Fuzzy-Based Power Control for DS/CDMA Cellular Mobile Communication

• Main Authors: Yi-Hui Wang, 王益慧
• Other Authors: Yih-Chuan Lin
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/58330344305897235495

碩士 === 樹德科技大學 === 電腦與通訊研究所 === 91 === Fuzzy-Based Power Control for DS/CDMA Cellular Mobile Communication Student : Yi-Hui Wang Advisors : Dr. Yih-Chuan Lin Dr. Nan-Yuan Yen Institute of Shu-Te University of Computer & Communication Department ABSTRACT Direct Sequence Code Division Multiple Access (DS/CDMA) techniques have been investigated for cellular mobile radio system recently. The channel characteristics such as the multipath fading, the shadowing effect, and the path loss will make the interference even worse. Power control is essential for DS/CDMA system to combat the near-far problem and there are lots of researches on power control schemes in the literatures. The conventional feedback power control algorithms allow the base station to send a power command to either raise or lower each user transmitting signal power level by a fixed power step and then keep the received powers almost equal. However, this control scheme suffers from poor system stability, large overshoot, and long rise time. To tackle this difficulty, a fuzzy Proportional-plus-Integral (PI) control, whose input variables are the received power error and error change, is introduced to determine each user’s transmitting power in order to maintain simultaneously all users’ signal power received at the base station nearly equal and to achieve better system stability and control performance. The fuzzy-rule base is used by an inference mechanism in conjunction with some knowledge of the states of process in order to determine control actions. These control actions would lead to the fast rise time, minimum overshoot, and small root-mean-squared (rms) tracking error. We modified the membership function of [15] to improve the performance by the semicircle shape. From the simulation results, we found the modified fuzzy based scheme performed better than the tradition scheme performed of ping-pong power control.