Tuyển tập các báo cáo nghiên cứu về hóa học được đăng trên tạp chí hóa hoc quốc tế đề tài : Performance analysis of distributed ZF beamforming in the presence of CFO | Lebrun et al. EURASIP Journal on Wireless Communications and Networking 2011 2011 177 EURASIP Journal on . http content 2011 1 177 Wireless Communications and Networking a SpringerOpen Journal RESEARCH Open Access Performance analysis of distributed ZF beamforming in the presence of CFO Yann YL Lebrun1 2 Kanglian KZ Zhao3 Sofie SP Pollin2 Andre AB Bourdoux2 Francois FH Horlin1 4 and Rudy RL Lauwereins1 2 Abstract We study the effects of residual carrier frequency offset CFO on the performance of the distributed zero-forcing ZF beamformer. Coordinated transmissions where multiple cells cooperate to simultaneously transmit toward one or multiple receivers have gained much attention as a means to provide the spectral efficiency and data rate targeted by emerging standards. Such schemes exploit multiple transmitters to create a virtual array of antennas to mitigate the co-channel interference and provide the gains of multi-antenna systems. Here we focus on a distributed scenario where the transmit nodes share the same data but have only the local knowledge of the channels. Considering the distributed nature of such schemes time frequency synchronization among the cooperating transmitters is required to guarantee good performance. However due to the Doppler effect and the non-idealities inherent to the local oscillator embedded in each wireless transceiver the carrier frequency at each transmitter deviates from the desired one. Even when the transmitters perform frequency synchronization before transmission a residual CFO is to be expected that degrades the performance of the system due to the in-phase misalignment of the incoming streams. This paper presents the losses of the signal-to-noise ratio gain analytically and the diversity order semi-numerically of the distributed ZF beamformer for the ideal case and in the presence of a residual CFO. We illustrate our results and their accuracy through simulations. Keywords distributed coordinated .
