| Summary: | 碩士 === 淡江大學 === 電機工程學系碩士班 === 96 === In the past the access of wireless network was mainly emphasized on the fixed mode transmission. As time goes by, new standards and their associated wireless communication networks have been designed and developed lately to support high mobility users. When a mobile moves around and through a series of base stations the user will receive signals not only from its serving and neighboring base stations but also from its surrounding radio environment so that the user’s received signal strength will encounter various kinds of fading and interference effects. Furthermore as the user moves its received signal strength from its serving base station may be degraded time to time and it needs to be handover to other base station to maintain its quality of communication and to avoid it from dropping of service.
In this thesis a channel model that is suitable for use in the high mobility wireless communication system is developed. In this model the mobile received signal strength is formulated it consists of two parts one is the long range signal attenuation with the accumulation of lognormal scattering factor and the other part is the fast fading attenuation that is mainly contributed from the Rayleigh fading effect. Four kinds of interferences from its neighboring base stations are discussed and analyzed, their effect on the quality of service are reviewed.
Hard and soft handoffs are considered in this thesis for mobile speed varying from low of 60 km/hr and up to 350 km/hr. The handoff phenomena and its effect on the system performance are widely discussed by varying the overlapping areas between base stations, the reuse factor, and the hysteresis value, i.e. the handoff threshold between the signal strengths of the serving and target base stations. Based on the handoff algorithm developed we have simulated many examples of the radio environments to depict the effectiveness of developed algorithm.
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