Yuan Wen

A routing protocol with energy and traffic balance awareness in wireless ad hoc networks

The work of this paper is motivated by the idea of taking account of several factors in wireless mobile ad hoc networks (MANETs) routing design in a unified way. The rational of our motivation is that most of the routing protocols is designed only based on one criteria, e.g., shortest path considered, or power conservation. There are few works which could consider several factors in a unified way at the same time. Therefore, we propose a routing scheme which could consider power conservation, shortest path and traffic load balancing, named power and traffic balance awareness paths selection routing scheme ( PTPSR ). In this routing scheme, we would consider both the shortest path and the power conservation in an unified way. We define an energy factor as the ratio of the remaining energy over the initial energy of a node. We will use the products of the energy factors of all the nodes along different paths as the selection criteria. The higher the products of all the energy factors, the higher the remaining energy they will have, in the mean time, the higher the products of the energy factors, the fewer the number of hops along the path. We conduct simulation in Glomosim to compare the PTPSR with other routing protocols, e.g., ad hoc on demand multi-path distance vector (AOMDV). The results demonstrate that PTPSR would achieve better performance.

Strategies for an Acoustical-Hotspot Generation

Two methods for hotspot generation using multiple sources, known as time-delay (TD) method and maximum-control-gain (MCG) method are investigated in the two typical acoustical fields, namely, the free field and a rectangular room. Based on the theoretical analysis and simulations, strategies are developed according to the sound field where the target region is defined. In the free field, the MCG method can be used if the performance in terms of control gain is the priority for an optimal control, whereas the TD method is more preferable if the simplicity of implementation is the first consideration. In a room environment, if a target region is defined in the near field where the direct sound dominates, the TD method is still effective. However, in the far field where the reverberant sound prevails, only the MCG method is applicable. The near field/far field can be roughly separated according to the critical distance from the sources in the room.

Nonlinear least-square solution to flat-top pattern synthesis using arbitrary linear array

This paper presents a new approach for synthesizing flat-top patterns, based on the least-square error criterion. The cost function is formulated according to the amplitude approximation error without phase constraint. The optimal array weight is obtained by using the Levenberg-Marquardt nonlinear optimization algorithm. Simulations are performed to compare the proposed approach with the Woodward-Lawson method and two recent methods using minimax and adaptive array techniques, respectively. The results indicate that the approach is effective in sidelobe control and synthesizing prespecified patterns for arbitrary linear arrays.

Target-Oriented Acoustic Radiation Generation Technique for Sound Field Control

A multiple-source system for rendering the sound pressure distribution in a target region can be modeled as a multi-input-multi-output (MIMO) system with the inputs being the source strengths and the outputs being the pressures on multiple measuring points/sensors. In this paper, we propose a target-oriented acoustic radiation generation technique (TARGET) for sound field control. For the MIMO system of a given geometry, a series of basic radiation modes, namely, target-oriented radiation modes (TORMs) can be derived using eigenvector analysis. Different TORMs have different contributions to the system control gain, which is defined as the ratio of the acoustic energy generated in the target zone to the transmitter output power. The TARGET can be effectively applied to the sound reproduction and suppression, which correspond the generations of bright and dark zone respectively. In acoustically bright zone generation and sound beamforming, the highest-gain TORM can be employed to determine the optimal source strengths. In active noise control, the strengths of the secondary sources can be derived using low-gain TORMs. Simulation results show that the proposed method has better or comparable performance than the traditional techniques.

Application of radiation mode in desired sound field generation using loudspeaker array

The paper presents two preprocessing methods for the task of generating a desired response in a target region while simultaneously depressing the sound pressure level (SPL) in a stop region using a loudspeaker array. The first is a least squares method applying a commonly used cost function. The complex source strengths/weights are obtained by optimizing the cost function. The least squares solution may cause a low gain problem. The problem can be solved by the second method, which incorporates a radiation mode filter in the cost function. Simulations show that the second method offers the flexibility of controlling the gain of the array and still maintains the fidelity of generating the desired sound field.

A Fast Algorithm for the Sound Projection Using Multiple Sources

An algorithm for the sound projection using multiple sources is presented. The source strength vector is obtained by using a fast estimation approach instead of the conventional eigenvalue decomposition (EVD) method. The computation load is therefore greatly reduced, which makes the algorithm more efficient in practical applications.

A New Method for the Multichannel Sound Reproduction in a Prespecified Region

A preprocessing technique for the creation of a desired sound field in a target region using multiple sources is presented. The complex source strengths/weightings are obtained by an optimization in a transformed space formed by a truncated series of radiation modes, and two adaptive algorithms are developed for the optimal filter design. The truncation acts as a filter that eliminates the low gain radiation modes of the sources. Therefore, it is able to improve the efficiency of the array. Compared with conventional optimization methods, the new algorithms work on smaller dimensions with little dependence to the initial values. Simulations show that smaller square error can be achieved under the same input-power constraint