Qinghai Yang

Outage Performance of Cognitive Radio with Multiple Receive Antennas

Outage performance of cognitive radios is analyzed in this paper. The scenario under consideration requires the cognitive radio to sense whether the primary user (PU) link is free (i. e. a spectrum hole exists) before making an active transmission using that link. Multiple antennas are available at the cognitive radio link to provide array gains at the sensing stage. We derive a closed-form expression of the outage probability for cognitive transmission by classifying it into several cases. A sensing threshold is deduced according to the PU arrival model illustrated in this paper. Simulation results verify our analysis.

Chaotic Communications in MIMO Systems

In wireless communications, chaotic communications have been a field of interest due to its low complexity in hardware implementation and low power consumption in chaotic signal generation. Among the modulation schemes using the chaotic signal, Differential Chaos Shift Keying (DCSK) is a robust noncoherent technique. Multiple-input multiple-output (MIMO) system is a technology that uses multiple transmit and/or multiple receive antennas in order to improve the system performance in wireless systems. In our paper, we have proposed a new scheme of MIMO-DCSK which utilizes the benefits of MIMO system into the chaotic communication system by transmitting and receiving DCSK modulated signals through multiple antennas. Our analysis and simulation results show how the chaotic communications in the new MIMO-DCSK benefits over the single input single output (SISO) system and the BER performance of DCSK in additive white Gaussian noise (AWGN) channels using Alamouti space-time code and the maximum likelihood decoding is analyzed.

Performance Analysis of MB-OFDM System using SVD aimed LMMSE Channel Estimation.

A low rank LMMSE(linear minimum mean square error) channel estimation with variable rank is proposed for MB-OFDM(multi-band OFDM) system in this paper. A comparison is performed with an LS(least square), LMMSE channel estimation, respectively. In the real time system, it is difficult to implement LMMSE channel estimation because of its high complexity though which superior channel estimation performance. On the other hand by using the low rank LMMSE algorithm with proper rank size, we can reduce the complexity of the LMMSE but without channel estimation performance degradation. We have analyzed the system performance of LS, LMMSE and low rank LMMSE with variety of the number of rank under the IEEE 802.15.3a channel model. The performance analysis provides an appropriate number of rank depending on the channel characteristics. Low rank LMMSE can be implemented in the real time with obtained number of rank without performance degradation, which is shown by our simulation results.

Outage Probability Analysis for Cognitive Radios with Reception Diversity

Outage probability for cognitive radios is investigated in this paper. The scenario under consideration requires the cognitive radio to sense whether the primary user (PU) link is free (or exists a spectrum hole) before making an active transmission using that link. The use of multiple antennas at the cognitive receiver provides array gains at the sensing stage. We derive a closed-form outage probability for cognitive transmissions by classifying them into several cases.

Singular Value Decomposition-Based Algorithm for IEEE 802.11a Interference Suppression in DS-UWB Systems*This research was supported by University IT Research Center Project of Inha UWB-ITRC, Korea.

Coexisting with many concurrent narrowband services, the performance of UWB systems will be affected considerably by them. Specifically, IEEE 802.11a systems which operate around 5 GHz and overlap the band of UWB signals will interfere with UWB systems significantly. In this paper, a novel narrow-band interferences (NBI) suppression technique based on singular value decomposition (SVD) algorithm for a direct sequence ultra-wideband (DS-UWB) communication system is presented. SVD is used to approximate the interferences which then are subtracted from the received signals. The proposed technique is simple and robust. Simulation results show that the proposed new technique is very effective.

Performance analysis of fast handoff with mobility prediction

A location-aided handoff reservation scheme with mobility prediction for wireless cellular networks is proposed in this study. We analyze the performance of the proposed handoff reservation scheme and propose a two-dimensional (2-D) random walk model for simulation to show its effectiveness. The influences of the threshold distance and mean value of the distance that the mobile station moves in a straight line are also investigated.

Outage Performance of Cooperative DF Relaying in Rayleigh Fading with Multiple Receive Antennas at Destination

We address the outage performance in the Rayleigh fading for the decode-and-forward relaying with multiple receive antennas at the destination. A closed-form expression for the outage probability is derived. Simulation results demonstrate our theoretical solutions.

A Novel Cross Layer NFCAC Game Algorithm in IEEE 802.16-based Multi-radio Heterogeneous Ad Hoc Networks

The special scenario of the topology in the IEEE 802.16-based multi-radio heterogeneous ad hoc networks was analyzed and a novel cross layer game algorithm based on neural fuzzy connection admission controller (NFCAC) was proposed in this paper. NFCAC has been successfully applied in the control-related problems of neural networks. However, there is no discussion about the power control game algorithm and location recognition based on NFCAC in heterogeneous ad hoc networks. The proposed algorithm integrated the attributes both of NFCAC and the topology space in special scenario. The topology and the power consumption of each node can all be optimized due to the minimum link occupation with the help of the algorithm. Simulation results show that the novel algorithm can give more power control guarantee to heterogeneous ad hoc networks in the variable node loads and transmitting powers, and make the node more stable to support multi-hops at the same time.

Resource Reservation for Handoff Using Location-Aided Mobility Prediction

In this paper, a resource reservation scheme for handoff using location-aided mobility prediction is proposed for wireless cellular networks. We analyze the performance of the proposed scheme and propose a two-dimensional random walk model for performance evaluation. The influences of threshold distance, average distance where the mobile station moves along a straight line and location error are investigated. The effectiveness of mobility prediction is also evaluated. Performance comparison reveals that the proposed scheme performs better than the solely distance-based scheme without mobility prediction

Outage Performance of Opportunistic Amplify-and-Forward Relay under Nakagami Fading

The outage performance for the opportunistic amplify-and-forward relaying strategies under Nakagami-m fading channels is investigated in this paper. A closed-form expression for the outage probability is derived. Simulation results verify our theoretical solutions.