Testing and interoperability of 10GBASE-LRM optical interfaces [Topics in Optical Communications]

This article will discuss some of the issues in testing 10GBASE-LRM optical interfaces over multimode fiber, and will outline a methodology for doing so. The article will also describe test results from a recent multivendor interoperability test demonstrating the feasibility and robustness of the LRM interface     

Sub-Wavelength Solutions for Next-Generation Optical Networks [Topics in Optical Communications]

The recent trend in optical networks is switching packets directly in the optical domain. The aim is to benefit from both packet flexibility and optical transparency. In this article, we review current optical architectures that try to reconcile these two requirements. We discuss the challenges encountered in these new architectures and their respective niches. To meet the requirements of next-generation high-speed optical networks, we also propose a new solution based on the distribution of the aggregation process in the network. The feasibility of this scheme and the benefit that it provides over existing solutions are analyzed in this article.     

An introduction to PON technologies [Topics in Optical Communications]

Passive optical networks are the most important class of fiber access systems in the world today. This article first reviews the reasons why the PON as a general architecture is so important. We then outline in some depth the technologies used to implement this architecture, including the G-PON and E-PON systems being deployed today, and the advanced PON systems that provide the evolution path to ever higher bandwidths     

IP over optical cross-connect architectures [Topics in Optical Communications]

IP over optical network architectures have been extensively discussed within the research literature over the past few years. However, although signaling protocols between IP routers and optical cross-connect networks have been standardized, large IP backbones are not typically deployed over optical cross-connect networks with automatic reconfigurability features, such as automatic restoration or dynamic establishment of new IP links. One of the most important criteria in determining whether an IP backbone should be carried over such an optical cross-connect network is economic viability. In this article we analyze and explore four architectures for a typical large ISP backbone. In contrast with some other published claims, our results suggest it is more economically attractive to bypass an intermediate cross-connect network, given current equipment and IP backbone network design requirements. However, for ISPs who also provide a large volume of private line services, we propose an integrated architecture for IP over optical cross-connect networks that may provide an attractive alternative for providing rapid and cost-effective restoration from network failures     

Secure Optical Burst Switching: Framework and Research Directions [Topics in Optical Communications]

Optical burst switching has been positioned as a viable means of implementing optical communication efficiently. This article identifies potential threats to security in OBS networks. To alleviate the security threats in OBS networks, a secure Optical Burst Switching (S-OBS) framework is proposed. The S-OBS framework provides two levels of security measures: authentication of burst headers and confidentiality of data bursts. Candidate solutions in each category are examined, and research directions are presented.     

Translucent optical networks: the way forward [Topics in Optical Communications]

The transmission reach of signals in optical transmission systems is limited. To go beyond these transparent reach limits, signal regeneration is necessary to re-amplify, reshape, and retime the optical signals. Translucent optical networks are a type of optical transport network specifically devised to address such a concern by allowing for sparse but strategic signal regeneration in the network. Translucent optical networks seek a graceful balance between network design cost and service provisioning performance, and can achieve performance comparable to that of an all-electronic switching network, but requiring far fewer signal regenerators. Despite massive progress, there are many outstanding issues regarding the implementation of translucent networks planning and operation. This article reviews a range of translucent optical networks and discusses various research issues, particularly involving network planning, lightpath routing and wavelength assignment, and network survivability. We also suggest other potential research topics such as traffic grooming, fault detection, and multicasting for translucent networks     

OCDMA and Optical Coding: Principles, Applications, and Challenges [Topics in Optical Communications]

We survey the current trends in OCDMA and optical coding through their applications. Although a prerequisite for OCDMA, optical coding distinguishes itself from OCDMA through major applications where codes are not applied to data and carry network-level information other than user identity. After introducing the principles of coding, we discuss OCDMA and its applications, particularly OCDMA PON. Optical coding and its applications are then reviewed.     

Topics in Circuits for Communications [Guest Editorial]

The three articles in this special section cover integrated circuits for future high-speed configurable backplanes and mobile TV. The articles are summarized here.     

Radio-over-fiber-based solution to provide broadband internet access to train passengers [Topics in Optical Communications]

Nowadays, combining high-bandwidth connections (e.g., 5 Mb/s/user) and fast-moving users (e.g., on a train at 300 km/h) while keeping a sufficient level of QoS is still an unsolved bottleneck. In this article we propose a cellular trackside solution for providing broadband multimedia services to train passengers. A radio-over-fiber network in combination with moving cells forms the base of this realization     

Time-limited leases in radio systems [Topics in Radio Communications]

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.     

RF-MEMS for Wireless Communications [Topics in Design and Implementation]

This article presents an introduction and overview of MEMS technology with a focus on RF applications of MEMS in the design of cellular handsets. A novel, integrated, high-Q tunable digital capacitor is discussed to demonstrate how RF-MEMS technology can be utilized to make high frequency components whose RF characteristics can be adjusted during operation, allowing for the first time reconfiguration of radio hardware under software control. It is concluded that as the consumer wireless market continues to grow and evolve, product designers will remain under ever increasing pressure to develop smaller, lighter, thinner products that are more functional, energy-efficient, and intuitive, and to do so faster and at lower cost. Although issues and challenges persist, opportunities abound, and RF-MEMS technology holds the promise of being a key enabler of future generations of more highly converged, cognitive, and flexible consumer wireless products.     

An Overlay Photonic Layer Security Approach Scalable to 100 Gb/s [Topics in Optical Communications]

As data rates outpace the capabilities of electronic encryption schemes, photonic layer security may fill the gap in providing a communication security solution at high data rates. In this article we review and highlight the advantages of our proposed optical code-division multiplexed (OCDM)-based photonic layer security (PLS) system based on high-resolution control of the optical phase of tightly spaced phase locked laser lines. Such a PLS system is scaleable to 100 Gb/s and provides a protocol independent security solution. We review the use of high-resolution control of the optical phase of mode-locked laser frequency combs as an enabling technology for a new class of OCDM systems. A network based on such systems is compatible with and can have comparable spectral efficiency to existing DWDM networks. Through inverse multiplexing of 10 Gb/s tributaries, we have already demonstrated optical transmission of a 40 Gb/s aggregate OCDM signal over 400 km. Such a PLS solution is achieved through shared phase scrambling of the individual OCDM codes assigned to each of the tributaries using an integrated micro-ring resonator-based phase coder/ scrambler. The confidentiality of OCDM-based PLS is robust against exhaustive, known plain text, and archival/forensic attacks, and can complement digital encryption operating at higher layers. Moreover, the integrity of the PLS solution is ensured through the inherent coupling to confidentiality, since knowledge of the key is needed in order to easily alter the transmitted data stream without introducing observable errors. This system can leverage advances in optical integration to support new applications where electronic encryption is impractical because of space, weight, power, availability, and cost requirements. Such applications range from timely security support for the emerging 100 GbE standards to all-optical multilevel security offered through the compatibility of PLS with transparent DWDM networks.     

Shared spectrum access for the DoD [Topics in Radio Communications]

Increasing demands are being placed on spectrum access, both domestic and abroad, as a result of current demands for global mobility, electromagnetic spectrum requirements of both outdated and future defense systems, and loss of military access to certain frequency bands due to spectrum legislation. Consequently, the DoD should identify shared spectrum access opportunities and explore dynamic spectrum access technologies to help meet the growing spectrum requirements of the military. This article discusses a few cases of current and future shared spectrum access environments to highlight the circumstances for spectrum sharing and utilization of military and commercial frequency bands.     

Fixed Mobile Convergence Architectures for Broadband Access: Integration of EPON and WiMAX [Topics in Optical Communications]

EPON and WiMAX are two promising broadband access technologies for new-generation wired and wireless access. Their complementary 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 bandwidth 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.     

XG dynamic spectrum access field test results [Topics in Radio Communications]

The XG Radio system uses dynamic spectrum access technology to determine locally unused spectrum, and then operates on these channels without causing interference to existing non-cooperative users. In August 2006 the XG Radio system was field tested at Fort A.P. Hill, Virginia, in the laboratory, and at field locations in Northern Virginia. There were three major test criteria: to cause no harm (avoid interference), to work (form and maintain connected networks), and to add value (efficiently use spectrum). This article defines the test metrics for fulfillment of these criteria, and describes the test results.     

Can RF Help CMOS Processors? [Topics in Circuits for Communications]

Digital circuits implemented in CMOS technology have been the workhorses of high performance computer processors for more than a decade, following Moore's law with exponentially increasing integration and performance. Driven by lower cost, increasing performance, and mixed-signal benefits, CMOS technology also has found increasing use in analog, and more recently, RF applications. Now, with transistor performance still improving, wires are becoming the limiting factor for speed and performance by imposing limits on communication bandwidth and latency between processing cores and memories, both off- and on-chip. Communication and circuit techniques, developed mainly for narrow band-wireless RF communication can help increase the wired communication speed in digital systems. This approach, dubbed RF Interconnect (RF-I), picks up speed for on-board and on-chip applications, changing the communication paradigm from the old parallel unidirectional time-shared bus to new transmission lines enabling reconfigurable communication using both frequency and code division multiple access techniques.     

Timing Synchronization in MF-TDMA Systems for Geostationary Satellites[Topics in Radio Communications]

The most expensive costs in satellite communication are incurred by the space segment. Therefore, effort should be focused on the efficient use of this resource. One aspect is the optimization of the physical layer, to approach the Shannon limit of channel capacity. In IP-based networks, communication between arbitrary terminals can be established, which must hold for IP-based satellite networks as well. A commonly used topology is the star network, where data are routed via the master station, which in case of satellite communications introduces a double hop for terminal-to-terminal connections [1]. A double hop requires twice the bandwidth and twice the response time, which is very unattractive for interactive services. This drawback is avoided with a fully meshed topology, where terminals can communicate directly. Of course, an appropriately designed access system is required in this context. The well-known multi-frequency, time-division multiple access (MF-TDMA) scheme slices the channel capacity along both time and frequency axes. Each fragment (slot) can be used by any station for direct communication [2, 3]. This article describes the method on an abstraction layer, starting with the high-level timing that copes with frame numbers; the low-level timing that maps the frame numbers to time instants of the local time scale; and ends with the time stamp handled in the hardware, where calculation delays and filter flushing affect the received time stamp. Compared to commercial systems, the method described in this article uses differential time stamps, which reduces the effort of the synchronization procedure.     

Detect and avoid: an ultra-wideband/WiMAX coexistence mechanism [Topics in Radio Communications]

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.