Mastaneh Mokayef

Omnidirectional Circularly Polarized Dielectric Resonator Antenna for 5.2-GHz WLAN Applications

The rectangular dielectric resonator antenna (RDRA) is presented to generate linearly polarized (LP) with omnidirectional radiation patterns. The proposed omnidirectional LP DRA is fed centrally by a coaxial probe and offers an impedance bandwidth of 130 MHz between 5.15 and 5.35 GHz for dB, which can be useful for 5.2-GHz WLAN applications. It is noted that by introducing several inclined slits to the diagonal and sidewalls of the RDR and also deducting a rectangular part of the top wall of the LP RDRA, degeneracy mode is excited to generate the circularly polarized (CP) fields. The proposed omnidirectional CP DRA with axial-ratio (AR) bandwidth of 210 MHz was designed for WLAN (5.15-5.35 GHz) applications. A parametric study is presented. The proposed CP DRA is built, and the characteristics of the antenna are measured. Very good agreement between numerical and measured results is obtained.

Modeling the RMS delay spread in time-varying UWB communication channels

Ultra wideband (UWB) communication is a promising technology for achieving high data rate transmission. For any system design process and testing, understanding the wireless channel behavior is essential in situations where the communication system parameters can be designed to match the studied behavior. Due to its high bandwidth, UWB channel has its own characteristics. Therefore, measurement and statistical analysis of different UWB channel parameters are needed. In this paper, we focus on the statistical analysis and modeling of the RMS delay spread of a time-varying UWB channel based on time-domain measurement. The empirical RMS delay spread values have been calculated. Based on the measurement data, the RMS delay spread has been modeled based on the probability density functions (PDFs). The cumulative distribution functions (CDFs) showed a good agreement between the empirical and the generated values.

Stationarity Regions for Ultrawideband Channels

In this letter, extracting the stationarity regions (SRs), where the channel statistics changes are insignificant, for ultrawideband (UWB) channel is achieved. SRs are found based on the correlation between consecutive power delay profiles (PDPs). The PDPs are found from channel measurement data for a frequency range of 3.1-5.3 GHz. The measured channel exhibits the sparsity behavior. Results show that the obtained SRs are between 0.27-0.32 m, where short distances show the variability of the channel. Moreover, the results are compared to standard probability density functions (PDFs). The generalized extreme value, Weibull, and exponential distributions are seen as the best fitted PDFs.

UWB channel measurement and development of scatterer identification algorithm

Ultra wideband is a promising technology for achieving high data rate communication. When channel measurements are conducted, the channel values can be extracted using CLEAN deconvolution algorithm. However, artifact paths can be generated during this process. These artifact paths are registered as channel element values representing a reflected signal from a scatterer. In reality, these mentioned paths does not represent a real scattering environment which affects accurate channel modeling. Therefore, removing the artifact paths is important to conserve better and more real scattering environment. In this paper, a scattering identification algorithm that can be used upon CLEAN algorithm is presented. It has been developed based on the geometric elliptical modeling approach. Results show that the developed algorithm can remove additional paths in a particular delay bin and conserve one channel values in that bin.

Optimizing the coexistence between HAPS platform and terrestrial system in 5.8GHz band

The 5850-7075MHz band is profoundly utilized for the fixed service such as Terrestrial Systems (TS) and microwave access (WiMAX) in various parts of the world. Nowadays, the High Altitude Platform System (HAPS) became a recognized system in this band. Therefore, terrestrial links are one of the most considerable interference with the HAPS gateway (HAPSGS) links. Hence, the legitimated interference level between HAPS and TS must be investigated to prevent performance degradation to both systems. This paper investigates the compatibility between HAPS and TS for microwave access (WiMAX) when both systems operate in co channel sharing scenario. This is done by evaluating the downlink (DL) and uplink (UL) performance of both systems. The compatibility results are based on the theoretical derivation of spectrum sharing scenario between HAPS and Terrestrial WiMAX user (TS) located in the coverage area of HAPS in high rain attenuation areas by using the deterministic methodology. This assessment has been executed in the urban area elevation angle. The performance of the system is evaluated in terms of interference to noise ratio (INR) of TS receiver inside the urban area coverage (UAC) of HAPS. Based on the study results, the minimum separation distance should be between 15 to 18 kilometers away from the reference point (i.e. Nadir Point (NP)). The isolation technique is applied in the distances less than 15 km and above 18 km in order to mitigate the interference. Consequently, the maximum isolation values should be 30.92 dB and 13.4 dB inserted between the FS and HAPS Gate Station (HAPSGS) and HAPS airship (HAPSAS) respectively to prevent the co-channel interference.