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1.
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
2.
Future Personal Communication Networks (PCN) will employ microcells and picocells to support a higher capacity, thus increasing the frequency of handoff calls. Forced call terminations due to handoff call blocking are generally more objectionable than new call blocking. The proposed guard channel schemes for radio channel allocation in cellular networks reduce handoff call blocking probability at the expense of increases in new call blocking probability by giving resource access priority to handoff calls over new calls in call admission control. Under uniform traffic assumptions, it has been shown that a fixed number of guard channels leads to good performance results. In a more realistic system, non-uniform traffic conditions should be considered. In this case, the achieved call blocking probability may deviate significantly from the desired objective. In this paper, we propose a new adaptive guard channel scheme: New Adaptive Channel Reservation (NACR). In NACR, for a given period of time, a given number of channels are guarded in each cell for handoff traffic. An approximate analytical model of NACR is presented. Tabu search method has been implemented in order to optimize the grade of service. Discrete event simulations of NACR were run. The effectiveness of the proposed method is emphasized on a complex configuration. 相似文献
3.
Xiaomin Ma Yonghuan Cao Yun Liu Trivedi K.S. 《Vehicular Technology, IEEE Transactions on》2006,55(2):670-680
This paper investigates the features of a cellular geometry in code-division multiple-access (CDMA) systems with soft handoff and distinguishes controlling area of a cell from coverage area of a cell. Some important characteristics of the cellular configuration in soft handoff systems are used to propose a new design of efficient call admission control (CAC) in CDMA systems. Then, the paper constructs a continuous-time Markov chain (CTMC) model for CAC in CDMA with a soft handoff queue, obtains closed-form solutions, and thus develops loss formulas as performance indices such as the new blocking probability and the handoff dropping probability. In order to determine handoff traffic arrival rate, a fixed-point strategy is developed. Algorithms are also provided to stably compute loss probabilities and to determine the optimal number of guard channels. A new soft handoff scheme-eliminating pseudo handoff calls (EPHC)-is proposed to improve channel utilization efficiency based on mobility information. As an application of the loss formulas, the proposed modeling techniques are used to evaluate and compare the performance of conventional and proposed EPHC soft handoff schemes. Numerical results show the effectiveness of the proposed Markov chain models and the benefits of the new soft handoff scheme. 相似文献
4.
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
5.
6.
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
7.
Emerging mobile wireless networks are characterized by significant uncertainties in mobile user population and system resource state. Such networks require adaptive resource management that continuously monitor the system and dynamically adjust resource allocations for adherence to the desired system performance requirements. We propose adaptive resource management technique based on control theory. The controller dynamically solves resource allocation problem using feedback control laws. In the base algorithm, the number of guard channels is dynamically adjusted by feeding back the current handoff call dropping probability. The base algorithm is then enhanced in two ways: feeding back the instantaneous number of handoff calls and by probabilistically implementing a fractional number of guard channels. We study the effects of parameter choices on the performance of the proposed algorithms using discrete event simulation. Simulation results indicate that the feedback controllers can guarantee the predetermined call dropping probability under a variety of traffic conditions, and so can utilize the scarce wireless resource efficiently by accepting more new calls. 相似文献
8.
Evaluates four handoff priority-oriented channel allocation schemes. These give priority to handoff calls by reserving channels exclusively for handoff calls. The measurement-based handover channel adaptive reassignment scheme (MHAR-A) exclusively uses reserved handover channels for newly originated calls if a certain criterion is satisfied. All four schemes studied differ from the conventional guard channel-based handover priority-oriented channel allocation scheme. To study the schemes, a personal communication network (PCN) based on city street microcells is considered. A teletraffic simulation model accommodating a fast moving vehicle is developed, and the performance parameters are obtained. The performances of all four schemes are compared with the nonpriority scheme and the conventional guard channel-based handover priority-oriented channel allocation scheme. It was found that some of the channel allocation algorithms studied improved the teletraffic capacity over the nonpriority and the conventional guard case. Also, the probability of new call blocking and carried traffic was improved for three of the schemes when compared to the conventional guard scheme. The MHAR-A scheme did not perform up to expectation. Nevertheless, it can be used to finely control the communication service quality equivalent to the control obtained by varying the number of handoff channels in a fraction of one. Increasing the number of reserved handover channels in fraction of one can never be achieved in the conventional guard channel-based handover priority-oriented channel allocation scheme 相似文献
9.
Hassan Al-Mahdi Hamed Nassar Yasser Fouad Mohamed Ali 《Wireless Personal Communications》2013,69(2):579-599
In this paper, a channel assignment scheme is proposed for use in CDMA/TDMA mobile networks carrying voice and data traffic. In each cell, three types of calls are assumed to compete for access to the limited number of available channels by the cell: new voice calls, handoff voice calls, and data calls. The scheme uses the movable boundary concept in both the code and time domains in order to guarantee the quality of service (QoS) requirements of each type. A traditional Markov analysis method is employed to evaluate the performance of the proposed scheme. Measures, namely, the new call blocking probability, the handoff call forced termination probability, the data call loss probability, the expected number of handoff and the handoff link maintenance probability are obtained from the analysis. The numerical results, which are validated by simulation, indicate that the scheme helps meet the QoS requirements of the different call types. 相似文献
10.
H.K. Pati 《International Journal of Communication Systems》2007,20(9):1037-1058
In this paper, a distributed adaptive guard channel reservation (DAGCR) scheme is proposed to give priority to handoff calls. This scheme is built upon the concept of guard channels and it uses an adaptive algorithm to search automatically the optimal number of guard channels to be reserved at each base station. The quality‐of‐service (QoS) parameters used are the new and handoff call blockings. Simulation studies are performed to compare the present algorithm with the static guard channel policy. Simulation results show that this proposed algorithm guarantees the handoff call blocking probability to remain below the targeted threshold up to a substantially high offered load with a minimal blocking to new calls up to a moderate offered load and also shows significantly high channel utilization in all offered load conditions. This scheme is examined over a wide range of offered load. Thus, it seems the proposed scheme is very useful in controlling the blocking performances in wireless cellular networks. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
11.
《Vehicular Technology, IEEE Transactions on》2006,55(5):1603-1612
In this paper, a new soft handoff scheme for CDMA cellular systems is proposed and investigated. It is pointed out that some handoff calls unnecessarily occupy multiple channels with little contribution to the performance of handoffs in IS95/CDMA2000-based handoff schemes or systems. To alleviate performance degradation due to channel resource shortage during soft handoff, a new concept of channel convertible set (CCS), which contains several types of handoff calls that unnecessarily occupy extra channels by considering the relative mobility of the calls in the handoff area is introduced. A new scheme that reallocates those extra channels in the CCS to new handoff calls when there is no available free channel in the system is proposed. Furthermore, according to the variation of the CCS, the proposed scheme dynamically adjusts the number of guard channels reserved exclusively for handoff. Then, the feasibility and implementation issues of the proposed scheme are discussed. To evaluate and compare performance indexes of different soft handoff schemes, continuous-time Markov chain models are constructed. Automated generation and solution of the underlying Markov chains are facilitated by stochastic reward net models, which are specified and solved by stochastic Petri net package. Numerical results show that this scheme can significantly decrease both the number of dropped handoff calls and the number of blocked calls without degrading the quality of communication service and the soft handoff process. 相似文献
12.
K. Ioannou S. Kotsopoulos P. Stavroulakis 《International Journal of Communication Systems》2003,16(9):851-863
This paper presents a dynamic guard channel assignment technique based on a two‐layer cellular architecture which optimizes the blocking probability performance of high‐speed moving terminals (HSMT) and handoff calls of low‐speed moving terminals (LSMT), in a congested urban area. The lower layer of the proposed architecture is based on a microcellular solution, for absorbing the traffic loads of LSMT. The higher layer is based on a macro‐cell umbrella solution, for absorbing the traffic load of the HSMT. The results show that using the optimum number of channels and adjusting dynamically the number of guard channels in each layer, the blocking probability of the HSMT and the handoff blocking probability of LSMT is optimized having the minimum bad effect on the new call blocking probability of LSMT. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
13.
This paper proposes a prioritized call admission control (CAC) model to support soft handoff calls with quality of service (QoS) assurances for both the uplink and downlink connections in a CDMA system. CAC is formulated as a combinatorial optimization problem in which the problem objective is to minimize the handoff forced termination rate. The model, which is based on the adaptive channel reservation (ACR) scheme for prioritized calls, adapts to changes in handoff traffic where the associated parameters (reserved channels, and new and handoff call arrival rates) can be varied. To solve the optimization model, iteration-based Lagrangean relaxation is applied by allocating a time budget. We express our achievements in terms of the problem formulation and performance improvement. Computational experiments demonstrate that the proposed ACR scheme outperforms other approaches when there are fewer rather than more channels, and it reduces the handoff call blocking rate more efficiently when the handoff traffic is heavily loaded. Moreover, the model can be adapted to any kind of reservation service. 相似文献
14.
Traffic model and performance analysis for cellular mobile radio telephone systems with prioritized and nonprioritized handoff procedures 总被引:23,自引:0,他引:23
《Vehicular Technology, IEEE Transactions on》1986,35(3):77-92
A traffic model and analysis for cellular mobile radio telephone systems with handoff are described. Three schemes for call traffic handling are considered. One is nonprioritized and two are priority oriented. Fixed channel assignment is considered. In the nonprioritized scheme the base stations make no distinction between new call attempts and handoff attempts. Attempts which find all channels occupied are cleared. In the first priority scheme considered, a fixed number of channels in each cell are reserved exclusively for handoff calls. The second priority scheme employs a similar channel assignment strategy, but, additionally, the queueing of handoff attempts is allowed. Appropriate analytical models and criteria are developed and used to derive performance characteristics. These show, for example, blocking probability, forced termination probability, and fraction of new calls not completed, as functions of pertinent system parameters. General formulas are given and specific numerical results for nominal system parameters are presented. 相似文献
15.
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
16.
Adaptive and predictive downlink resource management in next-generation CDMA networks 总被引:1,自引:0,他引:1
Xin Wang Ramjee R. Viswanathan H. 《Selected Areas in Communications, IEEE Journal on》2005,23(6):1219-1232
Guard channels have been proposed to minimize handoff call dropping when mobile hosts move from one cell to another. Code-division multiple-access (CDMA) systems are power- and interference-limited. Therefore, guard capacity in CDMA networks is soft, that is, a given capacity corresponds to variable number of connections. Thus, it is essential to adjust the guard capacity in response to changes in traffic conditions and user mobility. We propose two schemes for managing downlink CDMA radio resources: guard capacity adaptation based on dropping (GAD), and guard capacity adaptation based on prediction and dropping (GAPD). In both schemes, the guard capacity of a cell is dynamically adjusted so as to maintain the handoff dropping rate at a target level. In the second scheme, there is an additional, frequent adjustment component where guard capacity is adjusted based on soft handoff prediction. We show through extensive simulations that GAD and GAPD control the handoff dropping rate effectively under varying traffic conditions and system parameters. We also find that GAPD is more robust than GAD to temporal traffic variations and changes in control parameters. 相似文献
17.
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
18.
Performance evaluation of two bandwidth allocation strategies in wireless mobile integrated services networks is carried out.
Performances of the proposed strategies are compared with those of the traditional guard channels and threshold strategies.
In the study, a single wireless cell which is accessed by voice and non-voice traffic types producing, respectively narrowband
and wideband calls is considered. In the proposed strategies a number of channels are reserved in a fixed or dynamic fashion
for the use of originating wideband calls in addition to the guard channels allocated for the handoff calls. The results indicate
that the two strategies have comparable advantages and by manipulating the number of reserved channels, desired performance
levels can be achieved. The dynamic reservation based strategy makes the system fairer for the originating wideband calls
while maintaining low handoff dropping probability and acceptable channel utilization levels. On the other hand, the fixed
reservation strategy provides a lower handoff call dropping at comparable channel utilization levels. The tradeoff is between
improving the handoff call dropping versus the originating wideband call blocking. Both strategies provide better performance
for the originating wideband calls compared with that provided by the traditional guard channels strategy.
相似文献
Dervis Z. DenizEmail: |
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.
Adaptive channel allocation for wireless PCN 总被引:1,自引:0,他引:1
In cellular networks, forced call terminations due to handoff call blocking are generally more objectionable than new call blocking. In order to maintain an acceptable call dropping probability rate, we propose, in this paper, two new guard channel schemes: an adaptive one – New Adaptive Channel Reservation (NACR) – and a dynamic one – Predictive Reservation Policy (PRP). In NACR, for a given period of time, a given number of channels is guarded in each cell for handoff traffic. In PRP, the number of reserved channels depends on the actual number of calls in progress in the neighboring cells. An approximate analytical model of NACR is presented. A Tabu search method has been implemented in order to optimize the Grade of Service. Discrete event simulations of PRP and NACR were run. The effectiveness of the proposed methods is emphasized on a complex configuration. 相似文献