Pisit Boonsrimuang

Mobile Internet navigation system

This paper presents a mobile Internet navigation system (MINS) which can provide traffic-condition acquisition and monitoring convenience for mobile phone users by using the wireless application protocol (WAP) format. This system operates in two ways. Firstly, mobile phone users can access the network to request road traffic information from the database of the server. This feature is useful to a user in planning the optimum route to a destination. Secondly, the user can monitor real time traffic information on the screen of the mobile phone. The traffic information includes quantity of cars for both main roads and their branch roads. These data are collected from sensors at all locations and are relayed to the clients computer by the traffic controller via the Internet and are stored at the database in the server. This system enables mobile phone users to acquire real time traffic condition data from the server for deciding the optimum road route in their travels.

Proposal of Improved PTS Method for OFDM Signal

The major drawback of orthogonal frequency division multiplexing (OFDM) is a large Peak-to-Average Power Ratio (PAPR). To overcome the PAPR problem, many PAPR reduction methods have been proposed. Partial Transmit Sequence (PTS) method is a well known method to reduce the PAPR statistics of an OFDM signal. The PTS method can reduce the PAPR by controlling the multiplied weighting factor of subblock both data sub carrier and clusters. The PTS method can improve PAPR reduction performance very well as increasing a number of weighting factors and clusters. However, the number of side information is proportionally increasing as increased number of weighting factors or/and clutters, which are required to inform the side information to the receiver for recovering the original data. In this paper, we propose the new weighting factor which can improve the PAPR reduction performance better than conventional PTS method. The proposed method doesnpsilat have any additional number of side information and system complexity. The proposed method can achieve both a better PAPR performance and BER performance with keeping the same number of side information when compare with the conventional PTS method. This paper presents various computer simulation results to verify the effectiveness of proposed method in the multi-path fading channel.

Proposal of Clipping and Inter-Modulation Noise Mitigation Method for OFDM Signal in Non-linear Channel

One of the disadvantages of using OFDM is the larger peak to averaged power ratio (PAPR) of the time domain signal as compared with the conventional single carrier transmission method. The OFDM signal with larger PAPR will cause the undesirable spectrum regrowth and the larger degradation of bit error rate (BER) performance both due to the inter-modulation products occurring in the non-linear amplifier at the transmitter. The clipping method in conjunction with the Decision Aided Reconstruction (DAR) method is well known as one of the solutions to improve the BER performance with keeping the better PAPR performance. However, the DAR method is proposed to mitigate only the clipping noise and not for the inter-modulation noise. In this paper, we propose the Improved DAR (IDAR) method, which can mitigate both the clipping noise and inter-modulation noise on the basis of DAR method. The proposed method enables the efficient usage of transmission power amplifier at the transmitter with keeping the better PAPR and BER performances. This paper presents various computer simulation results to verify the performance of proposed IDAR method in the non-linear channel.

A Support Vector Machine-Based Particle Filter Method for Improved Flooding Classification

Support vector machines (SVMs) have been applied to land cover classification, and a number of studies have demonstrated their ability to increase classification accuracy. The high correlation between the data set and SVM training model parameters indicates the high performance of the classification model. To improve the correlation, research has focused on the integration of SVMs and other algorithms for data set selection and SVM training model parameter estimation. This letter proposes a novel method, based on a particle filter (PF), of estimating SVM training model parameters according to an observation system. By treating the SVM training function as the observation system of the PF, the new method automatically updates the SVM training model parameters to values that are more appropriate for the data set and can provide a better classification model than can the original model, wherein the parameters are set by trial and error. Various experiments were conducted using Radarsat-2 synthetic aperture radar data from the 2011 Thailand flood. The proposed method provides superior performance and a more accurate analysis compared with the standard SVM.

PAPR Reduction Method for OFDM Signal by Using Dummy Sub-carriers

One of the disadvantages of using OFDM is the larger peak to averaged power ratio (PAPR) in its time domain signal. The larger PAPR signal would course the fatal degradation of bit error rate performance (BER) due to the inter-modulation noise in the non-linear channel. This paper proposes an improved DSI (Dummy Sequence Insertion) method, which can achieve the better PAPR and BER performances. The feature of proposed method is to optimize the phase of each dummy sub-carrier so as to reduce the PAPR performance by changing all predetermined phase coefficients in the time domain signal, which is calculated for data sub-carriers and dummy sub-carriers separately. To achieve the better PAPR performance, this paper also proposes to employ the time-frequency domain swapping algorithm for fine adjustment of phase coefficient of the dummy subcarriers, which can achieve the less complexity of processing and achieves the better PAPR and BER performances than those for the conventional DSI method. This paper presents various computer simulation results to verify the effectiveness of proposed method as comparing with the conventional methods in the non-linear channel.

Iterative based time domain equalization method for OFDM signal under high mobile environments

A loss of subcarrier orthogonality in orthogonal frequency division multiplexing (OFDM) signal due to time-varying multipath fading channel causes an inter-carrier interference (ICI) which would lead fatal degradation of bit error rate (BER) performance. To solve this problem, this paper proposes a high accuracy time domain channel impulse response (CIR) estimation method and a time domain equalization (TDE) method of using estimated CIR at every sampling time in conjunction with a low-complexity iterative method instead of using an inverse matrix calculation. The salient feature of proposed method is to employ a time-domain training sequence (TS) for the estimation of CIR at every sampling time and low-complexity iterative method for solving the simultaneous equations which are required in the TDE method. This paper presents various simulation results to demonstrate the effectiveness of proposed TDE method as comparing with the conventional frequency domain equalization (FDE) method.

Interleaved partitioning PTS with new phase factors for PAPR reduction in OFDM systems

Interleaved partitioning partial transmit sequence (PTS) has lower computational complexity when compared with adjacent partitioning PTS and pseudo random partitioning PTS. However, the PAPR performance of interleaved partitioning PTS is worse than other methods. This paper proposes a new phase factors for Partial Transmit Sequence (PTS) method with interleaved partitioning scheme, which can improve the PAPR performance as compared with the conventional PTS method, without any increasing of side information and the computational complexity.

Iterative Based ML Demodulation Method for OFDM Signal under Higher Mobile Environments

Orthogonal Frequency Division Multiplexing (OFDM) signal would be damaged significantly by inter- carrier interference (ICI) in higher time-varying fading channels which leads fatal degradation of bit error rate (BER) performance due to the loss of orthogonality among subcarriers. To solve this problem, this paper proposes an iterative based maximum likelihood demodulation (MLD) method which can achieve better BER performance with lower computation complexity even in higher time-varying fading channels. The features of proposed method are to employ a time domain training sequence (TS) in the estimation of channel impulse response (CIR) instead of using pilot subcarriers in the frequency domain and to employ a time domain equalization (TDE) method with a maximum likelihood (ML) estimation instead of using a conventional frequency domain equalization (FDE) method. This paper also proposes a low-complexity iterative method for solving the simultaneous equations in the MLD method instead of using an inverse matrix calculation. This paper presents various simulation results in higher time-varying fading channels to demonstrate the effectiveness of proposed method as comparing with the conventional frequency domain equalization method.

Proposal of Simple PAPR Reduction Method for OFDM Signal by Using Dummy Sub-Carriers

One of the disadvantages of using OFDM is the larger peak to averaged power ratio (PAPR) in its time domain signal. The larger PAPR signal would course the fatal degradation of bit error rate performance (BER) due to the inter-modulation noise in the non-linear channel. This paper proposes an improved DSI (Dummy Sequence Insertion) method, which can achieve the better PAPR and BER performances. The feature of proposed method is to optimize the phase of each dummy sub-carrier so as to reduce the PAPR performance by changing all predetermined phase coefficients in the time domain signal, which is calculated for data sub-carriers and dummy sub-carriers separately. To achieve the better PAPR performance, this paper also proposes to employ the time-frequency domain swapping algorithm for fine adjustment of phase coefficient of the dummy subcarriers, which can achieve the less complexity of processing and achieves the better PAPR and BER performances than those for the conventional DSI method. This paper presents various computer simulation results to verify the effectiveness of proposed method as comparing with the conventional methods in the non-linear channel.

Proposal of Time Domain Channel Estimation Method for MIMO-OFDM Systems

This paper proposes a time domain channel estimation (TD-CE) method for Multi Input Multi Output-Orthogonal Frequency Division Multiplexing (MIMO-OFDM) systems. The feature of proposed TD-CE method is to estimate channel frequency responses for all links between transmit and receive antennas in MIMO-OFDM systems by using one scattered pilot preamble symbol in the time domain. The proposed method can achieve higher channel estimation accuracy even when the number of transmission antennas is larger and the transmission signal is sampled by a non-Nyquist rate in which the number of IFFT points is different from the number of data subcarriers due to the insertion of null subcarriers (zero padding) at the both ends of data subcarriers. This paper shows various computer simulation results in the time-varying fading channels to demonstrate the effectiveness of the proposed channel estimation method as comparing with the conventional channel estimation methods.