Abstract: Preface. Acknowledgments. 1. Introduction. Fundamentals. Overview of UWB. A Brief History of UWB Signals. Types of UWB Signals. Regulatory, Legal, and Other Controversial Issues. What Makes UWB Unique? Time Domain Design. Impact of the Antenna. Propagation and Channel Models. Transmitter and Receiver Design. Difficulties in Using DSP Technology. Networking Issues. Future Directions. The I-UWB System Model. Overview of the I-UWB System. Pulse Shapes. Modulation Schemes. MultipleAccess Schemes. Receiver Decision Statistic. The MC-UWB System Model. Overview of the MC-UWB System. OFDM UWB. Overview of the Book. 2. Channel Measurement and Simulation. Introduction. Measurement Techniques. Time Domain Measurement Techniques. Frequency Domain Measurement Techniques. Measurement Results. Typical Results for Time Domain Measurements. Typical Results for Frequency Domain Measurements. The Role of Antennas. Impact of Building Architecture and Properties of Building Materials. Electromagnetic Simulation of UWB Propagation in Indoor Environments. Simulation of Transmitting and Receiving Antennas. Simulation of the UWB Channel. Organization of the Electromagnetic Simulator. Comparisons of Measurement and Simulation Results. Summary. 3. Channel Modeling. Introduction. What's Different about UWB? Large-Scale Channel Modeling. Free-Space Path Loss Modeling: The Friis Transmission Formula. Path Loss Modeling for Non-Free-Space Environments. Frequency Dependent Models. Partition Dependent Approaches. Large-Scale Modeling Studies. Antenna Impact on Large-Scale Modeling. Better than Free-Space Propagation. Receiver-Dependent Path Loss Models. Shadowing. Link Budget Calculations. Small-Scale Channel Modeling. Statistical Modeling of the Channel Impulse Response. Saleh-Valenzuela Model. -K Model. Single Poisson Model. Modified Poisson Model. Split-Poisson Model. Effect of Model Parameters. Stochastic Tapped-Delay Line Model. Amplitude Statistics. Summary of Measurement Campaigns and Modeling Efforts. Spatial Behavior and Modeling of UWB Signals. Introduction. Spatial Fading. Spatial Fading of Signal Components. Spatial Correlation. A Two-Dimensional Channel Model for UWB Indoor Propagation. Impact of Frequency Distortion on Discrete Channel Modeling. The CLEAN Algorithm. Impact of Frequency Dependent Distortion. Impact of Reflections. Summary. 4. Antennas. Basic Properties of Antennas. Reciprocity and Antenna Effective Length. Directivity, Gain, and Related Definitions. A Link Model Using S-Parameters. Link Budget Concepts. Fundamental Limits of Antennas. Antenna Measurements and Modeling in the Time Domain. Basic Responses. UWB Performance. Frequency and Time Relationships. Pattern Concept in Time. Time Domain Modeling (A Minimal Approach). Transient Responses of Scatterers. Summary. 5. Transmitter Design. I-UWB Signal Generators. Avalanche Pulse Generators. Step Recovery Diode Pulse Generators. Tunnel Diode Pulsers. Pulse Circuits Suitable for Integrated Circuits. Modulators. I-UWB Transmitters. TH-PPM and TH-(A-PAM) UWB Signals. OOC-PPM UWB Signals. DS-UWB Signals. Transmitter Reference (TR) UWB System. MC-UWB Transmitters. CI-UWB Signals. FH-UWB System. OFDM-UWB System. Spectral Encoded UWB Communication System. Summary. 6. Receiver Design Principles. I-UWB - RadioReceivers. System Model. Threshold/Leading Edge Detection. Correlation Detection (CD) Receivers. RAKEReceivers. Multi-User Detection (MUD) UWB Receivers. Hybrid RAKE/MUD UWB Receivers. Other I-UWB Receivers. Autocorrelation Transmitted Reference (TR) UWB Receiver. Synchronization and Timing Issues. Digital I-UWB Implementation. Example of IEEE Proposed Standards for PPM and DS-Based UWBReceivers. MC-UWBReceivers. Carrier Interferometry (CI) UWB Receiver. Frequency Hopped (FH) UWB Receivers. OFDM-UWBReceivers. Example on IEEE Proposed Standard for MC and OFDM-Based UWB Receivers. Spectral Encoded UWB Communication System. CaseStudy: Improving Range of UWB Using RAKE Receivers. GSC(N, L)withIndependent but Nonidentically DistributedFading Statistics. PMRC(N, L)withIndependent but Nonidentically DistributedFading Statistics. GSC(N, L)withEqually Correlated Nakagami-m FadingStatistics. Summary. 7. On the Coexistence Of Uwb and Narrowband Radio Systems. Introduction. Interference of UWB on NB: Waveform Analysis. UWB Pulse Model. Effect of NB Receive Filter. BER Analysis. Time-Hopped Case. Simulation Results. Aggregate UWB Interference Modeling. Received Power. Asymptotic Pdf of Aggregate Noise. Amplitudes: Aggregate Pdf. Bernoulli and Poisson Models. Simulation Examples. Interference Analysis: NB on UWB. Interference Analysis: UWB on UWB. Summary. 8. Simulation. What's Different about UWB SystemSimulations? Direct/Quadrature Signal Decomposition. Model Development for UWB Systems. UWB Simulation Development Challenges. Developing a Simulation. Simulation Methodologies-A Brief Review. Monte Carlo Simulation Techniques. Semi-Analytic Simulation Techniques. Discrete Event Simulation Techniques. Multicarrier UWB (MC-UWB) Simulation. UWB Component Simulation. UWB Pulse Generation and Modulation. Signal Ampli?cation. Simulation of Antenna Effects. Simulation of UWB Channels. Summary. 9. Networking. How Is UWB Networking Different? UWB Physical Layer Issues. Data Link Layer Design. Objectives of the Data Link Layer. Contention-Based Medium Access Control. ChannelPartition Medium Access Control. MultipleAccess Protocols for UWB Networks. Forward Error Correction and Automatic Repeat Request. UWB Multiple Hop Ad Hoc Networks. Hierarchical Network Topologies. Flat Network Topologies. Other Networking Issues. TCP Performance in a Wireless Environment. Quality of Service Management. Summary. 10. APPLICATIONS AND CASE STUDIES. Specialized Applications for UWB Signals. Applications. High Resolution Radar Applications. Communications Applications. Location Aware Communications Applications. Channel Sounding Applications. Case Studies. XtremeSpectrum Incorporated (XSI)/Motorola Trinity Chipset. Time Domain Corp-PulsON Chipset. Multispectral Solutions Incorporated (MSSI). Aether Wire and Location Localizers. 802.15.3a. 802.15.4a Devices. Summary. Appendix A. Range Analysis of UWB Signals Using Time of Arrival. Appendix B. UWB Standards for WPANs. IEEE 802.15.3/3a MAC. IEEE 802.15.3a PHY. MB-OFDM PHY. DS-UWB PHY. Summary. Appendix C. UWB Regulations. FCC. World. About The Editor. About The Authors. Index.

Abstract: In this paper we explore the idea of using cognitive radios to reuse locally unused spectrum for their own transmissions. We impose the constraint that they cannot general e unacceptable levels of interference to licensed systems on the same frequency. Using received SNR as a proxy for distance, we prove that a cognitive radio can vary its transmit power while maintaining a guarantee of service to primary users. We consider the aggregate interference caused by multiple cognitive radios and show that aggregation causes a change in the effective decay rate of the interference. We examine the effects of heterogeneous propagation path loss functions and justify the feasibility of multiple secondary users with dynamic transmit powers. Finally, we prove the fundamental constraint on a cognitive radio's transmit power is the minimum SNR it can detect and explore the effect of this power cap.

Abstract: The effect of two different antenna types on radio propagation in ultrawideband (UWB) on-body channel measurement are analyzed. Statistical path loss parameters and time domain channel characteristics [mean delay and root mean square (rms) delay spread] are extracted from measurement data. Reduction in rms delay spread is experienced when using printed horn shaped self-complementary antennas (HSCA) for specific body area links in comparison to monopole-like omnidirectional antennas, e.g., planar inverted cone antennas (PICA). Results show that the hybrid use of different type UWB antennas can effectively improve channel behavior in body-centric wireless networks.

Abstract: Methods, apparatuses, and systems directed to a wireless node location mechanism that uses a signal strength weighting metric to improve the accuracy of estimating the location of a wireless node based on signals detected among a plurality of radio transceivers. In certain implementations, the wireless node location mechanism further incorporates a differential signal strength metric to reduce the errors caused by variations in wireless node transmit power, errors in signal strength detection, and/or direction-dependent path loss. As opposed to using the absolute signal strength or power of an RF signal transmitted by a wireless node, implementations of the present invention compare the differences between signal strength values detected at various pairs of radio receivers to corresponding differences characterized in a model of the RF environment. One implementation of the invention searches for the locations in the model between each pair of radio receivers where their signal strength is different by an observed amount.

Abstract: A good understanding of the wireless channel, its key physical parameters and the modeling issues, lays the foundation for the rest of the book. This is the goal of this chapter. A defining characteristic of the mobile wireless channel is the variations of the channel strength over time and over frequency. The variations can be roughly divided into two types (Figure 2.1): Large-scale fading , due to path loss of signal as a function of distance and shadowing by large objects such as buildings and hills. This occurs as the mobile moves through a distance of the order of the cell size, and is typically frequency independent. Small-scale fading , due to the constructive and destructive interference of the multiple signal paths between the transmitter and receiver. This occurs at the spatial scale of the order of the carrier wavelength, and is frequency dependent. We will talk about both types of fading in this chapter, but with more emphasis on the latter. Large-scale fading is more relevant to issues such as cell-site planning. Small-scale multipath fading is more relevant to the design of reliable and efficient communication systems – the focus of this book. We start with the physical modeling of the wireless channel in terms of electromagnetic waves. We then derive an input/output linear time-varying model for the channel, and define some important physical parameters. Finally, we introduce a few statistical models of the channel variation over time and over frequency.

Abstract: A method and apparatus for determining the path loss model of an object within a wireless communication system is provided herein. During operation, a path loss model for a node is generated based on path loss values and corresponding numbers of neighbors of the said node. The path loss model is used to determine a relationship between path loss and distance. With this relationship established, distances to known-located nodes may be obtained by obtaining a path loss to the known-located node. From these distances, a node can then be located.

Abstract: Currently, for the planning of wireless networks (e.g. WLAN) in indoor scenarios either empirical (direct ray) or ray- optical (ray tracing) propagation models are used. In this paper both approaches are compared to one another and to measurements in different (multi-floor) buildings. Additionally a new concept - which is called Dominant Path Model - is presented in this paper. This new concept does not focus only on the direct ray (like empirical models) and it does not consider hundreds of rays for a single pixel (like ray tracing), but it focuses on the dominant path(s) between transmitter and receiver. The parameters of these dominant paths are determined (e.g. path length, number and type of interactions, material properties of objects along the path, etc.) and are used for the prediction of the path loss between transmitter and receiver. Thus the computational effort is far below ray tracing and in the range of empirical models. But the accuracy of the new model in very complex environments (where multiple interactions occur) is even higher than the accuracy of ray tracing models (because of their limitations in the number of interactions considered). This very high accuracy is shown with the comparison to measurements in different buildings.

Abstract: GSM system provides measurements regarding the signal attenuations from serving and neighboring base stations for managing radio resources. This paper proposes a mobile location estimation based on differences of downlink signal attenuations, which yield circles along which the mobile may lie. Then, the curves intersect at the estimated mobile position. The proposed method does not require a known and accurate path loss modeling, reduces the impact of shadowing on location, and is capable of being applied in existing systems without hardware development. Performance simulations include environments involving different standard deviation and cross-correlation of shadowings, and different abilities to detect base stations. Simulations demonstrate encouraging performance with only three base stations being available in severe shadowing environments. Additionally, the results of driving measurement show that the proposed method outperforms the cell-ID method in a real GSM in urban Taipei.

Abstract: This paper presents a statistical characterization of an ultra wideband (UWB) indoor propagation channel based on measurements conducted in various types of high-rise apartments in several cities of Korea. Measurements were carried out in the frequency band of 3–10 GHz. Various communication links were considered including both line-of-sight (LOS) and non-LOS (NLOS) scenarios, which covered within-the-room and room-to-room propagations. The measurement procedure allows us to characterize both the large-scale and the small-scale statistics of the channel. The aim here is to study in more detail the statistical characteristics of the UWB propagation channel and to provide insight for future statistical channel modeling work. Channel characteristics examined include the distance and frequency dependency of path loss, shadowing fading statistics, and multipath temporal-domain parameter statistics such as the mean excess delay, RMS delay spread, and the number of dominant paths. Copyright © 2005 John Wiley & Sons, Ltd.

Abstract: Multiple antenna systems can enhance wireless communication links by improving their capacity and/or reliability. Multiple input multiple output (MIMO) communications are the most common exploitation of this property. When applied to deterministic ray modelling, the computational cost of MIMO predication is a major drawback. Two MIMO modelling approaches are investigated. Both methods make use of an enhanced deterministic ray-tracing propagation model. The first method relies on point-to-point prediction for each of the multiple element-to-element links. The second approach estimates the MIMO link matrix from a single point-to-point ray tracing study. A comparison of normalized capacity and path loss is performed for the two methods in an outdoor city centre environment. For a single input multiple output (SIMO) case, the two modelling approaches are presented and compared with measured array data. Result show that the single point-to-point approximation works well and can significantly reduce run-time when compared with full element-to-element ray tracing.

Abstract: When a mobile station moves, the path loss and shadow fading contribute to the large-scale variation in the received signal strength. The variation of signal strength caused by shadow fadings is a random process, and handover decision mechanisms based on measurements of signal strength induce the "ping-pong effect." This paper proposes an improved handover algorithm, based on the estimates of location and velocity of the mobile station, to suppress the ping-pong effect in cellular systems. A practical approach based on GSM measurement data is used to estimate the location and velocity of mobile station to identify the correlation among shadowing components. The impact of location errors on handover performance was examined, and the proposed handover algorithm was applied to a real GSM system in urban Taipei city. The results indicate that the number of unnecessary handover can be reduced 18-26 percent by the proposed approach compared to the conventional method, while the signal outage probability remains similar. Besides, the computational complexity of the proposed algorithm is low, and the algorithm does not use a database or lookup table.

Abstract: Connectivity is an important property for QoS support in mobile ad hoc networks (MANETs). Recently, there has been a big effort in exploring the critical transmission range (CTR) analytically, based on different network models. While most of these studies rely on a geometric model and come up with asymptotic bounds, their significance regarding finite 802.11 based MANETs is unclear. In this paper, we investigate connectivity in MANETs from a layered perspective. We first point out how the transmission range affects the end-to-end connection probability in a log-normal shadowing model and compare the results to theoretical bounds and measurements in the path loss model. We then show how connectivity issues behave in 802.11 and IP based networks if the fading effect increases. The paper concludes with an analytical model for the link probability in log-normal shadowing environments as a function of the number of nodes, network area, transmission range, path loss exponent and shadowing deviation.

Abstract: In order to carry out high-speed packet communications using a large-volume transmission channel like an E-DCH, uplink communication quality must be good. However, in a state in which a link imbalance occurs, a mobile station cannot estimate the uplink communication quality from downlink communication quality. Therefore, the mobile station calculates a path loss from the setting power of a common pilot channel which is notified from a base station, and the received power of the common pilot channel received thereby, and also estimates the received power in the base station on the basis of this path loss. The mobile station further judges the uplink communication quality by estimating the SIR in the base station by using the interference power notified from the base station and the estimated received power.

Abstract: In this paper we analyze the optimal number and locations of fixed radio relay stations forming multi-hop links in infrastructure-based wireless networks. Under the assumptions of using orthogonal channels for the hops and all links having the same average path loss exponent, we show using the spectral efficiency as a metric that the optimal relay locations are at equal intervals along the straight line between source and destination whenever multihop is to be utilized. We show that a single-hop fixed radio link can be efficiently (from a spectral efficiency perspective) replaced with the multi-hop link only if the single-hop SNR has a relatively low value. We introduce a "multi-hop criterion" to quantify the single-hop SNR value below which a more efficient multi-hop replacement exists. We also determine the optimal number of hops for the multi-hop links having relays disposed in straight line at equal intervals

Abstract: A system abstracts channel information from field data gathered in actual wireless communication system environments. The abstracted data is then transformed into control signals or programming codes that can be used to control channel simulators so as to recreate the field conditions, including path loss, slow fading, fast fading, path delay, fading power spectral density with and without line-of-sight (LOS), and different kind of handoff scenarios, such as soft, softer, intra-band hard, inter-band hard handoffs. The system thus can accurately simulate a realistic wireless communication link originated from multiple signal sources in different band channels and formed by multipath signal propagation. The simulated realistic wireless communication link can be condensed by selecting the most useful scenarios from its original field data files or modified by tuning its parameters as desired.

Abstract: This paper presents the results of a significant number of propagation measurements performed at 3.5 GHz in urban environments. Furthermore, the data collected is used to derive a statistical path loss model over the range 100 m to 2 km. This work offers valuable propagation measurements in a frequency range that is globally being allocated for broadband wireless systems.

Abstract: We analyze the methodology and present the interpretation of results obtained in the measurement of the temporal Ricean K-factor and the time-autocovariance function of the received power for fixed narrowband wireless links in urban residential environments. Our main observation is that the time-autocovariance function (and thus both the temporal K-factor and the coherence time) fundamentally depends on a combination of the characterization of the transmit-receive path and whether the street-level moving objects are in the field of view of the antennas. In most practical cases the latter refers only to the customer premises antenna, as the base station is typically placed at a much greater distance from moving scatterers. No significant basis was found for the popular conjecture that the K-factor is mainly influenced by the excess path loss. However, a strong correlation between coherence times and temporal K-factor was observed over a wide range of link conditions. We also found that the time-autocovariance function can be quite accurately modeled by the weighted sum of two exponentially decaying functions: one with a time constant on the order of 1 s and the other typically slower by one order of magnitude. The results will be helpful in establishing design criteria for radio systems such as multiple input-multiple output that need to estimate the channel response and its persistence in time and for media access control (MAC) layer transmission protocols whose efficiency is affected by the depth and duration of channel outages.

Abstract: The design of RF circuits for short-range, low-power wireless communication is discussed. A derivation of optimum link range and transceiver power budget is presented based on simple models for indoor path loss and power vs. performance tradeoffs in a generic transceiver. Design techniques aimed at efficiently reaching these parameters are discussed for individual circuit blocks. Finally, some published transceivers are discussed with respect to the optimization and design techniques presented.

Abstract: The wireless radio channel poses a severe challenge as a medium for reliable high-speed communication. Not only is it susceptible to noise, interference, and other channel impediments, but these impediments change over time in unpredictable ways as a result of user movement and environment dynamics. In this chapter we characterize the variation in received signal power over distance due to path loss and shadowing. Path loss is caused by dissipation of the power radiated by the transmitter as well as by effects of the propagation channel. Path-loss models generally assume that path loss is the same at a given transmit–receive distance (assuming that the path-loss model does not include shadowing effects). Shadowing is caused by obstacles between the transmitter and receiver that attenuate signal power through absorption, reflection, scattering, and diffraction. When the attenuation is strong, the signal is blocked. Received power variation due to path loss occurs over long distances (100–1000 m), whereas variation due to shadowing occurs over distances that are proportional to the length of the obstructing object (10–100 m in outdoor environments and less in indoor environments). Since variations in received power due to path loss and shadowing occur over relatively large distances, these variations are sometimes referred to as large-scale propagation effects . Chapter 3 will deal with received power variations due to the constructive and destructive addition of multipath signal components.

Abstract: An ad-hoc network with a base station, a mobile and a third station acting as a relay is analysed. The channels are modelled using path loss, Rayleigh fading and thermal noise. Different combining methods and diversity protocols are compared. In the simulations, the amplify and forward protocol shows a better performance than the decode and forward protocol. To combine the incoming signals the channel quality should be estimated as well as possible. Information about the average quality shows performance benefits, and a rough approximation about the variation of the channel quality increases the performance even more. Whatever combination of diversity protocol and combining method is used, second level diversity is observed. The relative distances between the relay and the stations have a large effect on the performance.

Abstract: To facilitate a broad range of experimental research on novel protocols and application concepts, we consider an indoor wireless testbed to emulate the performance of real-world networks. A fundamental issue for emulation is the replication of communication links of specified quality. In particular, we need to replicate on the testbed, for every link in the real world, a communication link whose received signal-to-interference-and-noise-ratio (SINR) matches the corresponding link signal-to-noise-ratio (SNR). In this paper, we focus on the downlink SNR mapping associated with a network with a single access point (AP). Four indoor wireless propagation models (commercial buildings with/without line-of-sight path and residential buildings with/without line-of-sight path) and two types of spatial distributions (uniform distribution inside a circular cell and uniform distribution along a line) have been investigated. Based on the characteristics of the indoor testbed, we propose a mapping method with one AP and one interferer, which separates the task into two phases: in the first phase, the best location and transmission power for the interferer node are determined; in the second phase, the topology of receiver nodes is configured by a minimum weight matching algorithm. Through analysis and simulations, we find that when the interferer node is located on the corner across from the AP, we can achieve a mapping range on the order of 57 dB and an average root-mean-square (RMS) mapping error less than 1 dB.

Abstract: The paper presents a statistical characterization of an ultra-wideband (UWB) indoor propagation channel based on measurements conducted in various types of high-rise apartments in several cities in Korea. Measurements were carried out in the frequency band of 3-10 GHz. Various communication links were considered including both line-of-sight (LOS) and non-LOS (NLOS) scenarios which cover within-the-room and room-to-room propagation. The measurement procedure allows us to characterize both the small-scale and the large-scale statistics of the channel. The aim is to study in more detail the behavior of the UWB propagation channel and to provide more of the measurement data required for the standardization activities in the IEEE 802.15.4a channel modeling subgroup. Channel characteristics examined include the distance and frequency dependency of path loss, shadowing fading statistics and multipath temporal-domain parameter statistics, such as the mean excess delay, RMS delay spread and the number of dominant paths.

Abstract: An important problem for wireless ad hoc networks has been to design overlay networks that allow time- and energy-efficient routing. Many local-control strategies for maintaining such overlay networks have already been suggested, but most of them are based on an oversimplified wireless communication model.In this paper, we suggest a model that is much more general than previous models. It allows the path loss of transmissions to significantly deviate from the idealistic unit disk model and does not even require the path loss to form a metric. Also, our model is apparently the first proposed for algorithm design that does not only model transmission and interference issues but also aims at providing a realistic model for physical carrier sensing. Physical carrier sensing is needed so that our protocols do not require any prior information (not even an estimate on the number of nodes) about the wireless network to run efficiently.Based on this model, we propose a local-control protocol for establishing a constant density spanner among a set of mobile stations (or nodes) that are distributed in an arbitrary way in a 2-dimensional Euclidean space. More precisely, we establish a backbone structure by efficiently electing cluster leaders and gateway nodes so that there is only a constant number of cluster leaders and gateway nodes within the transmission range of any node and the backbone structure satisfies the properties of a topological spanner.Our protocol has the advantage that it is locally self-stabilizing, i.e., it can recover from any initial configuration, even if adversarial nodes participate in it, as long as the honest nodes sufficiently far away from adversarial nodes can in principle form a single connected component. Furthermore, we only need constant size messages and a constant amount of storage at the nodes, irrespective of the distribution of the nodes. Hence, our protocols would even work in extreme situations such as very simple wireless devices (like sensors) in a hostile environment.

Abstract: The indoor optical wireless channel is significantly different than the radio channel. Statistical propagation models developed for the radio channel, which characterize path loss, shadowing, and multipath fading, do not apply. In this paper, we investigate statistical modelling for the indoor optical wireless channel through the examination of the characteristics of a large set of channel impulse responses. The channel responses are generated using an estimation method based on geometrical modelling of indoor environments together with an iterative technique for calculating multiple reflections. We confirm prior studies showing that channels with line-of-sight paths must be modelled separately from those fully diffuse channels with no such path. We show that the distribution of the channel gain in dB for the LOS component follows a modified gamma distribution, and the channel gain in dB for LOS channels including all reflections follows a modified Rayleigh distribution for most transmitter–receiver distances. Similar results are described for distributions of channel gains of diffuse channels and for distributions of rms delay spreads. Finally, we describe a method for generating a statistically realistic impulse response given any transmitter–receiver separation in an indoor environment. Copyright © 2005 John Wiley & Sons, Ltd.

Abstract: This paper presents the results of ultra-wide band (UWB) indoor channel measurements performed in a hall, a meeting room, and a corridor with both LOS and NLOS scenarios The channel multipath propagation characteristics are investigated by examining the power delay profiles, path loss, power distribution, and rms delay spread It is found that in UWB channels, the appearance of multipath components are in the forms of diffuse, single dominant and clustered paths, their appearance is highly dependent on the measurement environments UWB radio is robust to multipath fading due to the small fading margin and the high multipath diversity gain it has Moreover, the UWB measurement results are compared with the results obtained in traditional wideband 60 GHz indoor channels

Abstract: Impulse response radiowave propagation measurements from an urban area of Denver, CO, are described. The basic transmission loss and delay spread are used to characterize the mobile communications environment. These metrics are quantified using path loss slope and delay spread statistics. By analyzing the results versus carrier frequency, the relative propagation impairments at 430, 1350, 2260, and 5750 MHz are compared. It was found that the path loss slope increased on average by 11 dB/dec and the median delay spread decreased from 0.7 to 0.3 /spl mu/s over the decade of frequencies measured.

Abstract: This paper describes the results of an ultra wideband (UWB) channel measurements and modelling from 31 to 60 GHz carried out at the Oulu University Hospital Mainly line-of-sight (LOS) channels were measured having transmitter-receiver separation from 3 to 6 m The modelling is done in time domain and in frequency domain, and the results are compared with Channel parameters that are corresponding to the modified Saleh-Valenzuela (SV) model in time domain and autoregressive (AR) model in frequency domain are extracted from the measurement data Also, delay spreads and path losses are examined In the study, the effect of the huge frequency diversity over the UWB band on the path loss is pointed out

Abstract: Received signal power in mobile wireless commu- nications is often modelled as a product of three factors: distance-dependent average path loss, lognormal variation in the local mean power level (shadow fading), and small-scale fading due to movement in the order of a wavelength. Of these three factors, the least well understood is the shadow fading, the lognormality of which is usually explained as a result of multiplication of large number of random attenuating factors in the radio channel. This model is not credible from physical propagation point of view, and is also partly contradicted by measurements. In this paper, we propose an additive cluster- based model for shadow fading. We assume that the received signal is a superposition from several scattering clusters. It is shown that if the distribution of the local mean cluster powers satisfy certain mild statistical conditions, the shadow fading of the received signal will be approximately lognormal. We also present measurement results that support the theory.

Abstract: This work presents the results of the studies concerning the applications of the feedforward neural networks to the prediction of propagation path loss in urban and suburban environment. First, neural network models are designed in order to predict the path loss. Further investigations are made on an error correction model, based on the combination between a theoretical model and a neural network. The performances of the neural models are compared to the measured path loss values from the measurements conducted in the city of Kavala and in Oia village on Santorini Island, Greece, based on the absolute mean square error, standard deviation and root mean square error between predicted and measured values. Also, the neural networks models are compared to each other and to the COST 231-Walfisch-Ikegami.