Spectrum Sharing of HAPS and Fixed Link in Millimeter Waves

A High Altitude Platform System (HAPS) is an emerging technology that can potentially bring connectivity to areas that are not partially or totally covered by cellular networks. However, allocating certain frequency bands for the HAPS alongside wireless Fixed Service (FS) imposes some restrictions on operating the HAPS systems to ensure no interference occurs between the two systems (HAPS and FS). This paper presents an analytical study of the spectrum sharing between the HAPS and the FS in millimeter waves, namely in 38- and 47-GHz bands. Some potential and significant interference scenarios have been applied in order to investigate the spectrum-sharing situations in urban and suburban areas. The Carrier to Interference plus Noise Ratio (CINR) has been adopted as the main criterion to assess the performance of the HAPS. It is found that the HAPS and FS systems can simultaneously share the 38- and 47-GHz bands with some restrictions to HAPS altitude, allowable CINR, and location of the HAPS user. These restrictions differ depending on the area coverage type

Interference coordination for LTE-advanced and FM broadcasting interoperability

The surest way to guarantee that multiple wireless systems can concurrently exist harmlessly, when operating in the same or adjacent channel, is by analyzing spectrum overlapping. This paper proposes a more accurate model to evaluate the interference power from co-channel and adjacent channel of orthogonal frequency division multiplexing-based long term evolution-advanced (LTE-Advanced) towards broadcasting frequency modulation systems at 800 MHz. Power spectral density overlapping factor is employed, and closed form of the interference power loss is derived. Numerical results demonstrate that the proposed method evaluates more exact interference power than the advanced minimum coupling loss (A-MCL) method, where the co-channel and adjacent channel interference powers are reduced by 1.3 and 3 dB, correspondingly, compared to that obtained using the AMCL method. This decreases the minimum separation distance between the two systems, which can eventually lead to efficient radio spectrum resources utilization

Asymmetric patch element reflectarray with dual linear and dual circular polarization

A reflectarray antenna consisting of asymmetrical patch elements is proposed, which is capable of producing dual linear and dual circular polarized operation at 26 GHz frequency. The main purpose of this design is to support four different polarizations using the same patch element. The proposed reflectarray has a single layer configuration with a linearly polarized feed and circular ring slots in the ground plane. Asymmetric patch element is designed from a square patch element by tilting its one vertical side to some optimized inclination. A wide reflection phase range of 600° is obtained with the asymmetric patch element during unit cell measurements. A 332 element circular aperture reflectarray is designed with the proposed configuration and experimentally validated with a linearly polarized prime feed configuration. Two different orientations of mirror and non-mirror asymmetric patch elements on the surface of reflectarray are analyzed. Dual linear polarization is obtained with the mirror orientation of the asymmetric patch elements on the surface of reflectarray. Alternatively, asymmetric patch elements without mirror orientation are demonstrated to produce dual circular polarization with the same linearly polarized feed. A maximum measured gain of 24.4 dB and 26.1 dB is achieved for dual linear and dual circular polarization, respectively. Their respective measured efficiencies are 28% and 41.3%, which are supported by a maximum −3 dB gain bandwidth of 13.8% and 11.5%. The circular polarization operation of the reflectarray is also supported by a 6 dB axial ratio bandwidth of 9.2%. The proposed asymmetric patch reflectarray antenna with polarization diversity, wide bandwidth and high gain is suitable to be used in many high frequency applications of 5G communication

Linearly polarized millimeter wave reflectarray with mutual coupling optimization

This work provides the design and analysis of a single layer, linearly polarized millimeter wave reflectarray antenna with mutual coupling optimization. Detailed analysis was carried out at 26 GHz design frequency usingthe simulations of the reflectarray unit cells as well as the periodic reflectarray antenna. The simulated results were verified by the scattering parameter and far-field measurements of the unit cell and periodic arrays, respectively. A close agreement between the simulated and measured results was observed in all the cases. Apart from the unit cells and reflectarray, the waveguide and horn antenna were also fabricated to be used in the measurements. The measured scattering parameter results of the proposed circular ring unit cells provided a maximum reflection loss of 2.8 dB with phase errors below 10°. On the other hand, the measured far-field results of the 20 × 20 reflectarray antenna provided a maximum gain of 26.45 dB with a maximum 3 dB beam width of 12° and 1 dB gain drop bandwidth of 13.1%. The performance demonstrated by the proposed reflectarray antenna makes it a potential candidate to be used in modern-day applications such as 5th Generation (5G) and 6th Generation (6G) communication systems

Site diversity against rain fading in LMDS systems

Local Multipoint Distribution Service (LMDS) is a new terrestrial fixed radio technology for broadband communication applicable that can be used to provide digital two-way voice, data, Internet, and video services or other digital services requiring high capacity traffic channels. LMDS is a point to multipoint wireless system operating at frequencies above 20 GHz, the most serious impairment at these frequencies is rain fading. In the system point of view a moving rain cell over the LMDS service area will not only attenuate the desired signal but also the interferer. Many techniques could be used to overcome rain fading. Applying Site Diversity as a possible solution to reduce the effect of rain is necessary, because a rain-cell degrades the system performance at a part of the service area but the rain can improve the carrier signal conditions elsewhere depending on the locations of the Base Station, Terminal Station and the rain-cell. The rain attenuation of different locations in Malaysia region in a given LMDS is calculated and the effects of a moving rain cell over an LMDS system are analyzed, different situations of interference according to the position of the rain-cell over the service area of LMDS are elaborated. The site diversity is implemented based on the ITU-R Recommendations to enhancement LMDS. The location dependent C/I in the LMDS service area under rainy conditions with and without site diversity technique is calculated and simulated. Different cell sizes of LMDS with and without site diversity are considered in this project for significant analyses and discussions. It is found that site diversity has high ability to improve the performance level of all LMDS service area specially under rainy conditions

Interference coupling loss between highaltitude platform gateway and fixed satellite service earth station at 5850-7075 MHz

High Altitude Platform Station (HAPS) is a new type of communications station that is expected to operate in parallel with terrestrial and satellite systems. Under agenda item 1.20 of next World Radio Conference 2012 (WRC-12), a new spectrum allocation for HAPS gateway link is proposed in the frequency band 5850-7075 MHz. Although the proposed band will provide reliable communication, the band is already saturated by the allocations of Fixed Satellite Service (FSS) earth station transmissions that have signal levels much higher than those in HAPS systems. Besides, the current HAPS spectrum sharing regulation method has limitations, such as coordination using separation distance as a dominant factor, ignoring the frequency isolation effects, and implementing Free Space Loss (FSL) model as a default propagation mechanism; thus, pessimistic results lead to large separation distances. To illuminate HAPS' chance for spectrum sharing with existing services, this paper proposes a new spectrum-sharing prediction method using the spectral technique of Net Filter Discrimination (NFD) along with the antenna height within a deployment area. Reduction in required physical isolation is achieved, and frequency isolation produces an Interference Coupling Loss (ICL) that can utilize the radio spectrum resource as efficiently as possible

Potential interference and rain attenuation at 21.4-22 GHz downlink broadcasting satellite signals

World Radio Conference WRC-1992 has allocated the frequency band 21.4-22.0 GHz to regions 1 and 3 to be utilised to carry direct broadcasting satellite (DBS) services. This high-frequency band is more susceptible to rain attenuation, leading to degradation of the signal quality. Moreover, this frequency band is assigned to two different services, i.e. satellite broadcasting and fixed mobile services at the same regions; hence, the impact of intersystem interference in a depredated signal is a critical issue in the DBS receiver. In this study, the effects of rain attenuation on the DBS downlink signals as well as the impact of the potential interference on the reception quality will be estimated. An interference scenario will be introduced to investigate the system performance in both propagation mechanisms of clear-sky and rain conditions