LED spectral slicing for single-mode local loop applications

An approach towards a single-mode local loop is presented in which each customer is given a dedicated wavelength channel by taking different wavelength slices from identical LEDs. This is accomplished by means of wavelength division multiplexing (WDM) components. Results from a four-channel system operating at 2 Mbit/s over 2.2 km, together with a theoretical analysis of a ten-channel system, are presented     

SONET ring applications for survivable fiber loop networks

Synchronous optical network (SONET) self-healing rings (SHR) are studied in the loop environment. SONET SHR architectures for loop feeder networks are discussed, focusing on three possible dual central office (CO) architectures for fiber loop networks, using SONET SHRs to reduce network costs and provide network service survivability. These architectures reflect an integrated planning concept for SONET networks that eliminates the boundary between the access network and the inter-office network. It is shown that the use of SONET SHRs makes it easy to evolve to a protected dual CO access architecture. Economic and survivability studies are discussed. The economic studies show that using the ring approach yields significant advantages over the traditional diverse protection approach in terms of cost and survivability, especially for the dual CO architectures     

Passive optical local networks for telephony applications and beyond

A new digital telephone system is described using a passive optical network. Downstream transmission is broadcast and optical time-division, multiple-access (OTDMA) is used in the upstream path. The principle advantage of this approach is that exchange resources and fibres are shared between a large number of customers     

Reverse link performance of wireless local loop CDMA networks

We study the effect of directional subscriber antennas on the reverse link performance of a power-controlled code-division multiple access (CDMA) network in wireless local loop deployments. We investigate the capacity gain that is attained in wireless local loop (WLL) CDMA over mobile cellular systems and its variation as a function of the channel statistics. We also determine the overhead that soft handoff and directional subscriber antennas impose on the WLL system capacity     

Sampling of French local networks and applications

In this paper the authors describe a study in progress by which it is intended to represent all the French local telephone networks by just a small number of typical cases. The objectives are firstly, to gain a better knowledge of the existing network and secondly, to be able to compare equipment policies by simulating the evolution of the sample networks. The representative areas were chosen by original data analysis methods (principal component analysis followed by classification and choice of samples). Detailed data appertaining to the sample areas were then collected. They give examples of overall statistical results extrapolated at national level and discuss the corresponding applications. Lastly, they consider further developments of the study.     

光纤传感器在全光网络安全及防范措施中的应用

在对全光网络存在的安全问题分析的基础上,总结了现存的攻击方法,讨论了光纤传感器在全光网络安全及防范措施中应用,在现有的理论模型基础上提出一种新型的全分布式光纤传感器模型,最后分析了该方案解决全光网络安全隐患的有效性.     

Amplitude-locked loop analysis for calibration applications

A linear analysis of an ALL, as it would be used in an amplitude calibration, is presented. The impact of different loop filter choices is considered, for steady-state error and loop dynamics as well as for disturbances in the input amplitude and peak detector ripple. It is shown that in most applications a loop filter with an integrator is desirable.     

Communication-sensitive loop scheduling for DSP applications

The performance of computation-intensive digital signal processing applications running on parallel systems is highly dependent on communication delays imposed by the parallel architecture. In order to obtain a more compact task/processor assignment, a scheduling algorithm considering the communication time between processors needs to be investigated. Such applications usually contain iterative or recursive segments that are modeled as communication sensitive data flow graphs (CS-DFGs), where nodes represent computational tasks and edges represent dependencies between them. Based on the theorems derived, this paper presents a novel efficient technique called cyclo-compaction scheduling, which is applied to a CS-DFG to obtain a better schedule. This new method takes into account the data transmission time, loop carried dependencies, and the target architecture. It implicitly uses the retiming technique (loop pipelining) and a task remapping procedure to allocate processors and to iteratively improve the parallelism while handling the underlying communication and resource constraints. Experimental results on different architectures demonstrate that this algorithm yields significant improvement over existing methods. For some applications, the final schedule length is less than one half of its initial length     

Competing for throughput in the local loop

The voice-grade telephone channel is the communication medium most widely available throughout the world. Its limitations, a relatively narrow bandwidth and a moderate SNR figure, have challenged telecommunication researchers and engineers over several decades to develop technologies able to pass higher and higher data rates. The sophisticated combination of trellis coding and quadrature amplitude modulation increases the bandwidth utilization close to the Shannon limit of 10 b/s/Hz for the 3.1 kHz bandwidth voice channel. However, the resultant data rate of about 30 kb/s does not even begin to approach the throughput needed by multimedia applications. Fortunately, twisted pair bandwidth reaches up to several megahertz, so multilevel signaling implemented as in the xDSF family of modems enables data rates of several megabits per second to be reached. Standard ADSL modems are able to deliver 8 Mb/s to a subscriber in the best case. VDSL modems can deliver 52 Mb/s, but only up to 300 m, so their mass implementation will only become possible when fiber migrates into an access network closer to the user premises. Both broadband xDSL solutions approach the Shannon limit and the related spectral efficiency as well, so there is not much room left for a transmission improvement     

Optical loop mirror multiplexer

A novel fiber-optic configuration has been developed to generate high-repetition-rate optical pulses up to hundreds of GHz. The set-up consists of a parallel connection of optical loop mirrors. The multiplexer has potential applications in multichannel parallel processing and in high speed optical communications. With the use of fiber switches, our set-up can be converted into an optical bit pattern generator.     

Hybridizing the local loop

The recent collapse of two widely publicized merger proposals-of Bell Atlantic with Tele-Communications International and Southwestern Bell with Cox Broadcasting-has shaken some industry pundits, who are now wondering if communications convergence is on hold, if not dead. Whether or not phone and cable TV companies merge, the technologies they use to deliver their services to the home will do so. The author speculates how electric utilities may play a key role in their amalgamation     

Phase-locked loop design for on-chip tuning applications

A novel phase-locked loop scheme is proposed, the main application of which is in on-chip tuning circuits. It involves the use of a variable gain amplifier and also a frequency tunable loop filter, providing infinite hold-in range, a fractionally constant pull-out range and also a fractionally constant ripple     

A low-power phase-locked loop for UWB applications

This paper describes a low-power phase-locked loop (PLL) design for WiMedia UWB synthesizer implemented in a 0.13-μm CMOS process. Three parallel PLLs and a multiplexer (MUX) constitute a frequency synthesizer which is used to generate carrier frequencies to UWB band groups 1 and 3. The implemented PLL consumes only 10 mW from a 1.2-V supply. Moreover, it achieves a close-in spurious tone level of −54 dBc and in-band phase noise of −78 dBc/Hz.     

Compact current-mode loop filter for PLL applications

A novel capacitance scaling technique is proposed to reduce on-chip capacitor area using a dual-path self-biased current-mode filter. The capacitor multiplier is obtained by the relative ratio of charge-pump currents I/sub cp2//(I/sub cp2/-I/sub cp1/), rather than the scaling ratio I/sub cp2//I/sub cp1/. Compared with the original current-mode filter, the demonstrated loop filter of 250 pF capacitance is achieved with only 25 pF (90% die area saving), and the resistor area is reduced by 50% owing to reuse of the degenerated resistor R/sub G/.     

Optical phase-locked loop for coherent detection optical receiver

A novel subcarrier-based optical phase-locked loop (SC-OPLL/sup /spl reg//), with off-the-shelf optical components, is presented and demonstrated. The method, based on a continuous-wave laser and optical subcarrier modulation using a standard LiNbO/sub 3/ Mach-Zehnder modulator, allows easier practical implementation than the previously proposed OPLL circuits based on laser direct modulation.     

Repacking on demand for two-tier wireless local loop

This paper proposes a radio channel assignment scheme called repacking on demand (RoD) for two-tier wireless local loop (WLL) networks. A two-tier WLL overlays a macrocell with several microcells. When a new call arrives at a two-tier WLL with RoD, if no idle channel is available in both the microcell and the macrocell, repacking is performed (i.e., a call in the macrocell is moved to its corresponding microcell), and then the reclaimed macrocell channel is used to serve the new call. An analytic model is proposed to compute the call blocking probability of the two-tier WLL with repacking. This analytic model is validated against simulation experiments. We prove that the blocking probability is not affected by the call holding time distributions, but is only dependent on the mean of the call holding times. Compared with some previous proposed schemes, RoD has low blocking probability and significantly reduces repacking rate.     

New architectures for diversity in fiber loop networks

Active and passive multiplexing technologies and alternative architectural approaches to diverse routing for fiber-loop networks are described. It is shown on the basis of Markov models that the mean time to failure (MTTF) for a 1:1 protected system can be significantly improved by deploying fiber with alternate paths and duplicate central offices. Specific network examples are used to compare installed first costs of the active and passive multiplexing alternatives for various loop-diversity approaches. The results indicate the requirements for diverse routing can have a large impact on the choice of technologies and approaches for fiber loop networks. Specifically, a passive double-star architecture, using dense wavelength-division multiplexing (WDM) techniques, represents a promising technological approach to diverse routing, for it has the lowest installed first cost for diversity in the loop of the several approaches studied, both in suburban and urban areas     

UHF reader loop antenna for near-field RFID applications

A novel reader loop-type antenna for ultra-high-frequency (UHF) near-field radio frequency identification (RFID) applications is presented. This antenna, printed on a 0.8 mm-thick FR4 substrate with a diameter of 16 cm, is composed of four curved strips and four pairs of coupled stubs, and achieves a wide impedance bandwidth from 840 to 1300 MHz. The proposed structure can make large currents along the loop so that a strong and uniform magnetic field distribution is excited in the region around the antenna. Measurements show that the antenna operating with a commercial reader demonstrates good performance of tag identification with inductive coupling for near-field RFID applications.     

A comparative evaluation of DECT, PACS, and PHS standards forwireless local loop applications

In a comparative analysis the performance and capacity of DECT, PACS, and PHS for wireless local loop applications have been investigated. This article reports the results of both qualitative and quantitative analyses. The qualitative evaluation consists of a detailed comparison of the parameters of each standard and their relevance in WLL applications. In the quantitative analysis detailed simulations were performed covering diverse sets of conditions. The results of both types of analysis are presented. A major conclusion is that all three standards provide satisfactory performance for WLL applications. For low traffic environments PACS, which can employ larger cells, performs better than the other two standards. In suburban areas where, in addition to coverage capabilities, capacity is an issue, DECT has better performance. For high traffic density urban areas with great capacity requirements, the three standards all have good performance