Title :
Precoding in downlink multi-carrier code division multiple access systems using expectation maximisation algorithm
Author :
Haghbin, Afrooz ; Azmi, Paeiz
Author_Institution :
Electr. Eng. Dept., Tarbiat Modares Univ., Tehran
fDate :
11/1/2008 12:00:00 AM
Abstract :
The presence of multiple access interference and hardware complexity of the mobile terminal are two major burdens for multi-carrier code division multiple access schemes. Both burdens can be overcome in downlink by precoding the transmitted signal using the knowledge of the channel state information. In multi-user precoding techniques, the transmitter is optimised to combat channel impairments through the use of new spreading sequences that are obtained by solving an optimisation problem based on some criterion. Among these optimisation problems, the problem based on maximum likelihood is hard and complex to solve. In the proposed precoding scheme, the well-suited expectation maximisation algorithm is used to solve this problem. The proposed precoding technique is simulated and its performance is analysed and compared with some other precoding and detecting techniques. The results show that the proposed scheme considerably outperforms the previous precoding schemes.
Keywords :
code division multiple access; expectation-maximisation algorithm; maximum likelihood decoding; mobile radio; multiuser channels; precoding; radiofrequency interference; channel state information; downlink multicarrier code division multiple access systems; expectation maximisation algorithm; hardware complexity; maximum likelihood decoding; mobile terminal; multiple access interference; multiuser precoding techniques; optimisation problem;
Journal_Title :
Communications, IET
DOI :
10.1049/iet-com:20080046