ISSN:1124-318X    

DOI:10.1002/ett.4460110402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2000

数据来源: WILEY

摘要:

AbstractWe propose an admission control policy for wireless multimedia networks that is based on the well known threshold‐based guard channel method. The new scheme deals with two different types of traffic classes; namely: voice and data. We assume two different thresholds, one for each traffic class. In addition. we propose to buffer the handoff data calls if no free channels are available rather than rejecting them. For handoff voice calls, we propose two methods. namely: a blocking method and a preemptive method. For the blockins method, we reject the handoff voice calls it no channels are available. For the precmptive method, an ongoing data call can be buffered and its channel allocated to the handoff voice call. We study the effect of the thresholds. buffer size and the application of the proposed methods on call blocking probabilities. It is shown that the new call blocking probabilities are only affected by the threshold values. Meanwhile, the data handoff blocking probability exhibited grcat improvement. For handoff voice calls, when the blocking method is applied. the blocking probability value increases slightly with the increase of buffer size. Meanwhile. for the preemptive method, the handoff voice call blocking probability significantly decreases as the buffer size increases. Based on these results. we develop an algorithm that uses the proposed policy to estimate the appropriate thresholds and buffer six which meet the required call blocking probabilities for each traffic typ

ISSN:1124-318X    

DOI:10.1002/ett.4460110403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2000

数据来源: WILEY

摘要:

AbstractIn the near future, the telecommunication services provided by wireless networks will be characterized by high throughput and flexibility. Today the challenge in this area is to find techniques which will make it possible to introduce multimedia capabilities into mobile communications. The application of a wireless network structure made up of pico‐cells to solve this problem will cause an increase in the handover rate. Therefore, a major requirement in a wireless environment is to design an effective call admission control (CAC) strategy to minimize the handover drop probability. Another important requirement is to maximize network utilization, in terms OF the average number of channels used. The target of the paper is to define an extension of the Guard Channel CAC strategy for adaptive‐rate traffic sources, in such a way that both the handover drop probability and network utilization are optimized. In order to assess the effectiveness of the proposed CAC strategy, two Markov models of the system are introduced: one, from the network point of view, to evaluate global system performance, and another, from the user point of view, to evaluate the performance each user is provided with by the network. Numerical examples conclude the paper to analyze which factors most affect performance when the traffic bit rate is adaptive and the proposed admission strategy is appl

ISSN:1124-318X    

DOI:10.1002/ett.4460110404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2000

数据来源: WILEY

摘要:

AbstractIn a previous work, we studied how to send a video stream over a noisy satellite channel using the scalability features of the MPEG‐2 standard. The base and the enhancemcnt tlows were sent with different levels of protection (bit and coding rates) in order to deal with the channel degradation. In this paper, we add Dynamic Rate Shaping (DRS), thus obtaining a greater flexibility in the choice of transmission parameters. In fact, it is possible to trim the required bandwidth in continuous mode in the working range, thus saving some bandwidth when keeping the video quality constant during changing fade conditions. The performances of DRS applied to both the non‐scalable and the scalable MPEG‐2 coded video streams are shown separately. An application of thc techniques presented is discussed, and some criteria are given for choosing the most suitable pammcters, according to the service quality require

ISSN:1124-318X    

DOI:10.1002/ett.4460110405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2000

数据来源: WILEY

摘要:

AbstractA Medium Access Control (MAC) protocol of the Reservation Random Access (RRA) family is integrated with a hierarchical video‐coding scheme, to realize effective real‐time video services over the up‐link of a mobile wireless network. For every picture or for each group of contiguous pictures (GOP), the encoder generates an information set organized in a hierarchical layered structure. The base layer contains the information needed to a low quality video; the other layers contain data, which, if received and decoded, can enhance the video quality. The basic idea is to reserve bandwidth only to grant the transmission of base layer information, and modify the MAC scheme to manage the video enhancement data together with voice/dota streams. by adaptively transmitting the increimental video information only it the performances of other traffic classes will not drop below a certain threshold. The aim or this proposal is the improvement of the video stream quality in low load conditions, without a significant reduction of other traffic classes performance during high load periods. Several simulation results show the effectiveness of the proposed m

ISSN:1124-318X    

DOI:10.1002/ett.4460110406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2000

数据来源: WILEY

摘要:

AbstractWe propose and analyze the performance of an algorithm for integrated power control and adaptive, modulationkoding to achieve a specitied range of packct error rate for real‐time applications in broadband wireless packet‐switched networks. The algorithm applies the Kalman‐filter method [I] for power control, and adapts packet transmission to an appropriate modulation level, according to the packet error requirement, and the radio and interference conditions. A new criterion for maintaining stable transmission power is derived. Based on the criterion, the proposed technique performs the link adaptation and adjusts transmission power to achieve the specified packet error rate. The effectiveness of the proposed method is dcmonstratcd by several numcrical exa

ISSN:1124-318X    

DOI:10.1002/ett.4460110407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2000

数据来源: WILEY

摘要:

AbstractWith the increasing penetration of wireless communications systems, customers are expecting the same level of service, reliability and performance from the wireless communication systems as the traditional wire‐line networks. Due to the dynamic environment, such as the roaming of mobile subscribers, maintaining a high radio frequency (RF) availability is one of the most challenging aspects in wireless network management. To date, in wireless network management, a call is dropped when the channel it uses goes down. In order to increase system end‐to‐end availability, an RF channel recovery scheme is proposed in this paper. When an RF channcl Pds, the channcl is replaced by another working channel and the call continues. The methods to replace failed RF channels of ongoing calls and to handle channel failures of handoR and new calls are investigatcd. Markov reward models are developed to compare system availability and performance. Automated generation and solution of Markov reward modcls is facilitatcd by a version of stochastic Petri nets that we call stochastic reward nets. The results show that the rccovcry schcme reduces the dropped calls and the blocked calls significantly under both light and normal trar

ISSN:1124-318X    

DOI:10.1002/ett.4460110408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2000

数据来源: WILEY

摘要:

AbstractIn this paper a novel handover initiation algorithm is proposed for next generation wireless systems, in the presence of a generic packet access protocol. By proper monitoring of the sequence of packets that may be lost due to channel impairments, handover triggering can bc strictly related to the Quality of Service (QoS) parameter of the source, In particular, a threshold length of the sequence of lost packets is used as a handover criterion for delay sensitive sources. In a log‐normal shadowing environmcnt, the algorithm pcrformance is derived analytically. Simulation is also used to validate the approximations introduced in the analysis. From numerical rcsults it is sccn that the novel algorithm can provide better performance than typical signal strcngth nlgorithnls used in second gcncrution mobile radio systems. Moreover, the proposed approach is rather general and may apply 10 a large class of sourecs and acccss protocol

ISSN:1124-318X    

DOI:10.1002/ett.4460110409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2000

数据来源: WILEY

摘要:

AbstractConsidering the high‐speed data transfer by the ABR service class in a wireless ATM network, we investigate the impact of forward and backward hard handover protocols on the performance of the three rate‐based ABR flow‐control schemes Explicit Rate Indication for Congestion Avoidance (ERICA+), Fuzzy Explicit Rate Marking (FERM) and a new promising adaptation of FERM, called FERMA. We evaluatc the performance of these flow‐control protocols by means of an object‐oriented simulation modcl of a basic client‐scrvcr architecture. Considering a standard hard handover protocol in a wircless ATM nctwork. wc show that our proposcd enhanced signaling schemes based on a congestion‐awarencssconceptand their integratibn into thc ABR flow control have a positive influence on the stability and efficiency of the cell transfer by ABR connections. Morcovcr, we point out that the new adaptation of the fuzzy‐control scheme FERM provides a promising altcrnativc lo the E

ISSN:1124-318X    

DOI:10.1002/ett.4460110410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2000

数据来源: WILEY

ISSN:1124-318X    

DOI:10.1002/ett.4460110411

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2000

数据来源: WILEY