Calculation of third order intermodulation spectrum

A fast method for calculating the third order intermodulation spectrum by convolution of the input power spectrum using the FFT method is presented. The computation time is reduced to seconds even for large numbers of carriers. The computation time is insensitive to the number of different carrier types (level and bandwidth).<>     

Modeling and analysis of QPSK/TDMA burst-mode link analyzer bycomputer simulation

The authors describe modeling and simulation of a nonlinear QPSK/TDMA (quadrature phase-shift keyed/time-division multiple access) digital satellite channel and burst-mode link analyzer (BMLA), using novel computational and least-squares (LS) approaches on a VAX 11/780 computer. The BMLA is applied to channel equalization. Some simulation results are given, including results on the BMLA with LS algorithm and on the effects of nonlinearity and quantization wordlength. Emphasis is placed on the introduction of the BMLA/LS to impulse response extraction, and on the comparison and evaluation of the test results, which confirm the possibility of the BMLA/LS applications in a digital communication channel and confirm this simulation system as a powerful tool for QPSK/TDMA link analysis and channel equalization     

An open-systems approach to video on demand

Open systems will enable video servers and set-tops to provide different services in a variety of environments. Hewlett-Packard is interested in applying the principles of open systems to video on demand (VOD). In particular, the company is developing a technology base that will allow their servers and set-tops to operate in a variety of environments and enable the provision of a variety of services. The impact that the different VOD system elements have on the video server and set-top are examined from a communications standpoint. Opportunities for open or standard interfaces are identified and recommendations are made on what these should be where possible     

Derivation of cochannel and adjacent channel reuse ratiodistributions in DCA cellular systems

This paper presents the first closed-form analysis of cochannel and adjacent channel reuse ratio distributions in dynamic channel assignment (DCA) cellular systems and compares the results with conventional fixed channel assignment (FCA) cellular systems. Computer simulations show that DCA systems exhibit significantly closer cochannel and adjacent channel frequency reuse than FCA systems for a significant proportion of terminals. Mathematical analysis is used to show that this is a fundamental consequence of DCA channel pooling and that the resultant interference distributions cannot be obtained using conventional cellular engineering techniques. The closed-form expressions derived establish a theoretical lower limit to channel reuse in DCA cellular systems     

HANGMAN Gb/s network

The design and implementation of the Hewlett-Packard active node gigabit-per-second metropolitan area network (HANGMAN) prototype network are discussed. The three main areas addressed are the physical-layer transmission system, the MAC sublayer protocols, and the architecture of the network interface unit. It is shown that low-cost gigabit-per-second transmission systems are practical, particularly in the local area environment where network links are typically limited to a few hundred meters. A MAC protocol that provides a synchronous service as well as the conventional asynchronous data service is described. The node architecture is presented and the way in which a single node can support multiple concurrent physical connections and how this architecture might be used in the future to develop high-performance protocol implementations are also discussed     

Determination of device structure from GaAs/AlGaAs HEMT DC I-V characteristic curves

A procedure for the inverse modeling of GaAs/AlGaAs HEMT structures from the DC I-V characteristic is described. The procedure allows important structural parameters, including the aluminum fraction, dopant density, doped layer thickness, spacer layer thickness, physical gate length, source resistance, drain resistance, and the saturated electron velocity, in the 2DEG and in the doped AlGaAs to be obtained. The accuracy of the inverse modeling procedure is established by comparison of the derived HEMT structure with experimental results     

Simulations of HEMT DC drain current and 1 to 50 GHzS-parameters as a function of gate bias

The usefulness over an extended range of a high-electron-mobility transistor (HEMT) model previously validated for a 1-25-GHz S-parameter model is shown. Experimental and simulation results for the DC drain current and 1-50-GHz S-parameters of a pseudomorphic 0.32-μm gate AlGaAs-InGaAs-GaAs HEMT are presented. The model predicts the device's DC current and S-parameters as functions of the applied gate bias with good accuracy. The core of the model is directly dependent on the HEMT wafer structure and the physical gate length. As part of the modeling procedure, a value of (1.77±0.07)×10⁵ m-s^-1 is found, confirming the results of other research, for the electron velocity in undoped pseudomorphic In_0.15Ga_0.85As under ≈0.3-μm gates     

HIPERLAN channel assignment strategies

HIPERLAN (high performance radio local area network) (type I) is an ETSI high speed wireless LAN standard. The simulation results presented suggest that the best RSSI-based HIPERLAN channel assignment strategy is to always choose the channel with the lowest amount of measured interference, rather than the first channel measured below the clear channel assessment (CCA) threshold