Yang Luxi

Extracting rules from fuzzy neural network by particle swarm optimisation

A four layer fuzzy neural network is presented to realise knowledge acquisition from input-output samples. The network parameters including the necessary membership functions of the input variables and the consequent parameters are tuned and identified using a modified particle swarm algorithm which uses each particles best current performance of its neighbours to replace the best previous one and uses a non accumulative rate of change to replace the accumulative one for accelerating search procedure. The trained network is then pruned so that the general rules can be extracted and explained. The experimental results have shown that the similar classification rules can be obtained in comparison to that of other fuzzy neural approaches.

Doubly selective fading channel estimation in MIMO OFDM systems

High data transmission rates and high mobility give rise to time- and frequency-selectivity in wireless communication channels. This paper investigated time and frequency doubly selective channel estimation using pilot tones among Multi-Input Multi-Output (MIMO) orthogonal frequency division multiplexing (OFDM). Firstly, a complex exponential basis expansion channel model (BECM) was introduced to represent doubly selective channel during an OFDM symbol period; then, based on BECM, an effective MIMO-OFDM doubly selective channel estimation method was presented; finally, the optimality in designing pilot tones parameters was done according to the minimization of channel estimation MSE, mainly including the number, the placement and the structure of pilot tones. Simulation results show that the proposed estimation method has good performance in doubly selective channel scenarios and confirms the theoretical analysis findings.High data transmission rates and high mobility give rise to time- and frequency-selectivity in wireless communication channels. This paper investigated time and frequency doubly selective channel estimation using pilot tones among Multi-Input Multi-Output (MIMO) orthogonal frequency division multiplexing (OFDM). Firstly, a complex exponential basis expansion channel model (BECM) was introduced to represent doubly selective channel during an OFDM symbol period; then, based on BECM, an effective MIMO-OFDM doubly selective channel estimation method was presented; finally, the optimality in designing pilot tones parameters was done according to the minimization of channel estimation MSE, mainly including the number, the placement and the structure of pilot tones. Simulation results show that the proposed estimation method has good performance in doubly selective channel scenarios and confirms the theoretical analysis findings.

Energy-efficiency of Very Large Multi-user MIMO systems

Energy efficiency is becoming increasingly important for wireless communications as mobile devices are battery-constrained. Motivated by this, in this paper we consider uplink energy-efficient resource allocation in Very Large Multi-user MIMO systems. Specifically, both the number of antenna arrays at BS and the transmit power at the user are adjusted to maximize the energy efficiency, in which the power consumption accounts for both transmit power and circuit power. We demonstrate the existence of a unique globally optimal number of antenna arrays at BS and the transmit power and provide iterative algorithms to obtain it. Our simulation results show that the performance of the proposed algorithms is close to the optimum, while having low complexity. It is also found that the distance between the base station and the users plays an important role in increasing the energy efficiency, namely, the energy efficiency is increasing with the distance decreasing.

Downlink capacity analysis of two-hop relay OFDMA cellular network with load balancing

This paper firstly introduces a new architecture of two-hop relay OFDMA cellular network with load balancing, and then develops an analytic model of this system via two-dimensional Markov chains. In order to realize the load balancing, we propose one strategy: the hot cell borrows the idle sub-carriers from its neighboring cells through the relays and transfers users to neighboring cells. Finally, through numerical calculation, we analyze the impact of the various parameters on the performance of network with load balancing. Our results show that the two-hop relay OFDMA cellular network with load balancing can decrease the call blocking probability efficiently.

Stability analysis of nonlinear observer with application to chaos synchronization

In this paper, we first discuss the stability of linearized error dynamics of the nonlinear observer used for time-continuous driving chaos synchronization and give the criteria on it. Then we find by theoretical analysis and numerical experiments that the observer can still synchronize with the original system under time-discrete driving provided that some conditions are met. Finally we derive the asymptotical stability criterion of the nonlinear observer used for time-discrete driving chaos synchronization. Simulations illustrate the validity of the criterion.

Performance Analysis for Orthogonal Space-Time Block Codes Over Correlated MIMO Channels

In MIMO communication systems, performance analysis is very important for the comparison of different transmit schemes. In this paper, we consider three widely used modulations and use the moment generation function (MGF) approach and the Gauss- Chebyshev integration to present an efficient numerical computation method for the symbol error rate (SER) of orthogonal space-time block codes (OSTBC) over correlated MIMO channels. Our work can greatly reduce the complexity for evaluating SER and provide valuable insights into the performance of OSTBC. Finally, computer simulation results demonstrate that the new method is correct and effective.

Mutual Coupling Calibration for Smart Antennas in CDMA Communication Systems

A novel mutual coupling calibration method is presented for smart antennas in CDMA communication systems. The proposed method first uses the measured smaller mutual coupling coefficients as a prior knowledge and relies on processing the covariance matrix of the signal vector after pseudo noise (PN) despreading to estimate the other coupling coefficients and direction-of-arrivals (DOAs) of the desired users simultaneously. Then mutual coupling effect can easily be eliminated with matrix compensation technique. Compared with previous blind calibration methods, the proposed method shows less computation time and higher calibration accuracy. Computer simulation results demonstrate that the new method is correct and effective.

A system identification method using vector space base function

This paper presents a new system identification approach using vector space base functions, and proposes two network structures based on Gamma sequence and Laguerre sequence. After analyzing and comparing these structures in detail, some simulation results to demonstrate the conclusions are given.

Chaotic neural network for associative memory

Based on current research on applications of chaotic neuron network for information processing, the stability and convergence of chaotic neuron network are proved from the viewpoint of energy function. Moreover, a new auto-associative matrix is devised for artificial neural network composed of chaotic neurons, thus, an improved chaotic neuron network for associative memory is built up. Finally, the associative recalling process of the network is analyzed in detail and explanations of improvement are given.

Some statistical analysis of the recall probability of parallel intraconnected bidirectional associative memory

This paper addressed a statistical analysis for the recall of parallel intraconnected bidirectional associative memory—Modified Intraconnected Bidirectional Associative Memory 0 (MIBAM) and proved the conclusions: two MIBAM with the equal total number of neurons have the equal recalling probability form pairs of stored pattern pairs ifm is not too large. So they have the same capacity and same error correcting ability, i. e., their performances are statistically equivalent. The results of simulation support the conclusions well.