Kazuhito Ishida

An evaluation point culling algorithm for radio propagation simulation based on the imaging method

This paper presents a three-dimensional radio propagation simulation technique that reduces its computation time. The technique is based on the imaging method, which is one of the ray tracing methods. First, the probability that propagation paths exist at evaluation points within second-order reflection is shown. The result shows that the probability is less than a few percents. Therefore, it appears that the computation time can be reduced by eliminating the calculation for evaluation points where rays never launch. Second, the algorithm implemented the idea is presented. The algorithm uses “approximated illumination area. ” There aren ′t any evaluation points outside the area. The area is solved from the coordinate relationships between the last reflected object and the last imaging point. The last imaging point is derived from recursive image generation of the transmitting point. After that, only evaluation points within the illuminated area are calculated. The computation time can be reduced to less than one-quarter of the time previously required because the calculation for evaluation points where rays don′t launch never be executed. The accuracy of the proposed method is not degraded since the method just eliminates redundancy of the path determination part of the conventional imaging method.

Cochannel Interference Cancelling Effects of MSE Processing and Viterbi Decoding in On-Board Processing Satellites

This paper presents cochannel interference cancelling techniques in on-board processing satellite systems using orthogonal polarizations. The techniques, based on mean square error (MSE) criterion and convolutional coding/soft decision Viterbi decoding (SDVD), are introduced on board. The bit error rate (BER) is derived for the mixed detection of a desired signal and an undesired cochannel interference when the techniques are applied to binary phase shift keying (BPSK), and is compared to that of no compensation for the interference. Performance results, obtained theoretically, show that the techniques of both the MSE and SDVD processings realize excellent improvements of the BER, and the improvements become significant in a large interference environment.