Kechu Yi

A survey on impulse-radio UWB localization

Impulse radio ultra-wideband (IR-UWB) technique has good performance in the application of high-precision localization since it possesses unique properties such as large instantaneous bandwidth and high time resolution. Making IR-UWB localization technology a growing hot topic in recent research field, therefore, it is necessary for us to give an overview of it in this paper. The TOA estimation, error analysis, NLOS identification and NLOS localization are studied in details based on the ranging methods. Simultaneously the UWB localization applications and practical problems are pointed out. At last, we outline the challenges for further research of IR-UWB localization.

Novel scheduling strategy for downlink multiuser MIMO system: Particle swarm optimization

In this paper the scheduling problem in downlink multiuser MIMO system is described as an optimization problem and particle swarm optimization (PSO) algorithm is introduced to address such problem. Two PSO scheduling methods with different objective functions applicable to different requirements on capacity and complexity are investigated. One is the capacity based PSO(C-PSO) scheduling method aiming at achieving the near optimal capacity; and the other is the lower bound of eigenvalue based PSO (LBE-PSO) scheduling method with the purpose of reducing computational complexity and at the same time achieving as large as possible capacity gain. Furthermore, convergence analysis of PSO from both the particle and the velocity aspects is also presented to derive the convergent condition, which is validated by several examples of different parameter values. Simulation results reveal that the C-PSO can obtain nearly the same capacity as the exhaustive search method with lower complexity, while the LBE-PSO provides a viable approach by striking a better tradeoff between capacity and computational complexity.

Multiuser Scheduling in Downlink MIMO Systems Using Particle Swarm Optimization

In this paper, a novel scheduling strategy based on particle swarm optimization (PSO) algorithm is proposed for the downlink of multiuser MIMO systems. By means of PSO searching mechanism, this scheduling algorithm mainly seeks the optimal particle, i.e. the best scheduled user group, to maximize the system capacity. Besides, a new approach to associate the possible scheduled candidates by particles in PSO is also presented. Simulation results reveal that the proposed PSO strategy achieves nearly the same performance to the exhaustive search (ES) algorithm in terms of capacity performance, but with lower complexity. The convergence analysis is also presented to give a guideline in determining the parameters to keep the PSO convergent.

Adaptive two-stage filter bank based narrowband interference suppression in DSSS systems

In this paper, we propose a cost efficient approach for narrowband interference suppression in direct sequence spread spectrum systems. Our proposed approach takes advantage of the multirate property by using cosine- and sine- modulated perfect reconstruction filter bank blocks of small size to form an adaptive two-stage tree-structured filter bank. In the first stage, an efficient complex modulated critical sampled filter bank is built to split the complex input signal into 2M real low-rate subchannel signals. The detected interfered subchannel signals are further decomposed by the second staged filter banks for narrowband interference suppression in DSSS systems. The proposed structure is cost efficient in terms of computation and storage. Simulation results demonstrate that our approach also effectively enhances the systempsilas performance.

An OFDM modulation recognition algorithm based on spectrum analysis

This paper presents the feature of energy distribution parameters for power spectrum. Then based on the spectrum analysis, an OFDM recognition method is proposed using the energy distribution parameter P, the kurtosis coefficient of the power spectrum and the power spectrum parameter R. Power spectrum is preprocessed to eliminate the effect of signal bandwidth, sampling rate, carrier frequency and FFT points on the threshold of identification. This method does not require any prior knowledge (such as symbol rate, carrier frequency, etc.), and the IF signal can be directly processed. Simulation results show that the extracted parameters have good performances in both AWGN and Rayleigh fading channel. The recognition accuracy is up to 97% with a signal to noise ratio (SNR) at 10dB.

Iteration interference cancellation decoding for multi-user MIMO uplink transmission system

In this paper, an iteration interference cancellation detector for multi-user MIMO uplink transmission system is proposed, which utilizes the special property of Orthogonal Space Time Block Code(OSTBC) equivalent channel of each user to simplify the decoding at the base station. With the proposed algorithm the number of receive antennas is significantly reduced as much as the number of users, and more spatial multiplexing gain can be obtained. Simulation results validate our proposed algorithm in terms of BER performance.

New Combining Scheme in STBC Single Carrier Block Transmission System

A new diversity combining algorithm is presented in this paper with high performance in the STBC single carrier (SC) block transmission MISO system with two transmit antennas and one receive antenna. The decision on the transmitted signal is made by STBC-based SC frequency domain equalizer (STBC-SC-FDE), and then the line of sight (LOS) component under Rician fading channels or the component with highest power under Rayleigh fading channels in the received signal is obtained by cancelling the multipath signals reconstructed by the initial detecting solution and the channel impulse response (CIR) from the received signal. Then, the LOS or the strongest component is combined using STBC-like combining scheme. The new algorithm can achieve the performance advantages dramatically over STBC-SC-FDE which is verified by computer simulations carried out in the SUI-4 and TU wireless communication link.

Suppression of Sinusoidal Frequency Modulation Interference in DSSS Systems

For the wideband nonstationary sinusoidal frequency modulation (SFM) interference in DSSS systems, the paper proposes a method to estimate partial parameters of the interference, and then an interference suppression algorithm is developed. The performance of the algorithm is analyzed. Simulations show that the algorithm can efficiently suppress the SFM interference.

A novel demodulation algorithm based on sampling with aliasing

It is a challenging problem to demodulate a linear modulation signal. The sampling theorem plays an important role in the software radio for designing the receiver. The theory of bandpass sampling gives a criterion to sample a signal without aliasing in the frequency domain. Using a different sampling frequency, the sampled signal has many different structures of the spectrum. Taking advantage of this characteristic, this paper presents a demodulation algorithm based on sampling the aliasing signal by analyzing the spectrum of some kind of linear modulation signal in an intuitionistic way. Analysis shows that this demodulation algorithm has great advantages over the traditional ones in antialiasing filter design and the design of receivers structure. This algorithm has been successfully used in our underground mine communication system.