Multi-user And Multi-antenna FDD Downlink System Study On Space-time Code Technology

In today's society,most of demands for wireless communications come from the growing requirements of mobile multimedia services and their applications,which continues to drive the exponential growth of mobile communications.In order to meet these demands,scholars have proposed the multiple-input,multiple-output(MIMO)technology.The main principle of this technology is to configure multiple antennas at both ends of the transceiver to obtain spatial gain and time gain.In recent years,large-scale antenna systems have been proposed in order to enable systems to implement multiple spatial data transmission links at the same time and frequency band.In this system,the base station configures a large number of antennas so that the channels between the base station and different users tend to be orthogonal,so that multiple users can communicate with the base stations at the same time and frequently band.This paper focus on multi-user,multi-antenna,frequency division duplex(FDD)downlink system.In this system,precoding techniques are used to eliminate interference between users.However,when the number of base station antennas is limited,the channel between the base station and the different users does not satisfy the orthogonality,and as the number of users increases,even if the precoding technique is utilized,the inter-user interference increases.Based on this fact,this paper proposes a transmission technique that combines precoding and space-time codes to mitigate the interference.The specific contributions are as follows:First,this paper briefly describes the channel model of the downlink of multi-user multi-antenna FDD system.Then,for the downlinks system with single antenna users,new transmission schemes and corresponding decoding methods are proposed by combining precoding technology and space-time code technology.This scheme can convert the inter-user interference into channel gain,while the linear decoding complexity is maintained.Specifically,when the number of users is equal to two,based on the Alamouti scheme,and when the number is greater than two,based on the cyclic matrix,new transmission schemes are proposed,respectively.Compared with the traditional transmission scheme,the proposed schemes can effectively convert the interference into beneficial information,while maintaining linear decoding complexity.Finally,the numerical simulation results show that the proposed transmission scheme has improved performances.