Interference Cancellation and Detection for More than Two Users ABSTRACT: In multiple access channels, when users know each other’s channels, precoders can be designed utilizing channel information to cancel the interference at the receiver without sacrificing the diversity or the complexity of the system. Recently, it was shown that when there are only two users,a receiver can completely cancel the interference of the two users and provide full diversity for each user. Unfortunately, the scheme only works for two users. In this paper, we extend the scheme to more than 2 users. In other words, we propose a system to achieve interference cancellation and full diversity with low complexity for any number of users. Then, we extend the results to any number of users with any number of transmit and receive antennas. Our main idea is to design precoders, using the channel information, to make it possible for different users to transmit over orthogonal directions. Then, using the orthogonality of the transmitted signals, the receiver can separate them and decode the signals independently. We also analytically prove that our system provides full diversity to each user. Simulation results confirm our analytical proof and show that our proposed scheme outperforms other existing interference cancellation schemes. BLOCK DIAGRAM: ML User 1 User 1 Encoder Noise Decoder User 2 Encoder Channel ML Decoder User 2 User 3 Encoder ML Decoder User 3 EXISTING SYSTEM: The existing multi-user systems are the small number of required receive antennas and the low complexity of the array-processing decoding. However, as mentioned before, full diversity for each user is only achieved using maximum-likelihood detection. On the other hand, maximum- likelihood detection is usually not practical, because its complexity increases exponentially as a function of the number of antennas, the number of users, and the bandwidth efficiency DISADVANTAGES OF EXISTING SYSTEM: High complexity High interference Limited users PROPOSED SYSTEM: Our main idea is to design precoders, using the channel information, to make it possible for different users to transmit over orthogonal directions. Then, using the orthogonality of the transmitted signals, the receiver can separate them and decode the signals independently. We have analytically proved that the system provides full diversity to each user and extended the results to any number of users each with any number of transmit antennas and one receiver with any number of receive antennas. ADVANTAGES OF PROPOSED SYSTEM: Full diversity achieved High interference cancellation It is applied to many no of users Low complexity DOMAIN COMMUNICATION Wireless communication is the transfer of information over a distance without the use of electrical conductors or "wires". The distances involved may be short (a few meters as in television remote control) or long (thousands or millions of kilometers for radio communications). When the context is clear, the term is often shortened to "wireless". Wireless communication is generally considered to be a branch of telecommunications. SOFTWARE REQUIREMENT MATLAB 7.9 MATLAB MATLAB is a high-performance language for technical computing. It integrates computation, visualization, and programming in an easy-to-use environment where problems and solutions are expressed in familiar mathematical notation. Typical uses include: Math and computation Algorithm development Modeling, simulation, and prototyping Data analysis, exploration, and visualization Scientific and engineering graphics Application development, including Graphical User Interface building MATLAB is an interactive system whose basic data element is an array that does not require dimensioning. This allows you to solve many technical computing problems, especially those with matrix and vector formulations, in a fraction of the time it would take to write a program in a scalar non- interactive language such as C or FORTRAN.
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