Browsing by Author "Chu, Jui-Hung"

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Analysis and determination of cooperative MAC strategies from throughput perspectives
(2013-08-01)
Chu, Jui-Hung
;
Feng, Kai-Ten
;
Liao, Chun-Chieh
;
電機資訊學士班
;
Undergraduate Honors Program of Electrical Engineering and Computer Science
In recent years, cooperative communication has been developed as a new communication strategy that incorporates a relay node to assist direct point-to-point transmission. By exploiting cooperative diversity, different types of techniques have been proposed to improve transmission reliability from the physical layer perspective. However, owing to the longer transmission time resulting from the cooperative schemes, there is no guarantee to enhance network throughput in view of the medium access control (MAC) performance. In this paper, system throughput of combined direct/cooperative communication is evaluated by exploiting the proposed analytical model based on the IEEE 802.11 MAC protocol. The feasibility of adopting either cooperative or direct communication is also studied in the analytical model. In terms of network throughput, whether to adopt cooperative schemes depends on the tradeoff between cooperative transmission delay and channel quality of direct communication. Moreover, two cooperative MAC protocols are proposed to determine the circumstances to activate cooperative communication according to the channel quality. The full-channel quality indicator based cooperative (FCC) MAC protocol is introduced to choose both the transmission scheme and the relay node according to the full channel quality information. However, the overhead caused by the FCC scheme can degrade the throughput performance as the number of available relays is significantly increased. Therefore, the bitwise competition based cooperative (BCC) MAC protocol is utilized to efficiently determine a feasible relay node for data transmission. Simulations are performed to validate the effectiveness of proposed analytical models and cooperative MAC protocols. It is observed that the proposed BCC scheme can outperform both the FCC protocol and conventional direct transmission with enhanced system throughput.
Cognitive Radio Enabled Multi-channel Access for Vehicular Communications
(2010)
Chu, Jui-Hung
;
Feng, Kai-Ten
;
Chuah, Chen-Nee
;
Liu, Chin-Fu
;
電機工程學系
The IEEE 1609.4 standard has been proposed to provide multi-channel operations in wireless access for vehicular environments (WAVE), where all the channels are periodically synchronized into control and service intervals. The communication device in each vehicle will stay at the control channel for negotiation and contention during the control interval, and thereafter switch to one of the service channels for data transmission in the service interval. The inefficiency of WAVE system comes from the fact that half of the time intervals of the service channels remain idle since all the stations are performing message contention within the control channel. In this paper, the cognitive radio-enabled multi-channel access (CREM) protocol is proposed to increase the channel utilization of IEEE 1609.4 standard. Based on the concept of cognitive radio, the vehicular stations are categorized into primary stations with safety-related messages and secondary stations with non-safety information to be delivered. Prioritized channel access is designed in the proposed CREM scheme in order to increase the transmission opportunity of primary stations. Moreover, extended time intervals are granted for primary stations to ensure reliability for data transmission. The enhanced CREM (CREM-E) protocol is proposed to further opportunistically increase the channel utilization of secondary stations. Simulation results show that the proposed CREM-E scheme outperforms the existing IEEE 1609.4 protocol with enhanced channel utilization and smaller waiting time intervals.
Cognitive Radio-Enabled Optimal Channel-Hopping Sequence for Multi-Channel Vehicular Communications
(2011)
Chu, Jui-Hung
;
Feng, Kai-Ten
;
Lin, Jia-Shi
;
Hsu, Chung-Hsien
;
電機工程學系
The IEEE 1609.4 standard has been proposed to provide multi-channel operations in wireless access for vehicular environments (WAVE), where all the channels are periodically synchronized into control and service intervals. In this paper, based on the concept of cognitive radio, the vehicles are categorized into primary providers (PPs) that intend to transmit safety-related messages and secondary providers (SPs) with non-safety information to be delivered. The cognitive radio-enabled optimal channel-hopping sequence (CROCS) approach is proposed to improve the channel utilization of IEEE 1609.4 standard for multi-channel vehicular networks. Prioritized channel access is analyzed in the CROCS scheme in order to increase the transmission opportunity of the PPs. Moreover, optimal channel-hopping sequence is assigned for the SPs based on the dynamic programming technique. It is designed to consider the optimal load balance between both the channel availability and channel utilization within the throughput constraints of PPs. With the adoption of proposed CROCS approach, simulation results show that maximum throughput of SPs can be achieved with guaranteed quality-of-service requirement for the PPs.
Energy-Efficient Cell Selection and Resource Allocation in LTE-A Heterogeneous Networks
(2014)
Chu, Jui-Hung
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Feng, Kai-Ten
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Chang, Tain-Sao
;
電機工程學系
;
Department of Electrical and Computer Engineering
In 3GPP Release-12 specification, the adoption of small cells in long term evolution (LTE) networks is considered as a promising solution to meet the growing traffic demand for mobile data usage. However, energy consumption becomes a crucial challenge for network operators to deploy more small cells in heterogeneous networks in order to fulfill the requirement for achieving high data rates. In this paper, an advanced signaling mechanism has been proposed to practically acquire global channel state information (CSI) between network components. Based on the signaling scheme, an energy-efficient cell selection and resource allocation (ECR) algorithm is proposed to increase system energy efficiency by handovering UEs from light-loaded base station to nearby cells. Some active cells can therefore be switched off to reduce total energy consumption. Simulation results show that better energy efficiency can be achieved by adopting the proposed signaling and ECR schemes.
Energy-Efficient Spectrum Selection and Resource Allocation in Downlink Cognitive Femtocell Networks
(2015)
Chen, Jun-Quan
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Chu, Jui-Hung
;
Feng, Kai-Ten
;
電機學院
;
College of Electrical and Computer Engineering
The adoption of femtocell networks is considered as a promising solution to resolve the poor received signal strength problem experienced by the user equipment (UE) located in the coverage hole or in indoor environment. The architecture of femtocell networks, which adopt cognitive radio (CR), centralized controlled by femtocell gateway (F-GW) is further proposed to enhance the system performance by accessing more licensed spectrums. However, more deployed femtocells lead to additional energy consumption and it has become a crucial challenge for mobile operators. In this paper, the spectrum selection with limited number of antennas (SSLNA) is proposed to derive the target spectrum with consideration of hardware limitation of both femtocell access points (FAPs) and UEs. Based on the spectrum selection policies, the energy-efficient joint resource block (RB) and power allocation (EJRPA) scheme is proposed to improve the system energy efficiency. To avoid large amount of communicational load and complex computation for both F-GW and FAPs, the energy efficiency optimization problem is transformed into a two-layer problem solved respectively by F-GW and FAPs when the EJRPA is adopted. Simulation results show that better system energy efficiency can be achieved by adopting the proposed schemes.
Joint Clusterization and Power Allocation for Cloud Radio Access Networks
(2015)
Tsou, Yao-Chun
;
Li, Pei-Rong
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Chu, Jui-Hung
;
Feng, Kai-Ten
;
電機學院
In this paper, the cloud radio access network (CRAN) is considered to extend the transmission coverage via the distributed deployment of large-scale remote radio units (RRUs). However, this type of structure can induce considerable computational loadings due to the centralized management mechanisms. To reduce the complexity incurred in the C-RAN architecture, the clusterization technique is designed to categorize those RRUs into several groups. For the purpose of enhancing energy efficiency (EE) as well as the consideration of computational complexity, the joint clusterization and power allocation schemes are proposed to obtain the better tradeoff under the quality-of-service (QoS) requirement for each user equipment (UE). Simulation results show that the proposed algorithms can provide better performance gain than the existing method.
Novel Design of Optimal Spectrum Sharing for Cognitive Radio-Enabled LTE-A Multi-Cell Networks
(2016-10-01)
Feng, Kai-Ten
;
Li, Pei-Rong
;
Chu, Jui-Hung
;
電機學院
;
College of Electrical and Computer Engineering
For long term evolution-advanced (LTE-A) system, carrier aggregation (CA) allows LTE evolved Node B (eNB) and user equipment (UE) to access idle frequency spectrum to serve continuously growing traffic demands. To efficiently enhance network throughput, the concept of cognitive radio (CR) is adopted for LTE-A system to dynamically access opportunistic spectrum not occupied by primary system. Under the consideration of limited feedback system, the partially observable Markov decision process (POMDP) is applied in this paper to estimate the channel occupancy information (COI) on shared spectrum by partially sensing the frequency carriers. A POMDP-based spectrum sharing (POSS) scheme is then proposed to realize throughput maximization via the designs of contention mechanism and resource allocation policy according to the partially observable COI, channel state information, and number of contending cells in the network. Compared with the exhaustive search, the proposed approach can achieve optimal performance gain with lower computational complexity, which is proved to be a linear time algorithm. Numerical results illustrate that the proposed POSS protocol can effectively improve system throughput on shared spectrum for the LTE-A networks.
Prioritized Optimal Channel Allocation Schemes for Multi-Channel Vehicular Networks
(2015-07-01)
Chu, Jui-Hung
;
Feng, Kai-Ten
;
Lin, Jia-Shi
;
電機資訊學士班
;
Undergraduate Honors Program of Electrical Engineering and Computer Science
The IEEE 1609.4 standard has been proposed to provide multi-channel operations in wireless access for vehicular environments (WAVE), where all channels are periodically synchronized into control and service intervals. Communication device in each vehicle will stay at the control channel for negotiation and contention during the control interval, and thereafter switch to one of the service channels for data transmission in the service interval. In this paper, based on the concept of cognitive radio (CR), the vehicles are categorized into primary providers (PPs) that intend to transmit safety-related messages and secondary providers (SPs) with non-safety information to be delivered. The prioritized optimal channel allocation (POCA) approaches are proposed to improve channel utilization of IEEE 1609.4 standard for multi-channel vehicular networks. Prioritized channel access is analyzed in the POCA schemes in order to increase the transmission opportunity of PPs. Moreover, depending on whether the CR network is distributed or centralized, the optimal channel-hopping sequence and optimal channel allocation is assigned for SPs based on dynamic programming and linear programming technique, respectively. These schemes are designed to consider optimal load balance between both channel availability and channel utilization within the throughput constraints of PPs. With the adoption of proposed POCA schemes, simulation results show that maximum throughput of SPs can be achieved with guaranteed quality-of-service requirement for PPs.
Stochastic spectrum handoff protocols for partially observable cognitive radio networks
(2014-07-01)
Chu, Jui-Hung
;
Ma, Rui-Ting
;
Feng, Kai-Ten
;
電機資訊學士班
;
Undergraduate Honors Program of Electrical Engineering and Computer Science
Recent studies have been conducted to indicate the ineffective usage of licensed bands due to static spectrum allocation. In order to improve spectrum utilization, cognitive radio (CR) is therefore suggested to dynamically exploit the opportunistic primary frequency spectrums. How to provide efficient spectrum handoff has been considered a crucial issue in the CR networks. Existing spectrum handoff algorithms assume that all the channels can be correctly sensed by the CR users in order to perform appropriate spectrum handoff process. However, this assumption is impractical since excessive time will be required for the CR user to sense the entire spectrum space. In this paper, the partially observable Markov decision process (POMDP) is applied to estimate the network information by partially sensing the frequency spectrums. A POMDP-based spectrum handoff (POSH) scheme is proposed to determine the optimal target channel for spectrum handoff according to the partially observable channel state information. Moreover, a POMDP-based multi-user spectrum handoff (M-POSH) protocol is proposed to exploit the POMDP policy into multi-user CR networks by distributing CR users to frequency spectrum bins opportunistically. By adopting the policies resulted from the POSH and M-POSH algorithms for target channel selection, minimal waiting time at each occurrence of spectrum handoff can be achieved which will be feasible for multimedia applications. Numerical results illustrate that the proposed spectrum handoff protocols can effectively minimize the required waiting time for spectrum handoff in the CR networks.
Stochastic spectrum handoff protocols for partially observable cognitive radio networks
(2014-07-01)
Chu, Jui-Hung
;
Ma, Rui-Ting
;
Feng, Kai-Ten
;
電機工程學系
;
Department of Electrical and Computer Engineering
Recent studies have been conducted to indicate the ineffective usage of licensed bands due to static spectrum allocation. In order to improve spectrum utilization, cognitive radio (CR) is therefore suggested to dynamically exploit the opportunistic primary frequency spectrums. How to provide efficient spectrum handoff has been considered a crucial issue in the CR networks. Existing spectrum handoff algorithms assume that all the channels can be correctly sensed by the CR users in order to perform appropriate spectrum handoff process. However, this assumption is impractical since excessive time will be required for the CR user to sense the entire spectrum space. In this paper, the partially observable Markov decision process (POMDP) is applied to estimate the network information by partially sensing the frequency spectrums. A POMDP-based spectrum handoff (POSH) scheme is proposed to determine the optimal target channel for spectrum handoff according to the partially observable channel state information. Moreover, a POMDP-based multi-user spectrum handoff (M-POSH) protocol is proposed to exploit the POMDP policy into multi-user CR networks by distributing CR users to frequency spectrum bins opportunistically. By adopting the policies resulted from the POSH and M-POSH algorithms for target channel selection, minimal waiting time at each occurrence of spectrum handoff can be achieved which will be feasible for multimedia applications. Numerical results illustrate that the proposed spectrum handoff protocols can effectively minimize the required waiting time for spectrum handoff in the CR networks.