М.S. Krasikov - Master Student, Siberian State university of telecommunication and information (Novosibirsk) E-mail: kraskmax@mail.ru V.I. Novos - Dr.Sc. (Eng.), Professor, Siberian State university of telecommunication and information (Novosibirsk) E-mail: nvi@sibsutis.ru

Earth stations which located on the large area links one each over throw intermediate repeater mounted on artificial satellite during the construction of mobile satellite communication systems (MSCS). In constructing MSCS with zone service frequency-spatial planning tasks appears inevitably for electromagnetic compatibility since frequency marginal saving. It is necessary to consider mutual impact of beams which shape separate zones of serving area to ac-complish this tasks. Spatial construction of satellite transponder antenna determines service zones mainly [1]. It is necessary to use methods of reuse of frequency maximum number of times for the efficient use of spectrum meanwhile some frequencies must be spaced apart on the minimum possible distance [2]. Another research question is to examine effective methods of optimum frequency-spatial planning on the basis of the approaches used in the terrestrial but applied to satellite systems. It is necessary to provide low level of mutual beam impact and enough narrow directivity pattern in MSCS with MBA [3,4]. The none-quidistant concentric ring antenna arrays are mostly used in practice representing the aggregate of elements set of forming rings which have different diameters and a common center. Such antenna with few number of elements provides low side lobes level and sufficiently narrow directivity pattern about 1° [5]. Serviced area represented by operating zone of satellite transponder divided into parts corresponding to each beam of the antenna array directivity pattern. Adjacent beams affect on the energy parameters of each other. Each cell in MSCS is served by separate MBA beam [6]. The totality of the nearest cells using non-repetitive frequency channels is called a cluster. The number of cells in cluster are called as its dimension C. Assessing the impact of antenna array directivity pattern side-lobe is based on an assessment of the SINR level (Signal Interference + Noise Ratio) which is determined on the border of each beam of service area in case of interference [1]. In this case the total value of SINR is determined by the total noise level of directivity pattern lobes of interfering rays and the power of the interference noise. The formula (3) is given to calculate the SINR on the ground-to-satellite line. According to the developed technique with using the expression (3) it was assessed the level of SINR on the uplink and downlink lines under the influence of interference of the side lobes of the set of interfering beams in a single frequency network with various dimension of cluster and various configuration of AA with side from minus 17 to minus 27 dB. The results show that in the absence of interference from side lobes SINR = SNR = 16 dB on the downlink and SNR = 10 dB on the uplink. The difference between the signal / noise ratio SNR and SINR may reach 2,08 dB on the uplink and 4,95 dB on the downlink at a level SLR minus 17 dB to 3,26 dB on the uplink and 7,35 dB on the downlink at a level SLR minus 27 dB. Thus investigation showed that digital antenna arrays with low side lobes level is to be used in satellite mobile systems. Since at increasing a cluster dimension SINR increasing too then at high cluster dimension large position modulation have to be used.

 

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