http://nova.newcastle.edu.au/vital/access/services/Feed ${session.getAttribute("locale")} 5 http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:11677 We propose a simple unified analytical model to analyze the IEEE 802.11 DCF infrastructure BSS performance in terms of MAC delay, PLR, and throughput efficiency under non-homogeneous and non-saturation conditions. Our model accounts for: (i) asymmetric traffic load between an AP and its associated STAs of an infrastructure BSS; (ii) transition from the non-saturation to saturation mode (and vice-versa) from an AP perspective; (iii) heterogeneous traffic flows between STAs; and (iv) heterogeneous wireless channel conditions between BSSs of a multi-AP hotspot scenario, all in a single unifying framework. More specifically, we integrate a Markov chain model in conjunction with a finite queueing model to analyze the QoS performance of DCF infrastructure BSS, which will be useful for capacity analysis and the design of network control mechanisms. Extensive analyses and simulations have unveiled that the improper modeling or ignorant of backoff freezing for an infrastructure BSS will result in overly conservative bounds which will lead to low network utilization when deployed as admission control, particularly, in heavy load scenarios. 2013-03-26T05:59:36.000Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:11545 With the increasing demand for multimedia services on wireless networks, it is important to optimise air interface parameters to maximise throughput and QoS. In this paper, we examine the effect of WiMAX burst mapping and Round Robin - based packet schedulers on multimedia traffic and network capacity. In this work, we have simulated the IEEE802.16e air interface to examine the downlink channel performance in terms of subframe usage and subframe wastage. The paper presents simulation analysis of the IEEE802.16e downlink service flows for multimedia traffic using an OPNET model. Comparing the characteristics of the service flow parameters, the packet schedulers and the subframe resource allocation methods, we define a new scheduling algorithm based in the service flows QoS configured parameters and the WiMAX OFDMA subframe structure. The proposed new MDRR packet-scheduling algorithm for multimedia traffic shows improvements in the allocation procedures reducing the wastage from 40% down to 20%, improving subframe usage from 60% to 80% leading to serve 10 more users in the network. 2013-03-12T02:59:07.646Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:8744 The widespread use of IEEE 802.11 WLAN and the potential to deliver QoS demanding multimedia contents, with the advent of 802.11n standard, will position itself as one of the introductory de-facto wireless access networks in the emerging cognitive networks. Existing WLANs can be augmented with cognitive functionality by the introduction of cognitive radios. However, the frequency-agile cognitive radio supports dynamic spectrum access to channels, which are heterogeneous and have largely different propagation characteristics, from diverse parts of the available frequency spectrum. Although WLAN supports link adaptation in practice, most of the existing WLANs are DCF-based which will give rise to the well-known rate anomaly problem where the long-term throughput of stations are penalized by the lowest data rate peer under multirate operation. Hence, deploying a WLAN-based cognitive network results in nontrivial radio resource management. In this paper, we introduce the novel concept of load adaptation strategy (LAS) to manage dynamic channel conditions associated with multirate multi-AP multimedia WLAN-based cognitive network in a single unifying QoS framework. Particularly, we show that our distributed LAS arbitrates optimal load distribution by maintaining a QoS-balanced system through QoS-based handovers in an opportunistic yet altruistic manner. Through simulations, we show that rate anomaly in multirate environment can be mitigated, statistical QoS guarantee can be provisioned for multimedia traffic with QoS fairness and system capacity can be maximized. 2013-03-12T02:28:38.692Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:8743 The extensive deployment of 802.11 WLAN has positioned itself as the de-facto wireless access network for the 'last mile' connections. The potential for WLAN to deliver multimedia contents such as VoIP, video conferencing, streaming and data services will become a reality with the advent of 802.11n standard, promising data rate of up to 600 Mbps. Although these QoS demanding multimedia applications can be supported by the 802.11e standard, it offers limited QoS guarantee. Further, its possible adoption by the industry remains unclear due to high cost of hardware replacements. In this paper, we give a solution to provision QoS support for multimedia traffic in commercially deployed 802.11 a/b/g WLAN operating with fundamental distributed coordination function (DCF) access mechanism in a unifying QoS-inspired load optimization framework. We further postulate the notion of QoS balance as load criterion in heterogeneous WLANs where data rates and channel conditions are radically different. In practice, link adaptation employed to combat diverse channel conditions could lead to multirate operation and consequently the long-term throughput of stations are penalized by the lowest data rate peer. We argue that such rate anomaly can be mitigated by maintaining a QoS-balanced system. Simulations show that our solution provides service QoS guarantee for both real-time and non real-time traffic as well as achieves both throughput and QoS fairness under dynamic network conditions in a self-adjusting manner. 2013-02-06T00:02:27.508Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:8756 IEEE 1900.4 is the recently approved standard which specify a policy-based radio resource management (RRM) framework where the decision-making process is distributed between the network-terminal entities. By exploiting the cooperative exchange of context information between the network-terminal entities, the standard aims to facilitate the optimization of radio resource usage to improve the overall composite capacity and QoS of wireless networks in a multiple radio access technologies (multi-RAT) landscape. In this paper, we demonstrate how IEEE 1900.4 standard can be employed to legacy radio access network, in particular, a multiple access point (multi-AP) based WLAN to effectuate distributed radio resources usage optimization, corresponding to one of the three use cases defined in the standard through a load adaptation policy (LAP). Through simulations, we show that overall composite capacity and QoS in terms of QoS balance can be improved by 15% and 23% respectively and the total number of handover can be reduced by 72% with IEEE 1900.4 RRM as compared to a network-distributed RRM architecture. 2012-06-05T01:33:29.488Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:8754 With the increased deployment of WLAN access points (AP), the importance of IEEE 802.11x standard network is also increasing. Mass deployment of WLANs offers the advantage of increased QoS support for multimedia traffic by using an intelligent vertical handover technique combined with an advanced admission control algorithm. In this paper we analyze the performance of three different dynamic load distribution algorithms which can be used in a multi-AP based heterogeneous wireless network. Two of the algorithms are based on prediction technique and the third one is a reactive algorithm. In all cases, QoS-based vertical handover is initiated only after QoS degradation of a station is detected. All three algorithms are simulated using OPNET to compare their performances. 2012-06-05T01:32:42.002Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:5976 Always best connected (ABC) services allows multi- mode mobile terminals to stay connected to the best available networks, at anytime according to user preferences. One of the key aspects in realizing such ABC service is mainly attributed to an effective and dynamic access network selection process. However, most of the previous works consider the access network selection process as a static optimization problem which fails to address the dynamic QoS conditions intrinsic in wireless networks. One of the main challenges remains as no efficient way in obtaining dynamic QoS parameters such as packet delay, packet loss and jitter. In this paper, we proposed a novel dynamic access network selection algorithm capable of adapting to prevailing network conditions. Our algorithm is a dual stage estimation process where network selection performed using sequential Bayesian estimation relies on dynamic QoS parameters estimated through bootstrap approximation. Simulations demonstrate the effectiveness of our proposed algorithm which outperforms static optimization approach in a highly efficient manner. 2012-03-12T06:46:30.605Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:6152 With proliferation of the IEEE 802.11 WLAN and the emerging 802.11n standard, the WLAN is poised as a promising ubiquitous networking technology to support VoIP services, which is gaining popularity due to their high cost efficiency. However, the 802.11 WLAN is not designed to support delay sensitive traffic such as VoIP. This problem is magnified during a handover as user roam the WLAN network resulting in excessive handover latency and consequently packet loss. In addition, a 802.11 WLAN handover process is predominantly based on the physical layer detection without QoS considerations. This often causes overloading of access points and consequently all its associated connections would suffer from high delay, resulting in unacceptable QoS for the VoIP services. The former can be resolved by reducing handover latency to achieve seamless handover and the latter can be mitigated by employing link layer detection in the 802.11 WLAN handover process and having an appropriate admission control scheme. In this paper, we proposed an integrated load balancing scheme incorporating (i) QoS-based fast handover to support seamless handover by eliminating both detection and scanning phases from the 802.11 WLAN handover process; and (ii) soft admission control to protect QoS of existing voice connections when resources are low. This synergy guarantees service QoS during and after handover respectively. Simulations showed that our proposed integrated load balancing scheme is capable of providing seamless handover and QoS enhancements in terms of increased throughput, reduced packet loss and bounded delay when considering heterogeneous voice traffic of different packetization intervals. Particularly, our proposed scheme effectuate QoS balance of both delay and throughput which jointly optimize overall system utilization. 2012-03-07T23:20:04.632Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:6200 Multimedia Broadcast and Multicast Service (MBMS) specification was introduced in the release 6 of the 3GPP standard to deliver multimedia content to a large group of users in the UMTS network. With the MBMS system generally the same content is transmitted to multiple users in a unidirectional fashion, typically by multiple base stations to improve the coverage over a large geographical area. From the radio network point of view the standard supports the point-to-point (p-t-p) and the point-to-multipoint (p-t-m) transmission modes. In this paper we propose a group based p-t-m MBMS algorithm utilising the scalable video coding techniques to improve overall QoS of multimedia services. The group based MBMS algorithm has been proposed to support moderate to high data rate multicasting services over the DSDPA link. The proposed algorithm has been simulated using an OPNET simulation model. Initial results show that the proposed algorithm could offer higher data and improved QoS for MBMS users. 2012-03-07T23:11:40.719Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:6775 This paper presents a scheduling scheme for a FLO based advanced TDMA system to enable service multiplexing from user terminals. The FLO specifications allows different traffic types to use appropriate transport formats to meet QoS requirements of each class of traffic. Service multiplexing can be achieved by selecting appropriate transport formats for each traffic class and then combining them in a single packet and transmitting over a single slot of a TDMA air interface. The paper introduces a scheduling scheme known as LQP which can offer higher throughput for using a FLO based air interface. The paper presents some initial simulation results obtained from an OPNET based simulation model. 2012-03-07T06:37:14.722Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:716 A radio resource management scheme for WCDMA uplinks is proposed that manages quality of service (QoS) for heterogeneous services whilst maintaining high channel utilisation efficiency. The proposed system is partitioned into the 3 modules, viz. a QoS-sensitive rate scheduler, an inter-service and intra-service user prioritisation schemes, and a frame admission controller for dynamic resource reallocation. Users are allocated the minimum resources required to manage their QoS requirements through just-in-time delivery of payload, leaving more room for best-effort service users. The transmission urgency of each user is estimated by the rate scheduler based on a target transmission delay - a unique parameter used in the proposed resource management strategy to enable just-in-time payload delivery, service differentiation, and uncomplicated mapping of application requirements to QoS parameters. Transmission rate change requests from the rate schedulers are collectively processed through inter-service and intra-service priority queuing in a manner that is shown to exhibit fairness in allocation of resources amongst users of a heavily loaded network. The performance of the proposed strategy is explored through discrete-event simulations for 3 classes of traffic - voice, video and data, over the WCDMA uplink in the presence of short-term Rayleigh fading, ARQ, FEC, target transmission delays and FER targets in a multi-cell environment. Two alternatives for distributed resource management have been studied, with the UE or Node-B in control of resource allocation. The UE controlled resource management system is shown to achieve higher channel utilisation efficiency at the cost of fairness. The Node-B controlled resource manager respects the priority of speech, video and data traffic in heavily loaded systems, as reflected in 95 percentile packet transmission delays. 2011-12-20T22:20:03.635Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:6777 The IEEE 802.11 suite of WLAN standards are evolving to support an increase in emerging broadband multimedia applications, with their popularity attributed to simple, scalable and cost effective wireless broadband communication infrastructure. However, the most widely deployed generation of 802.11x based MAC protocols provide limited support for multimedia traffic, as no guarantee is provided on the quality of service (QoS) that a particular type of traffic will receive. Furthermore, the legacy 802.11 MAC exhibits high protocol overhead due to control frames, channel access, and the probability of contention. This article presents an overview of MAC layer enhancements designed to provide QoS support and higher throughputs in next generation WLANs, including IEEE 802.11e and 802.11n standards. Comprehensive simulation results are provided using an OPNET simulation model. 2010-09-24T01:10:14.553Z ]]>