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Radio and Wireless Conference, 1998. RAWCON 98. 1998 IEEE

Date 9-12 Aug. 1998

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  • Proceedings RAWCON 98. 1998 IEEE Radio and Wireless Conference (Cat. No.98EX194)

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    Freely Available from IEEE
  • Index of authors

    Page(s): 0_5
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    Freely Available from IEEE
  • MM-wave wireless access technology for the wideband wireless local loop applications

    Page(s): 5 - 8
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    We describe and demonstrate a wideband wireless local loop (W-WLL) testbed concept based on local multipoint distribution services (LMDS) millimeter wireless technology but with a modified access and backbone architecture. The testbed is intended as a demonstration platform for broadband wireless services particularly for high speed internet and shared multimedia applications. The investigation is focused on the radio link design, network architecture, system integration, and compatible interface to the existing ATM fiber and satellite core networks View full abstract»

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  • Design considerations for extremely high-Q integrated inductors and their application in CMOS RF power amplifier

    Page(s): 265 - 268
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    An extremely high-Q monolithic inductor (Q>2000) on silicon substrate was reported by Pehlke, Burstein and Chang (see Proceedings of the IEEE International Electron Device Meeting, pp. 63-6, 1997). The reported Q is 3 order of magnitude higher than a previously reported monolithic inductor. Such high quality factor may greatly improve the performance of monolithic RF circuits. Both 1-port (one terminal at ground) and 2-port (no terminal at ground) scattering parameters of the high-Q inductor were compared to examine any possible differences in device characteristics. A broadband physical model of the active inductor on silicon are presented to illustrate the improvement of quality factor. A design space with a range of gain and phase difference of current in the coils of the active inductor is reported. A typical application of the active inductor in CMOS RF power amplifier design is shown to illustrate the feasibility of applying the active inductor in RF circuits design View full abstract»

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  • Transmission techniques for increased power efficiency in OFDM-based wireless communication systems

    Page(s): 15 - 18
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    Due to their robustness against the time-dispersive effects of multipath propagation, OFDM schemes are widely considered for high rate transmission in digital wireless systems. This paper deals with power efficiency issues in OFDM-based broadband wireless systems for the MM-wave band. We consider grossly nonlinear power amplifiers only, within conventional and two-branch transmitter structures; channel coding and interleaving in the frequency domain; a space-diversity, maximal-ratio combining scheme, and, as an alternative to conventional ARQ, similar time-diversity, packet combining schemes. A set of simulation results is presented and discussed View full abstract»

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  • A FDM multiple user software configurable arbitrary format (MUSCAF) UHF receiver prototype

    Page(s): 35 - 38
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    Conventional PMR style radio receivers based on analog technology receive one frequency channel at any one time. This paper presents an alternative digital solution which currently allows up to 16 simultaneous 12.5 kHz spaced FDM channels to be demodulated to ETSI-B type approval standards, and uses conventional, currently available cost effective componentry. Arbitrary modulation formats per channel are supported. Technical issues up to and including the analog to digital converter (ADC) interface are discussed View full abstract»

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  • Linearization performance for a polar work function predistorter

    Page(s): 325 - 328
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    We present a polar work function predistorter (WFP) which shows good RF amplifier linearization performance and wideband capability. We describe a DSP optimization scheme that allows the linearizer to adapt and maintain optimum out-of-band performance. We further describe a simulator that accurately models the performance of the system and predicts dynamic distortion due to the WFP implementation as well as an unexpected nonlinear optimum solution for the am-to-am distortion compensation View full abstract»

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  • System performance analysis of impulse radio modulation

    Page(s): 67 - 70
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    We present a system performance analysis of impulse radio modulation using block waveform encoding signal sets. We analyze both the multiple-access performance in a channel with additive white Gaussian noise, and the single-link performance in a channel with dense multipath View full abstract»

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  • An IF digitizing receiver for a combined GPS/GSM terminal

    Page(s): 39 - 42
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    For the purpose of traffic telematics (route guidance, fleet management etc.) one needs terminals on the vehicle for the quasi-simultaneous reception of cellular phone (GSM) and satellite navigation (GPS). A conventional approach uses two complete receivers for these two tasks. We describe a cost-saving solution for a combined receiver which relies on the TDM structure of the GSM signal. Our solution is based on an bandpass-sigma-delta ADC for IF digitizing View full abstract»

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  • Ultra high speed digital processing for wireless systems using passive microwave logic

    Page(s): 43 - 46
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    This paper proposes two novel high-speed digital logic families that are implemented using passive microwave circuits. The proposed logic gates can process binary information represented in two high frequency carrier modulation formats-amplitude shift keying (ASK), and binary phase shift keying (BPSK). The fundamental logic gates (NOT, OR, AND) presented for both these data representations can process extremely high speed bit streams (1-100 Gbps). The combinational circuits formed from these passive logic gates can operate much faster than traditional electronic gates because they are not limited by the finite carrier mobility that is characteristic of semiconductors. Besides their higher operating speeds, these circuits are well suited for wireless communication systems because they process digital signals in a native high frequency transmission format and it is easy to integrate them with analog RF/microwave circuits View full abstract»

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  • Electrical package modeling for high power RF semiconductor devices

    Page(s): 359 - 362
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    A modeling procedure is developed for generating electrical package models for air-cavity metalized ceramic packages. Such models are capable of accounting for parasitic effects associated with the capacitance of the bonding pads in the package and the inductance of the bond wires. We have applied this modeling procedure to extract package equivalent circuit models for some of Motorola's LDMOS RF power transistors. The models have been validated up to the third harmonic with respect to the device's operating frequency. It has been demonstrated that the package parasitic effects contribute significantly to an accurate prediction of the packaged transistor nonlinear performance View full abstract»

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  • A high efficiency MMIC power amplifier for phased array antenna applications

    Page(s): 333 - 334
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    A high efficiency two stage MMIC power amplifier has been designed to meet the requirements of a 64 element transmit phased array antenna operating at 8.2 GHz. The array will provide a high speed data communication link for the NASA GSFC new millennium program. The array is to be installed on the Earth observing scientific satellite EO-1 scheduled for launch in 1999. The two stage MMIC amplifier cell includes an on chip gate bias reference. It provides 23 dB small signal gain, 45% PAE, and requires only 1 square millimeter of die area View full abstract»

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  • Analysis and coloring of a shotgun cellular system

    Page(s): 51 - 54
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    This paper analyzes cellular systems where the base stations are placed at random. Analysis compares the base station to mobile link in random systems to ideal hexagonal systems. Under log-normal shadow fading and sectorizing-but no channel planning-the random system has carrier to interference levels within 4 dB and spectral efficiency within 2 dB of the hexagonal system. A simple linear-time channel assignment algorithm reduces each of these differences by 1 dB. Thus, at a modest cost in performance, deployment costs and deployment speed can be greatly reduced View full abstract»

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  • MMIC-based class-A/F power amplifier for ultra-linear-commercial PCS multiple-modulation-format base station power amplification

    Page(s): 329 - 332
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    An MMIC based, three stage, class-A/F driver amplifier provided greatly improved linear power in concurrent multiple modulation formats over previous MMICs and class A/F amplifiers. The modified class A/F structure suppresses the 3rd and 5th order products by more than 15.8 dB and 13 dB respectively, over a typical class A/F amplifier, and by 17.8 dB over a straight class A amplifier. This provides a 3rd order intercept of 56.7 dBm. for only 48 watts DC. The amp has 0.3 dB gain flatness over a 10% AMPs bandwidth. The technique is patented View full abstract»

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  • MAI cancellation by optimum single-user detection for DS/CDMA systems using random binary codes

    Page(s): 177 - 180
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    The optimum single-user detector (OSD) for a DS/CDMA based communications system is investigated using random binary signature codes of length 32 and 64 chips. The BER performances are obtained by Monte-Carlo simulation for spectral efficiencies of 50% and 100%. Results show that the OSD performs significantly better than the matched filter detector (MFD) with a modest increase in complexity. It is also seen that noise enhancement is induced due to MAI cancellation which degrades the OSD performance View full abstract»

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  • Comparison of antenna diversity schemes

    Page(s): 161 - 164
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    This paper compares 4 kinds of simple diversity schemes for an indoor scenario at 2.4 GHz: polarisation, dual antenna, antenna and polarisation, and triple antenna for an indoor scenario, all combined according to 5 different techniques. Useful parameters are extracted statistically. We conclude that the power combining method gives the best results, and that the extra complexity of the 3 antenna case is not always justified from a cost viewpoint View full abstract»

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  • Table-based FET model assembled from small-signal models

    Page(s): 355 - 358
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    A data-table based large-signal MESFET model is presented based on an ensemble of bias-dependent small-signal equivalent circuits. The model is capable of accurate simulation of small-signal S-parameters over the data-acquisition bias range. In addition to the dc current sources, the model contains two quasi-static charge sources and RF current sources, which are generated by integration of respective intrinsic small-signal element values with respect to the port voltages. All equivalent elements are obtained by cubic spline interpolation. Extrapolation of the model beyond the measurement range is taken into account. The model is extracted by an in-house software without involving optimization. The validity of the model is demonstrated by comparing the simulation of small-signal S-parameters over a wide bias range and power performance to the measured data View full abstract»

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  • A mechanism for matching application message generation with wireless network performance

    Page(s): 59 - 62
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    Because of the modular layered architecture approach to network design, the application layer is isolated from the characteristics of the physical network. This isolation causes the application layer to blindly construct packets for transmission without regard to the likelihood that these packets will be received in a timely and reliable manner at the destination node. With this type of a system, a potentially unstable condition, in which queues grow without bound, can be avoided by adding a control loop with a feedback characteristic that provides metrics on the wireless network. In any actual implementation, queue buffers are limited in size so the queues can not grow without bound. In wireless systems, the network access delays can be rather pronounced. In such a system, knowledge of this metric can allow the application layer to adapt its message production rate to match the consumption rate of the network. This paper presents a mechanism that provides feedback of channel access metric from the data link layer to the application layer. The mechanism provides a means to exchange this information without affecting the network and transport layers of the stack. This shift from the traditional layered network architecture; while loosing some modularity and encapsulation of the stack layers, gains us more efficient use of the physical media View full abstract»

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  • Frequency-domain delay distortion equalization-the complex spectrum regeneration method

    Page(s): 249 - 252
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    In radio communications, equalization of delay distortion due to multipath propagation is one of the most necessary and difficult problems. There are two equalization methods, i.e., the time-domain method and frequency-domain method. The frequency-domain linear equalization, in which equalization is performed by deconvolution of the received signal by the transfer function of the propagation path is presented. Since this method is implemented by software-based devices, faster, stable, and more adaptive equalization is possible View full abstract»

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  • A PHEMT MMIC broad-band power amplifier for LMDS

    Page(s): 121 - 124
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    A two-stage monolithic microwave integrated circuits (MMIC) broad-band power amplifier with AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistor (PHEMT) has been developed for the up-link and down-link applications for local multipoint distribution systems (LMDS) in the frequency range of 24 ~28 GHz. The amplifier has a small signal gain of 18.6 dB at 24.5 GHz and 16.7 dB at 27.1 GHz. It achieved output powers of 19.8 dBm with PAE of 19.8% at 24.5 GHz and 18.8 dBm at 27.1 GHz View full abstract»

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  • The application of low noise amplifiers in CDMA cellular and PCS systems for coverage and capacity enhancements

    Page(s): 181 - 184
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    The paper examines the use of low noise amplifiers (LNAs) as a technique to enhance reverse-link coverage and capacity in a CDMA wireless network. The reduction of system noise figure for a base station is accomplished by installing LNAs between the receive antenna and the radio. Using noise figure theory, the paper develops an analytical model for the SNR improvement. The SNR models are found to be functions of the reverse-link noise rise, which constitutes a measure of the reverse-link capacity limits. Since the CDMA system uses reverse-link power control, the improvement in SNR is manifested in the reduction of the mobile's transmit power. In terms of capacity, the reverse-link capacity of a CDMA base station with installed LNAs has not improved. However, the capacity of a neighboring base station (with no LNAs) has improved. This is because the mobile within the coverage area of a base station (with LNA) now transmits less power and contributes less loading to the neighboring base station (with no LNA) View full abstract»

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  • Performance of an adaptive rate modem using quasi-analytic simulation techniques

    Page(s): 145 - 148
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    Analysis of bit error rate (BER) of a π/M-MDPSK modem in an (additive white Gaussian noise) AWGN channel using quasi-analytic simulation techniques is considered in this paper. Implementation losses, most notable at M=32 and 64, which result from practical transmit and receive filtering, can be largely overcome by increased accuracy symbol timing recovery and a fixed equalization filter View full abstract»

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  • Triple input single chip diversity LNA

    Page(s): 335 - 337
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    For mobile terminals using antenna diversity, a prototype monolithic integrated triple input low noise amplifier (LNA) with diversity function has been realized. The diversity LNA has more than 10 dB gain and less than 4 dB noise figure from 4 to 5 GHz. For comparison, a single LNA was fabricated on the same wafer showing very similar performance. The chip area is reduced by more than 30% and the power consumption by 50% compared to a multichip LNA with a switch View full abstract»

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  • Simulation of coded MC-DS-CDMA systems

    Page(s): 189 - 192
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    We use computer simulations to compare the performance improvements associated with coding on a Gaussianized BPSK-MC-DS-CDMA system and a non-Gaussianized DPSK-MC-DS-CDMA system. The effects of coding on the Gaussianized system approach the performance of a coded BPSK system operating in a Gaussian channel while the non-Gaussianized system performance is approximately 4 dB from the coded DPSK system operating in a Gaussian channel View full abstract»

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  • The use of arbitrary sequences for real-time wireless channel evaluation

    Page(s): 245 - 248
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    The need for accurate channel measurements for broadband communication systems is well known. The problem of system identification constitutes the basis for any wireless channel measurement and estimation. The classical approach to system identification employs a pseudo-random (PR) sequence as a test signal. The system response to this PR sequence is then correlated with a replica of the test signal in order to obtain an estimate of the system impulse response. The fundamental assumption upon which this technique is based is that the PR test signal has an ideally impulsive autocorrelation function (ACF). In practice, the majority of sequences of interest do not possess this idealised ACF. The consequences of employing test signals with nonimpulsive ACF results in the introduction of estimation errors. The problem is further accentuated when the classical approach to system identification is applied to channel estimation. In this paper, the problem of system identification is analysed for the case when the ACF of the test signal is non-ideal. It is shown that the system impulse response estimation error can be reduced by using a compensation filter whose response has been related to the imperfection in the test signal ACF. The applicability of this approach to broadband channel estimation is then demonstrated View full abstract»

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