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A Satellite Resource Allocation for Multi-Beam Satellite Communication System
Sagawa, Yuichi,Ohata, Kohei,Ueba, Masazumi 통신위성우주산업연구회 2003 Joint Conference on Satellite Communications Vol.2003 No.-
A multi-beam system is one solution for enlarging the communication capacity by re-using the limited system frequency band, but system resources should be allocated to each user considering the interferences from vicinity beams(users). In addition, in mobile satellite systems, the resource allocation must consider user mobility and the uneven user distribution in the system and each beam. In this paper, we analyze an FDMA based multi-beam satellite system resource allocation scheme that considers both inter-beam interference and user distribution in the system in controlling both forward link power and frequency simultaneously. We confirm that this scheme enhances system capacity relative to the CDMA system, which uses the entire system frequency band.
Satellite Link Availability Analysis using 3-Dimensional Map Data
Imaizumi, Yutaka,Ohata, Kohei,Ueba, Masazumi 통신위성우주산업연구회 2006 Joint Conference on Satellite Communications Vol.2006 No.-
We propose a method of simulating satellite link availability that uses three dimensional map data. Our method calculates the satellite signal reception level at a reception point by taking into account diffracted and/or reflected waves as well as direct waves. This paper identifies simulation parameters that enable calculations that show good agreement with measured satellite signal reception levels. Our work further shows the following. 1) To calculate satellite signal levels accurately it is necessary to take into consideration diffracted and reflected waves as well as direct waves. 2) The optimum reflection coefficient of building walls and roads was 10 dB for this evaluation environment. 3) The radius of the observation area where the reflected wave was calculated was about 150 m. This choice of area was made considering CPU time required to calculate one reception point. In future work the optimum radius will be determined by evaluating the accuracy of simulation results. The results confirmed that our satellite link availability analysis can effectively predict link conditions.
Toshinaga, Hideki,Kobayashi, Kiyoshi,Ohata, Kohei,Kazama, Hiroshi 통신위성우주산업연구회 2000 Joint Conference on Satellite Communications Vol.2000 No.-
This paper proposes an interference cancellation scheme for multimedia satellite communication systems, and presents results of hardware experiments on the scheme. In order to achieve higher frequency utilization efficiency, the high-speed TDM forward link signal and the low-speed spread spectrum FDMA return link signals are superposed. The conventional interference cancellation scheme utilizes a replica signal whose amplitude, phase and timing are fixed. It is virtually impossible to adjust them properly because factors such as equipment performance and propagation conditions vary irregularly. The proposed scheme is able to generate an accurate replica by utilizing a delay variation compensator and an adaptive filter. The results of a hardware experiment show that the proposed interference cancellation scheme holds the degradation in the return link signal to less than 3dB, when D/U is greater than -37dB.
Nakahira, Katsuya,Kobayashi, Kiyoshi,Ohata, Kohei,Ueba, Masazumi 통신위성우주산업연구회 2004 Joint Conference on Satellite Communications Vol.2004 No.-
To yield a large communication capacity in future mobile satellite communication systems, a multi-beam system must be employed that has extremely high levels of frequency reuse. This paper proposes a novel resource allocation algorithm for multi-beam satellite communication systems that can dynamically offer the virtually maximum communication capacity. The algorithm optimizes frequency bandwidth, satellite transmission power, modulation level and coding rate to each beam to deal with the ever changing traffic distribution considering interference between beams. First, the optimal resource allocation is found by evaluating capacities for all possible resource allocation patterns. Although, this primitive search takes a huge amount of computer calculation power, the achieved communication capacities are higher than with conventional ones such as fixed resource system. In addition, the results of analysis clarify the the optimal condition by which all clusters have the same bandwidth allocation ratio. Second, we propose an optimal resource allocation algorithm utilizing the aforementioned condition as a constraint. By using our algorithm, which is based on sequential quadratic programming, the calculation amount can be drastically reduced. It is confirmed that the algorithm allocate the same bandwidth as that by the amount can be drastically reduced. It is confirmed that the algorithm allocate the same bandwidth as that by the primitive search method for varieties of traffic model. This means that the preposed algorithm is applicable for multi-beam satellite resource allocation.
Multicarrier/Multirate modem providing channel de-assemble and assemble functions
Tanabe, Kazuhiro,Kobayashi, Kiyoshi,Ohata, Kohei,Ueba, Masazumi 통신위성우주산업연구회 2001 Joint Conference on Satellite Communications Vol.2001 No.-
A satellite communication system for enterprise Intranets must be able to support simultaneous multi-point connections among dispersed locations and to allocate satellite channels with the required data rates of each of the connections independently. To meet these requirements, the Multicarrier/Multirate Group Modem (MCMRM) for earth stations is proposed that can process multiple and various rate. MCMRM has the following features. 1. Supports simultaneous communications with hundreds of channels. (Maximum 768) 2. The prototype modem is roughly the same size of as the conventional single carrier modem. 3. To secure flexibility and scalability, the developed modem consists of independent modules. 4. Supports the allocation of bandwidth required over dispersed frequency bands, even if continuous frequency band is not available. MCMRM consists of a multi-rate filter bank and a group modem implemented on several FPGAs controlled by a timesharing system. Evaluations show that MCMRM has even higher BER performance than a conventional single carrier modem. This paper describes the architecture and processing method of MCMRM and performance evaluation results.
An Architecture of Group MODEM with Timesharing Processing for Satellite Communication Networks
Tanabe, Kazuhiro,Sagawa, Yuichi,Kobayashi, Kiyoshi,Ohata, Kohei,Ueba, Masazumi 통신위성우주산업연구회 2002 Joint Conference on Satellite Communications Vol.2002 No.-
A satellite communication system for a mesh type network must support many multi-point connections simultaneously, and allocate satellite channels with the required data rates to support each connection independently. The conventional approach is excessively expensive since it forces the earth station to have one single carrier modem for each connection. To eliminate this problem, we introduce the Multicarrier/Multirate Group MODEM for earth stations. This new MODEM is implemented as a single LSI chip. The current version supports up to 128 communication channels simultaneously, and the bandwidth of each communication channel can be set individually. This paper describes the architecture and processing method of the modem and proposes an algorithm that decreases buffer circuit so as to reduce circuit size. Performance evaluation results are shown.
토시나가 히데키,고바야시 키요시,오하타 코헤이,우에바 마사즈미,TOSHINAGA, Hideki,KOBAYASHI, Kiyoshi,OHATA, Kohei 통신위성우주산업연구회 2001 Joint Conference on Satellite Communications Vol.2001 No.-
A bi-directional multimedia satellite communication system has been proposed to offer high-speed Internet access links. For efficient use of frequency bandwidth and transponder power, this system employs super-posed transmission scheme, which Spread Spectrum (SS) signals are superposed on the high-speed TDM signal. In order to realize this scheme, two novel technologies are introduced. They are the adaptive interference cancellation technique, and the burst mode SS demodulation technique. This paper describes the results of a system performance evaluation that uses prototypes. The measured results demonstrate that the adaptive interference canceler can eliminate interference in spite of amplitude fluctuation, and also demonstrate that the burst-mode SS demodulator can demodulate without degradation, even if there is carrier frequency error.