Chia-Hsin Cheng

A modified genetic algorithm PTS technique for PAPR reduction in OFDM systems

In this paper, we propose a peak-to-average power ratio (PAPR) reduction method for an orthogonal frequency division multiplexing (OFDM) system by combining the improved genetic algorithm used the partheno-crossover operator (PCGA) with partial transmit sequence (PTS) scheme, called PCGA-PTS. Recently, the genetic algorithm based PTS scheme (GA-PTS) is a novel PAPR reduction method, which has lower computational load than the PTS technique and is a suboptimal PAPR reduction method. However, how to further improve the PAPR performance of GA-PTS in OFDM systems is still an active research. Therefore, this paper proposes a new PAPR reduction method to improve the PAPR performance of GA-PTS, based on the same computational complexity. Our proposed method uses a two-step crossover operator and a mutation operator to generate the offspring, and then selects the proper candidates from the offspring to be the individuals of new population, where the two-step crossover operator is composed of a crossover operator and a partheno-crossover operator. In simulation results, our proposed method has better PAPR performance than the GA-PTS technique in OFDM systems.

A security gateway application for End-to-End M2M communications

M2M (Machine-to-Machine) communication for the Internet of Things (IoTs) system is considered to be one of the major issues in future networks. Considering the characteristics of M2M networks in IoTs systems, traditional security solutions are not able to be applied to E2E (End-to-End) M2M networks because the M2M network itself is vulnerable to various attacks. We consider security aspects for M2M communications and then propose a security gateway application (SGA) including the lightweight symmetric key cryptographic negotiation function, secure E2E M2M key exchange generation function and secure E2E M2M messages delivery function. The proposal of the SGA is newly suggested to improve the gateway application (GA) of the ITU-T M2M service layer in the IoTs reference model. We prove that it could prevent various attacks via the theoretical security analyses. Therefore, it could meet the basic security requirements of the M2M service layer. The SGA is first proposed to improve the GA of the ITU-T M2M service layer in the IoT reference model;Secure Exchange Key scheme is used among smart devices and SGA server for secure E2E M2M communication in IoTs;Lightweight symmetric key cryptographic negotiation function is first proposed;The proposal functions of the SGA in this paper are suitable to be a new standard interface because their meet the basic security requirements of the M2M service layer.

Performance of an adaptive PSO partial parallel interference canceller for CDMA communication systems

In this paper, we propose an adaptive particle swarm optimization (APSO) based partial parallel interference cancellation scheme for direct-sequence code-decision multiple access (CDMA) communication system over frequency selective fading channels. However, the partial cancellation tries to reduce the cancellation error in parallel interference cancellation schemes due to the wrong interference estimations in the early stages. Thus, in order to reduce the computational complexity and improve the performacne of the CDMA system, particle swarm optimization (PSO), which has the ability of solution to complex combinatorial optimization problem, is employed in searching the optimal weight for multiple access interference cancellation. Experiments have been carried out on the method can improved on the multiuser detection in CDMA system, the simulation results show that APSO detector can achieve the global optimization in fast convergence rate, and also show that the proposed detector is obviously superior to convenentional receiver and multiuser detectors based on some optimum algorithm in terms of the multiple access interfere and the mitigation of near-far effect.

Using Back Propagation Neural Network for Channel Estimation and Compensation in OFDM Systems

In orthogonal frequency division multiplexing (OFDM) communication systems, due to the environmental impact generated the multipath effect caucused signals distortion and attenuation in transmitted process, and due to relative motion between transmitter and receiver caused the Doppler Effect that makes the signal carrier offset. Therefore, the knowledge of the channel characteristics is very important. To remove the effect from received signal, the receiver needs to have knowledge of channel impulse response (CIR) by channel estimation, and then compensates signals. In this paper, a back propagation neural network (BPNN) is used to estimate channel and compensate signals. Our proposed BPNN channel estimation would compare bit error rate (BER) and mean square error (MSE) with least square (LS) and minimum mean square error (MMSE) algorithms in an existing OFDM channel environment. From the results, our proposed algorithm has better performance than LS algorithm and closes to MMSE algorithm.

Improving TCP performance with fast adaptive congestion control during soft vertical handoff

Recently, the research on the interworking between 3G cellular networks and WLANs is actively being constructed. To integrate these two technologies, there are many issues such as the network architecture, mobility management, and security which should be solved. During vertical handoff, some undesirable phenomena may mistakenly trigger TCP congestion control operations and thus degrade TCP performance. In this paper, we propose an approach that can quickly estimate available bandwidth when a mobile node (MN) handoff occurs. A sender updates the adaptive slow-start threshold (ssthresh) and congestion window size (cwnd) to improve TCP performance during soft vertical handoff in hybrid mobile networks. Our scheme requires only minor modifications of the transport layer of the end hosts. Simulation results show that our scheme effectively improves the TCP performance.

An effective hybrid GACSA -based multi-user detection for ultra-wideBand communications systems

In this paper, we investigate the performance of various interference cancellation techniques in direct-sequence ultra-wideband (DS-UWB) communication systems. Multiple access interference (MAI) causes the performance of the conventional single user detector in DS-UWB systems to degrade. Due to high complexity of the optimum multiuser detector, suboptimal multiuser detectors with less complexity and reasonable performance have received considerable attention. A hybrid approach that employs a genetic algorithm (GA) and chaos algorithm (CSA) for the MUD problem in UWB communication systems is proposed. By taking advantage of heuristic values and the collective intelligence of GACSA, the proposed detector offers almost the same bit error rate (BER) performance as the full-search-based optimum multiuser detector does, while greatly reducing the computational complexity. The near-far resistance of the GACSA-based multiuser detector is also examined. The good behavior of the proposed approach is demonstrated by means of comparisons in term of bit error rate (BER) performance and implementation complexity with the classical Rake receiver and different multiuser receivers previously proposed in the literature on this subject.

Neural Network-Based Estimation for OFDM Channels

In this paper, an Neural network based channel estimation algorithm is proposed in the orthogonal frequency division multiplexing (OFDM) systems. The adoption of Functional Link Neural Fuzzy Network (FLNFN) algorithm is used for channel estimation. Experimental results indicate that the performance of the proposed channel estimation can improve the system performance, compared to the traditional channel estimation such as least square (LS), minimum mean square error (MMSE) algorithms.

Energy Efficient Block Division Methods for Data Aggregation in Wireless Sensor Networks

In this paper, data collection schemes with data aggregation for static sink are proposed in wireless sensor networks. According to the distribution of source nodes in whole sensor field, we use a block partition scheme and then each block selects a sensor node as local sink for the data collection of the local area. Furthermore, the local sink would transmit the data to the global sink after aggregating to achieve the purpose of reducing energy consumption. From the simulation results, it shows that our proposed methods are more efficient in the energy consumption and the data delivery ratio.

Invasive weed optimization method based blind multiuser detection for MC-CDMA interference suppression over multipath fading channel

The paper presents a novel constrained constant modulus (CMA) approach for the blind suppression of multiuser interference in multi-carrier code division multiple access (MC-CDMA) systems. In this paper, we put forward a novel receiver, which combines CMA blind adaptive multiuser detection with Invasive weed optimization (IWO) for MC-CDMA interference suppression over multipath fading channel. To work around potentially computational intractability, the proposed scheme exploits heuristics in consideration of both global and local exploration the step size of the CMA. The computer simulation results show that compared with the various CMA developed previously, the proposed IWO method obtains the most desirable bit error rate performance with low computational complexity.

Energy-Efficient Sink Location Service Protocol to Support Mobile Sinks in Wireless Sensor Networks

In this paper, we present mobile sinks with energy-efficient sink location service protocol for wireless sensor networks. The data is collected by mobile sinks in sensor networks. To make source built an efficiently forward data from a source node to a sink with minimal delay path, sink and source broadcast the information of their locations each other in different direction. We also propose a reduced data path detour situations in sink mobility and data forwarding maintenance. Therefore, the overall energy consumption and data transmission time can be reduced effectively. We compare our proposed protocol with Jeon’s Sink-oriented Dynamic Location Service (SDLS) protocol. From simulation results, it shows that the proposed protocol has less energy consumption and longer network lifetime than Jeon’s.