IEEE802.16/WiMAX-Based Broadband Wireless Networks: Protocol Engineering, Applications, and Services

Dynamic radio resource and interference management for MIMO–OFDMA mobile broadband wireless access systems

In this paper, we discuss the effect of wireless link characteristics and mobility in wireless access broadband networks, and how major differences between wireline and wireless transmission links introduce a new networking paradigm with difficult and interesting challenges. We show that these differences have a direct impact on the packet-level quality-of-service defined by the packet loss, delay and jitter statistics. Moreover, we examine a number of alternatives such as forward error correction, antenna diversity and retransmission schemes to combat the time varying nature and high bit error rate of the wireless link, as well as how much and in what way these schemes can improve the packet-level quality-of-service. We also show that routing, call admission control, and capacity allocation functions of wireless access broadband networks need to take mobility into account. These functions can be invoked in a reactive manner at every hand-off event, or they can be invoked in a pro-active manner at the call setup time instead of being invoked at every hand-off event. In addition, we discuss the trade-offs between these two call control schemes, and show that each of these schemes is associated with a major cost. To find a balance between the cost of these two call control schemes, we use a connection tree as a basis for routing, call admission control, and resource allocation in wireless access broadband networks.

Online video transmissions over wireless networks are rising in popularity and have already become part of our daily life. In the meantime, it is necessary to address a number of challenges ranging from the scarce resources, time-varying, and high error rates, to the fluctuating bandwidth, unveiling the need for an adaptive mechanism to ensure a good video transmission. Adaptive Forward Error Correction (FEC) techniques with Quality of Experience (QoE) assurance are appropriate to deliver QoE-aware video data to wireless users in dynamic and high error rates networks. This paper proposes an adaptive Video-aware FEC and Fuzzy Logic-based mechanism to shield realtime video transmissions against packet loss in wireless networks, improving both user experience and the usage of resources. The benefits and drawbacks of the proposed mechanism compared with exiting work are demonstrated through simulations and assessed with QoE metrics.

The increasing popularity of wireless broadband access in local and wide area networks is the main expression of the need for flexible and ubiquitous wireless connectivity. In order to satisfy user resource requirements in the presence of volatility of the wireless medium, sophisticated multiple access and adaptation techniques are required, which alleviate channel impairments and increase system throughput. The use of multiple antennas at the base station allows intra-cell channel reuse by multiple spatially separable users through space division multiple access (SDMA) and hence enhances cell capacity. However, the employment of antennas in the physical layer raises significant issues in the medium access control (MAC) layer. We investigate the impact of antenna arrays on MAC layer channel allocation in the context of orthogonal frequency division multiplexing (OFDM), which is the predominantly proposed signaling scheme for wireless broadband access. We propose an algorithm to allocate channels to users based on their spatial separability properties, while appropriately adjusting beamforming weights and transmission rates for each user in a channel. The unified consideration of such adaptive techniques yields significant throughput benefits.

As wireless devices and the useful services they can deliver become more pervasive and affordable; the need for wireless broadband technologies meeting the demands of emerging market countries is growing. In this paper the technology choice in wireless broadband access and service architecture is discussed with reference to three important wireless broadband technologies and relevant parameters such as service activation, authentication and delivery, cost effectiveness and sustainability. The main focus of the article is towards wireless broadband technology deployment in developing countries and rural communities for providing innovative wireless broadband services.

Congestion in ATM communications is a significant issue as it can have a dramatic effect on critical or real-time data. Forward error correction (FEC) can be used to decrease or eliminate this effect. Conventional FEC has a uniform error correction capability, which can result in poor bandwidth utilization. Adaptive FEC is more suitable because it allows a different quality of service for each data type. In this paper a versatile adaptive FEC technique is proposed. It is shown that this technique can decrease the effect of congestion and increase the channel utilization.

Unmanned aerial vehicles (UAV) are rising in popularity together with video applications for both military and civilian use. Because of that, it is necessary to address a set of challenges related to the device movement, scarce resources as well as high error rates, making evident the need for an adaptive mechanism to strengthen video transmissions. Adaptive Forward Error Correction (FEC) techniques are known to be suitable to enhance the Quality of Experience (QoE) of video transmitted over error-prone wireless networks with high mobility. This book chapter proposes an adaptive video-aware FEC mechanism that uses motion vectors details to improve real-time UAV video transmissions, providing both higher user experience and better usage of resources. The benefits and drawbacks of the proposed mechanism along with the related work are analysed and put up for test through simulations and evaluated using QoE metrics.

The increasing demand for multimedia communication over wireless platform necessitates the QoS-aware packet scheduling schemes in Broadband Wireless Access (BWA) networks. This paper deals with the analysis of queue size of QoS-aware Weighted Hybrid Packet Scheduling Schemes (WHPSS) for heterogeneous traffic classes in BWA networks. By categorizing the heterogeneous traffics of BWA networks into several classes (i.e. Class-1, Class-2, Class-3) depending upon their QoS requirement, we analyze the effect of queue size in WHPSS using three dimensional Continuous Time Markov Chain (CTMC) model. The analysis has been carried out with respect to the several performance parameters such as queuing delay, packet loss rate and throughput. This paper aims to observe the effect of queue size for each traffic flow to maximize the throughput of the network under the specified constraint of queuing delay and packet loss rate. Thus, the analysis helps to determine suitable queue size in the BWA network under varied traffic condition satisfying the required QoS constraints.

Access to networked data and information services has taken on an ever increasing importance to users for business, entertainment, and social networking applications. Users want high-speed, high-reliability, and high-quality access to these information services to be ubiquitous and available when they are fully mobile. Having these services available in a mobile environment also provides additional opportunities for service providers to enrich their offerings with location- based services. This article describes the IEEE 802.20 standard that was developed to meet the unique requirements for supporting high-speed data services while at the same time supporting full user mobility. It is a standard optimized to provide (IP-based) broadband wireless (Internet) access in a mobile environment, thereby affording network operators superior performance (e.g., higher data rates, lower latency) and lower costs as compared to networks built using standards that are not optimized for that purpose. The standard includes an OFDM wideband mode and a 625k-multicarrier mode. TDD duplexing is supported by both the 625k-MC mode and the OFDM wideband mode; FDD duplexing is supported by the OFDM wideband mode. Both modes are designed to support a full range of QoS attributes, making this technology suitable to support real-time streaming service that has low delay and jitter requirements, as well as near-real-time data services, where low error rate can be traded off for delay. These characteristics of the 802.20 standard make it suitable to meet user requirements for wireless mobile access well into the twenty-first century.

Rain fade is a very critical problem in designing broadband wireless access systems operating at frequencies above 20 GHz. How to keep the system working robustly in both clear and rainy weather has always been a big concern. A successful design of such systems is therefore highly dependent upon detailed knowledge about the propagation environments, especially about the influences of rainfall events. In this paper, a new rain fading simulation model for broadband wireless channels is presented. The model can generate time-correlated rain fading waveforms based on previous rain rate and rain attenuation measurement results. Such effects as multipath, path loss and rainfall rate variation are included into the simulation model. The amplitude of the generated waveforms is Rician distributed, with the K factor as a function of rain rate, which is in agreement with the previous measurement results.

Although WiMAX, based on the IEEE 802.16 family of standards, has emerged as one of the major candidates for next generation networks, it is also clear that in the near future, the combination of several technologies will be required. In this sense, the support of mobility in heterogeneous environments, addressing broadband wireless, is one of the main requirements in next generation networks. This chapter presents an architecture based on the recently standardized IEEE 802.21 framework, integrating both mobility and Quality of Service (QoS) mechanisms, and accommodating different wired and wireless technologies, such as WiMAX, Wi-Fi, DVB, and UMTS. This architecture supports seamless mobility in broadband wireless access (BWA) networks, and thus, it is suitable for next generation network environments. The results, obtained through real experimentation of the implemented architecture through an advanced mobility scenario using a real WiMAX testbed, show that the architecture is able to provide QoS under dynamic scenarios, with fast integrated QoS and mobility signaling.

The three articles in this special section are devoted to wireless broadband communications, with special emphasis on WiMax and other new applications.

In order to satisfy the demand of future Broadband Wireless Access (BWA) with high mobility, high data rate and low cost, Tsinghua University proposes a novel BWA system named BRadio with independent intellectual property rights. This paper describes the BRadio system from the aspects of physical layer technologies, Medium Access Control (MAC), networking methods, and services. The physical layer technologies focus on Time domain and Frequency domain United Orthogonal Frequency Division Multiple Access (TFU-OFDMA), Time domain and Frequency domain United Single Carrier Modulation time division multiple Access (TFU-SCMA), Interleave Division Multiple Access (IDMA), and Multiple Input Multiple Output (MIMO). In MAC layer we describe several new functionalities in BRadio system. The networking methods of BRadio are divided into networking independently and networking with the existing networks. BRadio can support various services, among which, the Personal Media Service (PMS) is presented in detail. Relying on the technical superiority of its high data rate, high mobility and low cost, as well as its flexible networking and comprehensive service platform, BRadio has become a potential technical solution for BWA.

Relay is considered as a method to ensure capacity and coverage in the broadband wireless access (BWA) system. This paper proposes a type of MAC layer simulator architecture for the relay enhanced BWA networks, and then addresses the issue on the network topology when relay is introduced. Furthermore, downlink co-operative communication in such relay scenario is discussed on. The results show that the proposed relay enhanced BWA system outperforms the single-hop one on spectrum efficiency.

This dissertation is addressed to novel and high innovative technical solutions for broadband wireless access (BWA) networks.The proposed networks are compatible with the existing IEEE 802.11n wireless local area networks (WLANs), wireless metropolitan area networks (MANs) IEEE 802.16e and WiMAX systems(Worldwide Interoperability for Microwave Access).The proposed designs are linked to the specific requirements which will be incorporated into emerging IEEE 802.16m and LTE advanced (Long Term Evolution) standards.These standards aim at defining an air interface that can ensure high mobility, transmit high data rates and offer higher performance compared to the current standards.The dissertation focuses on advanced radio resource allocation schemes involving cross-layer optimization and hopes to influence these future standards.Radio Resource Management (RRM) algorithms optimize the radio resources especially spectral efficiency and reduce the power consumptions.This work studies mechanisms for downlink (DL) RRM in an environment which suffers from interference created by neighboring transmitters.Beamforming, scheduling and admission control are evaluated.After the description of state-of the-art techniques, advanced algorithms -strategies are developed and simulated.These algorithms take information coming from the radio site (RSSI, CSI, SNR, etc) or from the application layer side (QoS).