Abstract: We show that realistic multipath infrared channels can be characterized well by only two parameters: optical path loss and RMS delay spread. Functional models for the impulse response, based on infrared reflection properties, are proposed and analyzed. Using the ceiling-bounce functional model, we develop a computationally efficient method to predict the path loss and multipath power requirement of diffuse links based on the locations of the transmitter and receiver within a room. Use of our model is a simple, yet accurate, alternative to the use of an ensemble of measured channel responses in evaluating the impact of multipath distortion.

Abstract: A level of automated adjustment of system organization parameters in a wireless communication system is provided by determining the parameter settings using a characterization of signal propagation of the system's coverage area. This characterization is based on measurements of path loss-related characteristics by the system's base stations and wireless terminals operating throughout the coverage area. An exemplary path loss-related characteristic is path loss as determined by measuring received signal strength (RSS) at wireless terminals based on signals transmitted at known powers by a plurality of the system's base stations. It is possible for the wireless terminals to take measurements while operating in the coverage area, whether idle or during communication with the system, and for such terminals to be associated with the system's subscribers. A resulting characterization of signal propagation in the coverage area based on the measured path loss-related characteristic can then be used to determine a variety of parameter settings including base station transmission power settings, wireless terminal access parameters, neighbor lists, sets of base stations that can reuse channels and base station transmission power settings when base stations are added to or removed from the system.

Abstract: This paper presents a three-dimensional (3-D) propagation model for path-loss prediction in a typical urban site, based on geometrical optics (GO) and uniform theory of diffraction (UTD). The model takes into account numerous rays that undergo reflections from the ground and wall surfaces and diffraction from the corners or rooftops of buildings. The exact location of the reflection and diffraction points is essential in order to calculate the polarization components of the reflected and diffracted fields and their trajectories. This is accomplished by local ray-fixed coordinate systems in combination with appropriate dyadic reflection and diffraction coefficients. Finally, a vector addition of the received fields is carried out to obtain the total received field strength and, subsequently, the path loss along a predetermined route. The model computes the contributions of various categories of rays, as selected, in a flexible manner. Several results-path loss versus distance and power-delay profile-are given, and comparisons with measured data are presented.

Abstract: We provide a general analytical framework for the computation of the interference statistics in mobile radio cellular systems. This approach, which takes into account log-normal shadowing, distance path loss, best cell site selection and power control based on signal strength, applies to various cellular environments, including narrowband systems (e.g., IS-54 and Group Special Mobiles GSM) and code-division multiple-access (CDMA) systems. Some examples of application are provided.

Abstract: The present wide-band propagation model based on uniform geometrical theory of diffraction (UTD) for cellular mobile radio communications includes two major contributions. First, a UTD-based narrow-band channel transfer function containing both the diffracted electric field and the reflection of diffracted electric fields is derived. Not only is it an important element of the wide-band modeling method, but it also leads to a total path-loss prediction model verified by comparisons with previously published theoretical and experimental results. In particular, the distance for horizontal placement on the street allows one to calculate the ray-path length difference (used in wide-band modeling) for the diffracted field and the reflection. Second, new refinements (including a number of explicit-form expressions to an existing method experimentally confirmed, simulating wide-band radiowave propagation for rural environments including terrain profiles) are added, making it applicable here. The method generates the time-domain path loss, wide-band path loss, and the relative power in the frequency domain. The time-domain path loss physically interprets and reasonably predicts the power delay profiles. The presence of this and similar power delay profiles, as well as the behavior of the relative power in the frequency domain, has been confirmed by existing wide-band propagation measurements. The value of the wide-band path loss is of the order of the total path loss at the carrier frequency.

Abstract: A lattice Boltzmann model which simulates and predicts, on a massively parallel computer, wave propagation in urban environments is presented. This technique takes into account complicated boundary conditions. Two-dimensional simulations are performed starting from a city map and a renormalisation scheme is proposed to extend the results to three dimensions and adjust the wave length. The method, which is simple and easy to implement, provides good path loss predictions when compared with in situ measurements.

Abstract: Transmitter diversity is an attractive means for improving the performance of the downlink in a cellular system. This paper investigates one of these methods, referred to as antenna hopping, which consists in transmitting consecutive bursts of information on different antennas. Provided that the antenna branches are exposed to different multipath fading, a gain is achieved. Results from simulation of the GSM TCH/FS (full rate speech channel) reveal that the gain of hopping on two uncorrelated antennas is 2.9 dB for low speed terminals in an urban environment, and 5.4 dB for an indoor environment with semi-stationary users. The maximal gain is shown to be reduced at high cross-correlation and difference in path loss between the antenna branches. Antenna hopping combined with frequency hopping is shown to further enhance performance. With antenna hopping on two antennas, the maximal gain can be obtained by using frequency hopping on only 4 frequencies instead of 8 without antenna hopping. Finally, a comparison is made with delayed transmitter diversity, which is shown to have no essential advantages over antenna hopping at low terminal speed, which is the situation where diversity is really needed.

Abstract: A method is disclosed whereby a cellular network's BA lists are modified so that the mobile terminals (12) in the network (10) can measure downlink interference on predetermined BCCH frequencies. These measurements can be made in all cells where the mobile terminals (12) are located and then reported back to the base station (20). The base station (20) maps the reported measurements to corresponding cells, and uses the mapping to produce a cell-to-cell interdependency matrix. For the preferred embodiment, the matrix describes the difference in path loss between cells. This path loss information can be used to derive downlink C/I or C/A ratios between cells (or combinations of those ratios) and thus an estimate of the downlink reference in the frequencies assigned to the same cells. Consequently, the downlink interference in the network can be taken into account when new frequencies are to be selected for each cell, which can be used to increase the overall quality of the network (in terms of the C/I).

Abstract: The Character of Land-Mobile Radio Signals. Probability Distributions. Parameter Estimation in Rayleigh Fading. Coverage Relations. Specific Coverage Applications. Verification of Coverage. Path Loss Models. Noise Considerations. Link Budgets. Automatic RF Layout of Multisite, Frequency-Reuse Radio Systems. Appendices.

Abstract: Experiments of 94-GHz millimeter-wave propagation were carried out in indoor channels, where the propagation path loss and multipath fading are investigated. The results show that the path-loss exponents in the line-of-sight (LOS) and obstructed (OBS) channel are 1.2-1.8 and 3.6-4.1, respectively. The received power of the OBS path is attenuated significantly as compared with that of the LOS path, thereby requiring an additional link-budget margin as well as battery power. In this paper, the use of an artificial reflector is also suggested under OBS conditions in order to avoid significant propagation loss, and then, a comparative study is conducted.

Abstract: Field strength measurements were conducted at VHF and UHF for different base station antenna heights in the south Indian coastal zones in urban, sub-urban, quasi-open and open regions. These experimentally observed values are compared with different prediction methods like Hata, ITU-R, Blonquist & Ladell, Egli, and Tbrahim & Parsons. The results showed that in sub-urban and urban regions Hata's method gave reasonable agreement with the observed values and in the open region gave better agreement at 440 MHz than at 150 MHz. All the other methods deviated appreciably from the observed values.

Abstract: A method for detecting inequality in path balance in a cellular telephone system including the steps of providing data describing measured signal strength of signals received at a mobile unit and at a cell site in the absence of interference at a plurality of points describing the entire system; providing data describing measured signal strength of signals transmitted from each cell and from the mobile unit in the cellular telephone system; accumulating and averaging the data describing measured signal strength of signals received at the mobile unit and at the cell site to eliminate path loss variances between points and the cell site; selecting data describing measured signal strength of signals received at a mobile unit with path loss variances eliminated, data describing measured signal strength of signals transmitted from the mobile unit, data describing measured signal strength of signals received at a cell with path loss variances eliminated, data describing signal strength of signals transmitted from each cell for each point of the system; utilizing the selected data for each point to provide measures of the difference between the strength of signals on each path between each point and each cell; comparing the difference on each path between a point and a cell to other differences between the point and the cell; and changing cell characteristics where a difference on any path between a point and a cell is significantly different than any other difference between the point and the cell.

Abstract: A power-law path-loss model for indoor communications at 1.8 GHz is examined. In it, the exponent of the distance is treated as a random variable and its behaviour studied through experiments conducted under various propagation conditions in different buildings. The effects of random human traffic in the propagation channel, as well as those of antenna polarization are also experimentally studied. The statistical behaviour of the exponent and its fitting to several distribution functions, in particular Weibull, Nakagami and gamma ones, are also reported. By using the proposed model, new, simple and efficient instruments can be developed as an aid for the estimation of the power budget of indoor wireless communication systems.

Abstract: An advanced LOS (line-of-sight) path loss model with the characteristics of a real urban environment is proposed. Good results are obtained by using a two-path model together with shadowing caused by obstacles that would appear in an actual urban environment and rising reflection points caused by vehicular traffic. By applying the model in the urban environment, microcellular path loss can be predicted from the UHF to microwave bands. Measurements were performed using two different frequencies (457.2 MHz and 10.7 GHz) and two different BS antenna heights (3 m and 24 m).

Abstract: A new uniform-theory-of-diffraction- (UTD-) based approach for cellular-mobile-radio-propagation modelling is presented. Buildings are represented as conducting halfplanes or screens, and the model includes the effect of building-height variation along all intervening screens between base station and mobile. The proposed model has low computational complexity and could be applicable to small urban cells over regular terrain, with buildings of nonuniform height. It is shown that results from the model are in very close agreement with experimental observations, and that they accurately predict observed trends in the dependence of path loss and its variability on frequency, range, building-height variation and screen spacing.

Abstract: A general three-dimension theoretical model is developed to predict the path loss of UHF radio propagation through floors in a multifloored building. The computed propagation loss is compared with the measured value of 900 MHz, 1.4 GHz, 1.9 GHz, and 2.44 GHz and gives a reasonable agreement. It is found that the floor, lateral beams and the walls around the receiver are the major construction features to affect the estimation of the penetration loss through floors.

Abstract: PN offset planning in IS-95 based CDMA systems is systematically addressed in this paper. The minimum reuse distance for the same pilot PN offset is derived based on pilot signal strengths. The reuse distance is a function of receiver sensitivity, propagation path loss, system configuration, search window size and hand-off parameters. It is found that the required reuse distance decreases from six times of cell radius to one cell radius, when the path loss slope increases from 20 to 50 dB/decade. The minimum pilot offset interval between two adjacent base stations is a function of propagation delay spread, hand-off parameter settings and cell distance difference. The minimum pilot separation between two adjacent cell sites will increase when the hand-off area increases. Several PN offset aliasing cases in the CDMA system deployment are discussed. Pilot PN planning strategy is also addressed. System deployment demonstrates that the established criteria are sufficient to avoid the pilot PN offset ambiguity.

Abstract: A new model for path loss in radio systems is proposed, which combines the individual segment approach based on varying propagation constants into a single closed form expression. Before this work, the propagation models used examined each propagation segment individually. This closed form expression is more useful than prior models in performing near-far system analyses. This new model is based on concepts drawn from frequency response analysis used in the circuits and control communities. After showing that the general form of a frequency response fits the data shape of a path loss propagation study, the mathematics are refined to effect a close match with measured data. The applicability of this model to signal strengths that increases with distance, such as emerging from a shadow, is demonstrated.

Abstract: Scattering, diffraction, and attenuation of UHF wave propagation in the receiver near range (RNR) may cause significant additional path loss. Wave-propagation models for rural areas consider mainly the influence of topography and often ignore the effects due to land usage in the vicinity of mobile receivers. In some models, this path loss is accounted for either by empirical corrections or by additional knife edges. In this paper, new ray optical approaches for the calculation of the additional path loss for receiver sites within forested and suburban environments are presented. Typical macro situations are defined to describe the RNR. For urban areas, the additional path loss is determined by means of the uniform theory of diffraction (UTD), whereas in forested areas, a lateral wave-propagation approach is used. The resulting RNR model is tested in an operating global system for mobile communication (GSM) network. The results show good agreement with both wide- and narrow-band measurements.

Abstract: This paper presents a two-dimensional propagation model for microcellular local, personal, and mobile communication for the case when both antennas, receiver and transmitter, are located below rooftop level in an urban crossing-street situation. The model of crossing broken waveguides with randomly distributed buildings (screens) and gaps between them (slits) is considered as a model of an urban area with a rectangular grid pattern of streets. The average field intensity attenuation at the street level and coverage effects are investigated taking into account multireflection from the building walls and multidiffraction from the building edges. The theoretical predictions were verified by path loss measurements obtained by the communication group of Tadiran Telecommunication. The comparison shows good agreement with experimentally found field intensity loss at the urban street level and redistribution of field energy at the intersections of streets in an urban area with rectangular grid plan streets.

Abstract: While originally planned for indoor use, more and more outdoor applications of DECT (Digital Enhanced Cordless Telecommunication) systems are emerging. In this paper a new wave propagation model based on imaging theory is introduced, which is especially adapted for low base station antenna heights. Comparisons with measurements and other ray tracing methods are used to evaluate the prediction accuracy and computational complexity. The advantages of ray optical models for the planning of outdoor DECT systems are demonstrated by path loss and delay spread predictions. Angle of transmission and angle of arrival diagrams are evaluated to optimize the coverage area using directive antennas.

Abstract: Macroscopic diversity provides two or more independent copies of the transmitted signal which fade in an uncorrelated manner. The signals can be combined to fight against shadowing but also against fast fading avoiding the use of two antennas per site (microdiversity). It is suggested in this paper that macrodiversity can provide all the necessary fading protection (against fast as well as slow fading) in microcellular networks where the density of antennas is high. This paper investigates the performance of macrodiversity versus microdiversity from the radio coverage point of view. Two and four port combining are considered, firstly for a Rayleigh fading environment and later with a more elaborate microcellular channel model that includes Rician statistics for the received signal envelope, dual-slope path loss model and lognormal shadowing. The results show that macrodiversity is an effective fading countermeasure in microcellular environments. This work is motivated for the concept of a radio fibre microcellular network where optical fibre links are used for RF signal distribution from a central controller to remote antennae at cellsite. In these systems low-cost and compact radio access ports can be deployed anywhere. Therefore the question is how to obtain maximum radio coverage with minimum number of ports using diversity techniques.

Abstract: The work physically models wide-band radio propagation for urban line-of-sight (LOS) micro-cellular mobile and personal communications, including two contributions. First, a more explicit narrow-band channel transfer function for a six-ray model is presented. Second, the corresponding wide-band propagation characteristics are calculated, by extending an existing and validated method originally for rural environments and making it applicable to urban LOS micro-cellular environments. These characteristics are described by time-domain path loss, wide-band path loss, and relative power in frequency domain. Comparisons of these parameters with results calculated by using two-ray model are presented, since the experimental validation of the entire wide-band modeling for two-ray model was made previously. The time-domain path loss interprets power-delay profiles. The wide-band path loss is on the order of narrow-band path loss at a carrier frequency. The relative power in frequency domain ranges a finite bandwid...

Abstract: An investigation was carried out into how singly distributed trees on a hilltop in a radio path would affect the excess propagation loss. The results from measurements performed on vegetation attenuation and scatter on both in and out of leaf states at 20 GHz are presented and discussed.

Abstract: This paper addresses the feasibility of spectrum overlay of IS-95 over the GSM system. A simulation methodology has been adopted to ascertain the behaviour of the narrow band IS-95 and GSM system when using the same frequency spectrum, geographic region and time. This study is exploratory in nature and the IS-95 and GSM systems that are modelled, are based on the specifications provided in the GSM and IS-95. A hybrid model is developed to assist in writing a simulation program, taking into account the cellular parameters such as fading, path loss etc. and system specific parameters such as frame structure, channel allocation, sectorisation, discontinuous transmission, power control etc. The depth of the frame structure for each system is selected, that is enough for the power control and slow frequency hopping (for GSM) to work properly. The performance is computed in terms of received interference energies at a burst level. A burst corresponds to a transmission, on a time slot for GSM, and on a power control group for IS-95. Threshold erasure rates are defined for the IS-95 and GSM system and are compared with recorded erasure rates obtained via simulation. Constant receiver power control for GSM and E/sub b//I/sub o/, balancing control for IS-95 were used. It is then shown that due to the behaviour of the power control schemes, the systems can not co-exist fruitfully.

Abstract: A system is tested for jamming resistance by supplying a simulated jammingignal. The simulated jamming signal is produced by calculating a propagation path loss in the terrain between the system under test and a location where the jammer would be, predicting a jamming level in accordance with the propagation path loss, and generating a simulated jamming signal. The simulated jamming signal is supplied to the antenna port of the system under test. The testing does not require the use of either a real jammer or a pilot signal generator at the location where the jammer would be.

Abstract: An easy-to-use DTR model combined with a patched-wall model is proposed to predict the path loss for out-of-sight propagation on a single floor through interior walls. The model demonstrates an accurate prediction, and iserified by comparison of the predicted path loss with the measured one of 2.44-GHz radio propagation at four different sites. Q 1997 John Wiley & Sons, Inc. Microwave Opt Technol Lett 14, 56)59, 1997.

Abstract: The capacity of a fast fading channel with a Gaussian signal is analyzed using a simple block-wise fading model. We conclude that, the capacity degradation due to the high fading rate is small, and the fading degradation compared with a static channel is also very small, so in most cases of mobile communications, we need only consider the path loss and the shadowing effect.

Abstract: Two-way time spreading and path-loss measurements were collected in water 100 m deep, off the coast of Nova Scotia. Data were collected at frequencies of 20-22 kHz, 27-29 kHz, and 35-37 kHz using linear FM pulses 0.160 s in duration. The source-receiver was an anchored, high-frequency active sonar, and the target was a free-drifting echo repeater. Sonar and target positions were recorded using a portable tracking range. In the paper, two-way time spreading and path loss measurements are compared with modeled estimates obtained using an enhanced version of the generic sonar model (GSM). The GSM estimates of time spreading due to multipath propagation compare favorably with the experimental data. The model indicates that the path loss for individual eigenrays was extremely sensitive to fluctuations in the sound-speed profile. This led to substantial variation in the model output depending on the choice of profile. In place of the model, an empirical estimate of path loss was computed from the data. We obtained a two-way spreading loss of 2[18.4log/sub 10/(R)] where R is the range from sonar to target. The data were also used to compute the standard deviation of the received echo intensity at each frequency. The standard deviation was computed two different ways. First it was computed using the peak echo level from each of the pulses at a given frequency. Then, it was computed from the total energy received from each of the pings. At all frequencies, the standard deviation was 1-2 dB lower when computed from the total received energy.