Statistical characterization of urban spatial radio channels

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

An Additive Model as a Physical Basis for Shadow Fading

Received signal power in mobile wireless communications is typically modeled as a product of three factors: distance-dependent average path loss law, variation in the local mean power (shadow fading), and small-scale fading. Of these three factors, the least investigated is the shadow fading, which is usually explained as a result of multiplication of large number of random attenuating factors in the radio channel. In this paper, the authors propose an additive model as an alternative physical basis for shadow fading within an "extended local area" where path loss is constant. Starting from a sum-of-sinusoids signal model, they show that under mild statistical assumptions on the powers of the sinusoids, the resulting signal power will have approximately Gaussian distribution in logarithmic scale. A cluster-based model for shadow fading emerges as a special instance of the general result. They present simulation and measurement results that support their theoretical findings. The new physical basis for shadow fading also provides insights into simulation and modeling of radio channels     

Approximate distribution of capacity of Rayleigh fading MIMO channels

Approximate closed-form density and distribution functions for the capacity of multiple-input multiple-output (MIMO) radio systems in spatially semi-correlated Rayleigh fading channels are derived. The approximations are given in terms of the Meijer G-function, hence allowing easy numerical evaluation of capacity outage probabilities with, for example, Maple or Mathematica.     

Influence of antenna configurations on performance of STBC in urban microcells

Based on urban microcell channel measurements, the bit error rate performance of a space-time block code with four transmit antennas using various dual-branch receive antenna configurations, is evaluated. It is demonstrated that with realistic handset antennas, it is possible to achieve performance very close to that of the theoretical uncorrelated Rayleigh case, although proximity of operator tissue (e.g. head) will result in several decibels performance degradation.     

Empirical characterization of wideband indoor radio channel at 5.3GHz

Characteristics of wideband indoor radio channel at 5.3 GHz were defined based on an extensive measurement campaign using a wideband channel sounder with 19 ns delay resolution. Pathloss exponents were 1.3-1.5 in LOS and 2.9-4.8 in non-line of sight (NLOS). Large difference in NLOS exponents was due to different dominating propagation mechanisms in different types of building structures. The delay dispersion was characterized by cumulative distribution functions (CDF) of the RMS delay spreads, the values for CDF=0.9 varied from 20 to 180 ns in different setups in an office building and large hall environments. The correlation functions of the radio channel in spatial and frequency domains were extracted. Small scale models for five typical indoor scenarios were developed using tapped delay lines     

Polarization Behaviours at 2, 5 and 60 GHz for Indoor Mobile Communications

The behaviours of linear polarizations at 2.15, 5.3 and 61.7 GHz in corridors are studied in this paper. It shows that there is no significant difference between the received powers for vertical and horizontal polarizations. Depolarization is obvious at 2.15 GHz due to different antenna type is applied at the receiver, and it is more serious in non-line-of-sight (NLOS) cases.     

On the relationship between peak factor of a multicarrier signal and aperiodic autocorrelation of the generating sequence

The well-known relationship between the peak-to-average power ratio (PAPR) of a multicarrier signal and the autocorrelation coefficients of the generating sequence is discussed. We emphasise that low values of the autocorrelation coefficients represent only a sufficient condition for a small value of the PAPR of the signal. Therefore, the autocorrelation coefficients of the generating sequences cannot serve as a basis for comparison of PAPR of the corresponding signals.     

Coupling Element-Based Dual-Antenna Structures for Mobile Terminal with Hand Effects

This paper presents a comprehensive simulation study on the performance of coupling element-based dual-antenna structures on a mobile terminal at the 2,000 MHz Universal Mobile Telecommunications System (UMTS) frequency band with varying two significant hand effects; vertical position of hand along terminal chassis, and distance between hand palm and terminal chassis. The results reveal that in uniformly distributed isotropic environment, there exists a gain imbalance between antenna elements due to hand effects and it is shown that a gain imbalance of 3.7 dB lead to a reduction of 1.9 dB in diversity gain at 99% reliability level using maximal ratio combining (MRC) technique. For a dual-antenna configuration, the impact of gain imbalance on diversity gain is more significant when only one antenna element is in close proximity to the hand, compared to when both antenna elements are in the presence of the hand. It is also shown that a dual-antenna structure with elements vertically oriented along the edges of a small 100 mm × 40 mm mobile terminal chassis achieves better performance in port-to-port isolation, gain imbalance and diversity gain compared to other studied dual-antenna configurations when the user’s hand is present.     

Near-field scanner for the detection of passive intermodulation sources in base station antennas

Passive intermodulation (PIM) distortion is a challenging problem in the design and manufacturing of base station antennas. Small nonlinearities, typically in junctions, may cause a distortion signal that interferes with the receiver even with a level of -155 dBc in a GSM900 system. The PIM level specification of an outdoor base station antenna is difficult to achieve and the sources of PIM generation are laborious to track down. In this paper, a near-field measurement method is presented to localize and investigate passive intermodulation sources in antennas and open transmission lines. The principle of the PIM near-field measurement is otherwise the same as in a common reactive near-field measurement, but instead of measuring the signal at the input frequency, the signal amplitude and phase at the PIM frequency of interest are acquired. The constructed measurement system is capable of measuring PIM signal levels down to -110 dBm with 2/spl times/43 dBm transmit power in the GSM900 frequency band. As demonstration measurements, PIM sources in a two-element base station antenna and in a microstrip line are localized.