Browsing by Author "Huang, Jane-Hwa"

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An Enhanced VoIP Scheduling with Silence Suppression in IEEE 802.16e/m Systems
(2010)
Wang, Li-Chun
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Yen, Eulin
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Huang, Jane-Hwa
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電機工程學系
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Department of Electrical and Computer Engineering
Thanks to silence suppression, the VoIP capacity can be improved. When the voice users are listening or thinking, the VoIP system does not need to allocate resources to them, thereby being able to accommodate more users. The main issue is how to immediately allocate resources to the user, when the user transits from the silence state to the talkspurt state. The IEEE 802.16e/m system provides two typical bandwidth request methods: unicast polling and multicast polling. The unicast-polling method can ensure the bandwidth request delay, but needs more slots for polling. Contrarily, the multicast-polling method needs fewer slots for polling, but the bandwidth request delay cannot be guaranteed. Therefore, we propose the hybrid-polling method, which combines the multicast and unicast polling. Simulation results demonstrate that by properly designing system parameters, the hybrid-polling method can achieve better tradeoff between the bandwidth request failure rate and the resources needed for polling. Moreover, the proposed hybrid-polling method can achieve comparable VoIP capacity as the multicast-polling method, with a guaranteed bandwidth request delay.
Capacity and QoS for a scalable ring-based wireless mesh network
(2006-11-01)
Huang, Jane-Hwa
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Wang, Li-Chun
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Chang, Chung-Ju
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電信工程研究所
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Institute of Communications Engineering
The wireless mesh network (WMN) is an economical solution to support ubiquitous broadband services. This paper investigates the tradeoffs among quality-of-service (QoS), capacity, and coverage in a scalable multichannel ring-based WMN. We suggest-a simple frequency planning in the proposed ring-based WMN to improve the capacity with QoS support, and to make the system more scalable in terms of coverage. We develop a physical (PHY)/ medium access control (MAC) cross-layer analytical model to evaluate the delay, jitter, and throughput of the proposed WMN, by taking account of the carrier sense multiple-access (CSMA) MAC protocol, and the impact of hop distance on transmission rate in the physical layer. Furthermore, the mixed-integer nonlinear programming optimization approach is applied to determine the optimal number of rings and the associated ring widths, aiming at maximizing the capacity and coverage of a mesh cell subject to the delay requirement.
Capacity Comparison for CSG and OSG OFDMA Femtocells
(2010)
Tsai, Ang-Hsun
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Huang, Jane-Hwa
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Wang, Li-Chun
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Hwang, Ruey-Bing
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交大名義發表
The low-power and low-cost femtocells can improve indoor coverage and capacity. However, when femtocells are deployed extensively, the serious two-tier interference problem occurs. The method to access the femtocell is the key to manage the interference in the femtocell systems. In this paper, we investigate the impacts of access methods and directional antenna on link reliability and capacity for the orthogonal frequency-division multiple access (OFDMA)-based femtocell systems. Simulation results show that the open access method can improve the femtocell capacity over the traditional closed access method. Nevertheless, under the link reliability requirement of indoor and outdoor users, the improvement in femtocell capacity due to open access method is minor. Thanks to the narrow-beam pattern, the switched-beam directional antenna can be used to further reduce the interference and enhance the capacity. It is shown that the open access method using the switched-beam antenna can achieve higher femtocell capacity than that using the omnidirectional antenna.
Coverage Enhancement for a Multi-channel Ring-based Wireless Mesh Network with Guaranteed Throughput and Delay
(2006)
Huang, Jane-Hwa
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Wang, Li-Chun
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Chang, Chung-Ju
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電信工程研究所
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Institute of Communications Engineering
Wireless mesh network (WMN) is a viable solution to support ubiquitous broadband services with low transmission power. This paper investigates the tradeoffs among delay, throughput, and coverage in a multi-channel ring-based wireless mesh network. In the proposed WMN, a simple ring-based frequency planning is employed to effectively utilize available channels. To evaluate the delay and throughput in the proposed WMN, we develop a physical (PHY)/medium access control (MAC) cross-layer analytical framework, which incorporates the carrier sense multiple access (CSMA) MAC protocol and a physical-layer distance-based rate adaptation with multi-hop connections. On top of the analytical model, the mixed-integer nonlinear programming (MINLP) optimization approach is applied to analytically determine the optimal number of rings and the associated ring widths, aiming at maximizing the coverage of a mesh cell subject to the requirements of throughput and delay.
Cross-Layer Analysis of Joint Rate and Power Adaptation in Nakagami Fading Channels with Multiple-User Contention
(2009-11-01)
Wang, Li-Chun
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Huang, Jane-Hwa
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Chen, Anderson
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Chang, Chung-Ju
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電信工程研究所
Adaptively adjusting transmit rate and power concurrently to enhance goodput and save energy is a challenging issue in a wireless local area network (WLAN) because goodput enhancement and energy saving are usually two contradictory goals. In this paper, we propose channel-driven rate and power adaptation (CDRPA) schemes and develop a physical (PHY)/medium access control (MAC) cross-layer analytical method incorporating the impacts of Nakagami fading channel and the carrier sense multiple access (CSMA) MAC protocol. The CDRPA scheme has much lower computation complexity than the energy-optimal complete-search scheme. In a multiuser contention scenario, we analyze the energy efficiency and the goodput of the power-first and rate-first CDRPA schemes as well as the energy-optimal complete-search adaptation scheme. At the cost of lower goodput, the power-first scheme has better energy efficiency than the rate-first CDRPA scheme, whereas if the goodput is the main concern, the rate-first CDRPA scheme shall be chosen due to better goodput performance. More interestingly, we find that the power-first CDRPA scheme can achieve about the same goodput and energy efficiency as the energy-optimal complete-search link adaptation scheme.
Design of optimal relay location in two-hop cellular systems
(2010-11-01)
Huang, Jane-Hwa
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Wang, Li-Chun
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Chang, Chung-Ju
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Su, Wen-Shan
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電信工程研究所
Relay stations are usually used to enhance the signal strength for the users near cell boundary, thereby extending the cell coverage. However, transmission through a relay station needs two transmission phases. The first phase is from base station to relay station, and the second one is from relay station to mobile station. Thus, using relay station may decrease system capacity due to two-phase transmission time. As a result, whether or not data are transmitted by one-hop or two-hop phases should be determined according to both signal strength and throughput. In this paper, we investigate the optimal relay location aiming to maximize system capacity. We consider two relay selection rules for determining whether two-hop transmission will be used: signal strength-oriented and throughput-oriented selection rules. We find that the signal strength-oriented two-hop transmission may yield even lower system capacity than the one-hop transmission. In the throughput-oriented scheme, the two-hop transmission can achieve higher system capacity than the one-hop transmission. By simulations, we determine the optimal relay location and show the coverage enhancement by the relaying network. Extensive simulations are performed to investigate the impacts of relay transmission power and the number of relay stations on system capacity and optimal relay location. The simulation results reveal important insights into designing a relaying network with high system capacity.
Distributed Channel Selection Principles for Femtocells with Two-tier Interference
(2010)
Lee, Chiao
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Huang, Jane-Hwa
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Wang, Li-Chun
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交大名義發表
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National Chiao Tung University
It goes without saying that the femtocells will be widely employed in the next generation wireless networks since the femtocells improve indoor capacity and coverage with low power and less cost. However, as the femtocells become popular, the femtocell users suffer from the complicated two-tier interference, including the macrocell-to-femtocell and femtocell-to-femtocell interference. Therefore, the femtocells pose a difficult challenge on managing the interference in a autonomous and distributed manner. In this paper, we investigate how to distributedly select the sub-channels for the OFDMA-based femtocell systems to reduce interference and to improve indoor capacity under a link reliability requirement. We develop the channel-gain oriented and interference-avoidance oriented distributed channel selection schemes. Simulation results show that the interference from the macrocell and other femtocells significantly degrades femtocell link reliability and capacity. However, by properly adjusting the number of used sub-channels, the developed channel selection schemes can improve capacity and ensure the link reliability.
High Capacity Femtocells with Directional Antennas
(2010)
Tsai, Ang-Hsun
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Huang, Jane-Hwa
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Wang, Li-Chun
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Hwang, Ruey-Bing
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傳播研究所
Femtocells are low-power, low-cost and user-deployed home base stations that can improve poor indoor coverage and enhance system capacity. However, as femtocells are deployed extensively, the two-tier interference will become serious, including the interference from macrocells and that from femtocells. Thanks to the low side lobe, the E-plane horns based reconfigurable antenna can be used to reduce the interference and enhance the capacity. In this paper, we investigate the effects of applying E-plane horns based reconfigurable directional antenna on link reliability and capacity of the orthogonal frequency-division multiple access (OFDMA) based femtocell systems. We compare our newly designed E-plane horns based reconfigurable antenna, and the sector antenna provided in the IEEE 802.16m, as well the omni-directional antenna. It is shown that E-plane horns based reconfigurable antenna system has higher femtocell capacity than the IEEE 802.16m sector antenna system due to the advantages of low side lobe and high main-lobe gain.
High-Capacity OFDMA Femtocells by Directional Antennas and Location Awareness
(2012-06-01)
Tsai, Ang-Hsun
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Wang, Li-Chun
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Huang, Jane-Hwa
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Hwang, Ruey-Bing
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電機工程學系
"In this paper, we propose a location-aware mechanism combined with a low-cost four-sector switched-beam directional antenna to enhance the spectrum efficiency of orthogonal frequency-division multiple access (OFDMA)-based femtocell systems. The considered location-awareness capability is specified in the current IEEE 802.16m WiMAX standard, but has not been applied to avoid the interference between indoor femtocells and outdoor macrocells. With the knowledge of the locations of outdoor users, the proposed four-sector switched-beam antenna in a femtocell can effectively avoid the interference among femtocells and macrocells by adjusting the number of OFDMA subcarriers used at each femtocell. Numerical results show that the proposed approach can significantly improve spectrum efficiency compared to the existing methods."
Network-assisted Device-decided Channel Selection and Power Control for Multi-pair Device-to-Device (D2D) Communications in Heterogeneous Networks
(2014)
Yang, Shu-Hao
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Wang, Li-Chun
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Huang, Jane-Hwa
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Tsai, Ang-Hsun
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電機工程學系
The device-to-device (D2D) communications can improve the spectrum efficiency with low power and effectively offload the traffic from the macro-eNB. However, the macro/femto/D2D heterogeneous networks face a complicated three-tier interference issue. The completely centralized resource management is not applicable in such three-tier heterogeneous networks. Therefore, we propose a network-assisted device-decided (NADD) scheme to jointly select the channels and adjust the transmission power for D2D devices. In the NADD method, the macro-eNB broadcasts resource allocation instruction to D2D devices. According to the resource allocation instruction and the device\'s communication quality, D2D devices autonomously and dynamically select the suitable channels and adjust the transmission power. Simulation results show that NADD scheme can significantly improve the total throughput and ensure the link reliability of macrocell users, comparing to both the fixed power scheme and the network-decided (ND) power control scheme.
Optimal relay location in multi-hop cellular systems
(2008)
Wang, Li-Chun
;
Su, Wen-Shan
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Huang, Jane-Hwa
;
Chen, Anderson
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Chang, Chung-Ju
Relay stations (RSs) are usually used to enhance the signal strength for the users close to the cell boundary. However, transmission through a relay station needs two transmission phases, i.e., one is from the base station to the relay station and the other is from relay station to mobile stations. Thus, relay may also decrease system capacity if two phase transmission time is considered. As a result, whether or not data are transmitted by one hop or two hop transmission should be determined based on both signal strength and throughput. In this paper, we investigate the optimal relay location aiming to maximize system capacity. We consider two relay selection rules for determining whether a two hop transmission is necessary: signal strength oriented and throughput oriented. We find that the signal strength oriented two hop transmission may yield even lower system capacity than the one hop transmission. Based on the throughput oriented rule, we find that the throughput in the two hop transmission can be higher than that in the one hop transmission at some locations. We also identify the optimal relay location that can achieve the highest system capacity.
Power fairness in a scalable ring-based wireless mesh network
(2007)
Huang, Jane-Hwa
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Wang, Li-Chun
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Chang, Chung-Ju
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電信工程研究所
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Institute of Communications Engineering
The wireless mesh network (WMN) is an essential low-power solution to support ubiquitous broadband services. However, mesh networks face the power unfairness and throughput bottleneck issues. Compared to the users far away from the gateway, the users near the gateway need to relay more traffic and consume more power. This paper proposes a scalable ring-based WMN that can ensure power fairness among users by adjusting the ring widths. On top of the ring-based WMN, frequency planning is suggested to overcome the throughput bottleneck issue for the inner-ring users near the gateway, thereby making the system more scalable to accommodate more users and facilitating coverage extension. We also investigate the overall tradeoffs of the ring-based WMN in terms of power fairness, capacity, and coverage. An analytical model is developed to evaluate the throughput and power consumption of the ring-based WMN using carrier sense multiple access (CSMA) MAC protocol in the unsaturated situation. Then, a mixed-integer nonlinear optimization problem aiming to maximize cell capacity and coverage subject to the constraint of power fairness is formulated. Applying this optimization approach, we obtain the optimal number of rings and the associated ring widths of the ring-based WMN.
Power Fairness in A Scalable Ring-based Wireless Mesh Network with Variable Ring-width Design
(2008)
Huang, Jane-Hwa
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Wang, Li-Chun
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Chang, Chung-Ju
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電信工程研究所
;
Institute of Communications Engineering
The wireless mesh network (WMN) is a promising solution to support wireless broadband applications. However, mesh networks face the power unfairness issue. Compared to the users far away from the gateway, the users near the gateway have to relay more traffic and consume more power. This paper proposes a scalable ring-based WMN that can ensure power fairness among users by adjusting its ring widths. On top of the ring-based cell structure, frequency planning is suggested to reduce the contending users, thereby making the system more scalable to accommodate more users. To investigate the overall tradeoffs among power fairness, capacity, and coverage, we develop an analytical model to evaluate the throughput and power consumption of the ring-based WMN using carrier sense multiple access (CSMA) medium access control (MAC) protocol in the unsaturated situation. Then, the optimization approach is applied to determine the best number of rings and the optimal ring widths, aiming to maximize cell capacity and coverage subject to the requirement of power fairness. Numerical results show that compared to the uniform ring-width strategy, the variable ring-width design criterion can improve cell capacity and coverage.
QoS provisioning in a scalable wireless mesh network for intelligent transportation systems
(2008-09-01)
Huang, Jane-Hwa
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Wang, Li-Chun
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Chang, Chung-Ju
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電信工程研究所
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Institute of Communications Engineering
The wireless mesh network (WMN) is an economical low-power solution to provide wireless broadband access in intelligent transportation systems (ITSs). This paper investigates how to deploy access points (APs) to improve throughput and quality-of-service (QoS), when the multihop communication is used to extend the coverage of wireless ITS network. Frequency planning is suggested to improve the capacity with QoS provisioning and to make the system more scalable. To investigate the overall tradeoffs among QoS, throughput, and coverage, we develop an analytical model to evaluate throughput, frame delay, and jitter for the considered ITS WMN using the carrier-sense multiple-access (CSMA) medium access control (MAC) protocol. Then, we apply an optimization approach to determine the optimal separation distances between APs with the delay requirement. To provide a guideline for network planning, we compare the uniform-spacing and increasing-spacing AP deployment strategies. The uniform-spacing strategy is to make all the APs with the same separation distance. In the increasing-spacing strategy, the separation distances between AN are increased from the central AP to the outer APs. Because of the shorter separation distance, the AP closer to the central AP can deliver higher traffic. It is shown that the increasing-spacing strategy outperforms the uniform-spacing strategy in terms and a profit function, considering the capacity and the total cost for deploying APs.
QoS provisioning in multihop outdoor public access networks with asymmetric user traffic
(2007)
Huang, Jane-Hwa
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Wang, Li-Chun
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Chang, Chung-Ju
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電信工程研究所
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Institute of Communications Engineering
With the goal to provide ubiquitous wireless In ternet access, large scale deployment of outdoor public access networks will continue at a rapid pace in the next years. In outdoor environment, connecting access points (APs) via cables is costly and requires a lot of cabling engineering work. Therefore, the multihop augmented network architecture has become an option of upsurging interest. This paper investigates how to deploy AN in an outdoor public access network to improve throughput and quality of service (QoS) while extending the coverage by multihop communications. Frequency planning is suggested to improve user throughput with QoS provisioning and to make the multihop network more scalable to facilitate cov erage extension. To investigate the overall tradeoffs among QoS, throughput, and coverage, we develop an analytical throughput and delay model for this multihop network using the carrier sense multiple access (CSMA) medium access control (MAC) protocol. This model also considers bidirectional asymmetric traffic for users operating in the unsaturated situation. Then, we apply an optimization approach to determine the optimal number of APs in a cluster and the best separation distances between APs, aiming to maximize the capacity and coverage of a cluster of AN subject to the delay requirement.
Throughput-coverage tradeoff in a scalable wireless mesh network
(2008-03-01)
Huang, Jane-Hwa
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Wang, Li-Chun
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Chang, Chung-Ju
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電信工程研究所
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Institute of Communications Engineering
The wireless mesh network (WMN) is an economical and low-power solution to support ubiquitous broadband services. However, mesh networks face scalability and throughput bottleneck issues as the coverage and the number of users increase. Specifically, if the coverage is extended by multiple hops, the repeatedly relayed traffic will exhaust the radio resource and degrade user throughput. Meanwhile, as the traffic increases because of more users, the throughput bottleneck will occur at the users close to the gateway. The contention collisions among these busy users near the gateway will further reduce user throughput. In this paper, a newly proposed scalable multi-channel ring-based WMN is employed. Under the ring-based cell structure, multi-channel frequency planning is used to reduce the number of contending users at each hop and overcome the throughput bottleneck issue, thereby making the system more scalable to accommodate more users and facilitate coverage extension. This paper mainly focuses on investigating the overall tradeoffs between user throughput and cell coverage in the ring-based WMN. An analytical throughput model is developed for the ring-based WMN using the carrier sense multiple access (CSMA) medium access control (MAC) protocol. In the analysis, we also develop a bulk-arrival semi-Markov queueing model to describe user behavior in a non-saturation condition. On top of the developed analytical model, a mixed-integer nonlinear optimization problem is formulated, aiming to maximize cell coverage and capacity. Applying this optimization approach, we can obtain the optimal number of rings and the associated ring widths of the ring-based WMN. (c) 2007 Elsevier Inc. All fights reserved.
Wireless mesh networks for intelligent transportation systems
(2006)
Huang, Jane-Hwa
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Wang, Li-Chun
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Chang, Chung-Ju
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電信工程研究所
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Institute of Communications Engineering
The wireless mesh network (WMN) is an economical solution for disseminating broadband wireless information in the intelligent transportation systems (ITS). This paper investigates the issue of deploying access points (APs) in an ITS wireless mesh network, where several adjacent APs form a cluster. Each AP in a cluster operates as a wireless relay to forward neighboring AP's traffic to the central access point connected to the Internet through cables. In general, access points are placed for maximizing cell coverage. However, larger coverage of an AP leads to lower throughput and longer delay in the access link as well as in the relay link. To find the optimal tradeoffs among delay, capacity, and coverage, we develop a physical (PHY)/medium access control (MAC) cross-layer analytical model to evaluate the throughput and delay of the considered ITS wireless mesh network. We consider the carrier sense multiple access (CSMA) protocol and the impact of hop distance on the data rate in the physical layer. Then, we apply the mixed-integer nonlinear programming (MINLP) optimization approach to determine the optimal number of APs in a cluster and the best cell radius of each AP, aiming at maximizing the capacity and coverage of a cluster of All's subject to the delay and fairness requirements.