtained. Explicit expressions for the expected number of failures and expected number of repair completions in an interval [0, t] are obtained. An iterative numerical method is used to solve the systems of integral equations obtained and a comparative study has been carried out between exact and approximate solutions.     

Approximate analysis of asymmetric single-service prioritized tokenpassing systems

A LAN or MAN (local or metropolitan area network) using token passing to allow stations to access the transmission medium is studied. Ibe and Cheng (1989) recently presented an approximate derivation of message delays for an asymmetric single-service token passing with only one type of message. In the present work, this analysis is extended to an operation with nonpreemptive priority queuing. The number of message priority levels and the walktime vary from one station to another. Moreover, the assumed Poisson message arrival process and the message transmission time vary, not only from one station to another, but also from one class to another. The performance, as measured by the mean delay for any message class at any station, is derived. The simulation results show excellent agreement with the analytical results, even under heavy loading. The results confirm earlier findings that the performance at a station is influenced by its position relative to heavily loaded stations     

A priority TCAM IP-routing lookup scheme

A priority TCAM IP-routing lookup scheme, which combines a priority ternary content addressable memory (TCAM) technique with a compact IP-routing lookup scheme, is proposed in this paper. It not only completes an IP-routing lookup with two memory accesses but also achieves small lookup table size and fast table reconstruction time.     

Analysis of a static pricing scheme for priority services

We analyze a static pricing scheme for priority services. Users are free to choose the priority of their traffic but are charged accordingly. Using a game theoretic framework, we study the case where users choose priorities to maximize their net benefit. For the single link case, we show that there always exists an equilibrium for the corresponding game; however, the equilibrium is not necessarily unique. Furthermore, we show that packet loss in equilibrium can be expressed as a function of the prices associated with the different priority classes. We provide a numerical case study to illustrate our results.     

OBS网络中QoS优先级保证方案研究

文章把信道分组和PPJET(Preemptive Prioritized Just Enough Time)协议以及光纤延时线三者结合使用,提出了一种新的QoS调度方案D-PPJET(Developed-PPJET)协议.在该协议下,高优先级数据包可以被动态地调度到任何可用的信道上去,而低优先级数据包只能在规定的部分信道上调度,并利用光纤延时线(FDL)缓存机制为未成功调度的突发包提供二次调度的机会,这样高优先级业务包调度成功的机会就大大增加,为高优先级业务提供了保证,同时还使得低优先级突发分组丢失率下降.结果表明它能够大大地改善整个网络突发包的丢失率、信道吞吐量及信道利用率.     

Adaptive delay threshold-based priority queuing scheme with opportunistic packet scheduling for integrated service in mobile broadband wireless access systems

In this letter, we propose a novel method of implementing an opportunistic priority queuing scheme that supports both latency-sensitive real-time (RT) and best-effort non-realtime (NRT) service classes in mobile broadband wireless (MBWA) systems. It employs an adaptive delay threshold as a dynamic reference of prioritizing the urgent RT service users over others, which allows for fully leveraging the multiuser diversity gain of NRT service users under the varying system conditions. It is shown that the overall system capacity can be further increased by the proposed adaptation rule, as compared with the existing opportunistic priority queuing scheme with the fixed delay threshold.     

Performance analysis of a preemptive and priority reservation handoff scheme for integrated service-based wireless mobile networks

We propose an analytical model for integrated real-time and non-real-time services in a wireless mobile network with priority reservation and preemptive priority handoff schemes. We categorize the service calls into four different types, namely, real-time and non-real-time service originating calls, and real-time and non real-time handoff service request calls. Accordingly, the channels in each cell are divided into three parts: one is for real-time service calls only, the second is for non-real-time service calls only, and the last one is for overflow of handoff requests that cannot be served in the first two parts. In the third group, several channels are reserved exclusively for real-time service handoffs so that higher priority can be given to them. In addition, a realtime service handoff request has the right to preempt non-real-time service in the preemptive priority handoff scheme if no free channels are available, while the interrupted non-real-time service call returns to its handoff request queue. The system is modeled using a multidimensional Markov chain and a numerical analysis is presented to estimate blocking probabilities of originating calls, forced termination probability, and average transmission delay. This scheme is also simulated under different call holding time and cell dwell time distributions. It is observed that the simulation results closely match the analytical model. Our scheme significantly reduces the forced termination probability of real-time service calls. The probability of packet loss of non-real-time transmission is shown to be negligibly small, as a non-real-time service handoff request in waiting can be transferred from the queue of the current base station to another one.     

Approximate analysis of narrow-band interference rejectiontechnique in CDMA spread spectrum systems using nonlinear predictionfilters

The performance of code-division multiple access (CDMA) spread spectrum systems using nonlinear prediction filters in the presence of narrow-band interference is approximately analyzed. Closed-form approximate analytical expressions for the performance improvement are derived. Also, the closed-form approximate analytical results are compared with simulated results by numerical examples. The comparison results show that the analytical results are valid when the interference bandwidth is small     

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     

Delay analyses of token-passing protocols with limited tokenholding times

The primary concern of this paper is delay analysis of IEEE 802.4 token-bus, IEEE 802.5 token-ring, and Fiber Distributed Data Interface (FDDI) when all the network traffic is of the highest priority class. We model them in an unified manner as a cyclic-service system with exhaustive time-limited service policies. We have specifically pointed out two variants of the time-limited service policies-nonpreemptive and look-ahead. The former models the token-bus, and the latter models the token-ring and FDDI. The major result of this paper is an iterative algorithm to approximate the mean delays for the nonpreemptive policy. Numerical results show that the algorithm is reasonably accurate for both deterministic and exponential frame sizes. Last, we apply the algorithm to the performance analysis of a token-bus. In the appendix, we also outline a similar approach for the look-ahead policy     

基于信道借用和信号预测的切换方法

随着业务需求的日益增长,蜂窝也越变越小,移动蜂窝通信环境中的切换成为日益重要的问题。在CDMA蜂窝系统中使用软切换,为了解决切换时的信道短缺问题,提出了许多解决方法。该文中提出了称为基于信道借用和信号预测的切换算法。当切换请求到达蜂窝时,如果没有空闲信道,就将从参与软切换的静止呼叫借用一信道,并将借用的信道分配给移动呼叫的切换请求.如果没有信道可借用,就将切换请求放入队列中,使用信号预测的方法来确定队列中的优先级。并将此切换方式的性能与其它切换方式进行了比较。     

Approximate aggregation for linear multivariable systems

Given a reduced order model of a high order system, the question of approximate aggregation is examined. An error analysis indicates that there is an optimal choice for the aggregation matrix. The method shows that reduced order models are related to Luenberger observers. A comparison with the method of singular perturbations is made.     

Approximate transfer functions for multivariable systems

An approximation, valid over a limited region of the s plane, is given to a single path in a multivariable system. The inference of system instability from instability of this approximate transfer function is discussed, and it is shown that it is not sufficient for the approximation to be valid over a region of the real-frequency axis alone. This point is demonstrated by an example.     

Nonpreemptive priority scheme for the S-MAC protocol in multimedia mobile sensor networks

S-MAC is a well-known medium access control (MAC) protocol designed for wireless sensor networks (WSNs). S-MAC uses a few novel techniques to reduce energy consumption and support self-configuration. Besides, S-MAC also achieves good scalability and collision avoidance by utilizing a combined scheduling and contention scheme. However, S-MAC does not have any priority scheme, making it unsuitable for multimedia applications and suffering from varying degree of starvation and fairness problems. In this paper, we propose a simple, efficient, but yet well-performing sliding contention window control mechanism to modify the S-MAC protocol such that priority can be supported along with the multimedia applications in multimedia mobile sensor networks. Furthermore, the proposed scheme could solve the starvation problem and alleviate the fairness problem. An analytic model is carried out to study the saturation throughput of proposed scheme. In addition, simulations were also conducted to analyze the proposed scheme and the results show that the proposed scheme is able to carry the prioritized traffic and mitigate the starvation and fairness problems.     

Performance analysis of flexible hierarchical cellular systems witha bandwidth-efficient handoff scheme

In this paper, a bandwidth-efficient handoff strategy is proposed and analyzed for hierarchical cellular systems. Mobile subscribers are divided into two classes, i.e., low- and high-mobility subscribers. In our bandwidth-efficient handoff strategy, each of the originating and handoff calls of both slow and fast mobile subscribers first tries to get a channel in a microcell. Macrocells are overlaid over the microcells to handle overflowed calls. A call overflowed into a macrocell requests a take-back to the new microcell at each border crossing of the microcells. The request will be accommodated by the target microcell if there is any idle traffic channel in the cell. An analytical model is developed, and the most important performance measures such as the blocking probability of originating calls and the forced termination probability of calls are evaluated. It is shown through extensive comparisons with other candidate handoff strategies that if the total traffic load of the system is not very heavy, our scheme has the best bandwidth efficiency and can provide better quality of service for mobile subscribers without bringing too much processing expense to the system