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Link adaptation is a way to increase data rates in wireless systems by adapting transmission parameters such as the modulation and coding rate. While link adaptation in single antenna systems is now mature, its application to multiple-input multiple-output communication links, presented in several emerging wireless standards, has been challenging. The main reason is that the space-time transmission strategy can also be adjusted in MIMO communication links, introducing a new dimension for adaptation. This means that practical MIMO link adaptation algorithms must also provide a dynamic adaptation between diversity and multiplexing modes of operation. This article reviews a recently proposed framework for adaptive MIMO architectures and shows how to use this framework to reduce adaptive control overhead. We also discuss practical implementation issues. Simulations in an IEEE 802.16e (mobile WiMAX) system illustrate the framework's potential improvements in data rates. [ABSTRACT FROM AUTHOR]

System-level simulation has been widely used to evaluate system performance. Simulation methodologies have also been comprehensively discussed in different organizations or institutions. Most of the simulation methodologies proposed, however, mainly focus on one area of specific technologies. How to evaluate the performance of multiple air interface systems (e.g., cdma2000, WCDMA, WiMAX, and their evolutions) in a fair and comprehensive manner has not been addressed extensively. This article presents a unified simulation methodology, including fading channel models, system configurations, and how to consider technology-dependent algorithms such as scheduling, overhead modeling, interference margin definition, and resource allocation based on system loading. This article uses this framework to compare three major existing radio technologies: cdma2000 1x EV-DO Rev. A, WCDMA HSPA, and mobile WiMAX based on 802.16e. Key simulation results based on our suggested system models and settings are presented and analyzed. It is shown that under our unified framework, the two CDMA systems exhibit higher spectrum efficiency than mobile WiMAX, especially on the downlink, while mobile WiMAX provides a higher peak rate. [ABSTRACT FROM AUTHOR]

Relaying and cooperation have re-emerged as important research topics in wireless communication over the past half-decade. Although multihop relaying for coverage extension in wireless networks is an old concept, it became practical only recently. Nowhere is this better illustrated than in the IEEE 802.16 working group, which has devoted a task group to incorporating relay capabilities in the foundation of mobile WiMAX-IEEE 802.16e-2005. Currently, this task group is in the process of finishing IEEE 802.16j, the Multihop Relay Specification for 802.16. This amendment will be fully compatible with 802.16e-2005 mobile and subscriber stations, but a BS specific to 802.16j will be required for relays to operate. This article presents an introduction to the upcoming IEEE 802.16j amendment and provides insight about the obstacles that practical system designers face when incorporating relaying into a wireless broadband network. [ABSTRACT FROM AUTHOR]

This article presents a high-level overview of the IEEE 802.22 standard for cognitive wireless regional area networks (WRANs) that is under development in the IEEE 802 LAN/MAN Standards Committee. [ABSTRACT FROM AUTHOR]

Over the past decade or so, the wireless industry has undergone many significant changes. Radio systems have moved toward forming heterogeneous wireless networks: collaborations of multiple radio access networks, which in some cases operate different radio access technologies, such as second- and third-generation cellular RATs, IEEE 802.x wireless standards, and so on. On the other hand, multimode reconfigurable user devices with the ability to choose among various supported RATs have become a reality, and devices and networks with dynamic spectrum access capabilities, allowing real-time sharing of spectrum resource usage among different systems, are expected to be a part of the future radio eco-space. As a result of these changes, there is a need to develop a standard that addresses the requirements and leverages the opportunities posed by such a versatile radio environment. To this end, IEEE 1900.4 aims to standardize the overall system architecture and information exchange between the network and mobile devices, which will allow these elements to optimally choose from available radio resources. In other words, the standard facilitates the distributed dynamic optimization of the usage of spectrum offered by the heterogeneous wireless network, relying on a collaborative information exchange between networks and mobile devices, thereby acting as a common means to improve overall composite capacity and quality of service for the served networks. This article provides a snapshot of IEEE P1900.4 in its current form, covering the scope and purpose of the standard, reference use cases for which the standard is applicable, its system and functional architectures, and finally, the information model for its main interfaces. [ABSTRACT FROM AUTHOR]

Providing users of multi-interface devices the ability to roam between different access networks is becoming a key requirement for service providers. The availability of multiple mobile broadband access technologies, together with the increasing use of real-time multimedia applications, is creating strong demand for handover solutions that can seamlessly and securely transition user sessions across different access technologies. A key challenge to meeting this growing demand is to ensure handover performance, measured in terms of latency and loss. In addition, handover solutions must allow service providers, application providers, and other entities to implement handover policies based on a variety of operational and business requirements. Therefore, standards are required that can facilitate seamless handover between such heterogeneous access networks and that can work with multiple mobility management mechanisms. The IEEE 802.21 standard addresses this problem space by providing a media-independent framework and associated services to enable seamless handover between heterogeneous access technologies. In this article, we discuss how the IEEE 802.21 standard framework and services are addressing the challenges of seamless mobility for multi-interface devices. In addition, we describe and discuss design considerations for a proof-of-concept IEEE 802.21 implementation and share practical insights into how this standard can optimize handover performance. [ABSTRACT FROM AUTHOR]

This article introduces a novel framework of cooperative coded video multicast (CCVM) for provisioning IPTV services in metropolitan area access networks based on the emerging integration of Ethernet passive optical networks and WiMAX. The framework of CCVM is formed through the central coordination and synchronization at the optical line terminal and advanced coding techniques across different system layers. A cross-layer design of video multicasting on a single ONU-BS is first introduced for dealing with the multi-user channel diversity and short-term channel fluctuations, where the scalable video coding with multiple description coding (MDC) at the source and physical layer superposition coding techniques at the channel are jointly considered. This approach is further extended into the scenario that involves multiple ONU-BSs for cooperative communications to tackle intercell interference. Finally, the efficiency of the proposed framework is demonstrated via a case study on the employment of CCVM strategy under the collaboration of multiple distributed ONU-BSs. [ABSTRACT FROM AUTHOR]

This article presents the outlook of the overall broadband market and operators' challenges in offering profitable mass market mobile data services. The concept of wireless relaying and its state of the art are then introduced, followed by a comprehensive description of a multihop relay system for WiMAX and related use cases. The article explains the impact of relays on network planning and presents an example of deployment cost analysis in different traffic scenarios and propagation conditions. Performance results show that multihop relaying is one of the most promising technologies that enables cost-effective enhancement of coverage, user throughput, and system capacity, and is especially suitable for the emerging markets and rural areas. [ABSTRACT FROM AUTHOR]

The IEEE 802.16 standard, commonly known as WiMAX, is the latest technology that has promised to offer broadband wireless access over long distance. Since 2001 WiMAX has evolved from 802.16 to 802.16d for fixed wireless access, and to the new IEEE 802.16e standard with mobility support. In this article we provide an. overview of the state-of-the-art mobile WiMAX technology and its development. We focus our discussion on QoS provisioning and mobile WiMAX specification. [ABSTRACT FROM AUTHOR]

As telecom operators are struggling to accommodate the existing demands of mobile users, new data consuming applications are emerging in the daily routines of mobile users (e.g., proximity-aware services). Moreover, 4G cellular technologies (WiMAX and LTE-A), which have extremely efficient physical and MAC layer performance, are still lagging behind mobile users' booming data demand. [ABSTRACT FROM PUBLISHER]

The article examines the development of WiMAX telecommunication technology in the Middle East and North America (MENA). The author cites four factors which accredit to the current surge in demand for WiMAX in the areas, they include telecommunication market liberalization, inadequacy of existing infrastructure, competition and 3G spectrum cost. It is noted that the 3.5 gigahertz (GHz) is the primary frequency band used to offer WiMAX services in MENA, and it was Algeria to be the first Arab country to have WiMAX service launched via Smart Link Communication.

This theme is strongly reflected in the four articles we have selected for this edition of the Consumer Communications and Networking series. The theme includes the integration of network features as well as new application and network integration. The first article in this edition, by Stuart Jacobs, focuses on the authentication mechanisms in WiMAX-based metropolitan networks. It discusses how digital certificates are handled and highlights the lack of multiple certificate authority support as an issue that prevents the interoperability of WiMAX devices from different manufacturers. [ABSTRACT FROM PUBLISHER]

The femtocell concept is an integral part of the telecommunication industry?s efforts to provide high-throughput, high quality services into the users? home. In contrast to conventional cell types which are well-planned by the operators, femtocell base stations are supposed to be installed by customers themselves, similar to a WiFi access point. Unlike WiFi, however, femtocells operate mainly in licensed bands, such that operators are in control of the radio interface. This brings new challenges as well as opportunities for femtocell design; these include sophisticated mobility and interference management, increased reliability, as well as deployment in a plug-and-play manner. Extensive progress in femtocell design has been made in Advanced WiMAX recently, which is associated with the IEEE 802.16m update in 2011. This article gives an overview and update on novel concepts and mechanisms for femtocell support in the network architecture and air interface that have been adopted into the WiMAX Forum network specifications and the IEEE 802.16m specification. [ABSTRACT FROM PUBLISHER]

The author discuss several issues regarding standards required by the IEEE to the networking and communication industries. The authors cited the standards set by the IEEE including the significance of the WiMAX technology in telecommunication industry, the applications and upgradings of new technologies in media, and the importance of cognitive radio technologies in creating the spectrum management.