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We propose an analytical model to assess the throughput and call blocking rate of Opportunistic Spectrum Orthogonal Frequency Division Multiple Access network constituted of multiple classes of Secondary Users (SUs) and temporarily active Primary Users (PUs) of different priorities. In the case of PUs we consider low activity wideband and high activity narrowband users. While in the case of SUs we...
WiMAX packet networks are considered an attractive broadband wireless technology for 4G networks due to the support of quality of service (QoS) they provide. Radio resource allocation is an important part of the WiMAX QoS framework and a great part of its design and implementation is left to the vendor. Current WiMAX standard defines the real time polling service (rtPS) as the polling service for...
HCF controlled channel access (HCCA), defined in the IEEE 802.11e document, provides a sample scheduler to allocate transmission opportunity (TXOP) to QoS-aware stations (QSTAs). Since the calculation of TXOP duration is based on mean data rate, it is efficient for constant bit rate (CBR) traffic. For variable bit rate (VBR) traffic, however, delay bound of some admitted traffic flows may be violated...
This paper shows a delay probability of some traffics transmitted by each MT (Mobile Terminal) in a time slot in terms of VBR (Variable Bit Rate) traffic, analyzes that and proposes a generalization over new OFDM-based system to make up for the fault of existing WCDMA system. When a channel error exists, an average delay time processing in a time slot is analyzed and a generalization according to...
Variable bit rate (VBR) traffic may have a wide range of packet sizes and generation intervals. While the former can be handled in the IEEE 802.11e uplink scheduling, e.g., by adapting transmission opportunity (TXOP) durations according to backlogged traffic reports, the latter may cause packet losses if service intervals of the scheduling do not fit the generation intervals. In this paper, a scheduler...
Call admission control (CAC) plays a critical role in the performance of the IEEE 802.16 mesh networks. The IEEE 802.16 standard does not specify any CAC mechanisms. In this paper, based on bandwidth estimation, we propose a call admission control scheme in IEEE 802.16 centralized scheduling mesh mode. The proposed scheme does the admission control function by using the characteristic defined in the...
The constant and rapid expansion of the Internet at such a high rate has caused its traffic to double every four to six months. A large portion of this traffic is known to be multimedia and real time traffic, which has strict requirements in term of bandwidth, delay, jitter, and loss rate. Recent studies showed that constant bit rate (CBR) and variable bit rate (VBR) traffic can reduce both the transmission...
In the IEEE 802.16e OFDMA systems, the data mapping algorithm maps the data to the appropriate rectangular regions in the two-dimensional matrix of time and frequency domain. Each region is described by an Information Element (IE) which is used for signaling and occupies a slot. The IEs as well as vacant slots in the allocated rectangular region result in a substantial amount of overhead. In order...
Proportional fair (PF) scheduling algorithm selects a user according to the ratio between the user current channel rate and the user average channel rate, which provides a good performance in terms of fairness. However, PF scheduler can not guarantee a quality of service (QoS) requirement be achieved. Moreover, if a variable bit rate (VBR) traffic is considered under different channel conditions for...
One of the critical issues in multimedia applications is the support of quality of service (QoS) at an acceptable level. IEEE802.11e has proposed a simple scheduler but it proves unable to support QoS in variable bit rate traffic. This paper presents a novel scheduling algorithm named adaptive transmission opportunity (ATX) to support variable bit rate in multimedia services. In the proposed scheduling...
The mobile WiMAX (standard 802.16e) provides capabilities for adaptive radio resource allocation for users with a slowly changing channel. To achieve a performance gain possible under adaptive allocation it is important to choose an appropriate practical algorithm feasible for real-time implementation. In the paper the allocation task is considered as a two-step process and several combinations of...
For QoS requirements of real-time traffic, IEEE 802.11 working group introduces a QoS-aware channel access mechanism, called hybrid coordination function (HCF), which consists of contention-based enhanced distributed channel access (EDCA) and contention-free HCF controlled channel access (HCCA). The TXOP allocation and the admission control units of the HCCA reference scheduler are only appropriate...
With the increasing popularity of using WLANs for Internet access, the controlled channel access mechanism in IEEE 802.11e WLANs, HCCA, has received much more attentions since its inherent centralized mechanism is more efficient in handling time-bounded multimedia traffics. So far, only a few research works address the admission control problem of variable bit rate (VBR) traffic over HCCA. These existing...
We consider the problem of allocating bandwidth to a set of traffic flows at a statistical multiplexer to provide both quality-of-service (QoS) and resistance to a class of denial- of-service (DoS) attacks. The target application is QoS signaling in a mobile ad hoc network (MANET) environment where the channel bandwidth is variable and the mobile device handles bandwidth requests arriving from multi-hop...
An effective scheduler is proposed to improve the performance of IEEE 802.11e wireless local area networks (LANs), which adaptively adjusts the ratio of enhanced distributed channel access (EDCA) duration to controlled access phase (CAP) duration by tracking the amounts of variable bit rate (VBR) and constant bit rate (CBR) traffics in a real-time manner. Simulation results show that the proposed...
In this paper we present a novel traffic scheduling algorithm for IEEE 802.11e, referred to as ARROW (adaptive resource reservation over WLANs), which aims at providing improved performance for the support of multimedia traffic. The novel characteristic of this algorithm, compared to previous proposals, is that it performs channel allocations based on the actual traffic buffered in the various mobile...
The IEEE 802.11 working group is currently working on the standard IEEE 802.11e and introduces the hybrid coordination function (HCF) to provide better QoS support to real-time traffic. A reference design of simple scheduling and admission control algorithm is proposed in a TGe consensus proposal. However, this scheduling and admission control unit only consider the mean data rate and mean packet...
Traffic measurements taken from real data are highly desirable for validating traffic models, designing congestion control and flow control algorithms, implementing communication protocols, and developing switch architectures. This paper investigates the traffic characteristics of several applications in an ATM network with the goal of studying bursty traffic behavior and realizing the multiplexing...
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