A bandwidth request reiteration mechanism for IEEE 802.16 wireless networks

The IEEE 802.16 is a leading technology for Broadband Wireless Access (BWA), where a Base Station (BS) provides a set of Subscriber Stations (SSs) with first-mile network access. Each SS has multiple connections directed to the BS, which are assigned bandwidth on a demand basis. Specifically, the BS allocates part of the channel as request slots, which are accessed by best-effort connections in a random access manner to transmit bandwidth requests. Although bandwidth requests sent by different SSs may collide the standard does not specify an explicit acknowledgment mechanism. This, and the bandwidth being assigned by the BS to each SS as a whole, may lead to critical inconsistencies between the perception of the SSs’ requirements at the BS and the actual SSs’ requirements, which in turn may entail SS service disruption. While the standard suggests that an SS should regularly update the BS about the backlog of its connections, the algorithm to do so is left unspecified. In this paper we propose a simple, yet effective, mechanism to be employed by the SSs, called Bandwidth Request Reiteration (BR²), which prevents deadlock from occurring. Using detailed packet-level simulation, we compare BR² to an alternative approach based on timeout, and show that BR² achieves better performance, in terms of the average transfer delay, while it does not incur a significant additional overhead, in terms of MAC signaling.     

An efficient energy saving mechanism for IEEE 802.16e wireless MANs

This paper presents an energy conservation scheme, Maximum Unavailability Interval (MUI), to improve the energy efficiency for the Power Saving Class of Type II in IEEE 802.16e. By applying the Chinese Remainder Theorem, the proposed MUI is guaranteed to find the maximum Unavailability Interval, during which the transceiver can be powered down. The proposed MUI only dynamically adjusts one parameter defined in the standard. In addition, it is fully compatible with 802.16e standard. We also propose a new technique to reduce the computational complexity when solving the Chinese Remainder Theorem problem. Simulation and analysis have been conducted to evaluate the performance.     

Energy saving mechanism in the IEEE 802.16e wireless MAN

In this paper, we study energy consumption for the IEEE 802.16e broadband wireless access (BWA) network, A mobile subscriber station goes to sleep-mode after negations with the base station and temporarily wake-up periodically for a short interval to check whether there is downlink traffic to it to decide whether it goes to wake-mode or continues to be in the sleep-mode. The sleep interval is increased exponentially upon no arrival traffic. We analytically model the sleep-mode scheme and validate the model with simulations.     

Cross-layer optimization for SVC video delivery over the IEEE 802.11e wireless networks

The Scalable Video Coding (SVC) standard extends the H.264/AVC with scalability support and is effective to adapt bitrate to the time-varying wireless channel bandwidth. In this paper, we propose a cross-layer optimization scheme, which includes packet prioritization and QoS mapping, for the delivery of SVC over the IEEE 802.11e wireless networks. The proposed structure enables interaction among different network layers, providing differentiated services for video packets. Our cross-layer optimization performs with the following information: (i) SVC packet prioritization at the application layer, (ii) service differentiation at the MAC layer, and (iii) interface queue (IFQ) occupation status at the link layer. We formulate the QoS mapping problem as a joint optimization of access category (AC) assignment and IFQ control. A novel and efficient solution is proposed to reduce the computational complexity of the joint optimization problem. Simulation results show that the proposed approach achieves notable improvement when compared to conventional methods.     

基于IEEE 802.16e的跨层上行调度架构设计

对IEEE 802.16标准的上行链路调度架构进行了研究,并联合MAC层和物理层,设计了一种跨层的上行调度结构,在满足移动性要求的同时增强了系统的QoS保障能力,使频谱利用率和吞吐量得到提高.     

Scheduler for IEEE 802.16 networks

The IEEE 802.16 standard was designed to support real-time and bandwidth demanding applications with quality of service (QoS). Although the standard defines a QoS signaling framework and five service levels, scheduling disciplines for these service levels are unspecified. In this paper, we propose a scheduling scheme for the uplink traffic which is fully standard-compliant and can be easily implemented in the base station. Simulation results show that this scheme is able to meet the QoS requirements of the service flows.     

Advancement of MIMO technology in WiMAX: from IEEE 802.16d/e/j to 802.16m

WiMAX is the first cellular standard that employs OFDMA technology and provides true integrated services for both fixed and mobile broadband access. Among the many new technologies adopted in WiMAX, MIMO antenna technology plays an essential role in delivering fast, rich-content, mobile broadband service reliably over extended coverage areas. In this article we provide a survey on the state of art of MIMO technologies in current WiMAX standards with an emphasis on practical engineering considerations. Moreover, we also briefly discuss the ongoing MIMO technologies in the evolution toward the next-generation WiMAX network.     

Cross-layer design for wireless networks

As the cellular and PCS world collides with wireless LANs and Internet-based packet data, new networking approaches will support the integration of voice and data on the composite infrastructure of cellular base stations and Ethernet-based wireless access points. This article highlights some of the past accomplishments and promising research avenues for an important topic in the creation of future wireless networks. We address the issue of cross-layer networking, where the physical and MAC layer knowledge of the wireless medium is shared with higher layers, in order to provide efficient methods of allocating network resources and applications over the Internet. In essence, future networks will need to provide "impedance matching" of the instantaneous radio channel conditions and capacity needs with the traffic and congestion conditions found over the packet-based world of the Internet. Furthermore, such matching will need to be coordinated with a wide range of particular applications and user expectations, making the topic of cross-layer networking increasingly important for the evolving wireless buildout.     

A queuing model for distributed scheduling in IEEE 802.16 wireless mesh networks

The IEEE 802.16 standard for wireless broadband networks includes the mesh mode in its specifications, where network nodes interact to deliver packets from a client to a remote destination through intermediate nodes. This paper presents a study of the capacity of IEEE 802.16 wireless networks in mesh mode by using M/G/1/L queuing model that represents each network node by incorporating the features of the standard in order to calculate the average delay and throughput in the node. An iterative method integrates the calculation results at each node, obtaining the end‐to‐end delay from any node of the mesh to the Base Station. Because of multiple hops, a node far from the Base Station may have its flows damaged. To minimize this problem, we propose a criterion for a fair distribution of resources. We show the numerical results of the model which indicate a good fit when compared with simulation results. Copyright © 2013 John Wiley & Sons, Ltd.     

Cross-layer Scheduling Algorithms for IEEE 802.16 Based Wireless Mesh Networks

Wireless mesh network (WMN) is emerging as an important networking architecture for future wireless communications. The mesh mode supported in IEEE 802.16 protocol provides a TDMA solution for WMN, in which scheduling is an important issue. In this paper, we discuss the issues on how to satisfy a set of bandwidth requests in IEEE 802.16 WMNs using minimal radio resources (or solving minimal schedule length problem). In consideration of transmission overhead and adaptive modulation and coding (AMC), two cross-layer scheduling algorithms are proposed, namely max-transmission and priority-based algorithms. In particular, they are proposed based on a physical interference model, instead of a protocol interference model as suggested in the literature. For the priority-based algorithm, we study several priority criteria based on different cross-layer information. An iterative scheme for QoS traffic is introduced to guarantee fairness when traffic load exceeds the network capacity. Simulation results show that our algorithms outperform the existing schemes based on protocol model, and they also ensure better fairness among different nodes.     

Adaptive packet scheduling for the uplink traffic in IEEE 802.16e networks

IEEE 802.16e is a telecommunication standard technology designed to support a wide variety of multimedia applications. It defines five service classes, each one with its respective QoS requirements, but does not define the scheduling algorithm for these service classes. In this paper, an adaptive packet scheduling algorithm for the uplink traffic in IEEE 802.16e networks is proposed. This algorithm is designed to be completely dynamic, mainly in networks that use various modulation and coding schemes (MCSs). The algorithm is applied directly to the bandwidth request queues in the base station (BS) and aims at supporting the real‐time and non‐real‐time applications. Using a cross‐layer approach and the states of the bandwidth request queues in the BS, a new deadlines based scheme was defined, aiming at limiting the maximum delay to the real‐time applications. Moreover, this algorithm interacts with the polling management mechanisms of the BS and controls the periodicity of sending unicast polling to the real‐time and non‐real‐time service connections, in accordance with the QoS requirements of the applications. The proposed algorithm was evaluated by means of modeling and simulation in environments where various MCSs were used and also in environments where only one type of modulation was used. The simulations showed satisfactory results in both environments. Copyright © 2012 John Wiley & Sons, Ltd.     

Adaptive scheduling mechanism for IPTV over WiMAX IEEE 802.16j networks

A WiMAX technology is a very promising Broadband Wireless Access technology that is able to transmit different service types. This latter can have different constraints such as traffic rate, maximum latency, and tolerated jitter. The IEEE 802.16 Medium Access Control specifies five types of QoS classes: UGS, rtPS, ertPS, nrtPS, and BE. However, the IEEE 802.16 standard does not specify the scheduling algorithm to be used. Operators have the choice among many existing scheduling techniques. Also, they can propose their own scheduling algorithms. In this paper, we propose a scheduling strategy (Adaptive Weighted Round Robin, AWRR) for various Internet Protocol Television (IPTV) services traffic over 802.16j networks. Our scheme adapts dynamically the scheduler operation to according queue load and quality of service constraints. In particular, the proposed mechanism gives more priority to high definition television and standard definition television traffic by using two schedulers. The proposed scheduling algorithm has been simulated using the QualNet network simulator. The experimental results show that our scheduler schemes AWRR have a better performance than the traditional scheduling techniques for rtPS traffic, which allows ensuring QoS requirements for IPTV application. Copyright © 2012 John Wiley & Sons, Ltd.     

Real-time CBR traffic scheduling in IEEE 802.16-based wireless mesh networks

This paper studies packet transmission scheduling for real-time constant-bit-rate (CBR) traffic in IEEE 802.16-based wireless mesh networks. We first formulate and solve the scheduling problem as a binary linear programming problem. The computational complexity of the optimum scheduling solution may prevent it from being implemented in practice. We then propose a heuristic scheme, namely bottleneck first scheduling scheme, where scheduling decisions at stations (base station or subscriber stations) with higher traffic loads are done before those at stations with lower traffic loads. At each station, scheduling decisions for CBR packets with more hops to their destinations are done first. Numerical results show that the proposed scheduling scheme achieves the same capacity as the optimal one while obtaining satisfactory delay performance. Dongmei Zhao received the Ph.D. degree in Electrical and Computer Engineering from the University of Waterloo, Waterloo, Ontario, Canada in June 2002. Since July 2002 she has been with the Department of Electrical and Computer Engineering, McMaster University, Hamilton, Ontario, Canada where she is an assistant professor. Dr. Zhao’s research interests include modeling and performance analysis, quality-of-service provisioning, access control and admission control in wireless networks. Dr. Zhao is a member of the IEEE and a registered Professional Engineer of Ontario. Jun Zou received the B.S. and M. Eng. Degrees from Tianjin University, China in 1999 and 2002, respectively. He worked at Siemens Communication Networks Ltd., Beijing from 2002 to 2004. Currently, he is a Ph.D. student at McMaster University, Canada. His research interests include wireless networking, routing protocols, architecture of next generation networks, network security and their applications in telecommunication industry.     

基于802.16e OFDMA下行链路物理层仿真及性能分析

重点分析IEEE802.16e OFDMA物理层的关键部分,针对不同信道条件下,尤其是高车速条件下,为了克服无线信道的频率选择性衰落和较大的多普勒频偏带来的ICI(信道间干扰),接收机关键部分的设计。最后给出了完整的物理层平台在不同信道条件下的整体性能仿真结果。     

Performance analysis and enhancements for IEEE 802.11e wireless networks

The IEEE 802.11 WLAN legacy standard cannot provide QoS support for multimedia applications. Thus, considerable research efforts have been carried out to enhance QoS support for 802.11. Among them, 802.11e is the upcoming QoS-enhanced standard proposed by the IEEE working group. This article describes in detail the new QoS features of 802.11e based on the latest version of the standard draft. We investigate the performance of 802.11e through computer simulations. Using simple examples, we show the effectiveness of adaptive schemes under the 802.11e framework.     

Modeling and performance evaluation of the sleep mode in the IEEE 802.16e wireless networks with self-similar traffic

for minimizing the total system cost.     

On the optimization of the contention resolution mechanism for IEEE 802.16 networks

The IEEE 802.16 standard defines a contention bandwidth request mechanism offering QoS-aware broadband access through a wireless medium. According to the standard, the Base Station (BS) is responsible for granting the requests issued by the Subscriber Stations (SSs). The SSs communicate their requests to the BS by placing their requests into the uplink subframe, using the contention period defined within the subframe for this purpose. The size of contention period, defined in minislots, is fixed by the BS on a frame by frame basis. The remaining part of the uplink subframe is used to carry the data frames. A tradeoff between these two periods of the uplink subframe is required for an effective operation of the system. On the contrary, if the size of the contention is shorten below a certain threshold, the SSs may be unable to place their requests within the time required by the end-user applications. In this paper, we introduce an adaptive mechanism of the contention period size. The proposed mechanism takes into account the varying operation conditions of the system by estimating the number of stations that may be placing a request. Simulation results confirm that our proposal outperforms other mechanisms having recently been reported in the literature.     

Delay versus energy consumption of the IEEE 802.16e sleep-mode mechanism

We propose a discrete-time queueing model for the evaluation of the IEEE 802.16e sleep-mode mechanism of Power Saving Class (PSC) I in wireless access networks. Contrary to previous studies, we model the downlink traffic by means of a Discrete Batch Markov Arrival Process (D-BMAP) with Ν phases, which allows to take traffic correlation into account. The tradeoff between energy saving and increased packet delay is discussed. In many situations, the sleep-mode performance improves for heavily correlated traffic. Also, when compared to other strategies, the exponential sleep-period update strategy of PSC I may not always be the best.     

IEEE802.16中一种改进的跨层QoS调度架构设计

IEEE802委员会制定了一个解决“最后一公里”宽带无线城域网（WMAN）接入问题的全球统一标准,即IEEE802．16标准。它定义了支持多种业务类型的独立于具体物理层的MAC层和多个物理层。对于802．16系统的QoS保障,标准中详细规定了服务类别的划分以及系统的Qos框架和具体的信令交互机制,但没有规定具体的QoS调度算法,而是留给厂家设计。因此本文在IEEE802．16已有QoS调度架构的基础上,设计出一种改进的跨层QoS调度架构,并详细介绍了该构架下各功能模块的功能和具体实现方法。