Computer Science – Performance
Scientific paper
Jan 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002iaf..confe.610n&link_type=abstract
IAF abstracts, 34th COSPAR Scientific Assembly, The Second World Space Congress, held 10-19 October, 2002 in Houston, TX, USA.,
Computer Science
Performance
Scientific paper
ground-based access systems, such as FTTH, ADSL and even terrestrial cellular systems, are only available within limited geographical areas, broadband satellite communication systems that can cover unlimited service area have attracted wide interest. However, the success of broadband satellite communication depends heavily on the cost of user terminals and satellite circuits. and frequency bandwidth, which involves design parameters. For such parameters, we must consider modulation, coding, the number of radiating beams and the number of areas in which frequency bandwidth can be reused. These parameters should be chosen such that maximum communication capacity can be provided with minimum system resources under a designated rain attenuation and interference environment. The difficulty in optimization stems from the number of design parameters and the interactions between them. The optimization also has to be done in a manner such that the service provider can determine the relation between the service cost and the service grade. The service grade can be expressed in terms of the available user information rate, return link as well as forward link, and the number of available communication channels, while the system cost can be expressed in terms of required satellite power and the bandwidth. power and bandwidth parameters. In the method, the number of spot beams, the number of repeated bandwidth areas and the type of modulation are separately determined for the return and forward link. From the selected design parameters, the relationship between bandwidth capacity and power capacity is derived assuming they are linear. The power and bandwidth required for the return and forward link are then integrated by applying a linear programming method. The constraints in linear programming are power and bandwidth. To denote the system resource management proficiency, we introduce an index called power-utilization efficiency, which is a ratio of the maximum capacity to the required power. systems that have 15 or 35 spot beams. Since circuit quality degradation in Ku band systems due to the propagation environments is less than that in Ka band systems, the power-utilization efficiency of the Ku band is 1.25 times more that of the Ka band. On the other hand, the total capacity of the Ka band is 3.5 times that of the Ku band since the allocated bandwidth in the Ku band is narrower than that of the Ka band. Bandwidth reuse is an effective way to increase total available bandwidth. For the same service area and the same number of reused bandwidths, increasing the number of spot beams can reduce the interference between different areas assigned the same frequency, since the distance between those areas widens. This enables total capacity and power-utilization efficiency for a 35-spot-beam system to be more than 2.2 and 2.75 times greater, respectively, than for a 15-spot-beam system. limited transmission power of the user terminal. Therefore, the return link transponder requires a higher transmission power level to compensate for this limitation. On the other hand, a high-quality downlink is also required for the forward link because of the small size of the user terminal antenna. However, the quality of the forward link can be maintained since it is possible to increase uplink quality by improving hub-station performance. This makes it possible to suppress the increase in the transmission power of the forward link transponder in comparison with that of the return link transponder. As an example, we compared two cases, in one of which the capacity ratio (forward link capacity divided by the return link capacity) was 2.0 and in the other of which it was 10.0. We found that the amount of capacity and power utilization efficiency were, respectively, 33% and 50% greater for the latter case than for the former case. applications.
Mitsugi Jin
Mizuno Hideki
Nakasuga Yoshinori
Ueba Masazumi
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