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Capital expenditures and indoor challenges are two of the main obstacles toward equal access positioning services worldwide. Global Navigation Satellite Systems (GNSS) do not function well indoors and in some challenging outdoor scenarios, such as dense forest canopies or hilly terrains rich in vegetation due, for example, to multipaths and low carrier-to-noise ratios. Terrestrial solutions nowadays can be used to complement GNSS, but they are typically costly to deploy with high coverage and do not offer equal access, for example in some low-revenue countries, in regions forbidding wireless 5G access due to health concerns, or in areas hard to reach with terrestrial infrastructure, such as deep jungle, desert areas with sandy dunes, and deep valleys/deep canyons. As many low Earth orbit (LEO) mega-constellations are emerging and their satellites are significantly closer to Earth than GNSS satellites, solutions based on LEO could complement GNSS. LEO-based communications are expected to be widespread in the next decade, and they will offer a global and easy-to-access infrastructure, with the main costs to the end user coming from the receiver equipment. It is our assumption that future wireless receivers will support the integration of terrestrial and satellite infrastructure, and thus, the LEO-based positioning tasks could be mainly implemented as software add-ons on existing future receivers. Nevertheless, closer proximity to Earth does not automatically mean stronger received signals or acceptable positioning accuracy, especially when the carrier frequencies of the new LEO signals are higher than those in GNSS. Here, we present a feasibility study of LEO-based equal access localization by looking at the current opportunities, benefits, and challenges of LEO megaconstellations used as signals of opportunities. We show that there is an unharnessed potential of future LEO megaconstellations for equal access localization, although several challenges are still to be overcome. [ABSTRACT FROM AUTHOR]

The fifth-generation (5G) network is a fast-growing technology that impacts personal devices for both society and the economy. With the widespread Internet of Things (IoT) devices in such networks, powering and exploring energy to operate them is vital in the 5G era. Therefore, projecting and forecasting how to power IoT devices in the 5G network have already begun, with an aspiration to provide self-powered and green future communication services. Here, we provide a vision for energy harvesting technologies for IoT devices (e.g., emerging wearable and implantable devices employed in healthcare and consumer technologies) that can aid the research line in the 5G era. We propose that various power harvesting and management techniques at the circuit, device, and system levels will be the most crucial segment of IoT devices. Thus, self-power and sustainability should be key features of IoT devices in the 5G network, and ought to be given close attention by electronics and communications communities. To envision this concept, we provide a systematic outline in which prospective power harvesting scenarios of IoT devices in the 5G network are expected. We successively describe vital potential landscapes of 5G and evaluate the energy harvesting and power management requirements. We additionally investigate the challenges beyond energy technologies that could impede the 5G enhancement. [ABSTRACT FROM AUTHOR]

It is often said that the Internet is ubiquitous in our daily lives, but this holds true only for those who can easily access it. In fact, billions of people are still digitally disconnected, as bringing connectivity to certain zones does not make a good business case. The only solution for these unsatisfied potential users is to directly undertake the building of the infrastructure required to obtaining access to the Internet, typically forming groups in order to share the corresponding cost. This article presents a global classification and a summary of the main characteristics of different Alternative Network deployments that have arisen in recent years with an aim to provide Internet services in places where mainstream network deployments do not exist or are not adequate solutions. The "Global Access to the Internet for All" Research Group of the Internet Research Task Force, where all authors actively participate, is interested in documenting these emerging deployments. As an outcome of this work, a classification has converged by consensus, where five criteria have been identified and, based on them, four different types of Alternative Networks have been identified and described with real-world examples. Such a classification is useful for a deeper understanding of the common characteristics behind existing and emerging Alternative Networks. [ABSTRACT FROM PUBLISHER]

Mobile communications are today widespread and contribute to the development of our society. Every day new devices include some means of wireless transmission, which is becoming ubiquitous with the Internet of Things. These systems are standardized by international organizations such as the IEEE, 3GPP, and ETSI, among others. Even though knowledge of wireless standards is key to the understanding of these systems, wireless communications are quite often taught in engineering degrees in a traditional way, without much emphasis on the standardization. Moreover, strong focus is often placed on the theoretical performance analysis rather than on practical implementation aspects. In contrast, most of the current applications make extensive use of mobile data, and the global users' satisfaction is highly correlated with the mobile data throughput. Thus, modern wireless engineers need to have deep insight on the standards that define the mobile transmission systems, and this knowledge is not acquired following the traditional theoretical teaching schemes. In this article, a new learning approach is described. This novel paradigm is based on a new flexible hardware/software platform (FRAMED-SOFT), which is also detailed. Although the article is focused on two wireless standards, GSM and UMTS, the work discussed in this article can easily be extended to other standards of interest, such as LTE and beyond, WiFi, and WiMAX. [ABSTRACT FROM PUBLISHER]

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]

A quality of service framework is a fundamental component of a 4G broadband wireless network for satisfactory service delivery of evolving Internet applications to end users, and managing the network resources. Today's popular mobile Internet applications, such as voice, gaming, streaming, and social networking services, have diverse traffic characteristics and, consequently, different QoS requirements. A rather flexible QoS framework is highly desirable to be future-proof to deliver the incumbent as well as emerging mobile Internet applications. This article highlights QoS frameworks and features of OFDMA-based 4G technologies -- IEEE 802.16e, IEEE 802.16m, and LTE -- to support various applications' QoS requirements. A few advanced QoS features such as new scheduling service (i.e., aGP), quick access, delayed bandwidth request, and priority controlled access in IEEE 802.16m are explained in detail. A brief comparison of the QoS framework of the aforementioned technologies is also provided. [ABSTRACT FROM AUTHOR]

Because mobile devices are equipped with a limited amount of battery power, it is essential to have efficient power management mechanisms in mobile broadband networks such as mobile WiMAX and 3GPP Long Term Evolution that enable always on connectivity. This article presents the state-of-the-art power management methods in next-generation wireless networks with a focus on IEEE 802.16m1 based next-generation WiMAX networks and 3GPP LTE. To minimize and optimize user equipment power consumption, and further to support various services and large amounts of data transmissions, advanced power conservation mechanisms are being developed in IEEE 802.16m and 3GPP. Two advanced power conservation mechanisms, sleep and idle modes, which are enhanced versions of the legacy IEEE 802.16 system's sleep and idle modes, were proposed and adopted in IEEE 802.16m. Similarly, 3GPP LTE adopts a discontinuous reception mechanism for power conservation in RRC_CONNECTED and RRC_IDLE states. Power management techniques in WiMAX and 3GPP LTE provide less control signaling and operational overhead while providing more efficient power saving, and use simpler operation procedures than the existing power management techniques. [ABSTRACT FROM AUTHOR]

The current TD-SCDMA commercialization in China brings about many issues concerning the implementation of TD-SCDMA technology, the market, and its applications. In order to make TD-SCDMA successful, evolution from the current TD-SCDMA standards to International Mobile Telecommunications-Advanced are anticipated. TD-SCDMA standards and technologies will take a home-made evolution path in China, aiming at a smooth migration to the next-generation mobile communication system. This article provides a brief description of the evolution strategies of both the standards and key technologies, in which the evolution is divided into three phases. The state of the art of TD-SCDMA evolution is surveyed, and its technologies and standards in different evolution phases are characterized. Single- and multi-carrier high-speed packet access is specified in the first evolution phase for guaranteeing the high transmission bit rate of packet services. Meanwhile, broadcast services are supported, and the HSPA evolution is also incorporated in this phase. Long Term Evolution is defined in the second evolution phase for approaching similar performance as mobile WiMAX, where channel-reciprocity-based multiple antenna techniques are utilized. The last phase is the revolution to the IMT-Advanced system and becoming one alternative standard in beyond 3G systems, which is based on the evolution of TD-LTE. The difference of standardizations between 3GPP and local standard releases are introduced. Some challenging work and open issues in different evolution phases are discussed as well. [ABSTRACT FROM AUTHOR]

Location-based services have become a requisite feature for most wireless networks. There are two primary use cases: newer applications such as navigation, tracking of assets and personnel, and Points of Interest lookup, and emergency services (e.g., E911), where the user's location is reported to the public safety answering point from which emergency responders are dispatched. Within this space of applications, location accuracies ranging from less than 5 m to hundreds of meters may be acceptable, depending on the specific use case. This article presents the end-to-end framework for location-based services in WiMAX technology, including both the mobile managed location approach with minimal network support as well as different network managed location solutions with assistance from mobile stations. [ABSTRACT FROM AUTHOR]

Multicast and broadcast services in WiMAX are downlink point-to-multipoint access services optimized for transmission of a common set of multimedia data packets to a group of users. This capability enables low-cost delivery of large volumes of popular contents (e.g., for video/audio streaming and file sharing) in a mobile network. The MCBCS framework in WiMAX allows multicast/broadcast of data in a radio channel that is time shared with unicast services. In a single-frequency network, where MCBCS transmissions are synchronized or coordinated across BSs in the designated service area, the mobile stations can use macro-space diversity to improve achievable data rates and also maintain service continuity and power saving across cells with minimal interaction with the network. [ABSTRACT FROM AUTHOR]

Femtocells are low-power base stations operating in licensed spectrum, which are typically installed indoors in a house, small office, or home office by end users to provide exclusive or preferential access to a designated group of users as configured by the femtocell subscriber and/or the access provider. Femtocells have gained a lot of attention recently due to their advantages in terms of infrastructure cost saving and improved user experience in indoor environments. Several standards bodies, such as 3GPP, WiMAX Forum, and IEEE 802.16, have started to develop standard solutions to enable and optimize femtocells operation. However, there are some technical challenges to the success of femtocell technologies that need to be overcome before they can be deployed on large scales. This article presents an overview of WiMAX femtocell requirements, deployment models, and solutions in the near and long terms. [ABSTRACT FROM AUTHOR]

Shrinking cell sizes, primarily a result of keeping up with the increasing demand for higher data rates, are stretching thin the notion of our traditional cellular system architecture. More and more base stations are serving smaller and smaller areas (cells) which in effect is driving up deployment costs. The option of deploying relay stations is increasingly beginning to look like a solution to the problem of providing a cost-effective way to extend the coverage and capacity in a cellular network. A relay station can be used to extend the point-to-multipoint link between the base station and mobile stations. Relay stations connect to the base stations without wires and are expected to be deployed to cover smaller geographic areas. Primarily the deployment costs but also the equipment costs are expected to be substantially lower than those of base stations. In this article we first introduce the relay station and discuss the place it is likely to carve out for itself in the traditional cellular architecture. We highlight the important economic and performance benefits relay stations could potentially offer, and outline a few scenarios where relays are likely to be deployed in the beginning. The multihop relay standard developed by the IEEE 802.16 working group is then used as a basis to provide an overview of the relay-enhanced cellular architecture and the key choices that can be made in developing relay support within a cellular system - a precursor to what can be expected in later releases of the Mobile WiMAX system. Finally, we discuss some future directions in the development of relay systems. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Multiple wireless interfaces (GSM, Wi-Fi, Bluetooth, FM, and GPS receiver, etc.) are being integrated into mobile devices. WiMAX, an IEEE802.16-based wireless access technology recently included in the IMT-2000 set of standards by ITU-R, will soon be added. Obstacles remain to operating these collocated radios concurrently, including interference and hardware conflicts due to congested spectrum allocation and component sharing with radio integration. In this article we provide a tutorial overview of today's solutions to enable concurrent operation of multiple collocated radios in IEEE 802.16- based wireless networks with a focus on perceived concurrency: a MAC coordination approach. We then present three general design principles - predictability, compressibility, and flexible scheduling - with examples of standard features. It is anticipated that the next-generation IEEE 802.16 standards will be enhanced with new features such as explicit service setup, asynchronous operation, and collocated coexistence-aware scheduling. [ABSTRACT FROM AUTHOR]

Mobile satellite services are attracting renewed attention stemming from the FCC ancillary terrestrial component ruling that allows satellite spectrum to be used for integrated terrestrial services in the footprint of the satellite. This attention is focused on the development of dual-mode satellite-terrestrial devices to facilitate hybrid satellite-terrestrial networks intended by the ATC order. The satellite component in these dual-mode devices is best adapted from the air interface chosen for the ATC to optimize form factor, especially for small hand-held devices, mobility management, power efficiency, and a common core network functionality. With the advent of WiMAX as a viable 4G technology, satellite adaptation of WiMAX has been considered for the satellite services coupled with WiMAX ATC. The main considerations for satellite adaptation of WiMAX, relative to its terrestrial counterpart, are reduced link margin and longer transmission delays - both absolute delay from the center of a spot beam to the satellite and differential delay between the beam edge and the beam center to the satellite. These considerations suggest adaptation of the sub-channelization schemes, the frame synchronization methods, and the ranging process in WiMAX to make it operable over satellite, while keeping the general framework of the WiMAX protocol stack intact, thereby facilitating the incorporation of S-WiMAX into a common baseband processor with terrestrial WiMAX; this allows S-WiMAX to be added to terrestrial WiMAX devices with minimal cost and form-factor impact. Methods for these adaptations are considered here. [ABSTRACT FROM AUTHOR]

The growing demand for wireless Internet services is accelerating the evolution of wireless networks toward all-IP architecture, and the mobile WiMAX network is a prominent example. Although currently deployed mobile WiMAX networks use hierarchical architecture, flat architecture is feasible and specified as a design alternative in the mobile WiMAX standard. In flat architecture the functionalities of the ASN-GW and BS are consolidated into a single element. In this article we first discuss the benefits and challenges of flat architecture mobile WiMAX networks. We then present a scheme to deal with the seamless mobility issue, which is one of the key challenges of the flat architecture. The proposed scheme combines two standard IP-mobility protocols, Proxy Mobile IP and Fast Mobile IP, and customizes them for IEEE 802.16e-based mobile WiMAX networks. This provides interoperability with existing mobile WiMAX networks. We demonstrate the viability of the proposed scheme through simulations using NS-2. [ABSTRACT FROM AUTHOR]

The mobile WiMAX system is based on IEEE 802.16e, which defines radio interface supporting several classes of Internet Protocol applications and services. While the mobile WiMAX system is being deployed, IEEE 802.16m TO is developing an amendment to the IEEE 802.16e to greatly improve the system performance, and it is focusing not only on the PHY and MAC performance but also on a level of end-to-end performance improvement that includes the scope of the net- work and application to embrace the strong market request and interest. To evaluate the mobile WiMAX system capacity and performance, all the aspects of performance evaluation - from air link to application - are required. For the network and application-level capacity and performance analysis, we first provide an overview of mobile WiMAX systems, especially of the OFDMA/TDD systems of IEEE 802.16e and then describe subscriber and application profiles that include traffic-mix ratio, data-session attempts for applications, diurnal-application traffic distribution, and the application-traffic model. Afterward, the simulation results of network-traffic characteristics and demand estimation are provided. Finally, in the last section, we provide simulation results of end-to-end application performance evaluation using the examples of VoIP and a TCP/IP performance-enhancement method that can be implemented in the mobile WiMAX MAC or MAC/IP cross layer. [ABSTRACT FROM AUTHOR]

WiMAX, a fourth-generation wireless-access technology, has made significant progress both in the standard forums and with wireless network carriers. To ensure service continuity to a legacy end user, it is important for a WiMAX mobile device to interwork with existing third-generation access networks before it is uniquely and ubiquitously deployed. This article addresses this issue and shows how interworking can be achieved with EVDO wireless-access technology, using mobile IP in a dual mode terminal. We present a network architecture solution and detailed call flows. [ABSTRACT FROM AUTHOR]

The growing demand for mobile Internet and wireless multimedia applications has motivated the development of broadband wireless-access technologies in recent years. Mobile WiMAX has enabled convergence of mobile and fixed broadband networks through a common wide-area radio-access technology and flexible network architecture. Since January 2007, the IEEE 802.16 Working Group has been developing a new amendment of the IEEE 802.16 standard (i.e., IEEE 802.16m) as an advanced air interface to meet the requirements of ITU-R/IMT-advanced for 4G systems, as well as for the next-generation mobile network operators. Depending on the available bandwidth and multi-antenna mode, the next-generation mobile WiMAX will be capable of over-the-air data-transfer rates in excess of 1 Gb/s and of supporting a wide range of high-quality and high-capacity IP-based services and applications while maintaining full backward compatibility with the existing mobile WiMAX systems to preserve investments and continuing to support first-generation products. This tutorial describes the prominent technical features of IEEE 802.16m and the potential for successful deployment of the next generation of mobile WiMAX in 2011+. [ABSTRACT FROM AUTHOR]

Phases I and II of the WINNER project contributed to the development, integration, and assessment of new mobile network techniques from 2004 to 2007. Some of these techniques are now in the 3GPP LTE and IEEE 802.16 (WiMAX) standards, while others are under consideration for LTE-Advanced and 802.16m. The WINNER+ project continues this forward-looking work for IMT-advanced technologies and their evolution, with a particular focus on 3GPP LTE-Advanced. This article provides an overview of the WINNER system concept and several of its key innovative components. [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]

This article provides an up-to-date survey of hybrid fiber-wireless (FiWi) access networks that leverage on the respective strengths of optical and wireless technologies and converge them seamlessly. FiWi networks become rapidly mature and give rise to new powerful access network solutions and paradigms. The survey first overviews the state of the art, enabling technologies, and future developments of wireless and optical access networks, respectively, paying particular attention to wireless mesh networks and fiber to the home networks. After briefly reviewing some generic integration approaches of EPON and WiMAX networks, several recently proposed FiWi architectures based on different optical network topologies and WiFi technology are described. Finally, technological challenges toward the realization and commercial adoption of future FiWi access networks are identified. [ABSTRACT FROM AUTHOR]

A key aspect of the 3GPP system architecture evolution is the specification of an evolved packet core that supports multiple access networks. The EPC enables operators to deploy and operate one common packet core network for 3GPP radio accesses (E-UTRAN, UTRAN, and GERAN), as well as other wireless and wireline access networks (e.g., eHRPD, WLAN, WIMAX, and DSL/Cable), providing the operator with a common set of services and capabilities across the networks. A key requirement of the EPC is to provide seamless mobility at the IP layer as the user moves within and between accesses. This article provides an overview of the EPC specifications that use a network-based mobility mechanism based on Proxy Mobile IPv6 to enable mobility between access networks. An important facet of providing seamless mobility for a user's sessions across technologies is to ensure that quality of service is maintained as the user moves between accesses. An overview of the "off-path" QoS model to supplement PMIPv6 is also provided. [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]

Ethernet services represent a steadily growing portion of the fixed telecommunication market. To enable the provisioning of Ethernet services over IEEE 802.16e, the Mobile WiMAX network artchitecture supports transparent Ethernet transport as an optional extension to the IP services architecture. Ethernet support is tightly aligned to the IP services network model, and leverages many data path and control plane functions from its IP sibling to keep the implementation and operation overhead low for the Ethernet extension. Mobile WiMAX provides IP services as well as Ethernet services over the same mobile access network. The intrinsic mobility support may create new deployment opportunities for Ethernet services. Initially, the Ethernet extension may be mostly used to realize wireless access for DSL networks based on the same network interfaces defined for the wired Ethernet-based DSL aggregation. [ABSTRACT FROM AUTHOR]

As the wireless industry makes its way to the next generation of mobile systems, it is important to engineer solutions that enable seamless integration of emerging 4G access technologies within the currently deployed and/or evolved 2G/30 infrastructures. In this article we address a specific case of such a seamless integration, that of mobile WiMAX in evolved 3GPP networks. In this context we investigate the architecture and the key procedures that enable this integration, and we also introduce a novel handover mechanism that enables seamless mobility between mobile WiMAX and legacy 3GPP access, such as UTRAN or GERAN. The core characteristic of this novel handover mechanism is that mobile terminals do not need to support simultaneous transmission on both WiMAX and 3GPP accesses; therefore, it mitigates the RF coexistence issues that exist otherwise and improves handover performance. In addition, we provide a brief overview of mobile WiMAX and the evolved 3GPP network technologies, and we set the appropriate background material before presenting our proposed handover mechanism. Our main conclusion is that integrating mobile WiMAX in evolved 3GPP networks is a compelling approach for providing wireless broad- band services, and mobility across WiMAX and 3GPP access can become seamless and efficient with no need for mobile terminals to support simultaneous transmission on both types of access. [ABSTRACT FROM AUTHOR]

This article highlights WiMAX network requirements and functionality for integration with 3GPP Rel 7 IMS/PCC architectures. [ABSTRACT FROM AUTHOR]

Femtocells are viewed as a promising option for mobile operators to improve coverage and provide high-data-rate services in a cost-effective manner. The idea is to overlay low-power and low-cost base station devices, Femto-APs, on the existing cellular network, where each Femto-AP provides high-speed wireless connection to subscribers within a small range. In particular, Femto-APs can be used to serve indoor users, resulting in a powerful solution for ubiquitous indoor and outdoor coverage, using a single access technology such as WiMAX. In this article we consider a WiMAX network deploying both macro BSs and Femto-APs, where it is assumed that Femto-APs have wired backhaul such as cable or DSL and operate on the same frequency band as macro BSs. Simulation results show that significant areal capacity (throughput per unit area) gain can be achieved via intense spatial reuse of the wireless spectrum. In addition, Femto-APs improve indoor coverage, where the macro BS signal may be weak. Motivated by the gains in capacity and coverage offered by femtocells, we review the state of the art of this "infant" technology, including use cases and network deployment scenarios, technical challenges that need to be addressed, and current standardization and industry activity. [ABSTRACT FROM AUTHOR]

Efficient support of voice traffic has always been one of the key metrics for evaluating and selecting radio access technologies. Even for next-generation broadband wireless technologies primarily focused on the mobile Internet, special handling of VoIP traffic in the physical and MAC layers is required to maximize voice capacity. While Mobile WiMAX Release 1.0 and 802.16e have all the key features necessary to support mobile VoIP traffic, special attention is given in Mobile WiMAX Release 1.5 and 802.16REV2 to further optimizing VoIP capacity through reduction in the MAC layer overhead associated with signaling messages. This article focuses on features and solutions used in Mobile WiMAX and the 802.16 standard to support voice traffic and the expected performance in Release 1.0/802.16e-2005, as well as gains from optimization concepts such as persistent allocation added in Release 1.5/802.16REV2. In each case, MAP overhead reduction and the projected improvements in VoIP capacity are presented using typical industry accepted models and assumptions. The results show about 15 percent increase in bidirectional VoIP capacity. [ABSTRACT FROM AUTHOR]

Mobile WiMAX was successfully adopted by ITU as one of the IMT-2000 technologies in November 2007. Since then mobile WiMAX (a.k.a. IP-OFDMA) has officially become a major global cellular wireless standard along with 3GPP UMTS/HSPA and 3GPP2 CDMA/EVDO. Mobile WiMAX is an OFDM-based technology available for deployment today, and new WIMAX devices come to market at much reduced cost than that of current 3G solutions. Currently over 260 service providers are deploying fixed, portable and mobile WiMAX networks in 110 countries. This article provides an overview of the mobile WiMAX system and its performance under various configurations, channel conditions, and types of data traffic. Furthermore, the article provides an overview of mobile WiMAX evolution. [ABSTRACT FROM AUTHOR]

Mobile WiMAX is a fast growing broadband access technology that enables low-cost mobile Internet applications, and realizes the convergence of mobile and fixed broadband access in a single air interface and network architecture. Mobile WiMAX combines OFDMA and advanced MIMO schemes along with flexible bandwidth and fast link adaptation, creating a highly efficient air interface that exceeds the capacity of existing and evolving 3G radio access networks. WiMAX networks, built on all-IP network architecture for plug and play network deployments, can support a mix of different usage and service models. While some consider mobile WiMAX as a candidate for the fourth generation of mobile networks, others view it as the first generation of mobile Internet technologies emerging from a wider ecosystem targeting to extend the success of WiFi over wide area networks supporting mobility. This article provides a high-level overview of mobile WiMAX technology and its evolution roadmap from both radio and network perspectives. [ABSTRACT FROM AUTHOR]

This article sets out the opportunity and the role of Ethernet within largescale carrier net works. Carrier Ethernet can greatly reduce the consequences of the complexity associated with the large scale and broad scope of carriers' net works by being a costeffective replacement for SONET/SDH. However, in order to achieve this, carrier Ethernet needs to provide the equivalent level of transparency, simplicity, and reliability currently achieved by SONET/SDH, and the emerging IEEE Ethernet standards for PBB and PBBTE are well suited to this role. These technologies are an ideal complement to IP/MPLS for which they can provide highly costeffective managed and guaranteed bit pipes. [ABSTRACT FROM AUTHOR]

The surest way to increase the system capacity of a wireless link is by getting the transmitter and receiver closer to each other, which creates the dual benefits of higher-quality links and more spatial reuse. In a network with nomadic users, this inevitably involves deploying more infrastructure, typically in the form of microcells, hot spots, distributed antennas, or relays. A less expensive alternative is the recent concept of femtocells also called home base stations which are data access points installed by home users to get better indoor voice and data coverage. In this article we overview the technical and business arguments for femtocells and describe the state of the art on each front. We also describe the technical challenges facing femtocell networks and give some preliminary ideas for how to overcome them. [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]

Cognitive radio techniques are being applied to many different communications systems. They hold promise for increasing utilization of radio frequencies that are underutilized today, allowing for improved commercial data services, and allowing for new emergency and military communications services [1]. For example, these techniques are being considered by the U.S. FCC for communications services in unlicensed VHF and UHF TV bands. Although traditionally these techniques are closely associated with software- defined radios, many standards such as WiFi (IEEE 802.11), Zigbee (IEEE 802.15.4), and WiMAX (IEEE 802.16) already include some degree of CR technology today. Further advances are occurring rapidly. IEEE 802.22 will be the first cognitive radio-based international standard with tangible frequency bands for its operation. Standardization is at the core of the current and future success of cognitive radio. Industry stakeholders are participating in international standards activities governing the use of cognitive radio techniques for dynamic spectrum access and coexistence, next-generation radio and spectrum management, and interoperability in infrastructure-less wireless networks. This article provides a review of standardization activities for cognitive radio technologies and comments on prospects and issues for future standardization. [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]

In several countries manufacturers, operators, and public authorities look at WiMAX system as a viable technology to fill the "digital divide," providing broadband services mainly in suburban and rural areas, but also in densely populated areas. Nevertheless, as a standalone system it will never offer global services, and to complement its capabilities, the utilization of broadband space-based access shared among users represents a scalable and cost-effective solution to offer wider area coverage, improved performance in terms of QoS, service continuity in case of terrestrial network failure, and long-range user mobility. Integration between WiMAX and a space-based infrastructure, composed of a combination of satellites and high altitude platforms, can be pursued in several ways. The simplest solution is based on connecting a WiMAX network by means of a terrestrial network terminating at a hub station connected to the space infrastructure. A more flexible solution should allow the WiMAX subscriber station or base station to directly access the space infrastructure. This article addresses the identification of suitable scenarios and a feasibility analysis presenting link budget results related to a subset of the identified solutions. [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]

The advances in broadband Internet access and scalable video technologies have made it possible for Internet Protocol television (IPTV) to become the next killer application for modern Internet carriers in metropolitan areas. With the recent release of IEEE 802.16d/e (worldwide interoperability for microwave access or WiMAX), broadband wireless access (BWA) is envisioned to further extend IPTV services to a new application scenario with wireless and mobility dimensions. It is a very strategic but challenging leverage for a carrier to glimpse the potential of IPTV by using WiMAX as the access network. Challenges are posed for IPTV over WiMAX due to multicasting under a diversity of fading conditions, A cross-layer design frame-work based on a novel two-level superposition coded multicasting (SCM) scheme is introduced. Simulation results show that much improved video quality is achievable with our approach. [ABSTRACT FROM AUTHOR]

Multimedia stream service provided by broadband wireless networks has emerged as an important technology and has attracted much attention recently. An all-IP network architecture with reliable high-throughput air interface makes orthogonal frequency division multiplexing access (OFDMA)-based mobile worldwide interoperability for microwave access (mobile WiMAX) a viable technology for wireless multimedia services, such as voice over IP (VoIP), mobile TV, and so on. One of the main features in a WiMAX MAC layer is that it can provide differentiated services among different traffic categories with individual QoS requirements. In this article, we first give an overview of the key aspects of WiMAX and describe multimedia broadcast multicast service (MBMS) architecture of the 3GPP. Then, we propose a multicast and broadcast service (MBS) architecture for WiMAX that is based on MBMS. Moreover, we enhance the MBS architecture for mobile WiMAX to overcome the shortcoming of limited video broadcast performance over the baseline MBS model. We also give examples to demonstrate that the proposed architecture can support better mobility and offer higher power efficiency. [ABSTRACT FROM AUTHOR]

In this article we propose a cross-layer design model for multimedia multicast/broadcast services to efficiently support the diverse quality of service requirements over mobile wireless networks. Specifically, we aim at achieving high system throughput for multimedia multicast/broadcast while satisfying QoS requirements from different protocol layers. First, at the physical layer, we propose a dynamic rate adaptation scheme to optimize the average throughput subject to the loss rate QoS constraint specified from the upper-layer protocol users. We investigate scenarios with either independent and identically distributed (i.i.d.) or non-i,i.d. fading channels connecting to different multicast receivers. Then, applying the effective capacity theory at the data link layer, we study the impact of the delay QoS requirement (i.e., QoS exponent) on the multimedia data rate of mobile multicast/broadcast that our proposed scheme can support. Also presented are simulation results which show the trade-off among different QoS metrics and the performance superiority of our proposed scheme as compared to the other existing schemes. [ABSTRACT FROM AUTHOR]

In this article we propose a unified radio net- work architecture, broadband wireless multimedia (BWM), which integrates broadcasting service and broadband wireless access service at both the application and physical layers. A simple, flexible, and comprehensive radio resource management framework is developed for the unified radio network. It is shown that the proposed radio network architecture has many advantages over existing ones. In addition, the new architecture is currently being considered in China for the system level design. [ABSTRACT FROM AUTHOR]

EPON and WiMAX are two promising broadband access technologies for new-generation wired and wireless access. Their complementaiy features motivate interest in using EPON as a backhaul to connect multiple dispersed WiMAX base stations. In this article we propose four broadband access architectures to integrate EPON and WiMAX technologies. The integrated architectures can take advantage of the band-width benefit of fiber communications, and the mobile and non-line-of-sight features of wireless communications. Based on these integrated architectures, we elaborate on related control and operation issues to address the benefits gained by this integration. Integration of EPON and WiMAX enables fixed mobile convergence, and is expected to significantly reduce overall design and operational costs for new-generation broadband access networks. [ABSTRACT FROM AUTHOR]

Cognitive radios have been advanced as a technology for the opportunistic use of underutilized spectrum wherein secondary devices sense the presence of the primary user and use the spectrum only if it is deemed empty. Spectral cognition of this form can also be used by regulators to facilitate the dynamic coexistence of different service types. An example of this is the operation of ultra-wideband devices in WiMAX bands: UWB devices must detect and avoid WiMAX devices in certain regulatory domains. In this article we start by discussing various options for detection and avoidance. We then describe the obstacles faced in achieving robust detection and avoidance with an on-chip implementation of basic DAA functionality. Finally, we present measurement results for operation of a single UWB device with a WiMAX system. This interaction also highlights the problem of dealing with listen before speak primaries where secondary transmission could interfere by blocking the primary's access to the medium. [ABSTRACT FROM AUTHOR]

A time-limited lease is a set of rights that expires after a specified duration. We analyze ways to use leases to facilitate innovation in radio devices and wireless communication. In our vision, manufacturers include in their devices a simple, secure subsystem that contains a clock and disables specific transmit capabilities if no extension message is received by the end of the lease period. When devices provide this support, regulators may use certification leases rather than permanent grants to accelerate deployment of innovative radios. Spectrum rights holders may use leases to reduce risk in secondary spectrum market transactions. Firms collaborating in innovative wireless service business models can better retain control of their respective rights. We examine both the technical and policy issues associated with leases. [ABSTRACT FROM AUTHOR]

The 3GPP specifies the IP multimedia subsystem (IMS) to provide several kinds of multimedia services in UMTS Release 5 and later releases. Interworking at the service layer between 3GPP and Wimax networks requires interworking between IMS functionality. By studying several interconnection scenarios and the main functionality of IMS, this article analyzes how the interworking of 3GPP and Wimax networks can be performed to support different levels of service interconnection. Special attention is paid to the interconnection at the session negotiation level, using SIP (the base protocol of the IMS), COPS/Go, and Diameter protocols/interface to provide session negotiation with QoS and AAA (authentication authorization accounting) support. [ABSTRACT FROM AUTHOR]

In this article we propose cross-layer design frameworks for 802.16e OFDMA systems that are compatible with WiBro based on various kinds of cross-layer protocols for performance improvement: a cross-layer adaptation frame- work and a design example of primitives for cross-layer operation between its MAC and PRY layers. In addition, we provide a simulation framework for cross-layer analysis between the MAC and PRY layers in 802.16e systems. Through this cross-layer simulator, we show that average cell throughput can be improved by 25-60 percent by applying careful cross-layer adaptation schemes. [ABSTRACT FROM AUTHOR]