A Linear Power Amplifier Design Using an Analog Feedforward Method

We propose and describe the fabrication of a linear power amplifier (LPA) using a new analog feedforward method for the IMT‐2000 frequency band (2,110–2,170 MHz). The proposed analog feedforward circuit, which operates without a pilot tone or a microprocessor, is a small and simple structure. When the output power of the fabricated LPA is about 44 dBm for a two‐tone input signal in the IMT‐2000 frequency band, the magnitude of the intermodulation signals is below ?60 dBc and the power efficiency is about 7%. In comparison to the fabricated main amplifier, the magnitude of the third intermodulation signal decreases over 24 dB in the IMT‐2000 frequency band.     

Wide‐Band Fine‐Resolution DCO with an Active Inductor and Three‐Step Coarse Tuning Loop

This paper presents a wide‐band fine‐resolution digitally controlled oscillator (DCO) with an active inductor using an automatic three‐step coarse and gain tuning loop. To control the frequency of the DCO, the transconductance of the active inductor is tuned digitally. To cover the wide tuning range, a three‐step coarse tuning scheme is used. In addition, the DCO gain needs to be calibrated digitally to compensate for gain variations. The DCO tuning range is 58% at 2.4 GHz, and the power consumption is 6.6 mW from a 1.2 V supply voltage. An effective frequency resolution is 0.14 kHz. The phase noise of the DCO output at 2.4 GHz is –120.67 dBc/Hz at 1 MHz offset.     

Modified UMP-BP decoding algorithm based on mean square error

The modified uniformly most powerful belief-propagation (UMP-BP) decoding algorithm is proposed. This utilises a new normalisation factor to diminish the error introduced by approximation of the soft values. The proposed algorithm shows better performance than the normalisation UMP-BP algorithm, and has the same complexity of implementation.     

Resilience in GMPLS path management: model and mechanism

The recent advent of converging the IP and optical networks has necessitated the development of a generalized multiprotocol label switching framework. Resilience becomes more important than ever before in a GMPLS network since a single cut of an optical fiber may generate hundreds of link and node failures at high layers of the GMPLS architecture. In this article we briefly survey the current work regarding GMPLS recovery management, and present a new resilience-based dynamic GMPLS path management strategy. We present a simple model to represent the resilience requirements in GMPLS path management, and propose fast path management algorithms. The salient feature of the proposed approach is that it enables the paths to be dynamically selected under multiple simultaneous failure occurrences while satisfying the resilience requirement. Backup path design rules are developed, and the condition for backup path availability is derived for the special mesh-type GMPLS network. Finally, a simple example is shown to illustrate the effectiveness of the proposed resilience model and path management mechanism.     

Network mobility and protocol interoperability in ad hoc networks

The integration of various network-level functions, including routing, management, and security, is critical to the efficient operation of a mobile ad hoc network. In this article we focus on network mobility (rather than node mobility), implying the movement of entire subnetworks with respect to one another, while individual users initially associated with one such subnetwork may also move to other domains. One example is a battlefield network that includes ships, aircraft, and ground troops. In this "network of networks", subnets (e.g. shipboard networks) may be interconnected via a terrestrial mobile wireless network (e.g., between moving ships). We discuss the design and implementation of a new ad hoc routing protocol, a suite of solutions for policy-based network management, and approaches for key management and deployment of IPsec in a MANET. These solutions, in turn, are integrated with real-time middleware, a secure radio link, and a topology monitoring tool. We briefly describe each component of the solution, and focus on the challenges and approaches to integrating these components into a cohesive system to support network mobility. We evaluate the effectiveness of the system through experiments conducted in a wireless ad hoc testbed.     

Performance of GaAs-AlGaAs V-grooved inner stripe quantum-well wirelasers with different current blocking configurations

GaAs-AlGaAs V-grooved inner stripe (VIS) quantum-well wire (QWW) lasers grown by metalorganic chemical vapor deposition with different current blocking configurations, n-blocking on p-substrate (VIPS), p-n-p-n blocking on n-substrate (VI(PN)_nS) and p-blocking on n-substrate (VINS) have been fabricated and characterized. The VIPS QWW lasers show the most stable characteristics with effective current confinement: one of the lasers shows fundamental transverse mode, lasing up to 5 mW/facet, typical threshold current of 39.9 mA at 818.5 mm, an external differential quantum efficiency of 24%/facet, and characteristic temperature of 92 K. The current tuning rate was almost linear at 0.031 mm/mA, and the temperature tuning rate was measured to be 0.14 nm/°C. Comparison of the light output versus current characteristics of the lasers with different current blocking configurations is presented here     

SMAQ: a measurement-based tool for traffic modeling and queuinganalysis. II. Network applications

For pt. I see ibid. p.56-65 (1998). SMAQ is a measurement-based tool for integration of traffic modeling and queuing analysis. It can be used in a variety of network design areas. For instance, it can be used as a traffic generator to generate various traces for network testing. It also provides numerical solutions of the queue length and loss rate performance for transport of multimedia traffic. Several application modules are built into the tool for the evaluation of statistical multiplexing, buffer dimensioning, and link bandwidth allocation. Other examples include the evaluation of traffic shaping, local-congestion control, and the modeling of wireless channel dynamics. As one will find, the SMAQ tool indeed provides a solution technique for network engineers to solve many of the current design issues