A Cross-Layer Scheduling Algorithm With QoS Support in Wireless Networks

Wireless Body Area Networks (WBANs) deal with variety of healthcare services with diverse Quality of Service (QoS) requirements. However, QoS handling is a challenging problem in such networks. In general, QoS related problems can be addressed from different layers in the networking protocol suite. Design of an efficient QoS aware Medium Access Control (MAC) protocol can address this problem in MAC layer. This paper analyzes the QoS requirements of WBAN, identifies the requisites of QoS handling system, and outlines the trends that are being followed for its advancement with focus on QoS issues at MAC layer. We review some prior works, compare them, and analyze the current research concerned with problem of providing QoS in WBAN. We also explore some open issues and discuss them.

With the onset of multimedia applications, Quality of Service (QoS) in 802.11-based wireless ad hoc networks has been an essential area to look into. Standard wireless protocols such as IEEE 802.11b and IEEE 802.11e have been deemed unsuitable for multimedia traffic transmission in an ad hoc (multihop) network environment due to the unique network characteristics. As an ad hoc network is infrastructureless and distributed in nature, it gives rise to several challenges in QoS provisioning. In this thesis, we focus on the research of three key areas on QoS in ad hoc networks namely, buffer management in the medium access control (MAC) layer, cross-layer design and flow admission control. Firstly, we study MAC layer buffer management in the IEEE 802.11e protocol. The IEEE 802.11e MAC protocol provides QoS for multimedia traffic by probabilistic priority queueing. Ad hoc networks tend to generate a large volume of network control packets for route maintenance and these control packets are typically queued in the highest priority queue. As a result, higher priority control traffic is always being served, consuming most of the bandwidth and results in poor network performance for data traffic. We examine this problem and propose a dynamic buffer management scheme to mitigate it. By setting different threshold levels in different priority queues, we allow lower priority data traffic to be served when the higher priority control traffic is deemed to be excessive. Simulation of our proposed scheme has shown that our approach yielded better network performance compared to the standard protocol in terms of packet delivery ratio and average delay. Secondly, we study the cross-layer interaction between the MAC and Network layers to identify its impact on QoS. We select the IEEE 802.11e MAC protocol and Ad-hoc On Demand Distance Vector (AODV) routing protocol in our study since they are standardized protocols for wireless networks. In IEEE 802.11e MAC protocol, lower priority traffic has a higher probability of being blocked. Hence, the MAC layer will inform the Network layer of a broken link through the link notification function. In this case, AODV will re-route the paths that traverse this link. As a result, higher priority traffic which shares the same link as the lower priority traffic will undergo the same re-routing procedures. We termed this phenomenon path correlation effect. Under high traffic load, the path correlation effect will be more intense and hence degrade the QoS of higher priority traffic. To break the path correlation effect, we propose a cross-layer design called the Bundled Virtual Circuit (BVC). Our proposed BVC scheme not only addresses the path correlation issues, but also provides priority treatment from the Network layer to the MAC layer. Through our simulations, our proposed cross-layer design approach is proven to provide better network performance than the 802.11e/AODV protocols in terms of packet delivery ratio and delay. Finally, we examine flow admission control at the routing layer in ad hoc networks. Standard routing protocols such as AODV performs routing on a shortest path basis. In the presence of multiple routes, hotspots are likely to form among the intermediate nodes and thus lead to network congestion. In addition, existing routes are not well-protected from the introduction of new routes. We propose a flow admission control algorithm to be used with AODV. Our algorithm allows routes to be created through available bandwidth and congestion estimation. During the route discovery phase, each node will be gauged on its estimated available bandwidth and its backlog of packets in the MAC buffer. If a node does not have sufficient bandwidth, or has too many backlogged packets compared to the requested flow rate, it will not participate in the route discovery process. From simulations, our new scheme is able to provide better network performance than the standard AODV protocol in terms of delay. Our work in this thesis focuses on QoS provisioning in ad hoc networks from the MAC and network layer perspectives. By studying the network characteristics and protocols’ behavior, we investigate the various problems of providing QoS in an ad hoc network environment and propose three different schemes to improve the QoS provisioning at the MAC and network layers. We believe that our work is able to provide some insights to the research area on QoS in ad hoc networks.

The IEEE 802.16 standard, which includes specification for the medium access control (MAC) and physical (PHY) layers, was designed to handle the requirements of different contemporary applications with diverse QoS requirements. IEEE 802.16 standard is equipped with signaling and bandwidth allocation algorithms that can accommodate many connections with a variety of QoS requirements at one subscriber station (SS). The connections may be varied in their bandwidth and latency requirements, so several researchers proposed an IEEE 802.16 schedulers with different objectives to provide for wireless resource allocations over a different range of traffic models. In this paper, we conduct a comprehensive performance study of scheduling algorithms in Point to multipoint mode of WiMAX. We first make a classification of WiMAX scheduling algorithms, then simulate a representative number of algorithms in each class taking into account the characteristics of the IEEE 802.16 standard. We evaluate the algorithms with respect to their abilities to support multiple classes of service, providing quality of service (QoS) guarantees, fairness amongst service classes and bandwidth utilization. To the best of our knowledge, no such comprehensive performance study has been reported in the literature. Simulation results indicate that none of the current algorithms is capable of effectively supporting all WiMAX classes of service. We demonstrate that an efficient, fair and robust scheduler for WiMAX is still an open research area. We conclude our study by making recommendations that can be used by WiMax protocol designers.

Wireless Sensor Networks (WSNs) have emerged as perhaps the most important networking paradigm of recent times, both in terms of their commercial potential and also from a scientific point of view. WSNs are important commercially because of their many applications, spanning from civil to military applications such as structural monitoring of bridges, monitoring of wildlife, tracking of contaminants in the soil and atmosphere. Some of these applications have already proved to be commercially viable and indeed financially very attractive. WSNs are also very important from a scientific point of view, because of their unique features with respect to other types of wireless networks: nodes are typically immobile, and are required to carry a specific type of traffic (which is advantageous), have extreme restrictions on the energy they consume, the processing power they have, and the antennas they can use (which is disadvantageous); in addition, the data created at different sensors may be strongly correlated, which can be beneficial but requires only good algorithms that take advantage of it. Therefore, in the last few years we have experienced an important shift in research activities, moving from general purpose wireless networks to more focused topics specifically on WSNs, taking into account their specific advantages and peculiarities. An important recurring theme in research in this field is the need for energy efficiency, which is the thread of this special issue. The papers which appear in this issue have been carefully selected from the best IEEE PIMRC 2008 conference papers addressing the issue of energy efficiency in WSNs. The respective authors have been asked to provide a significantly extended version of the conference paper, which has subsequently undergone a rigorous review process according to the IJWIN publication standards prior to acceptance. The final set of papers addresses issues at physical, medium access control and networking layers, and to some extent at the application layer. All of these papers take into account the unique peculiarities, advantages, and shortcomings of wireless sensor networks, and propose algorithms and analyses that significantly advance research in the field. We sincerely hope you will enjoy reading them as much as we did. The author of the first paper ‘‘Power Management and Data Rate Maximization in Wireless Energy Harvesting Sensors’’ by Chandra R. Murthy, deals with the problem of power management and throughput maximization for energy neutral operation when using increasingly important but so far rarely analyzed Energy Harvesting Sensors (EHS) to send data over wireless links. The EHS is assumed to be able to harvest energy at a constant rate, and use a fixed part of the energy harvested in a slot for measuring the channel state. The rest of the harvested energy is available for transmission, but it can also be stored in an Wireless Sensor Networks (WSNs) have emerged as perhaps the most important networking paradigm of recent times, both in terms of their commercial potential and also from a scientific point of view. The papers that appear in this issue have been carefully selected from the best IEEE PIMRC 2008 conference papers which addressed the issue of energy efficiency in WSNs. The final set of papers addresses issues at physical, medium access control, networking and to some extend application layers. All of these papers take into account the unique peculiarities, advantages, and shortcomings of wireless sensor networks, and propose algorithms and analyses that significantly advance research in the field. Note that this activity has been partly supported by the NoE-216715 NEWCOM++.

The evolution of wireless sensor technology allows for the provision of enhanced services to miscellaneous application domains. In parallel, Quality of Service (QoS) support becomes necessary to satisfy the needs of these new service models. This paper presents QoS requirements from a service model perspective and describes challenges for QoS support in WSNs. We also provide a review of current efforts in Medium Access Control (MAC) QoS support in WSNs. Then, we investigate various performance metrics of IEEE 802.15.4 standard in order to determine the technological issues that arise. From the outcome of the experiments conducted, using ns-2, we identified that different schemes of services and application scenarios for different ways of deployment, scales of network and traffic load can satisfy diverse user needs and requirements.

IEEE 802.11p is proposed as the VANET wireless media access control (MAC) interface for the transmissions of emergency messages in V2V and V2I Communications. However, in a high mobility vehicular adhoc network (VANET), quality of service (QoS) of both the emergency message (EM) and handoff transmissions suffer from high collision probability of the contention-based media access mechanism and high interference exhibiting near the cell-edge that encodes a low coding rate of the adaptive modulation and coding (AMC) scheme. Thus, this paper proposes an efficient MAC for IEEE 802.11p to solve above critical issues, in which the approach consists of three main mechanisms to dynamically determine contention window (CW) based on the sigmoid function. Numerical results demonstrate that the analysis results are close to the simulation results, and thus justify the correctness of the mathematical analytical model. In addition, the proposed approach outperforms the compared approaches (including the IEEE 802.11p std.) in EM transmission delay, collision probability, throughput and MAC frame dropping probability.

To meet the growing demand for broadband wireless connectivity, integrating 3G and IEEE 802.16 networks is a clear and viable solution. To the best of the authors' knowledge, this is the first solution proposed for the integration of 3G and 802.16 wireless networks. We present a novel network and mobile client architecture that provides seamless roaming and mobility while maintaining connectivity across these heterogeneous wireless networks and provides quality of service (QoS) support. To provide QoS support to the application in the integrated network environment, the proposed architecture incorporates the procedures for activating a QoS session, the translation between network-specific QoS classifications, and network and session layer QoS support. We provide simulation results that show the viability and performance of the proposed QoS architecture

Due to the constraints of wireless communications in general and wireless sensor networks in particular, the layered model is poor in mechanisms to support QoS (Quality of service) in such networks. However, the cross-layer model proposes different techniques and architectures allowing collaboration between layers to overcome the limitations of the layered model. In this context, we have proposed the HCQ (Hierarchical Cross-layer approach for QoS provisioning in WSN) model which uses a cross-layer architecture allowing the support of QoS in a monitoring application with different types of traffic. Indeed, our contribution involves three layers, namely, the application layer, the network layer, and the MAC (Medium Access Control) layer. Synchronization between the three layers is implemented allowing the same interpretation of the assigned priorities.

Nowadays, Wireless Body Area Networks (WBANs) are used in many fields. WBANs are described as small sensor nodes that communicate wirelessly and provide services to the personal area. Quality of Service (QoS) is an essential issue for WBANs due to the importance of human life. QoS problems can only be solved with a robust Medium Access Control (MAC) protocol in WBANs. To find a solution to this problem, developers performed many MAC protocols for WBANs. ISO/IEEE 11073 health informatics defines the standard of personal health information and purposes to provide interoperability between medical technologies. This paper presents a MAC protocol that provides ISO/IEEE 11073 communication standards with QoS support, bases on cross-layer architecture. We designed a slot assignment scheme, prioritization mechanism, admission control mechanism to provide QoS. The performance evaluation of the proposed MAC protocol is compared with IEEE 802.15.4 and IEEE 802.15.6 protocols by considering end-to-end delay, packet loss ratio, and throughput parameters, and it has achieved out performance. It is observed that the proposed protocol doesn't exceed 45 ms delay, reached 81% traffic load, and a maximum error rate of 0.162%.

Below the Media Access Control (MAC) layer is the Physical (PHY) layer which deals with the actual transmission of the bits received from the MAC layer above into electromagnetic signals. This layer is optimized to implore power management in wireless networks. Power management is a crucial issue in wireless and mobile networks. In this paper, we propose an Adaptive Context-Aware Rate Selection (ACARS) algorithm to handle the issue of power consumption in wireless networks. This algorithm is implemented by optimizing the PHY layer to transmit efficiently as the number of nodes changes and we estimate the Signal-to-Noise Ratio (SNR) to the PHY layer. Results show that by using the appropriate power management technique, ACARS is reliable and efficient for power consumption in wireless networks which is a high demand for vehicular networks.

For the influence of Internet, 802.11 lacks the definition over the MAC (medium access control) layer, user-data are switched via upper protocols and the switching point is located in the network layer. This redundant architecture has shortcomings on efficiency and is not propitious to guarantee QoS (quality of service). In this paper, we propose a novel user-data switching mechanism in the lower layer, viz. the MAC layer in 802.11. This mechanism modifies the traditional finite state machine, the header format of user-data and the communication primitives of MAC layer to achieve the goal of reducing user-data plane. Our simulations show this user-data mechanism can better the relay efficiency and improve the QoS.

Energy saving and quality of service (QoS) support are two important issues of Long-Term Evolution Advanced (LTE-A) wireless networks. Unfortunately, achieving high energy saving efficiency often implies degradation of QoS support. In this paper, we address the issue of QoS support under Discontinuous Reception (DRX), the power saving mechanism of LTE-A. Different from previous studies which analyzed average packet delay under DRX mechanism, we adopt packet loss ratio due to violation of delay bound as QoS requirements of real-time applications. The problem of QoS support under DRX mechanism is defined as an optimization problem to maximize average power saving under the constraint that the packet loss ratio is no greater than a pre-determined threshold. We derive packet loss ratio and energy saving efficiency given DRX parameter values and propose an approach to select appropriate DRX parameter values. Simulations are conducted to verify our analysis. We found that the analytical results match well with simulations. Moreover, the energy saving efficiency achieved by the selected DRX parameter values is very close to that of the optimum solution.

Error control coding improves reliability and efficiency of wireless communication systems. This research delves into the latest advancements in error control coding schemes for wireless communication systems, with a specific focus on their application within the domain of Low Power Wide Area Networks (LPWANs) such as Narrowband Internet of Things (NB-IoT) systems, LoRa energy-efficient hardware design, random access control systems, and wireless sensor networks. In the context of LPWANs, particularly NB-IoT systems, we investigate the adaptive coding and modulation (ACM) in NB-IoT systems, which adapts coding rates and modulation techniques to changing channel circumstances. Comprehensive analysis of the literature review shows that the proposed approaches are more energy efficient and less error-prone than fixed coding and modulation schemes. Using Cell Design Methodology (CDM), Single Error Correction (SEC) codes are optimized for energy efficiency. Power and energy efficiency have improved in standard CMOS and CDM logic systems. This impacts IoT devices, memory storage, and security systems. Next, Forward Error Correction (FEC) is examined for ALOHA-based random-access control systems wherein packet loss rate and spectral efficiency metrics are mathematically calculated. FEC is beneficial, especially when time and frequency synchronization diverge. Monte Carlo simulations studied in the literature shows that FEC improves satellite communication systems. This review establishes benefits of FEC, notably in satellite communications systems. In addition, Wireless Sensor Networks (WSNs) error control techniques and network reliability and performance are examined along with Convolutional, Turbo, Low density parity check codes(LDPC), and Polar error correction coding (ECC) methods. We learn about their benefits, drawbacks, and implementation challenges by assessing their efficacy, efficiency, and applicability in wireless sensor networks (WSN) applications. This study further highlights advancements of energy-efficient error control coding when, integrated into network designs alongwith the trade-offs between efficacy and intricacy to help improve wireless communication networks. Finally, this study summarizes current error control coding approaches for wireless communication systems. We provide insights into improving reliability, energy conservation, and efficacy by examining ACM, CDM, FEC, and error correction coding (ECC) across varied domains including LPWAN and IoT technologies with earnest hope to facilitate researchers, engineers, and professionals working in the field of error control coding in wireless communication.

In order to support the quality of service (QoS) requirements for real-time traffic over broadband wireless networks, advanced techniques such as space-time diversity (STD) and multicarrier direct-sequence code division multiple access (MC-DS-CDMA) are implemented at the physical layer. However, the employment of such techniques evidently affects the QoS provisioning algorithms at the medium access control (MAC) layer. In this paper, we propose a space-time infrastructure and develop a set of cross-layer real-time QoS-provisioning algorithms for admission control, scheduling, and subchannel-allocations. We analytically map the parameters characterizing the space-time diversity onto the admission-control region guaranteeing the real-time QoS. Our analytical analyses show that the proposed algorithms can effectively support real-time QoS provisioning. Also presented are numerical solutions and simulation results showing that the space-time diversity can significantly improve the QoS provisioning for real-time services over wireless networks.

This paper presents a novel cross-layer approach to multiuser H.264/AVC video stream transmission over wireless networks. We consider the joint optimization of three layers of the protocol stacks: the application (APP) layer, the media access control (MAC) layer and the physical (PHY) layer. At the APP layer, the contribution of each packet to the perceptual video quality is evaluated by distortion effect of the packet loss, which is estimated by a Packet Relative Importance Index (PRII). At the MAC layer and the PHY layer, the Gilbert-Elliott (GE) model is employed to describe the time-varying nature of the wireless networks. An objective function for cross-layer optimization is developed based on the layered abstracted parameters from the APP layer, the MAC layer and the PHY layer. Our goal is to maximize the perceptual quality of the video transmitted through the wireless network with constraint of the limited resources. Simulation results show that the proposed scheme performs significantly than the conventional scheduling schemes for video transmission.