Paper Information

Journal:   TABRIZ JOURNAL OF ELECTRICAL ENGINEERING   SUMMER 2016 , Volume 46 , Number 2 (76); Page(s) 333 To 341.
 
Paper: 

OPPORTUNIST INTERFERENCE ALIGNMENT IN COGNITIVE NETWORK BY SECONDARY USERS TO TRANSMIT STBC

 
 
Author(s):  NEZAMABADI M., FALAHATI A.
 
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Abstract: 

Growing demand to access frequency spectrum, cognitive radio is introduced so that the secondary users (SU) are allowed to use unused spectrum of primary user. If the primary user (PU) uses the full frequency spectrum, the existing unused spectrum in space-domain can create ideal opportunistic interference alignment considering cognitive networks. Since the PU knows perfect channel knowledge, it can perform water-filling algorithm and singular value decomposition, then secondary users transmit along the spatial direction with the design pre-coder. In this paper, we improve the efficiency of the system with a transmit space-time coding technique introduced by Alamouti. In this regard, the SU transmit and receive antennas are reduced and after performing interference alignment algorithm, but the interference does not becomes exactly zero. In fact, to remove this interference, SU transmits Alamouti code. In this paper, we consider the case of two secondary users opportunistically exploiting the same frequency band utilized by a licensed user. Our goal is to design low-complexity precoders to realize interference cancellation for each secondary user. The main idea is to design precoders such that the two users transmit over two orthogonal spaces. As a result, the decoders can project the received signals to each of the orthogonal spaces and decode the information of each user without any interference from the other user.

 
Keyword(s): INTERFERENCE ALIGNMENT, COGNITIVE NETWORK, SPACE- TIME CODE, INTERFERENCE CANCELLATION, DEGREE OF FREEDOM
 
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