Xuezhi Tan

A Novel Through-Wall Imaging Method Using Ultra WideBand Pulse System

Through-wall imaging is one of the applications of Ultra Wideband communication that attracts recent interests for its ability to penetrate the wall. However, the available references fail to provide a clear feasible imaging method. This paper proposes a novel virtual elliptic curve imaging method based on the UWB pulse system, which presents the detail imaging process and imaging results. The key factor of this method is to correctly obtain the propagation delay by the correlator, and it is achieved by the spread gain of the pseudo-noise sequences. The imaging results show the proposed method has very high imaging resolution. And the error analysis is investigated on account of misestimating wall parameters. Simulations illustrate the effects of the errors under different scenarios.

Asymmetric active cooperation strategy in spectrum sharing game with imperfect information

In this paper, we study the spectrum sharing problem in the cognitive network where two secondary users coexist and interfere with each other in an unlicensed channel. Each user in our scenario is independent and is unaware of the characteristic of its rival but its statistics imperfect information. An important issue is the interaction among selfish independent wireless communication systems secondary users who aim to maximize their own current utility. We provide a self-enforcing spectrum sharing framework, which has the advantage of not requiring a control center or communicating between two users. The short-term profits of users gained before cooperation being builded are asymmetrical. The long-term profit is used as the users utility. Users improve their long-term profits by creating mutual cooperation actively. The historical action of the user is used by its rival to evaluate/update the current action. The action updating algorithm is provided. Moreover, we investigate the stability of the cooperation. As demonstrated, the proposed scheme can build mutual cooperation through extensive simulations. The existence of equilibrium is confirmed by the repeated game. And our scheme can achieve a good trade-off between short-term profits and long-term profits. Copyright

Blind Source Separation Algorithm Based on Wavelet Denoising

In this paper, a method of blind source separation (BSS) is proposed based on wavelet denoising. This method firstly makes wavelet transform (WT) to the observation signals, and then adopts a uniform method which combines signal whitening and maximum information algorithm to obtain the separate signals which approach to the source signals. Simulations show this method could achieve better performance than that without wavelet denoising, and when the iterative number reaches 4000, it could achieve very good results.

Optimization algorithm for cooperative detection in cognitive radio

In cognitive radio, cooperative detection through optimization can improve the performance of spectrum sensing. In this paper, the optimal selection of cognitive radios including threshold optimization and cognitive radios selection optimization is proposed, and the sensing mechanism including sensing period optimization and sensing time optimization is also analyzed. The proposed optimization algorithm can minimize the error detection probability and maximize the average throughout. Simulations show the error detection probability of the proposed algorithm is lower than that of the cooperative detection algorithm with the settled threshold, and the cognitive radios with low SNR, which bring the negative effect to detection, can be removed, and it is also showed that the optimal sensing period and sensing time exists to decrease the detection spending time and improve the average throughout.

The Spectrum Detection and Allocation of Cognitive Radio Based on OFDM

Cognitive radio (CR) is viewed as a novel approach for improving the utilization of a precious natural resource: the radio electromagnetic spectrum. Spectrum sensing is a primary task of CR. At first, this article makes an overview of the background and concept of CR. Then focused on spectrum sensing of CR in OFDM, we put forward energy detection based on OFDM. Last this article provides two spectrum allocation algorithms: the Irrigation Algorithm with the capacity optimization and the Revision Greedy Algorithm with the minimum interference to the authorized user. Simulation shows choosing more OFDM symbols and appropriate threshold can make the total possibility of error detection reach the least and the Revision Greedy Algorithm is suited for the CR spectrum allocation.

A construction algorithm of cognitive radio network with multiobjective genetic algorithm

Cognitive Radio Network Technology brings a novel approach to share the open spectrum flexibly and efficiently. However, how to further improve the network construction for reducing the redundant information has become the hot topic. Minimum Independent Dominating Set (MIDS) in graphs is a classic problem in operations research with important application in network construction design. The single objective MIDS (SMIDS) problem can be solved efficiently, but the degree constrained and multi-objective versions are NP-hard. In this paper, according to the characteristics of cognitive radio network nods, an improved Genetic Algorithm (GA) with special crossover and mutation operators is proposed to solve the problem. Experimental results showed that the proposed method for searching multi-objective MIDS (MMIDS) with improved GA outperforms the conventional methods with heuristic algorithm search in multi-objective optimization problem. And it was therefore effectively able to select the clusters for different network simulation scenarios.

The research on the total delay and packet length of the trunking communication system based on IP network

Trunking communication system based on IP network is an innovation of the traditional trunking communication system and IP network. The IP network employs a best effort service, which is dissatisfied with the demands of the trunking communication systems quality of service (QoS) on the transfer network. In this paper the structure of the system is illustrated. And also the total delay, the key factor affecting the QoS, and the packet length are analyzed and simulated. From the simulation of the mathematical model, the relationship of the total delay and the optimal packet length under different bandwidth and traffic is got. The numerically simulated results show that the trunking communication system based on IP network is able to meet the needs of the time delay limitation of the system

A survey of trunking communications over LTE: Implementation framework, application requirements, and quality of service

Trunking communications has been widely applied in dedicated areas for many years, owning to its powerful functionality of scheduling and immediate group communication. Evolution of such services over the cellular mobile network attracts more and more interests due to its wider coverage and cheaper establishment and maintenance cost, especially with the coming era of Long Term Evolution (LTE). In this paper, a survey work is proposed to analyze the application prospects and requirements of the trunking communications over LTE. Taking the push-to-talk over cellular (PoC) as a candidate, the implementation framework is presented. Additionally, the key issues to guarantee quality-of-service (QoS) of the LTE-based PoC service are well analyzed in this paper.

Spectrum Allocation Based on Game Theory in Cognitive Radio Networks

This paper proposes a new spectrum allocation scheme based on detection probability of cognitive users. This new scheme takes a look at a cognitive radio network system composed of one primary system with several cognitive users which is combined with game theory to compensate the detection cost through detection probability. Nash Equilibrium (NE) was used to determine the cost based on the detection probability. Outcomes data revealed that in the utility function of the game, NE was stable through price adjustment. The findings shows that NE is related to the detection probability and the higher the detection probability, the more spectrum resources are in dynamic allocation and thus the higher the quality communication services for the user will gained, thus the detection cost influences the quality of the system. Finally a comparison was made between NE and Pareto Optimality to look at the necessity and conditions of possible conversion from NE to Pareto Optimality.

Competitive spectrum allocation in cognitive radio based on idle probability of primary users

Cognitive radio is recognized as an efficient way to improve the spectrum efficiency. In the distributed cognitive radio networks of multiple primary users and a secondary user, we proposed a utility function based on idle probability of primary users by using game model. The primary users can achieve the Nash equilibrium by adjusting the learning rate through repeated games. Simulations show that the primary user whose idle probability is larger, the system utility is higher and the system utility becomes the largest when the spectrum offered by primary users is totally idle. Besides, the Nash equilibrium is not efficient as the total profit of the primary users is not maximized. The cooperative optimality solution can obtain the highest system profit finally.