Based On The Mixed Iterative Space-time Technology Research

Multi-access technology is one of the key technologies of wireless communications, and its core content is how to make multiple users share the limited resources without interfering each other. Li Ping etc. have proposed a promising noval multi-access approach based on CDMA, which is called Interleave-Division Multiple-Access (IDMA). IDMA uses low code rate coding scheme to maximize the coding gain, performs chip-by-chip interleaving, uses different interwoven to identify users and thus avoids the code resource constraints of channel coding. At the receiver. IDMA employs chip level Turbo iterative detection scheme. Compared with the traditional CDMA system, it can overcome the Multi-Access Interferences (MAI) effectively even with quite low system complexity. Interleave iterative detection technology is just the most important basis for IDMA to achieve excellent performance.On the other hand, space-time technologies have muti-input multi-output technology as its representative. As one of key technologies in the next generation of wireless communication, space-time technologies are able to provide reliable broadband data services by utilizing limited frequency spectrum resource. Besides, as a virtual technology of Multiple-Input Multiple-Output (MIMO), cooperative communication combines advantages from both diversity technique and relay transmission technique. Furthermore, cooperative communication combined with network coding could improve the system transmission efficiency and enlarge the capacity and stability of entire network.In recent years, the demand for broadband multimedia services has promoted the development of the whole broandband communications network. Traditional wireless communications systems grow rapidly both in performance and capacity through the introduction of large amounts of advanced technologies. In addition to studying interleave iterative technique and space-time technology in the traditional wireless communications, we also pay attention to terrestrial wireless atmospheric optical communications. Light is the best carrier of broadband information and the rapid development of optical fiber communications has proved this point. Different from optical fiber communications in application fields, terrestrial wireless atmospheric optical communications is more suitable for broadband wireless access. For example, in places with strong electromagnetic interference, temporary or mobile spaces, places not easy to set wires, it’s very suitable to use free-space optical communication technologies.This paper outlines the research background and status of related techniques at first, and then introduces in detail the basic principles and realization of IDMA technology. Then we research the interleaved iterative systems under different types of modulation and coding scheme. On this basis, we propose a network-coded non-orthogonal multi-access user cooperative system. It contains technologies such as interleave iterative detection, convolutional coding, relay cooperative scheme, network coding. We analyze the system capacity and perform some computer simulations. Next, we design an Interleave-Division-Multiplexing (IDM) based MIMO Free-Space Optics (FSO) communication system. In this system, we employ the Gamma-Gamma turbulence-induced fading channel model. It can accurately simulate the turbulent atmospheric channel in actual situations. Expression of an upper bound of Frame-Error-Rate (FER) is derived. And it makes assessing transmission performances much more simple and quick compared to computer simulations.