Browsing by Author "Mekonnen, Elleni"

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    Cooperative Diversity for Broadband Vehicular Communication under Doubly-Selective Channel
    (Addis Ababa University, 2014-09) Mekonnen, Elleni; Hailemariam, Dereje (PhD)
    Previous works on vehicular communication assume the channel to be frequency-flat and quasi-static. But this assumption is unrealistic in now days where communication takes place at a high data rate and also when large number of reflectors are present between transmitter and receiver. These factors introduce frequency-selective behavior to the channel and also the movement of reflectors and/or communicating terminals makes the channel to be time-selective. Therefore it is better to assume our channel to be doubly-selective. Mitigation techniques are required to have a reliable communication in this type of channel. Precoding, equalizer and cooperative communication are considered as mitigation techniques in this thesis work. Selection Combining (SC) and Equal Gain Combining (EGC) are used as diversity combining scheme. It is assumed that the relay just amplifies and forwards (AF) the information it has received from the source. Simulation results show that cooperative diversity along with precoding and equalizer improves the performance of fading channel and hence provide a better service even in the worst type of fading channel i.e., doubly-selective channel. Taking a fixed bit error rate (BER) of 10-4, performance was improved by 2.5dB for EGC scheme and by 0.5dB for SC. Key Words: Doubly-selective channels, Equalizer, Precoding, Cooperative communication, Diversity combining.