Modelling of Communication Channels for Use in Channel Equalization | |
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A signal travelling between an earth station and a satellite must pass through the earth's atmosphere. The earth's atmosphere is not a perfect communications channel as it is both non-homogeneous and dynamic (non-stationary) in nature. Imperfections in the atmosphere come from a number of sources including the ionosphere, atmospheric gases, ice crystals, cloud cover and rain. These natural phenomena cause a number of impairments to the transmitted signal such as attenuation, depolarisation, reflection, refraction, dispersion and delay. Channel equalization is the process of compensating for the effect of the physical channel between a transmitter and a receiver on the information exchanged. It is an important area in communications as it can greatly improve the quality of the information once it has been received. Improvement in the information received will lead to higher quality transmission which in turn leads to more efficient communication as re-transmission may not be as necessary. This is especially relevant to satellite communications where the information exchange is often in real-time and as such retransmission may not be an option. ApproachTo date much work has been performed in creating equalization methods which operate under the assumption of zero knowledge of the physical communication channel. However, there is no need to assume complete unawareness of the channel when it is possible to obtain, through measurement, some knowledge about it. The objective of the research is to produce a channel equalization algorithm that uses a model of the earth-satellite channel to improve accuracy and convergence properties.[Written by Mr Ismaan Ameer who was previously investigating this topic] If you are interested in this topic, please email Prof. Abdelhak Zoubir for more information. |