Providing Dynamic TXOP for QoS Support of Video Transmission in IEEE 802.11e WLANs

The IEEE 802.11e standard introduced by IEEE 802.11 Task Group E (TGe) enhances the Quality of Service (QoS) by means of HCF Controlled Channel Access (HCCA). The scheduler of HCCA allocates Transmission Opportunities (TXOPs) to QoS-enabled Station (QSTA) based on their TS Specifications (TSPECs) negotiated at the traffic setup time so that it is only efficient for Constant Bit Rate (CBR) applications. However, Variable Bit Rate (VBR) traffics are not efficiently supported as they exhibit nondeterministic profile during the time. In this paper, we present a dynamic TXOP assignment Scheduling Algorithm for supporting the video traffics transmission over IEEE 802.11e wireless networks. This algorithm uses a piggybacked information about the size of the subsequent video frames of the uplink traffic to assist the Hybrid Coordinator accurately assign the TXOP according to the fast changes in the VBR profile. The proposed scheduling algorithm has been evaluated using simulation with different variability level video streams. The simulation results show that the proposed algorithm reduces the delay experienced by VBR traffic streams comparable to HCCA scheduler due to the accurate assignment of the TXOP which preserve the channel time for transmission.Comment: arXiv admin note: substantial text overlap with arXiv:1602.0369

Packet level measurement over wireless access

PhDPerformance Measurement of the IP packet networks mainly comprise of monitoring the network performance in terms of packet losses and delays. If used appropriately, these network parameters (i.e. delay, loss and bandwidth etc) can indicate the performance status of the network and they can be used in fault and performance monitoring, network provisioning, and traffic engineering. Globally, there is a growing need for accurate network measurement to support the commercial use of IP networks. In wireless networks, transmission losses and communication delays strongly affect the performance of the network. Compared to wired networks, wireless networks experience higher levels of data dropouts, and corruption due to issues of channel fading, noise, interference and mobility. Performance monitoring is a vital element in the commercial future of broadband packet networking and the ability to guarantee quality of service in such networks is implicit in Service Level Agreements. Active measurements are performed by injecting probes, and this is widely used to determine the end to end performance. End to end delay in wired networks has been extensively investigated, and in this thesis we report on the accuracy achieved by probing for end to end delay over a wireless scenario. We have compared two probing techniques i.e. Periodic and Poisson probing, and estimated the absolute error for both. The simulations have been performed for single hop and multi- hop wireless networks. In addition to end to end latency, Active measurements have also been performed for packet loss rate. The simulation based analysis has been tried under different traffic scenarios using Poisson Traffic Models. We have sampled the user traffic using Periodic probing at different rates for single hop and multiple hop wireless scenarios. 5 Active probing becomes critical at higher values of load forcing the network to saturation much earlier. We have evaluated the impact of monitoring overheads on the user traffic, and show that even small amount of probing overhead in a wireless medium can cause large degradation in network performance. Although probing at high rate provides a good estimation of delay distribution of user traffic with large variance yet there is a critical tradeoff between the accuracy of measurement and the packet probing overhead. Our results suggest that active probing is highly affected by probe size, rate, pattern, traffic load, and nature of shared medium, available bandwidth and the burstiness of the traffic

Recent Advances in Wireless Communications and Networks

This book focuses on the current hottest issues from the lowest layers to the upper layers of wireless communication networks and provides "real-time" research progress on these issues. The authors have made every effort to systematically organize the information on these topics to make it easily accessible to readers of any level. This book also maintains the balance between current research results and their theoretical support. In this book, a variety of novel techniques in wireless communications and networks are investigated. The authors attempt to present these topics in detail. Insightful and reader-friendly descriptions are presented to nourish readers of any level, from practicing and knowledgeable communication engineers to beginning or professional researchers. All interested readers can easily find noteworthy materials in much greater detail than in previous publications and in the references cited in these chapters

Fairness and transmission opportunity limit in IEEE 802.11e enhanced distributed channel access

Tämä diplomityö tutkii lähetysaikarajan vaikutusta verkon reiluuteen IEEE802.11e tehostettuun ja hajautettuun kommunikaatiokanavaan pääsyyn. IEEE802.11e tuo palvelunlaatuominaisuuksia IEEE802.11 langattomiin verkkoihin. Asemat, jotka käyttävät IEEE802.11e-ominaisuuksia jakavat liikenteen neljään kategoriaan. Kategorioiden välinen erottelu saavutetaan neljällä parametrilla, jotka kontrolloivat kanavaan pääsyä. Tämä työ tutkii yhtä näistä parametreistä, lähetysaikarajaa, joka kontrolloi lähetyksen kestoa. IEEE802.11e antaa referenssiarvoja parametreille, mutta näillä arvoilla verkon kuormituksen lisääntyessä, alemman prioriteetin liikenne kärsii nopeasti. Hyvin pian kuormituksen lisääntyessä alemman prioriteetin liikenne ei pääse verkosta läpi lainkaan. Tällöin myös verkon reiluus on matala. Reiluuden parantamiseksi, häiritsemättä korkean prioriteetin liikennettä, tämä työ tutkii ison lähetysaikarajan käyttöä. Ensimmäisessä simulaatiosarjassa alemman prioriteetin lähetysaikaraja on ääretön. Tämä tarkoitta sitä, että alemman prioriteetin jono voi lähettää kaikki pakettinsa kun se pääsee lähettämään. Tulokset osoittavat, että ääretön lähetysaikaraja parantaa reiluutta kun kanava on kuormittumassa. Tulokset osoittavat myös, että ääretön lähetysaikaraja ei merkittävästi heikennä korkean prioriteetin liikennettä. Toinen simulaatiosarja keskittyy sellaiseen verkon kuormitustilaan, missä äärettömän lähetysaikarajan vaikutus on suurin. Näissä simulaatioissa lähetysaikarajan arvo on staattinen. Simulaatiosta toiseen lähetysaikarajan arvo muutetaan toiseen arvoon väliltä nolla-suurin sallittu arvo. Tulokset näistä simulaatioista ovat hyvin samanlaiset kuin ensimmäisen simulaatiosarjan tulokset.This thesis investigates the effect of transmission opportunity limit on fairness in IEEE802.11e enhanced distributed channel access. IEEE802.11e brings quality of service features into IEEE802.11 wireless local area networks. In stations operating with IEEE802.11e, traffic is divided into categories. Differentiation between these categories is achieved by using four parameters to control the channel access. This thesis investigates one of these parameters, the transmission opportunity limit, which controls the channel access duration. With the reference parameter values given in IEEE802.11e, as the network congestion level increases, low priority traffic suffers quickly to a point where none of it gets transmitted. This makes the network overall fairness poor. To improve fairness while not disturbing high priority traffic, this thesis investigates the use of large transmission opportunity limit values. In the first set of simulations, the low priority traffic transmission opportunity limit values are set to infinite. This means that the low priority queue can send all its packets when it gains access to the channel. The results show that infinite transmission opportunity limit improves fairness when channel is getting congested. Also infinite transmission opportunity limit does not notably weaken high priority traffic performance. Second set of simulations focuses on the network congestion level where the effect of the infinite transmission opportunity limit is the largest. In these simulations the transmission opportunity limit is set to static value ranging from zero to a maximum allowed value. The results from these simulations are similar to the results of the first simulation set

Estimating Average End-to-End Delays in IEEE 802.11 Multihop Wireless Networks

In this paper, we present a new analytic model for evaluating average end-to-end delay in IEEE 802.11 multihop wireless networks. Our model gives closed expressions for the end-to-end delay in function of arrivals and service time patterns. Each node is modeled as a M/M/1/K queue from which we can derive expressions for service time via queueing theory. By combining this delay evaluation with different admission controls, we design a protocol called DEAN (Delay Estimation in Ad hoc Networks). DEAN is able to provide delay guarantees for QoS applications in function of the application level requirements. Through extensive simulations, we compare performance evaluation of DEAN with other approaches like, for instance, DDA

Smart context-aware QoS-based admission control for biomedical wireless sensor networks

Wireless sensor networks are being used as the enabling technology that helps to support the development of new applications and services targeting the domain of healthcare, in particular, regarding data collection for continuous health monitoring of patients or to help physicians in their diagnosis and further treatment assessment. Therefore, due to the critical nature of both medical data and medical applications, such networks have to satisfy demanding quality of service requirements. Despite the efforts made in the last few years to develop quality of service mechanisms targeting wireless sensor networks and its wide range of applications, the network deployment scenario can severely restrict the network's ability to provide the required performance. Furthermore, the impact of such environments on the network performance is hard to predict and manage due to its random nature. In this way, network planning and management, in complex environments like general or step-down hospital units, is a problem still looking for a solution. In such context, this paper presents a smart context-aware quality of service based admission control method to help engineers, network administrators, and healthcare professionals managing and supervising the admission of new patients to biomedical wireless sensor networks. The proposed method was tested in a small sized hospital. In view of the results achieved during the experiments, the proposed admission control method demonstrated its ability, not only to control the admission of new patients to the biomedical wireless sensor network, but also to find the best location to admit the new patients within the network. By placing the new sensor nodes on the most favourable locations, this method is able to select the network topology in view of mitigating the quality of service provided by the network.Work supported by the Portuguese Foundation for Science and Technology, FCT, PhD Grant SFRH/BD/61278/2009. Miranda was supported by Portuguese funds through the CIDMA - Center for Research and Development in Mathematics and Applications, and the Portuguese Foundation for Science and Technology.info:eu-repo/semantics/publishedVersio