Research On Interference Suppression Of Downlink In Heterogeneous Networks

With the rapid development of wireless communication,the wireless terminal equipment is increasing,so the interference between user devices becomes a hindrance to the quality of communication.In this paper,we focus on solving the interference suppression problem of user devices in three different scenarios.In the range of the LTE-A standard base station,the device-to-device pairs were introduced to improve the utilization of the cellular network spectrum.But the device-to-device pairs may cause interference to the cellular network,such as the interference caused by the device-to-device pairs to the cellular users,and the interference between the device-to-device pairs themselves.To solve the interference of the two parts,a communication method which device-to-device pairs reused the cellular network to improve the utilization rate of the spectrum is adopted.Firstly,the threshold of D2D-pairs(D2D-Ps)communication is designed to reject the D2D-Ps which were not satisfied the threshold constraint,ensuring the cellular users(CUs)have priority to use the spectrum resources.Then the interference from D2D-Ps at the receiver of CUs is eliminated first by precoding at the D2 D transmitter and decoding at the CU's receiver.Next,the interference between D2D-Ps is suppressed by using interference alignment.Performance analysis shows that the priority for which CUs use the spectrum resources has been guaranteed;the interference generated on the cellular links is well eliminated;the interference between D2D-Ps also be suppressed.In the 802.11 ac wireless local area network(WLAN),wireless intelligent devices(WID)need to be connected to the network through the wireless access point(AP),and other wireless APs in the downlink transmission will cause interference to the target WID.In this paper,we adopted a modified method based on iterative minimum mean square error interference alignment,which can suppress the interference from the other wireless APs to the target WIDs.The wireless access terminal and wireless smart devices have designed linear precoding and decoding respectively.Under the minimum mean square error criterion and the limitation of the power constraint,optimal precoding and decoding can be received.Simulation results show that the adopted method can suppress the interference from WLAN,and its transmission rate is better than the Max-SINR algorithm.In the heterogeneous network of cellular network and wireless local area network(WLAN),under the pattern of cellular network,there exists the interference caused by the base station(BS)to the WLAN user equipment(UE);under the pattern of WLAN,there exists the interference caused by the wireless access point(AP)to the non expected user equipment.The following interference suppression scheme is adopted: Design the precoding matrix at the transmitter,which maximizes the expected signal strength and reduces the interference signal strength.Design the interference suppression matrix at the receiver,which inhibits the interference of base station to WLAN user equipments and the interference of AP to the non expected user equipments.Simulation results show that the scheme can restrain the interference in heterogeneous networks,and improve the transmission rate of the heterogeneous network users.