This work presents accurate closed-form approximations for the probability density function (PDF) of the sum of independent and identically distributed (i.i.d.) fading envelopes and square fading envelopes, experienced by indoor and outdoor channels operating in the D-band. In order to provide a simple yet accurate analytical expression for these PDFs, we propose the use of the Pearson family of distributions, which are mainly characterized by their skewness and kurtosis. Our analysis has demonstrated that among the seven types of Pearson distributions, the type I Pearson distribution provides the most accurate fit to the exact PDF of envelopes and squared envelopes, for a diverse range of indoor and outdoor wireless propagation scenarios. The distribution parameters are estimated using moments-matching techniques, while the requisite moments are obtained through a measurement campaign conducted in indoor as well as outdoor environments. Specifically, with regard to the indoor scenarios, the following locations have been considered: A mall, an airport, and an entrance hall. With regard to the outdoor scenarios, the following locations have been selected: A university campus, a residential area, and a city center. Our results are further applied to analyze the average bit error rate performance and the ergodic capacity of equal-gain combining (EGC) and maximal-ratio combining (MRC) receivers, the sum rate of rate splitting multiple access (RSMA) systems with EGC diversity reception, as well as the coverage probability of wireless systems employing intelligent reflecting surfaces (IRS). Our analysis is supported by extensive numerical results and Monte Carlo simulations.

Millimeter-wave (mmWave) and D Band (110170 GHz) frequencies are poised to play a pivotal role in the advancement of sixth-generation (6 G) systems and beyond, owing to their ability to enhance performance metrics such as capacity, ultra-low latency, and spectral efficiency. This paper concentrates on deriving statistical insights into power, delay, and the number of paths based on measurements conducted across four distinct locations at a center frequency of 143.1 GHz. The findings underscore the suitability of various distributions in characterizing power behavior in line-of-sight (LOS) scenarios, including lognormal, Nakagami, gamma, and beta distributions, whereas the loglogistic distribution gives the optimal fit for power distribution in non-line-of-sight (NLOS) scenarios. Moreover, the exponential distribution shows to be the most appropriate model for the delay distribution in both LOS and NLOS scenarios. In terms of the number of paths, observations indicate a tendency for the highest concentration within the 10 m to 30 m distance range between the transmitter (Tx) and receiver (Rx). These insights shed light on the statistical nature of D band propagation characteristics, which are vital for informing the design and optimization of future 6 G communication systems.

As the ubiquity of 5G technology permeates various domains, coupled with the introduction of new carrier frequencies under the New Radio (NR) framework, devices employing this advanced technology require stringent and repeatable operational conformance tests. Those tests are essential to ascertain the AUT performance under realistic deployment scenarios, thereby ensuring reliability. Hence emulating realistic channel characteristics is fundamental to reach a reliable evaluation of radio components. Considering small-scale fading phenomena is imperative in evaluating the operational integrity of radio devices, as it pervades everything from vehicular communications to the mobility of user equipment. This work demonstrates implementing and validating the operation of a Rician fading channel emulator which can be integrated in an over-the-air antenna testbed. It provides a real-time cost-effective solution using off-the-shelf software defined radios (SDR). The paper provides an overview on the hardware setup and the software implementation of the Rician fading emulator. The setup is tested in an anechoic chamber and comparative analysis showed a robust correlation between the empirical data and theoretical plots of the Rician fading magnitude statistics.

In this work we present a novel ray-launching (RL) method for field prediction utilizing a laser-scanned point cloud model of the environment. The method takes advantage of the high level of detail found in the point cloud to simulate propagation of rays as they undergo reflection and transmission through local surfaces represented by points of the point cloud. The method is implemented using MATLAB's Parallel Computing Toolbox and its GPU Computing library for straightforward parallelization and acceleration of computations. Indoor multipath channels are simulated at the 60 GHz band and compared to their measured counterparts to study accuracy of the presented method. Up to 6 reflections and 3 transmissions can be simulated in approximately 6 minutes. Utilizing a post-processing step to eliminate propagation paths with near-identical trajectories, an issue seemingly unique to point clouds, the channel is well reproduced in terms of path gains and a relative error of less than 10% for delay spread.

This contribution aims at experimentally validating the suitability of Gaussian mixture (GM) distributions to capture the stochastic characteristics of outdoor terahertz (THz) wireless channels. In this direction, we employ a machine learning enabled approach, based on the expectation maximization algorithm, in order to identify the suitable number of Gaussian distributions as well as their corresponding parameters that result to an acceptable fit. The fitting accuracy of the GMs to the empirical distributions is evaluated by means of the Kolmogorov-Smirnov (KS), Kullback-Leibler (KL), root-mean-square-error (RMSE) and R2fitting accuracy tests. These tests verify the suitability of GMs to model the small-scale fading channel amplitude of outdoor THz wireless links. In addition, the fitting accuracy results indicate that as the number of mixtures increases the resulting GMs achieve a better fit to the empirical data.

| openaire: EC/H2020/101015956/EU//Hexa-X

This work investigates the suitability of α–µ distribution to model line-of-sight (LoS) and non-line-of-sight (NLoS) multi-path fading in terahertz (THz) wireless systems. The goodness of fit of α–µ to the small-scale fading of the measured channels is evaluated in terms of the Kolmogorov-Smirnov (KS) test. The KS test revealed the capability of α–µ distribution to capture the fading characteristics of THz wireless channels. To highlight the importance of this study and the applicability to the theoretical analysis of THz wireless systems, for indicative values of α and µ, the ergodic capacity of THz wireless systems is assessed.

6G will likely be the first generation of mobile communication that will feature tight integration of localization and sensing with communication functionalities. Among several worldwide initiatives, the Hexa-X flagship project stands out as it brings together 25 key players from adjacent industries and academia, and has among its explicit goals to research fundamentally new radio access technologies and high-resolution localization and sensing. Such features will not only enable novel use cases requiring extreme localization performance, but also provide a means to support and improve communication functionalities. This paper provides an overview of the Hexa-X vision alongside the envisioned use cases. To close the required performance gap of these use cases with respect to 5G, several technical enablers will be discussed, together with the associated research challenges for the coming years.

The use of above-100 GHz radio frequencies would be one of promising approaches to enhance the fifth-generation cellular further. Any air interface and cellular network designs require channel models, for which measured evidence of large-scale parameters such as pathloss, delay and angular spreads, is crucial. This paper provides the evidence from quasi-static spatio-temporal channel sounding campaigns at two indoor hotspot (InH) scenarios at 140 GHz band, assuming short-range backhaul connectivity. The measured two InH sites are shopping mall and airport check-in hall. Our estimated omni-directional large-scale parameters from the measurements are found in good match with those of the Third Generation Partnership Project (3GPP) for new radios (NR) channel model in InH scenario, despite the difference of assumed link types and radio frequency range. The 3GPP NR channel model is meant for access links and said to be valid up to 100 GHz, while our measurements cover short-range backhaul scenarios at 140 GHz. We found more deviation between our estimated large-scale parameters and those of the 3GPP NR channel model in the airport than in the shopping mall.

This paper establishes the analytical model and analyzes the statistical behaviors of multimode channels in spherical vector wave (SVW) domain based on the microcellular radio channel measurement in downtown Helsinki at 5.3 GHz band. The multimode channel is the representation of radio wave propagation in the form of the SVW mode coupling between the transmit and receive antennas. The multimode channel does not rely on particular realizations of antennas at link ends, since any transmitting/receiving/scattering fields associated with an antenna can be modeled as a weighted sum of SVW modes where different antennas have different mode weights. The multimode channels are converted from the plane wave channel model parameters that are extracted from measured channels of coherent snapshots along 6 different routes in Helsinki. Based on the analysis of various first and second order statistics of the multimode channels, the main findings can be summarized as follows: 1) the multimode channels are power imbalanced; 2) the envelope short-term fading statistics of the multimode channels can be described with Rician probability distributions with varying K-factors; 3) the auto-correlations of multimode channels along the spatial translation of a mobile node in a propagation environment present varying coherent distances; 4) the cross-correlations of multimode channels vary with the spatial translation too. The obtained results and the proposed multimode channel model provide invaluable insights into the design of antenna systems tailored to a specific propagation environment. Indeed, antenna systems at both link ends can be devised such that the multimode channels with higher power, larger coherent distance and smaller cross-correlation are excited resulting in multiple-input multiple-output antenna systems that exploit efficiently the degrees of freedom of the propagation channel.

Future wireless networks are expected to operate in both the centimeter-wave and millimeter-wave bands. It is thus necessary to provide an accurate characterization of the {\em joint} channel properties in the two bands. Shadow fading is an important characteristic of wireless channels as it impacts achievable data rates and in particular outage probabilities. In this paper, we propose cross-band correlation models that can be used to capture the correlation over space and frequency. The models are designed to reduce to existing correlation models in the case of a single-band, which enables reuse of the large existing literature for (single-band) shadowing models. We extract and report the parameters of the proposed models in a micro-cellular environment. The important finding from our proposed models is that the cross-band spatial correlation function may not be derived just by scaling a single-band correlation function.

Device-to-Device (D2D) communications has been embraced as a novel approach for extending coverage in fifth-generation (5G and beyond) wireless networks. Throughput and reliability assessment of such wireless networks are therefore of utmost importance for D2D communication systems design. In this paper, we consider the capacity results of wireless propagation channels in two 5G modes namely the sub-6 GHz centimeter-wave (cm-wave) and 60 GHz millimeter-wave (mm-wave) bands for a multiple-input-multiple-output (MIMO) D2D fading channel. Results presented in this paper were obtained from propagation channel measurements jointly conducted in both cm-wave (2-6 GHz) and mm-wave (59-63 GHz) bands using an 8 × 8 MIMO virtual array setup in an outdoor environment. These measurements were conducted at the exact same locations (with constituents unchanged) in both cm-wave and mm-wave bands for comparability of results. Capacity values were computed using two power policies (with and without channel state information (CSI)). We also investigated the eigenmode spectral structure to understand the spatial correlatedness of the channel and the Rician K-factor to analyze small-scale fading in the channel. The results presented in this paper can be used by wireless systems designer for assessing the performance of D2D systems operating in the cm-wave and/or mm-wave bands for this type of environment.

In this paper, we parameterize an excess loss-based multipath component (MPC) cross-polarization ratio (XPR) model in indoor and outdoor environments for above-5-GHz frequency bands. The results are based on 35 measurement campaigns in several frequency bands ranging from 5 to 80 GHz. A conventional XPR model of an MPC assuming a constant mean value fits our measurements very poorly and moreover overestimates the depolarization effect. Our measurements revealed a clear trend that the MPC XPR is inversely proportional to the excess loss in reference to the free-space path loss. The model is physically sound as a higher loss is attributed to more lossy interactions or to a greater number of interactions with objects, leading to a greater chance of depolarization. The measurements furthermore showed that the MPC XPR is not strongly frequency or environment dependent. In our MPC XPR model, an MPC with zero-dB excess loss has a mean XPR of 27 dB. The mean XPR decreases half-a-dB as the excess loss increases by every dB and the standard deviation around the mean is 7 dB. The model is applicable to existing channel models to reproduce realistic MPC XPRs for the above 5-GHz radio links.

In this paper, we present a method to analyse the millimeter-wave (mm-wave) radio channel scatterers applied to channel sounding at 32 GHz in an urban microcell (UMi) environment in the city of Espoo (Finland). The proposed method is based on a geometric single bounce assumption for recovering the scatterer positions. A simple formulation exploiting the discovered scatterer positions allows quantifying the excess-loss to free space for each scatterer. We found that large building walls, as well as small urban furniture such as metallic sign-board reflectors, are objects producing reflections and strong scattering. Finally, their radar cross-section and equivalent scattering area are estimated.

This paper reports measurements of self-interference (SI) channels in an in-band full-duplex (IBFD) relay scenario for millimeter-wave street-level backhauling. The street-level backhauling suffers from clutters surrounding the relay devices and hence SI originating from the environment may be dominant. An ultrawideband channel sounder operating at 70 GHz carrier frequency is used to measure the SI channels in a chamber, indoor window-side, indoor and outdoor corner scenarios. The transmit and receive antennas are waveguide-fed lens antennas. The measurements showed that cross-polarized feeding of waveguides to the lenses provided higher isolation than co-polarized feeding. In the corner scenario, observed minimum isolation level is 85 dB in the frequency domain, and 100 dB in the delay domain. The results confirmed that isolation is not limited by the direct coupling because of the high directivity of the lens antenna, but by the environmental coupling. Further link budget analysis for outdoor-to-indoor backhauling showed that the IBFD relay with practical transmit power is capable of enhancing the signal-to-noise ratio and hence extending the coverage, as SI at the relay receiver can be almost the same level as thermal noise.

This paper studies suitability of two polarimetric diffuse scattering models of electromagnetic fields at 28 GHz from a facade of a modern shopping center. The models are integrated into our in-house ray-based wave propagation simulation tool. Parameter values of the scattering models are estimated in reference to polarimetric channel sounding at the same site. We found that Lambertian model represents the measured scattering better than SLD model as the facade elements are made of heterogeneous materials and non-uniformly oriented, leading to backscattering equally strong as forward scattering. The parameter values giving the best fit of the scattering models to measurements are in line with the previously reported values in the literature for below-6GHz RF.

Wireless capsule endoscopy (WCE) systems are used to capture images of the human digestive tract for medical applications. The antenna is one of the most important components in a WCE system. In this paper, we propose a compact capsule antenna operating at the 433-MHz ISM band. The antenna conforms to the outer-wall of a small capsule module with dimensions of 19.5 mm ×10 mm. A colon-equivalent tissue phantom and CST Gustav voxel human body model were used to numerically verify the operation of the capsule antenna. The simulation results in the colon-tissue phantom were then validated through in-vitro measurements using a liquid phantom. According to the phantom simulations, the capsule antenna has -10 dB impedance matching from 288 to 2200 MHz. The ultrawideband characteristic enables the capsule antenna to tolerate the detuning effects due to electronic modules in the capsule and due to the proximity of various different tissues in gastrointestinal tracts. While providing ultrawide operational bandwidth and sufficient radiation performance, the small size makes the antenna suitable especially for pediatric patients in addition to adults.

This paper studies a gain of an antenna array embedded on a mobile device operating at a millimeter-wave radio frequency. Assuming that mobile phones at millimeter-wave range operate with a single baseband unit and analog beamforming like phased arrays, we define a total array gain denoting a path gain of the phased antenna array in excess to the omni-directional path gain. The total array gain circumvents the ambiguity of conventional array gain which cannot be uniquely defined as there are multiple choices of a reference single-element antenna in an array. Two types of 8-element patch antenna arrays implemented on a mobile phone chassis, i.e., uniform linear array (ULA) and distributed array (DA) both operating at 60 GHz, are studied. The gain evaluated in a small-cell scenario in an airport shows that DA achieves higher median and outage gain by up to 8 and 6 dB than ULA when different orientations of the mobile phone are considered along with body torso and finger shadowing. There are always postures of the mobile phone where ULA cannot see the line-of-sight due to directionality of the patch antenna and of body and finger shadowing, leading to outage gain of -15 dB in the worst case. The DA has much smaller variation of the gain across different orientations of the phone, even when the human torso shadowing and user's finger effects are considered.

The millimeter-wave (mm-wave) band will be a key component of fifth-generation (5G) wireless communication systems. This paper presents radio propagation measurements and analysis investigating the wideband directional channel characteristics of the mm-wave transmission for in-building and urban cellular communication systems in the 28-GHz band. Based on the measurements, we analyze and model the spatio-temporal channel characteristics such as multipath delay, angular statistics, and path loss. In particular we investigate the clustering of the multipath components, and investigate both the intra-cluster and inter-cluster distributions. Based on these investigations, we present a complete channel model suitable for system simulations in the in-building and urban environments.

A compact dual band antenna operating simultaneously at 5.4 GHz and 15 GHz is presented in this paper. It is a planar array composed of a grid of 6×8 (48) patch antennas working at 5.4 GHz and 7×9 (63) patch antennas working at 15 GHz. The whole antenna array occupies an area of 150 mm × 180 mm which fits the ordinary size requirement of wireless access point. All the antenna patch antennas have a reflection coefficient lower than −6 dB across 320 and 2000 MHz bandwidth at 5 and 15 GHz. The electromagnetic coupling between any two antennas is lower than − 10 dB within the specified bandwidth. Measurement results show good agreement with the simulation of input matching, mutual coupling and radiation pattern. Compared to the ordinary antenna array design with half-wavelength spacing between two neighboring antennas, our proposed dual band array design accommodates 1.6 times more antennas at 5.4 GHz and extra 63 antennas at 15 GHz, while maintaining sufficient radiation efficiency, matching bandwidth and decoupling.

Spatio-temporal channel sounding was performed at frequency bands of 15,28 and 60 GHz in the backhaul-link street canyon scenario. Analysis of the measured channels from the sounding show 1) path loss exponents close to the free-space in the line-of-sight condition, with extra losses of 5 to 30 dB in the non-line-of-sight conditions; 2) the azimuth angular and delay spreads mostly less than 25° and 30 ns at the three frequency bands; 3) decreasing angular and delay spreads as the link distance is longer, 4) up to fourth-order specular reflection observed in the 100-m long street canyon when looking at the strongest 30-dB dynamic range of the channels, and finally, 5) no decisive frequency dependency of the angular and delay spreads and the reflection order, though the presence or absence of cars in the street canyon during the measurements seemed to make some impacts on the spread values given the antenna height of our channel sounding.

For the development of new 5G systems to operate in bands up to 100 GHz, there is a need for accurate radio propagation models at these bands that currently are not addressed by existing channel models developed for bands below 6 GHz. This document presents a preliminary overview of 5G channel models for bands up to 100 GHz. These have been derived based on extensive measurement and ray tracing results across a multitude of frequencies from 6 GHz to 100 GHz, and this document describes an initial 3D channel model which includes: 1) typical deployment scenarios for urban microcells (UMi) and urban macrocells (UMa), and 2) a baseline model for incorporating path loss, shadow fading, line of sight probability, penetration and blockage models for the typical scenarios. Various processing methodologies such as clustering and antenna decoupling algorithms are also presented.

Airport terminal is one of the indoor scenarios envisioned for mm-wave 5G deployment. In this paper, we characterize the propagation channel in the Helsinki airport at 15, 28, and 60 GHz bands by means of directional wideband channel sounding. The radio environment was characterized by studying the specular propagation paths, specular and diffuse power contributions, polarization, and the delay and angular spreads. All the studied metrics in different bands were compared and the frequency dependency was analyzed.

In-band full-duplex (IBFD) operation can potentially double the spectral efficiency of wireless networks. For IBFD operation, self-interference is a critical issue. In addition, in full-duplex cellular (FDC) networks, particularly when the cell size is small, inter-user interference would be another limiting factor for the performance. To overcome these issues, the scheduling scheme proposed in this paper is to adaptively utilize bidirectional IBFD in addition to half-duplex (HD) and unidirectional IBFD in FDC networks according to the residual self-interference after interference cancellation and inter-user interference. The proposed scheme is based on generalized proportional fair scheduling by using a fairness parameter. Extensive simulations are conducted to analyze the impact of the cell size. Simulation results revealed that the use of bidirectional IBFD is extremely effective for a small cell with few users if self-interference is sufficiently canceled because inter-user interference is large in small cell and the scheduler tends to select bidirectional IBFD in the cell with few users.

Millimeter-wave radios have great potential of spatial interference management through its physically small but possibly electrically large antenna aperture. It is expected that the interference management becomes a major challenge after massive deployment of millimeter-wave devices. This paper therefore discusses design guidelines and an influential radio link property of two beamforming schemes for spatial coexistence at 60 GHz; conventional gain focusing and the interference alignment. The guideline is derived from an example of distributed channels in a small room. The investigation shows that, under a moderate receive signal-to-noise ratio, 1) having 2λ2antenna apertures at the Tx and Rx realizes 3 to 7 bit/s/Hz under the presence of mutual interference, 2) the gain focusing is as robust as the interference alignment, and finally, 3) inter-link correlation is a primary bottleneck in the interference alignment.

To statistically model time-variant vehicle-to-vehicle (V2V) channels, the dynamic multi-path components (MPCs) are characterized based on suburban measurements conducted at 5.3 GHz. The correlation matrix distance (CMD) is used to determine the size of local wide-sense stationary (WSS) region. Within each WSS time window, MPCs are extracted using wideband spatial spectrum of Bartlett beamformer. A MPC distance (MCD)-based tracking algorithm is used to identify the "birth" and "death" of MPCs over different WSS regions, and the lifetime of MPC is modeled with a truncated Gaussian distribution. Distributions of number of MPCs and their positions are statistically modeled. The MPC characterization considers both angular and delay domain properties as well as the dynamic evolution of MPCs over different WSS regions. The results shows insight into the dynamic behaviors of MPCs in V2V environments, and is useful for the scatterer modeling in the geometry-based stochastic channel modeling.

In this paper, we derive parameters of the WINNER II channel model for a shopping mall environment at 60 GHz band, covering both line-of-sight and obstructed-line-of-sight scenarios. The model parameters are derived mostly based on channel measurements reported in this paper. Due to a large measurement bandwidth and the highly specular nature of the channel in the shopping mall, only weak clustering effects of propagation paths are found. Still, we demonstrate that the WINNER II model structure is applicable to 60 GHz channel modeling since the model reproduces the measured channels well.

This paper investigates the achievable throughput of a multi-antenna two-hop relay link under hybrid full/half-duplex operation. The analysis is facilitated by realistic waveform simulations, which explicitly model all the essential circuit impairments occurring in the relay transceiver together with degrading channel estimation and self-interference cancellation. The obtained results indicate that pure full-duplex operation does not ensure optimal performance but additional half-duplex transmission periods are usually needed to maximize the end-to-end throughput. Especially, it is shown that the estimation of the self-interference channel within the relay should be performed when the source is not transmitting anything while also the source should be allowed to transmit alone to avoid making the first hop a bottleneck. These findings form a solid basis for optimizing the full-duplex MIMO relay deployments in future mobile networks.

Mutual orthogonal user channels in multiuser (MU)-multiple-input multiple-output (MIMO) systems are desirable and can be approximately obtained under independent and identically distributed (i.i.d.) Rayleigh fading assumption with a very large number of base station antennas. However, it has been shown that at millimeter-wave (mmW) frequencies, this assumption is not valid due to the limited number of multipath components and spatial channel correlation. In this paper, we examine the mutual orthogonality of a realistic 60-GHz outdoor propagation channel with practical large antenna arrays, and determine the factors deciding it based on the channel data generated by means of deterministic field prediction. The results obtained reveal relationships between mutual orthogonality, inter-user distance, number of active users, transmit array dimensions, and downlink system capacity at 60-GHz band, which are useful for designing future mmW massive MU-MIMO systems.

Relays can be used to improve the coverage in blind spots as well as increase the signal strength at locations where the signal from the access point undergoes fading. In-band full-duplex relaying is a promising technique which improves the spectral efficiency over traditional half-duplex relaying by relaying at the same time slot and frequency. Relays are expected to play a major role in IEEE 802.11ah systems for below 1 GHz WLAN in order to cover a large area of 1 km around the access point. In this contribution, the impact of deploying in-band full- duplex relays is studied over traditional half- duplex relays in improving the coverage and throughput at the stations for M2M applications. System-level realistic evaluation of in-band full- duplex relaying is performed using the COST-2100 channel model to model the propagation and self- interference channels at 920 MHz. The channel is combined with realistic antenna design to determine the end-to-end throughput at the location of each station in a 1 sq.km area. For the downlink scenario, it is shown that such in-band full-duplex relays can increase the number of users for a given throughput over half-duplex relays. Also, a single in-band full-duplex relay can decrease the outage by 0.9% compared to half-duplex relays and 12.6% without a relay to cover 97.8% of the stations in a 1 sq.km area with downlink throughput of 100 kbps.

This paper studies the potential of spatial multiplexing for measured 60 GHz radio channels by estimating the number of eigenchannels. It is well-known that the number of available eigenchannels is dependent on a propagation channel condition as well as antenna array conguration. We evaluate a spatial degrees- of-freedom (SDoF) metric that depends on the propagation conditions and the antenna aperture size, but is otherwise independent of the realization of antenna elements on the aperture. The SDoF metric is a measure of the effective number of antenna elements for spatial multiplexing. We evaluate the SDoF for 60 GHz multiple-input multiple-output channels measured in a conference room environment under a line-of- sight (LOS) condition. Our analysis reveals that the SDoF is more than one for a transmit- receive antenna separation of more than 2 m, which indicates that spatial multiplexing can work in such LOS scenarios. Our results indicate that using only 10 antenna elements at each of the transmit and receive antenna aperture is sufficient for effective spatial multiplexing performance in the considered propagation scenario. Furthermore, by using just 5 antennas at each aperture, eigenchannels down to -15 dB relative magnitude can still be captured.

This paper presents a measurement-based evaluation of link budget gain from uplink transmit antenna selection in 3GPP LTE. In contrast to earlier studies, the results are based on channel measurements and realistic non-omnidirectional mobile terminal antennas. Further, in addition to the impact of fast selection based on small-scale fading power, also the gain from slow selection based on average signal power is evaluated. In the evaluated measurement cases, fast and slow fading based transmit antenna selection result in up to $3.7$ and $3.2$ dB average power gain, respectively, with respect to the fixed uplink transmit antenna case. This implies that with practical non-omnidirectional terminal antennas a major portion of the gain can be realized based on slow selection, hence justifying a simple open-loop transmit antenna selection scheme which is also applicable to FDD systems.

This paper presents a performance evaluation of 60 GHz high-speed radio systems under an application scenario related to a medical operation. The evaluation is based on the following specifications: IEEE 802.15.3c and IEEE 802.11ad, which have been designed to provide data rates of multi-Gbps at physical layer. First, by using measured power delay profiles (PDPs) in hospital environments, both inter-symbol-interference (ISI) and channel capacity are calculated. Then, system simulations are carried out in order to show achievable throughputs. The results reveal that OFDM systems provide the required throughput for the application scenario in all the measured PDPs. On the other hand, the single carrier (SC) systems without any equalization are limited to 85 % of the measured PDPs where the required throughput is achieved. Also, it is shown that the calculated channel capacity for each measured PDP reveals the similar trend with the available throughputs obtained from the system simulations.

Directional properties of the radio channel are of high importance for the development of reliable wireless systems operating in the 60 GHz frequency band. Using transfer functions measured from 61 to 65 GHz in a conference room we have extracted estimates of the multi-path component parameters using the SAGE algorithm. In the paper we compare results for line-of-sight (LOS) scenarios and the corresponding non-line-of-sight (NLOS) scenarios and present values of the direction spread at the Tx and the Rx.

A millimeter-wave (mm-wave) impulse radio is an attractive alternative to existing high-speed mm- wave radio systems because of the potential for a simpler transceiver architecture. This paper studies the feasibility of a mm-wave impulse radio system for home and office use by considering state-of-the- art transceivers and multiple-input multiple-output measured propagation channels as well as the IEEE 802.15.3c channel model. Our analysis reveals that reliable data transmission is infeasible even in line-of-sight (LOS) scenarios because of a low power level at the Rx if we do not use beamforming. However, introducing 7×7 beamforming at the Tx dramatically improves the coverage beyond 5 m distance in the LOS scenario and up to 5 m in a non- line-of-sight (NLOS) scenario, though the performance varies in the NLOS scenario, depending on the Tx and Rx locations. We propose an adaptive transmit signaling scheme that adjusts the pulse repetition frequency depending on the delay dispersion of the propagation channel in order to avoid intersymbol interference and keep the Rx structure simple. The proposed transmit signaling scheme leads to a pulse transmission rate of 250 Mpulses/s in all measured channels while the rate is lower when the 802.15.3c model is considered because of a more multipath-rich characteristics than our measured channels.

This letter presents radio channel measurements and modeling results for the feasibility study of 60 GHz high-speed radio systems in hospital environments. Two possible applications of those systems are considered: real-time video streaming for angiography and for ultrasonic inspection. Channel modeling was performed for the path loss and multipath characteristics of the propagation channel, i.e., the delay spreads. Results revealed generally lower path loss and delay spread values compared to regular indoor office and residential environments. The results indicate that the 60 GHz radio systems operating in hospital environments can provide better signal quality and wider coverage than those operated in regular indoor environments, though increased interference with neighboring cells might be an unfortunate consequence.

Beamforming is an important feature of 60 GHz communications. We present an analysis of the influence of beamforming in indoor ultrawideband radio channels measured in the mm-wave 60 GHz band. The performance of narrowband and wideband direction-based beamformers is investigated in terms of improving channel metrics such as the delay spread, excess delay, and the signal-to-noise ratio (SNR). The performance of the direction-based beamformers is compared with dominant eigenmode transmission and statistical beamforming. Our analysis reveals that in line-of-sight (LOS) scenarios, the two direction-based beamformers have a similar performance that approaches the upper bound set by dominant eigenmode transmission. In non-LOS (NLOS) scenarios, the direction-based beamformers show a performance degradation in relation to the upper bound, with the narrowband beamformer worse off than the wideband variant. The array gain in our measured NLOS scenarios is observed to exceed the theoretical upper limit valid for a rich scattering environment. We show that this result follows from the spatial structure of the measured NLOS channels that has only a few strong reflected components. We investigate the influence of array size on beamforming performance; 5×5 planar arrays are observed to improve the channel's delay metrics as well as the larger 7×7 planar arrays.

There has been extensive research about single link multiple-input multiple-output (MIMO) channels, both simulated and measured, but only few studies have targeted multilink analysis with measured channel data. Hence, in this paper, we analyze the influence of spatial separation of user terminals and the human shadowing effect on the MIMO capacity and to the signal to interference ratio (SIR) in a time-variant dual-link scenario. The paper analyses the dual-link channel capacity based on simulations as well as measurements conducted using dynamic dual-link dual-polarized wideband MIMO channel sounder in an indoor office environment, and compare the results to the singlelink capacity. Here the analysis is restricted to 4 x 4 MIMO links. The following conclusions have been obtained from the analyses: 1) Compared to the single link case, the dual-link channel capacity is more affected by the SIR than the spatial separation of the users. 2) The human shadowing introduced variations of SIR up to ±10 dB, causing large fluctuations in the dual-link capacity.

This report describes results from 60 GHz channel measurements and modelling in a shielded room. Final goal of this work is to investigate potential and feasibility of 60 GHz radios for very-high-data-rate short-range communications in medical applications. The measurement in a shielded room is meaningful for studying propagation characteristics in medical applications, since real surgery rooms are typically shielded. One particular usage scenario, i.e., real-time video streaming for ultrasonic imaging, was considered, where the antenna settings were adjusted to the usage scenario accordingly. Link budget and delay domain multipath characteristics were analyzed and modelled. Finally, model parameters that fit the measured power delay profiles were given.

In this paper radio wave scattering processes in an indoor hall environment are reported by analyzing double-directional multiple-input-multiple-output (MIMO) channel sounding data at 5.3 GHz. The pathways and scattering processes of the dominant propagation phenomena were identified using a measurement-based ray tracer (MBRT) software. It is shown that the dominant propagation phenomena included a line-of-sight (LOS) or obstructed LOS component, single, double, and triple bounce scattering processes from walls and ground. The proportion of power carried by each identified pathway was studied. The number of active pathways varied between 3 and 8, which indicates that the multipath environment changes significantly during the measurement route.

We study the performance of a two-hop full-duplex OFDM relay link, where the relay, or in-band repeater, amplifies and forwards its input signal on the same channel as the main transmitter. We derive new closed-form expressions for the end-to-end signal-to-interference and noise ratio (SINR) when the multipath channels are modeled with clustered exponential power-delay profiles. Our system model incorporates the deleterious effect of loop interference associated with full-duplex relays due to signal leakage from transmission to reception. In particular, our analysis shows that the relay gain is a central parameter in the mitigation of residual loop interference and for the optimization of the end-to-end performance.

This paper aims at validation of an iterative receiver for multiple-input multiple-output with orthogonal frequency division multiplexing (MIMO-OFDM) systems using real-measurement channel data from an indoor scenario. The receiver performs iterative multi-user detection (MUD) and Channel Estimation (CE) via soft information from the single- user decoders. The channel measurements were performed for a dynamic dual MIMO link scenario. The case with two users with multiple antennas interfering each other is considered. CE at the receiver exploits the frequency correlation of the MIMO link. Simulation results for the performance are shown in terms of bit- error rate (BER) vs. signal-to-noise ratio (SNR). Performance for the whole system are provided and compared with respect to the case of perfect channel-state information (PCSI) at the receiver, as well as for the single user. We also provide an analysis of BER with respect to signal-to-interference ratio (SIR). CE performance are evaluated in terms of normalized mean square error (NMSE).

This paper investigates the applicability of deterministic ultra wideband (UWB) propagation modeling for evaluating UWB system performances. The modeling explores the wave propagation characteristics on both transmitting and receiving antenna sides, which is known as the double directional modeling. In evaluating the applicability, bit error probability (BEP) performances were derived using two kinds of channel impulse responses: 1) raw data which were measured by channel sounding campaign and 2) reconstructed data from the propagation modeling results. In the BEP simulation, the direct sequence UWB system was considered. Comparison of the BEP performances from two kinds of channels revealed that the concept of the double directional modeling was capable of evaluating BEP performances accurately. However, it was also found that the limitation of our double directional modeling approach based on the model-based ray path extraction method resulted in the limited capability in modeling the total received power. As a consequence, fading statistics of the reconstructed channels were different from the measured data, ending up with less accuracy to predict BEP performances depending on the data rate. Finally, possible solutions to improve the double directional propagation modeling were suggested.

This paper presents multipath characteristics of non-specular scattering from building surface roughness. Superresolution method was applied as an approach to handle signal parameters (DOA, TOA) of the individual incoming waves reflected from building surface roughness. In order to comprehend in detail the microscopic mechanisms of scattering, signal parameters are to be incorporated into the geometrical ray tracing. The results show that the multiple paths can he detected from many scatterers, such as ground, window glass, window frame, bricks surface, as well as directly from the transmitter. Most of the scattered waves arrives closely from specular directions.

This report presents a MIMO sounding system dedicated to short range wireless communication. The system can easily be integrated with a vector network analyzer (VNA) and other commercial equipments. The advantage of our proposed system is the achievement of completely automatic measurement, while retaining accuracy. Using the system, a double directional measurement campaign in indoor NLOS environment was performed, where the channel was estimated in a deterministic way with the ISI-SAGE algorithm. In the use of ISI-SAGE algorithm, we propose to estimate polarization characteristics for identical path. One of the realizations of the optimum search and initialization with successive interference cancellation type procedure, which is suitable for a large number of sampling, available case is shown as well. The result of the measurement campaign shows the effectiveness of our proposals.