Effect of Antenna Beam Pattern and Layout on Cellular Performance in High Altitude Platform Communications (original) (raw)
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Optimizing an array of antennas for cellular coverage from a high altitude platform
IEEE Transactions on Wireless Communications, 2003
In a wireless communications network served by a high altitude platform (HAP) the cochannel interference is a function of the antenna beamwidth, angular separation and sidelobe level. At the millimeter wave frequencies proposed for HAPs, an array of aperture type antennas on the platform is a practicable solution for serving the cells. We present a method for predicting cochannel interference based on curve-fit approximations for radiation patterns of elliptic beams which illuminate cell edges with optimum power, and a means of estimating optimum beamwidths for each cell of a regular hexagonal layout. The method is then applied to a 121 cell architecture. Where sidelobes are modeled as a flat floor at 40-dB below peak directivity, a cell cluster size of four yields carrier-to-interference ratios (CIRs), which vary from 15 dB at cell edges to 27 dB at cell centers. On adopting a cluster size of seven, these figures increase, respectively, to 19 and 30 dB. On reducing the sidelobe level, the improvement in CIR can be quantified. The method also readily allows for regions of overlapping channel coverage to be shown.
Optimization of Beams Directions for High Altitude Platforms Cellular Communications Design
2006
Cellular communications using high altitude platforms will predominate the existing conventional terrestrial or satellite cellular systems but requires some optimization especially in the, radio coverage cellular design. In this paper either spot-beam antennas or antenna phased arrays are used in the radio coverage which is optimized in directing their beams to satisfy mostly uniform cellular layout with minimal coverage problems such as coverage gaps between cells or excessive cells overlap
Performance of Multiple High Altitude Platforms using Directive HAP and User Antennas
Wireless Personal Communications, 2005
This paper examines the behaviour of system capacity in High Altitude Platform (HAP) communications systems as a function of antenna directivity and HAP positioning. Antenna models for the user and the HAP are discussed, and it is shown that a flat sidelobe antenna pattern is suitable for modelling multiple HAP constellations when HAPs are located outside the coverage area. Using a single HAP scenario it is shown how narrowing the HAP antenna beamwidth may give better downlink Carrier-to-Noise Ratio (CNR) over the most of the coverage area. The roles of the HAP antenna beamwidth, HAP antenna pointing and HAP spacing radius are investigated. An equation is derived to determine the location of the peak CNR combined with these three parameters. A more complex multiple HAP scenario where all HAP's operate on the same channel and interfere with each other is also assessed in terms of the Carrier to Interference plus Noise Ratio (CINR) and spectral efficiency. It is shown that locating HAPs at a specific spacing radius that is outside the coverage area can improve performance. Using these techniques the combined bandwidth efficiency is shown to increase almost pro-rata when the number of HAPs is increased up to 16.
A Novel Design of Arbitrary Shaped Cells for Efficient Coverage from High Altitude Platforms
2008
This paper proposes a novel beamforming technique to form an arbitrary-shaped cell for the high altitude platforms (HAPs) mobile communications. The new technique is based on pattern summation of individual low-sidelobe narrow-beams which constitute the desired cell pattern weighted by an amplitude correcting function. The new cell pattern can be adapted to cover the main highways forming worm-shaped cells which may cover the highway for long distances up 100 km and it will has an important role in reducing frequent handoffs and signaling traffic of location updating from moving users over the long highways.
High-Altitude Platforms Cellular System for Sparsely Populated Areas
International Journal of Computer Network and Information Security, 2014
In this paper, the cellular communications using high altitude platform (HAP) will be discussed including the coverage analysis and design. The cells are analyzed showing the main parameters affecting its shape, layout and area which are important in the cellular design stage. This HAP cellular system is very important to cross the gap of difficult extension of ground infrastructure especially for sparsely populated areas needing communications services. The system design is explained where the footprint of the HAP cell is demonstrated and the overall cellular layout is established. As a case study, the coverage of the HAP cellular system is proved to cover some areas in the Kingdom of Saudi Arabia (KSA) using several scenarios such as populated as well as long highways passing through desert areas. The HAP cells are generated using spot-beam antennas which are practically candidate. The simulation results show that a single HAP can provide hundreds of microcells for urban areas while covering very long highways that can extend to several hundreds of kilometers which is very useful in covering the long highways linking sparsely separated cities in KSA.
IEEE Transactions on Aerospace and Electronic Systems, 2010
An investigation into the impact of antenna radiation patterns on the performance of a 3G mobile communication system provided a single high-altitude platform (HAP) is presented. Use of elliptical and circular beam antennas is examined for a 91-cell system. Crucial performance parameters are shown to be the mainlobe power roll-off and sidelobe level. It is presented that the optimum power roll-off from cell center to the cell edge ranges between 10-35 dB, which is dependent on the types of antennas used, sidelobe level, and antenna gain strategy employed. Elliptical beam antennas are proven to provide the best solution, but circular beam antennas with their gain adjusted to reduce the degree of cell overlap and compensate for increasing path loss are shown to provide similar performance, with the advantage that they are practically more realizable. It is shown that poorer overlap performance can be partially compensated for by an increased power roll-off at the cell edge, a strategy that is employed in the case of the gain adjusted circular beam antennas. The impact of cell radius and elevation angles is also assessed. I. INTRODUCTION Third generation (3G) mobile systems, e.g., UMTS (universal mobile telecommunications system), especially when supplemented with high-speed downlink packet access (HSDPA), should fulfill the increasing requirements for high-speed mobile data communications [1, 2]. The rapid deployment of UMTS networks is limited by many factors. In many instances, particularly in suburban and rural areas, coverage is the dominant consideration. High-altitude platforms (HAPs) will be situated in the stratosphere at an altitude from 17 to 22 km [3-6] and could be used as an alternative to a terrestrial component for UMTS 3G mobile networks or as a complementary element of terrestrial networks in providing telecommunication and data services in sparsely populated areas such as in Africa during disasters, terrorist attacks, etc. The frequency spectrum
Fixed Channel Allocation Techniques Exploiting Cell Overlap for High Altitude Platforms
An investigation is performed into the capacity enhancements achievable from various fixed channel allocation techniques exploiting overlap between the cells formed by the antenna beams from a High Altitude Platform (HAP). It is shown that the areas served by more than one cell (overlap areas) benefit from the multiplexing gain and as a result they have lower blocking than the areas served by one cell. A novel technique derived from the Erlang-B distribution is described, which imposes certain restrictions in order to limit the proportion of the channels allocated to the overlap areas and be retained for use in areas with no overlap, in order to maintain a more uniform blocking probability over the coverage area. This technique has significantly improved the capacity of the system and the spectrum efficiency.
Improving the system capacity of broadband services using multiple high-altitude platforms
IEEE Transactions on Wireless Communications, 2000
A method of significantly improving the capacity of high-altitude platform (HAP) communications networks operating in the millimeter-wave bands is presented. It is shown how constellations of HAPs can share a common frequency allocation by exploiting the directionality of the user antenna. The system capacity of such constellations is critically affected by the minimum angular separation of the HAPs and the sidelobe level of the user antenna. For typical antenna beamwidths of approximately 5 an inter-HAP spacing of 4 km is sufficient to deliver optimium performance. The aggregate bandwidth efficiency is evaluated, both theoretically using the Shannon equation, and using practical modulation and coding schemes, for multiple HAP configurations delivering either single or multiple cells. For the user antenna beamwidths used, it is shown that capacity increases are commensurate with the increase in the number of platforms, up to 10 HAPs. For increases beyond this the choice of constellation strategy becomes increasingly important.
Channel assignment strategies for a high altitude platform spot-beam architecture
The 13th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, 2002
Channel assignment strategies for use with a high altitude platform, spot beam architecture are examined. A novel power roll-off approximation is derived to allow terrestrial simulation tools to be used, and simulation performance is compared with a theoretical lower bound derived from the Engset distribution. It is shown that the use of cell overlap considerably e nhances the blocking probability performance, in addition to boosting flexibility.
The coverage, capacity and coexistence of mixed high altitude platform and terrestrial segments
2019
This thesis explores the coverage, capacity and coexistence of High Altitude Platform (HAP) and terrestrial segments in the same service area. Given the limited spectrum available, mechanisms to manage the co-channel interference to enable effective coexistence between the two infrastructures are examined. Interference arising from the HAP, caused by the relatively high transmit power and the antenna beam profile, has the potential to significantly affect the existing terrestrial system on the ground if the HAP beams are deployed without a proper strategy. Beam-pointing strategies exploiting phased array antennas on the HAPs are shown to be an effective way to place the beams, with each of them forming service cells onto the ground in the service area, especially dense user areas. Using a newly developed RF clustering technique to better point the cells over an area of a dense group of users, it is shown that near maximum coverage of 96% of the population over the service area can b...