To use millimeter wave bands in future cellular and outdoor wireless networks, understanding the multipath cluster characteristics such as delay and angular spread for different polarization is very important besides knowing the path loss and other large scale propagation parameters. This paper presents result from analysis of wide-band full polarimetric double directional channel measurement at the millimeter wave band in a typical urban pico-cell environment. Only limited number of multipath clusters with gains ranging from -8dB to -26.8dB below the free space path loss and mainly due to single reflection, double reflection and diffraction, under both line of sight (LOS) and obstructed LOS conditions are seen. The cluster gain and scattering intensity showed strong dependence on polarization. The scattering intensities for ϑ-ϑ polarization were seen to be stronger compared to ϕ-ϕ polarization and on average 6.1dB, 5.6dB and 4.5dB higher for clusters due to single reflection, double reflection and scattering respectively. In each cluster, the paths are highly concentrated in the delay domain with delay spread comparable to the delay resolution of 2.5ns irrespective of polarization. Unlike the scattering intensity, the angular spread of paths in each cluster did not show dependence on polarization. On the base station side, average angular spread in azimuth and in elevation were almost similar with ≤3.3° spread in azimuth and ≤3.2° spread in elevation for ϑ-ϑ polarization. These spreads were slightly smaller than those observed for ϕ-ϕ polarization. On the mobile station side the angular spread in azimuth was much higher compared to the base station side. On average, azimuth angular spread of ≤11.4° and elevation angular spread of ≤5° are observed for ϑ-ϑ polarization. These spreads were slightly larger than in ϕ-ϕ polarization. Knowing these characteristics will be vital for more accurate modeling of the channel, and in system and antenna design.

This paper presents the radiation characteristics of a circularly polarized conical beam spherical slot array antenna for applying to the mobile satellite communication subscriber. The structure of the antenna is easy to fabricate i. e. , a ring of perpendicular slot pairs cut on an outer surface of a concentric conducting spherical cavity enclosed by the conducting conical surface with the simple feeding structure, and a linear electric probe excited at the center of the inner surface of the cavity. Radiation fields of a spherical slot array antenna are calculated by superposing the patterns of all the slots. From the numerical results of the radiation pattern, in both elevational and azimuthal planes, it is obvious that the conical beam is realized. The elevational beam direction is low, which is suitable for installing in the land mobile subscriber unit located far from the equator. The tracking system is not necessary because the azimuthal pattern is omnidirectional. Directivity of the antenna for various spherical radii and angles of slot positions are illustrated as the guidelines for the design. Experimental results are in good agreement with the predictions.

To characterize an antenna, the acquisition of its three-dimensional radiation pattern is the fundamental requirement. Spherical antenna measurement is a practical approach to measuring antenna patterns in spherical geometry. However, due to the limitations of measurement range and measurement time, the measured samples may either be incomplete on scanning sphere, or be inadequate in terms of the sampling interval. Therefore there is a need to extrapolate and interpolate the measured samples. Spherical wave expansion, whose band-limited property is derived from the sampling theorem, provides a good tool for reconstructing antenna patterns. This research identifies the limitation of the conventional algorithm when reconstructing the pattern of an antenna which is not located at the coordinate origin of the measurement set-up. A novel algorithm is proposed to overcome the limitation by resampling between the unprimed and primed (where the antenna is centred) coordinate systems. The resampling of measured samples from the unprimed coordinate to the primed coordinate can be conducted by translational phase shift, and the resampling of reconstructed pattern from the primed coordinate back to the unprimed coordinate can be accomplished by rotation and translation of spherical waves. The proposed algorithm enables the analytical and continuous pattern reconstruction, even under the severe sampling condition for deviated AUT. Numerical investigations are conducted to validate the proposed algorithm.

Conventional localization techniques such as triangulation and multilateration are not reliable in non-line-of-sight (NLOS) environments such as dense urban areas. Although fingerprint-based localization techniques have been proposed to solve this problem, we may face difficulties because we do not know the parameters of the illegal radio when creating the fingerprint database. This paper proposes a novel technique to localize illegal radios in an urban environment by interpolating the channel impulse responses stored as fingerprints in a database. The proposed interpolation technique consists of interpolation in the bandwidth (delay), frequency and spatial domains. A localization algorithm that minimizes the squared error criterion is employed in this paper, and the proposed technique is evaluated through Monte Carlo simulations using location fingerprints obtained from ray-tracing simulations. Results show that utilizing an interpolated fingerprint database is advantageous in such scenarios.

In this paper, we performed six human movement simulation by a commercial software (Poser7). We performed FDTD simulations for body area network propagation with one transmitter and six receivers. Received amplitudes were calculated for every time frame of 1/30 s interval. We also demonstrated a polarization diversity effectiveness for dynamic wearable body area network propagation.

This paper presents the performance of the Directionally Constrained Minimization of Power (DCMP) and the Zero-Forcing (ZF) in the Angular Spread (AS) environment. To obtain the optimal weights for both methods, the Extended Array Mode Vector (EAMV) is employed. It is known that the EAMV represents the instantaneous AS as well as the instantaneous DOA in the slow fading channel. As a result, it is shown that the DCMP and the ZF using the EAMV estimates can improve the Signal-to-Interference-plus-Noise Ratio (SINR) considerably, as compared with those using the Direction of Arrival (DOA) information only. At the same time, the intrinsic problems causing the performance loss in the DCMP and the ZF are revisited. From this, the reasons for the performance deterioration are analyzed, in relation with the AS, the number of samples, the number of antenna elements, and the spatial correlation coefficient of the signals. It follows that the optimal signal combining techniques using the EAMV estimates can diminish such effects.

In this paper, we evaluated the characteristics of the magnetic core loop antenna that is used to receive long wave radio signals for time standards. To evaluate the receiving sensitivity of the antenna, we calculated the antenna factor of the magnetic core loop antenna by combining a magnetic field simulation and a circuit simulation. The simulation results are in good agreement with the results obtained from the experiments. We then investigated the optimization of the antenna shape, and showed the relation between the shape of the magnetic core and the receiving sensitivity.

Effects of the model order estimation error in the TLS-ESPRIT algorithm were investigated. It was found that if the model order is overestimated true signal parameters are preserved even though spurious signals of which power values are negligibly small appear, whereas if the model order is underestimated some signals degenerate to each others, resulting in the erroneous estimates.

In this paper, an Ultra-Wideband (UWB) double-directional channel sounding measurement and spatio-temporal analysis of UWB propagation based on the clusterization approach were reported. After separating the propagation paths and diffuse components both on the transmitter (Tx) antenna and receiver (Rx) antenna positions, the propagation paths both on Tx and Rx positions were observed for clusters separately, while coupling the clusters between Tx and Rx position based on similar time of arrivals, and ray tracing by utilizing high temporal and spatial resolution, respectively. The relation between direction of departure and direction of arrival will then be investigated. For cluster properties, parameters of model characteristics are discussed and compared to other earlier works.

In this letter, we propose a new technique that reduces the computation time to derive the MEI coefficients in solving scattering problems by the Measured Equation of Invariance (MEI) methods. Methods that use the MEI technique spend most of the computation time in the integration process to derive the MEI coefficients. Moreover, in the conventional solution process, some repeated computation of metron fields to derive the MEI coefficients is included. To avoid the repeated operations and thus save computation time, we propose a matrix localization technique in computing the MEI coefficients. The time comparison for the computation of MEI coefficients of a cylinder and a sphere is given to verify the CPU time reduction of our new technique.

We introduce a MIMO channel estimation method that exploits the channel's spatiotemporal correlation without the aid of a priori channel statistical information. A simplified Gauss-Markov model that has fewer parameters to be estimated is presented for the Kalman filter. In order to obtain statistical parameters on the time evolution of the channel, considering that the time evolution is a latent statistical variable, the expectation-maximization (EM) algorithm is applied for accurate estimation. Numerical simulations reveal that the proposed method is able to enhance estimation capability by exploiting spatiotemporal correlations, and the method works well even if the forgetting factor is small.

In a shared medium communication system, mobile users contend for channel access according to a given set of rules to avoid collisions and achieve efficient use of the medium. If one or more users do not comply with the agree rules either due to selfish or malicious behaviours, they will cause some impacts on the system performance, especially to the well-behaved users. In this paper, we consider the problem of user misbehaviours on the performance of a wireless infrastructure-based network using reservation-based MAC protocols. Key misbehaving strategies possible in such a network are identified and explained. To quantify the impact of these misbehaviours upon the network performance, three different misbehaving scenarios are developed to allow a systematic investigation of each misbehaving strategy. For each scenario, we have derived mathematical formulations for evaluating and analyzing the key performance metrics, i.e., probabilities of success of well-behaved and misbehaved users and the fairness index. Numerical results show that the presence of misbehaviours can cause different levels of damage depending on the misbehavior strategy used. The combined multi-token and increasing permission probability strategies where the misbehaved user selfishly accesses the channel more times and with higher probabilities than allowed is shown to cause the most severe impairment of performance and fairness.

A compact multiple-input multiple-output (MIMO) dielectric resonator antenna (DRA) was proposed and studied. The DRA consists of three antenna ports. The antennas operate at 2.4GHz, where one of the antenna ports was placed at the center and resonates in the monopole mode, and the two other ports were located at the sides and resonate in the TEy111 mode. Both simulation and measurements were carried out, and reasonably good agreement was obtained. In addition, a study for miniaturization with different permittivities for the DRA and a comparison of the throughput with the reference antennas of a commercial wireless LAN router were performed. Our proposed MIMO DRA gave similar performance as that of the reference antennas but was more compact in size.

In the urban area, buildings are the main scatterer which dominate the mobile propagation characteristics. However, reflection, diffraction, and scattering on the building surfaces in the radio environment induce undesirable multipath propagation. Multipath prediction with respect to a building surface has been conventionally based on an assumption that reflection from the surface has a substantial specular direction. However non-specular scattering from the building surface can affect the channel characteristics as well as specular scattering. This paper presents multipath characteristics of non-specular wave scattering from building surface roughness based on the experimental results. Superresolution method was applied as an approach to handle the signal parameters (DoA, ToA) of the individual incoming waves reflected from building surface roughness. The results show that the multipaths can be detected at many scatterers, such as ground, window's glass, window's frames and bricks surface, as well as directly from the transmitter. Most of the scattered waves are arriving closely from specular directions. The measured reflection coefficients were well bounded by reflection coefficients of the theoretically smooth and random rough surface. The Fresnel reflection coefficient formula, considering the finite thickness of the building surface and Gaussian scattering correction, give better prediction for glass and bricks reflection coefficient measurement.

A new spectrum management architecture for a flexible software defined radio (SDR) is proposed. In this architecture, the SDR hardware and software are certified separately so as not to destroy the SDR flexibility, but to ensure that any combinations of hardware and software are compliant to the radio regulations even at the system (vertical) handover, global (horizontal) handover, and upgrade (forward) or downgrade (backward) handover. This architecture is based on automatic calibration & certification unit (ACU), built-in GPS receiver, and radio security module (RSM). The ACU is a hardware embedded RF manager that dynamically controls the output power spectrum to be compliant to the local radio regulation parameters. This local radio regulation parameters are securely downloaded to the hardware as an electronic label of the SDR software and stored in the RSM which is a security manager of the hardware. The GPS position check is used, especially during roaming, to keep the compliancy of the terminal to each local radio regulations managed by the geographical region. The principle parties involved in this architecture are telecommunication certification body (TCB), SDR hardware maker (HW maker), SDR software maker (SW maker), and SDR user. The roles and relationships of these four parties in the proposed architecture are clarified in this paper.

This paper presents an overview of research, development, standardization and regulation activities on ultra wideband (UWB) technologies in National Institute of Information and Communications Technology (NICT). NICT started a project on UWB technologies since 2002, and organized UWB consortium in cooperation with more than 20 companies and 7 universities in Japan. Up to now, we have been conducting numerous UWB R&D including the following main works: i) key technology development such as MMIC chips, antennas and other devices, ii) measurement and channel modeling for UWB signal propagation, iii) standardization in international activities of IEEE 802.15, ITU-R TG1/8 as well as in a national regulatory committee of Ministry of Internal Affair and Communications (MIC). The UWB systems we have studied occupy frequency bands range from microwave band (3-5 GHz) to quasi-millimeter wave band (24-29 GHz). Various prototype UWB systems including multi-functional terminals have been developed. The output of NICT has been succeeded by industrial parties with with national and international standardization and regulation.

Electronic Toll Collection (ETC), an application of Dedicated Short Range Wireless Communication (DSRC), had suffered from wrong operations due to multipath problems. To solve this problem, we proposed to apply a simple configured path determination scheme for the ETC system. The system consists of a vector network analyzer, low-noise amplifier, and X-Y positioner and achieves an automatic measurement of the spatial transfer function with emphasis on accurate measurement and reproducibility. For the reliable identification of the propagating paths, 3-D Unitary ESPRIT and SAGE algorithms were employed. Having developed the system, field experiments at the toll gate of the highway was carried out. In the measurements, we could determine many propagation paths so that the dominant propagation phenomena at the toll gate was identified. They included a ground-canopy twice reflected wave, which was a potential path that caused wrong operation. Consequently, their reflection coefficients and polarization characteristics were investigated. From the results, applicability of the path determination system for short range on-site measurement was confirmed.

Recently the effect of the angular spread caused by locally scattered signals in the vicinity of the mobile has received considerable attention. This paper proposes the Extended Array Mode Vector (EAMV) which represents the Instantaneous Angular Spread (IAS) as well as the Instantaneous Direction Of Arrival (IDOA) of the received signal at the Base Station (BS). Using the EAMV, MUSIC algorithm is generalized in order that it is possible to estimate both the IDOA and the IAS. In computer simulations, the estimates of the IDOA and the IAS in the fading situation are evaluated. The results show that the estimates for small angular spread agree well with the given values and demonstrate the validity of the proposed approach.

An RF front-end using a six-port circuit is a promising technology for realization of a compact software defined radio (SDR) receiver. Such a receiver, called a six-port direct conversion receiver (DCR), consists of analog circuit and digital signal processing components. The six-port DCR itself outputs four different linear combinations of received and local signals. The output powers are measured at each port, and the received signal is recovered by solving a set of linear equations. This receiver can easily cover a wide frequency band unlike the conventional DCR since it does not require the precise orthogonality that the conventional one does. In this paper, we propose a novel calibration method for a six-port system that includes nonlinear circuits such as diode detectors. We demonstrated the demodulation performance of a six-port DCR by computer simulation and experiments at 1.9, 2.45, and 5.85 GHz.

In this paper, a method of the signal subspace interpolation to constructing a continuous fingerprint database for radio localization is proposed. When using the fingerprint technique, enhancing the accuracy of location estimation requires very fine spatial resolution of the database, which entails much time in collecting the data to build up the database. Interpolated signal subspace is presented to achieve a fine spatial resolution of the fingerprint database. The angle of arrival (AOA) and the measured signal subspace at known locations are needed to obtain the interpolated signal subspaces. The effectiveness of this method is verified by an outdoor experiment and the estimated location using this method was compared with those using the geometrically calculated fingerprint and the measured signal subspace fingerprint techniques.