| Summary: | 碩士 === 國立雲林科技大學 === 資訊工程研究所 === 99 === Next generation (4G) systems like LTE-A and WiMAX are designed to support universal frequency reuse (UFR) to achieve best achievable use of their valuable spectrum. While UFR is being targeted for 4G cellular wireless networks, ongoing efforts are still made to effectively eliminate the severe co-channel interference (CCI) which leads to unacceptable interference levels experienced by users near the cell edge area in cellular networks. An elaborate coordination among multiple cells called coordinated multipoint (CoMP) transmission/reception is adopted by LTE-A to improve coverage and cell-edge throughput. This paper investigates several joint precoding techniques among coordinated cell sites to address the serious CCI for downlink CoMP broadband transmission. They include joint time-division multiple access (J-TDMA), joint zero-forcing (J-ZF), joint minimum mean square error (J-MMSE), and joint null-space decomposition (J-NSD). The J-TDMA scheme is automatically free from CCI at the cost of sacrificing spectral efficiency. The J-ZF scheme enables complete suppression of interference, but is at the expense of demanding higher transmitter power on precoding process. The performance of J-MMSE is close to the J-TDMA since it makes a good tradeoff between interference suppression and transmitter power efficiency. In J-NSD, the CCI is completely removed but it comes with a penalty in that a user’s transmission is constrained to a smaller subspace. The precoding is done under the perfect channel state information and thus the simulation results in this paper provide an upper-bound reference for these precoding schemes.
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