Browsing by Author "Hsu, Yu-Pin"

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A maximal power-conserving scheduling algorithm for broadband wireless networks
(2008)
Tseng, Hsin-Lung
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Hsu, Yu-Pin
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Hsu, Chung-Hslen
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Tseng, Po-Hslian
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Feng, Kai-Ten
The limitation on the battery lifetime has been a critical issue for the advancement of mobile computing. Different types of powersaving techniques have been proposed in various fields. In order to provide feasible energy conserving mechanism for the Mobile Subscriber Stations (MSSs), three powersaving types have been proposed for the IEEE 802.16e broadband wireless networks. However, these power saving types are primarily targeting for the cases with a single connection between the Base Station (BS) and the MSS. With the existence of multiple connections, the power efficiency obtained by adopting the conventional scheduling algorithm can be severely degraded. In this paper, a Maximal Power Conserving (MPC) scheduling algorithm is proposed to consider the aggregated effect from the multiple connections to the power efficiency. Moreover, the Quality of Service (QoS) constraints from both the downlink and the uplink traffic are employed in the design of the MPC algorithm in order to facilitate the corresponding MSS to fulfill its QoS requirements in both directions. Numerical results show that the proposed MPC scheduling algorithm outperforms the conventional 802.16e power saving mechanism, especially under the multi connection scenarios.
Cross-layer routing for congestion control in wireless sensor networks
(2008)
Hsu, Yu-Pin
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Feng, Kai-Ten
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電信工程研究所
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Institute of Communications Engineering
Techniques for improving the network congestion have been proposed in different fields. In recent year, the congestion control problems were studied to enhance the routing performance for wireless sensor networks. In this paper, an Adaptive NAV-Assisted Routing (ANAR) algorithm is proposed to improve the network congestion with a crosslayer approach. The NAV vectors obtained from the RTS/CTS packets are utilized for the determination of the channel status around a sensor node. The routing path is selected based on the congestion-free probability along the route for the transmission of data packets. Moreover, the adaptive path-switching scheme further enhances the routing performance of the proposed ANAR algorithm. The effectiveness of the ANAR protocol is illustrated via the simulations. Without consuming excessive power for each sensor node, the ANAR algorithm can achieve better performance comparing with other existing schemes, especially under the scenarios with network congestion.
Design and Analysis of Optimal Channel-Hopping Sequence for Cognitive Radio Networks
(2010)
Lee, Chi-Mao
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Lin, Jia-Shi
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Hsu, Yu-Pin
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Feng, Kai-Ten
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電機工程學系
In recent years, channel-hopping based medium access control (MAC) protocols are proposed to improve the capacity in a decentralized multi-channel cognitive radio (CR) networks without extra usage of a control channel. Each CR user has to stochastically follow a default channel-hopping sequence in order to sense a channel and to conduct its frame transmission. In this paper, based on the channel-hopping protocol, an analysis is conducted on both the probability of channel availability and the average frame delay for the primary queueing networks. The analytical model is proposed by considering the impact caused by imperfect sensing of the CR users and the imperfect synchronization between the primary and CR networks. According to the proposed model with more realistic considerations, an optimal channel-hopping sequence (OCS) approach is designed for the CR users based on dynamic programming technique. It is designed by exploiting the optimal load balance between both the channel availability and channel utilization within the delay constraints of primary users (PUs). By adopting the OCS approach, the maximum aggregate throughput of CR users and the quality of service (QoS) requirement of PUs can both be achieved. Numerical results illustrate that the proposed OCS scheme can effectively maximize the aggregate throughput compared to conventional channel-hopping sequences, and as well guarantee the QoS requirement of the PUs.
Dynamic Power Management in Cognitive Radio Networks based on Constrained Stochastic Games
(2009)
Wang, Chia-Wei
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Hsu, Yu-Pin
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Feng, Kai-Ten
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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
Recent studies have been conducted to indicate the ineffective usage of licensed bands due to the static spectrum allocation. In order to improve the spectrum utilization, the cognitive radio is therefore suggested to dynamically exploit the opportunistic primary frequency spectrums. The interference from the secondary users to the primary user consequently draws the attention to the spectrum and power management for the cognitive radio networks. In this paper, the constrained stochastic games are utilized to exploit the optimal policies for power management by considering the variations from both the channel gain and the primary traffic. Both the underlay and overlay waveforms are considered within the network scenarios for the proposed power management scheme. Constraints for allowable interferences will be applied in order to preserve the communication quality among the primary and the secondary users. According to the formulation of the constrained stochastic games, the existence of the constrained Nash equilibrium will be validated with rigorous proofs, which will be acquired as the optimal policies for the power management problem. Simulation results further validate the correctness of the theoretically-derived policies for dynamic power management.
MCR: MAC-assisted congestion-controlled routing for wireless multihop networks
(2012-06-01)
Hsu, Yu-Pin
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Feng, Kai-Ten
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電機工程學系
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Department of Electrical and Computer Engineering
Techniques for improving network congestion have been proposed in different fields. In recent years, the congestion control problems were studied to enhance the routing performance in wireless multihop networks (WMNs). In this paper, the network allocation vector (NAV) introduced by the contention-based medium access control (MAC) protocols is utilized for the determination of the channel status around a wireless node (WN). A MAC-assisted congestion-controlled routing (MCR) algorithm is proposed to alleviate the network congestion problem by adopting the information from the MAC layer. The routing path is selected based on the congestion-free probability along the path for transmitting the data packets. Moreover, the adaptive path-switching scheme and the aggressive hop-reduction (AHR) local repair mechanism further enhance the routing performance of the proposed MCR algorithm. The effectiveness of the MCR protocol is evaluated via both the analytical study and the simulation results. Without consuming excessive control packets for each WN, the MCR algorithm can achieve better performance when compared with other existing schemes, especially under the scenarios with network congestion. Copyright (C) 2010 John Wiley & Sons, Ltd.
Performance Analysis of Cooperative Communications from MAC Layer Perspectives
(2008)
Liao, Chun-Chieh
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Hsu, Yu-Pin
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Feng, Kai-Ten
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電信工程研究所
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Institute of Communications Engineering
In recent years, cooperative communication has been proposed as a new communication paradigm that incorporates a relay node to assist the direct point-to-point transmission. By exploiting the cooperative diversity, different types of techniques have been proposed to improve the transmission reliability from the physical layer perspective, e.g. the cooperative automatic repeat request. However, owing to the longer transmission time resulting from the cooperative schemes, there is no guarantee to enhance the network throughput in view of the medium access control (MAC) performance. In this paper, the system throughput of the cooperative communication is evaluated by exploiting the proposed analytical model based on the IEEE 802.11 MAC protocol. Both the relay-based and the original direct communications are considered in the analytical studies. Simulations are conducted to further validate the effectiveness of the proposed model. In terms of the network throughput, whether to adopt the cooperative schemes depends on the tradeoff between the cooperative transmission delay and the channel condition of the direct communication.
Performance modeling of power saving classes with multiple connections for broadband wireless networks
(2008)
Hsu, Yu-Pin
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Feng, Kai-Ten
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電信工程研究所
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Institute of Communications Engineering
Different types of power saving techniques have been proposed in various fields to alleviate the limitation on the battery lifetime for the mobile stations (MSs). In order to provide feasible energy conserving mechanism, three different power saving types have been introduced in the IEEE 802.16e broadband wireless networks. By means of pre negotiations, the MS can be absent from the serving base station (BS) by performing the sleep mode operation. For each involved MS, connections with similar properties can be group into the defined power saving classes. In this paper, a comprehensive performance modeling of the IEEE 802.16e power saving classes of Type I and II are proposed. Multiple connections between the BS and the MS with both the downlink and the uplink traffic are considered in the analytical models. The power saving efficiency and the mean waiting time are utilized as the metrics for performance analysis. Simulations are performed in order to validate the results obtained from the analytical models.