Spectrum Sharing Cognitive Radio with MIMO Interference Cancellation for MB-OFDM UWB System
| Autor: | Jen-Chieh Wang, 王貞傑 |
|---|---|
| Rok vydání: | 2008 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 96 In order to sharing the same frequency resource with primary users, the concept of “Cognitive Radio” is coming out. Cognitive radio defined as an intelligent wireless communication system for improving the utilization of the radio electromagnetic spectrum can be aware of its surrounding environment and then make some corresponding changes to adopt it to provide more highly reliable communication and efficient utilization of the radio spectrum. It caters dynamic spectrum management skills to prevent interference, and adapts to immediate spectrum availability. In this paper, we first introduce the idea of active interference cancellation (AIC) that how it works under some protected bands used to transmit information sent by primary subscribers or other regular radios. In short, AIC is a cognitive method that we sacrifice the side tones beside the protected frequency bands to suppress the interference below the sensitivity threshold. We’ll also show the turn-off method and then compare the effects by those two methods, AIC and turn-off approach, so that we can find that AIC behaves more excellent. Second, we bring in a multiple-input and multiple-output (MIMO) system. Recent information theory research has figured out that the employment of multiple antennas at the transmitter and the receiver induces enormous capacity increase. That is, it can meet high bit rate (or data rate) demand. That’s attractive nowadays for the deficiency of time resource and frequency resource. We mainly talk about V-BLAST (vertical Bell Laboratories Layered Space-Time), one of the BLAST techniques. V-BLAST is a MMSE-like (minimum mean square error) solution by taking MMSE skill, but it has better performance because it has fewer interferences than pure MMSE solution after the first result with MMSE. V-BLAST will make away with the first result and adapt MMSE again with left signals. From the two aforesaid ideas, the AIC algorithm and the MIMO system with V-BLAST theory, we’d like to combine their advantages to make some different transmission. When using AIC algorithm, people always intercommunicate with each other outside the protected bands and try not to make interferences with the primary users. Here we want to dispose all the frequency bands, even the protected ones. We still need obey the major premise primary users could communicate without redundant interferences so that they can transmit reliably. So we’d desire to implement a MIMO system that in the transmitters some antennas can message with receivers by making use of all the spectrums, and the others attempt to send AIC signals to cancel the blanketing from the first kind of antennas. It exhibits that the power spectrum is still clean or below the sensitivity level and at the receivers the end users employ MIMO avenues, e.g. V-BLAST to resolve the information out. These make the transmission in a secret way and only consumers who know the channel-state and measure the signals with the right MIMO approach are able to get the correct information. Receivers which don’t have these prerequisites will view these signals as noise-like interferences so that they won’t bother the major consumers too much. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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