http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Route Selection Strategy Combined with Spectrum Characteristic in Cognitive Radio Networks
Jie Chen,Shaoqian Li,Shoufeng Deng 보안공학연구지원센터 2008 International Journal of Software Engineering and Vol.2 No.2
This paper studies route selection strategy combined with spectrum characteristic in decentralized cognitive radio network. The problem is explored from two aspects: the path stability under spectrum characteristic and interference. Especially, a method that measures the interference to primary users is designed. Under this measurement method, the route selection criteria are explored based on spectrum characteristic. Theoretical analysis and numerical results shows these criteria considering interference is better than random selection.
DS-CDMA and MC-CDMA with Per-User MMSE Frequency Domain Equalization
Tao LUO,Gang WU,Shaoqian LI,Yong Liang GUAN,Choi Look LAW 보안공학연구지원센터 2008 International Journal of Hybrid Information Techno Vol.1 No.3
The future wireless mobile communication systems will be required to support high-speed transmission rate. Direct sequence code-division multiple access (DS-CDMA) and multicarrier (MC-) CDMA are two important CDMA schemes for high rate wireless communication. A novel linear per user minimum mean square error (PU-MMSE) detection technique for DS-CDMA with frequency domain equalization (FDE) based on the MMSE criterion applied per user is presented. It is shown by computer simulation that PU-MMSE outperforms conventional per carrier (PC-) MMSE for DS-CDMA with FDE in frequency selective block fading channel. Especially, in case of uplink PU-MMSE gains better performance than conventional MMSE not only for non-full-load DS-CDMA with FDE but also for full-load DS-CDMA with FDE. The performance of DS-CDMA with PU-MMSE FDE can be further promoted by successive interference cancellation (SIC). Comparing to MCCDMA with PU-MMSE FDE, DS-CDMA with PU-MMSE FDE has no performance loss and has much lower peak-to-average power ratio (PAPR).
BER-Minimizing Limited Feedback for Transmit Beamforming in MISO-OFDM Systems
Lei Zhang,Gang Wu,Shaoqian Li 보안공학연구지원센터 2008 International Journal of Multimedia and Ubiquitous Vol.3 No.2
To implement transmit beamforming, which is an effective way of leveraging the diversity gains, for multiple-input single-output orthogonal frequency division multiplexing (MISOOFDM) systems, (partial) channel state information is required at the transmitter. In this paper, we present a new limited feedback scheme in MISO-OFDM systems with transmit beamforming. By dividing the total subcarriers of an OFDM symbol into a series of clusters, from the codebook we choose the “proper” one, which minimizes the average bit error rate (BER) per subcarrier of the considered cluster, as the beamforming vector for this cluster. The scheme can reduce the feedback overhead remarkably while obtain good BER performance. Further, a simple sub-optimal algorithm exploiting the correlation of channel frequency responses at different ubcarriers is proposed to avoid exhaustive search in the optimal solution. The complexity analysis and simulations show that the proposed method has low computational complexity and provides improvement over the existing schemes.
Performance Analysis of Detection Threshold on OFDM Time Synchronization Using PN Sequences
Yuan Tian,Xia Lei,Wanbin Tang,Shaoqian Li 보안공학연구지원센터 2008 International Journal of Software Engineering and Vol.2 No.3
Many synchronization algorithms for orthogonal frequency division multiplexing (OFDM) systems have been proposed. Among them, the time synchronization algorithm by correlating the training sequence with the local known sequence can obtain good performance with a sharp synchronization peak. Detection threshold is an important and necessary parameter in time synchronization. In this paper, based on this algorithm, we evaluate three different methods of setting threshold and point out one method which performs well when SNR is in large dynamic range. The simulation results are consonant with our theoretic analyses and show that this method is suitable for OFDM systems in multi-path fading channel.