摘要
Orthogonal Frequency Division Multiplexing (OFDM) systems suffer from performance deterioration when the length of Cyclic Prefix (CP) is shorter than the Channel Impulse Response (CIR). The fundamental reason of this impairment is the InterCarrier Interference (ICI) and Inter- Symbol Interference (ISI) introduced by the excessive multipath delay. Specifically, Multiple Input Multiple Output (MIMO) beamforming is helpful in cancelling such interference since it can spatially suppress some of the multipath. In this paper, we propose an ICI eliminating beamforming scheme employing a per-tone processing approach, thus with moderate computational complexity. The ISI is removed by using a simple decision feedback equalizer, while the optimal steering and combining vectors are then derived to maximize the Signal to Interference plus Noise Ratio (SINR). This method not only achieves the beamforming benefit, but also significantly alleviates the ICI. Simulation results show that the proposed algorithm can effectively reduce the system Symbol Error Rate (SER), per- mitting good performance for multipath delay profiles that would break conventional links.
Orthogonal Frequency Division Multiplexing （OFDM） systems suffer from performance deterioration when the length of Cyclic Prefix （CP） is shorter than the Channel Impulse Response （CIR）. The fundamental reason of this impairment is the InterCarrier Interference （ICI） and Inter- Symbol Interference （ISI） introduced by the excessive multipath delay. Specifically, Multiple Input Multiple Output （MIMO） beamforming is helpful in cancelling such interference since it can spatially suppress some of the multipath. In this paper, we propose an ICI eliminating beamforming scheme employing a per-tone processing approach, thus with moderate computational complexity. The ISI is removed by using a simple decision feedback equalizer, while the optimal steering and combining vectors are then derived to maximize the Signal to Interference plus Noise Ratio （SINR）. This method not only achieves the beamforming benefit, but also significantly alleviates the ICI. Simulation results show that the proposed algorithm can effectively reduce the system Symbol Error Rate （SER）, permitting good performance for multipath delay profiles that would break conventional links.
基金
Supported by the National Science Fund for Distinguished Young Scholars (No. 60725105)
the National Basic Re-search Program of China (2009CB320404)
the Program for Changjiang Scholars and Innovative Research Team in University
the National High Technology Research and Development Program of China (2007AA01Z288)
the 111 Project (B08038)
the National Natural Science Founda-tion of China (No. 60902032, 60902033, and 60702057)
the Key Project of Chinese Ministry of Education (107103)
the Program for State Key Laboratory of Integrated Service Networks (ISN02080001)
