Tan Kim Geok

Solving shortest path problem using particle swarm optimization

This paper presents the investigations on the application of particle swarm optimization (PSO) to solve shortest path (SP) routing problems. A modified priority-based encoding incorporating a heuristic operator for reducing the possibility of loop-formation in the path construction process is proposed for particle representation in PSO. Simulation experiments have been carried out on different network topologies for networks consisting of 15-70 nodes. It is noted that the proposed PSO-based approach can find the optimal path with good success rates and also can find closer sub-optimal paths with high certainty for all the tested networks. It is observed that the performance of the proposed algorithm surpasses those of recently reported genetic algorithm based approaches for this problem.

A DUAL-BAND OMNI-DIRECTIONAL MICROSTRIP ANTENNA

Omni-directional antennas are useful for variety of wireless communication devices as well as capable of handling the additional different frequency bands since the radiation pattern allows good transmission and reception from a mobile unit. However, to implement the two frequencies on a single antenna with wide bandwidth can be significant because of the presence of mutual coupling and interference effects between the two radiating elements. In this paper, a novel method of combining dual-band frequencies onto a single layer board with wide bandwidth is described. A dual-band printed dipole antenna is designed in this study by combining a rectangular and two “L” shaped radiating elements and are embedded on a single layer structure with relatively small size. The obtained results show that the proposed dual-band omni-directional microstrip antenna achieves high antenna efficiency and provides better bandwidth while maintaining the structural compact size.

Objects tracking in a dense reader environment utilising grids of RFID antenna positioning

One of the fundamental constraints in radio frequency identification (RFID) large scale deployment, such as in warehouse RFID deployment, is the positioning of RFID reader antennas to efficiently locate all the tagged objects distributed in a dense RFID reader environment. For tracking the tagged objects in a dense RFID deployment, the required number of reader antennas must be optimised in order to reduce the overall cost. This study proposes highly accurate square and hexagonal grid-based positioning and tracking techniques mainly for use indoors and includes performance comparison of both of these grids. The study involves the design of the square and hexagonal grid reader antenna networks and position calculation using a diffusion algorithm. Both of these grids of RFID antenna positioning present a solution for the problem of the placement pattern of RFID reader antennas in a dense reader environment, hence an optimal number of required reader antennas and guaranteed coverage can be achieved. This study also presents a path loss model that can be applied to predict the radio signal strength information at a certain distance. The proposed diffusion algorithm estimates RFID tag position by using distance information between the reader and the tag. The obtained results show that a square grid can yield higher positioning accuracy compared to the hexagonal grid. The obtained results further show that the proposed tracking techniques can achieve an average positioning error below 1 m, which is 85% better in some cases than the results obtained by other known methods.

A NOVEL POSITIONING SYSTEM UTILIZING ZIGZAG MOBILITY PATTERN

This paper proposes a new positioning system utilizing mobile readers that are programmed to move in a zigzag pattern to locate the tags. The proposed zigzag mobility pattern is able to cover an area completely within a given period, determine optimal number of required mobile readers, and flnd out reader placement and movement pattern. The received signal strength (RSS) model is used to exchange the information over a short range by estimating the position of the tag by means of distance information between the reader and the tag. The results obtained from this study point out that the proposed method is able to provide near exact tag position. The proposed method can achieve average error as low as 0.6m. With this proposed method, the scanning of large areas, such as warehouses, libraries, and storage areas can be done very quickly. Mobile reader is proposed because it is cost-efiective, fast, and is able to provide relatively accurate results.

A new particle swarm optimization based algorithm for solving shortest-paths tree problem

This paper presents an efficient particle swarm optimization (PSO) based search algorithm for solving the single source all destination shortest paths or what is called the shortest-paths tree (SPT), commonly encountered in graph theory. A new particle encoding/decoding scheme has been devised for particle-representation of the SPT parameters. This encoding/decoding exploits the sub-optimality feature of the shortest path. In the proposed algorithm, the solution, the shortest path tree, is not represented by one particle, but it is the solution that is contributed by the complete swarm population. Numerical computation results on several networks with random topologies illustrate the efficiency of the proposed PSO method for computation of shortest paths in networks.

RFID Transponder Collision Control Algorithm

Transponder collision problem can be significant when a large number of RFID (radio frequency identification) transponders exist in field. Most existing anti-collision algorithms can solve this problem. However, problem arises when all or part of these transponders are having identical UID (unique identification). This paper proposes a new transponder collision control algorithm to overcome overlapping that occurs among transponders with identical UID in RFID large scale deployment (e.g., in a large warehouse), so that the RFID reader can successfully identify the quantity of transponders for each particular UID with high identification accuracy. The proposed anti-collision algorithm adopts a modified version of frequency domain method by adding stochastic delays in time domain. The obtained results show that the proposed method can achieve optimum frequency bandwidth utilization and at the same time poses high identification accuracy (almost 100%) with low identification delay.

Hybrid co-evolutionary particle swarm optimization and noising metaheuristics for the delay constrained least cost path problem

This paper presents a co-evolutionary particle swarm optimization (PSO) algorithm, hybridized with noising metaheuristics, for solving the delay constrained least cost (DCLC) path problem, i.e., shortest-path problem with a delay constraint on the total “cost” of the optimal path. The proposed algorithm uses the principle of Lagrange relaxation based aggregated cost. It essentially consists of two concurrent PSOs for solving the resulting minimization-maximization problem. The main PSO is designed as a hybrid PSO-noising metaheuristics algorithm for efficient global search to solve the minimization part of the DCLC-Lagrangian relaxation by finding multiple shortest paths between a source-destination pair. The auxiliary/second PSO is a co-evolutionary PSO to obtain the optimal Lagrangian multiplier for solving the maximization part of the Lagrangian relaxation problem. For the main PSO, a novel heuristics-based path encoding/decoding scheme has been devised for representation of network paths as particles. The simulation results on several networks with random topologies illustrate the efficiency of the proposed hybrid algorithm for the constrained shortest path computation problems.

A novel 3D ray launching technique for radio propagation prediction in indoor environments

Radio propagation prediction simulation methods based on deterministic technique such as ray launching is extensively used to accomplish radio channel characterization. However, the superiority of the simulation depends on the number of rays launched and received. This paper presented the indoor three-dimensional (3D) Minimum Ray Launching Maximum Accuracy (MRLMA) technique, which is applicable for an efficient indoor radio wave propagation prediction. Utilizing the novel MRLMA technique in the simulation environment for ray lunching and tracing can drastically reduce the number of rays that need to be traced, and improve the efficiency of ray tracing. Implementation and justification of MRLMA presented in the paper. An indoor office 3D layouts are selected and simulations have been performed using the MRLMA and other reference techniques. Results showed that the indoor 3D MRLMA model is appropriate for wireless communications network systems design and optimization process with respect to efficiency, coverage, number of rays launching, number of rays received by the mobile station, and simulation time.

Particle swarm optimization with noising metaheuristics for solving network shortest path problem

This paper presents an efficient particle swarm optimization (PSO) based search algorithm for solving the single source shortest path problem (SPP), commonly encountered in graph theory. A particle encoding/decoding scheme has been devised for particle-representation of the SPP parameters. The search capability of PSO is diversified by hybridizing the PSO with a noising metaheuristics. Numerical computation results on several networks with random topologies illustrate the efficiency of the proposed hybrid PSO-noising method for computation of shortest paths in networks.

Indoor Millimeter-Wave Propagation Prediction by Measurement and Ray Tracing Simulation at 38 GHz

The Millimeter-Wave (mmW) technology is going to mitigate the global higher bandwidth carriers. It will dominate the future network system by the attractive advantages of the higher frequency band. Higher frequency offers a wider bandwidth spectrum. Therefore, its utilizations are rapidly increasing in the wireless communication system. In this paper, an indoor mmW propagation prediction is presented at 38 GHz based on measurements and the proposed Three-Dimensional (3-D) Ray Tracing (RT) simulation. Moreover, an additional simulation performed using 3-D Shooting Bouncing Ray (SBR) method is presented. Simulation using existing SBR and the proposed RT methods have been performed separately on a specific layout where the measurement campaign is conducted. The RT methods simulations results have been verified by comparing with actual measurement data. There is a significant agreement between the simulation and measurement with respect to path loss and received signal strength indication. The analysis result shows that the proposed RT method output has better agreement with measurement output when compared to the SBR method. According to the result of the propagation prediction analysis, it can be stated that the proposed methods ray tracing is capable of predicting the mmW propagation based on a raw sketch of the real environment.