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| Sub-carrier Allocation and Power Control in Multi-user Multi-rate OFDM Systems |
| Wu Lin-jun; Li Yan-wen |
| School of Information Science and Engineering, Henan University of Technology, Zhengzhou 450001, China |
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Abstract Based on the performance analysis of the Orthogonal Frequency Division Multiplexing (OFDM) system, this paper proposes a scheme for sub-carrier allocation and power control in a multi-user multi-rate OFDM system. For the downlink transmission employing P-QAM, if all Channel State Information (CSI) are known, under the constraint of the Quality of Service (QoS) of each user being satisfied, the CBR (Constant Bit Rate) users are allocated with channels prior to the VBR (Variable Bit Rate) users. The VBR users are allocated with remain channels with the rule of link gain maximization. Signal powers are assigned with the water-filling policy: the larger is the link gain of the sub-channel, the more power is assigned. Simulation results show that the proposed sub-carrier allocation and power distribution scheme can achieve higher system capacity than Jang’s method.
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Received: 09 October 2006
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2007, Vol. 29 
