Blockwise Subcarrier and Bit Allocation Algorithms for Multiuser OFDM Systems

• Main Authors: I-Wei Chiu, 邱翊瑋
• Other Authors: Chin-Liang Wang
• Format: Others
• Language: en_US
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/48689050920583151918

碩士 === 國立清華大學 === 通訊工程研究所 === 93 === Multiuser orthogonal frequency division multiplexing (MU-OFDM) is a promising technique for achieving high spectral efficiency in future wireless communication systems. A key issue in MU-OFDM system is the dynamic subcarrier, bit, and power allocation among users sharing the channel. Conventional subcarrier and bit allocation algorithms assign subcarriers and bits based on “subcarrier to subcarrier” mode. It will cause large computational complexity. Therefore, some papers have proposed a blockwise subcarrier and bit allocation algorithms based on adjacent subcarriers to reduce the computational complexity. But this kind of blockwise method will cause large performance degradation due to use the average SNR value to calculate blockwise bit and power allocation. Differ from these two subcarrier and bit allocation algorithms, we propose a novel blcokwise subcarrier and bit allocation algorithm to reduce the computational complexity and performance loss. We divide the proposed blockwise subcarrier and bit allocation algorithm into two steps: first, we bind the subcarriers to blocks based on the proposed channel level classification method; second, we also propose a novel signal-to-noise ratio (SNR) value based on least-squared (LS) criterion to reduce the performance loss caused by blockwise bit and power allocation,. From the simulation results and complexity comparisons, the proposed blockwise subcarrier, bit, and power allocation algorithm with LS-SNR value can largely decrease the computational complexity and the performance loss.