OFDM协作网络中基于组合叠加导频的信道估计技术

针对三节点放大转发(amplify-and-forward, AF)的正交频分复用(orthogonal frequency division multiplexing, OFDM)协作中继网络,为了高效获取级联和单跳链路信道状态信息(channel state information, CSI),本文提出基于组合叠加导频的信道估计方案。新方案在源节点和中继节点分别将不同的导频叠加到发送数据上,目的节点利用源导频和中继导频分别完成级联(S→R→D)信道和单跳(R→D)信道的估计。为了消除叠加导频方案中信息符号对于各链路信道估计造成的严重干扰,源导频设计采用发端预处理的数据置零叠加导频(data nulling superimposed pilots, DNSP)方式,并提出了基于协作干扰消除(cooperative interference cancelation, CIC)的中继导频设计方案,新方案一方面借助直达(S→D)链路检测符号来消除中继数据对R→D信道估计的影响,另一方面利用迭代重构来弥补源节点数据失真和提高检测性能。仿真结果表明,新方案在避免训练导频占用带宽开销的同时能获得与传统频分复用(frequency division multiplexing, FDM)导频相近的性能。

Channel estimation technology for OFDM-based cooperative systems using combined superimposed pilots

In amplify-and-forward (AF) orthogonal frequency division multiplexing (OFDM)-based coope-rative network, to acquire channel state information (CSI) of different links efficiently, channel estimation scheme based on combined superimposed training is proposed. In the new scheme, different pilots are superimposed onto the transmitted data at source nodes and relay nodes respectively while channel estimation of cascaded link(S→R→D)and single-hop link(R→D)are achieved at destination nodes using source pilots and relay pilots. In order to eliminate the severe interference for channel estimation induced by data sequence in the superimposed pilots scheme, a data-nulling superimposed pilots (DNSP) method with pre-processing at the transmitter is proposed for source pilots design. Moreover, a novel cooperative interference cancelation (CIC) method is employed for relay pilots design. The degradation on performance ofR→D channel estimation induced by cooperative data is canceled with the detected symbols fromS→D link while the information distortion is compensated and detecting performance is improved using iterative reconstruction. Simulation results are provided that the proposed scheme can eliminate the spending of bandwidth for pilots and approach the detecting performance of traditional frequency division multiplexing (FDM) schemes.