Browsing by Author "Chien, Feng-Tsun"

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35 An Effective Routing Protocol with Guaranteed Route Preference for Mobile Ad Hoc Networks
(2014)
Chien, Feng-Tsun
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Wu, Kuo-Guan
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Chan, Yu-Wei
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Chang, Min-Kuan
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Su, Yi-Sheng
Battery power and queue conservation are critical issues in mobile ad hoc network (MANET). These two factors not only affect the delivery ratio but also the lifetime of the network. In this work, we will propose a simple and effective routing protocol to extend the lifetime and to evenly distribute the traffic loads of the networks as possible. Furthermore, a concept of serving capacity is introduced to reflect the level of congestion around a node. In this way, the proposed routing protocols can avoid network congestion and achieve higher packet delivery ratios. The extensive computer simulation is conducted to compare the proposed protocol against many existing routing protocols. The results show that the proposed routing protocol can have better performance in terms of queueing length, lifetime, and packet delivery ratio and have comparable end-to-end delays.
A Coalitional Graph Game Approach for Minimum Transmission Broadcast in IoT Networks
(2020-01-01)
Chan, Yu-Wei
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Chien, Feng-Tsun
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Chang, Min-Kuan
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Ho, Wei-Chun
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Hung, Jason C.
In this work, we consider the broadcast mechanisms for both reliable links and unreliable links in the Internet of Things (IoT) networks. Focusing on the minimum transmission broadcast (MTB) problem, we propose an efficient algorithm, termed as the Connected Dominating Set Algorithm based on Coalitional Graph Game (CDSA-CGG), to find the minimum connected dominating set (MCDS). Distinct from related work in the literature which adopts a non-cooperative game approach and assumes the interaction among nodes is limited to neighboring nodes, we formulate the interaction and cooperation among nodes over reliable links and over unreliable links as a connected forwarding graph based on coalitional graph game. We prove that the forwarding graph constructed by CDSA-CGG is a Nash network. In addition, we also prove that the final resulting graph is pairwise stable. The simulation results show that the proposed coalition graph game-based algorithm performs well in terms of the number of transmissions, convergence rate, and lifetime of nodes.
A Content-Adaptive Image Enlargement Scheme Based on Iterative Back-Projection
(2014-01-01)
Chang, Min-Kuan
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Su, Ming-Cheng
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Lin, Guo-Shiang
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Chien, Feng-Tsun
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電子工程學系及電子研究所
In this paper, we propose an adaptive image enlargement scheme based on iterative back-projection. Initial estimates of each enlarged image can be individually created from the spatial and temporal domains by using sub-pixel interpolation and sub-pixel motion estimation. Then, based on the initial estimates and image content, reconstructed images are derived by using a modified iterative back-projection technique and fused into an enlarged image. Finally, a low-pass filter as a post-processing is applied to reduce the blocking artifacts in the reconstructed high-resolution images. Our experiment results demonstrate that, in terms of PSNR and NQM, the proposed scheme is superior to existing methods.
Adaptive Modulation in Decode-and-Forward Cooperative Communications With Limited Source-Relay CSI
(2014-12-01)
Chang, Min-Kuan
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Chien, Feng-Tsun
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
In this letter, we study the problem of adaptive modulation (AM) in cooperative decode-and-forward (DF) relaying systems with limited channel state information (CSI) of the source-relay link. We first develop the signal-to-noise ratio (SNR)-based opportunistic AM and obtain the regions of the source-destination and relay-destination link SNR, by which whether cooperative relaying is needed and what constellation size should be chosen can be determined without requiring the source-relay link CSI. We also propose the probabilistic AM to further enhance the transmission rate. Simulation results demonstrate the effectiveness of the proposed AM criteria.
Analysis and Visualization of Deep Neural Networks in Device-Free Wi-Fi Indoor Localization
(2019-01-01)
Liu, Shing-Jiuan
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Chang, Ronald Y.
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Chien, Feng-Tsun
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
Device-free Wi-Fi indoor localization has received significant attention as a key enabling technology for many Internet of Things (IoT) applications. Machine learning-based location estimators, such as the deep neural network (DNN), carry proven potential in achieving high-precision localization performance by automatically learning discriminative features from the noisy wireless signal measurements. However, the inner workings of the DNNs are not transparent and not adequately understood, especially in the indoor localization application. In this paper, we provide quantitative and visual explanations for the DNN learning process as well as the critical features that the DNN has learned during the process. Toward this end, we propose to use several visualization techniques, including 1) dimensionality reduction visualization, to project the high-dimensional feature space to the 2D space to facilitate visualization and interpretation, and 2) visual analytics and information visualization, to quantify relative contributions of each feature with the proposed feature manipulation procedures. The results provide insightful views and plausible explanations of the DNN in device-free Wi-Fi indoor localization using the channel state information (CSI) fingerprints.
Asymptotic Reduced-Rank MMSE in Asynchronous MC-DS-CDMA Systems
(2014-01-01)
Chien, Feng-Tsun
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Chang, Ronald Y.
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
We consider the design of a reduced-rank minimum mean-squared error (MMSE) receiver for asynchronous multicarrier-direct sequence-code division multiple access (MC-DS-CDMA) systems with random spreading. We focus on the asymptotic MMSE filter designs in the large system regime, i.e., both the spreading gain and the number of users approach infinity while their ratio is a finite constant and the number of subcarriers is finite. Explicit expressions for the asymptotic weights of the MMSE receiver are derived for the case where the spreading sequences are identical over different subcarriers for each user. Simulation results validate our analysis.
Bandwidth-Constrained Multistage Bayesian Game for Spectrum Trading in Cognitive Radio Networks
(2009)
Lee, Chong-You
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Chien, Feng-Tsun
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
In this paper, we study the problem of spectrum trading in cognitive radio (CR) networks from a game theoretical perspective. Particularly, we consider the CR network with multiple primary services (PS's) and a single secondary service (SS), where all PS's are sellers competing in the prices and the SS is the buyer deciding how much spectrum is demanded from each PS in the trading game. Aiming at dealing with the trading behaviors, we propose using a multistage Bayesian game based trading model to account for possible unknown private information in each player, and obtain the perfect Bayesian equilibrium (PBE) sequentially under a bandwidth constraint. By the backward induction principle, we translate the Karush-Kuhn- Tucker (KKT) condition of the SS to form a joint KKT conditions with PS in order to solve the optimization problem. Finally, in the simulations, we compare the proposed approach with that in [1], and numerically study the convergence behaviors of the proposed multistage game.
Blind recursive tracking of carrier frequency offset (CFO) vector in MC-CDMA systems
(2007-04-01)
Chien, Feng-Tsun
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Kuo, C.-C. Jay
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
A recursive algorithm for estimating and updating the effective carrier frequency offset (CFO) vector in a multicarrier code-division multiple-access (MC-CDMA) system is proposed in this work.. The recursive relation is derived based on the expectation maximization (EM) algorithm with a quadratic constraint. This new approach enables the use of linear estimation theory to tackle the CFO estimation problem with or without training data, which leads to an analytic CFO estimate in closed form. Furthermore, the multiple access interference (MAI) is mitigated using the second order statistics of the interference-plus-noise vector, which is updated in a recursive manner under the EM formulation, too. When reaching a converged estimate, a fixed-norm quadratic constraint is imposed so that the final CFO estimate is robust to an imprecise covariance matrix estimate caused by insufficient data samples. It is demonstrated by computer simulation that the performance of an MC-CDMA system without the CFO information can be restored by the proposed scheme in the sense that its bit error probability (BEP) performance is close to that with perfect CFO knowledge.
Coalitional Game Formulation for Multi-Channel Cooperative Cognitive Radio Networks
(2011)
Chan, Yu-Wei
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Chang, Ronald Y.
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Chien, Feng-Tsun
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Chang, Min-Kuan
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Chung, Yeh-Ching
In this paper, we study a coalitional game approach to resource allocation in a multi-channel cooperative cognitive radio network with multiple primary users (PUs) and secondary users (SUs). We propose to form the grand coalition by grouping all PUs and SUs in a set, where each PU can lease its spectrum to all SUs in a time-division manner while the SUs in return help the data transmission of PUs by relaying. The grand coalition is shown to be stable in the considered scenario by justifying that the solution concept of the coalitional game (the core) is nonempty. Also, optimal relay strategies of SUs, to relay or to transmit its own data, are obtained so that the sum rate of all PUs and SUs is maximized. Finally, we demonstrate in simulation the benefits of the grand coalition comparing to the case of direct transmission only and other forms of coalitions as well.
Coalitional Power Control and Time Allocation for Multiuser Cognitive Networks
(2013-09-01)
Chan, Yu-Wei
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Chien, Feng-Tsun
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Park, James J.
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Hung, Jason C.
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Yen, Neil Y.
This paper considers the problem of resource allocation for a cooperative cognitive radio network with multiple primary users (PUs) and multiple secondary users (SUs), in which secondary users (SUs) relay traffics for primary users, in exchange for dedicated transmission time for their own transmission needs. However, since the PUs and SUs are rational, they aim at maximizing their own utility. Therefore, the problem of conflicting interests between them exists. We formulate the problem as a coalitional game to analyze the cooperation behavior between PUs and SUs. We propose to form the grand coalition by grouping all PUs and SUs in a set, and to use the core and the Shapley value solution concepts, respectively to analyze the stability and fairness of cooperative resource allocation. The optimal fraction of time allocation and power allocation for PUs and SUs are derived by an iterative updating algorithm, respectively. Simulation results show the benefits of our proposed approach as compared with other approaches.
Cooperative Online Caching in Small Cell Networks with Limited Cache Size and Unknown Content Popularity
(2018-01-01)
Yen, Chen-Tai
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Chien, Feng-Tsun
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Chang, Min-Kuan
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
In this paper, we study delay-aware cooperative online content caching with limited caching space and unknown content popularity in dense small cell wireless networks. We propose a Cooperative Online Content cAching algorithm (COCA) that decides in which BS the requested content should be cached with considerations of three important factors: the residual cache space in each small cell basestation (SBS), the number of coordinated connections each SBS establishes with other SBSs, and the number of served users in the coverage area of each SBS. In addition, due to limited storage space in the cache, the proposed COCA algorithm eliminates the least recently used (LRU) contents to free up the space. We compare the delay performance of the proposed COCA algorithm with the existing offline cooperative caching schemes through simulations. Simulation results demonstrate that the proposed COCA algorithm has a better delay performance than the existing offline algorithms.
Cross-layer QoS analysis of opportunistic OFDM-TDMA and OFDMA networks
(2007-05-01)
Chang, Yu-Jung
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Chien, Feng-Tsun
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Kuo, C. -C. Jay
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
Performance analysis of multiuser orthogonal frequency division multiplexing (OFDM-TDMA) and orthogonal frequency division multiple access (OFDMA) networks in support of multimedia transmission is conducted in this work. We take a cross-layer approach and analyze several quality-of-service (QoS) measures that include the bit rate and the bit error rate (BER) in the physical layer, and packet average throughput/delay and packet maximum delay in the link layer. We adopt a cross-layer QoS framework similar to that in IEEE 802.16, where service classification, flow control and opportunistic scheduling with different subcarrier/bit allocation schemes are implemented. In the analysis, the Rayleigh fading channel in the link layer is modeled by a finite-state Markov chain, and the channel state information (CSI) is assumed to be available at the base station. With the M/G/1 queueing model and flow control results, our analysis provides important insights into the performance difference of these two multiaccess systems. The derived analytical results are verified by extensive computer simulation. It is demonstrated by analysis and simulation that OFDMA outperforms OFDM-TDMA in QoS metrics of interest. Thus, OFDMA has higher potential than OFDM-TDMA in supporting multimedia services.
Delay Analysis and Comparison of OFDM-TDMA and OFDMA under IEEE 802.16 QoS Framework
(2006)
Chang, Yu-Jung
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Chien, Feng-Tsun
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Kuo, C. -C. Jay
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
The delay analysis and comparison of OFDM-TDMA and OFDMA using a flow control scheme under the QoS framework of IEEE 802.16 are conducted in this work. We investigate the maximum packet delay performance by deriving delay bounds for several multiaccess modes with different subcarrier/time-slot assignment and bit allocation schemes. The analytical delay bounds provide insights into the performance difference among different multiaccess schemes, and demonstrate each scheme\'s capability of supporting real-time, delay-sensitive multimedia applications. The derived analytical results are verified by computer simulation.
Design and Performance Analysis of Multirate Multicarrier Systems for Dynamic Spectrum Access
(2015-07-01)
Mukherjee, Mithun
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Chang, Ronald Y.
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Chien, Feng-Tsun
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
In this letter, we analytically study the bit-error-rate (BER) performance of the multirate multicarrier system with a multistage interference cancellation receiver for dynamic spectrum access (DSA) in correlated Rayleigh fading channels. We consider a scheme that incorporates a novel combination of non-contiguous carrier interferometry (NC-CI) codes and NC-binary codes to maintain orthogonality in NC subcarrier allocation for DSA. Simulation corroborates the analysis and demonstrates the superior performance of the proposed system over conventional scheme due to the nice properties of the proposed code design.
Design of reduced-rank MMSE combiner in asynchronous MC-DS-CDMA
(2008)
Hwang, Chien-Hwa
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Chien, Feng-Tsun
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
In this paper, we consider the design of a reduced-rank minimum mean-squared error (MMSE) combiner in an asynchronous multicarrier-direct sequence-code division multiple access (MC-DS-CDMA) system. It is shown that the combiner weights are related to quantities whose expressions resembles the eigenvalue moments of the interference autocorrelation matrix. To lift the burden of recomputing the weights from time to time, the weights are evaluated in a large system regime and averaged over random parameters including asynchronous delays, correlated fading coefficients and spreading sequences. Explicit expressions for the asymptotic weights of the MMSE combiner are derived. The large system setting is with the spreading gain N and user number K approaching infinity, but K/N = beta and the number of sub-carriers both finite.
Distributed channel assignment for network MIMO: game-theoretic formulation and stochastic learning
(2015-05-01)
Tseng, Li-Chuan
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Chien, Feng-Tsun
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Chang, Ronald Y.
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Chung, Wei-Ho
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Huang, ChingYao
The cooperative frequency reuse among base stations (BSs) can improve the system spectral efficiency by reducing the intercell interference through channel assignment and precoding. This paper presents a game-theoretic study of channel assignment for realizing network multiple-input multiple-output (MIMO) operation under time-varying wireless channel. We propose a new joint precoding scheme that carries enhanced interference mitigation and capacity improvement abilities for network MIMO systems. We formulate the channel assignment problem from a game-theoretic perspective with BSs as the players, and show that our game is an exact potential game given the proposed utility function. A distributed, stochastic learning-based algorithm is proposed where each BS progressively moves toward the Nash equilibrium (NE) strategy based on its own action-reward history only. The convergence properties of the proposed learning algorithm toward an NE point are theoretically and numerically verified for different network topologies. The proposed learning algorithm also demonstrates an improved capacity and fairness performance as compared to other schemes through extensive link-level simulations.
Distributed Channel Selection in Multilink MISO Networks: Stochastic Learning under Time-Varying Channel States
(2014)
Tseng, Li-Chuan
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Chien, Feng-Tsun
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Chang, Ronald Y.
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
In this paper, we study the channel selection problem for selfish and altruistic precoding in multilink multiple-input single-output (MISO) networks from a distributed game-theoretic perspective. Our goal is to find for each link a proper channel selection strategy that is robust against time-varying channel states. This motivates the development of stochastic learning that finds Nash equilibrium (NE) of an expected game. The convergence properties of the proposed learning algorithm are theoretically and numerically verified. The proposed algorithm demonstrates good sum-rate performance in the system-level simulation of a multilink MISO network based on the 3GPP-LTE model.
Distributed Spectrum Trading in Multiple-Seller Cognitive Radio Networks
(2014)
Tseng, Li-Chuan
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Chien, Feng-Tsun
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Chang, Ronald Y.
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Chung, Wei-Ho
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電子工程學系及電子研究所
This paper studies spectrum trading in cognitive radio networks in which multiple service providers (SPs) sell unused spectrum to multiple unlicensed secondary users (SUs). Motivated by the nature of the problem with new considerations, spectrum trading is modeled as a multi-leader multi-follower expected Stackelberg game with two levels of competition. The SPs as leaders compete in offering subscription prices (upper-level subgame) and the SUs as followers compete in selecting service from the SPs (lower-level subgame). The lower-level subgame incorporates the time-varying spectrum availability as the external state so that the proposed scheme does not require knowledge of dynamic spectrum availability. To achieve self-organized network operation, we propose decentralized, stochastic learning-based algorithms for the game. The convergence properties of the proposed algorithms toward the Nash equilibrium (NE) are theoretically and numerically studied. The proposed scheme demonstrates good utility performance for the SUs as compared to other service selection schemes.
Energy-Assisted Decode-and-Forward for Energy Harvesting Cooperative Cognitive Networks
(2017-09-01)
Verma, Dileep K.
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Chang, Ronald Y.
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Chien, Feng-Tsun
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
In this paper, we consider a simultaneous wireless information and power transfer (SWIPT)-enabled cooperative cognitive network that addresses energy scarcity and spectral scarcity, two important issues in 5G wireless communications. In the considered network, the self-sustainable, SWIPT-enabled relay assists primary user's transmission, while the relay itself is also a secondary user with its own information superimposed on the regenerated primary information for transmission. The SWIPT relay employs the proposed energy-assisted decode-and-forward (EDF) protocol, which enhances the conventional decode-and-forward (DF) protocol with energy-dimension-augmented information decoding. We conduct a comparative analysis of the proposed EDF and the conventional DF and amplify-and-forward (AF) protocols in this SWIPT cooperative cognitive framework in terms of capacity, outage probability, and throughput for both primary and secondary networks. Simulation corroborates the analysis and demonstrates performance advantages of EDF over DF/AF from various perspectives.
Energy-Assisted Information Detection for Simultaneous Wireless Information and Power Transfer: Performance Analysis and Case Studies
(2016-06-01)
Chang, Chih-Hua
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Chang, Ronald Y.
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Chien, Feng-Tsun
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
In simultaneous wireless information and power transfer (SWIPT), practical receiver architectures consisting of an information receiver and an energy harvester have been proposed in place of an ideal receiver capable of performing two tasks simultaneously using the same circuits. In this paper, we present a novel receiver architecture design incorporating an interplay between the information receiver and the energy harvester to enhance the performance of the practical SWIPT receiver. In particular, the energy level of the received signal monitored at the energy harvester is fed back to the information receiver to assist information decoding at the information receiver. The symbol-error-rate (SER) and diversity analyses show that the proposed receiver architecture could yield a higher diversity order for unconventional constellations where any two distinct symbols have distinct energy levels, and the same diversity order for conventional modulations. Simulation of PAM and QAM modulations verifies the analysis, shows the improved SER performance of the proposed receiver architecture, and illustrates the energy-dimension-augmented decision regions. Some insights into designing enhanced practical SWIPT receivers are provided as a result.