By Topic

Selected Areas in Communications, IEEE Journal on

Issue 3 • Date April 2002

Filter Results

Displaying Results 1 - 17 of 17
  • Guest editorial channel and propagation models for wireless system design I

    Publication Year: 2002 , Page(s): 493 - 495
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | PDF file iconPDF (172 KB) |  | HTML iconHTML  
    Freely Available from IEEE
  • Capacity of MIMO systems based on measured wireless channels

    Publication Year: 2002 , Page(s): 561 - 569
    Cited by:  Papers (128)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (293 KB) |  | HTML iconHTML  

    We measure the capacity of multiple-input multiple-output radio systems in microcellular environments. We use a new data evaluation method that allows to evaluate the cumulative distribution function of the capacity from a single measurement. This method is based on an extraction of the parameters of the multipath components and, thereafter, a synthetic variation of their phases. In the analyzed environments, we find capacities to be about 30% smaller than would be anticipated from an idealized model. In addition, the frequency selectivity of the channel makes the CDF of the capacity steeper and, thus, increases the outage capacity, compared with the frequency-flat case, but the influence on the mean capacity is small View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Outdoor BLAST measurement system at 2.44 GHz: calibration and initial results

    Publication Year: 2002 , Page(s): 570 - 583
    Cited by:  Papers (32)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (567 KB) |  | HTML iconHTML  

    There are ever increasing demands for additional capacity in wireless communications to handle voice, data, and wideband Internet applications. These demands are constrained by the bandwidth that was allocated to wireless communications. The spectral efficiencies in present day wireless systems hover around 1 bit/s/Hz. Bell-labs Layered Space-Time (BLAST) is a communication technique for achieving very high spectral efficiencies in highly scattering environments using multiple transmit and receive antennas. A measurement campaign was undertaken to assess the BLAST gains in spectral efficiency in the suburban outdoor environment for stationary subscribers. The measurements employed directive antennas to better control interference from adjacent cells. The measurements were performed over a narrow band at 2.44 GHz with five transmitting and seven receiving antennas, respectively. Extensive calibration methods, assisted by simulations, were developed to assure accurate results for the BLAST capacities of the measured remote subscriber sites. Initial results indicate that BLAST capacities of C B⩾38 bits/s/Hz at 20% of the measured locations and CB⩾24 bits/s/Hz at 50% of these locations are feasible, for reasonable link parameters and negligible interference View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Statistical modeling of small-scale fading in directional radio channels

    Publication Year: 2002 , Page(s): 584 - 592
    Cited by:  Papers (23)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (383 KB) |  | HTML iconHTML  

    After a review of the known description of time-variant channels by means of system and correlation functions, a consistent extension of this description to directional time-variant channels is described. This extension allows a clear distinction between time- and space-variant effects in directional mobile radio channels. The major intention of the described directional extension however is the derivation of a statistical modeling approach for small-scale fading effects in time-variant wideband directional channels, which can be regarded as a consistent extension of the well established Rayleigh or Rice-fading approach for nondirectional time-variant narrowband channels. The approach, which is based on the time and aperture-variant transfer function, appears to be preferable to the frequently used statistical modeling of the time-variant angle-resolved impulse response for several reasons. The major advantage is that the approach can cope with the demand for a great number of superimposing components as the basis for statistical modeling. The correlation between adjacent values is proposed to be achieved by filtering with appropriate directional scattering functions. The description of the modeling approach, as done in the present paper, is intended to be general and universal; for the application on certain channel types statistical distribution functions and parameters to be used with the approach can readily be determined from appropriate measurements View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Channel modeling and characterization at 17 GHz for indoor broadband WLAN

    Publication Year: 2002 , Page(s): 593 - 601
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (330 KB) |  | HTML iconHTML  

    This paper provides the results of a complete study about the indoor radio propagation channel at 17 GHz. Wideband parameters, as coherence bandwidth or rms delay spread, and coverage are analyzed for the design of an OFDM-based broadband WLAN. A discussion of some adequate system parameters is also included. The report presents the characterization results as well as a previously developed indoor channel model; both of them have been checked and compared to bibliography results in order to verify their reliability View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Statistical characterization of urban spatial radio channels

    Publication Year: 2002 , Page(s): 539 - 549
    Cited by:  Papers (56)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (413 KB) |  | HTML iconHTML  

    We present a statistical analysis of wideband three-dimensional channel measurements at base station locations in an urban environment. Plots of the received energy over azimuth, elevation, and delay planes suggest that the incident waves group to clusters in most measured transmitter positions. A super-resolution algorithm (Unitary ESPRIT) allows one to resolve individual multipath components in such clusters and hence enables a detailed statistical analysis of the propagation properties. The origins of clusters-sometimes even individual multipath components-such as street apertures, large buildings, roof edges, or building corners can be localized on the city map. Street guided propagation dominates most of the scenarios (78%-97% of the total received power), while quasi-line-of-sight over-the-rooftop components are weak(3%-13% of the total received power). For this measurement campaign, in 90% of the cases, 75% of the total received power is concentrated in the two strongest clusters, but only 55% in the strongest one. Our analysis yields an exponential decay of power with 8.9 dB/μs, and a standard deviation of the log-normally distributed deviations from the exponential of 9.0 dB. The power of cross-polarized components is 8 dB below copolarized ones on average (vertical transmission) View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Spatial and temporal characteristics of 60-GHz indoor channels

    Publication Year: 2002 , Page(s): 620 - 630
    Cited by:  Papers (148)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (364 KB) |  | HTML iconHTML  

    This article presents measurement results and models for 60-GHz channels. Multipath components were resolved in time by using a sliding correlator with 10-ns resolution and in space by sweeping a directional antenna with 7° half power beamwidth in the azimuthal direction. Power delay profiles (PDPs) and power angle profiles (PAPs) were measured in various indoor and short-range outdoor environments. Detailed multipath structure was retrieved from PDPs and PAPs and was related to site-specific environments. Results show an excellent correlation between the propagation environments and the multipath channel structures. The measurement results confirm that the majority of the multipath components can be determined from image based ray tracing techniques for line-of-sight (LOS) applications. For non-LOS (NLOS) propagation through walls, the metallic structure of composite walls must be considered. From the recorded PDPs and PAPs, received signal power and statistical parameters of angle-of-arrival and time-of-arrival were also calculated. These parameters accurately describe the spatial and temporal properties of millimeter-wave channels and can be used as empirical values for broadband wireless system design for 60-GHz short-range channels View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The effect of precipitation on microwave LMDS networks-performance analysis using a physical raincell model

    Publication Year: 2002 , Page(s): 615 - 619
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (285 KB) |  | HTML iconHTML  

    This article proposes an application of the EXCELL model to microwave local multipoint distribution systems. With EXCELL, validated in many years of observations with a meteorological radar, rain is modeled by a population of exponentially-profiled raincells. Their statistics can be made to honor any given rainfall cumulative distribution function. It is, thus, possible to simulate synthetic precipitation events so that rain effects on various radio link topologies (point-to-point or multipoint) can be evaluated on each event. Both copolar and crosspolar effects were modeled, and the C/I and C/N statistics were evaluated for a large number of events View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A space-time correlation model for multielement antenna systems in mobile fading channels

    Publication Year: 2002 , Page(s): 550 - 560
    Cited by:  Papers (204)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (546 KB) |  | HTML iconHTML  

    Analysis and design of multielement antenna systems in mobile fading channels require a model for the space-time cross correlation among the links of the underlying multiple-input multiple-output (MIMO) channel. In this paper, we propose a general space-time cross-correlation function for mobile frequency nonselective Rice fading MIMO channels, in which various parameters of interest such as the angle spreads at the base station and the user, the distance between the base station and the user, mean directions of the signal arrivals, array configurations, and Doppler spread are all taken into account. The new space-time cross-correlation function includes all the relevant parameters of the MIMO fading channel in a clean compact form, suitable for both mathematical analysis and numerical calculations/simulations. It also covers many known correlation models as special cases. We demonstrate the utility of the new space-time correlation model by clarifying the limitations of a widely accepted correlation model for MIMO fading channels. As another application, we quantify the impact of nonisotropic scattering around the user, on the capacity of a MIMO fading channel View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Spatio-temporal channel characterization in a suburban non line-of-sight microcellular environment

    Publication Year: 2002 , Page(s): 532 - 538
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB) |  | HTML iconHTML  

    This paper reports a spatio-temporal channel characterization of a suburban non-line-of-sight microcellular environment in which azimuth-delay profiles obtained by an experiment are compared with ray-tracing simulation. The results are statistically treated step by step to extract model parameters in order to characterize the spatio-temporal channel. The experimental results we obtain are used to improve the accuracy of the simulation process. We are able to obtain a very good agreement between the simulation and the experiment, with the exception of the exponential decay of the delay profile. The results presented can be directly used to implement the stochastic spatio-temporal channel model, based on the deterministic ray-tracing simulations View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Experimental analysis of the joint statistical properties of azimuth spread, delay spread, and shadow fading

    Publication Year: 2002 , Page(s): 523 - 531
    Cited by:  Papers (85)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (355 KB) |  | HTML iconHTML  

    Empirical results characterizing the joint statistical properties of the local azimuth spread (AS), the local delay spread (DS), and the shadow (slow) fading component are presented. Measurement data from typical urban, bad urban, and suburban (SU) environments have been analyzed. It is found that a log-normal distribution accurately fits the distribution function of all the investigated parameters. The spatial autocorrelation function of both AS, DS, and shadow fading can be modeled with an exponential decay function. However, for SU environments the spatial autocorrelation function is better characterized by a composite of two exponential decaying functions. A positive cross correlation is found between the AS and the DS, while both parameters are negatively correlated with shadow fading. All essential parameters required for the implementation of a simulation model considering the joint statistical properties of the AS, DS, and shadow fading are provided View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Small-scale fading for high-altitude platform (HAP) propagation channels

    Publication Year: 2002 , Page(s): 641 - 647
    Cited by:  Papers (33)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (287 KB) |  | HTML iconHTML  

    There has been a great interest in the development of high-altitude platforms, which are low cost stratospheric aircraft carrying payloads tailored for a wide range of applications in telecommunications and remote sensing. These platforms are capable of flying at altitudes ranging between 17 and 30 km, with a potential endurance of weeks to months, features that make them attractive for the provision of future personal communication services. This paper deals with the theoretical derivation of a channel model for the communication link between the platform and terrestrial mobile users or stations. In particular, we address the problem of modeling the small-scale fading effects. It is shown that the particular geometry of the propagation scenario leads to a specific model applicable to the stratospheric channel View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Physical optics and field-strength predictions for wireless systems

    Publication Year: 2002 , Page(s): 515 - 522
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (333 KB) |  | HTML iconHTML  

    Physical optics, or Fresnel-Kirchhoff theory, is often used for studies of particular problems in terrestrial radio-wave propagation. With efficient techniques of numerical integration, it can also be used effectively for routine predictions and for designing terrestrial wireless systems. A computer program of this type has been in use for several years. It is most useful in situations in which the base station (BS) antenna is above local clutter, and over areas large enough that ground cover can be characterized with categories such as "open," "forest," "dense residential," etc., rather than individual buildings. The main calculation is a marching algorithm that simulates diffraction over all the variations in terrain height along radials from the BS. A secondary calculation estimates the additional attenuation due to buildings and trees close to the mobile antenna. This part of the calculation is based on several parameters characterizing the local environment of the mobile antenna. Calculations are slow compared to many traditional methods, but are fast enough for routine use on a PC View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A physical model of the wireless infrared communication channel

    Publication Year: 2002 , Page(s): 631 - 640
    Cited by:  Papers (42)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (358 KB) |  | HTML iconHTML  

    A simple analytical model of the wireless infrared communication channel in indoor environments is presented. The infrared signal is modeled as the combination of a diffuse component and a line-of-sight (LOS) or direct component. For the diffuse component alone, the properties of the channel are found using Ulbricht's integrating sphere. When a LOS component is also present, the transfer function depends upon the Rician factor K given by the ratio of the electrical power in the LOS and diffuse signals after the detector. For small K, the transfer function shows notches down to low frequencies, but due to the nature of light never for zero frequency. We confirm that a K-factor ⩾13 dB is required also in infrared wireless links in order to support distortionless data transmission beyond 100 Mbit/s. Increasing the directivity at the receiver and/or at the transmitter improves the effective value of K. Here, we show that a moderate directivity will be sufficient for high-speed infrared communication in typical indoor scenarios View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Prediction of outdoor and outdoor-to-indoor coverage in urban areas at 1.8 GHz

    Publication Year: 2002 , Page(s): 496 - 506
    Cited by:  Papers (27)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (453 KB) |  | HTML iconHTML  

    A run-time efficient three-dimensional radio propagation prediction model is presented. The model allows mobile network operators to predict the outdoor and the outdoor-to-indoor coverage in dense urban areas using one general prediction model. It integrates almost all relevant propagation phenomena in dense urban areas with an accuracy comparable to the results of dedicated prediction models. The required high resolution building data is stored in vector as well as raster format. Depending on the terrain processing task, the format resulting in the shorter run-time is employed. A huge amount of measurements from the Global System for Mobile Communications 1800 network of E-Plus have been used to derive the heuristics and empirical correction factors included in the model. It is shown that the prediction accuracy can be improved significantly by considering vegetation effects and multipath propagation. Measurements justify multipath propagation only up to a distance of measurements from the base stations (BSs) in an dense urban environment. This is another source of significant run-time savings. Consequently, the prediction time of large areas decreases dramatically by neglecting multipath effects at these distances. A semiempirical building penetration extension is used to derive indoor predictions for each floor based on outdoor predictions at ground-level combined with a height gain model. An additional deterministic component is incorporated in case the BS and (parts of) the building are in line of sight. Preliminary tests show a sufficient match between the measurements and the outdoor as well as the outdoor-to-indoor predictions View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Use of cell-site diversity in millimeter-wave fixed cellular systems to combat the effects of rain attenuation

    Publication Year: 2002 , Page(s): 602 - 614
    Cited by:  Papers (26)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB) |  | HTML iconHTML  

    An examination of potential advantages of cell-site diversity with selection combining in the context of MM-wave fixed cellular systems is reported. The study involves simulation of converging radio links over weather radar images of the radar reflectivity factor, from which the specific attenuation of rain at 30 GHz is derived. The average correlation of attenuation on two converging links as a function of their angular separation is shown to indicate the potential benefits in the use of cell-site diversity, especially in heavy rain. Results show that diversity gain exhibits a dependence on angular separation θ in the general form of sink (θ/2). For links of identical lengths the model reduces to a root-sinusoidal shape (k=0.5), whereas links of unequal lengths lead to the ITU-R recommended model (k=1). Based on the sink (θ/2) model and observation of the length ratio of the links, a set of criteria for determining the benefit of cell-site diversity for a given subscriber location is proposed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Propagation characteristics for wideband outdoor mobile communications at 5.3 GHz

    Publication Year: 2002 , Page(s): 507 - 514
    Cited by:  Papers (64)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (549 KB) |  | HTML iconHTML  

    In this paper, empirical channel models and parameters are derived from the wideband measured data at 5.3 GHz in outdoor mobile communications. The path loss exponents and intercepts are obtained by using the least square method. The mean excess delay and mean root-mean-square (rms) delay spread are within 29-102 ns and 22-88 ns, respectively. The correlation distances and bandwidths are within 1-11 λ and 1.2-11.5 MHz, respectively, when the envelope correlation coefficients equal 0.7 in line-of-sight cases. These correlation values depend strongly on the base station antenna heights. The window length for averaging out the fast fading components is about 1-2 m for microcells and picocells. The multipath number distributions follow both Poisson's and Gao's distributions, but Gao's distribution is better in the high probability region. Large excess delays up to 1.2 μs and rms delay spread about 0.42 μs are found in the urban rotation measurements, where the receiver is close to a large open square View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

IEEE Journal on Selected Areas in Communications focuses on all telecommunications, including telephone, telegraphy, facsimile, and point-to-point television, by electromagnetic propagation.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Muriel Médard
MIT