共查询到20条相似文献,搜索用时 78 毫秒
1.
Analysis of a hybrid cutoff priority scheme for multiple classes of traffic in multimedia wireless networks 总被引:7,自引:0,他引:7
In this paper, we propose and analyze the performance of a new handoff scheme called hybrid cutoff priority scheme for wireless
networks carrying multimedia traffic. The unique characteristics of this scheme include support for N classes of traffic, each may have different QoS requirements in terms of number of channels needed, holding time of the connection
and cutoff priority. The proposed scheme can handle finite buffering for both new calls and handoffs. Futhermore, we take
into consideration the departure of new calls due to caller impatience and the dropping of queued handoff calls due to unavailability
of channels during the handoff period. The performance indices adopted in the evaluation using the Stochastic Petri Net (SPN)
model include new call and handoff blocking probabilities, call forced termination probability, and channel utilization for
each type of traffic. Impact on the performance measures by various system parameters such as queue length, traffic input
and QoS of different traffic has also been studied.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
2.
Chang C. Chung-Ju Chang Kuen-Rong Lo 《Vehicular Technology, IEEE Transactions on》1999,48(4):1080-1091
We analyze a hierarchical cellular system with finite queues for new and handoff calls. Both the effect of the reneging of waiting new calls because of the callers' impatience and the effect of the dropping of queued handoff calls as the callers move out of the handoff area are considered, besides the effect of the guard channel scheme. We successfully solve the system by adopting the multidimensional Markovian chain and using the transition-probability matrix and the signal-flow graph to obtain the average new-call blocking probability, the forced termination probability, and the average waiting time of queued new and handoff calls. We further investigate how the design parameters of the buffer sizes and guard channel numbers in macrocell and microcells affect the performance of the hierarchical cellular system. The results show that provision of a buffering scheme and guard channel scheme can effectively reduce the new call blocking probability and the forced termination probability in the hierarchical cellular system, and the effectiveness is more significant in the macrocell than in the microcells 相似文献
3.
A traffic management scheme is proposed in a multicode code-division multiple-access system supporting soft handoff that uses guard channels and a queue for real-time traffic. Preemptive queue control gives priority to queued handoff calls. Handoff traffic is derived as a function of the new call arrival rate, the size of the soft handoff region, mobile speed, the new call blocking probability, and the handoff failure probability. System performance with K types of calls is analyzed by introducing a concept of effective channel. The effects of the number of guard channels, the number of effective channels, system capacity, and other factors are numerically investigated. The effectiveness of the proposed queue control scheme is also observed in terms of handoff processing delay 相似文献
4.
Se-Hyun Oh Dong-Wan Tcha 《Communications, IEEE Transactions on》1992,40(7):1259-1269
Dimensioning procedures for prioritized channel assignment in a cellular radio network are considered. Under the cutoff priority discipline, the prioritized channel assignment procedures for a single cell and multicell system are formulated as nonlinear discrete capacity allocation problems. Exact incremental algorithms which efficiently solve the proposed problems are devised. They are based on the properties of the blocking probabilities of new calls and handoff calls. Given the number of available frequency channels together with the arrival rates and the grade of service (GOS) for both types of calls in each cell, algorithm SP1 generates an optimal channel assignment which ensures priority for handoff calls. Given the arrival rates and distinct GOSs for new and handoff calls, algorithm SP2 finds the minimum number of channels required in each cell. Algorithm MP extends algorithm SP1 to a multicell system and provides the prioritized channel assignment for all calls in the system. The algorithms are very fast and are appropriate for the fair allocation of frequency channels among cells 相似文献
5.
On optimal call admission control in cellular networks 总被引:10,自引:0,他引:10
Two important Quality-of-Service (QoS) measures for current cellular networks are the fractions of new and handoff “calls”
that are blocked due to unavailability of “channels” (radio and/or computing resources). Based on these QoS measures, we derive
optimal admission control policies for three problems: minimizing a linear objective function of the new and handoff call
blocking probabilities (MINOBJ), minimizing the new call blocking probability with a hard constraint on the handoff call blocking
probability (MINBLOCK) and minimizing the number of channels with hard constraints on both of the blocking probabilities (MINC).
We show that the well-known Guard Channel policy is optimal for the MINOBJ problem, while a new Fractional Guard Channel policy
is optimal for the MINBLOCK and MINC problems. The Guard Channel policy reserves a set of channels for handoff calls while
the Fractional Guard Channel policy effectively reserves a non-integral number of guard channels for handoff calls by rejecting
new calls with some probability that depends on the current channel occupancy. It is also shown that the Fractional policy
results in significant savings (20-50\%) in the new call blocking probability for the MINBLOCK problem and provides some,
though small, gains over the Guard Channel policy for the MINC problem. Further, we also develop computationally inexpensive
algorithms for the determination of the parameters for the optimal policies.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
In cellular networks, blocking occurs when a base station has no free channel to allocate to a mobile user. One distinguishes
between two kinds of blocking, the first is called new call blocking and refers to blocking of new calls, the second is called
handoff blocking and refers to blocking of ongoing calls due to the mobility of the users. In this paper, we first provide
explicit analytic expressions for the two kinds of blocking probabilities in two asymptotic regimes, i.e., for very slow mobile
users and for very fast mobile users, and show the fundamental differences between these blocking probabilities. Next, an
approximation is introduced in order to capture the system behavior for moderate mobility. The approximation is based on the
idea of isolating a set of cells and having a simplifying assumption regarding the handoff traffic into this set of cells,
while keeping the exact behavior of the traffic between cells in the set. It is shown that a group of 3 cells is enough to
capture the difference between the blocking probabilities of handoff call attempts and new call attempts.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
8.
Sachiko Yamanaka Katsunori Shimohara 《International Journal of Communication Systems》2006,19(3):317-333
This paper presents the analysis of CDMA cellular networks with channel sub‐rating. From users' point of view, our considered scheme gives higher priority to handoff calls over new calls by sub‐rating the existing connections when handoff calls find no idle channels upon their arrivals. Therefore, it is considered that the disadvantage of the soft handoff which needs more channels than the hard handoff is made up for. Handoff calls can also wait in a queue while they are in handoff areas if all channels are sub‐rated in the cell of interest. We mathematically model this scheme by applying queueing theory. Then, we analyse its performance to derive the blocking probabilities of the new and handoff calls, the probability that handoff calls leave the handoff area without getting new channels, the degradation ratio of the voice quality by sub‐rating, mean and coefficient of variation of the waiting time of handoff calls. In numerical results, the analytical results are compared with the simulation ones to validate our analytical approach. Moreover, we compare the sub‐rating scheme with full‐rating one with respect to some characteristic values to show the effect of sub‐rating. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
9.
Performance Evaluation and Resource Management of Hierarchical MACRO-/MICRO Cellular Networks using MOSEL-2 总被引:1,自引:1,他引:0
Aymen I. Zreikat Suleiman Yerima Khalid Al-Begain 《Wireless Personal Communications》2008,44(2):153-179
The paper presents a performance evaluation and resource management of hierarchical MACRO-/MICRO cellular networks using the
new Modeling and Evaluation Language (MOSEL-2). MOSEL-2 with new constructs has the ability to find the performance and reliability
modeling and evaluation of systems with exponential and non-exponential distributions. A MACRO/MICRO cell structure is solved
numerically and mathematically in this paper to handle the handoff calls. Additionally, a simulation program is written to
validate these results. In order to reduce the loss probability, a guard channels are introduced at the MICRO cell and channel
reservation at the MACRO cell. Additionally, the concept of queuing is introduced where there is a possibility for the handoff
calls from both MACRO and MICRO layers to be queued when all the resources are occupied. MOSEL-2 is used to find the numerical
solution for this problem with both exponential and general exponential (GE) distribution. The performance analysis show the
efficiency of the proposed scheme to manage the handoff calls and the ability of the suggested scheme to reduce the blocking
probability of handover calls and the loss probability as the main objective is to block the new connection rather than terminating
the ongoing connection as well as balancing the load all over the whole network. It is shown in this paper that there are
a set of important factors that affect the performance, such as: reservation policy, channel allocation, handover ratio, capacity
of the queue and the variation of the inter-arrival times. These factors are discussed via some important performance measures,
such as: new call blocking probability, blocking probability of handover calls, loss probability, utilization and the average
delay of the queue. 相似文献
10.
Jin Weon Chang Dan Keun Sung 《Vehicular Technology, IEEE Transactions on》2001,50(2):341-353
Soft handoff techniques in direct-sequence code-division multiple-access (DS-CDMA) systems provide mobile calls with seamless connections between adjacent cells. Channel reservation schemes are used to give high priority to more important soft handoff attempts over new call attempts. However, since the number of soft handoff attempts varies according to environmental conditions, fixed reservation schemes for handoff attempts can be inefficient. An adaptive channel reservation scheme is herein proposed to control the size of reservation capacity according to varying the number of soft handoff attempts. The proposed scheme also includes a balancing procedure between soft handoff failure and new call blocking to maximize the system capacity. To evaluate the performance of the proposed scheme, a Markovian model is developed that considers the interference-limited capacity effect of DS-CDMA systems. The analytical result shows that the proposed scheme yields a considerable enhancement in terms of new call blocking and soft handoff failure probabilities when compared with the conventional fixed channel reservation scheme 相似文献
11.
The Guard Channel Scheme (GCS) and Handoff Queueing Scheme (HQS) are the popular and practical strategies to prioritize handoff
calls in wireless cellular networks. A key issue of giving handoff calls the higher priority is how to achieve a tradeoff
among the handoff call blocking probability, new call blocking probability and handoff delay. This paper extends GCS and HQS
and presents an efficient handoff scheme that dynamically manages the channels reserved for handoff calls depending on the
current status of the handoff queue. A three-dimensional Markov model is developed to analyze the performance of this scheme
and investigate the desirable performance tradeoff. The Poisson process and Markov-Modulated-Poisson-Process (MMPP) are used
to model the arrival processes of new and handoff calls, respectively. The accuracy of this model is evaluated through the
extensive comparison of the analytical results to those obtained from discrete-event simulation experiments. Performance measures
in terms of the mean number of calls in the system, aggregate response time, aggregate call blocking probability, handoff
call blocking probability, new call blocking probability and handoff delay are evaluated. The analytical model is used to
investigate the effects of the number of channels originally reserved for handoff calls, the number of dynamic channels, and
the ratio of the rate of handover calls to the aggregate arrival rate on the system performance. 相似文献
12.
Yuguang Fang Yi Zhang 《Vehicular Technology, IEEE Transactions on》2002,51(2):371-382
Call admission control (CAC) plays a significant role in providing the desired quality of service in wireless networks. Many CAC schemes have been proposed. Analytical results for some performance metrics such as call blocking probabilities are obtained under some specific assumptions. It is observed, however, that due to the mobility, some assumptions may not be valid, which is the case when the average values of channel holding times for new calls and handoff calls are not equal. We reexamine some of the analytical results for call blocking probabilities for some call admission control schemes under more general assumptions and provide some easier-to-compute approximate formulas 相似文献
13.
In future personal communications networks (PCNs) supporting network-wide handoffs, new and handoff requests will compete for connection resources in both the mobile and backbone networks. Forced call terminations due to handoff call blocking are generally more objectionable than new call blocking. The previously proposed guard channel scheme for radio channel allocation in cellular networks reduces handoff call blocking probability substantially at the expense of slight increases in new call blocking probability by giving resource access priority to handoff calls over new calls in call admission control. While the effectiveness of a fixed number of guard channels has been demonstrated under stationary traffic conditions, with nonstationary call arrival rates in a practical system, the achieved handoff call blocking probability may deviate significantly from the desired objective. We propose a novel dynamic guard channel scheme which adapts the number of guard channels in each cell according to the current estimate of the handoff call arrival rate derived from the current number of ongoing calls in neighboring cells and the mobility pattern, so as to keep the handoff call blocking probability close to the targeted objective while constraining the new call blocking probability to be below a given level. The proposed scheme is applicable to channel allocation over cellular mobile networks, and is extended to bandwidth allocation over the backbone network to enable a unified approach to prioritized call admission control over the ATM-based PCN 相似文献
14.
As channel allocation schemes become more complex and computationally demanding in cellular radio networks, alternative computational models that provide the means for faster processing time are becoming the topic of research interest. These computational models include knowledge-based algorithms, neural networks, and stochastic search techniques. This paper is concerned with the application of a Hopfield (1982) neural network (HNN) to dynamic channel allocation (DCA) and extends previous work that reports the performance of HNN in terms of new call blocking probability. We further model and examine the effect on performance of traffic mobility and the consequent intercell call handoff, which, under increasing load, can force call terminations with an adverse impact on the quality of service (QoS). To maintain the overall QoS, it is important that forced call terminations be kept to a minimum. For an HNN-based DCA, we have therefore modified the underlying model by formulating a new energy function to account for the overall channel allocation optimization, not only for new calls but also for handoff channel allocation resulting from traffic mobility. That is, both new call blocking and handoff call blocking probabilities are applied as a joint performance estimator. We refer to the enhanced model as HNN-DCA++. We have also considered a variation of the original technique based on a simple handoff priority scheme, here referred to as HNN-DCA+. The two neural DCA schemes together with the original model are evaluated under traffic mobility and their performance compared in terms of new-call blocking and handoff-call dropping probabilities. Results show that the HNN-DCA++ model performs favorably due to its embedded control for assisting handoff channel allocation 相似文献
15.
In this paper, we present an analytical model of two-tier handoff mechanisms for a hierarchical NEMO system composed of access
routers (ARs), mobile routers (MRs), and visiting mobile nodes (MNs). In the proposed two-tier handoff mechanism, service
areas of MR and AR are respectively divided into handoff and non-handoff regions. Consequently, concurrent voice/data sessions
in a hierarchical AR-MR model can be classified into four types according to the locations of MN and MR within the MR's and
the AR's service areas, respectively. We build a mathematical model with 4-D Markov chains to analyze the performance in terms
of the system utilization and the blocking probabilities of new sessions and handoff sessions. For the purpose of validation,
we conduct experiments through simulation. Simulation results reveal that both the blocking probabilities of new sessions
and handoff sessions are very close to the analytical results, particularly when the system utilization is high. The impacts
of session residence time and session arrival rates on the blocking probabilities are also investigated. 相似文献
16.
We propose and analyze two handoff schemes without and with preemptive priority procedures for integrated wireless mobile networks. We categorize the service calls into four different types, namely, originating voice calls, originating data calls, voice handoff request calls, and data handoff request calls and we assume two separate queues for two handoff services. A number of channels in each cell are reserved exclusively for handoff request calls. Out of these channels, few are reserved exclusively for voice handoff request calls. The remaining channels are shared by both originating and handoff request calls. In the preemptive priority scheme, higher priority is given to voice handoff request calls over data handoff request calls and can preempt data service to the queue if, upon arrival, a voice handoff request finds no free channels. We model the system by a three-dimensional Markov chain and compute the system performance in terms of blocking probability of originating calls, forced termination probability of voice handoff request calls, and average transmission delay of data calls. It is observed that forced termination probability of voice handoff request calls can be decreased by increasing the number of reserved channels. On the other hand, as a data handoff request can be transferred from a queue of one base station to another, there is no packet loss of data handoff except for a negligibly small blocking probability. 相似文献
17.
The traffic performance of integrated 3G wide-band code division multiple access (WCDMA) and GSM/GPRS network is evaluated.
This type of network links two cellular radio systems which have different set of frequency bands and the same coverage size.
The base station of 3G WCDMA is installed on an existing GSM/GPRS site. Dual-mode mobile terminals use handoff to establish
calls on the better system. The soft handoff or inter-frequency hard handoff occurs when mobile terminals of 3G WCDMA or GSM/GPRS
move between two adjacent cells, respectively. The inter-system hard handoffs are used between 3G WCDMA and GSM/GPRS systems.
The data rate conversions between different systems, soft handoff region size, multiple data rate multimedia services, and
the effect of the mobile terminal mobility on the user mean dwell time in each system are considered in the study. The simulation
results demonstrate that a great traffic performance improvement on the complementary use of 3G WCDMA and GSM/GPRS cellular
radio networks compared with the use of GSM/GPRS cellular radio networks. When high-data rate transmission is chosen for low-mobility
subscribers, both the handoff failure probability, and carried traffic rates increase with the new call generation rate. However,
both rates decrease conversely with the increasing new call generation rate as soon as the new call generation rate exceeds
a critical value. This causes the integrated networks saturation. The higher mean speed for the mobile terminals produces
lower new call blocking probabilities and total carried traffic. The new call blocking probabilities and total carried traffic
increase with the size of the soft handoff region. 相似文献
18.
A queueing algorithm for new call requests has been proposed to increase the system capacity of traditional fixed channel allocation (FCA) handoff channel reservation schemes. However, mobility of queued call requests was ignored in previous literature. In this paper, a detailed analysis on the effects of the mobility of queued call requests is included in the analytic model. This is important because we found that the mobiles with queued call requests are very likely to leave the cell before granted a free channel. Computer simulation is performed and the results are compared with the numerical ones. It is found that the mobility of the queued new call requests reduces the average queueing delay, but increases blocking probability generally 相似文献
19.
Performance analysis of a preemptive and priority reservation handoff scheme for integrated service-based wireless mobile networks 总被引:2,自引:0,他引:2
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. 相似文献
20.
Rappaport S.S. Lon-Rong Hu 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1994,82(9):1383-1397
A hierarchical overlaid scheme suitable for high-capacity microcellular communications systems is considered as a strategy to achieve high system performance and broad coverage. High-teletraffic areas are covered by microcells while overlaying macrocells cover low-teletraffic areas and provide overflow groups of channels for clusters of microcells. New calls and handoff calls enter at both the microcell and macrocell levels. Handoff calls are given priority access to channels at each level. The layout has inherent load-balancing capability, so spatial teletraffic variations are accommodated without the need for elaborate coordination of base stations (wireless gateways). An analytical model for teletraffic performance (including handoff) is developed. Theoretical performance characteristics that show carried traffic as well as blocking, handoff failure, and forced termination probabilities are derived. Effects of nonuniform teletraffic demand and channel allocation strategies on system performance are discussed 相似文献