As of today, orthogonal frequency division multiplexing (OFDM) has been the dominant technology for broadband multicarrier communications. However, in certain applications such as cognitive radios and uplink of multiuser multicarrier systems, where a subset of subcarriers is allocated to each user, OFDM may be an undesirable solution. In this article, we address the shortcomings of OFDM in these and other applications and show that filter bank multicarrier (FBMC) could be a more effective solution. Although FBMC methods have been studied by a number of researchers, and some even before the invention of OFDM, only recently has FBMC been seriously considered by a few standard committees.

OFDM Versus Filter Bank Multicarrier

This paper considers the multiuser power control problem in a frequency-selective interference channel. The interference channel is modeled as a noncooperative game, and the existence and uniqueness of a Nash equilibrium are established for a two-player version of the game. An iterative water-filling algorithm is proposed to efficiently reach the Nash equilibrium. The iterative water-filling algorithm can be implemented distributively without the need for centralized control. It implicitly takes into account the loop transfer functions and cross couplings, and it reaches a competitively optimal power allocation by offering an opportunity for loops to negotiate the best use of power and frequency with each other. When applied to the upstream power backoff problem in very-high bit-rate digital subscriber lines and the downstream spectral compatibility problem in asymmetric digital subscriber lines, the new power control algorithm is found to give a significant performance improvement when compared with existing methods.

Distributed multiuser power control for digital subscriber lines

From the Publisher:
Multi-carrier modulation, in particular orthogonal frequency division multiplexing (OFDM), has been successfully applied to a wide variety of digital communications applications for several years. Although OFDM has been chosen as the physical layer standard for a diversity of important systems, the theory, algorithms, and implementation techniques remain subjects of current interest. 

This book is intended to be a concise summary of the present state of the art of the theory and practice of OFDM technology. This book offers a unified presentation of OFDM theory and high speed and wireless applications. In particular, ADSL, wireless LAN, and digital broadcasting technologies are explained. 

It is hoped that this book will prove valuable both to developers of such systems, and to researchers and graduate students involved in analysis of digital communications, and will remain a valuable summary of the technology, providing an understanding of new advances as well as the present core technology.

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Multi-Carrier Digital Communications: Theory and Applications of OFDM

The mutual information of independent parallel Gaussian-noise channels is maximized, under an average power constraint, by independent Gaussian inputs whose power is allocated according to the waterfilling policy. In practice, discrete signaling constellations with limited peak-to-average ratios (m-PSK, m-QAM, etc.) are used in lieu of the ideal Gaussian signals. This paper gives the power allocation policy that maximizes the mutual information over parallel channels with arbitrary input distributions. Such policy admits a graphical interpretation, referred to as mercury/waterfilling, which generalizes the waterfilling solution and allows retaining some of its intuition. The relationship between mutual information of Gaussian channels and nonlinear minimum mean-square error (MMSE) proves key to solving the power allocation problem.

/pdf/optimum-power-allocation-for-parallel-gaussian-channels-with-6fj5ovds2s.pdf

Optimum power allocation for parallel Gaussian channels with arbitrary input distributions

This paper proposes efficient rate and power allocation algorithms for OFDMA downlink systems where each tone is taken by at most one user. Weighted sum rate maximization (WSRmax) and weighted sum power minimization (WSPmin) problems are considered. Since these resource allocation problems are non-convex, complexity of finding the optimal solutions is prohibitively high. This paper employs the Lagrange dual decomposition method to efficiently solve both optimization problems. Because of their non-convex nature, there is no guarantee for the solution obtained by the dual decomposition method to be optimal. However, it is shown that with practical number of tones, the duality gap is virtually zero and the optimal solutions can be efficiently obtained.

Optimal Resource Allocation for OFDMA Downlink Systems

1. DSL Fundamentals. Alternatives to DSLs: Fiber, Wireless, and Coax. Worldwide Extent. Voice-Band Modems and DSLs. Transmission Modes. DSL Terminology. Rate Versus Reach. Crosstalk. Enabling and Disabling Forces. Applications. Evolution of Digital Transmission. 2. Types of DSLs. DSL Design Margin. DSL Precursors. Basic Rate ISDN. HDSL. ADSL. VDSL. 3. Twisted-Pair Transmission. Twisted-Wire-Pair Origins. Telephone Network and Loop Plant Characteristics. Line Powering. Sealing Current. Transmission Line Characterization. Noises. Spectral Compatibility. More Two-Port Networks. Three-Port Networks for DSLs. References. 4. Comparison with Other Media. Fiber-to-the-Home. Coax and Hybrid Fiber Coax. Wireless Alternatives. Satellite Services. References. 5. Transmission Duplexing Methods. Four-Wire Duplexing. Echo Cancellation. Time-Division Duplexing. Frequency-Division Multiplexing. References. 6. Basic Digital Transmission Methods. Basic Modulation and Demodulation. Baseband Codes. Passband Codes. References. 7. Loop Impairments, Solutions, and DMT. Intersymbol Interference. Multichannel Line Codes. Trellis Coding. Error Control. References. 8. Initialization, Timing and Performance. Initialization Methods. Adaptation of Receiver and Transmitter. Measurement of Performance. Timing Recovery Methods. References. 9. Operations, Administration Maintenance, and Provisioning. OAM&P Features. Loop Qualification. 10. DSL in the Context of the ISO Reference Model. The ISO Model. Theory and Reality. The Internet Protocol Suite. ATM in the Seven-Layer Model. 11. ADSL: The Bit Pump. ADSL System Reference Model. ATU-C Reference Model. ATU-R Reference Model. Specific Configurations to Support ATM. Framing. Operations and Maintenance. Initialization. Reference. 12. ATM Transmission Convergence on ADSL. Functions of ATM Transmission Convergence. Transmission Convergence in an ADSL Environment. Reference. 13. Frame-Based Protocols over ADSL. PPP over a Frame-Based ADSL. FUNI over ADSL. Reference. 14. ADSL in the Context of End-to-End Systems. An Overview of a Generic DSL Architecture. Potential ADSL Services and the Service Requirements. Specific Architectures for Deploying ADSL in Different Business Models. Several ADSL Architectures. References. 15. Network Architecture and Regulation. Private Line. Circuit Switched. Packet Switched. ATM. Remote Terminal. Competitive Data Access Alternatives. Regulation. 16. Standards. ITU. Committee T1. ETSI. ADSL Forum. ATM Forum. DAVIC. IETF. EIA/TIA. IEEE. The Value of Standards and Participation in Their Development. Standards Process. Appendix A: Glossary. Appendix B: Selected Standards and Specifications. Appendix C: Selected T1E1.4 Contributions and ADSL Forum Technical Reports (found on website). Index.

Understanding Digital Subscriber Line Technology

Cutting-edge xDSL: technology, standards, architecture, regulation, and its application. The state of the art in DSL technology, standards, and architecture ADSL, HDSL2, SHDSL, VDSL, line unbundling, spectrum management, and more Voice over DSL and video-on-demand: technical progress and its impact on services DSL in the home: automating deployment, enhancing security, maximizing revenue Improved coding techniques, multi-user detection, and other new advancesDigital Subscriber Lines (DSLs) have transformed millions of ordinary phone lines into broadband arteries that link homes and businesses to the Internet at megabit speeds. DSL Advances brings together the state of the art in DSL technology and architecture for every technical professional and manager. The authors of the classic Understanding Digital Subscriber Line Technology review the key challenges service providers and equipment manufacturers face now, preview tomorrow's most important standards and technical enhancements, and offer new insights into today's regulatory and business environment. Coverage includes: HDSL2 and SHDSL: The next generation of symmetric DSL technology Recent developments in ADSL and standards for line unbundling Spectrum management standards: "traffic cops" for crosstalk management Voice over DSL and video-on-demand: technical progress that enhances the business case DSL networked homes: wired/wireless LANs, shared phone and AC wiring?including both centralized splitters and distributed in-line filter premises wiring Streamlining deployment: CPE auto-configuration and flow-through service provisioning Security risks and essential safeguards for vendors, service providers, and users Future directions, including advanced coding techniques and multi-user detection

DSL Advances

Control-plane functions are migrating from dedicated network equipment into software running on commodity hardware. The Software- Defined Access Network (SDAN) concept introduced here extends the benefits of Software- Defined Networking and Network Function Virtualization (NFV) into broadband access. In a SDAN, access-network control and management functions for broadband access are virtualized, to streamline operations, speed services creation, and enhance broadband customer satisfaction, particularly in multi-operator environments. This article examines industry drivers, identifies software- definable control and management functions for broadband access, and presents some specific usage scenarios for the SDAN.

Software-defined access networks

Digital subscriber lines

Operator-controlled implementations of user preferences are provided when feasible. User preference data is obtained by the operator and compared to operational characteristics and parameters of a communication system, such as a DSL system, to determine whether one or more of the user preferences can be implemented in the communication system. When implementation of a user preference would violate operational rules of the system, or where implementation would adversely affect system operation, the preference need not be implemented. However, when a user preference can be implemented in the system without causing problems, the operator can implement (or permit another party to implement) the user preference to effect the user's desires. The user preference data can be obtained directly from users (for example, by surveys and other direct user feedback) or can be obtained indirectly (for example, by constructing a Hidden Markov Model that shows user preferences). The operator may collect the user preference data from a user set (for example, a single user or a plurality of users). The user preference data can be compared to 2 or more performance metrics that can be adjusted, to the extent feasible, to implement the user preference data.

Peter J. Silverman

Papers

Understanding Digital Subscriber Line Technology

DSL Advances

Software-defined access networks

Digital subscriber lines

User-preference-based dsl system