Compressed Sensing-based CSI Feedback Assisted By Support-set

In a frequency division duplex(FDD)massive multiple input multiple output(MIMO)system,the accurate channel state information(CSI)is required by base station(BS)for downlink beamforming and user selection.Due to the large number of antennas at BS,the CSI feedback incurs significant amount of overhead in FDD massive MIMO systems.What's more,due to the limited energy and bandwidth resources at users,the CSI feedback is extremely difficult and challenging.To reduce the overhead of CSI feedback and optimize the use of bandwidth resources,the main contributions of this paper are summarized as follows:Firstly,in order to reduce the overhead of CSI feedback,a novel scheme of compressed sensing(CS)-based CSI feedback with partial support-set is studied.The small magnitude elements' support-set information and the compressed CSI are fed back to BS together.The analysis and simulation results show that,compared with conventional CS-based CSI feedback scheme,the proposed scheme can reduce feedback overhead significantly while guaranteeing the CSI recovery accuracy and system sumrate.Secondly,considering that the CS-based CSI feedback scheme with partial support-set inevitably occupies uplink bandwidth resources,it seems reasonable to introduce the superimposed coding(SC)technique into CS-based CSI feedback scheme with the partial support-set,and a novel SC-based compressed CSI feedback with partial support-set scheme is studied.The downlink CSI(DL-CSI)is superimposed on uplink user data sequences(UL-US)and then fed back to BS after quantization,modulation and spread spectrum processing.The analysis and simulation results show that,compared with SC-based CSI feedback method,the UL-US's bit error ratio(BER)and the DL-CSI's accuracy can be improved.Finally,in order to reduce the superposition interference of the SC-based compressed CSI feedback with partial support-set,this paper introduces 1-bit CS into the SC-based compressed CSI feedback with partial support-set,and then,a novel scheme of SC-based CSI feedback using 1-bit CS is studied.The compressed support-set information and DL-CSI are superimposed on the UL-US and fed back to BS after quantization,modulation,and spread spectrum processing.The analysis and simulation results show that,compared with the 1-bit compressed CSI feedback in time-division multiplexing(TDM)mode,the studied method can improve the DL-CSI's accuracy,without acquiring exclusive uplink bandwidth resources.Compared with SC-based CSI feedback method,the studied method can improve the UL-US's BER and DL-CSI's accuracy.The CSI feedback methods investigated in this paper can be applied in the wireless communication systems which employ massive MIMO technology with FDD mode,e.g.,the 5th generation wireless systems(5G),the 6th generation wireless systems(6G),and the next generation WiFi system(802.11ax/ay),etc.