| Summary: | 碩士 === 國立交通大學 === 電機學院碩士在職專班電信組 === 96 === Diversity is a well-known technology combating fading effects in wireless communications. Diversity, in time, frequency or space, can be obtained with signals transmited through independent fading channels, and received by some combining technique. Spatial or antenna diversity has the advantage that it does not have to increase the transmition time and bandwidth. However, in many case, the transmitter have limits on its phisical size or cost. As a result, multiple antennas are either not allowed, or the diversity gain is not significant.
Cooperative diversity is a recently developed diversity technique. With the technique, a transmitter with only one antenna can have spatial diversity provided by the virtual antenna array, joined formed with other transmitters. In the literature, most works in cooperative communications focus on theoretic inverstigation. Few results are reported in the performance evaluation of real-world systems. In this thesis, we fill this gap by investigating the cooperative communications with IEEE 802.11a/g wireless LAN systems. Using well-knonw cooperative protocols, we conduct performance evaluation with extensive simulations. The results show that the performance of the wilress LAN system can be significantly enhanced through user cooperation.
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