Showing papers in "IEEE Transactions on Vehicular Technology in 2002"

A parametric model for the distribution of the angle of arrival and the associated correlation function and power spectrum at the mobile station

Abstract: One of the main assumptions in Clarke's classic channel model is isotropic scattering, i.e., uniform distribution for the angle of arrival (AOA) of multipath components at the mobile station. However, in many mobile radio channels we encounter nonisotropic scattering, which strongly affects the correlation function and power spectrum of the complex envelope at the mobile receiver. We propose the use of the versatile von Mises (1918) angular distribution, which includes and/or closely approximates important distributions like uniform, impulse, cardioid, Gaussian, and wrapped Gaussian, for modeling the nonuniform AOAs at the mobile. Based on this distribution, the associated correlation function and. power spectrum of the complex envelope at the mobile receiver are derived. The utility of the new results is demonstrated by comparison with the correlation function estimates of measured data.

Call admission control schemes and performance analysis in wireless mobile networks

Abstract: Call admission control (CAC) plays a significant role in providing the desired quality of service in wireless networks. Many CAC schemes have been proposed. Analytical results for some performance metrics such as call blocking probabilities are obtained under some specific assumptions. It is observed, however, that due to the mobility, some assumptions may not be valid, which is the case when the average values of channel holding times for new calls and handoff calls are not equal. We reexamine some of the analytical results for call blocking probabilities for some call admission control schemes under more general assumptions and provide some easier-to-compute approximate formulas.

Aeronautical channel modeling

Abstract: A class of aeronautical wide-band channel models is proposed, featuring parking and taxi environments, takeoff and landing situations, and en-route scenarios for ground-air and air-air links. Typical and worst case parameter sets are suggested, based on published measurement results and empirical data. The models are suitable for channel emulators that can be easily implemented on digital computers or in hardware and thus are useful for the validation of digital aeronautical links. A time-domain and frequency-domain implementation of such a channel emulator are derived, and results for a typical multicarrier system are presented. It is shown that the scenarios have distinguishable performance results depending on the underlying maximum ranges and shapes of the Doppler and delay spectra and the presence of a line-of-sight path. Finally, the degrading effects of intersymbol interference and intersubcarrier interference on the multicarrier signal are explained.

Semi-autonomous adaptive cruise control systems

Abstract: The concept of a semi-autonomous adaptive cruise control (SAACC) system is developed, which enjoys significant advantages over present day adaptive cruise control (ACC) systems in terms of highway safety and traffic flow capacity. The semi-autonomous systems combine the deployment advantages of autonomous vehicles with the performance advantages of fully automated highway systems (AHSs) in which vehicles operate cooperatively as a platoon. Unlike platoon systems, the semi-autonomous systems are immediately deployable on present day highways, where both manually driven and adaptive cruise controlled vehicles can coexist. Our theoretical results show that the proposed system is able to maintain smaller time gaps safely, is string stable, and is guaranteed to have smaller actuator inputs than a standard autonomous ACC system. The simulation results indicate that more accurate and smoother tracking, smaller time gaps, smaller control efforts, and increased robustness to vehicle dynamics are achieved by semi-autonomous control.

Planning effective cellular mobile radio networks

Abstract: This paper deals with the automatic selection and configuration of base station sites for mobile cellular networks. An optimization framework based on simulated annealing is used for site selection and for base-station configuration. Realistic path-loss estimates incorporating terrain data are used. The configuration of each base station involves selecting antenna type, power control, azimuth, and tilt. Results are presented for several design scenarios with between 250 and 750 candidate sites and show that the optimization framework can generate network designs with desired characteristics such as high area coverage and high traffic capacity. The work shows that cellular network design problems are tractable for realistic problem instances.

Angular power distribution and mean effective gain of mobile antenna in different propagation environments

Abstract: We measured the elevation angle distribution and cross-polarization power ratio of the incident power at a mobile station in different radio propagation environments at 2.15 GHz frequency. A novel measurement technique was utilized, based on a wideband channel sounder and a spherical dual-polarized antenna array at the receiver. Data were collected over 9 km of continuous measurement routes, both indoor and outdoor. Our results show that in non-line-of-sight situations, the power distribution in elevation has a shape of a double-sided exponential function, with different slopes on the negative and positive sides of the peak. The slopes and the peak elevation angle depend on the environment and base-station antenna height. The cross-polarization power ratio varied within 6.6 and 11.4 dB, being lowest for indoor and highest for urban microcell environments. We applied the experimental data for analysis of the mean effective gain (MEG) of several mobile handset antenna configurations, with and without the user's head. The obtained MEG values varied from approximately -5 dBi in free space to less than -11 dBi beside the head model. These values are considerably lower than what is typically used in system specifications. The result shows that considering only the maximum gain or total efficiency of the antenna is not enough to describe its performance in practical operating conditions. For most antennas, the environment type has little effect on the MEG, but clear differences exist between antennas. The effect of the user's head on the MEG depends on the antenna type and on which side of the head the user holds the handset.

Correlation and channel capacity of MIMO systems employing multimode antennas

Abstract: A novel way of exploiting higher modes of antennas as diversity branches in multiple-input-multiple-output (MIMO) systems is introduced. Essentially, antennas employing multiple modes offer characteristics similar to an antenna array, through multiple modes and using only a single element. The physical mechanism that yields different received signals is the fact that each mode has a different radiation pattern. Analytical expressions for the correlation between signals received by different modes are presented for a biconical and a circular microstrip antenna that employs higher order modes. It is found that the correlation is low enough to yield a significant diversity gain. Furthermore, the channel capacity of a MIMO system using a multimode antenna, i.e., an antenna employing multiple modes, is found to be comparable to the capacity of an array. Since only one element is needed, the multimode antenna offers several advantages over traditional arrays, and is an interesting antenna solution for future high capacity MIMO systems.

Principles of space-time array processing for ultrawide-band impulse radar and radio communications

Abstract: The emerging ultrawide-band (UWB) impulse technology has found numerous applications in the commercial as well as the military sector. The rapid technological advances have made it possible to implement (cost-effective, short-range) impulse radar and impulse-radio communication and localization systems. Array beamforming and space-time processing techniques promise further advancement in the operational capabilities of impulse radar and impulse-radio communications to achieve long-range coverage, high capacity and interference-free quality of reception. We introduce a realistic signal model for UWB impulse waveforms and develop the principles of space-time array processing based on the signal model. A space-time resolution function (STRF), a space-frequency distribution function (SFDF) and a monopulse-tracking signal are derived for impulse waveforms received by a self-steering array beamforming system. The directivity peak-power pattern and energy pattern of the beamformer are also derived. Computer plots of the STRF, SFDF and the beam patterns are obtained. The directivity beam patterns of impulse waveforms are sidelobe-free and, therefore, there is no need for sidelobe suppression via amplitude weighting of the array elements. Also, the resolution angle for the beam patterns is derived as a decreasing function of array size and frequency bandwidth. Electronic beamsteering based on slope processing of monopulse waveforms is described.

Partial zero-forcing adaptive MMSE receiver for DS-CDMA uplink in multicell environments

Abstract: Adaptive multi-user detection techniques for interference suppression in direct-sequence code division multiple access (DS-CDMA) systems have gained much attention since they do not require any information on interfering users. In the uplink of DS-CDMA systems, however, the base station receiver typically knows the spreading waveforms of the users within its cell but does not know those of the users in other cells. We propose a partial zero-forcing adaptive minimum mean squared error (MMSE) receiver for the DS-CDMA uplink utilizing the spreading waveforms known at the base station as well as training data. The proposed receiver first removes the intracell interference using a linear filter based on the knowledge of the spreading waveforms of the interfering users within the cell. Then the intercell interference remaining in the output of the linear filter is mitigated by adaptive MMSE detection. To speed up the convergence of the adaptive filter weights without loss of the steady-state performance, we develop a modified least mean square (LMS) algorithm based on the canonical representation of the filter weights. It is shown through analysis and simulation results that the proposed receiver improves the convergence speed and the steady-state performance.

Performance of handoff algorithm based on distance and RSSI measurements

Abstract: The performance of a proposed handoff algorithm based on both the distance of a mobile station to neighboring base stations and the relative signal strength measurements is evaluated. The algorithm performs handoff when the measured distance from the serving base station exceeds that from the candidate base station by a given threshold and if the measured signal strength of the adjacent base station exceeds that of the serving base station by a given hysteresis level. The average handoff delay and average number of handoffs are used as criteria for performance. Numerical results are presented to demonstrate the feasibility of the distance-based handoff algorithm, including results for an additional criterion based on relative signal strength. The proposed algorithm is compared with an algorithm based on absolute and relative signal strength measurements and with a solely distance-based algorithm. It is found that the proposed handoff algorithm performs well in a log-normal fading environment when the distance estimate error is modeled by wide-sense stationary additive white Gaussian noise.

Measurement of angular and distance correlation properties of log-normal shadowing at 1900 MHz and its application to design of PCS systems

Abstract: This paper investigates the correlation properties of shadow fading as a function of the angle between two PCS base stations over urban, light urban, and suburban terrain. Results from this study are relevant to the analysis of interference, handoff gain, and to various frequency planning applications in modern cellular and PCS systems. Using a significantly larger data set than previous experiments, we observed that on the average, the shadow fading components of the signals are not correlated, even at small angles. Our results contradict the conventional wisdom, as expressed in several papers, which says that there is relatively high correlation at small angles. Our results indicate that a mathematically simpler uncorrelated model for the relationship between signals from multiple base stations at small angles can be used in analysis tools. Distance correlation measurements computed by forming the autocorrelation function on a large number of data sets showed that the correlation distance of the shadowing process ranges from about 25 to 100 m.

Analysis of dynamic location management for PCS networks

Abstract: Location management is a key issue in personal communication service (PCS) networks. Performance analysis plays important roles in the implementation of location management methods and system design in PCS networks. Existing PCS networks have the home location registers (HLRs) and visitor location registers (VLRs) architecture for location management. Some interesting dynamic location management methods are proposed to improve the system performance of PCS networks. However, the existing performance analysis of the dynamic location management methods are too simple and not available for PCS networks with real HLR/VLR architecture. One of the reasons is the complexity and difficulty of the problem. In this paper, we challenge the problem and successfully establish a new analytical model available for the analysis of the important dynamic movement-based location management method for PCS networks.

A simple distributed PRMA for MANETs

Abstract: With the rapid development of Global Positioning System (GPS) technology and its applications, synchronization between terminals in mobile ad hoc environments becomes feasible at a low cost. Thus, slotted-channel-based medium access control (MAC) schemes like time division multiple access (TDMA) also become interesting for mobile ad hoc networks (MANETs). In this paper, we extend the classical centralized and slotted packet reservation multiple access (PRMA) scheme to a simple distributed PRMA (D-PRMA) as a MAC scheme for MANETs, with emphasis on voice application support. The major efforts of D-PRMA include 1) a simple slot reservation mechanism for voice traffic at the level of "talkspurt" without relying on any central entity and 2) a simple solution for the hidden and exposed terminal problems uniquely present in wireless ad hoc environments. The performance of D-PRMA has been investigated by analysis and computer simulations in comparison with IEEE 802.11. The results show that D-PRMA is much more suitable than IEEE 802.11 for voice application.

Using learning automata for adaptive push-based data broadcasting in asymmetric wireless environments

Abstract: Push systems are not suitable for applications with a priori unknown, dynamic client demands. This paper proposes an adaptive push-based system. It suggests the use of a learning automaton at the broadcast server to provide adaptivity to an existing push system while maintaining its computational complexity. Using simple feedback from the clients, the automaton continuously adapts to the client population demands so as to reflect the overall popularity of each data item. Simulation results are presented that reveal the superior performance of the proposed approach in environments with a priori unknown, dynamic client demands.

A real-time DOA-based smart antenna processor

Abstract: We designed, built, and tested a real-time processor for a direction-of-arrival-based smart antenna GSM 1800 base station with eight half-wavelength spaced antenna elements. Its processing steps include direction-of-arrival (DOA) estimation, user identification, tracking, beamforming, and signal reconstruction. We demonstrate that the accuracy of DOA estimation is not of primary concern, but the robustness is. This can be assessed by a new parameter, the estimation range. Tracking of reliable user DOAs only, increases the robustness against interference. Our tracking concept is compatible with frequency hopping. We quantify the benefits of smart antennas by the statistics of the gain in carrier-to-interference ratio (C/I) and in signal-to-noise ratio (SNR), both measured at the 90 or 99% levels with actual transmitted data. In an urban environment with large angular spread and overlap of user and interferer signals, the C/I gain is as high as 18 dB. Interferer nulling increases the C/I gain only slightly, but enhances robustness against angular spread, particularly if broad nulls are applied. Separating SNR gain in its contributions due to beamforming and diversity gives valuable insight into the way of operation. In uplink, the processor can exploit angular diversity. The entire suite of processing steps is done within less than 1 ms, demonstrating that sophisticated DOA-based smart antenna processing is feasible in real time. Our solution does not require any change in the GSM standard.

Adaptive asymmetric linearization of radio over fiber links for wireless access

Abstract: The biggest concern in the use of radio-over-fiber (ROF) links in wireless access is their limited dynamic range due to nonlinear distortion (NLD). In this paper, a higher order adaptive filter based nonlinearity compensation scheme is proposed. Pre-compensation is done for the downlink while post-compensation is done for the uplink to result in asymmetry with respect to complexity. This centralized signal processing is attractive in that it keeps the remote unit simple. Accurate measurements of ROF link parameters are not required with this approach because the filters are adapted from the distortion of the input/output base band signal. This technique also facilitates fast tracking of modifications and drifts in the link characteristics. Measurements and simulation results show that gradually saturating amplitude nonlinearity can be adequately linearized with some backoff from the clipping limit. A 42% backoff is required for pre-compensation to protect the laser while only a 16.7% backoff is required for post-compensation. Phase pre-compensation is accomplished with a higher accuracy than phase post-compensation.

A novel adaptive beamforming algorithm for antenna array CDMA systems with strong interferers

Abstract: Blind beamforming based on the maximum signal-to-noise ratio (MSNR) can improve the performance of an array system only when the processing gain of the given code-division multiple-access (CDMA) system is high enough such that the desired signal can become dominant after despreading (see Choi, S. and Shim, D., IEEE Trans. Veh. Technol., vol.49, p.1793-1806, 2000; Choi, S. and Yun, D., IEEE Trans. Antennas Propagat., vol.45, p.1393-1404, 1997). We consider a maximum signal-to-interference-plus-noise ratio (MSINR) beamforming. The MSINR performance criterion is chosen to deal with strong interferers effectively. It is shown that blind MSINR beamforming is possible by directly utilizing the input and output signals of correlators of the CDMA systems. In addition, we propose an adaptive beamforming algorithm at a lower computational complexity - about O(7.5N) - where N is the number of antenna elements of the array system. Simulation results are presented in various signal environments to show the performance of the proposed adaptive algorithm.

Modeling and efficient handling of handoffs in integrated wireless mobile networks

Abstract: We propose and analyze two handoff schemes without and with preemptive priority procedures for integrated wireless mobile networks. We categorize the service calls into four different types, namely, originating voice calls, originating data calls, voice handoff request calls, and data handoff request calls and we assume two separate queues for two handoff services. A number of channels in each cell are reserved exclusively for handoff request calls. Out of these channels, few are reserved exclusively for voice handoff request calls. The remaining channels are shared by both originating and handoff request calls. In the preemptive priority scheme, higher priority is given to voice handoff request calls over data handoff request calls and can preempt data service to the queue if, upon arrival, a voice handoff request finds no free channels. We model the system by a three-dimensional Markov chain and compute the system performance in terms of blocking probability of originating calls, forced termination probability of voice handoff request calls, and average transmission delay of data calls. It is observed that forced termination probability of voice handoff request calls can be decreased by increasing the number of reserved channels. On the other hand, as a data handoff request can be transferred from a queue of one base station to another, there is no packet loss of data handoff except for a negligibly small blocking probability.

Demand responsive services in hierarchical public transportation system

Abstract: An advanced public transportation system called the local initiative for neighborhood circulation (LINC) is proposed and the realization of its usage is investigated. LINC effectiveness and efficiency comes from its utilization of a transit-station-oriented system with elimination of present bus stops. LINC has three levels of services. Level 1 is the regional trunk line service with high-speed and high-capacity service provided by the regional transit authority. Level 2 is the intercommunity express bus service with frequent and reliable service provided by the metro transit system. Level 3 could have many forms to serve within the community and to/from level 1 or level 2 transit stations. Our study is limited to the dial-a-ride service, which operates door-to-door service as a public taxi, provided by small buses and/or vans. This paper will address the optimization problem of the dial-a-ride service. A genetic algorithm scheme is applied to its optimization and proper solutions are obtained as a result.

Performance analysis of generalized selection combining with threshold test per branch (T-GSC)

Abstract: We analyze the average bit error rate (BER) and outage probability performance of two types of conditional diversity combining schemes in which each branch signal-to-noise ratio (SNR) is tested against a fixed predetermined threshold and applied to the combiner only if its value exceeds this threshold. The two schemes, respectively referred to as absolute threshold generalized selection combining (AT-GSC) and normalized threshold generalized selection combining (NT-GSC), differ from one another only in the manner in which the threshold is chosen. Nevertheless, when operating over a generalized fading channel, the two schemes have a markedly different behavior as reflected in the numerical results presented. The analytical method taken to obtain these results follows the moment generating function approach originally proposed by the authors for analyzing the performance of more conventional diversity combining schemes (see Simon, M.K. and Alouini, M.-S., Proc. IEEE, vol.86, p.1860-77, 1998).

Authentication protocols for mobile network environment value-added services

Abstract: The secure provision of mobile computing and telecommunication services is rapidly increasing in importance as both demand and applications for such services continue to grow. This paper is concerned with the design of public key based protocols suitable for application in upcoming third-generation mobile systems such as the Universal Mobile Telecommunications Service. Candidate protocols are considered for the authentication of a mobile user to a value-added service provider with initialization of a mechanism enabling payment for the value-added service. A set of goals for such a protocol are identified, as are a number of generic attacks; these goals and attacks are then used to evaluate the suitability of seven candidate third-generation user-to-network authentication protocols. Many of these candidate protocols are shown to have highly undesirable features.

Bluetooth performance in the presence of 802.11b WLAN

Abstract: Both Bluetooth and 802.11b wireless communication technology are poised to make a significant impact in many applications. The complementary nature of the two technologies leads to applications enhanced by their collocation and simultaneous operation. Thus heightening the need for understanding the coexistence issues between the two technologies. A method was developed for evaluating the impact an 802.11b network will have on the Bluetooth piconet performance. A three step process was used in this development: characterize the 802.11b interference in a stationary environment, characterize the Bluetooth performance in the presence of a single 802.11b interferer and characterize the Bluetooth performance in an arbitrary 802.11b network environment. Empirical results were used to develop and substantiate the analytical model. The root-mean-square (RMS) difference between the single interferer empirical test results and the analytical model results was 2%. Analysis results, based on a specific range of radio propagation parameters and 802.11b network parameters, are presented.

The Jakes fading model for antenna arrays incorporating azimuth spread

Abstract: A new method for simulating the multiplicative fading of the narrow-band, flat wireless channel for antenna array receivers is presented. The new approach produces a set of fading waveforms, one waveform associated with each receiver element, in which the waveforms are appropriately correlated to take into account the spread, or dispersion, in the azimuth (arrival angle) of the received signal. The new method is an extension of the Jakes (1974) method of simulating fading in which the appropriate correlation of the set of waveforms is accomplished by directly considering the azimuth of scatterers in a particular distribution about the mobile transmitter. The models used for this cluster of scatterers are a ring and a disk of scatterers. Further modifications of the disk model permit the generation of fading waveforms which are correlated in a manner which reflect actual field measurements of azimuth dispersion. Analytical correlation of these models is reviewed for purposes of verification with the waveforms generated by the method.

Wide-band CDMA for the UMTS/IMT-2000 satellite component

Abstract: This paper describes the main aspects relevant to the development of a third-generation radio transmission technology (RTT) concept identified as satellite wide-band CDMA (SW-CDMA), which has been accepted by the International Telecommunications Union (ITU) as one of the possible RTTs for the satellite component of International Mobile Telecommunications-2000 (IMT-2000). The main outcomes of the extensive system engineering effort that has led to the above ITU RTT are described. In particular, we address propagation channel characteristics, satellite diversity, power control, pilot channel, code acquisition, digital modulation and spreading format, interference mitigation, and resource allocation. Due to its similarity with respect to the terrestrial W-CDMA proposal from which it is derived, the SW-CDMA open air interface solution is described briefly, with emphasis only on the major adaptation required to best cope with the satellite environment. Quantitative results concerning the physical-layer performance over realistic channel conditions, for both forward and reverse link, are reported. A system capacity study case for a low-Earth-orbit constellation is also provided.

Performance analysis of adaptive interleaving for OFDM systems

Abstract: We proposed a novel interleaving technique for orthogonal frequency division multiplexing (OFDM), namely adaptive interleaving, which can break the bursty channel errors more effectively than traditional block interleaving. The technique rearranges the symbols according to instantaneous channel state information of the OFDM subcarriers so as to reduce or minimize the bit error rate (BER) of each OFDM frame. It is well suited to OFDM systems because the channel state information (CSI) values of the whole frame could be estimated at once when transmitted symbols are framed in the frequency dimension. Extensive simulations show that the proposed scheme can greatly improve the performance of the coded modulation systems utilizing block interleaving. Furthermore, we show that the adaptive interleaving out performs any other static interleaving schemes, even in the fast fading channel (with independent fading between symbols). We derived a semi-analytical bound for the BER of the adaptive interleaving scheme under correlated Rayleigh fading channels. Furthermore, we discussed the transmitter-receiver (interleaving pattern) synchronization problem.

Angle of arrival statistics for a 3-D spheroid model

Abstract: In this correspondence, a three-dimensional (3-D) geometric model is considered to simultaneously describe angular arrival of multipath waves in the azimuth and elevation planes. Closed-form expressions for the probability density functions (pdfs) in the angles are provided as seen from the mobile station (MS) and base station (BS). A closed-form expression is also provided for the root mean square (rms) angular spread in the azimuth plane as seen from the BS. The model is suitable in a macro-cellular environment with a low MS antenna and an elevated base station antenna, where significant scatterers are distributed about the former.

Optimal binary training sequence design for multiple-antenna systems over dispersive fading channels

Abstract: Accurate and efficient channel estimation is important in multiple-antenna communication systems in order to effectively reduce the mutual interference among different transmitting antennas. For a nondispersive channel that is modeled by a single tap for each transmitting and receiving antenna pair, the well-known Hadamard sequences can be applied to estimate the channel coefficients. However, for a dispersive channel that has multipath problem and is modeled by multiple taps, the optimal sequences must have both good autocorrelations and cross correlations. The existence of binary sequences with such good property is an open problem. In this paper, we devise an algorithm to find these sequence sets. These codes can be applied in multiple-antenna systems.

Deterministic channel modeling and performance simulation of microcellular wide-band communication systems

Abstract: To evaluate the performance of future microcellular IMT-2000 modems, simple physical models are required, so that a number of system characteristics, such as the signal bandwidth, the antenna beamwidth, or the base station height can be accounted for at a limited computational cost. This paper describes a deterministic three-dimensional electromagnetic model, which allows simulation of the radiowave propagation for microcellular wide-band communication systems in urban areas. The model is based on a UTD ray-tracing tool and makes use of an improved mirror method. Simulated power-delay profiles are plotted against measured power-delay profiles recorded at 1.87 GHz in a street of Louvain-la-Neuve, Belgium, by means of an 80-MHz channel sounder. Despite several discrepancies, a satisfying matching is found considering three orders of reflection and single diffraction. Predictions of rms delay-spread accounting for the sounder limited bandwidth are presented. Finally, simulated and measured channels are also compared through the resulting performance of a typical IMT-2000 service in the presence of multiple access interference.

Methods for modeling of specified and measured multipath power-delay profiles

Abstract: Five fundamental methods are proposed to model the multipath power-delay profile of frequency-selective indoor and outdoor wireless channels. Three of them are new, and the other two are well known, but their performance, however, has not been studied in detail up until now. All procedures are universally valid so that they can be applied to any specified or measured multipath power-delay profile. The performance of the proposed methods is investigated with respect to important characteristic quantities such as the frequency correlation function (FCF), average delay, and delay spread. The method found to perform best is the so-called L/sup P/-norm method (LPNM). This procedure is applied to measurement data of multipath power-delay profiles collected in different propagation environments. It is shown that the realization complexity of tapped-delay line-based simulation models for fading channels can be reduced considerably by using the LPNM. This is a great advantage for the development and specification of channel models for future wireless systems.

Measurement of the impulsive noise environment for satellite-mobile radio systems at 1.5 GHz

Abstract: Noise amplitude distribution measurements relevant to satellite-mobile radio systems are reported. The rationale for the measurements is outlined and the choice of measurement parameters justified. The measurement equipment and measurement methodology are described in detail. Results characterizing the elevation angle distribution of impulsive noise are presented for rural, suburban and urban environments and also for an arterial road (U.K. motorway) carrying high density, fast moving traffic. Measurements of the levels of impulsive noise to be expected in each environment for high- and low-elevation satellite scenarios using appropriate antenna configurations are also presented.