| Summary: | 碩士 === 國立清華大學 === 通訊工程研究所 === 95 === Multiuser orthogonal frequency division multiplexing (MU-OFDM) is a very promising technique for achieving high downlink data rates for future wireless networks. MU-OFDM allows multiple users to transmit simultaneously on different subcarriers during the same symbol period. The resources of the MU-OFDM systems contain power and subchannels. It is important to allocate resources to multiple users fairly and to improve the bandwidth efficiency simultaneously.
The problem of maximizing the total sum of users’ data rates subject to the constraints on the total available power and the proportionality among users’ data rates is known to be NP-hard. In the previous literature, a suboptimal subcarrier allocation algorithm with equal power distribution was provided but the fairness is rough. Based on this subcarrier allocation algorithm, an optimal power distribution technique given the fixed subcarrier assignment was also presented previously to maximize the overall data rates given the power and proportional rate constraints among users. However, it required complex iterative root-finding method to achieve the goal.
In this thesis, with the above-mentioned subcarrier allocation and constraints, we propose a closed-form formula for suboptimal power distribution in MU-OFDM systems that reduce the computational burden and require no iterative operations. By computer simulations, we show that the proposed suboptimal power allocation method achieves almost the same overall capacity as the optimal method and fairness among users can also be assured.
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